Innovative dentifrices based on bioactive silica for enamel remineralization and erosion control: an in vitro study

Innovative dentifrices based on bioactive silica for enamel remineralization and erosion control: an in vitro study | 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 Innovative dentifrices based on bioactive silica for enamel remineralization and erosion control: an in vitro study Elizabeth Barreto Galvão Sousa, Anderson Gomes Forte, Juliellen Luiz Cunha, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7359328/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 09 Dec, 2025 Read the published version in BMC Oral Health → Version 1 posted 10 You are reading this latest preprint version Abstract Background: Dental erosion and abrasion lead to progressive enamel loss, and preventive strategies often rely on fluoride dentifrices. Bioactive silica has emerged as a promising component due to its remineralizing potential, acting alone or synergistically with fluoride. This in vitro study evaluated the efficacy of bioactive silica dentifrices, with or without different fluoride concentrations, in promoting enamel remineralization and protecting against erosion‒abrasion cycles. Methods: Sixty bovine enamel samples were randomly assigned to five groups: RGS1 (bioactive silica dentifrice with 1450 ppm F), RGS2 (bioactive silica dentifrice with 1100 ppm F), RGS3 (bioactive silica dentifrice without fluoride), positive control (PC, 1100 ppm F dentifrice), and negative control (NC, fluoride- and silica-free dentifrice). The samples were subjected to a 5-day erosion-abrasion cycle with daily treatment with the assigned dentifrices. Enamel changes were assessed through surface microhardness recovery (%SMHR), fluorescence recovery (%ΔFR), surface loss (ΔSL), and surface roughness variation (ΔRa). The data were analyzed via one-way and repeated-measures ANOVA, followed by Tukey’s post hoc test (α = 0.05). Results: All tested dentifrices significantly affected enamel properties. Compared with the controls, bioactive silica dentifrices improved the microhardness and promoted greater mineral gain (p < 0.05). RGS2 demonstrated the highest %SMHR and ΔFR values, along with lowest surface roughness and enamel loss, indicating superior protective potential. RGS1, RGS3 and PC followed, with intermediate outcomes. The NC group exhibited the poorest performance across all the parameters evaluated (p < 0.05). Conclusion: Bioactive silica dentifrices significantly enhance enamel remineralization and protection against erosion-abrasion. The results highlight both the synergistic and independent roles of bioactive silica, supporting its application in daily oral care strategies for managing enamel wear. Clinical trial number: not applicable. Dental Enamel Toothpaste Fluoride Silica Tooth erosion Figures Figure 1 Figure 2 Figure 3 Background Dental erosion is a noncarious dental lesion characterized by the progressive loss of mineral content from the tooth surface due to acid exposure, in the absence of bacterial involvement 1,2 . Etiological factors can be classified as extrinsic, such as frequent consumption of acidic foods, beverages, or medications, and intrinsic, including conditions such as gastroesophageal reflux or eating disorders that expose teeth to gastric acids 3,4 . Acid-induced demineralization softens the enamel, increasing its susceptibility to mechanical wear, especially from toothbrushing 2 . Erosive tooth wear (ETW) is now recognized as a multifactorial condition, in which chemical, mechanical, and behavioral factors interact to accelerate the degradation of hard dental tissues 2,5 . If not diagnosed and managed in its early stages, ETW may lead to dentin exposure, hypersensitivity, loss of the occlusal vertical dimension, and compromised aesthetics 6,7 . To mitigate ETW, fluoride-based strategies have been widely adopted. Monovalent fluoride, such as sodium fluoride (NaF), promotes the formation of a calcium fluoride-like (CaF₂) layer on the enamel surface 8,9 . This transient protective layer acts as a fluoride reservoir, releasing ions under acidic conditions 9,10 . However, this layer is highly soluble and easily removed by brushing and salivary flow, which limits its durability and effectiveness in highly erosive environments. In response to these limitations, novel dentifrice formulations have been developed following the principles of preventive and minimally invasive dentistry, aiming to increase enamel protection and promote remineralization 11,12 . Among these advancements, bioactive silica (SiO₂-based compounds) has emerged as a promising agent capable of enhancing remineralization dynamics 13 . These compounds facilitate the deposition of calcium and phosphate ions and support the formation of a new mineralized layer on demineralized enamel, thereby improving its resistance to acid challenges 14 . In clinical scenarios that require enamel repair, bioactive agents capable of inducing hydroxyapatite nucleation are particularly valuable owing to their increased integration with dental structures 13,15 . Notably, the combination of bioactive silica with fluoride may result in synergistic effects, resulting in improved surface stability and greater resistance to acid challenges 16 . Previous studies have investigated the combined effects of bioactive silica, sodium fluoride, and tetrasodium pyrophosphate on the recovery of eroded enamel via pH cycling models 14,16–17 . These investigations revealed that dentifrice formulations containing both bioactive silica and fluoride, particularly in acidified environments, were more effective than fluoride alone in restoring enamel surface hardness and promoting structural repair. Such formulations were specifically designed to stimulate the formation of fluoride-enriched hydroxyapatite layers, often described as "enamel-like" structures 14 . These biomimetic layers exhibit increased resistance to acid dissolution and support deeper enamel remineralization, thereby contributing to a more resilient and durable protective effect 16–17 . On the basis of these premises, the present in vitro study aimed to evaluate the efficacy of bioactive silica-containing dentifrices, with or without different concentrations of fluoride, in repairing eroded enamel subjected to erosion–abrasion cycles. The null hypothesis tested was that the incorporation of bioactive silica, regardless of fluoride presence or concentration, would not result in statistically significant differences in (1) enamel surface hardness recovery, (2) post treatment mineral uptake, or (3) reduction in enamel surface loss compared with fluoride- and silica-free placebo dentifrice. Methods Sample preparation Freshly extracted bovine incisors were stored in a 0.08% thymol solution until use. These teeth were obtained from a certified slaughterhouse as post-mortem by-products, and no animals were sacrificed for research purposes. The use of animal-derived tissues followed institutional guidelines and international ethical principles. The sample size calculation was based on a previous study 18 that reported a large effect size (Cohen’s d = 1.29), with parameters set to achieve 80% statistical power and a 5% significance level, yielding a minimum of nine samples per group. To increase statistical confidence and compensate for potential specimen loss, 12 enamel blocks were prepared for each group. Standardized enamel blocks (4 × 4 × 2 mm) were obtained from the labial surface, embedded in acrylic resin, and polished with silicon carbide papers (grit 600 to 1500) under continuous water irrigation. Final polishing was performed with a 1 µm diamond paste. The baseline surface microhardness (SH₀) was measured via a Vickers microhardness tester (Shimadzu HMV—AD Easy Test, Version 3.0) with five indentations per sample (50 g load, 10 s dwell time, 100 µm spacing). Only the samples with initial hardness values of 380 ± 10 VHN were included. Each block was divided into three distinct regions: (1) the control area (sound enamel), (2) the eroded area (acid-induced lesion), and (3) the treated area (eroded enamel subjected to dentifrice treatment). Acid-resistant nail varnish (Risqué®, Niasi, Taboão da Serra, SP, Brazil) was applied in two layers to isolate the control area before lesion formation and the eroded area afterward (Fig. 1 ). Lesion formation Enamel erosion lesions were induced by immersing the samples in a 0.1% citric acid solution (pH 2.5) for 30 minutes at room temperature (28°C), with continuous agitation at 60 rpm. The acid solution (30 mL/specimen) was replaced every 5 minutes. Following lesion formation, surface microhardness was reassessed in the eroded region (SH₁) via the same parameters described previously 17 . Experimental groups and slurry Preparation Five dentifrices were tested, as described in Table 1 . Products were coded and stored by an independent researcher to maintain blinding during treatment and data analysis. Dentifrice slurries were freshly prepared daily by mixing each formulation with deionized water at a 1:3 ratio (w/w) and homogenized under constant agitation for 4 minutes prior to use. Table 1 Composition and manufacturer information of the dentifrice formulations evaluated in this study. Products (Groups) Active Ingredients* Manufacturer Sensitive Regenerator (RGS 1 ) Si-dentifrice with 1450 ppm sodium fluoride (REFIX® Technology). Rabbit Corp, Londrina, PR, Brasil (Lot number: 73045) Sensitive Regenerator (RGS 2 ) Si-dentifrice with 1110 ppm sodium fluoride (REFIX® Technology). Rabbit Corp, Londrina, PR, Brasil (Lot number: 020/2023) Sensitive Regenerator (RGS 3 ) Si-dentifrice with no Fluoride (REFIX® Technology). Rabbit Corp, Londrina, PR, Brasil (Lot number: 083/2023) Negative Control (NC) Fluoride-free dentifrice Rabbit Corp, Londrina, PR, Brasil (Lot number: 74071) Positive Control (PC) 1100 ppm sodium fluoride Rabbit Corp, Londrina, PR, Brasil (Lot number: 07802021) *Manufacturer information: all products provided by Rabbit Corp, Londrina, PR, Brazil. pH cycling and erosion-abrasion protocol pH cycling and erosion-abrasion protocol Prior to the initiation of pH cycling, the samples were immersed in a remineralizing solution for 24 hours. The experimental model then simulated daily erosive and abrasive challenges over a 5-day period at 37°C, following a protocol adapted from Simões et al. ( 2020 ) 18 . Each day, before and after the erosive challenge, the samples were stored in artificial saliva (0.2 mM glucose, 9.9 mM NaCl, 1.5 mM CaCl₂·2H₂O, 3 mM NH₄Cl, 17 mM KCl, 2 mM NaSCN, 2.4 mM K₂HPO₄, 3.3 mM urea, 2.4 mM NaH₂PO₄, and 11 µM ascorbic acid, pH 6.8), as described by Magalhães et al. ( 2008 ) 19 . The erosive challenge consisted of immersing each sample in 0.1% citric acid (pH 2.5) for 90 s three times per day under gentle agitation. After each cycle, the samples were rinsed with deionized water (10 s) and stored in artificial saliva (30 mL/specimen, pH 6.8, 25°C) for two hours between challenges. Following the first and last erosive challenges each day, abrasion was simulated via an automated brushing machine (MEV 3T-8XY, Odeme, Joaçaba, Brazil). Each brushing session