Impact of Simulated Gastric Acid on Electrochemical Behavior, Surface Morphology, and Topography of 3D Printed cobalt chromium and Titanium Alloys for Dental Applications

Impact of Simulated Gastric Acid on Electrochemical Behavior, Surface Morphology, and Topography of 3D Printed cobalt chromium and Titanium Alloys for Dental Applications | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Impact of Simulated Gastric Acid on Electrochemical Behavior, Surface Morphology, and Topography of 3D Printed cobalt chromium and Titanium Alloys for Dental Applications Kawkb El-Tamimi, Dalia Bayoumi, Mohamed Ahmed, Mohamed Habba, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7735818/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 14 You are reading this latest preprint version Abstract Background This in vitro study aimed to ascertain how 3D printed cobalt chromium (Co-Cr) and titanium (Ti-6Al-4V) alloys react to simulated stomach acid with a pH of 1.2. Materials and methods A comparative in vitro investigation assessed 32 samples (n = 16/group) of 3D printed cobalt chromium (Co-Cr) and titanium (Ti-6Al-4V) alloys. Each alloy was separated into two subgroups (n = 8) based on the pH values of two distinct solutions: pH 1.2 and pH 6.7 pure water (control) solutions. The samples in the acidic pH subgroup were immersed in an acidic solution for two minutes, rinsed with distilled water, and stored in distilled water at 37°C. The procedure was repeated six times a day for nine days with a 24-hours interval between each cycle. The control group was maintained at 37°C in distilled water. The surface roughness of the samples was examined using scanning electron microscopy (SEM). Results In the Co–Cr alloy, immersion in an acidic solution resulted in a decrease in the percentage of all elements except oxygen (O), which increased to 6.37 ± 1.77%, with the change being statistically significant (P-value 0.05). Comparatively, the oxygen percentages for both alloys were significantly different under neutral and acidic conditions. SEM images indicated more oxide deposits on Co-Cr in acidic solution, which also showed a notable increase in surface roughness, while Ti-6Al-4V exhibited greater stability. The Abbott-Firestone analysis further confirmed that Co-Cr underwent more significant changes in peak formation and exploitation zones than Ti-6Al-4V in acidic environments. Conclusion The Ti-6Al-4V alloy demonstrated superior corrosion resistance and surface stability compared with the Co-Cr alloy when exposed to simulated gastric acid, making it a more suitable choice for dental applications in patients with gastroesophageal reflux disease. Salivary pH 3D printing Co-Cr and Ti-6Al-4V alloys Corrosion Morphology Topography Gastroesophageal reflux disease (GERD) Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Biocompatible metals have been used in dental applications such as tooth fillings, prosthetic restorations, and orthodontic appliances. ( 1 ) The oral cavity environment is characterized by a wide range of pH, bacterial load, and/or fluctuations in temperature, each of which has its own significance.( 2 ) Two important variables that influence the electrochemical activity of dental materials are the temperature and pH.( 3 ) Intraoral pH can be largely affected by dietary intake and medical conditions that can cause reduced salivary flow, which in turn may result in a reduced buffering capacity of saliva. Individuals who have had radiation to their head and neck region for cancer treatment, Sjögren syndrome or those on antimuscarinic agent medications have all been reported to have a decrease in salivary production and flow rate. Gastroesophageal reflux, commonly experienced as heartburn, is reported by 40%–85% women during pregnancy. ( 4 ) Furthermore, gastroesophageal reflux disease (GERD) is a common disease that is represented by this affection( 5 , 6 ) Approximately 10–20% of individuals in the West suffer from GERD.( 7 ) The pH of oral fluids changes to an acidic state when GERD is present( 7 ), and lower pH values in the oral environment affect the characteristics, properties, and behavior of dental materials, including dental metals. ( 8 , 9 )A salivary pH of 5.5 or lower, is thought to be important, as it can cause metal corrosion( 10 ) In dentistry, cobalt-chromium (Co-Cr) and titanium alloys are frequently used to fabricate dental restorations and orthodontic appliances. These alloys exhibit long-term corrosion resistance due to their passive oxide layer which protects them from further corrosion.( 11 ) This passive oxide layer is composed mainly of Cr 2 O 3 in cobalt chromium alloy and TiO 2 in titanium alloys. ( 12 ) Nowadays, problems facing metallic biomaterials include the demand for better bio-functionality and the need to lower relatively high manufacturing costs. ( 13 ) To resolve these problems, additive manufacturing (AM), in which selective laser melting (SLM) is a popular technique, has shown the fastest growth and innovation. ( 14 ) SLM produces metal substrates with almost no porosity by melting the alloy powder layer by layer. ( 15 ) Few studies have evaluated the impact of simulated gastric acid with a low pH on the surface roughness and corrosion of 3D printed Co-Cr and Ti-6Al-4V alloys for dental applications. This in vitro study aimed to investigate the effect of simulated gastric acid (pH 1.2) on the surface roughness, corrosion resistance, and surface topography of 3D printed Co-Cr and Ti-6Al-4V alloys used in dental applications. Specifically, this study compared the responses of these two alloys to acidic and neutral environments by examining their corrosion behavior, elemental composition changes, surface morphology alterations, and topographical characteristics. This study utilized various analytical techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), surface roughness profiling, and Abbott-Firestone analysis, to provide a comprehensive assessment of the behavior of the alloys. By simulating the conditions that might occur in patients with GERD, this study aimed to determine which alloy demonstrates superior corrosion resistance and surface stability, thereby informing material selection for dental applications in patients prone to acidic oral environments. 2. Materials and Methods This section describes the experimental procedures and techniques used in this study to evaluate the corrosion behavior and surface characteristics of 3D printed Co-Cr and Ti-6Al-4V alloys under simulated gastric acid conditions. This section details samples preparation, experimental design, treatment protocols, and analytical methods employed to assess the performance of the alloys in acidic and neutral environments. 2.1 Samples preparation Titanium specimens were fabricated utilizing titanium grade 5 Ti-6Al-4 V powder (TC4, BLT) and a 3D printer (A160 BLT). The manufacturer's specifications for the SLM are as follows: particle size from 15 to 45 µm, powder layer thickness of 25 µm, fiber laser power of 200 W, focus diameter approximately 75 µm, argon working atmosphere, no pre-heating, hatch distance of 0.105 mm, checkerboard hatch pattern, scan speed of 1250 mm/s, contour offset of 0.0825 mm, and power supply of 1.5 kW. Following the SLM processes, specimens were annealed at 820◦C (10◦C/min) for 4 h in a furnace under an argon shield and then were gradually cooled down to room temperature. For CoCr samples, the specimens were processed with approximately 10 to 30 µm of cobalt-chromium (Co-Cr-W dental alloy) alloy powders type 5 (Starbond Easy Powder Scheftner) using a 3D printer (Vulcantech VM120). The parameters of the laser melting machine used for the samples fabrication were a laser spot diameter of 0.08 − 0.1 mm, a scanning speed of 1100– 1200 mm/s, and a layer thickness of 0.02 mm. The specimens underwent heat treatment in a furnace using high-purity argon after the SLM procedures. At a ramp rate of 10°C per minute, the specimens were heated from room temperature to 1150°C and maintained there for six hours in the furnace. Specimens that had been heated were then gradually cooled to room temperature. Table 1 Brand names, manufacturers, and elemental compositions of Co-Cr and Ti-6Al-4V Alloys. Co-Cr Alloy Ti-6Al-4V Alloy Starbond simple Pulver 30, Scheftner dentistry, Germany TC4 BLT, China El. Wt. % El. Wt.% Co 61 Ti 90 Cr 27.5 Al 5.5–6.75 W 8.5 V 3.5–4.5 Si 1.6 Fe > 0.3 C, Fe, Mn > 1% C > 0.08 N > 0.05 H > 0.015 O 0.08 − 0.015 2.2 Experimental Design This in vitro study employed a comparative design to evaluate the corrosion behavior and surface characteristics of two dental alloys under simulated gastric acid conditions. The computation of the sample size was adopted from an earlier study on the corrosion of Ti-6Al-4V and Co–Cr alloys ( 16 ) and performed using G*Power version 3.1.9.2. ( 17 ) A total of 32 samples were prepared and divided into two main groups (n = 16 each) of Co-Cr and Ti-6Al-4V alloys. Each main group was further subdivided into two subgroups (n = 8 each) based on the immersion solution used: simulated gastric acid (pH 1.2, SG-B) and a control (distilled water, pH 6.7, SG-A). This 2 × 2 factorial design allowed both intra-alloy (acidic vs. neutral conditions) and inter-alloy (Co-Cr vs. Ti-6Al-4V) across different pH environments. The samples were fabricated using 3D printing technology, with Co-Cr samples produced using a Vulcan tech VM120 printer and Ti-6Al-4V samples created using a 160 BLT printer. All samples were finished using silicon carbide sheets with increasing grit sizes (180–1000) to ensure consistent surface preparation. 2.3 Treatment Protocols The dental Co-Cr and Ti-6Al-4V sample treatment protocols were designed to simulate the acidic conditions experienced in the oral cavities of patients with gastroesophageal reflux disease (GERD). A simulated gastric acid solution (pH 1.2) was prepared according to the British Pharmacopoeia by dissolving 2.0 g NaCl and 7.0 mL of concentrated HCl in 1 L distilled water. The experimental methodology was implemented based on previous studies( 18 , 19 ) with modifications to mimic the intermittent nature of acid exposure in the oral environment. Samples in the acidic group (SG-B) were subjected to a cyclic immersion protocol: they were immersed in the prepared acidic solution for 2 min, followed by thorough rinsing with distilled water to neutralize any residual acid. After each acid exposure, the samples were stored in distilled water at 37°C to simulate the oral cavity temperature. This immersion cycle was repeated six times daily for nine consecutive days, with a 24-hour interval between each day's set of cycles. This regimen was designed to represent the cumulative effects of multiple acid reflux episodes over an extended period. The control group (SG-A) was maintained in distilled water (pH 6.7) at 37°C for the same duration. 2.4 Electrochemical Experiments Electrochemical experiments were conducted using a GAMRY Reference 3000 potentiostat/galvanostat/ZRA analyzer. A classical three-electrode setup was employed, consisting of the sample under test as the working electrode (exposed surface area of 0.25 cm²), a saturated calomel electrode (SCE) as the reference electrode, and a Pt grid as the counter electrode. The electrochemical cell was filled with either simulated gastric acid solution (pH 1.2) or distilled water (pH 6.7) as the electrolyte and maintained at 37 ± 1°C using a thermostatic water bath. Prior to testing, the samples were cleaned with ethanol, rinsed with distilled water, dried with compressed air, and stabilized in the electrolyte for 1 h to achieve a steady open-circuit potential (OCP). Electrochemical impedance spectroscopy (EIS) measurements were performed by applying an AC excitation of 10 mV amplitude (peak-to-zero) over a frequency range of 100 kHz to 10 mHz at the OCP, with 10 data points collected per decade. The EIS data were analyzed using GAMRY Echem Analyst software to fit Nyquist plots to extract parameters such as the charge transfer resistance (Rct) and double-layer capacitance (Cdl). 2.5 Surface Morphology and Topography Analysis A scanning electron microscope (SEM) (Prisma E, Thermo Fisher Co.) equipped with an energy-dispersive X-ray spectroscopy (EDX) unit was used to examine the surface morphology and elemental composition of the samples. SEM imaging was performed at an accelerating voltage of 30 kV. The surface morphologies of the tested alloys in both acidic and neutral solutions were evaluated using oxide percentage analysis, in which the extent of oxide formation on the alloy surface was quantified. In addition, a roughness profile analysis was conducted to assess changes in the surface texture. The Abbott-Firestone approach was utilized to determine the surface topography of the corrosion-tested samples, providing insights into the distribution of peaks, voids, and bearing areas. This method involves generating cumulative height distribution curves and analyzing key parameters. 2.6 Statistical Analysis An independent t-test was used for intra- and intergroup comparisons between the two types of solutions (neutral and acidic) and between the two types of alloys (Co/Cr and Ti-6Al-4V). Differences were considered statistically significant (95% significance level). A p-value ≤ 0.001 was considered to be highly statistically significant (99% significance level). Shapiro–Wilk test was used to test the normality of the data. Data was analyzed using the statistical software SPSS version 25 (IBM Co. USA). 