Effects of additive manufacturing technology and build angle on surface characteristics and microbial adhesion of 3D-printed dental zirconia: An invitro study

Effects of additive manufacturing technology and build angle on surface characteristics and microbial adhesion of 3D-printed dental zirconia: An invitro 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 Effects of additive manufacturing technology and build angle on surface characteristics and microbial adhesion of 3D-printed dental zirconia: An invitro study Kaibin Wu, Tingting Wan, Fangqi Liu, Jörg Lüchtenborg, Brigitte Altmann, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7475480/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 08 Dec, 2025 Read the published version in BMC Oral Health → Version 1 posted 17 You are reading this latest preprint version Abstract Background Microbial colonization on 3D-printed zirconia abutments elevates the risk of peri-implantitis. While additive manufacturing (AM) parameters significantly influence surface roughness and morphology, evidence regarding their impact on bacterial adhesion remains unclear. This study investigated the effects of AM technology and build angles on the surface characteristics and initial microbial adhesion of 3D-printed zirconia. Methods Zirconia discs were fabricated using material jetting (MJ) and digital light processing (DLP) technologies with three build angles (0°, 45°, and 90°), respectively. The surface topographic features and roughness were analyzed using scanning electron microscopy and laser scanning microscopy, respectively. The surface wettability was evaluated via water contact angle measurements. Streptococcus gordonii (S. gordonii) was used to assess bacterial adhesion, which was evaluated via colony-forming unit counts (n = 6) and visualized through SEM imaging. Two-way ANOVA and post hoc Tukey tests were performed for statistical analyses. Results AM technology and build angle significantly affected the surface characteristics of 3D-printed zirconia. Significant interactions were observed for S a , S dr , S tr , and V vv (all p < 0.05). DLP-45° showed the roughest surface, while DLP-0° was the smoothest. Water contact angle varied significantly with both factors (p < 0.05), with MJ-45° showing the highest wettability. For S. gordonii adhesion, a significant interaction was found (p < 0.05), and AM method showed a main effect (p = 0.0104), while build angle alone was not significant (p = 0.0642). The least adhesion occurred in MJ-45° and DLP-0°, with no consistent correlation between S a and bacterial adhesion. Conclusions Printing layer thickness and build angle significantly influenced DLP-printed zirconia’s surface roughness and water contact angle. Furthermore, they significantly impacted the adhesion of S. gordonii to zirconia surfaces. Zirconia Additive manufacturing Surface characteristics Microbial adhesion Material jetting Digital light processing Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1 Introduction The fabrication of zirconia ceramics using additive manufacturing (AM) techniques, namely three-dimensional (3D) printing, has revolutionized dental manufacturing paradigms, yielding geometrically complex, patient-specific prosthetic restorations [ 1 , 2 ]. Unlike subtractive manufacturing, where milling constraints limit the fabrication of intricate geometries, AM offers greater freedom in design and automation [ 3 , 4 ]. Among the various AM techniques applicable to zirconia, material jetting (MJ) and digital light processing (DLP) have gained clinical relevance [ 5 , 6 ]. DLP can efficiently fabricate objects by layer-wise photopolymerization of ceramic-filled resins using projected light patterns, offering high spatial resolution for detailed restorations such as crowns or implant abutments [ 7 ]. In contrast, MJ prints zirconia suspensions as discrete droplets via piezoelectric inkjet printhead and builds structures layer by layer, with the advantage of low organic binder content eliminating extensive post-curing steps [ 8 ]. The MJ process enables smoother as-printed surfaces and potentially higher trueness and bonding strength in complex structures, such as periodontal splints and orthodontic brackets [ 9 ]. Notably, both DLP and MJ inherently induce surface texture and anisotropy due to their distinct layerwise materials deposition and solidification mechanisms, affecting mechanical behaviors and biological interactions at critical interfaces [ 10 – 13 ]. Despite the advantages of 3D-printed zirconia, the long-term clinical success of zirconia-based restorations, particularly implant abutments, might be compromised by microbial colonization at the transgingival interface, increasing the risk of peri-implantitis [ 14 ]. The initial adhesion of bacteria, especially early colonizers such as S. gordonii , is crucial in biofilm formation and the subsequent inflammatory responses of periodontal tissues [ 15 , 16 ]. The surface characteristics of as-printed regions, typically left unpolished and unglazed to preserve marginal accuracy and fit, significantly influence bacterial colonization and biofilm development [ 17 ]. Similarly, smooth and accurately adapted margins in crowns, bridges, and periodontal splints are essential for reducing plaque accumulation and maintaining gingival health [ 18 ]. According to previous studies [ 19 ], AM parameters, particularly build angle and layer thickness, significantly influence surface roughness and morphology [ 20 ]. Given the inherent structural anisotropy of AM, evidence regarding its impact on bacterial adhesion is obscure. The structural anisotropy inherent to AM causes the surface characteristics to vary depending on the direction [ 21 ]. Print orientation alters the exposure status of layer interfaces and support structures, leading to notable and measurable differences in surface roughness and pore interconnectivity [ 22 ]. For example, vertically printed zirconia (0° build angle) exhibits denser layer packing and fewer support-induced defects compared to zirconia printed with angled orientations (45° and 90°). However, layer thickness significantly interacts with build angle to modulate surface topological features. At 50-µm layer thickness, 45°-printed specimens exhibit maximum surface roughness, characterized by pronounced stair-stepping effects and microgrooves, creating preferential sites for microbial colonization. Therefore, S. gordonii shows greater adhesion to 45°-printed surfaces compared to 0° and 90° orientations [ 20 ]. Although prior research has predominantly focused on mechanical anisotropy in DLP-printed ceramics, the orientation-dependent bacterial adhesion phenomena are underexplored, particularly in relation to DLP and MJ technologies. This study investigated the effects of the AM techniques (MJ and DLP) and build angles (0°, 45°, and 90°) on the surface topological features and microbial adhesion of 3D-printed zirconia. The following two null hypotheses were proposed: 1) Surface characteristics would not be significantly affected by either the AM technique or the build angle. 2) S. gordonii adhesion would not be significantly affected by either the AM technique or the build angle. 