involved 10 seconds of active brushing with 30 mL of dentifrice slurry, followed by 110 seconds of exposure to the dentifrice, totaling 2 minutes of treatment. The machine applied 11 zigzag vertical strokes (20 mm amplitude) under a 150 g axial load at 37°C. All the solutions were freshly prepared daily, and the samples were kept in artificial saliva overnight after the final session. Surface Microhardness Measurement The surface microhardness was assessed at three time points, namely, baseline (SH₀), post-erosion (SH₁), and post-treatment (SH₂), via a Vickers indenter with a 100 g load and a 10-second dwell time at five evenly spaced points (100 µm apart). The percentage of surface microhardness recovery (%SMHR) was calculated as follows: \(\:\%SMHR=100\times\:\frac{(SH2-SH1)}{(SH0-SH1)}\) 17 . Quantitative light-induced fluorescence (QLF) analysis Mineral changes were assessed via quantitative light-induced fluorescence (QLF) imaging (Qraycam Pro, Inspektor Research Systems BV, Amsterdam, Netherlands). Prior to image acquisition, the nail varnish was carefully removed via acetone-soaked cotton swabs, followed by rinsing with deionized water and air drying. A standardized imaging setup was used to ensure consistent positioning and lighting conditions. All the images were captured in a dark room, with the exposure and contrast settings set to zero and a fixed distance of 8 cm maintained between the device and the sample. The fluorescence data were analyzed via Q-ray software (version 1.38, Inspektor Research Systems BV, Amsterdam, Netherlands), which quantifies changes in mineral content on the basis of fluorescence loss values (ΔF). Two measurement stages were performed: ΔF₀, representing the fluorescence loss between sound and eroded enamel; and ΔF₁, representing the fluorescence loss between sound enamel and eroded enamel after treatment with dentifrices. The fluorescence recovery (%ΔFR) was calculated as the percentage change between posttreatment (ΔF₁) and pretreatment (ΔF₀) fluorescence loss, via the following formula: %ΔFR = [(ΔF₁ − ΔF₀) / ΔF₀] × 100, where positive values indicate mineral gain, and negative values indicate continued mineral loss 14 . Surface Profilometry Analysis The surface topography was evaluated via a noncontact 3D optical profilometer (Talysurf CCI MP, Leicester, UK). The system used the following parameters: 20x magnification, a field of view of 0.86 × 0.86 mm², "XY" reading mode with a resolution of 1024 × 1024 px, low-reflectance rough samples (level 4), a 0.25 mm cut off, and a standard Gaussian filter (ISO 16610-61). The surface roughness (Ra) was measured at three time points: Ra₀ (sound enamel), Ra₁ (after erosion), and Ra₂ (after treatment). The change in roughness (ΔRa) was calculated as ΔRa = Ra₂ − Ra₁, where negative values indicate a reduction in surface roughness following treatment (i.e., surface smoothing). Surface loss (SL) was calculated on the basis of vertical step differences between adjacent regions: SL₀ (sound vs. eroded), SL₁ (sound vs. treated). The variation in surface loss (ΔSL) was determined as ΔSL = SL₁ - SL₀, where higher values indicate greater tissue loss. The measurements were averaged from three predefined lines at 25%, 50%, and 75% of each sample. Three-dimensional surface maps were generated for qualitative analysis. Statistical analysis The data were analyzed via SPSS software (version 21.0, SPSS Inc., Chicago, IL, USA). The Shapiro–Wilk and Levene tests verified normality and homogeneity of variances, respectively. As both assumptions were met, no data transformation was necessary. One-way ANOVA followed by Tukey’s post hoc test was used to compare intergroup differences in SH, %SMHR, ΔF, and SL. Repeated-measures ANOVA was applied for intragroup comparisons (SH₀–SH₂ and Ra₀–Ra₂), with prior verification of sphericity. Statistical significance was set at α = 0.05. Results Surface Microhardness Table 2 presents the mean values and standard deviations of enamel surface microhardness at baseline (SH₀), after erosion (SH₁), and after treatment (SH₂), for each experimental group. No significant differences were found for SH₀ or SH₁ (ANOVA, p > 0.05), confirming initial homogeneity and successful lesion formation across all groups. After treatment (SH₂), significant differences were observed between groups (ANOVA, p 0.05). Intragroup comparisons revealed significant differences between the SH₀–SH₁ and SH₁–SH₂ groups (repeated-measures ANOVA, p < 0.05), indicating effective lesion formation followed by post-treatment changes across all groups. The RGS2 group (bioactive silica + 1100 ppm fluoride) achieved the highest percentage of surface microhardness recovery (%SMHR), with a 23% increase compared with that of PC (p RGS1 > RGS3. No significant differences were detected between PC and RGS1 or RGS3 (p > 0.05). The NC group presented the lowest %SMHR values. Table 2 Mean (± SD) enamel surface microhardness at baseline (SH₀), after erosion (SH₁), and after treatment (SH₂), and recovery (%SMHR) across experimental groups. Different lowercase letters within a column indicate statistically significant differences between groups at the same time point (p < 0.05). Different uppercase letters within a row indicate statistically significant differences across time points within the same group (p < 0.05).* Group SH 0 SH 1 SH 2 %SMHR RGS 1 388.2 (6.4) a,A 190.3 (3.8) a,B 308.9 (5.4) b,C 59.9 (2.6) b RGS 2 390 (6.6) a,A 193.4 (7.3) a,B 334.2 (13.2) c,C 71.7 (6.0) c RGS 3 387.6 (5.2) a,A 190.7 (6.7) a,B 291.5 (17.9) d,C 51.2 (9.3) d NC 391.2 (7.8) a,A 193 (7.4) a,B 210.9 (14) a,C 8.9 (8.9) a PC 389.6 (7.8) a,A 192 (6.5) a,B 306.8 (10.3) b,C 58.1 (5.7) b,d *ANOVA with Tukey’s post hoc for intergroup comparisons; repeated-measures ANOVA for intragroup comparisons. Quantitative light-induced fluorescence (QLF) analysis Table 3 summarizes the mean fluorescence loss values before and after treatment. No significant differences were found between groups at ΔF₀ (p > 0.05), demonstrating standardized lesion severity prior to treatment. After treatment (ΔF₁), significant differences were observed among the groups (ANOVA, p < 0.001). The groups treated with bioactive silica-containing dentifrices (RGS1, RGS2, RGS3) exhibited significantly greater fluorescence recovery (~ 52%) than the PC (~ 15%) and NC (which showed continued mineral loss) groups did. No significant differences were found among RGS1, RGS2, and RGS3 (p > 0.05). The fluorescence recovery (%ΔFR) followed a similar trend, with the bioactive silica groups showing the highest values (p < 0.05). The NC group was the only one that presented a negative ΔFR, indicating ongoing demineralization. Table 3 Mean (± SD) quantitative light-induced fluorescence values before (ΔF₀) and after treatment (ΔF₁), and fluorescence recovery (%ΔFR). Different lowercase letters indicate statistically significant differences between groups (p < 0.05).* Group ΔF 0 ΔF 1 %ΔFR RGS1 -12.6 (1.0) a -6.5 (0.5) c 47.9 (5.9) c RGS2 -12.7 (1.0) a -6.7 (0.6) c 46.5 (6.5) c RGS3 -13.0 (0.8) a -6.6 (0.5) c 48.6 (5.1) c NC -12.8 (1.0) a -14.7 (1.8) a, -13.0 (3.1) a PC -12.5 (0.8) a -10.6 (0.7) b 14.7 (2.9) b *ANOVA with Tukey’s post hoc for intergroup comparisons Surface Roughness (Ra), Surface Loss (SL), and ΔSL Analysis Table 4 presents the mean surface roughness (Ra) values under three conditions: sound enamel (Ra₀), after erosion (Ra₁), and posttreatment (Ra₂). No significant differences were found for Ra₀ or Ra₁ among the groups (p > 0.05), indicating consistency at baseline or in lesion formation. After treatment (Ra₂), the NC group presented the highest surface roughness (0.282 µm), which was significantly different from that of RGS2 (p < 0.05). The PC group presented intermediate values (0.210 µm), whereas RGS1 and RGS3 presented similar roughness levels, with no significant differences from PC or RGS2. With respect to ΔRa, all bioactive silica-treated groups (RGS1, RGS2, RGS3) presented negative values, indicating a reduction in surface roughness following treatment. RGS2 achieved the most pronounced smoothing effect (ΔRa = − 0.149 µm) and was significantly superior to PC (–0.055 µm) and NC (+ 0.056 µm) (p < 0.05). The positive ΔRa observed in the NC group reflects a worsening of surface roughness after treatment. Table 4 Mean (± SD) enamel surface roughness at baseline (Ra₀, sound enamel), after erosion (Ra₁), and after treatment (Ra₂), and roughness change (ΔRa, µm) across experimental groups. Different lowercase letters within a column indicate statistically significant differences between groups at the same time point (p < 0.05). Different uppercase letters within a row indicate statistically significant differences across time points within the same group (p < 0.05).* Group Ra 0 Ra 1 Ra 2 ΔRa RGS1 0.034 (0.022) a,A 0.234 (0.064) a,B 0.159 (0.037) b,c,C –0.075 (0.033) b RGS2 0.019 (0.008) a,A 0.275 (0.068) a,B 0.126 (0.044) c,C –0.149 (0.024) c RGS3 0.029 (0.017) a,A 0.254 (0.043) a,B 0.150 (0.045) b,c,C –0.104 (0.032) c NC 0.019 (0.009) a,A 0.226 (0.069) a,B 0.282 (0.062) a,B + 0.056 (0.046) a PC 0.021 (0.006) a,A 0.265 (0.061) a,B 0.210 (0.055) b,B -0.055 (0.041) b *ANOVA with Tukey’s post hoc for intergroup comparisons; repeated-measures ANOVA for intragroup comparisons. Figure 2 shows the enamel surface loss before and after treatment. SL₀ values (sound vs eroded) did not differ significantly among the groups (p > 0.05), confirming standardization of lesion depth. After treatment (SL₁), the NC group preented the greatest surface loss, which was significantly greater than that of all the other groups (p < 0.05). RGS2 displayed the lowest SL₁ value, whereas RGS1, RGS3, and PC achieved intermediate performance, with no significant differences among them. Compared with those in the PC and NC groups, the bioactive silica groups (RGS1, RGS2, RGS3) in the ΔSL group demonstrated superior preservation of the enamel structure. Qualitative surface topography Three-dimensional surface analysis (Fig. 3 ) revealed distinct topographic patterns among the groups, as represented by color-coded maps (orange = least surface loss; dark blue = greatest loss). RGS2 displayed the most favorable surface profile, with a predominance of green and light blue areas, indicating mild to moderate wear and well-preserved enamel contours. RGS1 exhibited a broader range of colors, from orange in preserved regions to light blue in worn areas, reflecting moderate wear. RGS3, although fluoride-free, presented a similar pattern to that of RGS1 but with a slightly more pronounced wear depth, as evidenced by larger dark blue regions. In contrast, the NC group (negative control) revealed extensive dark blue regions, indicating severe structural loss and the poorest topographical outcome. The PC group (positive control) presented predominantly light blue surfaces, which is consistent with moderate wear. However, compared with RGS2, PC provided less preservation of the enamel surface, reinforcing the superior protective effect of the bioactive silica formulation containing 1100 ppm fluoride. Discussion The results of the present study support the rejection of all three null hypotheses, as