3. Results 3.1 Electrochemical behavior Table 2 presents the electrochemical behavior of the Co-Cr and Ti-6Al-4V alloys in acidic and neutral solutions. In the acidic solution, the Ti-6Al-4V alloy exhibited superior corrosion resistance compared to the Co-Cr alloy. The Ti-6Al-4V alloy demonstrated superior corrosion resistance compared to the Co-Cr alloy in both acidic and neutral environments. In the acidic solution, Ti-6Al-4V exhibited a lower corrosion current density (i corr ) of 20.7 µA/cm 2 compared to 37.2 µA/cm 2 for Co-Cr (Table 2 ), indicating a better resistance to corrosion. This trend was even more pronounced in the neutral solution, with Ti-6Al-4V exhibiting an icorr of 0.122 µA/cm 2 versus 1.6 µA/cm 2 for Co-Cr. The corrosion rate (CR) values were significantly lower for Ti-6Al-4V in both solutions, especially in the neutral solution, where it showed a CR of 0.158 mpy compared to 1.4 mpy for Co-Cr (Table 2 ). The results listed in Table 2 indicate that the Ti-6Al-4V alloy is more resistant to corrosion and surface alterations in both acidic and neutral solutions. Figures 1 and 2 present the electrochemical impedance spectroscopy (EIS) results for the Co-Cr and Ti-6Al-4V alloys, respectively, in both acidic (pH 1.2) and neutral (pH 6.7) solutions. It can be remarked that for the Co-Cr (Fig. 1 ) and Ti-6Al-4V alloys (Fig. 2 ), there is a stark contrast between their behavior in acidic and neutral solutions. In the acidic solution (Fig. 1 a), the Nyquist plot of Co-Cr shows a small, depressed semicircle with a diameter of approximately 350 Ohm.cm². This indicates a relatively low charge transfer resistance, suggesting that the Co-Cr alloy is more susceptible to corrosion in acidic solution. The depressed nature of the semicircle can be attributed to the formation of oxides under acidic conditions. In contrast, the Co-Cr alloy in the neutral solution (Fig. 1 b) exhibited a much larger semicircle with a diameter exceeding 800,000 Ohm.cm². This significant increase in the diameter of the semicircle indicates a substantially higher charge transfer resistance, implying an enhanced corrosion resistance in a neutral solution. The near-perfect semicircular shape suggests the formation of a more uniform and stable passive layer on the alloy surface under neutral conditions. Figure 2 illustrates the EIS results for the Ti-6Al-4V alloy. In the acidic solution (Fig. 2 a), the Nyquist plot revealed a semicircle with a diameter of approximately 420 Ohm.cm². Although this is larger than that of Co-Cr under acidic conditions, it still indicates some vulnerability to corrosion. The Ti-6Al-4V alloy in the neutral solution (Fig. 2 b) demonstrated greater corrosion resistance, with a semicircle diameter of approximately 886,000 Ohm.cm². This value was slightly higher than that of Co-Cr under neutral conditions, indicating superior corrosion resistance. The near-perfect semicircle shape implies a highly stable and uniform passive layer on the Ti-6Al-4V surface in a neutral solution. Comparing the two alloys, Ti-6Al-4V consistently showed better corrosion resistance than Co-Cr under both acidic and neutral conditions. This is evidenced by the larger semicircle diameters of both solutions. The difference was particularly pronounced in the acidic solution, where Ti-6Al-4V exhibited a significantly higher charge transfer resistance. Table 2 Corrosion results of Co-Cr and Ti-6Al-4V alloys after immersion test in acidic and neutral solutions Solution Sample i corr (µA/ cm 2 ) CR (mpy) 1.2 Ti-6Al-4V 20.70 18.34 Co-Cr 37.20 34.04 6.7 Ti-6Al-4V 0.122 0.158 Co-Cr 1.60 1.40 Table 3 shows the EDX results for the Co-Cr and Ti-6Al-4V alloys after immersion testing in acidic and neutral solutions. For the Co-Cr alloy , there was a statistically significant increase in oxygen content from 3.83% in the neutral solution to 6.37% in the acidic solution (p < 0.05). This substantial increase in oxygen suggests more extensive oxide formation on the Co-Cr surface under acidic conditions, which aligns with the lower corrosion resistance observed in the electrochemical behavior shown in Table 2 and Figs. 1 and 2 . In contrast, the Ti-6Al-4V alloy showed a smaller, non-significant increase in oxygen content from 0.69% to 2.26% when exposed to an acidic solution (p > 0.05). This relatively minor change in oxygen content corresponds to the superior corrosion resistance of the alloy, as detected in the electrochemical behavior of Ti-6Al-4V (Table 2 ). The stability of the Ti-6Al-4V surface composition, particularly the limited increase in oxygen, contributed to its better performance in acidic solutions. The intergroup comparison of the oxygen content between the two alloys was statistically significant in both neutral (p = 0.002) and acidic (p = 0.008) solutions. This significant difference in oxide formation correlates with the distinct corrosion behavior observed in the electrochemical tests. Therefore, previous results indicate that while both alloys experience some degree of oxidation in acidic solutions, the Ti-6Al-4V alloy maintains better surface stability and corrosion resistance. This is reflected in both its electrochemical behavior and the limited changes in its elemental composition, particularly the oxygen content, when exposed to simulated gastric acid. Table 3 Mean ± SD of the percentage of elements (wt%) in different solution pH values for both alloys. Alloy Element Neutral Acidic P-value* Co/Cr C 6.23 ± 1.81 6.21 ± 2.28 0.990 NS O 3.83 ± 2.24 6.37 ± 1.77 0.036 S Cr 22.31 ± 2.16 22 ± 1.92 0.778 NS Co 53.64 ± 3.49 51.51 ± 2.22 0.199 NS W 14.31 ± 1.37 13.6 ± 1.36 0.346 NS Ti-6Al-4V C 1.11 ± 0.84 0.34 ± 0.11 0.058 NS O 0.69 ± 0.42 2.26 ± 1.22 0.141 NS Al 5.34 ± 0.51 5.16 ± 0.45 0.484 NS Ti 93.06 ± 2.34 92.07 ± 2.16 0.428 NS P-Value * 0.002 S** 0.008 S * P-value comparison between the two solutions (Independent T- test). * P-value comparison of O between the two alloys in different solutions (Independent T- test). ** S = Statistically significant at P ≤ 0.05; NS = Non-significant P < 0.05. 3.2 Surface Morphology Figure 3 and 4 shows the (Fig. 3 ) SEM of the tested alloys and (Fig. 4 ) the formation of oxide layers on the Co-Cr and Ti-6Al-4V alloy surfaces when exposed to acidic and neutral solutions, respectively. It can be remarked that Figs. 3 and 4 shows more extensive oxide (black area; Fig. 3 and blue area; Fig. 4 ) deposits on the Co-Cr surfaces compared to Ti-6Al-4V, especially in acidic solutions. Furthermore, both alloys demonstrated higher resistance to oxide formation in a neutral solution than in an acidic solution. Oxide formation appears as distinct surface features that alter the topography of the alloy surfaces. For the Co-Cr alloy (Fig. 4 a,b), there was a dramatic increase in oxide formation when exposed to the acidic solution compared to that in the neutral solution. The percentage of deposited oxides increased from 29.46% in neutral solution to 58.91% in acidic solution. This substantial difference suggests that the acidic solution significantly accelerated the oxidation of the Co-Cr surface. A higher oxide percentage under acidic conditions indicates greater corrosion activity and potential degradation of the Co-Cr alloy. In contrast, the Ti-6Al-4V alloy (Fig. 4 c,d) showed much lower overall oxide formation in both solutions. The percentage of oxides increased from 1.57% in neutral solutions to 6.16% in acidic solutions. Although this represents a notable increase, the oxide percentage for Ti-6Al-4V was considerably lower than that observed for Co-Cr. This finding aligns with the well-known excellent corrosion resistance of Ti-6Al-4V, which is attributed to its ability to form a stable passive oxide layer. These observations of oxide formation (Fig. 4 ) align with the EDX results in Table 3 , which show a significant increase in the oxygen content for the Co-Cr alloy from 3.83% to 6.37% under acidic conditions, whereas the Ti alloy exhibited a smaller, non-significant increase from 0.69% to 2.26%, owing to the superior corrosion resistance of TofAl-4V compared to Co-Cr under acidic conditions. It can be concluded that the SEM images (Fig. 4 ) clearly show more extensive oxide deposits on the Co-Cr surfaces than on Ti-6Al-4V, especially in acidic solution. Oxide formations appear as distinct surface features that alter the topography of the alloy surfaces. Figure 5 and Table 4 show the surface roughness characteristics of the Co-Cr and Ti-6Al-4V alloys exposed to acidic and neutral solutions, respectively. The data revealed significant differences in the responses of the two alloys to different pH solutions, particularly in terms of surface roughness. For the Co-Cr alloy, there was a substantial increase in surface roughness when exposed to the acidic solution compared with the neutral solution. The mean Ra value increased from 16.09 ± 1.27 in the neutral solution to 25.30 ± 1.83 in the acidic solution, as shown in Fig. 5 . This difference was statistically significant (p < 0.001; Table 4 ), indicating that the acidic solution had a pronounced effect on the surface topography of the Co-Cr alloy specimens. The increased roughness suggests that the acidic solution likely caused more aggressive corrosion or etching of the Co-Cr surface. In contrast, the Ti-6Al-4V alloy demonstrated much greater stability in terms of surface roughness under both pH conditions. The mean Ra value increased only slightly from 11.07 ± 0.82 in the neutral solution to 13.60 ± 1.42 in the acidic solution (Table 4 ). This difference was not statistically significant (p = 0.838), suggesting that the Ti-6Al-4V alloy surface was more resistant to changes induced by the acidic solution. This stability can be attributed to the well-known ability of Ti-6Al-4V to form a protective oxide layer, which effectively shields the bulk material from significant acid-induced surface alterations. Comparing the two alloys, it is evident that the Co-Cr alloy consistently exhibited a higher surface roughness than the Ti-6Al-4V alloy under both neutral and acidic conditions. The difference in Ra between the two alloys was highly statistically significant (p < 0.001) in both pH solutions. This suggests that even under neutral conditions, the Co-Cr alloy has an inherently rougher surface than the Ti-6Al-4V alloy, a characteristic that becomes even more pronounced under acidic conditions. These observations of oxide formation align with the EDX results in Table 2 , which showed a significant increase in oxygen content for the Co-Cr alloy from 3.83% to 6.37% under acidic conditions, while the Ti alloy exhibited a smaller, non-significant increase from 0.69% to 2.26%, confirming the superior corrosion resistance of Ti-6Al-4V compared to Co-Cr in simulated gastric acid environments. It can be concluded that the observed increase in the surface roughness of the Co-Cr alloy under acidic conditions may raise concerns regarding its long-term stability and potential for increased bacterial adhesion or food debris accumulation in acidic solutions. Table 4 Mean ± SD of Ra in different solutions pH (acidic and neutral solutions) for both alloys. Alloy Acidic Neutral P-value* Co/Cr 25.30 ± 1.83 16.09 ± 1.27 < 0.001 HS Ti-6Al-4V 13.60 ± 1.42 11.07 ± 0.82 0.838 NS P-value** < 0.001 HS < 0.001 HS -* P-value comparison between the two solutions (Independent T- test). * P-value comparison of Ra between the two alloys in different solutions (Independent T- test). HS = Highly significant at P ≤ 0.001; NS = Non-significant P < 0.05. 