2 Materials and methods 2.1 Specimen preparation Disk-shaped specimens (10 mm [in diameter] × 2 mm [in thickness]) were designed using the computer-aided design software Fusion 360 (Autodesk, CA, USA) and exported as stereolithography (STL) files, which were processed through the slicing software Chitubox v1.9.5) (CBD-Tech, China) and printed on an MJ system (Carmel 1400C, XJet Ltd., China) using biocompatible ZrO₂ ink at 16-µm resolution, as previously reported [ 23 ]. The samples were printed with different build angles (0°, 45° and 90°) and a soluble support material was used. Lateral (XY) and vertical (Z) axis shrinkage compensation was set to 1.22%, with zero contour offset. After printing, the supports were removed mechanically using reverse osmosis-purified water. Regarding the DLP fabrication, identical geometries were printed (ADT-3D-ZP-Printer-Pro-192-50, Shenzhen Adventure Tech, China) with uniform 125% scaling to accommodate sintering shrinkage. Layer thickness was fixed at 30 µm under 405-nm wavelength exposure with calibrated curing parameters. Build angles (0°, 45°, and 90°) were similarly varied, while software-generated supports ensured model integrity during the printing process. Conventionally milled zirconia (ST‑White, Upcera Dental Technology Co., Ltd., China) specimens served as a control group for the microbial adhesion test. Table 1 summarizes the information on 3D-printed materials. Table 1 Comparison of MJ and DLP printing parameters for zirconia used in this study. Parameter Category MJ Parameters DLP Parameters Print orientation Inkjet deposition Top-down projection Resolution 1200 dots per inch 1920 × 1080 pixels Min. feature size 20 µm (deposited droplet) 50 × 50 µm (pixel) Layer thickness 10 µm 30 µm Printing angle 0º, 45º and 90º 0º, 45º and 90º Curing Thermal evaporation (180°C) UV light (405 nm) Energy input Layer curing time: 60 s Irradiance: 52 mW/cm² 2.2 Surface characterization All the samples underwent surface characterization via digital photography, scanning electron microscope (SEM) morphology analysis, and surface roughness measurement using 3D laser profilometry as specified in ISO 25178-2:2021 [ 24 ]. The samples were photographed at 50× magnification using a handheld optical magnifier. Each sample was manually positioned at a 45° tilt angle and imaged at standard magnification (n = 2). Image processing was applied to remove handling tools and background artifacts. Prior to SEM evaluations, two samples per group (n = 2) were sputter-coated with a thin layer of Au-Pd (Quorum SC7620, West Sussex, UK). Surface morphology was analyzed using an SEM-EDS (TESCAN MIRA LMS, Czech Republic) at an accelerating voltage of 3 kV. Surface roughness was quantified in three samples per group using a color 3D laser scanning microscope (VK-X3000, KEYENCE, Osaka, Japan). A 350 × 250-µm area was scanned at 20× magnification in three randomized locations per sample (n = 9) to provide topography data, including arithmetic mean height (S a ), maximum height (S z ), texture aspect ratio (S tr ), arithmetic mean peak curvature (S pc ), developed interfacial area ratio (S dr ), root mean square height (S q ), skewness (S sk ), kurtosis (S ku ), maximum peak height (S p ), maximum valley depth (S v ), auto-correlation length (S al ), texture direction (S td ), root mean square gradient (S dq ), peak density (S pd ), core roughness depth (S k ), reduced peak height (S pk ), reduced valley depth (S vk ), material ratio at 1% level (S mr1 ), material ratio at 2% level (S mr2 ), extreme peak height (S xp ), valley void volume (V vv ), core void volume (V vc ), peak material volume (V mp ), and core material volume (V mc ). The wettability of zirconia discs (n = 6) was evaluated using a water contact angle (WCA) measurement. A 2-µL deionized water droplet was deposited on each surface, and its contact angle was determined in 20 s using a Dataphysics OCA 15EC system (Dataphysics GmbH, Germany). 2.3 Microbial adhesion test Bacterial adhesion testing was performed according to established methods [ 25 ]. The bacterium was cultured in brain-heart infusion (BHI) broth (Huankai Microbial, Guangdong, China) at 37°C for 24 h to prepare the S. gordonii (ATCC 10558) suspension. Following incubation, the bacterial cells were centrifuged and subsequently reconstituted in fresh BHI broth. The optical density (OD) of this suspension was set to 0.54 at 620 nm, corresponding to approximately 1×10⁸ bacteria/mL. For the adhesion assay, this suspension was further diluted with BHI broth to achieve a final concentration of 1×10⁶ cells/mL. To prepare for the bacterial adhesion experiment, specimens (n = 6) were inoculated at 37ºC for 2 h in 24-well plates containing 100 µL of S. gordonii suspension and 1 mL of BHI broth, allowing bacterial adhesion to the surfaces [ 26 ]. Following incubation, each specimen was transferred to a tube containing 1 mL of sterile phosphate-buffered saline (PBS) solution. Biofilm dispersion was then achieved by sonicating the tubes (Sonoplus HD 2200 50 W - Bandelin Electronic, Berlin, Germany) for 30 s. The resulting suspension was diluted 1000 times before colony plating to ensure an appropriate concentration. The diluted suspension (0.1 mL aliquots) was plated in triplicate on blood agar and incubated for 48 hours at 37.8°C under CO₂ to quantify bacterial adhesion. Plates containing 30–300 colonies post-incubation were selected for S. gordonii colony counting. This enumeration was performed using Point Camera Software (Beijing Pengtu Dream Technology Co., Ltd., Beijing, China). Based on the counts, bacterial adhesion on the specimens was quantified by calculating the colony-forming units per milliliter (CFU/mL), with the resulting values transformed to base-10 logarithms [log 10 (CFU·mL -1 )] [ 27 ]. For biofilm analysis via SEM, two specimens per group were fixed in 2.5% glutaraldehyde and dehydrated through a graded ethanol series. Following overnight drying at 37°C, the specimens were gold-sputtered and examined using SEM. Biofilm topography was characterized using photomicrographs at magnifications of 1000× and 10,000×. 2.4 Statistical analysis Statistical analyses were performed using GraphPad PRISM (v 10.0, GraphPad Software, USA). Data normality was verified using the Shapiro-Wilk test. Significant intergroup differences were assessed using a two-way ANOVA, with AM technology and build angle as independent factors. Tukey multiple comparisons were conducted at a significant threshold of p < 0.05 for multiple comparisons. 3 Results 3.1 Surface characteristics To examine the surface morphology variations induced by different AM technologies and build angles, SEM imaging was performed on zirconia specimens fabricated using MJ and DLP at 0°, 45°, and 90°. Figure 1 presents representative SEM images of zirconia specimens fabricated using MJ and DLP at 0°, 45°, and 90° build angles. Regarding MJ-printed specimens, the surface at a 0° build angle was generally smooth with a parallel distribution of shallow horizontal striations. At a 45° build angle, the MJ-printed surface exhibited a distinct wave-like texture, characterized by undulating, ripple-like features approximately parallel to one another. At a 90° build angle, MJ surfaces displayed densely arranged, parallel horizontal grooves. Partial layer fusion was observed between adjacent layers, causing localized disruptions of the groove continuity. The 0° build angle produced a uniformly flat and featureless surface in DLP-printed specimens. At a 45° build angle, a stair-step morphology emerged. At a 90° build angle, the surface exhibited regular, tightly spaced parallel grooves aligning with the printing direction. Overall, these SEM images reveal distinct, technology-specific surface morphologies and anisotropic patterns that vary systematically with build angle. To evaluate whether surface characteristics were influenced by AM technology or build angle, we compared MJ- and DLP-printed zirconia specimens at identical build angles, as well as different build angles within each technology. Table S1 summarizes the surface texture parameters of all groups. Reconstructed 3D surface topographies and statistical analyses of four representative parameters—S a , S tr , S dr , and V vv —are presented in Fig. 2 , with comparisons performed using two-way ANOVA followed by post hoc Tukey tests. These parameters were selected based on their relevance to surface anisotropy and microbial adhesion [ 28 , 29 ]. S a reflects surface roughness magnitude. S tr indicates the uniformity of feature distribution and the accessible attachment area. S dr captures the extent of potential adhesion sites by quantifying surface area increase while V vv represents the fluid-retaining valley volume that may shelter adherent bacteria [ 30 ]. The result of S a exhibited significant main effects of printing technology and angle (p < 0.0001) with a strong interaction between them (F (2,48) = 13.88, p < 0.0001). DLP-45° showed the highest S a (4.46 ± 0.24 µm, p < 0.0001) among all groups, whereas DLP-0° exhibited the lowest (0.16 ± 0.03 µm). The S a value of MJ-45° (2.51 ± 0.47 µm) was significantly higher than MJ-0°/90° (p < 0.0001). Moreover, S tr , which reflects surface isotropy, was significantly influenced by both printing technology and build angle (p < 0.0001 for each), although no significant interaction was observed between the two factors. DLP-0° exhibited the highest value (0.79 ± 0.26) among all groups, while DLP-90° had the lowest S tr (0.05 ± 0.01), suggesting highly directional