the incorporation of bioactive silica, particularly in association with fluoride, significantly improved enamel surface properties. These findings confirm the multifactorial benefits of bioactive silica dentifrices in enhancing microhardness, reducing mineral loss, and improving surface smoothness, which are critical for mitigating the effects of erosive-abrasive wear 17,20 . Compared with both conventional fluoride dentifrices and placebo formulations, bioactive silica dentifrices demonstrated superior performance. In particular, RGS2, containing 1100 ppm F⁻, achieved the highest values of %SMHR and %ΔFR, as well as the lowest ΔSL and ΔRa values, indicating greater enamel recovery and structural preservation. These results suggest that an optimized concentration of fluoride in combination with bioactive silica may provide the most favorable conditions for enamel repair in erosive-abrasive scenarios 21,22 . The significantly higher %ΔFR observed in RGS2 confirms its effectiveness in promoting mineral redeposition and mitigating early enamel demineralization, as fluorescence changes have been correlated with subsurface mineral recovery 14,22 . Although RGS1 (1450 ppm F⁻) also improved surface microhardness and fluorescence recovery, its outcomes were inferior to those of RGS2. This suggests that excessively high fluoride concentrations may not necessarily lead to superior protective effects when used in combination with bioactive silica, possibly due to less effective interactions between fluoride and the silica matrix under certain physicochemical conditions 14,17 . Interestingly, the results for RGS3, a fluoride-free formulation, also demonstrated significant improvements in %SMHR and %ΔFR compared with the NC. This finding reinforces the hypothesis that silica exerts a fluoride-independent remineralization effect. Silicate ions may directly promote apatite nucleation and stabilize amorphous calcium phosphate, facilitating mineral deposition even in the absence of fluoride 15,18,19 . In this context, the incorporation of bioactive silica has emerged as a promising strategy to overcome the limitations of traditional fluoride therapies. Silica plays a critical role in enamel remineralization by releasing bioactive ions in a controlled and sustained manner. Upon contact with saliva, bioactive silicates hydrate and partially dissolve, releasing fluoride (F⁻), calcium (Ca²⁺), phosphate (PO₄³⁻), and silicate (SiO₄⁴⁻) ions in response to the needs of the oral environment 11,23,24 . These ions promote the formation of a new mineralized layer via apatite nucleation, favoring tissue recovery and structural integrity 13,14,15 . Fluoride contributes to enamel remineralization by forming a superficial calcium fluoride-like (CaF₂) layer, which functions as a transient ion reservoir under acidic conditions 9,10,25–27 . However, in highly erosive environments, this layer is rapidly dissolved or mechanically removed by brushing or salivary flow, limiting its protective capacity 21,22,28 . In addition, the inclusion of calcium and phosphate in dentifrices may have limited remineralizing effects when these ions interact prematurely with fluoride, hindering effective deposition onto the enamel surface 29,30 . These limitations underscore the need for advanced formulations, such as those containing bioactive silica, which can modulate ion release and act independently of fluoride to sustain apatite nucleation and deeper mineral integration. Thus, silicon-based dentifrices are promising agents for enamel repair. The gradual release of calcium and phosphate ions facilitates mineral deposition and formation of a new mineralized layer, which integrates into the existing enamel matrix 13 . Previous studies have suggested that silica induces apatite nucleation on the enamel surface, leading to deeper and more stable remineralization 14,16,17,31 . From a mechanistic perspective, silicate ions (SiO₄⁴⁻) partially replace phosphate groups at the B-sites of hydroxyapatite crystals, resulting in the formation of a silicon-enriched apatite structure. In contrast, fluoride ions substitute for hydroxyl groups at the A-sites, forming fluorapatite 13,23 . While fluorapatite enhances the chemical stability of enamel, silicon contributes to biological integration by facilitating the localized deposition of calcium and phosphate in areas of mineral loss 13,17,32–34 . This distinction in their modes of incorporation—fluoride at A-sites and silicon at B-sites—highlights their complementary roles. When combined, fluoride and silica act on different nucleation sites of hydroxyapatite, producing a synergistic effect that enhances enamel remineralization and increases resistance to acid dissolution 13,17,31 . Moreover, the combination of bioactive silica with fluoride can produce synergistic effects, resulting in improved surface stability 16 . Previous studies have investigated the combined effects of silicon, sodium fluoride, and tetrasodium pyrophosphate on the recovery of eroded enamel via pH cycling models 14,16,17 . The results demonstrated that dentifrice formulations containing both silicon and fluoride, especially in an acidified environment, were more effective at restoring enamel hardness and promoting surface restructuring than fluoride alone 17,31 . These formulations were specifically developed to stimulate the formation of fluoride-enriched hydroxyapatite layers, often referred to as “enamel-like” structures 16 . These layers exhibit enhanced resistance to acid dissolution and support deeper enamel remineralization, contributing to more resilient and long-lasting protection 13,29,31 . Conversely, the positive control (PC), containing fluoride alone, significantly increased surface microhardness and improved the surface characteristics 35–37 . These effects align with the ability of fluoride to form fluorapatite, which enhances the chemical stability of enamel but may not penetrate deeply into demineralized areas 25,26,38 . The benefits of fluoride are therefore more restricted to surface-level changes, which may limit the effectiveness of fluoride-only formulations in managing progressive mineral loss 25,26 . Profilometric analysis provided complementary evidence regarding enamel wear resistance. RGS2 presented the lowest ΔSL and ΔRa values, indicating better surface preservation and smoother morphology after treatment. This outcome is clinically relevant, as reduced surface roughness is associated with lower plaque retention, less bacterial colonization, and diminished susceptibility to acidic challenges 28,30 . RGS1 and PC demonstrated intermediate outcomes, reinforcing the role of both fluoride concentration and the presence of bioactive silica in surface preservation. Taken together, these findings indicate that bioactive silica, whether used alone or in combination with fluoride, contributes to the repair and protection of eroded enamel subjected to abrasion. The superior performance of RGS2 supports the development of multifunctional dentifrices capable of addressing both preventive and therapeutic needs in managing enamel erosion. The formulation strategy combining optimal fluoride levels with bioactive silica may represent a new benchmark in daily oral care products targeting high-risk patients for erosive tooth wear. Given its favorable performance and versatility, bioactive silica represents a clinically relevant strategy for the prevention and repair of early enamel erosion. Further in situ and clinical studies are encouraged to validate these in vitro results and to support the development of innovative commercial dentifrices that integrate bioactive silica into routine oral care. Conclusions This in vitro study demonstrated that dentifrices containing bioactive silica, especially when combined with 1100 ppm fluoride, were more effective at restoring enamel microhardness, promoting mineral gain, and reducing surface loss after erosion‒abrasion cycles. The superior performance of this formulation (RGS2) suggests a synergistic effect between fluoride and silica. Fluoride-free silica dentifrice (RGS3) also exhibited significant benefits, confirming the independent remineralizing potential of bioactive silica. These results support the development of innovative dentifrices combining silica and fluoride as promising strategies for preventing and repairing erosive enamel damage. Declarations Ethics approval and consent to participate: The study used bovine teeth obtained from a certified slaughterhouse as post-mortem by-products. No animals were euthanized for this research, and specific ethical approval was not required. Procedures complied with institutional and international standards for the ethical use of biological material. Clinical trial number: Not applicable. Consent for publication: Not applicable. Availability of data and materials: The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request. Competing interests: The authors declare that they have no competing interests. Funding: The authors received no specific funding for this work. Authors ’ contributions: Elizabeth Barreto Galvão Sousa, Anderson Gomes Forte, Ana Maria Barros Chaves Pereira, Andressa Feitosa Bezerra Oliveira, and Fábio Correia Sampaio contributed to the conception and experimental design. Elizabeth Barreto Galvão Sousa, Anderson Gomes Forte, Juliellen Luiz Cunha, Marcel Alves Avelino Paiva, Adriana Moreira Ferreira, and Vitória Régia Rolim Nunes performed the acquisition of data, sample preparation and laboratory procedures. Elizabeth Barreto Galvão Sousa, Anderson Gomes Forte, and Andressa Feitosa Bezerra Oliveira contributed to statistical analysis and interpretation of data. Ana Maria Barros Chaves Pereira, Fábio Correia Sampaio, and Andressa Feitosa Bezerra Oliveira supervised the study and critically reviewed the manuscript. All authors read and approved the final version of the manuscript. Acknowledgements: The authors thank the Federal University of Paraíba (UFPB) for providing laboratory facilities and technical support during the study. 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Braz Dent Sci. 2023;26(1):e3688. doi:10.4322/bds.2023.e3688 Alkattan R, Lippert F, Tang Q, Eckert GJ, Ando M. The influence of hardness and chemical composition on enamel demineralization and subsequent remineralization. J Dent. 2018;75:34-40. doi:10.1016/j.jdent.2018.05.002 Tanaka T, Kobayashi T, Tamenori Y, Sakanaka A, Kuriki T, Amano A. Phosphoryl oligosaccharides of calcium enhance mineral availability and fluorapatite formation. Arch Oral Biol. 2019;101:135-141. doi:10.1016/j.archoralbio.2019.03.018 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 09 Dec, 2025 Read the published version in BMC Oral Health → Version 1 posted Editorial decision: Revision requested 10 Oct, 2025 Reviews received at journal 10 Oct, 2025 Reviews received at journal 09 Oct, 2025 Reviewers agreed at journal 06 Oct, 2025 Reviewers agreed at journal 02 Oct, 2025 Reviewers invited by journal 29 Sep, 2025 Editor assigned by journal 29 Sep, 2025 Editor invited by journal 29 Sep, 2025 Submission checks completed at journal 28 Sep, 2025 First submitted to journal 28 Sep, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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(A) Enamel blocks embedded in acrylic resin and polished. (B) baseline surface microhardness (SH₀. (C) Protection of the sound reference area with acid-resistant nail varnish. (D) Induction of the erosive lesion: immersion in 0.1% citric acid (pH 2.5) for 30 min under gentle agitation. (E) Post-erosion surface microhardness (SH₁). (F) Protection of the eroded area to delimit the treatment window. (G) Five-day erosion–abrasion cycling at 37 °C: 3x daily erosive challenge (90 s each) + 2x daily brushing treatments (15 s + 45 s immersion in dentifrice slurry); (H) Post-treatment surface microhardness (SH₂).