3.3 Surface Topography Surface topography using Abbott–Firestone analysis is a valuable technique for characterizing surface topography in materials science and engineering. The Abbott-Firestone curve provides a cumulative probability distribution of the surface heights, offering a comprehensive view of the topographical features of the surface. The Abbott-Firestone technique is particularly useful for evaluating the performance of surfaces in contact situations, such as those encountered in dental implants or prosthetics. The Abbott-Firestone curves show the distribution of peaks, voids, and exploitation surfaces on the alloy samples, which are critical factors in determining the wear resistance, friction characteristics, and potential for material degradation. In the context of this study, the Abbott-Firestone analysis allowed for a more nuanced understanding of how exposure to acidic and neutral solutions affects the surface topography of Co-Cr and Ti-6Al-4V alloys. This information is vital because changes in surface characteristics can significantly affect the performance and longevity of dental materials in oral solutions. For instance, an increase in the exploitation area ratio can potentially improve the wear resistance of dental materials during chewing. In addition, an increase in the void area could potentially lead to an increased probability of bacterial adhesion or food debris accumulation. The Abbott-Firestone approach complements the observations obtained through SEM imaging and elemental analysis, providing a more comprehensive analysis of the corrosion resistance and surface stability, bacterial adhesion, and food debris accumulaTi-6Al-4V on these alloys. Figures 6 – 9 show the surface topography analysis using the Abbott–Firestone approach for the Co-Cr (Figs. 6 and 7 ) and Ti-6Al-4V (Figs. 8 and 9 ) surfaces after immersion tests in acidic and neutral solutions. For the Co-Cr alloy (Figs. 6 and 7 ), the neutral solution led to a significant improvement in the surface topography compared with the acidic solution. The percentage of peaks decreased from 12% in the neutral solution to 8% in the acidic solution, indicating a rougher surface. Additionally, the void percentage was less than half, ranging from 5% to 2%. The exploitation zone, which represents the primary load-bearing area, increased from 83% to 90%. These changes collectively resulted in a higher total roughness (Rt) of 145.84 µm in the acidic solution compared to 106.61 µm in the neutral solution. Ti-6Al-4V alloys exhibited different behaviors under neutral conditions, as shown in Figs. 8 and 9 . Unlike Co-Cr, Ti-6Al-4V showed a slight increase in the peak percentage from 10% under neutral conditions to 11% under neutral conditions. However, the void percentage decreased significantly from 6% to 1%. The exploitation zone increased marginally from 84% to 88% of the total area. The total roughness (Rt) decreased from 116.41 µm under acidic conditions to 96.3 µm under neutral conditions. Peak formation analysis : For the Co-Cr alloy, the percentage of peaks decreased significantly from 12% in acidic solution to 8% in neutral solution. This represents a 33% decrease in peak formation when exposed to an acidic solution. For the Ti-6Al-4V alloy, the percentage of peaks increased slightly from 10% in the acidic solution to 11% in the neutral solution. The substantial reduction in the peak percentage suggests that the Co-Cr alloy experiences considerable surface roughening under acidic conditions, potentially leading to a more irregular surface topography. The minor 1% change in peak formation in the Ti-6Al-4V alloy between acidic and neutral solutions indicates that the Ti-6Al-4V alloy maintains a more stable surface topography even when exposed to acidic conditions, showing a lower tendency for surface roughening. Comparing the two alloys, it is evident that the Co-Cr alloy experienced a more dramatic change in the peak formation when exposed to acidic solutions. The 50% increase in Co-Cr compared to the 9% decrease in Ti-6Al-4V suggests that Co-Cr may be more susceptible to surface alterations under acidic conditions. This could potentially lead to increased surface roughness and irregularities over time. These results were confirmed by morphological analysis (Section 3.2 ). Exploitation zone analysis : For the Co-Cr alloy, the exploitation zone increased significantly from 83% in the acidic solution to 90% in the neutral solution. This represents a 7% improvement in the primary load bearing area under acidic conditions. However, the Ti-6Al-4V alloy demonstrated greater stability in the exploitation zone. The exploitation zone increased marginally, from 84% in the acidic solution to 88% in the neutral solution, representing an improvement of only 4%. This smaller change, compared to that of the Co-Cr alloy, indicates that the Ti-6Al-4V alloy maintained a more consistent surface topography and load-bearing area, even when exposed to acidic conditions. In addition, both alloys maintained a higher exploitation zone of over 88% in a neutral solution, suggesting potentially better wear resistance, load-bearing capacity during chewing food processing, and a long lifetime under neutral conditions. Void analysis : For the Co-Cr alloy, the void percentage decreased from 5% under neutral conditions to 2% under acidic conditions. This represents a 60% decrease in the void percentage when exposed to a neutral solution. In contrast, the Ti-6Al-4V alloy exhibited a greater reduction in the void percentage. Under acidic conditions, the void percentage was 6%, which decreased to 1% when exposed to a neutral solution. This represents an 83% decrease in the void percentage, which is significantly higher than the change observed in the Co-Cr alloy. It can be concluded that the Ti-6Al-4V and Co-Cr alloys exhibited a more substantial decrease in the void percentage, which could potentially decrease the surface defects and corrosion pits and increase the resistance to bacterial adhesion and food debris accumulation, particularly in Ti-6Al-4V alloys. 4. Discussion This comprehensive study on the impact of simulated gastric acid on 3D printed Co-Cr and Ti-6Al-4V dental alloys revealed a complex interplay between surface characteristics, corrosion resistance, and topographical changes. The results consistently demonstrated the higher performance of Ti-6Al-4V over Co-Cr in acidic environments, mimicking the conditions experienced by patients with gastroesophageal reflux disease (GERD). Electrochemical behavior analysis showed that Ti-6Al-4V exhibited a lower corrosion current density (icorr) and corrosion rate (CR) than Co-Cr in both acidic and neutral solutions (Table 2 ). The higher corrosion resistance of Ti-6Al-4V can be attributed to its ability to form a stable, adherent, and self-healing passive oxide layer primarily composed of TiO 2 . This protective layer is highly effective in resisting corrosion in various environments, including acidic and neutral solutions.( 20 , 21 ) The presence of Al and V in the alloy further enhanced the stability and protective nature of the oxide layer, contributing to its improved corrosion resistance. Furthermore, the electrochemical nobility of Ti is higher than those of Co and Cr, which inherently makes Ti-6Al-4V less susceptible to corrosion in different pH environments.( 22 , 23 ) This property, combined with the robust passive oxide layer, results in a lower corrosion current density (icorr) and corrosion rate (CR) for Ti-6Al-4V compared to Co-Cr alloys. Although Co-Cr alloys also form a protective oxide layer, primarily composed of Cr 2 O 3 , it may not be as stable or protective as the oxide layer formed on Ti-6Al-4V, especially in more aggressive environments.( 24 ) This difference in the oxide layer stability and protective properties explains the observed lower icorr and CR values for Ti-6Al-4V in both acidic and neutral solutions. The lower icorr and CR values for Ti-6Al-4V indicate that it undergoes less electrochemical dissolution than Co-Cr when exposed to both acidic and neutral environments. This is particularly significant in dental applications, where materials are frequently exposed to varying pH levels in the oral cavity. The superior corrosion resistance of Ti-6Al-4V is further supported by the EDX results (Table 3 ), which show a smaller increase in the oxygen content for Ti-6Al-4V (from 0.69% to 2.26%) than for Co-Cr (from 3.83% to 6.37%) when exposed to acidic conditions. The significant increase in oxygen content for Co-Cr indicates more extensive oxide formation, which is visually confirmed by SEM analysis showing larger oxide deposits on Co-Cr surfaces, particularly in acidic solutions. Increased thickness of the oxide layer may be associated with a higher degree of metal ion release. However, increased ion release of Co–Cr alloy in acidic conditions doesn’t exceed the limits of cell viability according to standards.( 25 ) Surface roughness measurements were consistent with these findings, demonstrating a substantial increase in Ra values for Co-Cr from 16.09 in neutral solution to 25.30 in acidic solution, while Ti-6Al-4V maintained relatively stable Ra values across both conditions (Fig. 5 and Table 4 ). The surface roughness of Ti-6Al-4V correlates with its superior corrosion resistance, suggesting better long-term performance in acidic oral environments. The Abbott-Firestone analysis results for the Ti-6Al-4V and Co-Cr alloys provided valuable insights into their topographical changes under different pH conditions, which have significant implications for dental applications. The more dramatic changes observed in the Co-Cr peak formation and exploitation zone under acidic conditions compared to Ti-6Al-4V (Figs. 6 – 9 ), can be attributed to the different corrosion behaviors of these alloys. Ti-6Al-4V typically forms a more stable and protective TiO 2 layer that is resistant to breakdown, even in acidic environments. This protective layer helps to maintain the surface topography of Ti-6Al-4V more effectively than that of Co-Cr alloys. The reduction in the void percentage observed for both alloys in neutral solutions is a positive finding for their dental applications. This change in surface topography can lead to potential resistance to bacterial adhesion and accumulation of food debris.( 26 ) A surface with fewer voids provides less space for bacteria to adhere and colonize, which can significantly impede biofilm formation. Additionally, a smoother surface with fewer voids is easier to clean, reducing the likelihood of food debris accumulation and helping to maintain better oral hygiene in patients with dental implants or prostheses.( 26 , 27 ) The importance of these topographical changes extends beyond the bacterial adhesion and debris accumulation. The reduction in surface voids can also contribute to improved corrosion resistance by minimizing the areas where corrosive agents can accumulate and initiate localized corrosion.( 26 , 28 ) This is particularly relevant in the dynamic oral environment, where pH fluctuations and various chemical challenges are common. It can be concluded that the Abbott-Firestone analysis results suggest that both Ti-6Al-4V and Co-Cr alloys may offer improved resistance to bacterial adhesion and food debris accumulation under neutral conditions, which is highly beneficial for dental applications in patients with GERD. Moreover, the stability of Ti-6Al-4V in acidic environments further substantiates its suitability for patients with GERD. 5. Conclusion Based on the comprehensive analysis presented in this study, the following conclusions can be drawn; Ti-6Al-4V exhibited superior corrosion resistance compared to Co-Cr in both acidic and neutral solutions, with lower corrosion current density (icorr) and corrosion rate (CR) values. In an acidic solution, Ti-6Al-4V showed an icorr of 20.70 µA/cm 2 compared to 37.20 µA/cm 2 for Co-Cr, indicating a better resistance to corrosion.The increase in oxygen content for Ti-6Al-4V (from 0.69% to 2.26%) was smaller than that for Co-Cr (from 3.83% to 6.37%) when exposed to acidic conditions, suggesting less oxide formation.The surface roughness (Ra) of Co-Cr increased significantly from 16.09 ± 1.27 in neutral solution to 25.30 ± 1.83 in acidic solution, while Ti-6Al-4V maintained more stable Ra values of 11.07 ± 0.82 to 13.60 ± 1.42.Abbott-Firestone analysis showed that Co-Cr experienced a more dramatic change in peak formation from 12% to 8% and exploitation zone from 83% to 90% under acidic conditions compared to Ti-6Al-4V.Both alloys exhibited a decrease in the void percentage in neutral solutions, with Ti-6Al-4V showing a greater reduction from 6% to 1% compared to Co-Cr, which decreased from 5% to 2%. Ti-6Al-4V demonstrated greater stability in surface topography across different pH conditions, making it more suitable for dental applications in patients with GERD. Declarations Acknowledgements Not applicable. Author contributions Kawkb M. El-Tamimi, Dalia A. Bayoumi , Sherif E. Zahra and Mohammed E. El-Sayed were contributed to the study’s conception and design. Kawkb M. El-Tamimi and Dalia A. Bayoumi performed material preparation, data collection, and analysis. Kawkb M. El-Tamimi and Mohamed I. A. Habba wrote the original draft of the manuscript. Mohamed M. Z. Ahmed reviewed the manuscript. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Funding The authors received no specific funding for this work. Data availability The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request. Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare no competing interests. Author details 1 Department of Removable Prosthodontics, Faculty of Dentistry, Suez Canal University, Ismailia 41522, Egypt. 2 Department of Dental Biomaterials, Faculty of Dentistry, Suez Canal University, Ismailia 41522, Egypt. 3 Mechanical Engineering Department, College of Engineering at Al Kharj, Prince Sattam Bin Abdulaziz University, Al Kharj 11942, Saudi Arabia. 4 Department of Metallurgical and Materials Engineering, Faculty of Petroleum and Mining Engineering, Suez University, Suez 43512, Egypt. 5 Mechanical Department, Faculty of Technology and Education, Suez University, Suez 43518, Egypt. 6 Department of Orthodontics, Faculty of Dentistry, Suez Canal University, Ismailia 41522, Egypt. References Marin E. History of dental biomaterials: biocompatibility, durability and still open challenges. Vol. 11, Heritage Science. Springer Science and Business Media Deutschland GmbH; 2023. Stašková A, Nemcová R, Lauko S, Jenča A. Oral Microbiota from the Stomatology Perspective. In: Bacterial Biofilms. IntechOpen; 2020. Eliaz N. Corrosion of Metallic Biomaterials: A Review. Materials. 2019 Jan 28;12(3):407. Ali RAR, Egan LJ. Gastroesophageal reflux disease in pregnancy. Best Pract Res Clin Gastroenterol. 2007;21(5):793–806. Akinola MA, Oyedele TA, Akande KO, Oluyemi OY, Salami OF, Adesina AM, et al. Gastroesophageal reflux disease: prevalence and Extraesophageal manifestations among undergraduate students in South West Nigeria. BMC Gastroenterol. 2020 Dec 26;20(1):160. Lin S, Li H, Fang X. Esophageal Motor Dysfunctions in Gastroesophageal Reflux Disease and Therapeutic Perspectives. J Neurogastroenterol Motil. 2019 Oct 30;25(4):499–507. Antunes C, Aleem A, Curtis SA. Gastroesophageal Reflux Disease. 