surface features. Additionally, S dr was significantly influenced by printing technology (F (2,48) = 118.3, p < 0.0001). Both DLP-45° (17.43 ± 1.80%) and MJ-45° (16.13 ± 4.53%) showed significantly higher S dr compared to their corresponding 0° and 90° groups (p < 0.0001). In contrast, DLP-0° (0.32 ± 0.03%) and MJ-0° (2.82 ± 1.08%) exhibited minimal surface complexity. The printing technology (p < 0.0001), angle (p = 0.0307), and their interaction (F (2,48) = 23.93, p < 0.0001) significantly affected V vv , which reflects the void volume within the surface valleys. DLP-45° exhibited the highest V vv (0.54 ± 0.06 ml/m², p < 0.0010), suggesting that DLP printing at a 45° orientation significantly enhanced the surface void structure. These findings indicate that surface characteristics were significantly affected by both AM technology and build angle. Figure 3 presents the WCA measurements. Two-way ANOVA revealed a significant interaction between printing technology and build angle (F (2, 30) = 39.88, p < 0.0001). Significant differences were detected in main effects, including printing technology (F (1, 30) = 72.31, p < 0.0001) and build angle (F (2, 30) = 23.42, p < 0.0001). Figure 3 b shows the results of post hoc comparisons. Specimens printed via MJ at 45° and 90° exhibited significantly higher contact angles compared to all DLP-printed groups (p < 0.0001), indicating greater hydrophilicity in DLP groups regardless of build angle. Taken together, these findings indicate that both AM technology and build angle significantly influence surface wettability, thereby refuting the null hypothesis that wettability is independent of these factors. 3.2 Adhesion of S. gordonii To evaluate whether S. gordonii adhesion was influenced by AM technology or build angle (Hypothesis 2), SEM images were compared between MJ and DLP-printed zirconia specimens at identical build angles and among different build angles within each technology (Fig. 4 ). At 0°, both MJ- and DLP-printed specimens showed a random and relatively uniform distribution of S. gordonii across the surface. However, fewer adherent bacteria were observed on MJ than on DLP. At 45°, the MJ surface comprised flat regions and deep valleys, with sparse adhesion on flats and increased localization within valleys. In contrast, the DLP-45° surface displayed a stepped morphology with alternating peaks and valleys; bacteria predominantly accumulated in the valleys, whereas regions near the peaks showed fewer adherent bacteria. At 90°, the MJ surface again presented flats and valleys and followed the same pattern as at 45°, with low adhesion on flats and higher adhesion in valleys, and the valleys appeared more numerous and deeper. The DLP-90° surface featured regularly aligned, shallow grooves; bacterial adhesion in both the grooves and adjacent flat regions remained sparse and relatively uniform. Taken together, these qualitative observations indicate that surface architecture, determined by AM technology and build angle, modulates early S. gordonii adhesion. Figure 5 presents the quantitative assessment of S. gordonii adhesion, as determined by CFU counting. Two-way ANOVA revealed a significant interaction between printing technology and build angle (F (2, 102) = 24.88, p < 0.0001), as well as a significant main effect of printing technology (F (1, 102) = 6.813, p = 0.0104). The main effect of build angle was not significant (F (2, 102) = 2.821, p = 0.0642). In the MJ group, S. gordonii adhesion at 45° was significantly lower than that at both 0° (p = 0.0001) and 90° (p < 0.0001), with no significant difference between 0° and 90° (p = 0.6519). In the DLP group, a significant difference was found only between 0° and 45° (p = 0.0158), whereas comparisons between 0° and 90° (p = 0.9984) and between 45° and 90° (p = 0.0511) revealed no significant differences. To evaluate the effect of AM technology at identical build angles, pairwise comparisons were performed between MJ and DLP specimens at 0°, 45°, and 90°. At 0°, S. gordonii adhesion was significantly higher on MJ-printed specimens compared to DLP-printed ones (p = 0.0031). No significant difference was found at 45° (p = 0.9959), while MJ-printed specimens again showed significantly higher adhesion than DLP-printed ones at 90° (p = 0.0120). To evaluate the effect of build angle within each printing technology, further intra-group comparisons were conducted. In the MJ group, adhesion at 45° was significantly lower than at both 0° (p = 0.0001) and 90° (p < 0.0001), whereas no significant difference was found between 0° and 90° (p = 0.6519). In contrast, in the DLP group, adhesion at 45° was significantly higher than at 0° (p = 0.0158), while no significant differences were found between 0° and 90° (p = 0.9984), or between 45° and 90° (p = 0.0511). Taken together, the annotated SEM observations and CFU data show that S. gordonii adhesion depends on the specific combination of AM technology and build angle (interaction p < 0.0001), with a significant main effect of technology (p = 0.0104) but no isolated main effect of angle (p = 0.0642). Accordingly, the second null hypothesis is rejected. 4 Discussion The effects of AM technology and build angle on surface morphology, surface texture parameters, wettability, and early S.gordonii adhesion were evaluated in this study. Comparisons were performed between printing technologies at identical build angles and within each technology across different angles. SEM and surface texture parameter measurements together with WCA data revealed clear differences among groups. Two-way ANOVA confirmed that both AM technology and build angle had significant effects on surface texture metrics (Sa, Str, Sdr, Vvv) and on wettability (all p < 0.05), indicating that surface characteristics depend on both factors. Thus, the first null hypothesis is not supported. For S. gordonii adhesion, the results depended on the specific combined effect of AM technology and print angle (F(2,102) = 24.88, p < 0.0001), with a significant main effect of technology (F(1,102) = 6.813, p = 0.0104) and no isolated main effect of angle (F(2,102) = 2.821, p = 0.0642). These findings demonstrate that adhesion is governed by technology–angle combinations, thereby refuting the second null hypothesis. The differences in surface morphology and texture parameters between test groups arose from the differing working principles of MJ and DLP technologies, as well as how the materials behaved differently depending on the build angle during fabrication (Fig. 6 a). The MJ printing employs a droplet-based jetting process, where both model and support inks, composed of nanoparticle suspensions, are deposited via multiple nozzles [ 31 , 32 ]. Interlayer diffusion occurs during printing, especially at a 45° angle, resulting in the formation of wave-like surface textures (Fig. 6 b) [ 33 ]. This effect is reinforced by the thermal evaporation of carrier solvents and subsequent planarization by a roller, resulting in complex and anisotropic surface patterns [ 8 ]. In contrast, DLP printing relies on voxel-wise layer exposure and uses a projected light source, resulting in more uniform, stepwise textures aligned with the stacking direction (Fig. 6 b) [ 34 ]. The voxel-based architecture becomes more pronounced at a 90° build angle, manifesting as regular linear grooves along the build axis [ 5 ]. Quantitative texture metrics confirmed these morphological distinctions (Fig. 6 c). The S a values, which reflect the mean surface height deviation, were elevated in MJ-45° and DLP-45° groups, consistent with SEM observations, where oblique angles produced undulating surfaces. In MJ, droplet diffusion and stacking irregularities resulted in wavy morphologies [ 35 ]. In contrast, in DLP, stair-step edges formed due to voxel-based layering [ 36 ]. S tr values indicate surface isotropy, with S tr values 0.5 representing an isotropic texture [ 37 ]. DLP-90° exhibited the lowest S tr values, consistent with the aligned microgrooves observed in SEM images. In contrast, MJ-printed surfaces at 0° and 45° showed higher S tr values (p > 0.5), corresponding to visually uniform and non-directional surface features. The S dr and V vv parameters, which represent developed surface area and void volume in valleys, further highlight surface complexity [ 38 ]. MJ-45° showed the highest S dr , consistent with its irregular