\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-7359328/v1/0c442d8f9e69e9e0aaf305c5.png"},{"id":93230477,"identity":"3c3a6632-b4a3-4f20-adf9-82c05c390223","added_by":"auto","created_at":"2025-10-10 13:07:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":184505,"visible":true,"origin":"","legend":"\u003cp\u003eMean surface loss (ΔSL, µm) of bovine enamel after erosive–abrasive challenges. Different lowercase letters indicate statistically significant differences between groups (p \u0026lt; 0.05).\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-7359328/v1/0ce49912cb392f49d3007bef.png"},{"id":93230478,"identity":"a90ec0d7-0201-4c30-9e01-de857c990d7d","added_by":"auto","created_at":"2025-10-10 13:07:06","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":962314,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative three-dimensional optical profilometry images of enamel surfaces from the experimental groups. Each panel shows three regions: (*) sound enamel; \u003cem\u003e(\u003c/em\u003e**) eroded enamel; and (***) enamel surface after erosive–abrasive treatment. Note that the vertical scale differs across groups: up to 30 µm for RGS1–RGS3 and PC, and up to 17 µm for NC.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-7359328/v1/7ad7969fc0c0ea50b61e9ff4.png"},{"id":98243500,"identity":"6568f333-25f6-414c-81cb-4ab2862c376c","added_by":"auto","created_at":"2025-12-15 16:07:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8423829,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7359328/v1/3d89bd48-0887-4e94-93eb-ef1d619df070.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Innovative dentifrices based on bioactive silica for enamel remineralization and erosion control: an in vitro study","fulltext":[{"header":"Background","content":"\u003cp\u003eDental erosion is a noncarious dental lesion characterized by the progressive loss of mineral content from the tooth surface due to acid exposure, in the absence of bacterial involvement\u003csup\u003e1,2\u003c/sup\u003e. Etiological factors can be classified as extrinsic, such as frequent consumption of acidic foods, beverages, or medications, and intrinsic, including conditions such as gastroesophageal reflux or eating disorders that expose teeth to gastric acids\u003csup\u003e3,4\u003c/sup\u003e. Acid-induced demineralization softens the enamel, increasing its susceptibility to mechanical wear, especially from toothbrushing\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eErosive tooth wear (ETW) is now recognized as a multifactorial condition, in which chemical, mechanical, and behavioral factors interact to accelerate the degradation of hard dental tissues\u003csup\u003e2,5\u003c/sup\u003e. If not diagnosed and managed in its early stages, ETW may lead to dentin exposure, hypersensitivity, loss of the occlusal vertical dimension, and compromised aesthetics\u003csup\u003e6,7\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eTo mitigate ETW, fluoride-based strategies have been widely adopted. Monovalent fluoride, such as sodium fluoride (NaF), promotes the formation of a calcium fluoride-like (CaF₂) layer on the enamel surface\u003csup\u003e8,9\u003c/sup\u003e. This transient protective layer acts as a fluoride reservoir, releasing ions under acidic conditions\u003csup\u003e9,10\u003c/sup\u003e. However, this layer is highly soluble and easily removed by brushing and salivary flow, which limits its durability and effectiveness in highly erosive environments.\u003c/p\u003e\u003cp\u003eIn response to these limitations, novel dentifrice formulations have been developed following the principles of preventive and minimally invasive dentistry, aiming to increase enamel protection and promote remineralization\u003csup\u003e11,12\u003c/sup\u003e. Among these advancements, bioactive silica (SiO₂-based compounds) has emerged as a promising agent capable of enhancing remineralization dynamics\u003csup\u003e13\u003c/sup\u003e. These compounds facilitate the deposition of calcium and phosphate ions and support the formation of a new mineralized layer on demineralized enamel, thereby improving its resistance to acid challenges\u003csup\u003e14\u003c/sup\u003e. In clinical scenarios that require enamel repair, bioactive agents capable of inducing hydroxyapatite nucleation are particularly valuable owing to their increased integration with dental structures\u003csup\u003e13,15\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eNotably, the combination of bioactive silica with fluoride may result in synergistic effects, resulting in improved surface stability and greater resistance to acid challenges\u003csup\u003e16\u003c/sup\u003e. Previous studies have investigated the combined effects of bioactive silica, sodium fluoride, and tetrasodium pyrophosphate on the recovery of eroded enamel via pH cycling models\u003csup\u003e14,16\u0026ndash;17\u003c/sup\u003e. These investigations revealed that dentifrice formulations containing both bioactive silica and fluoride, particularly in acidified environments, were more effective than fluoride alone in restoring enamel surface hardness and promoting structural repair. Such formulations were specifically designed to stimulate the formation of fluoride-enriched hydroxyapatite layers, often described as \"enamel-like\" structures\u003csup\u003e14\u003c/sup\u003e. These biomimetic layers exhibit increased resistance to acid dissolution and support deeper enamel remineralization, thereby contributing to a more resilient and durable protective effect\u003csup\u003e16\u0026ndash;17\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eOn the basis of these premises, the present in vitro study aimed to evaluate the efficacy of bioactive silica-containing dentifrices, with or without different concentrations of fluoride, in repairing eroded enamel subjected to erosion\u0026ndash;abrasion cycles. The null hypothesis tested was that the incorporation of bioactive silica, regardless of fluoride presence or concentration, would not result in statistically significant differences in (1) enamel surface hardness recovery, (2) post treatment mineral uptake, or (3) reduction in enamel surface loss compared with fluoride- and silica-free placebo dentifrice.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eSample preparation\u003c/h2\u003e\u003cp\u003eFreshly extracted bovine incisors were stored in a 0.08% thymol solution until use. These teeth were obtained from a certified slaughterhouse as post-mortem by-products, and no animals were sacrificed for research purposes. The use of animal-derived tissues followed institutional guidelines and international ethical principles. The sample size calculation was based on a previous study\u003csup\u003e18\u003c/sup\u003e that reported a large effect size (Cohen\u0026rsquo;s d\u0026thinsp;=\u0026thinsp;1.29), with parameters set to achieve 80% statistical power and a 5% significance level, yielding a minimum of nine samples per group. To increase statistical confidence and compensate for potential specimen loss, 12 enamel blocks were prepared for each group.\u003c/p\u003e\u003cp\u003eStandardized enamel blocks (4 \u0026times; 4 \u0026times; 2 mm) were obtained from the labial surface, embedded in acrylic resin, and polished with silicon carbide papers (grit 600 to 1500) under continuous water irrigation. Final polishing was performed with a 1 \u0026micro;m diamond paste. The baseline surface microhardness (SH₀) was measured via a Vickers microhardness tester (Shimadzu HMV\u0026mdash;AD Easy Test, Version 3.0) with five indentations per sample (50 g load, 10 s dwell time, 100 \u0026micro;m spacing). Only the samples with initial hardness values of 380\u0026thinsp;\u0026plusmn;\u0026thinsp;10 VHN were included.\u003c/p\u003e\u003cp\u003eEach block was divided into three distinct regions: (1) the control area (sound enamel), (2) the eroded area (acid-induced lesion), and (3) the treated area (eroded enamel subjected to dentifrice treatment). Acid-resistant nail varnish (Risqu\u0026eacute;\u0026reg;, Niasi, Tabo\u0026atilde;o da Serra, SP, Brazil) was applied in two layers to isolate the control area before lesion formation and the eroded area afterward (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eLesion formation\u003c/h3\u003e\n\u003cp\u003eEnamel erosion lesions were induced by immersing the samples in a 0.1% citric acid solution (pH 2.5) for 30 minutes at room temperature (28\u0026deg;C), with continuous agitation at 60 rpm. The acid solution (30 mL/specimen) was replaced every 5 minutes. Following lesion formation, surface microhardness was reassessed in the eroded region (SH₁) via the same parameters described previously\u003csup\u003e17\u003c/sup\u003e.\u003c/p\u003e\n\u003ch3\u003eExperimental groups and slurry Preparation\u003c/h3\u003e\n\u003cp\u003eFive dentifrices were tested, as described in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Products were coded and stored by an independent researcher to maintain blinding during treatment and data analysis. Dentifrice slurries were freshly prepared daily by mixing each formulation with deionized water at a 1:3 ratio (w/w) and homogenized under constant agitation for 4 minutes prior to use.\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\u003eComposition and manufacturer information of the dentifrice formulations evaluated in this study.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProducts (Groups)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eActive Ingredients*\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eManufacturer\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSensitive Regenerator (RGS\u003csub\u003e1\u003c/sub\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSi-dentifrice with 1450 ppm sodium fluoride (REFIX\u0026reg; Technology).\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRabbit Corp, Londrina, PR, Brasil (Lot number: 73045)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSensitive Regenerator (RGS\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSi-dentifrice with 1110 ppm sodium fluoride (REFIX\u0026reg; Technology).\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRabbit Corp, Londrina, PR, Brasil (Lot number: 020/2023)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSensitive Regenerator (RGS\u003csub\u003e3\u003c/sub\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSi-dentifrice with no Fluoride (REFIX\u0026reg; Technology).