2024. Kawar N, Park SG, Schwartz JL, Callahan N, Obrez A, Yang B, et al. Salivary microbiome with gastroesophageal reflux disease and treatment. Sci Rep. 2021 Jan 8;11(1):188. Armencia1 AO, Cristina TC, Lese A, Feier R, Scutariu MM, Balcos C. THE STUDY OF ROUGHNESS AND RESISTANCE TO CORROSION OF DENTAL ALLOYS IN THE ORAL ENVIRONMENT. Vol. 12, Romanian Journal of Oral Rehabilitation. Dawes C. What is the critical pH and why does a tooth dissolve in acid? J Can Dent Assoc. 2003 Dec;69(11):722–4. Adya N, Alam M, Ravindranath T, Mubeen A, Saluja B. Corrosion in titanium dental implants: literature review. The Journal of Indian Prosthodontic Society. 2005;5(3):126. M.Kaczmarek WWWK. chemical composition of passive layer formed on metallic biomaterials . Materials Science, Chemistry Archives of materials Science and engineering . 2007 May;28(5). Wilson J. Fundamental Biomaterials: Metals. Preetha Balakrishnan, Sreekala M S, Sabu Thomas, editors. Elsevier; 2018. 1–33 p. Chen L, He Y, Yang Y, Niu S, Ren H. The research status and development trend of additive manufacturing technology. The International Journal of Advanced Manufacturing Technology. 2017 Apr 24;89(9–12):3651–60. Ren XW, Zeng L, Wei ZM, Xin XZ, Wei B. Effects of multiple firings on metal-ceramic bond strength of Co-Cr alloy fabricated by selective laser melting. J Prosthet Dent. 2016 Jan;115(1):109–14. Şahin M, Ünalan F, Mutlu İ. Corrosion, ion release, and surface hardness of Ti-6Al-4V and cobalt-chromium alloys produced by CAD-CAM milling and laser sintering. J Prosthet Dent. 2022 Sep;128(3):529.e1-529.e10. Faul F, Erdfelder E, Lang AG, Buchner A. G*Power 3: A flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods. 2007 May;39(2):175–91. Kulkarni A, Rothrock J, Thompson J. Impact of Gastric Acid Induced Surface Changes on Mechanical Behavior and Optical Characteristics of Dental Ceramics. Journal of Prosthodontics. 2020 Mar 1;29(3):207–18. Abbate-Daga G, Pierò A, Gramaglia C, Fassino S. Factors related to severity of vomiting behaviors in bulimia nervosa. Psychiatry Res. 2005 Mar 30;134(1):75–84. Socorro-Perdomo PP, Florido-Suárez NR, Mirza-Rosca JC, Saceleanu MV. EIS Characterization of Ti Alloys in Relation to Alloying Additions of Ta. Materials. 2022 Jan 8;15(2):476. Wong KK, Hsu HC, Wu SC, Ho WF. A Review: Design from Beta Titanium Alloys to Medium-Entropy Alloys for Biomedical Applications. Materials. 2023 Nov 5;16(21):7046. Manaka T, Tsutsumi Y, Takada Y, Chen P, Ashida M, Doi K, et al. Galvanic Corrosion among Ti–6Al–4V ELI Alloy, Co–Cr–Mo Alloy, 316L-Type Stainless Steel, and Zr–1Mo Alloy for Orthopedic Implants. Mater Trans. 2023 Jan 1;64(1):MT-MLA2022001. Ghisheer MMM, Esen I, Ahlatci H, Akın B. Investigation of Microstructure, Mechanics, and Corrosion Properties of Ti6Al4V Alloy in Different Solutions. Coatings. 2024 Feb 25;14(3):277. Swaminathan V, Zeng H, Lawrynowicz D, Zhang Z, Gilbert JL. Electrochemical investigation of chromium oxide‐coated Ti‐6Al‐4V and Co‐Cr‐Mo alloy substrates. J Biomed Mater Res B Appl Biomater. 2011 Aug 6;98B(2):369–78. Kassapidou M, Hjalmarsson L, Johansson CB, Hammarström Johansson P, Morisbak E, Wennerberg A, et al. Cobalt–chromium alloys fabricated with four different techniques: Ion release, toxicity of released elements and surface roughness. Dental Materials. 2020 Nov;36(11):e352–63. Lorenzetti M, Dogša I, Stošicki T, Stopar D, Kalin M, Kobe S, et al. The Influence of Surface Modification on Bacterial Adhesion to Titanium-Based Substrates. ACS Appl Mater Interfaces. 2015 Jan 28;7(3):1644–51. Preedy E, Perni S, Nipiĉ D, Bohinc K, Prokopovich P. Surface Roughness Mediated Adhesion Forces between Borosilicate Glass and Gram-Positive Bacteria. Langmuir. 2014 Aug 12;30(31):9466–76. Velic A, Mathew A, Hines P, Yarlagadda P. Control of bacterial adhesion and distribution on Ti-6Al-4V surfaces by fracture topography. 2019 Sep. 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1","display":"","copyAsset":false,"role":"figure","size":99152,"visible":true,"origin":"","legend":"\u003cp\u003eNyquist plot (experimental and fitted data) of the Co-Cr alloy after the immersion test in (a) acidic and (b) neutral solutions.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7735818/v1/9c6b92e4469c7eea0d49bf19.png"},{"id":96051045,"identity":"cd0db01d-377f-4461-a68a-16cf8c67a45c","added_by":"auto","created_at":"2025-11-17 06:39:34","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":119480,"visible":true,"origin":"","legend":"\u003cp\u003eNyquist plots (experimental and fitted data) of the Ti-6Al-4V alloy after immersion in (a) acidic and (b) neutral 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4","display":"","copyAsset":false,"role":"figure","size":394489,"visible":true,"origin":"","legend":"\u003cp\u003eOxides deposited on the surfaces of Co-Cr and Ti-6Al-4V after immersion tests in (a, c) acidic and (b, d) neutral solutions.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7735818/v1/9c28268b8fd55bc1f4265d16.png"},{"id":96051212,"identity":"63e23c45-630a-4bce-92bc-f7d3d876f251","added_by":"auto","created_at":"2025-11-17 06:39:57","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":126680,"visible":true,"origin":"","legend":"\u003cp\u003eSurface roughness profile and Ra of Co-Cr and Ti-6Al-4V alloys after immersion test in acidic and neutral solutions.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7735818/v1/273483c686d3cc604d65684b.png"},{"id":96050968,"identity":"fe2db5d8-e427-404a-85a5-e369fec39c02","added_by":"auto","created_at":"2025-11-17 06:39:28","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":113557,"visible":true,"origin":"","legend":"\u003cp\u003eSurface topography of Co-Cr surface after immersion test in acidic solution.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7735818/v1/ea3190f38deb7cc7781ed10c.png"},{"id":96051084,"identity":"a1194563-149e-4c6e-966b-45a2071161a3","added_by":"auto","created_at":"2025-11-17 06:39:41","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":119870,"visible":true,"origin":"","legend":"\u003cp\u003eSurface topography of Co-Cr surface after immersion test in a neutral solution.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7735818/v1/8e5430c75dcf5ef717d565db.png"},{"id":96051166,"identity":"7f976365-5eb6-4fef-93df-63925ff043d5","added_by":"auto","created_at":"2025-11-17 06:39:48","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":122823,"visible":true,"origin":"","legend":"\u003cp\u003eSurface topography of Ti-6Al-4V surface after immersion test in acidic solution.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7735818/v1/308a6125fbac5476e266d5ab.png"},{"id":96051169,"identity":"bf707e49-1977-4e97-8852-4afcf450cf1e","added_by":"auto","created_at":"2025-11-17 06:39:49","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":117388,"visible":true,"origin":"","legend":"\u003cp\u003eSurface topography of Ti-6Al-4V surface after immersion test in a neutral solution.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7735818/v1/5cdf3a99e877bba9ed2c6c94.png"},{"id":96051290,"identity":"5d813c23-cd8e-43bd-a5ad-49b0d4e998ad","added_by":"auto","created_at":"2025-11-17 06:40:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2395152,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7735818/v1/22d77b8a-d486-476c-82d6-d4b15d62f6fa.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Impact of Simulated Gastric Acid on Electrochemical Behavior, Surface Morphology, and Topography of 3D Printed cobalt chromium and Titanium Alloys for Dental Applications","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eBiocompatible metals have been used in dental applications such as tooth fillings, prosthetic restorations, and orthodontic appliances. (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) The oral cavity environment is characterized by a wide range of pH, bacterial load, and/or fluctuations in temperature, each of which has its own significance.(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) Two important variables that influence the electrochemical activity of dental materials are the temperature and pH.(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) Intraoral pH can be largely affected by dietary intake and medical conditions that can cause reduced salivary flow, which in turn may result in a reduced buffering capacity of saliva. Individuals who have had radiation to their head and neck region for cancer treatment, Sj\u0026ouml;gren syndrome or those on antimuscarinic agent medications have all been reported to have a decrease in salivary production and flow rate. Gastroesophageal reflux, commonly experienced as heartburn, is reported by 40%\u0026ndash;85% women during pregnancy. (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eFurthermore, gastroesophageal reflux disease (GERD) is a common disease that is represented by this affection(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e) Approximately 10\u0026ndash;20% of individuals in the West suffer from GERD.(\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e) The pH of oral fluids changes to an acidic state when GERD is present(\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e), and lower pH values in the oral environment affect the characteristics, properties, and behavior of dental materials, including dental metals. (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e)A salivary pH of 5.5 or lower, is thought to be important, as it can cause metal corrosion(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e) In dentistry, cobalt-chromium (Co-Cr) and titanium alloys are frequently used to fabricate dental restorations and orthodontic appliances. These alloys exhibit long-term corrosion resistance due to their passive oxide layer which protects them from further corrosion.(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e) This passive oxide layer is composed mainly of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in cobalt chromium alloy and TiO\u003csub\u003e2\u003c/sub\u003e in titanium alloys. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eNowadays, problems facing metallic biomaterials include the demand for better bio-functionality and the need to lower relatively high manufacturing costs. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e) To resolve these problems, additive manufacturing (AM), in which selective laser melting (SLM) is a popular technique, has shown the fastest growth and innovation. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e) SLM produces metal substrates with almost no porosity by melting the alloy powder layer by layer. (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eFew studies have evaluated the impact of simulated gastric acid with a low pH on the surface roughness and corrosion of 3D printed Co-Cr and Ti-6Al-4V alloys for dental applications.\u003c/p\u003e\u003cp\u003eThis in vitro study aimed to investigate the effect of simulated gastric acid (pH 1.2) on the surface roughness, corrosion resistance, and surface topography of 3D printed Co-Cr and Ti-6Al-4V alloys used in dental applications. Specifically, this study compared the responses of these two alloys to acidic and neutral environments by examining their corrosion behavior, elemental composition changes, surface morphology alterations, and topographical characteristics. This study utilized various analytical techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), surface roughness profiling, and Abbott-Firestone analysis, to provide a comprehensive assessment of the behavior of the alloys. By simulating the conditions that might occur in patients with GERD, this study aimed to determine which alloy demonstrates superior corrosion resistance and surface stability, thereby informing material selection for dental applications in patients prone to acidic oral environments.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003eThis section describes the experimental procedures and techniques used in this study to evaluate the corrosion behavior and surface characteristics of 3D printed Co-Cr and Ti-6Al-4V alloys under simulated gastric acid conditions. This section details samples preparation, experimental design, treatment protocols, and analytical methods employed to assess the performance of the alloys in acidic and neutral environments.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Samples preparation\u003c/h2\u003e\u003cp\u003eTitanium specimens were fabricated utilizing titanium grade 5 Ti-6Al-4 V powder (TC4, BLT) and a 3D printer (A160 BLT). The manufacturer's specifications for the SLM are as follows: particle size from 15 to 45 \u0026micro;m, powder layer thickness of 25 \u0026micro;m, fiber laser power of 200 W, focus diameter approximately 75 \u0026micro;m, argon working atmosphere, no pre-heating, hatch distance of 0.105 mm, checkerboard hatch pattern, scan speed of 1250 mm/s, contour offset of 0.0825 mm, and power supply of 1.5 kW. Following the SLM processes, specimens were annealed at 820◦C (10◦C/min) for 4 h in a furnace under an argon shield and then were gradually cooled down to room temperature. For CoCr samples, the specimens were processed with\u003c/p\u003e\u003cp\u003eapproximately 10 to 30 \u0026micro;m of cobalt-chromium (Co-Cr-W dental alloy) alloy powders type 5 (Starbond Easy Powder Scheftner) using a 3D printer (Vulcantech VM120). The parameters of the laser melting machine used for the samples fabrication were a laser spot diameter of 0.08\u0026thinsp;\u0026minus;\u0026thinsp;0.1 mm, a scanning speed of 1100\u0026ndash; 1200 mm/s, and a layer thickness of 0.02 mm. The specimens underwent heat treatment in a furnace using high-purity argon after the SLM procedures. At a ramp rate of 10\u0026deg;C per minute, the specimens were heated from room temperature to 1150\u0026deg;C and maintained there for six hours in the furnace. Specimens that had been heated were then gradually cooled to room temperature.