folded features seen in SEM. Additionally, the DLP-45° also exhibited elevated S dr and V vv values, which are attributable to regular but deep stepwise structures. Wettability measurements revealed that both the AM technology and build angle significantly influenced the surface wettability of 3D-printed zirconia (p < 0.0001). In all groups, WCA values ranged between approximately 65° and 94°, suggesting partial wettability without reaching the hydrophobicity threshold (100°) [ 39 ]. In all groups, MJ-0° exhibited the lowest contact angle (65.3° ± 3.3), indicating the strongest hydrophilicity, with MJ-45° showing the highest (94.2° ± 7.1). Surface texture parameters provided partial insight into these variations. Although DLP-45° had the highest S a , S dr , and V vv , its contact angle remained modest (65.7° ± 5.8), indicating that increased roughness did not necessarily reduce wettability [ 40 ]. In contrast, MJ-45° displayed moderately high roughness values but reached the highest WCA, suggesting a different surface wetting regime, possibly influenced by the geometry and continuity of surface features. Moreover, S tr , which indicates surface isotropy, was not consistently related to WCA. For instance, DLP-0° had the highest S tr (0.79) but a higher contact angle compared to MJ-0°, suggesting that an isotropic surface alone does not guarantee better wettability. These findings underscore that the relationship between surface roughness and wettability is complex and non-linear [ 41 , 42 ]. Parameters such as S a , S dr , and V vv offer proper quantification. However, surface morphology—especially the spatial arrangement and feature shape—may impact wetting behavior, possibly through transitions between Wenzel and Cassie–Baxter states [ 43 , 44 ]. The adhesion of S. gordonii was significantly affected by both the AM technology and the build angle (p < 0.0001). In the DLP group, S. gordonii adhesion was significantly higher in the 45° specimens compared to the 0° specimens (p = 0.0158), and modestly higher than in the 90° specimens, although the difference did not reach statistical significance (p = 0.0511). This pattern was accompanied by concurrent variations in surface texture parameters [ 45 ]. Among the three DLP build angles, DLP-45° exhibited the highest S a (4.46 µm ± 0.24), S dr (17.43% ± 0.01), and V vv (0.54 mL/m² ± 0.06), indicating a rougher surface with increased interface area and greater void volume [ 46 ]. While DLP-45° and DLP-90° showed S tr values < 0.3, indicating anisotropic textures [ 47 ], DLP-0° exhibited a markedly higher S tr (0.79 ± 0.26), suggesting a more isotropic and evenly distributed surface pattern. Considering the correlation between surface roughness and microbial adhesion, these topographic characteristics could enhance bacterial colonization through several mechanisms [ 48 – 51 ]. A larger developed area related to S tr may increase the available contact surface, while higher V vv values may contribute to liquid pooling and local microenvironmental retention, favoring microbial settlement [ 52 ]. The observed anisotropy may also promote linear accumulation patterns along grooves or step edges. In the DLP-45° group, bacteria were frequently found in the stepped valley structures, suggesting that such topographic confinement may help protect adherent bacteria against shearing forces, promoting their retention [ 48 , 53 ]. In the MJ group, S. gordonii adhesion followed a markedly different pattern from that observed in the DLP group. The 90° build angle exhibited the highest bacterial adhesion, significantly greater than both 45° (p < 0.0001) and 0° (p = 0.0381) angles. Interestingly, this adhesion trend did not directly coincide with variations in surface texture parameters. For instance, MJ-45° exhibited the highest S a (2.51µm ± 0.47), S dr (16.13% ± 4.53) and V vv (0.41 mL/m² ± 0.06) in the MJ group, while MJ-90° showed lower S a (1.65µm ± 0.35), S dr (3.89% ± 0.96) and moderate V vv (0.25 mL/m² ± 0.07). These findings suggest that, unlike in DLP, bacterial adhesion in MJ may not be strongly associated with increased surface complexity or void volume [ 29 ]. One possible explanation is that the nature of the surface morphology produced by MJ printing differs substantially from that of DLP, even when the texture parameters appear similar [ 7 , 54 ]. For example, MJ-90° surfaces exhibited vertically aligned groove-like features, possibly resulting from layer-by-layer droplet stacking and drying along the Z-axis [ 55 ]. Such directional microstructures may provide elongated contact tracks or anchoring valleys to facilitate bacterial accumulation, despite lower S dr and V vv values [ 16 , 26 ]. By contrast, the MJ-45° surface, despite its higher roughness and void volume than MJ-0° and MJ-90°, showed the lowest bacterial adhesion in this group. SEM images of MJ-45° revealed more irregular and folded topographic features without clearly defined recesses, possibly limiting effective attachment areas or disrupting bacterial spreading [ 40 , 56 ]. Additionally, although MJ-45° exhibited the highest WCA (94.2° ± 7.1), its adhesion level differed significantly from MJ-90°, which had a similar WCA. This suggests that within MJ-printed specimens, surface wettability is not the sole determinant of S. gordonii adhesion, and that other factors such as surface morphology and texture parameters may play a more influential role [ 57 ]. Altogether, these findings highlight that the relationship between surface texture and bacterial adhesion strongly depends on the AM strategy. In the DLP group, higher S a , S dr , and V vv value s of 45° group compared to 0° and 90° group were associated with increased S. gordonii adhesion, suggesting that standard texture metrics may effectively reflect adhesion-prone features such as stepped valleys and confined topographic characteristics. In the MJ group, no single roughness parameter consistently aligned with the observed bacterial adhesion trends, and the pattern also did not fully correspond to the changes in wettability. This discrepancy suggests that early S. gordonii adhesion on MJ-printed surfaces is not predominantly governed by roughness magnitude or hydrophilicity alone, but rather by the spatial arrangement, orientation, and continuity of surface features generated by the printing process [ 51 ]. The interplay between these morphological characteristics may influence micro-scale contact points, sheltering effects, and nutrient accessibility [ 56 ]. This may modulate bacterial attachment in ways that are not captured by conventional surface metrics. Overall, these findings highlight that microbial responses to printed zirconia depend on a complex interplay between surface geometry, topographic accessibility, and fabrication-induced architecture. Several limitations should be acknowledged despite the comprehensive characterization of surface features and microbial adhesion in this study. First, only S. gordonii was employed as a representative early colonizer [ 58 ]. Other microbial species, particularly those participating in multispecies biofilms, may mount different responses to surface characteristics [ 59 ]. Second, although surface texture parameters offered quantitative insights, their biological relevance was inferred rather than directly validated. Therefore, further investigations using correlation analyses or regression modeling are necessary to clarify these relationships. Third, all the experiments were conducted under static in vitro conditions. In vivo environments, involving factors such as salivary pellicle formation [ 60 ], dynamic shear forces [ 59 ], and host immune responses [ 61 ], may influence microbial adhesion in ways not explored in the present study. Future studies should examine how AM-induced surface features and wettability influence biofilm development over time. 5 Conclusion Within the limitations of this in vitro study, the following conclusions can be drawn: Both the AM technology and the build angle significantly influenced the surface morphology, surface texture parameters, and WCA of 3D-printed zirconia. DLP-45° and MJ-45° exhibited the most complex surface textures, reflected by elevated S a , S dr , and V vv values. The interaction between printing technology and build angle significantly affected the adhesion of S. gordonii . In DLP, greater adhesion was aligned with