\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRabbit Corp, Londrina, PR, Brasil (Lot number: 083/2023)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNegative Control (NC)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFluoride-free dentifrice\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRabbit Corp, Londrina, PR, Brasil (Lot number: 74071)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePositive Control (PC)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1100 ppm sodium fluoride\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRabbit Corp, Londrina, PR, Brasil (Lot number: 07802021)\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*Manufacturer information: all products provided by Rabbit Corp, Londrina, PR, Brazil.\u003c/p\u003e\n\u003ch3\u003epH cycling and erosion-abrasion protocol\u003c/h3\u003e\n\u003cdiv class=\"Heading\"\u003epH cycling and erosion-abrasion protocol\u003c/div\u003e\u003cp\u003ePrior to the initiation of pH cycling, the samples were immersed in a remineralizing solution for 24 hours. The experimental model then simulated daily erosive and abrasive challenges over a 5-day period at 37\u0026deg;C, following a protocol adapted from Sim\u0026otilde;es et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003csup\u003e18\u003c/sup\u003e. Each day, before and after the erosive challenge, the samples were stored in artificial saliva (0.2 mM glucose, 9.9 mM NaCl, 1.5 mM CaCl₂\u0026middot;2H₂O, 3 mM NH₄Cl, 17 mM KCl, 2 mM NaSCN, 2.4 mM K₂HPO₄, 3.3 mM urea, 2.4 mM NaH₂PO₄, and 11 \u0026micro;M ascorbic acid, pH 6.8), as described by Magalh\u0026atilde;es et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2008\u003c/span\u003e)\u003csup\u003e19\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe erosive challenge consisted of immersing each sample in 0.1% citric acid (pH 2.5) for 90 s three times per day under gentle agitation. After each cycle, the samples were rinsed with deionized water (10 s) and stored in artificial saliva (30 mL/specimen, pH 6.8, 25\u0026deg;C) for two hours between challenges.\u003c/p\u003e\u003cp\u003eFollowing the first and last erosive challenges each day, abrasion was simulated via an automated brushing machine (MEV 3T-8XY, Odeme, Joa\u0026ccedil;aba, Brazil). Each brushing session involved 10 seconds of active brushing with 30 mL of dentifrice slurry, followed by 110 seconds of exposure to the dentifrice, totaling 2 minutes of treatment. The machine applied 11 zigzag vertical strokes (20 mm amplitude) under a 150 g axial load at 37\u0026deg;C. All the solutions were freshly prepared daily, and the samples were kept in artificial saliva overnight after the final session.\u003c/p\u003e\n\u003ch3\u003eSurface Microhardness Measurement\u003c/h3\u003e\n\u003cp\u003eThe surface microhardness was assessed at three time points, namely, baseline (SH₀), post-erosion (SH₁), and post-treatment (SH₂), via a Vickers indenter with a 100 g load and a 10-second dwell time at five evenly spaced points (100 \u0026micro;m apart). The percentage of surface microhardness recovery (%SMHR) was calculated as follows: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\%SMHR=100\\times\\:\\frac{(SH2-SH1)}{(SH0-SH1)}\\)\u003c/span\u003e\u003c/span\u003e\u003csup\u003e17\u003c/sup\u003e.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eQuantitative light-induced fluorescence (QLF) analysis\u003c/h2\u003e\u003cp\u003eMineral changes were assessed via quantitative light-induced fluorescence (QLF) imaging (Qraycam Pro, Inspektor Research Systems BV, Amsterdam, Netherlands). Prior to image acquisition, the nail varnish was carefully removed via acetone-soaked cotton swabs, followed by rinsing with deionized water and air drying.\u003c/p\u003e\u003cp\u003eA standardized imaging setup was used to ensure consistent positioning and lighting conditions. All the images were captured in a dark room, with the exposure and contrast settings set to zero and a fixed distance of 8 cm maintained between the device and the sample. The fluorescence data were analyzed via Q-ray software (version 1.38, Inspektor Research Systems BV, Amsterdam, Netherlands), which quantifies changes in mineral content on the basis of fluorescence loss values (ΔF).\u003c/p\u003e\u003cp\u003eTwo measurement stages were performed: ΔF₀, representing the fluorescence loss between sound and eroded enamel; and ΔF₁, representing the fluorescence loss between sound enamel and eroded enamel after treatment with dentifrices. The fluorescence recovery (%ΔFR) was calculated as the percentage change between posttreatment (ΔF₁) and pretreatment (ΔF₀) fluorescence loss, via the following formula: %ΔFR = [(ΔF₁ \u0026minus; ΔF₀) / ΔF₀] \u0026times; 100, where positive values indicate mineral gain, and negative values indicate continued mineral loss\u003csup\u003e14\u003c/sup\u003e.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eSurface Profilometry Analysis\u003c/h3\u003e\n\u003cp\u003eThe surface topography was evaluated via a noncontact 3D optical profilometer (Talysurf CCI MP, Leicester, UK). The system used the following parameters: 20x magnification, a field of view of 0.86 \u0026times; 0.86 mm\u0026sup2;, \"XY\" reading mode with a resolution of 1024 \u0026times; 1024 px, low-reflectance rough samples (level 4), a 0.25 mm cut off, and a standard Gaussian filter (ISO 16610-61).\u003c/p\u003e\u003cp\u003eThe surface roughness (Ra) was measured at three time points: Ra₀ (sound enamel), Ra₁ (after erosion), and Ra₂ (after treatment). The change in roughness (ΔRa) was calculated as ΔRa\u0026thinsp;=\u0026thinsp;Ra₂ \u0026minus; Ra₁, where negative values indicate a reduction in surface roughness following treatment (i.e., surface smoothing). Surface loss (SL) was calculated on the basis of vertical step differences between adjacent regions: SL₀ (sound vs. eroded), SL₁ (sound vs. treated). The variation in surface loss (ΔSL) was determined as ΔSL\u0026thinsp;=\u0026thinsp;SL₁ - SL₀, where higher values indicate greater tissue loss. The measurements were averaged from three predefined lines at 25%, 50%, and 75% of each sample. Three-dimensional surface maps were generated for qualitative analysis.\u003c/p\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eThe data were analyzed via SPSS software (version 21.0, SPSS Inc., Chicago, IL, USA). The Shapiro\u0026ndash;Wilk and Levene tests verified normality and homogeneity of variances, respectively. As both assumptions were met, no data transformation was necessary.\u003c/p\u003e\u003cp\u003eOne-way ANOVA followed by Tukey\u0026rsquo;s post hoc test was used to compare intergroup differences in SH, %SMHR, ΔF, and SL. Repeated-measures ANOVA was applied for intragroup comparisons (SH₀\u0026ndash;SH₂ and Ra₀\u0026ndash;Ra₂), with prior verification of sphericity. Statistical significance was set at α\u0026thinsp;=\u0026thinsp;0.05.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eSurface Microhardness\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents the mean values and standard deviations of enamel surface microhardness at baseline (SH₀), after erosion (SH₁), and after treatment (SH₂), for each experimental group. No significant differences were found for SH₀ or SH₁ (ANOVA, p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), confirming initial homogeneity and successful lesion formation across all groups. After treatment (SH₂), significant differences were observed between groups (ANOVA, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), except between RGS1 and PC (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Intragroup comparisons revealed significant differences between the SH₀\u0026ndash;SH₁ and SH₁\u0026ndash;SH₂ groups (repeated-measures ANOVA, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), indicating effective lesion formation followed by post-treatment changes across all groups.\u003c/p\u003e\u003cp\u003eThe RGS2 group (bioactive silica\u0026thinsp;+\u0026thinsp;1100 ppm fluoride) achieved the highest percentage of surface microhardness recovery (%SMHR), with a 23% increase compared with that of PC (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Among the REFIX-containing groups, the %SMHR followed the trend: RGS2\u0026thinsp;\u0026gt;\u0026thinsp;RGS1\u0026thinsp;\u0026gt;\u0026thinsp;RGS3. No significant differences were detected between PC and RGS1 or RGS3 (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The NC group presented the lowest %SMHR values.\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\u003eMean (\u0026plusmn;\u0026thinsp;SD) enamel surface microhardness at baseline (SH₀), after erosion (SH₁), and after treatment (SH₂), and recovery (%SMHR) across experimental groups. Different lowercase letters within a column indicate statistically significant differences between groups at the same time point (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Different uppercase letters within a row indicate statistically significant differences across time points within the same group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).*\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSH\u003csub\u003e0\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSH\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eSH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e%SMHR\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRGS\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e388.2 (6.4) \u003csup\u003ea,A\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e190.3 (3.8) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e308.9 (5.4) \u003csup\u003eb,C\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e59.9 (2.6) \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRGS\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e390 (6.6) \u003csup\u003ea,A\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e193.4 (7.3) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e334.2 (13.2) \u003csup\u003ec,C\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e71.7 (6.0) \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRGS\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e387.6 (5.2) \u003csup\u003ea,A\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e190.7 (6.7) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e291.5 (17.9) \u003csup\u003ed,C\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e51.2 (9.3) \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e391.2 (7.8) \u003csup\u003ea,A\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e193 (7.4) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e210.9 (14) \u003csup\u003ea,C\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e8.9 (8.9) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e389.6 (7.8) \u003csup\u003ea,A\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e192 (6.5) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e306.8 (10.3) \u003csup\u003eb,C\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e58.1 (5.7) \u003csup\u003eb,d\u003c/sup\u003e\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*ANOVA with Tukey\u0026rsquo;s post hoc for intergroup comparisons; repeated-measures ANOVA for intragroup comparisons.