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eBrand names, manufacturers, and elemental compositions of Co-Cr and Ti-6Al-4V Alloys.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eCo-Cr Alloy\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eTi-6Al-4V Alloy\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eStarbond simple Pulver 30,\u003c/p\u003e\u003cp\u003eScheftner dentistry, Germany\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eTC4\u003c/p\u003e\u003cp\u003eBLT, China\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eEl.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eWt. %\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eEl.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eWt.%\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCo\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eTi\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e90\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCr\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e27.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eAl\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.5\u0026ndash;6.75\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eW\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eV\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.5\u0026ndash;4.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSi\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eFe\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;0.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eC, Fe, Mn\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;1%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eN\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eH\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;0.015\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eO\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.08\u0026thinsp;\u0026minus;\u0026thinsp;0.015\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Experimental Design\u003c/h2\u003e\u003cp\u003eThis in vitro study employed a comparative design to evaluate the corrosion behavior and surface characteristics of two dental alloys under simulated gastric acid conditions. The computation of the sample size was adopted from an earlier study on the corrosion of Ti-6Al-4V and Co\u0026ndash;Cr alloys (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e) and performed using G*Power version 3.1.9.2. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e) A total of 32 samples were prepared and divided into two main groups (n\u0026thinsp;=\u0026thinsp;16 each) of Co-Cr and Ti-6Al-4V alloys. Each main group was further subdivided into two subgroups (n\u0026thinsp;=\u0026thinsp;8 each) based on the immersion solution used: simulated gastric acid (pH 1.2, SG-B) and a control (distilled water, pH 6.7, SG-A). This 2 \u0026times; 2 factorial design allowed both intra-alloy (acidic vs. neutral conditions) and inter-alloy (Co-Cr vs. Ti-6Al-4V) across different pH environments. The samples were fabricated using 3D printing technology, with Co-Cr samples produced using a Vulcan tech VM120 printer and Ti-6Al-4V samples created using a 160 BLT printer. All samples were finished using silicon carbide sheets with increasing grit sizes (180\u0026ndash;1000) to ensure consistent surface preparation.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Treatment Protocols\u003c/h2\u003e\u003cp\u003e The dental Co-Cr and Ti-6Al-4V sample treatment protocols were designed to simulate the acidic conditions experienced in the oral cavities of patients with gastroesophageal reflux disease (GERD). A simulated gastric acid solution (pH 1.2) was prepared according to the British Pharmacopoeia by dissolving 2.0 g NaCl and 7.0 mL of concentrated HCl in 1 L distilled water. The experimental methodology was implemented based on previous studies(\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e) with modifications to mimic the intermittent nature of acid exposure in the oral environment. Samples in the acidic group (SG-B) were subjected to a cyclic immersion protocol: they were immersed in the prepared acidic solution for 2 min, followed by thorough rinsing with distilled water to neutralize any residual acid. After each acid exposure, the samples were stored in distilled water at 37\u0026deg;C to simulate the oral cavity temperature. This immersion cycle was repeated six times daily for nine consecutive days, with a 24-hour interval between each day's set of cycles. This regimen was designed to represent the cumulative effects of multiple acid reflux episodes over an extended period. The control group (SG-A) was maintained in distilled water (pH 6.7) at 37\u0026deg;C for the same duration.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Electrochemical Experiments\u003c/h2\u003e\u003cp\u003eElectrochemical experiments were conducted using a GAMRY Reference 3000 potentiostat/galvanostat/ZRA analyzer. A classical three-electrode setup was employed, consisting of the sample under test as the working electrode (exposed surface area of 0.25 cm\u0026sup2;), a saturated calomel electrode (SCE) as the reference electrode, and a Pt grid as the counter electrode. The electrochemical cell was filled with either simulated gastric acid solution (pH 1.2) or distilled water (pH 6.7) as the electrolyte and maintained at 37\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u0026deg;C using a thermostatic water bath. Prior to testing, the samples were cleaned with ethanol, rinsed with distilled water, dried with compressed air, and stabilized in the electrolyte for 1 h to achieve a steady open-circuit potential (OCP). Electrochemical impedance spectroscopy (EIS) measurements were performed by applying an AC excitation of 10 mV amplitude (peak-to-zero) over a frequency range of 100 kHz to 10 mHz at the OCP, with 10 data points collected per decade. The EIS data were analyzed using GAMRY Echem Analyst software to fit Nyquist plots to extract parameters such as the charge transfer resistance (Rct) and double-layer capacitance (Cdl).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5 Surface Morphology and Topography Analysis\u003c/h2\u003e\u003cp\u003eA scanning electron microscope (SEM) (Prisma E, Thermo Fisher Co.) equipped with an energy-dispersive X-ray spectroscopy (EDX) unit was used to examine the surface morphology and elemental composition of the samples. SEM imaging was performed at an accelerating voltage of 30 kV. The surface morphologies of the tested alloys in both acidic and neutral solutions were evaluated using oxide percentage analysis, in which the extent of oxide formation on the alloy surface was quantified. In addition, a roughness profile analysis was conducted to assess changes in the surface texture. The Abbott-Firestone approach was utilized to determine the surface topography of the corrosion-tested samples, providing insights into the distribution of peaks, voids, and bearing areas. This method involves generating cumulative height distribution curves and analyzing key parameters.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6 Statistical Analysis\u003c/h2\u003e\u003cp\u003eAn independent t-test was used for intra- and intergroup comparisons between the two types of solutions (neutral and acidic) and between the two types of alloys (Co/Cr and Ti-6Al-4V). Differences were considered statistically significant (95% significance level). A p-value\u0026thinsp;\u0026le;\u0026thinsp;0.001 was considered to be highly statistically significant (99% significance level). Shapiro\u0026ndash;Wilk test was used to test the normality of the data. Data was analyzed using the statistical software SPSS version 25 (IBM Co. USA).\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Electrochemical behavior\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents the electrochemical behavior of the Co-Cr and Ti-6Al-4V alloys in acidic and neutral solutions. In the acidic solution, the Ti-6Al-4V alloy exhibited superior corrosion resistance compared to the Co-Cr alloy. The Ti-6Al-4V alloy demonstrated superior corrosion resistance compared to the Co-Cr alloy in both acidic and neutral environments. In the acidic solution, Ti-6Al-4V exhibited a lower corrosion current density (i\u003csub\u003ecorr\u003c/sub\u003e) of 20.7 \u0026micro;A/cm\u003csup\u003e2\u003c/sup\u003e compared to 37.2 \u0026micro;A/cm\u003csup\u003e2\u003c/sup\u003e for Co-Cr (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), indicating a better resistance to corrosion. This trend was even more pronounced in the neutral solution, with Ti-6Al-4V exhibiting an icorr of 0.122 \u0026micro;A/cm\u003csup\u003e2\u003c/sup\u003e versus 1.6 \u0026micro;A/cm\u003csup\u003e2\u003c/sup\u003e for Co-Cr. The corrosion rate (CR) values were significantly lower for Ti-6Al-4V in both solutions, especially in the neutral solution, where it showed a CR of 0.158 mpy compared to 1.4 mpy for Co-Cr (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The results listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e indicate that the Ti-6Al-4V alloy is more resistant to corrosion and surface alterations in both acidic and neutral solutions. Figures\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e present the electrochemical impedance spectroscopy (EIS) results for the Co-Cr and Ti-6Al-4V alloys, respectively, in both acidic (pH 1.2) and neutral (pH 6.7) solutions. It can be remarked that for the Co-Cr (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and Ti-6Al-4V alloys (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), there is a stark contrast between their behavior in acidic and neutral solutions. In the acidic solution (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea), the Nyquist plot of Co-Cr shows a small, depressed semicircle with a diameter of approximately 350 Ohm.cm\u0026sup2;. This indicates a relatively low charge transfer resistance, suggesting that the Co-Cr alloy is more susceptible to corrosion in acidic solution. The depressed nature of the semicircle can be attributed to the formation of oxides under acidic conditions. In contrast, the Co-Cr alloy in the neutral solution (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) exhibited a much larger semicircle with a diameter exceeding 800,000 Ohm.cm\u0026sup2;. This significant increase in the diameter of the semicircle indicates a substantially higher charge transfer resistance, implying an enhanced corrosion resistance in a neutral solution. The near-perfect semicircular shape suggests the formation of a more uniform and stable passive layer on the alloy surface under neutral conditions. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e illustrates the EIS results for the Ti-6Al-4V alloy. In the acidic solution (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea), the Nyquist plot revealed a semicircle with a diameter of approximately 420 Ohm.cm\u0026sup2;. Although this is larger than that of Co-Cr under acidic conditions, it still indicates some vulnerability to corrosion. The Ti-6Al-4V alloy in the neutral solution (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) demonstrated greater corrosion resistance, with a semicircle diameter of approximately 886,000 Ohm.cm\u0026sup2;. This value was slightly higher than that of Co-Cr under neutral conditions, indicating superior corrosion resistance. The near-perfect semicircle shape implies a highly stable and uniform passive layer on the Ti-6Al-4V surface in a neutral solution. Comparing the two alloys, Ti-6Al-4V consistently showed better corrosion resistance than Co-Cr under both acidic and neutral conditions. This is evidenced by the larger semicircle diameters of both solutions. The difference was particularly pronounced in the acidic solution, where Ti-6Al-4V exhibited a significantly higher charge transfer resistance.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eCorrosion results of Co-Cr and Ti-6Al-4V alloys after immersion test in acidic and neutral solutions\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSolution\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ei\u003csub\u003ecorr\u003c/sub\u003e (\u0026micro;A/ cm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCR (mpy)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e1.2\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTi-6Al-4V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e20.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e18.34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCo-Cr\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e37.