higher surface roughness and void volume; in contrast, in MJ, vertical structural features at 90° appeared more influential. Standard texture metrics must be interpreted in conjunction with morphology and AM-specific surface architecture to understand microbial behavior. These findings highlight the significance of process-aware surface design in optimizing biofilm resistance in 3D-printed zirconia restorations. Abbreviations 3D: Three-dimensional AM: Additive manufacturing MJ: Material jetting DLP: Digital light processing SEM: Scanning electron microscope WCA: Water contact angle BHI: Brain-heart infusion OD: Optical density PBS: Phosphate-buffered saline CFU: Colony forming unit S a : Arithmetic mean height S z : Maximum height S tr : Texture aspect ratio S pc : Arithmetic mean peak curvature S dr : Developed interfacial area ratio S q : Root mean square height S sk : Skewness S ku : Kurtosis S p : Maximum peak height S v : Maximum valley depth S al : Auto-correlation length S td : Texture direction S dq : Root mean square gradient S pd : Peak density S k : Core roughness depth S pk : Reduced peak height S vk : Reduced valley depth S mr1 : Material ratio at 1% level S mr2 : Material ratio at 2% level S xp : Extreme peak height V vv : Valley void volume V vc : Core void volume V mp : Peak material volume V mc : Core material volume Declarations Ethics approval and consent to participate: Not applicable Clinical trial number: Not applicable. Consent for publication: Not applicable Availability of data and materials: The data supporting the findings of this study are obtainable from the corresponding author upon reasonable request. Competing interests: The authors declare that they have no competing interests. Funding: The study was financed by the National Natural Science Foundation of China (82301134), Guangdong Basic and Applied Basic Research Foundation (2021A1515111140), Key Clinical technique of Guangzhou Municipal Health Commission (2023C-ZD07). The authors acknowledge the financial support from Guangzhou Medical University. Authors' contributions: KW was responsible for the study conception, design, experiments, statistical analysis, interpretation, and drafting of the manuscript. TW performed microbial adhesion test, statistical analysis, visualization, and contributed to manuscript drafting. FL contributed to the surface characterization test, interpretation and critical revision of the manuscript. JL participated in language polishing and critical revision of the manuscript. BA contributed to the study conception, design, interpretation, and critical revision of the manuscript. FW assisted in the critical revision of the manuscript. ZW contributed to the study conception, design, and critical revision of the manuscript. PL was involved in the study design, partial drafting, and critical revision of the manuscript. All authors have given their final approval and agree to be accountable for all aspects of the work, ensuring its integrity and accuracy. Acknowledgments: The authors acknowledge the support from the Key Clinical technique of Guangzhou Municipal Health Commission (2023C-ZD07). References Cesar PF, Miranda RB de P, Santos KF, Scherrer SS, Zhang Y. Recent advances in dental zirconia: 15 years of material and processing evolution. Dent Mater Off Publ Acad Dent Mater. 2024;40:824–36. Oh S-E, Park J-M, Kim J-H, Shim J-S, Park Y-B. 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Souza JGS, Nagay BE, Martins R, Bertolini M, Shibli JA, Aparicio C, et al. Engineered surface strategies to manage dental implant‐related infections. Papa S, Maalouf M, Claudel P, Sedao X, Di Maio Y, Hamzeh-Cognasse H, et al. Key topographic parameters driving surface adhesion of Porphyromonas gingivalis. Sci Rep. 2023;13:15893. Li P, Fernandez PK, Spintzyk S, Schmidt F, Yassine J, Beuer F, et al. Effects of layer thickness and build angle on the microbial adhesion of denture base polymers manufactured by digital light processing. J Prosthodont Res. 2023;67:562–7. Zhang X, Wu X, Shi J. Additive manufacturing of zirconia ceramics: a state-of-the-art review. J Mater Res Technol. 2020;9:9029–48. Lyu J, Yang X, Li Y, Tan J, Liu X. Dimensional accuracy and clinical adaptation of monolithic zirconia crowns fabricated with the nanoparticle jetting technique. J Prosthet Dent. 2024;132:985.e1-985.e7. Han A, Tsoi JKH, Lung CYK, Matinlinna JP. 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Front Microbiol. 2022;13. Additional Declarations No competing interests reported. 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(a) Reconstructed 3D surface topographies of specimens. (b) Sa, Str, Sdr, and Vvv for all groups (means and standard deviations). Black dashed lines represent the corresponding mean values of milled specimens for each parameter. (c) Heatmap of Tukey multiple comparisons between the groups. The blue square represents a statistical significance (p \u0026lt; 0.05); in contrast, the white one depicts no statistical differences (p \u0026gt;0.05).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7475480/v1/3078af6a81e322f7c613aaf0.png"},{"id":91511625,"identity":"5d8e488c-ad77-4247-bfd8-f2246f98ff33","added_by":"auto","created_at":"2025-09-17 08:51:50","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":139157,"visible":true,"origin":"","legend":"\u003cp\u003eThe wettability of MJ- and DLP-printed specimens. (a) The water contact angle of specimens (n=6). Black dashed lines represent the mean values of the milled specimens as baseline references. (b) The heatmap of Tukey multiple comparisons among all the groups. The color gradient bar indicates the distribution of p-values; the blue square represents a statistical significance (p \u0026lt; 0.05), and the white one depicts no significant differences (p \u0026gt; 0.05).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7475480/v1/13f44eb8324d7587fa0dfc14.png"},{"id":91515719,"identity":"73a6a942-575a-4f6c-913e-3ab0b265c096","added_by":"auto","created_at":"2025-09-17 09:15:50","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":3898442,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative SEM images showing the adhesion of S. gordonii to specimen surfaces after a 2-hour incubation, acquired at 1000×, 5000×, and 10000× magnifications under an accelerating voltage of 15 kV. At 1000× magnification, red and blue boxes (labeled “A” and “B”) indicate different surface regions selected for higher-magnification imaging. Corresponding 5000× and 10000× images are shown in adjacent columns. S. gordonii were highlighted in pink in the 10000× images.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7475480/v1/c5978b45fa8b4142a7b443a4.png"},{"id":91511629,"identity":"18505479-5934-47ef-b73d-1dae95caea37","added_by":"auto","created_at":"2025-09-17 08:51:50","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1173660,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eS. gordonii\u003c/em\u003eadhesion of the tested specimens. (a) Representative images of colony counts after incubation with \u003cem\u003eS. gordonii\u003c/em\u003e (2 h). (b) Quantitative assessment of \u003cem\u003eS. gordonii\u003c/em\u003e adhesion for all experimental groups (n = 6). The box plots display the interquartile range (25th–75th percentile), with the horizontal line indicating the median and whiskers representing the minimum and maximum values. The black dashed line indicates the mean adhesion level of the milled specimens, used as a baseline reference. (c) Heatmap of Tukey’s multiple comparisons among all groups. The blue squares indicate statistically significant differences (p \u0026lt; 0.05), while white squares indicate no significance (p \u0026gt; 0.05).\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7475480/v1/b80cfee08d88937f8a6b50bf.png"},{"id":91510370,"identity":"32269ba1-086e-42bc-b773-60b5bcda19e0","added_by":"auto","created_at":"2025-09-17 08:43:50","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":384130,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic representation of the working principle and MJ- and DLP-printed process causing the surface texture.