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003eQuantitative light-induced fluorescence (QLF) analysis\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e summarizes the mean fluorescence loss values before and after treatment. No significant differences were found between groups at ΔF₀ (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), demonstrating standardized lesion severity prior to treatment.\u003c/p\u003e\u003cp\u003eAfter treatment (ΔF₁), significant differences were observed among the groups (ANOVA, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The groups treated with bioactive silica-containing dentifrices (RGS1, RGS2, RGS3) exhibited significantly greater fluorescence recovery (~\u0026thinsp;52%) than the PC (~\u0026thinsp;15%) and NC (which showed continued mineral loss) groups did. No significant differences were found among RGS1, RGS2, and RGS3 (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003eThe fluorescence recovery (%ΔFR) followed a similar trend, with the bioactive silica groups showing the highest values (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The NC group was the only one that presented a negative ΔFR, indicating ongoing demineralization.\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 (\u0026plusmn;\u0026thinsp;SD) quantitative light-induced fluorescence values before (ΔF₀) and after treatment (ΔF₁), and fluorescence recovery (%ΔFR). Different lowercase letters indicate statistically significant differences between groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).*\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\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eΔF\u003csub\u003e0\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eΔF\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e%ΔFR\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRGS1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-12.6 (1.0) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-6.5 (0.5) \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e47.9 (5.9) \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRGS2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-12.7 (1.0) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-6.7 (0.6) \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e46.5 (6.5) \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRGS3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-13.0 (0.8) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-6.6 (0.5) \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e48.6 (5.1) \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-12.8 (1.0) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-14.7 (1.8) \u003csup\u003ea,\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-13.0 (3.1) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-12.5 (0.8) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-10.6 (0.7) \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e14.7 (2.9) \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003e*ANOVA with Tukey\u0026rsquo;s post hoc for intergroup comparisons\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003eSurface Roughness (Ra), Surface Loss (SL), and ΔSL Analysis\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e presents the mean surface roughness (Ra) values under three conditions: sound enamel (Ra₀), after erosion (Ra₁), and posttreatment (Ra₂). No significant differences were found for Ra₀ or Ra₁ among the groups (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), indicating consistency at baseline or in lesion formation. After treatment (Ra₂), the NC group presented the highest surface roughness (0.282 \u0026micro;m), which was significantly different from that of RGS2 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The PC group presented intermediate values (0.210 \u0026micro;m), whereas RGS1 and RGS3 presented similar roughness levels, with no significant differences from PC or RGS2.\u003c/p\u003e\u003cp\u003eWith respect to ΔRa, all bioactive silica-treated groups (RGS1, RGS2, RGS3) presented negative values, indicating a reduction in surface roughness following treatment. RGS2 achieved the most pronounced smoothing effect (ΔRa = \u0026minus;\u0026thinsp;0.149 \u0026micro;m) and was significantly superior to PC (\u0026ndash;0.055 \u0026micro;m) and NC (+\u0026thinsp;0.056 \u0026micro;m) (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The positive ΔRa observed in the NC group reflects a worsening of surface roughness after treatment.\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 (\u0026plusmn;\u0026thinsp;SD) enamel surface roughness at baseline (Ra₀, sound enamel), after erosion (Ra₁), and after treatment (Ra₂), and roughness change (ΔRa, \u0026micro;m) across experimental groups. Different lowercase letters within a column indicate statistically significant differences between groups at the same time point (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Different uppercase letters within a row indicate statistically significant differences across time points within the same group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).*\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRa\u003csub\u003e0\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRa\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eRa\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eΔRa\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRGS1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.034 (0.022) \u003csup\u003ea,A\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.234 (0.064) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.159 (0.037) \u003csup\u003eb,c,C\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;0.075 (0.033) \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRGS2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.019 (0.008) \u003csup\u003ea,A\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.275 (0.068) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.126 (0.044) \u003csup\u003ec,C\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;0.149 (0.024) \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRGS3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.029 (0.017) \u003csup\u003ea,A\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.254 (0.043) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.150 (0.045) \u003csup\u003eb,c,C\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;0.104 (0.032) \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.019 (0.009) \u003csup\u003ea,A\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.226 (0.069) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.282 (0.062) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e+\u0026thinsp;0.056 (0.046) \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.021 (0.006) \u003csup\u003ea,A\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.265 (0.061) \u003csup\u003ea,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.210 (0.055) \u003csup\u003eb,B\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.055 (0.041) \u003csup\u003eb\u003c/sup\u003e\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*ANOVA with Tukey\u0026rsquo;s post hoc for intergroup comparisons; repeated-measures ANOVA for intragroup comparisons.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the enamel surface loss before and after treatment. SL₀ values (sound vs eroded) did not differ significantly among the groups (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), confirming standardization of lesion depth. After treatment (SL₁), the NC group preented the greatest surface loss, which was significantly greater than that of all the other groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). RGS2 displayed the lowest SL₁ value, whereas RGS1, RGS3, and PC achieved intermediate performance, with no significant differences among them. Compared with those in the PC and NC groups, the bioactive silica groups (RGS1, RGS2, RGS3) in the ΔSL group demonstrated superior preservation of the enamel structure.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003eQualitative surface topography\u003c/h2\u003e\u003cp\u003eThree-dimensional surface analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) revealed distinct topographic patterns among the groups, as represented by color-coded maps (orange\u0026thinsp;=\u0026thinsp;least surface loss; dark blue\u0026thinsp;=\u0026thinsp;greatest loss). RGS2 displayed the most favorable surface profile, with a predominance of green and light blue areas, indicating mild to moderate wear and well-preserved enamel contours. RGS1 exhibited a broader range of colors, from orange in preserved regions to light blue in worn areas, reflecting moderate wear. RGS3, although fluoride-free, presented a similar pattern to that of RGS1 but with a slightly more pronounced wear depth, as evidenced by larger dark blue regions.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn contrast, the NC group (negative control) revealed extensive dark blue regions, indicating severe structural loss and the poorest topographical outcome. The PC group (positive control) presented predominantly light blue surfaces, which is consistent with moderate wear. However, compared with RGS2, PC provided less preservation of the enamel surface, reinforcing the superior protective effect of the bioactive silica formulation containing 1100 ppm fluoride.\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe results of the present study support the rejection of all three null hypotheses, as the incorporation of bioactive silica, particularly in association with fluoride, significantly improved enamel surface properties. These findings confirm the multifactorial benefits of bioactive silica dentifrices in enhancing microhardness, reducing mineral loss, and improving surface smoothness, which are critical for mitigating the effects of erosive-abrasive wear\u003csup\u003e17,20\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eCompared with both conventional fluoride dentifrices and placebo formulations, bioactive silica dentifrices demonstrated superior performance. In particular, RGS2, containing 1100 ppm F⁻, achieved the highest values of %SMHR and %ΔFR, as well as the lowest ΔSL and ΔRa values, indicating greater enamel recovery and structural preservation. These results suggest that an optimized concentration of fluoride in combination with bioactive silica may provide the most favorable conditions for enamel repair in erosive-abrasive scenarios\u003csup\u003e21,22\u003c/sup\u003e. The significantly higher %ΔFR observed in RGS2 confirms its effectiveness in promoting mineral redeposition and mitigating early enamel demineralization, as fluorescence changes have been correlated with subsurface mineral recovery \u003csup\u003e14,22\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eAlthough RGS1 (1450 ppm F⁻) also improved surface microhardness and fluorescence recovery, its outcomes were inferior to those of RGS2. This suggests that excessively high fluoride concentrations may not necessarily lead to superior protective effects when used in combination with bioactive