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e34.04\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003e6.7\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTi-6Al-4V\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.122\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.158\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCo-Cr\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.40\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the EDX results for the Co-Cr and Ti-6Al-4V alloys after immersion testing in acidic and neutral solutions. \u003cb\u003eFor the Co-Cr alloy\u003c/b\u003e, there was a statistically significant increase in oxygen content from 3.83% in the neutral solution to 6.37% in the acidic solution (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). This substantial increase in oxygen suggests more extensive oxide formation on the Co-Cr surface under acidic conditions, which aligns with the lower corrosion resistance observed in the electrochemical behavior shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e \u003cb\u003eand\u003c/b\u003e Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. In contrast, the Ti-6Al-4V alloy showed a smaller, non-significant increase in oxygen content from 0.69% to 2.26% when exposed to an acidic solution (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). This relatively minor change in oxygen content corresponds to the superior corrosion resistance of the alloy, as detected in the electrochemical behavior of Ti-6Al-4V (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The stability of the Ti-6Al-4V surface composition, particularly the limited increase in oxygen, contributed to its better performance in acidic solutions. The intergroup comparison of the oxygen content between the two alloys was statistically significant in both neutral (p\u0026thinsp;=\u0026thinsp;0.002) and acidic (p\u0026thinsp;=\u0026thinsp;0.008) solutions. This significant difference in oxide formation correlates with the distinct corrosion behavior observed in the electrochemical tests. Therefore, previous results indicate that while both alloys experience some degree of oxidation in acidic solutions, the Ti-6Al-4V alloy maintains better surface stability and corrosion resistance. This is reflected in both its electrochemical behavior and the limited changes in its elemental composition, particularly the oxygen content, when exposed to simulated gastric acid.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD of the percentage of elements (wt%) in different solution pH values for both alloys.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAlloy\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eElement\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNeutral\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAcidic\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eP-value*\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"1\" nameend=\"c6\" namest=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e\u003cp\u003e\u003cb\u003eCo/Cr\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.23\u0026thinsp;\u0026plusmn;\u0026thinsp;1.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.21\u0026thinsp;\u0026plusmn;\u0026thinsp;2.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.990\u003csup\u003eNS\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c6\" namest=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.83\u0026thinsp;\u0026plusmn;\u0026thinsp;2.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.37\u0026thinsp;\u0026plusmn;\u0026thinsp;1.77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.036\u003csup\u003eS\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c6\" namest=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCr\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.31\u0026thinsp;\u0026plusmn;\u0026thinsp;2.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e22\u0026thinsp;\u0026plusmn;\u0026thinsp;1.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.778\u003csup\u003eNS\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c6\" namest=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e53.64\u0026thinsp;\u0026plusmn;\u0026thinsp;3.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e51.51\u0026thinsp;\u0026plusmn;\u0026thinsp;2.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.199\u003csup\u003eNS\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c6\" namest=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14.31\u0026thinsp;\u0026plusmn;\u0026thinsp;1.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e13.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.346\u003csup\u003eNS\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e\u003cb\u003eTi-6Al-4V\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.84\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.058\u003csup\u003eNS\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.69\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.26\u0026thinsp;\u0026plusmn;\u0026thinsp;1.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.141\u003csup\u003eNS\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.484\u003csup\u003eNS\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTi\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.06\u0026thinsp;\u0026plusmn;\u0026thinsp;2.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e92.07\u0026thinsp;\u0026plusmn;\u0026thinsp;2.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.428\u003csup\u003eNS\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eP-Value\u003c/b\u003e\u003csup\u003e\u003cb\u003e*\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.002\u003csup\u003eS**\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.008\u003csup\u003eS\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003csup\u003e\u003cem\u003e*\u003c/em\u003e\u003c/sup\u003e \u003cem\u003eP-value comparison between the two solutions (Independent T- test).\u003c/em\u003e\u003c/p\u003e\u003cp\u003e\u003csup\u003e\u003cem\u003e*\u003c/em\u003e\u003c/sup\u003e \u003cem\u003eP-value comparison of O between the two alloys in different solutions (Independent T- test).\u003c/em\u003e\u003c/p\u003e\u003cp\u003e\u003csup\u003e\u003cem\u003e**\u003c/em\u003e\u003c/sup\u003e \u003cem\u003eS\u0026thinsp;=\u0026thinsp;Statistically significant at P\u0026thinsp;\u0026le;\u0026thinsp;0.05; NS\u0026thinsp;=\u0026thinsp;Non-significant P\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Surface Morphology\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) SEM of the tested alloys and (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) the formation of oxide layers on the Co-Cr and Ti-6Al-4V alloy surfaces when exposed to acidic and neutral solutions, respectively. It can be remarked that Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows more extensive oxide (black area; Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and blue area; Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) deposits on the Co-Cr surfaces compared to Ti-6Al-4V, especially in acidic solutions. Furthermore, both alloys demonstrated higher resistance to oxide formation in a neutral solution than in an acidic solution. Oxide formation appears as distinct surface features that alter the topography of the alloy surfaces. For the Co-Cr alloy (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea,b), there was a dramatic increase in oxide formation when exposed to the acidic solution compared to that in the neutral solution. The percentage of deposited oxides increased from 29.46% in neutral solution to 58.91% in acidic solution. This substantial difference suggests that the acidic solution significantly accelerated the oxidation of the Co-Cr surface. A higher oxide percentage under acidic conditions indicates greater corrosion activity and potential degradation of the Co-Cr alloy. In contrast, the Ti-6Al-4V alloy (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec,d) showed much lower overall oxide formation in both solutions. The percentage of oxides increased from 1.57% in neutral solutions to 6.16% in acidic solutions. Although this represents a notable increase, the oxide percentage for Ti-6Al-4V was considerably lower than that observed for Co-Cr. This finding aligns with the well-known excellent corrosion resistance of Ti-6Al-4V, which is attributed to its ability to form a stable passive oxide layer. These observations of oxide formation (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) align with the EDX results in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, which show a significant increase in the oxygen content for the Co-Cr alloy from 3.83% to 6.37% under acidic conditions, whereas the Ti alloy exhibited a smaller, non-significant increase from 0.69% to 2.26%, owing to the superior corrosion resistance of TofAl-4V compared to Co-Cr under acidic conditions. It can be concluded that the SEM images (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) clearly show more extensive oxide deposits on the Co-Cr surfaces than on Ti-6Al-4V, especially in acidic solution. Oxide formations appear as distinct surface features that alter the topography of the alloy surfaces.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e show the surface roughness characteristics of the Co-Cr and Ti-6Al-4V alloys exposed to acidic and neutral solutions, respectively. The data revealed significant differences in the responses of the two alloys to different pH solutions, particularly in terms of surface roughness. For the Co-Cr alloy, there was a substantial increase in surface roughness when exposed to the acidic solution compared with the neutral solution. The mean Ra value increased from 16.09\u0026thinsp;\u0026plusmn;\u0026thinsp;1.27 in the neutral solution to 25.30\u0026thinsp;\u0026plusmn;\u0026thinsp;1.83 in the acidic solution, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. This difference was statistically significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), indicating that the acidic solution had a pronounced effect on the surface topography of the Co-Cr alloy specimens. The increased roughness suggests that the acidic solution likely caused more aggressive corrosion or etching of the Co-Cr surface. In contrast, the Ti-6Al-4V alloy demonstrated much greater stability in terms of surface roughness under both pH conditions. The mean Ra value increased only slightly from 11.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.82 in the neutral solution to 13.60\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42 in the acidic solution (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). This difference was not statistically significant (p\u0026thinsp;=\u0026thinsp;0.838), suggesting that the Ti-6Al-4V alloy surface was more resistant to changes induced by the acidic solution. This stability can be attributed to the well-known ability of Ti-6Al-4V to form a protective oxide layer, which effectively shields the bulk material from significant acid-induced surface alterations. Comparing the two alloys, it is evident that the Co-Cr alloy consistently exhibited a higher surface roughness than the Ti-6Al-4V alloy under both neutral and acidic conditions. The difference in Ra between the two alloys was highly statistically significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) in both pH solutions. This suggests that even under neutral conditions, the Co-Cr alloy has an inherently rougher surface than the Ti-6Al-4V alloy, a characteristic that becomes even more pronounced under acidic conditions. These observations of oxide formation align with the EDX results in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, which showed a significant increase in oxygen content for the Co-Cr alloy from 3.83% to 6.37% under acidic conditions, while the Ti alloy exhibited a smaller, non-significant increase from 0.69% to 2.26%, confirming the superior corrosion resistance of Ti-6Al-4V compared to Co-Cr in simulated gastric acid environments. It can be concluded that the observed increase in the surface roughness of the Co-Cr alloy under acidic conditions may raise concerns regarding its long-term stability and potential for increased bacterial adhesion or food debris accumulation in acidic solutions.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD of Ra in different solutions pH (acidic and neutral solutions) for both alloys.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAlloy\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAcidic\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNeutral\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP-value*\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCo/Cr\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e25.30\u0026thinsp;\u0026plusmn;\u0026thinsp;1.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e16.09\u0026thinsp;\u0026plusmn;\u0026thinsp;1.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003e\u003cb\u003eHS\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTi-6Al-4V\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e13.60\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.838\u003csup\u003e\u003cb\u003eNS\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eP-value**\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003e\u003cb\u003eHS\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003e\u003cb\u003eHS\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e-* P-value comparison between the two solutions (Independent T- test).\u003c/p\u003e\u003cp\u003e* P-value comparison of Ra between the two alloys in different solutions (Independent T- test).