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7475480/v1/0e9d62e9eb47c2e1e019b391.png"},{"id":98243534,"identity":"e6cd7957-4227-4deb-b61f-eadea342afb6","added_by":"auto","created_at":"2025-12-15 16:08:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":10318645,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7475480/v1/e77c2e2f-181e-4621-8f73-44bbff4e4a00.pdf"},{"id":91511627,"identity":"3fe5a093-ceac-4436-9cb4-d61a351d7340","added_by":"auto","created_at":"2025-09-17 08:51:50","extension":"tiff","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":568762,"visible":true,"origin":"","legend":"","description":"","filename":"Graphicalabstract.tiff","url":"https://assets-eu.researchsquare.com/files/rs-7475480/v1/49bb2ec98bfae1e1007b3443.tiff"},{"id":91513310,"identity":"a33991ed-96e7-490a-b7ce-07b69e03c193","added_by":"auto","created_at":"2025-09-17 08:59:50","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":24448,"visible":true,"origin":"","legend":"","description":"","filename":"Textureparameters.docx","url":"https://assets-eu.researchsquare.com/files/rs-7475480/v1/2bf246c0a631135226200f2d.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effects of additive manufacturing technology and build angle on surface characteristics and microbial adhesion of 3D-printed dental zirconia: An invitro study","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe fabrication of zirconia ceramics using additive manufacturing (AM) techniques, namely three-dimensional (3D) printing, has revolutionized dental manufacturing paradigms, yielding geometrically complex, patient-specific prosthetic restorations [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Unlike subtractive manufacturing, where milling constraints limit the fabrication of intricate geometries, AM offers greater freedom in design and automation [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Among the various AM techniques applicable to zirconia, material jetting (MJ) and digital light processing (DLP) have gained clinical relevance [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. DLP can efficiently fabricate objects by layer-wise photopolymerization of ceramic-filled resins using projected light patterns, offering high spatial resolution for detailed restorations such as crowns or implant abutments [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In contrast, MJ prints zirconia suspensions as discrete droplets via piezoelectric inkjet printhead and builds structures layer by layer, with the advantage of low organic binder content eliminating extensive post-curing steps [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The MJ process enables smoother as-printed surfaces and potentially higher trueness and bonding strength in complex structures, such as periodontal splints and orthodontic brackets [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Notably, both DLP and MJ inherently induce surface texture and anisotropy due to their distinct layerwise materials deposition and solidification mechanisms, affecting mechanical behaviors and biological interactions at critical interfaces [\u003cspan additionalcitationids=\"CR11 CR12\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eDespite the advantages of 3D-printed zirconia, the long-term clinical success of zirconia-based restorations, particularly implant abutments, might be compromised by microbial colonization at the transgingival interface, increasing the risk of peri-implantitis [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The initial adhesion of bacteria, especially early colonizers such as \u003cem\u003eS. gordonii\u003c/em\u003e, is crucial in biofilm formation and the subsequent inflammatory responses of periodontal tissues [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The surface characteristics of as-printed regions, typically left unpolished and unglazed to preserve marginal accuracy and fit, significantly influence bacterial colonization and biofilm development [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Similarly, smooth and accurately adapted margins in crowns, bridges, and periodontal splints are essential for reducing plaque accumulation and maintaining gingival health [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. According to previous studies [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], AM parameters, particularly build angle and layer thickness, significantly influence surface roughness and morphology [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Given the inherent structural anisotropy of AM, evidence regarding its impact on bacterial adhesion is obscure.\u003c/p\u003e\u003cp\u003eThe structural anisotropy inherent to AM causes the surface characteristics to vary depending on the direction [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Print orientation alters the exposure status of layer interfaces and support structures, leading to notable and measurable differences in surface roughness and pore interconnectivity [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. For example, vertically printed zirconia (0\u0026deg; build angle) exhibits denser layer packing and fewer support-induced defects compared to zirconia printed with angled orientations (45\u0026deg; and 90\u0026deg;). However, layer thickness significantly interacts with build angle to modulate surface topological features. At 50-\u0026micro;m layer thickness, 45\u0026deg;-printed specimens exhibit maximum surface roughness, characterized by pronounced stair-stepping effects and microgrooves, creating preferential sites for microbial colonization. Therefore, \u003cem\u003eS. gordonii\u003c/em\u003e shows greater adhesion to 45\u0026deg;-printed surfaces compared to 0\u0026deg; and 90\u0026deg; orientations [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Although prior research has predominantly focused on mechanical anisotropy in DLP-printed ceramics, the orientation-dependent bacterial adhesion phenomena are underexplored, particularly in relation to DLP and MJ technologies.\u003c/p\u003e\u003cp\u003eThis study investigated the effects of the AM techniques (MJ and DLP) and build angles (0\u0026deg;, 45\u0026deg;, and 90\u0026deg;) on the surface topological features and microbial adhesion of 3D-printed zirconia. The following two null hypotheses were proposed: 1) Surface characteristics would not be significantly affected by either the AM technique or the build angle. 2) \u003cem\u003eS. gordonii\u003c/em\u003e adhesion would not be significantly affected by either the AM technique or the build angle.\u003c/p\u003e"},{"header":"2 Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Specimen preparation\u003c/h2\u003e\u003cp\u003eDisk-shaped specimens (10 mm [in diameter] \u0026times; 2 mm [in thickness]) were designed using the computer-aided design software Fusion 360 (Autodesk, CA, USA) and exported as stereolithography (STL) files, which were processed through the slicing software Chitubox v1.9.5) (CBD-Tech, China) and printed on an MJ system (Carmel 1400C, XJet Ltd., China) using biocompatible ZrO₂ ink at 16-\u0026micro;m resolution, as previously reported [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The samples were printed with different build angles (0\u0026deg;, 45\u0026deg; and 90\u0026deg;) and a soluble support material was used. Lateral (XY) and vertical (Z) axis shrinkage compensation was set to 1.22%, with zero contour offset. After printing, the supports were removed mechanically using reverse osmosis-purified water.\u003c/p\u003e\u003cp\u003eRegarding the DLP fabrication, identical geometries were printed (ADT-3D-ZP-Printer-Pro-192-50, Shenzhen Adventure Tech, China) with uniform 125% scaling to accommodate sintering shrinkage. Layer thickness was fixed at 30 \u0026micro;m under 405-nm wavelength exposure with calibrated curing parameters. Build angles (0\u0026deg;, 45\u0026deg;, and 90\u0026deg;) were similarly varied, while software-generated supports ensured model integrity during the printing process. Conventionally milled zirconia (ST‑White, Upcera Dental Technology Co., Ltd., China) specimens served as a control group for the microbial adhesion test. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e summarizes the information on 3D-printed materials.