silica, possibly due to less effective interactions between fluoride and the silica matrix under certain physicochemical conditions\u003csup\u003e14,17\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eInterestingly, the results for RGS3, a fluoride-free formulation, also demonstrated significant improvements in %SMHR and %ΔFR compared with the NC. This finding reinforces the hypothesis that silica exerts a fluoride-independent remineralization effect. Silicate ions may directly promote apatite nucleation and stabilize amorphous calcium phosphate, facilitating mineral deposition even in the absence of fluoride\u003csup\u003e15,18,19\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIn this context, the incorporation of bioactive silica has emerged as a promising strategy to overcome the limitations of traditional fluoride therapies. Silica plays a critical role in enamel remineralization by releasing bioactive ions in a controlled and sustained manner. Upon contact with saliva, bioactive silicates hydrate and partially dissolve, releasing fluoride (F⁻), calcium (Ca\u0026sup2;⁺), phosphate (PO₄\u0026sup3;⁻), and silicate (SiO₄⁴⁻) ions in response to the needs of the oral environment\u003csup\u003e11,23,24\u003c/sup\u003e. These ions promote the formation of a new mineralized layer via apatite nucleation, favoring tissue recovery and structural integrity\u003csup\u003e13,14,15\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eFluoride contributes to enamel remineralization by forming a superficial calcium fluoride-like (CaF₂) layer, which functions as a transient ion reservoir under acidic conditions \u003csup\u003e9,10,25\u0026ndash;27\u003c/sup\u003e. However, in highly erosive environments, this layer is rapidly dissolved or mechanically removed by brushing or salivary flow, limiting its protective capacity\u003csup\u003e21,22,28\u003c/sup\u003e. In addition, the inclusion of calcium and phosphate in dentifrices may have limited remineralizing effects when these ions interact prematurely with fluoride, hindering effective deposition onto the enamel surface\u003csup\u003e29,30\u003c/sup\u003e. These limitations underscore the need for advanced formulations, such as those containing bioactive silica, which can modulate ion release and act independently of fluoride to sustain apatite nucleation and deeper mineral integration.\u003c/p\u003e\u003cp\u003eThus, silicon-based dentifrices are promising agents for enamel repair. The gradual release of calcium and phosphate ions facilitates mineral deposition and formation of a new mineralized layer, which integrates into the existing enamel matrix\u003csup\u003e13\u003c/sup\u003e. Previous studies have suggested that silica induces apatite nucleation on the enamel surface, leading to deeper and more stable remineralization\u003csup\u003e14,16,17,31\u003c/sup\u003e. From a mechanistic perspective, silicate ions (SiO₄⁴⁻) partially replace phosphate groups at the B-sites of hydroxyapatite crystals, resulting in the formation of a silicon-enriched apatite structure. In contrast, fluoride ions substitute for hydroxyl groups at the A-sites, forming fluorapatite\u003csup\u003e13,23\u003c/sup\u003e. While fluorapatite enhances the chemical stability of enamel, silicon contributes to biological integration by facilitating the localized deposition of calcium and phosphate in areas of mineral loss\u003csup\u003e13,17,32\u0026ndash;34\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThis distinction in their modes of incorporation\u0026mdash;fluoride at A-sites and silicon at B-sites\u0026mdash;highlights their complementary roles. When combined, fluoride and silica act on different nucleation sites of hydroxyapatite, producing a synergistic effect that enhances enamel remineralization and increases resistance to acid dissolution\u003csup\u003e13,17,31\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eMoreover, the combination of bioactive silica with fluoride can produce synergistic effects, resulting in improved surface stability\u003csup\u003e16\u003c/sup\u003e. Previous studies have investigated the combined effects of silicon, sodium fluoride, and tetrasodium pyrophosphate on the recovery of eroded enamel via pH cycling models \u003csup\u003e14,16,17\u003c/sup\u003e. The results demonstrated that dentifrice formulations containing both silicon and fluoride, especially in an acidified environment, were more effective at restoring enamel hardness and promoting surface restructuring than fluoride alone \u003csup\u003e17,31\u003c/sup\u003e. These formulations were specifically developed to stimulate the formation of fluoride-enriched hydroxyapatite layers, often referred to as \u0026ldquo;enamel-like\u0026rdquo; structures\u003csup\u003e16\u003c/sup\u003e. These layers exhibit enhanced resistance to acid dissolution and support deeper enamel remineralization, contributing to more resilient and long-lasting protection\u003csup\u003e13,29,31\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eConversely, the positive control (PC), containing fluoride alone, significantly increased surface microhardness and improved the surface characteristics\u003csup\u003e35\u0026ndash;37\u003c/sup\u003e. These effects align with the ability of fluoride to form fluorapatite, which enhances the chemical stability of enamel but may not penetrate deeply into demineralized areas\u003csup\u003e25,26,38\u003c/sup\u003e. The benefits of fluoride are therefore more restricted to surface-level changes, which may limit the effectiveness of fluoride-only formulations in managing progressive mineral loss\u003csup\u003e25,26\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eProfilometric analysis provided complementary evidence regarding enamel wear resistance. RGS2 presented the lowest ΔSL and ΔRa values, indicating better surface preservation and smoother morphology after treatment. This outcome is clinically relevant, as reduced surface roughness is associated with lower plaque retention, less bacterial colonization, and diminished susceptibility to acidic challenges\u003csup\u003e28,30\u003c/sup\u003e. RGS1 and PC demonstrated intermediate outcomes, reinforcing the role of both fluoride concentration and the presence of bioactive silica in surface preservation.\u003c/p\u003e\u003cp\u003eTaken together, these findings indicate that bioactive silica, whether used alone or in combination with fluoride, contributes to the repair and protection of eroded enamel subjected to abrasion. The superior performance of RGS2 supports the development of multifunctional dentifrices capable of addressing both preventive and therapeutic needs in managing enamel erosion. The formulation strategy combining optimal fluoride levels with bioactive silica may represent a new benchmark in daily oral care products targeting high-risk patients for erosive tooth wear.\u003c/p\u003e\u003cp\u003eGiven its favorable performance and versatility, bioactive silica represents a clinically relevant strategy for the prevention and repair of early enamel erosion. Further in situ and clinical studies are encouraged to validate these in vitro results and to support the development of innovative commercial dentifrices that integrate bioactive silica into routine oral care.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis in vitro study demonstrated that dentifrices containing bioactive silica, especially when combined with 1100 ppm fluoride, were more effective at restoring enamel microhardness, promoting mineral gain, and reducing surface loss after erosion‒abrasion cycles. The superior performance of this formulation (RGS2) suggests a synergistic effect between fluoride and silica.\u003c/p\u003e\u003cp\u003eFluoride-free silica dentifrice (RGS3) also exhibited significant benefits, confirming the independent remineralizing potential of bioactive silica. These results support the development of innovative dentifrices combining silica and fluoride as promising strategies for preventing and repairing erosive enamel damage.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cem\u003eEthics approval and consent to participate:\u0026nbsp;\u003c/em\u003eThe study used bovine teeth obtained from a certified slaughterhouse as post-mortem by-products. No animals were euthanized for this research, and specific ethical approval was not required. Procedures complied with institutional and international standards for the ethical use of biological material.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eClinical trial number:\u003c/em\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eConsent for publication:\u0026nbsp;\u003c/em\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAvailability of data and materials:\u003c/em\u003e The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCompeting interests:\u003c/em\u003e The authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFunding:\u003c/em\u003e The authors received no specific funding for this work.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAuthors\u003c/em\u003e\u003cem\u003e’ \u003c/em\u003e\u003cem\u003econtributions:\u003c/em\u003e Elizabeth Barreto Galvão Sousa, Anderson Gomes Forte, Ana Maria Barros Chaves Pereira, Andressa Feitosa Bezerra Oliveira, and Fábio Correia Sampaio contributed to the conception and experimental design. Elizabeth Barreto Galvão Sousa, Anderson Gomes Forte, Juliellen Luiz Cunha, Marcel Alves Avelino Paiva, Adriana Moreira Ferreira, and Vitória Régia Rolim Nunes performed the acquisition of data, sample preparation and laboratory procedures. Elizabeth Barreto Galvão Sousa, Anderson Gomes Forte, and Andressa Feitosa Bezerra Oliveira contributed to statistical analysis and interpretation of data. Ana Maria Barros Chaves Pereira, Fábio Correia Sampaio, and Andressa Feitosa Bezerra Oliveira supervised the study and critically reviewed the manuscript. \u0026nbsp;All authors read and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAcknowledgements:\u003c/em\u003e The authors thank the Federal University of Paraíba (UFPB) for providing laboratory facilities and technical support during the study. ChatGPT (OpenAI, 2024) was used to assist with language editing and clarity improvements, under full author oversight. The authors take full responsibility for the content and accuracy of the final version.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eFlemming J, Hannig C, Hannig M. Caries management\u0026mdash;the role of surface interactions in de- and remineralization processes. J Clin Med. 2022;11(23):7044. doi:10.3390/jcm11237044\u003c/li\u003e\n \u003cli\u003eCarvalho T, Lussi A. Chapter 9: Acidic beverages and foods associated with dental erosion and erosive tooth wear. Monogr Oral Sci. 2020;28:91-98. doi:10.1159/000455376\u003c/li\u003e\n \u003cli\u003eAvila V, Betlr\u0026aacute;n EO, Cort\u0026eacute;s A, Usuga-Vacca M, Castellanos Parras JE, Diaz-Baez D, et al. Prevalence of erosive tooth wear and associated risk factors in Colombian adolescents. Braz Oral Res. 2024;38:e050. doi:10.1590/1807-3107bor-2024.vol38.0050\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eOudkerk J, Grenade C, Davarpanah A, Vanheusden A, Vandenput S, Mainjot AK. 