\u003c/p\u003e\u003cp\u003eHS\u0026thinsp;=\u0026thinsp;Highly significant at P\u0026thinsp;\u0026le;\u0026thinsp;0.001; NS\u0026thinsp;=\u0026thinsp;Non-significant P\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Surface Topography\u003c/h2\u003e\u003cp\u003eSurface topography using Abbott\u0026ndash;Firestone analysis is a valuable technique for characterizing surface topography in materials science and engineering. The Abbott-Firestone curve provides a cumulative probability distribution of the surface heights, offering a comprehensive view of the topographical features of the surface. The Abbott-Firestone technique is particularly useful for evaluating the performance of surfaces in contact situations, such as those encountered in dental implants or prosthetics. The Abbott-Firestone curves show the distribution of peaks, voids, and exploitation surfaces on the alloy samples, which are critical factors in determining the wear resistance, friction characteristics, and potential for material degradation. In the context of this study, the Abbott-Firestone analysis allowed for a more nuanced understanding of how exposure to acidic and neutral solutions affects the surface topography of Co-Cr and Ti-6Al-4V alloys. This information is vital because changes in surface characteristics can significantly affect the performance and longevity of dental materials in oral solutions. For instance, an increase in the exploitation area ratio can potentially improve the wear resistance of dental materials during chewing. In addition, an increase in the void area could potentially lead to an increased probability of bacterial adhesion or food debris accumulation. The Abbott-Firestone approach complements the observations obtained through SEM imaging and elemental analysis, providing a more comprehensive analysis of the corrosion resistance and surface stability, bacterial adhesion, and food debris accumulaTi-6Al-4V on these alloys. Figures\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e show the surface topography analysis using the Abbott\u0026ndash;Firestone approach for the Co-Cr (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e) and Ti-6Al-4V (Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e and \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e) surfaces after immersion tests in acidic and neutral solutions. For the Co-Cr alloy (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e), the neutral solution led to a significant improvement in the surface topography compared with the acidic solution. The percentage of peaks decreased from 12% in the neutral solution to 8% in the acidic solution, indicating a rougher surface. Additionally, the void percentage was less than half, ranging from 5% to 2%. The exploitation zone, which represents the primary load-bearing area, increased from 83% to 90%. These changes collectively resulted in a higher total roughness (Rt) of 145.84 \u0026micro;m in the acidic solution compared to 106.61 \u0026micro;m in the neutral solution. Ti-6Al-4V alloys exhibited different behaviors under neutral conditions, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e and \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e. Unlike Co-Cr, Ti-6Al-4V showed a slight increase in the peak percentage from 10% under neutral conditions to 11% under neutral conditions. However, the void percentage decreased significantly from 6% to 1%. The exploitation zone increased marginally from 84% to 88% of the total area. The total roughness (Rt) decreased from 116.41 \u0026micro;m under acidic conditions to 96.3 \u0026micro;m under neutral conditions. \u003cb\u003ePeak formation analysis\u003c/b\u003e: For the Co-Cr alloy, the percentage of peaks decreased significantly from 12% in acidic solution to 8% in neutral solution. This represents a 33% decrease in peak formation when exposed to an acidic solution. For the Ti-6Al-4V alloy, the percentage of peaks increased slightly from 10% in the acidic solution to 11% in the neutral solution. The substantial reduction in the peak percentage suggests that the Co-Cr alloy experiences considerable surface roughening under acidic conditions, potentially leading to a more irregular surface topography. The minor 1% change in peak formation in the Ti-6Al-4V alloy between acidic and neutral solutions indicates that the Ti-6Al-4V alloy maintains a more stable surface topography even when exposed to acidic conditions, showing a lower tendency for surface roughening. Comparing the two alloys, it is evident that the Co-Cr alloy experienced a more dramatic change in the peak formation when exposed to acidic solutions. The 50% increase in Co-Cr compared to the 9% decrease in Ti-6Al-4V suggests that Co-Cr may be more susceptible to surface alterations under acidic conditions. This could potentially lead to increased surface roughness and irregularities over time. These results were confirmed by morphological analysis (Section \u003cspan refid=\"Sec11\" class=\"InternalRef\"\u003e3.2\u003c/span\u003e). \u003cb\u003eExploitation zone analysis\u003c/b\u003e: For the Co-Cr alloy, the exploitation zone increased significantly from 83% in the acidic solution to 90% in the neutral solution. This represents a 7% improvement in the primary load bearing area under acidic conditions. However, the Ti-6Al-4V alloy demonstrated greater stability in the exploitation zone. The exploitation zone increased marginally, from 84% in the acidic solution to 88% in the neutral solution, representing an improvement of only 4%. This smaller change, compared to that of the Co-Cr alloy, indicates that the Ti-6Al-4V alloy maintained a more consistent surface topography and load-bearing area, even when exposed to acidic conditions. In addition, both alloys maintained a higher exploitation zone of over 88% in a neutral solution, suggesting potentially better wear resistance, load-bearing capacity during chewing food processing, and a long lifetime under neutral conditions. \u003cb\u003eVoid analysis\u003c/b\u003e: For the Co-Cr alloy, the void percentage decreased from 5% under neutral conditions to 2% under acidic conditions. This represents a 60% decrease in the void percentage when exposed to a neutral solution. In contrast, the Ti-6Al-4V alloy exhibited a greater reduction in the void percentage. Under acidic conditions, the void percentage was 6%, which decreased to 1% when exposed to a neutral solution. This represents an 83% decrease in the void percentage, which is significantly higher than the change observed in the Co-Cr alloy. It can be concluded that the Ti-6Al-4V and Co-Cr alloys exhibited a more substantial decrease in the void percentage, which could potentially decrease the surface defects and corrosion pits and increase the resistance to bacterial adhesion and food debris accumulation, particularly in Ti-6Al-4V alloys.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThis comprehensive study on the impact of simulated gastric acid on 3D printed Co-Cr and Ti-6Al-4V dental alloys revealed a complex interplay between surface characteristics, corrosion resistance, and topographical changes. The results consistently demonstrated the higher performance of Ti-6Al-4V over Co-Cr in acidic environments, mimicking the conditions experienced by patients with gastroesophageal reflux disease (GERD). Electrochemical behavior analysis showed that Ti-6Al-4V exhibited a lower corrosion current density (icorr) and corrosion rate (CR) than Co-Cr in both acidic and neutral solutions (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The higher corrosion resistance of Ti-6Al-4V can be attributed to its ability to form a stable, adherent, and self-healing passive oxide layer primarily composed of TiO\u003csub\u003e2\u003c/sub\u003e. This protective layer is highly effective in resisting corrosion in various environments, including acidic and neutral solutions.(\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e) The presence of Al and V in the alloy further enhanced the stability and protective nature of the oxide layer, contributing to its improved corrosion resistance. Furthermore, the electrochemical nobility of Ti is higher than those of Co and Cr, which inherently makes Ti-6Al-4V less susceptible to corrosion in different pH environments.(\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e) This property, combined with the robust passive oxide layer, results in a lower corrosion current density (icorr) and corrosion rate (CR) for Ti-6Al-4V compared to Co-Cr alloys. Although Co-Cr alloys also form a protective oxide layer, primarily composed of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, it may not be as stable or protective as the oxide layer formed on Ti-6Al-4V, especially in more aggressive environments.(\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e) This difference in the oxide layer stability and protective properties explains the observed lower icorr and CR values for Ti-6Al-4V in both acidic and neutral solutions. The lower icorr and CR values for Ti-6Al-4V indicate that it undergoes less electrochemical dissolution than Co-Cr when exposed to both acidic and neutral environments. This is particularly significant in dental applications, where materials are frequently exposed to varying pH levels in the oral cavity. The superior corrosion resistance of Ti-6Al-4V is further supported by the EDX results (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), which show a smaller increase in the oxygen content for Ti-6Al-4V (from 0.69% to 2.26%) than for Co-Cr (from 3.83% to 6.37%) when exposed to acidic conditions. The significant increase in oxygen content for Co-Cr indicates more extensive oxide formation, which is visually confirmed by SEM analysis showing larger oxide deposits on Co-Cr surfaces, particularly in acidic solutions. Increased thickness of the oxide layer may be associated with a higher degree of metal ion release. However, increased ion release of Co\u0026ndash;Cr alloy in acidic conditions doesn\u0026rsquo;t exceed the limits of cell viability according to standards.(\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eSurface roughness measurements were consistent with these findings, demonstrating a substantial increase in Ra values for Co-Cr from 16.09 in neutral solution to 25.30 in acidic solution, while Ti-6Al-4V maintained relatively stable Ra values across both conditions (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e \u003cb\u003eand\u003c/b\u003e Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The surface roughness of Ti-6Al-4V correlates with its superior corrosion resistance, suggesting better long-term performance in acidic oral environments. The Abbott-Firestone analysis results for the Ti-6Al-4V and Co-Cr alloys provided valuable insights into their topographical changes under different pH conditions, which have significant implications for dental applications. The more dramatic changes observed in the Co-Cr peak formation and exploitation zone under acidic conditions compared to Ti-6Al-4V (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e), can be attributed to the different corrosion behaviors of these alloys. Ti-6Al-4V typically forms a more stable and protective TiO\u003csub\u003e2\u003c/sub\u003e layer that is resistant to breakdown, even in acidic environments. This protective layer helps to maintain the surface topography of Ti-6Al-4V more effectively than that of Co-Cr alloys. The reduction in the void percentage observed for both alloys in neutral solutions is a positive finding for their dental applications. This change in surface topography can lead to potential resistance to bacterial adhesion and accumulation of food debris.(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e) A surface with fewer voids provides less space for bacteria to adhere and colonize, which can significantly impede biofilm formation. Additionally, a smoother surface with fewer voids is easier to clean, reducing the likelihood of food debris accumulation and helping to maintain better oral hygiene in patients with dental implants or prostheses.(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e) The importance of these topographical changes extends beyond the bacterial adhesion and debris accumulation. The reduction in surface voids can also contribute to improved corrosion resistance by minimizing the areas where corrosive agents can accumulate and initiate localized corrosion.(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e) This is particularly relevant in the dynamic oral environment, where pH fluctuations and various chemical challenges are common. It can be concluded that the Abbott-Firestone analysis results suggest that both Ti-6Al-4V and Co-Cr alloys may offer improved resistance to bacterial adhesion and food debris accumulation under neutral conditions, which is highly beneficial for dental applications in patients with GERD. Moreover, the stability of Ti-6Al-4V in acidic environments further substantiates its suitability for patients with GERD.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eBased on the comprehensive analysis presented in this study, the following conclusions can be drawn;\u003c/p\u003e\u003cp\u003eTi-6Al-4V exhibited superior corrosion resistance compared to Co-Cr in both acidic and neutral solutions, with lower corrosion current density (icorr) and corrosion rate (CR) values. In an acidic solution, Ti-6Al-4V showed an icorr of 20.70 \u0026micro;A/cm\u003csup\u003e2\u003c/sup\u003e compared to 37.20 \u0026micro;A/cm\u003csup\u003e2\u003c/sup\u003e for Co-Cr, indicating a better resistance to corrosion.The increase in oxygen content for Ti-6Al-4V (from 0.69% to 2.26%) was smaller than that for Co-Cr (from 3.83% to 6.37%) when exposed to acidic conditions, suggesting less oxide formation.The surface roughness (Ra) of Co-Cr increased significantly from 16.09\u0026thinsp;\u0026plusmn;\u0026thinsp;1.27 in neutral solution to 25.30\u0026thinsp;\u0026plusmn;\u0026thinsp;1.83 in acidic solution, while Ti-6Al-4V maintained more stable Ra values of 11.