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BMC Oral Health. 2022;22(1):489. doi:10.1186/s12903-022-02429-2\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eAkbarzade T, Farmany A, Farhadian M, Khamverdi Z, Dastgir R. Synthesis and characterization of nano bioactive glass for improving enamel remineralization ability of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). BMC Oral Health. 2022;22(1):525. doi:10.1186/s12903-022-02549-9\u003c/li\u003e\n \u003cli\u003eVilhena FV, de Oliveira SML, Matochek MHM, Tomaz PLS, Oliveira TS, D\u003cspan dir=\"RTL\"\u003e\u0026rsquo;\u003c/span\u003eAlpino PHP. Biomimetic mechanism of action of fluoridated toothpaste containing proprietary REFIX technology on the remineralization and repair of demineralized dental tissues: an in vitro study. Eur J Dent. 2021;15(2):236-241. doi:10.1055/s-0040-1716781\u003c/li\u003e\n \u003cli\u003eOliveira AFB, Nunes VRR, Cunha JLD, Forte AG, Andrade AFB, Fernandes NLS, et al. Biomimetic and protective effects of bioactive toothpastes on eroded enamel surfaces. Braz Oral Res. 2024;38:e139. doi:10.1590/1807-3107bor-2024.vol38.0139\u003c/li\u003e\n \u003cli\u003eSim\u0026otilde;es ACCD, Dionizio A, C\u0026acirc;mara JVF, Sabino-Arias IT, Levy FM, Ventura TMO, et al. Do commercial whitening dentifrices increase enamel erosive tooth wear? J Appl Oral Sci. 2020;28:e20190163. doi:10.1590/1678-7757-2019-0163\u003c/li\u003e\n \u003cli\u003eMagalh\u0026atilde;es AC, Kato MT, Rios D, Wiegand A, Attin T, Buzalaf MA. The effect of an experimental 4% TiF4 varnish compared to NaF varnishes and 4% TiF4 solution on dental erosion in vitro. Caries Res. 2008;42(4):269-274. doi:10.1159/000135672\u003c/li\u003e\n \u003cli\u003eDos Santos GS, Felix AF, Matos ICRT, Carvalho GLM, Andr\u0026eacute; CB, Kury M, et al. Effects of dentifrices with antierosive potential on the surface of bovine enamel submitted to acidic beverage. J Esthet Restor Dent. 2025;37(2):553-560. doi:10.1111/jerd.13327\u003c/li\u003e\n \u003cli\u003e\u0026nbsp;Lussi A, Carvalho TS. Erosive tooth wear: a multifactorial condition of growing concern and increasing knowledge. Monogr Oral Sci. 2014;25:1-15. doi:10.1159/000359936\u003c/li\u003e\n \u003cli\u003eCarvalho TS, Colon P, Ganss C, Huysmans MC, Lussi A, Schlueter N, et al. Consensus report of the European Federation of Conservative Dentistry: erosive tooth wear\u0026mdash;diagnosis and management. Clin Oral Investig. 2015;19(7):1557-1561. doi:10.1007/s00784-015-1511-7\u003c/li\u003e\n \u003cli\u003eSilva HM, Soares GA, Mateescu M, et al. Characterization of hydroxyapatite substituted with silicon. In: 53rd Brazilian Congress on Ceramics. Brazil; 2009. Available from:\u003ca href=\"https://inis.iaea.org/records/gtkn1-9be39?utm_source=chatgpt.com\"\u003e\u0026nbsp;\u003c/a\u003ehttps://inis.iaea.org/records/gtkn1-9be39. Accessed June 25, 2025.\u003c/li\u003e\n \u003cli\u003eRamadoss R, Padmanaban R, Subramanian B. Role of bioglass in enamel remineralization: existing strategies and future prospects\u0026mdash;a narrative review. J Biomed Mater Res B Appl Biomater. 2022;110(1):45-66. doi:10.1002/jbm.b.34904\u003c/li\u003e\n \u003cli\u003eLussi A, Buzalaf MAR, Duangthip D, Anttonen V, Ganss C, Jo\u0026atilde;o-Souza SH, et al. The use of fluoride for the prevention of dental erosion and erosive tooth wear in children and adolescents. Eur Arch Paediatr Dent. 2019;20(6):517-527. doi:10.1007/s40368-019-00420-0\u003c/li\u003e\n \u003cli\u003eK\u0026ouml;rner P, Georgis L, Wiedemeier DB, Attin T, Wegehaupt FJ. Potential of different fluoride gels to prevent erosive tooth wear caused by gastroesophageal reflux. BMC Oral Health. 2021;21(1):183. doi:10.1186/s12903-021-01548-6\u003c/li\u003e\n \u003cli\u003eChatzidimitriou K, Seremidi K, Kloukos D, Gizani S, Papaioannou W. The role of calcium in the prevention of erosive tooth wear: a systematic review and meta-analysis. Evid Based Dent. 2024;25(1):55. doi:10.1038/s41432-023-00966-5\u003c/li\u003e\n \u003cli\u003eMachado RNS, Turssi CP, Fran\u0026ccedil;a FM, Amaral FL, Attin T, Basting RT. Varnish with S-PRG filler reduces dentin permeability after erosive/abrasive challenge. Am J Dent. 2023;36(4):193-200.\u003c/li\u003e\n \u003cli\u003eMeyer F, Enax J, Epple M, Amaechi BT, Simader B. Cariogenic biofilms: development, properties, and biomimetic preventive agents. Dent J (Basel). 2021;9(8):88. doi:10.3390/dj9080088\u003c/li\u003e\n \u003cli\u003eLeal IC, Costa WKF, Passos VF. Fluoride dentifrice containing calcium silicate and sodium phosphate salts on dental erosion: in vitro study. Arch Oral Biol. 2020;118:104857. doi:10.1016/j.archoralbio.2020.104857\u003c/li\u003e\n \u003cli\u003eFernandes NLS, Juliellen LDC, Andressa FBO, D\u003cspan dir=\"RTL\"\u003e\u0026rsquo;\u003c/span\u003eAlpino HPP, Sampaio CF. Resistance against erosive challenge of dental enamel treated with 1,450-ppm fluoride toothpastes containing different biomimetic compounds. Eur J Dent. 2021;15(3):433-439. doi:10.1055/s-0041-1725576\u003c/li\u003e\n \u003cli\u003eColombo M, Dagna A, Moroni G, Chiesa M, Poggio C, Pietrocola G. Effect of different protective agents on enamel erosion: an in vitro investigation. J Clin Exp Dent. 2019;11(2):e113-e118. doi:10.4317/jced.55278\u003c/li\u003e\n \u003cli\u003eYu OY, Zhao IS, Mei ML, Lo EC, Chu CH. A review of the common models used in mechanistic studies on demineralization-remineralization for cariology research. Dent J (Basel). 2017;5(2):20. doi:10.3390/dj5020020\u003c/li\u003e\n \u003cli\u003eKarlinsey RL, Mackey AC, Blanken DD, Schwandt CS. Remineralization of eroded enamel lesions by simulated saliva in vitro. Open Dent J. 2012;6:170-176. doi:10.2174/1874210601206010170\u003c/li\u003e\n \u003cli\u003eOlivan SRG, Sfalcin RA, Fernandes KPS, Ferrari RAM, Horliana ACRT, Motta LJ, et al. Preventive effect of remineralizing materials on dental erosion lesions by speckle technique: an in vitro analysis. Photodiagnosis Photodyn Ther. 2020;29:101655. doi:10.1016/j.pdpdt.2020.101655\u003c/li\u003e\n \u003cli\u003eNolasco SC, Rocha LC, Silva PS, Auad SM, Ferreira FM, Assun\u0026ccedil;\u0026atilde;o CM. Effects of different toothpaste formulations on erosive tooth wear prevention: systematic review. Braz Dent Sci. 2023;26(1):e3688. doi:10.4322/bds.2023.e3688\u003c/li\u003e\n \u003cli\u003eAlkattan R, Lippert F, Tang Q, Eckert GJ, Ando M. The influence of hardness and chemical composition on enamel demineralization and subsequent remineralization. J Dent. 2018;75:34-40. doi:10.1016/j.jdent.2018.05.002\u003c/li\u003e\n \u003cli\u003eTanaka T, Kobayashi T, Tamenori Y, Sakanaka A, Kuriki T, Amano A. Phosphoryl oligosaccharides of calcium enhance mineral availability and fluorapatite formation. Arch Oral Biol. 2019;101:135-141. doi:10.1016/j.archoralbio.2019.03.018\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":"Dental Enamel, Toothpaste, Fluoride, Silica, Tooth erosion","lastPublishedDoi":"10.21203/rs.3.rs-7359328/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7359328/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e Dental erosion and abrasion lead to progressive enamel loss, and preventive strategies often rely on fluoride dentifrices. Bioactive silica has emerged as a promising component due to its remineralizing potential, acting alone or synergistically with fluoride. This in vitro study evaluated the efficacy of bioactive silica dentifrices, with or without different fluoride concentrations, in promoting enamel remineralization and protecting against erosion‒abrasion cycles.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eSixty bovine enamel samples were randomly assigned to five groups: RGS1 (bioactive silica dentifrice with 1450 ppm F), RGS2 (bioactive silica dentifrice with 1100 ppm F), RGS3 (bioactive silica dentifrice without fluoride), positive control (PC, 1100 ppm F dentifrice), and negative control (NC, fluoride- and silica-free dentifrice). The samples were subjected to a 5-day erosion-abrasion cycle with daily treatment with the assigned dentifrices. Enamel changes were assessed through surface microhardness recovery (%SMHR), fluorescence recovery (%ΔFR), surface loss (ΔSL), and surface roughness variation (ΔRa). The data were analyzed via one-way and repeated-measures ANOVA, followed by Tukey’s post hoc test (α = 0.05).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e All tested dentifrices significantly affected enamel properties. Compared with the controls, bioactive silica dentifrices improved the microhardness and promoted greater mineral gain (p \u0026lt; 0.05). RGS2 demonstrated the highest %SMHR and ΔFR values, along with lowest surface roughness and enamel loss, indicating superior protective potential. RGS1, RGS3 and PC followed, with intermediate outcomes. The NC group exhibited the poorest performance across all the parameters evaluated (p \u0026lt; 0.05).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion: \u003c/strong\u003eBioactive silica dentifrices significantly enhance enamel remineralization and protection against erosion-abrasion. The results highlight both the synergistic and independent roles of bioactive silica, supporting its application in daily oral care strategies for managing enamel wear.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number:\u003c/strong\u003e not applicable.\u003c/p\u003e","manuscriptTitle":"Innovative dentifrices based on bioactive silica for enamel remineralization and erosion control: an in vitro study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-10 12:59:01","doi":"10.21203/rs.3.rs-7359328/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-10T23:29:57+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-10T14:22:16+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-09T13:04:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"93596070273514377761177455134568437249","date":"2025-10-06T14:52:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"86744689966036249607908033226013771752","date":"2025-10-02T11:19:06+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-29T13:16:39+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-29T13:01:17+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-09-29T12:41:22+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-28T10:53:18+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2025-09-28T09:55:26+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":"e7991070-ac55-408b-b097-17abbc6a6d1e","owner":[],"postedDate":"October 10th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-05-04T13:50:45+00:00","versionOfRecord":{"articleIdentity":"rs-7359328","link":"https://doi.org/10.1186/s12903-025-07502-0","journal":{"identity":"bmc-oral-health","isVorOnly":false,"title":"BMC Oral Health"},"publishedOn":"2025-12-09 15:57:16","publishedOnDateReadable":"December 9th, 2025"},"versionCreatedAt":"2025-10-10 12:59:01","video":"","vorDoi":"10.1186/s12903-025-07502-0","vorDoiUrl":"https://doi.org/10.1186/s12903-025-07502-0","workflowStages":[]},"version":"v1","identity":"rs-7359328","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7359328","identity":"rs-7359328","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}