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.82 to 13.60\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42.Abbott-Firestone analysis showed that Co-Cr experienced a more dramatic change in peak formation from 12% to 8% and exploitation zone from 83% to 90% under acidic conditions compared to Ti-6Al-4V.Both alloys exhibited a decrease in the void percentage in neutral solutions, with Ti-6Al-4V showing a greater reduction from 6% to 1% compared to Co-Cr, which decreased from 5% to 2%. Ti-6Al-4V demonstrated greater stability in surface topography across different pH conditions, making it more suitable for dental applications in patients with GERD.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eKawkb M. El-Tamimi, Dalia A. Bayoumi\u003c/strong\u003e,\u003cstrong\u003e\u0026nbsp;Sherif E. Zahra\u003c/strong\u003e and \u003cstrong\u003eMohammed E. El-Sayed\u003c/strong\u003e were contributed to the study\u0026rsquo;s conception and design. \u003cstrong\u003eKawkb M. El-Tamimi\u003c/strong\u003e and \u003cstrong\u003eDalia A. Bayoumi\u003c/strong\u003e performed material preparation, data collection, and analysis. \u003cstrong\u003eKawkb M. El-Tamimi and Mohamed\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;I. A. Habba\u003csup\u003e\u0026nbsp;\u003c/sup\u003e\u003c/strong\u003ewrote the original draft of the manuscript. \u003cstrong\u003eMohamed M. Z. Ahmed\u003c/strong\u003e reviewed the manuscript. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors received no specific funding for this work.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor details\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e1\u0026nbsp;\u003c/sup\u003eDepartment of Removable Prosthodontics, Faculty of Dentistry, Suez Canal University, Ismailia 41522, Egypt.\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e2\u003c/sup\u003e Department of Dental Biomaterials, Faculty of Dentistry, Suez Canal University, Ismailia 41522, Egypt.\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e3\u003c/sup\u003e Mechanical Engineering Department, College of Engineering at Al Kharj, Prince Sattam Bin Abdulaziz University, Al Kharj 11942, Saudi Arabia.\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e4\u0026nbsp;\u003c/sup\u003eDepartment of Metallurgical and Materials Engineering, Faculty of Petroleum and Mining Engineering, Suez University, Suez 43512, Egypt.\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e5\u003c/sup\u003e Mechanical Department, Faculty of Technology and Education, Suez University, Suez 43518, Egypt.\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e6\u003c/sup\u003e Department of Orthodontics, Faculty of Dentistry, Suez Canal University, Ismailia 41522, Egypt.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMarin E. History of dental biomaterials: biocompatibility, durability and still open challenges. Vol. 11, Heritage Science. Springer Science and Business Media Deutschland GmbH; 2023. \u003c/li\u003e\n\u003cli\u003eSta\u0026scaron;kov\u0026aacute; A, Nemcov\u0026aacute; R, Lauko S, Jenča A. Oral Microbiota from the Stomatology Perspective. In: Bacterial Biofilms. IntechOpen; 2020. \u003c/li\u003e\n\u003cli\u003eEliaz N. Corrosion of Metallic Biomaterials: A Review. Materials. 2019 Jan 28;12(3):407. \u003c/li\u003e\n\u003cli\u003eAli RAR, Egan LJ. Gastroesophageal reflux disease in pregnancy. Best Pract Res Clin Gastroenterol. 2007;21(5):793\u0026ndash;806. \u003c/li\u003e\n\u003cli\u003eAkinola MA, Oyedele TA, Akande KO, Oluyemi OY, Salami OF, Adesina AM, et al. Gastroesophageal reflux disease: prevalence and Extraesophageal manifestations among undergraduate students in South West Nigeria. BMC Gastroenterol. 2020 Dec 26;20(1):160. \u003c/li\u003e\n\u003cli\u003eLin S, Li H, Fang X. Esophageal Motor Dysfunctions in Gastroesophageal Reflux Disease and Therapeutic Perspectives. J Neurogastroenterol Motil. 2019 Oct 30;25(4):499\u0026ndash;507. \u003c/li\u003e\n\u003cli\u003eAntunes C, Aleem A, Curtis SA. Gastroesophageal Reflux Disease. 2024. \u003c/li\u003e\n\u003cli\u003eKawar N, Park SG, Schwartz JL, Callahan N, Obrez A, Yang B, et al. Salivary microbiome with gastroesophageal reflux disease and treatment. Sci Rep. 2021 Jan 8;11(1):188. \u003c/li\u003e\n\u003cli\u003eArmencia1 AO, Cristina TC, Lese A, Feier R, Scutariu MM, Balcos C. THE STUDY OF ROUGHNESS AND RESISTANCE TO CORROSION OF DENTAL ALLOYS IN THE ORAL ENVIRONMENT. Vol. 12, Romanian Journal of Oral Rehabilitation. \u003c/li\u003e\n\u003cli\u003eDawes C. What is the critical pH and why does a tooth dissolve in acid? J Can Dent Assoc. 2003 Dec;69(11):722\u0026ndash;4. \u003c/li\u003e\n\u003cli\u003eAdya N, Alam M, Ravindranath T, Mubeen A, Saluja B. Corrosion in titanium dental implants: literature review. The Journal of Indian Prosthodontic Society. 2005;5(3):126. \u003c/li\u003e\n\u003cli\u003eM.Kaczmarek WWWK. chemical composition of passive layer formed on metallic biomaterials . Materials Science, Chemistry Archives of materials Science and engineering . 2007 May;28(5). \u003c/li\u003e\n\u003cli\u003eWilson J. Fundamental Biomaterials: Metals. Preetha Balakrishnan, Sreekala M S, Sabu Thomas, editors. Elsevier; 2018. 1\u0026ndash;33 p. \u003c/li\u003e\n\u003cli\u003eChen L, He Y, Yang Y, Niu S, Ren H. The research status and development trend of additive manufacturing technology. The International Journal of Advanced Manufacturing Technology. 2017 Apr 24;89(9\u0026ndash;12):3651\u0026ndash;60. \u003c/li\u003e\n\u003cli\u003eRen XW, Zeng L, Wei ZM, Xin XZ, Wei B. Effects of multiple firings on metal-ceramic bond strength of Co-Cr alloy fabricated by selective laser melting. J Prosthet Dent. 2016 Jan;115(1):109\u0026ndash;14. \u003c/li\u003e\n\u003cli\u003eŞahin M, \u0026Uuml;nalan F, Mutlu İ. Corrosion, ion release, and surface hardness of Ti-6Al-4V and cobalt-chromium alloys produced by CAD-CAM milling and laser sintering. J Prosthet Dent. 2022 Sep;128(3):529.e1-529.e10. \u003c/li\u003e\n\u003cli\u003eFaul F, Erdfelder E, Lang AG, Buchner A. G*Power 3: A flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods. 2007 May;39(2):175\u0026ndash;91. \u003c/li\u003e\n\u003cli\u003eKulkarni A, Rothrock J, Thompson J. Impact of Gastric Acid Induced Surface Changes on Mechanical Behavior and Optical Characteristics of Dental Ceramics. Journal of Prosthodontics. 2020 Mar 1;29(3):207\u0026ndash;18. \u003c/li\u003e\n\u003cli\u003eAbbate-Daga G, Pier\u0026ograve; A, Gramaglia C, Fassino S. Factors related to severity of vomiting behaviors in bulimia nervosa. Psychiatry Res. 2005 Mar 30;134(1):75\u0026ndash;84. \u003c/li\u003e\n\u003cli\u003eSocorro-Perdomo PP, Florido-Su\u0026aacute;rez NR, Mirza-Rosca JC, Saceleanu MV. EIS Characterization of Ti Alloys in Relation to Alloying Additions of Ta. Materials. 2022 Jan 8;15(2):476. \u003c/li\u003e\n\u003cli\u003eWong KK, Hsu HC, Wu SC, Ho WF. A Review: Design from Beta Titanium Alloys to Medium-Entropy Alloys for Biomedical Applications. Materials. 2023 Nov 5;16(21):7046. \u003c/li\u003e\n\u003cli\u003eManaka T, Tsutsumi Y, Takada Y, Chen P, Ashida M, Doi K, et al. Galvanic Corrosion among Ti\u0026ndash;6Al\u0026ndash;4V ELI Alloy, Co\u0026ndash;Cr\u0026ndash;Mo Alloy, 316L-Type Stainless Steel, and Zr\u0026ndash;1Mo Alloy for Orthopedic Implants. Mater Trans. 2023 Jan 1;64(1):MT-MLA2022001. \u003c/li\u003e\n\u003cli\u003eGhisheer MMM, Esen I, Ahlatci H, Akın B. Investigation of Microstructure, Mechanics, and Corrosion Properties of Ti6Al4V Alloy in Different Solutions. Coatings. 2024 Feb 25;14(3):277. \u003c/li\u003e\n\u003cli\u003eSwaminathan V, Zeng H, Lawrynowicz D, Zhang Z, Gilbert JL. Electrochemical investigation of chromium oxide‐coated Ti‐6Al‐4V and Co‐Cr‐Mo alloy substrates. J Biomed Mater Res B Appl Biomater. 2011 Aug 6;98B(2):369\u0026ndash;78. \u003c/li\u003e\n\u003cli\u003eKassapidou M, Hjalmarsson L, Johansson CB, Hammarstr\u0026ouml;m Johansson P, Morisbak E, Wennerberg A, et al. Cobalt\u0026ndash;chromium alloys fabricated with four different techniques: Ion release, toxicity of released elements and surface roughness. Dental Materials. 2020 Nov;36(11):e352\u0026ndash;63. \u003c/li\u003e\n\u003cli\u003eLorenzetti M, Dog\u0026scaron;a I, Sto\u0026scaron;icki T, Stopar D, Kalin M, Kobe S, et al. The Influence of Surface Modification on Bacterial Adhesion to Titanium-Based Substrates. ACS Appl Mater Interfaces. 2015 Jan 28;7(3):1644\u0026ndash;51. \u003c/li\u003e\n\u003cli\u003ePreedy E, Perni S, Nipiĉ D, Bohinc K, Prokopovich P. Surface Roughness Mediated Adhesion Forces between Borosilicate Glass and Gram-Positive Bacteria. Langmuir. 2014 Aug 12;30(31):9466\u0026ndash;76. \u003c/li\u003e\n\u003cli\u003eVelic A, Mathew A, Hines P, Yarlagadda P. Control of bacterial adhesion and distribution on Ti-6Al-4V surfaces by fracture topography. 2019 Sep. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Salivary pH, 3D printing, Co-Cr and Ti-6Al-4V alloys, Corrosion, Morphology, Topography, Gastroesophageal reflux disease (GERD)","lastPublishedDoi":"10.21203/rs.3.rs-7735818/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7735818/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eThis in vitro study aimed to ascertain how 3D printed cobalt chromium (Co-Cr) and titanium (Ti-6Al-4V) alloys react to simulated stomach acid with a pH of 1.2.\u003c/p\u003e\u003ch2\u003eMaterials and methods\u003c/h2\u003e\u003cp\u003eA comparative in vitro investigation assessed 32 samples (n\u0026thinsp;=\u0026thinsp;16/group) of 3D printed cobalt chromium (Co-Cr) and titanium (Ti-6Al-4V) alloys. Each alloy was separated into two subgroups (n\u0026thinsp;=\u0026thinsp;8) based on the pH values of two distinct solutions: pH 1.2 and pH 6.7 pure water (control) solutions. The samples in the acidic pH subgroup were immersed in an acidic solution for two minutes, rinsed with distilled water, and stored in distilled water at 37\u0026deg;C. The procedure was repeated six times a day for nine days with a 24-hours interval between each cycle. The control group was maintained at 37\u0026deg;C in distilled water. The surface roughness of the samples was examined using scanning electron microscopy (SEM).\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eIn the Co\u0026ndash;Cr alloy, immersion in an acidic solution resulted in a decrease in the percentage of all elements except oxygen (O), which increased to 6.37\u0026thinsp;\u0026plusmn;\u0026thinsp;1.77%, with the change being statistically significant (P-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In contrast, the Ti alloy also show a decrease in all elements after immersion, with O rising to 2.26\u0026thinsp;\u0026plusmn;\u0026thinsp;1.22%, though no changes were statistically significant (P-value\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Comparatively, the oxygen percentages for both alloys were significantly different under neutral and acidic conditions. SEM images indicated more oxide deposits on Co-Cr in acidic solution, which also showed a notable increase in surface roughness, while Ti-6Al-4V exhibited greater stability. The Abbott-Firestone analysis further confirmed that Co-Cr underwent more significant changes in peak formation and exploitation zones than Ti-6Al-4V in acidic environments.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eThe Ti-6Al-4V alloy demonstrated superior corrosion resistance and surface stability compared with the Co-Cr alloy when exposed to simulated gastric acid, making it a more suitable choice for dental applications in patients with gastroesophageal reflux disease.\u003c/p\u003e","manuscriptTitle":"Impact of Simulated Gastric Acid on Electrochemical Behavior, Surface Morphology, and Topography of 3D Printed cobalt chromium and Titanium Alloys for Dental Applications","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-17 06:38:39","doi":"10.21203/rs.3.rs-7735818/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-09T22:02:36+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-01T19:32:30+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"27576754794363308198811382929239553449","date":"2026-02-22T18:16:13+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-28T15:39:35+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"91217379466479609232912595017237978086","date":"2026-01-15T14:14:28+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-14T08:49:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"275120823048317287918528976614939674732","date":"2025-11-27T15:43:58+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-11T07:07:44+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"164131193225933804074597177471921429363","date":"2025-11-08T06:23:31+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-11-06T00:28:49+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-10-30T21:17:52+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-28T11:52:43+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-10-28T11:51:51+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2025-09-28T17:16:19+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5aed0da4-0b37-4e01-925e-c85cded01a14","owner":[],"postedDate":"November 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-13T08:27:01+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-17 06:38:39","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7735818","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7735818","identity":"rs-7735818","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}