\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\u003eComparison of MJ and DLP printing parameters for zirconia used 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\u003eParameter Category\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMJ Parameters\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDLP Parameters\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrint orientation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eInkjet deposition\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTop-down projection\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eResolution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1200 dots per inch\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1920 \u0026times; 1080 pixels\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMin. feature size\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e20 \u0026micro;m (deposited droplet)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50 \u0026times; 50 \u0026micro;m (pixel)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLayer thickness\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10 \u0026micro;m\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30 \u0026micro;m\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrinting angle\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u0026ordm;, 45\u0026ordm; and 90\u0026ordm;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u0026ordm;, 45\u0026ordm; and 90\u0026ordm;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCuring\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThermal evaporation (180\u0026deg;C)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eUV light (405 nm)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEnergy input\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLayer curing time: 60 s\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eIrradiance: 52 mW/cm\u0026sup2;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Surface characterization\u003c/h2\u003e\u003cp\u003eAll the samples underwent surface characterization via digital photography, scanning electron microscope (SEM) morphology analysis, and surface roughness measurement using 3D laser profilometry as specified in ISO 25178-2:2021 [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The samples were photographed at 50\u0026times; magnification using a handheld optical magnifier. Each sample was manually positioned at a 45\u0026deg; tilt angle and imaged at standard magnification (n\u0026thinsp;=\u0026thinsp;2).\u003c/p\u003e\u003cp\u003eImage processing was applied to remove handling tools and background artifacts. Prior to SEM evaluations, two samples per group (n\u0026thinsp;=\u0026thinsp;2) were sputter-coated with a thin layer of Au-Pd (Quorum SC7620, West Sussex, UK). Surface morphology was analyzed using an SEM-EDS (TESCAN MIRA LMS, Czech Republic) at an accelerating voltage of 3 kV.\u003c/p\u003e\u003cp\u003eSurface roughness was quantified in three samples per group using a color 3D laser scanning microscope (VK-X3000, KEYENCE, Osaka, Japan). A 350 \u0026times; 250-\u0026micro;m area was scanned at 20\u0026times; magnification in three randomized locations per sample (n\u0026thinsp;=\u0026thinsp;9) to provide topography data, including arithmetic mean height (S\u003csub\u003ea\u003c/sub\u003e), maximum height (S\u003csub\u003ez\u003c/sub\u003e), texture aspect ratio (S\u003csub\u003etr\u003c/sub\u003e), arithmetic mean peak curvature (S\u003csub\u003epc\u003c/sub\u003e), developed interfacial area ratio (S\u003csub\u003edr\u003c/sub\u003e), root mean square height (S\u003csub\u003eq\u003c/sub\u003e), skewness (S\u003csub\u003esk\u003c/sub\u003e), kurtosis (S\u003csub\u003eku\u003c/sub\u003e), maximum peak height (S\u003csub\u003ep\u003c/sub\u003e), maximum valley depth (S\u003csub\u003ev\u003c/sub\u003e), auto-correlation length (S\u003csub\u003eal\u003c/sub\u003e), texture direction (S\u003csub\u003etd\u003c/sub\u003e), root mean square gradient (S\u003csub\u003edq\u003c/sub\u003e), peak density (S\u003csub\u003epd\u003c/sub\u003e), core roughness depth (S\u003csub\u003ek\u003c/sub\u003e), reduced peak height (S\u003csub\u003epk\u003c/sub\u003e), reduced valley depth (S\u003csub\u003evk\u003c/sub\u003e), material ratio at 1% level (S\u003csub\u003emr1\u003c/sub\u003e), material ratio at 2% level (S\u003csub\u003emr2\u003c/sub\u003e), extreme peak height (S\u003csub\u003exp\u003c/sub\u003e), valley void volume (V\u003csub\u003evv\u003c/sub\u003e), core void volume (V\u003csub\u003evc\u003c/sub\u003e), peak material volume (V\u003csub\u003emp\u003c/sub\u003e), and core material volume (V\u003csub\u003emc\u003c/sub\u003e). The wettability of zirconia discs (n\u0026thinsp;=\u0026thinsp;6) was evaluated using a water contact angle (WCA) measurement. A 2-\u0026micro;L deionized water droplet was deposited on each surface, and its contact angle was determined in 20 s using a Dataphysics OCA 15EC system (Dataphysics GmbH, Germany).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Microbial adhesion test\u003c/h2\u003e\u003cp\u003eBacterial adhesion testing was performed according to established methods [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The bacterium was cultured in brain-heart infusion (BHI) broth (Huankai Microbial, Guangdong, China) at 37\u0026deg;C for 24 h to prepare the \u003cem\u003eS. gordonii\u003c/em\u003e (ATCC 10558) suspension. Following incubation, the bacterial cells were centrifuged and subsequently reconstituted in fresh BHI broth. The optical density (OD) of this suspension was set to 0.54 at 620 nm, corresponding to approximately 1\u0026times;10⁸ bacteria/mL. For the adhesion assay, this suspension was further diluted with BHI broth to achieve a final concentration of 1\u0026times;10⁶ cells/mL.\u003c/p\u003e\u003cp\u003eTo prepare for the bacterial adhesion experiment, specimens (n\u0026thinsp;=\u0026thinsp;6) were inoculated at 37\u0026ordm;C for 2 h in 24-well plates containing 100 \u0026micro;L of \u003cem\u003eS. gordonii\u003c/em\u003e suspension and 1 mL of BHI broth, allowing bacterial adhesion to the surfaces [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Following incubation, each specimen was transferred to a tube containing 1 mL of sterile phosphate-buffered saline (PBS) solution. Biofilm dispersion was then achieved by sonicating the tubes (Sonoplus HD 2200 50 W - Bandelin Electronic, Berlin, Germany) for 30 s. The resulting suspension was diluted 1000 times before colony plating to ensure an appropriate concentration.\u003c/p\u003e\u003cp\u003eThe diluted suspension (0.1 mL aliquots) was plated in triplicate on blood agar and incubated for 48 hours at 37.8\u0026deg;C under CO₂ to quantify bacterial adhesion. Plates containing 30\u0026ndash;300 colonies post-incubation were selected for \u003cem\u003eS. gordonii\u003c/em\u003e colony counting. This enumeration was performed using Point Camera Software (Beijing Pengtu Dream Technology Co., Ltd., Beijing, China). Based on the counts, bacterial adhesion on the specimens was quantified by calculating the colony-forming units per milliliter (CFU/mL), with the resulting values transformed to base-10 logarithms [log\u003csub\u003e10\u003c/sub\u003e (CFU\u0026middot;mL\u003csup\u003e-1\u003c/sup\u003e)] [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eFor biofilm analysis via SEM, two specimens per group were fixed in 2.5% glutaraldehyde and dehydrated through a graded ethanol series. Following overnight drying at 37\u0026deg;C, the specimens were gold-sputtered and examined using SEM. Biofilm topography was characterized using photomicrographs at magnifications of 1000\u0026times; and 10,000\u0026times;.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Statistical analysis\u003c/h2\u003e\u003cp\u003eStatistical analyses were performed using GraphPad PRISM (v 10.0, GraphPad Software, USA). Data normality was verified using the Shapiro-Wilk test. Significant intergroup differences were assessed using a two-way ANOVA, with AM technology and build angle as independent factors. Tukey multiple comparisons were conducted at a significant threshold of p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 for multiple comparisons.\u003c/p\u003e\u003c/div\u003e"},{"header":"3 Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Surface characteristics\u003c/h2\u003e\u003cp\u003eTo examine the surface morphology variations induced by different AM technologies and build angles, SEM imaging was performed on zirconia specimens fabricated using MJ and DLP at 0\u0026deg;, 45\u0026deg;, and 90\u0026deg;. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents representative SEM images of zirconia specimens fabricated using MJ and DLP at 0\u0026deg;, 45\u0026deg;, and 90\u0026deg; build angles. Regarding MJ-printed specimens, the surface at a 0\u0026deg; build angle was generally smooth with a parallel distribution of shallow horizontal striations. At a 45\u0026deg; build angle, the MJ-printed surface exhibited a distinct wave-like texture, characterized by undulating, ripple-like features approximately parallel to one another. At a 90\u0026deg; build angle, MJ surfaces displayed densely arranged, parallel horizontal grooves. Partial layer fusion was observed between adjacent layers, causing localized disruptions of the groove continuity. The 0\u0026deg; build angle produced a uniformly flat and featureless surface in DLP-printed specimens. At a 45\u0026deg; build angle, a stair-step morphology emerged. At a 90\u0026deg; build angle, the surface exhibited regular, tightly spaced parallel grooves aligning with the printing direction.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eOverall, these SEM images reveal distinct, technology-specific surface morphologies and anisotropic patterns that vary systematically with build angle.\u003c/p\u003e\u003cp\u003eTo evaluate whether surface characteristics were influenced by AM technology or build angle, we compared MJ- and DLP-printed zirconia specimens at identical build angles, as well as different build angles within each technology.\u003c/p\u003e\u003cp\u003e\u003cb\u003eTable \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e summarizes the surface texture parameters of all groups. Reconstructed 3D surface topographies and statistical analyses of four representative parameters\u0026mdash;S\u003csub\u003ea\u003c/sub\u003e, S\u003csub\u003etr\u003c/sub\u003e, S\u003csub\u003edr\u003c/sub\u003e, and V\u003csub\u003evv\u003c/sub\u003e\u0026mdash;are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, with comparisons performed using two-way ANOVA followed by post hoc Tukey tests. These parameters were selected based on their relevance to surface anisotropy and microbial adhesion [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. S\u003csub\u003ea\u003c/sub\u003e reflects surface roughness magnitude. S\u003csub\u003etr\u003c/sub\u003e indicates the uniformity of feature distribution and the accessible attachment area. S\u003csub\u003edr\u003c/sub\u003e captures the extent of potential adhesion sites by quantifying surface area increase while V\u003csub\u003evv\u003c/sub\u003e represents the fluid-retaining valley volume that may shelter adherent bacteria [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. The result of S\u003csub\u003ea\u003c/sub\u003e exhibited significant main effects of printing technology and angle (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) with a strong interaction between them (F\u003csub\u003e(2,48)\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;13.88, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). DLP-45\u0026deg; showed the highest S\u003csub\u003ea\u003c/sub\u003e (4.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24 \u0026micro;m, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) among all groups, whereas DLP-0\u0026deg; exhibited the lowest (0.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03 \u0026micro;m). The S\u003csub\u003ea\u003c/sub\u003e value of MJ-45\u0026deg; (2.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.47 \u0026micro;m) was significantly higher than MJ-0\u0026deg;/90\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). Moreover, S\u003csub\u003etr\u003c/sub\u003e, which reflects surface isotropy, was significantly influenced by both printing technology and build angle (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001 for each), although no significant interaction was observed between the two factors. DLP-0\u0026deg; exhibited the highest value (0.79\u0026thinsp;\u0026plusmn;\u0026thinsp;0.26) among all groups, while DLP-90\u0026deg; had the lowest S\u003csub\u003etr\u003c/sub\u003e (0.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01), suggesting highly directional surface features. Additionally, S\u003csub\u003edr\u003c/sub\u003e was significantly influenced by printing technology (F\u003csub\u003e(2,48)\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;118.3, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). Both DLP-45\u0026deg; (17.43\u0026thinsp;\u0026plusmn;\u0026thinsp;1.80%) and MJ-45\u0026deg; (16.13\u0026thinsp;\u0026plusmn;\u0026thinsp;4.53%) showed significantly higher S\u003csub\u003edr\u003c/sub\u003e compared to their corresponding 0\u0026deg; and 90\u0026deg; groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). In contrast, DLP-0\u0026deg; (0.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03%) and MJ-0\u0026deg; (2.82\u0026thinsp;\u0026plusmn;\u0026thinsp;1.08%) exhibited minimal surface complexity. The printing technology (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), angle (p\u0026thinsp;=\u0026thinsp;0.0307), and their interaction (F\u003csub\u003e(2,48)\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;23.93, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) significantly affected V\u003csub\u003evv\u003c/sub\u003e, which reflects the void volume within the surface valleys. DLP-45\u0026deg; exhibited the highest V\u003csub\u003evv\u003c/sub\u003e (0.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 ml/m\u0026sup2;, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0010), suggesting that DLP printing at a 45\u0026deg; orientation significantly enhanced the surface void structure. These findings indicate that surface characteristics were significantly affected by both AM technology and build angle.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents the WCA measurements. Two-way ANOVA revealed a significant interaction between printing technology and build angle (F\u003csub\u003e(2, 30)\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;39.88, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). Significant differences were detected in main effects, including printing technology (F\u003csub\u003e(1, 30)\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;72.31, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) and build angle (F\u003csub\u003e(2, 30)\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;23.42, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb shows the results of post hoc comparisons. Specimens printed via MJ at 45\u0026deg; and 90\u0026deg; exhibited significantly higher contact angles compared to all DLP-printed groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), indicating greater hydrophilicity in DLP groups regardless of build angle. Taken together, these findings indicate that both AM technology and build angle significantly influence surface wettability, thereby refuting the null hypothesis that wettability is independent of these factors.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Adhesion of S. gordonii\u003c/h2\u003e\u003cp\u003eTo evaluate whether \u003cem\u003eS. gordonii\u003c/em\u003e adhesion was influenced by AM technology or build angle (Hypothesis 2), SEM images were compared between MJ and DLP-printed zirconia specimens at identical build angles and among different build angles within each technology (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAt 0\u0026deg;, both MJ- and DLP-printed specimens showed a random and relatively uniform distribution of \u003cem\u003eS. gordonii\u003c/em\u003e across the surface. However, fewer adherent bacteria were observed on MJ than on DLP. At 45\u0026deg;, the MJ surface comprised flat regions and deep valleys, with sparse adhesion on flats and increased localization within valleys. In contrast, the DLP-45\u0026deg; surface displayed a stepped morphology with alternating peaks and valleys; bacteria predominantly accumulated in the valleys, whereas regions near the peaks showed fewer adherent bacteria. At 90\u0026deg;, the MJ surface again presented flats and valleys and followed the same pattern as at 45\u0026deg;, with low adhesion on flats and higher adhesion in valleys, and the valleys appeared more numerous and deeper. The DLP-90\u0026deg; surface featured regularly aligned, shallow grooves; bacterial adhesion in both the grooves and adjacent flat regions remained sparse and relatively uniform. Taken together, these qualitative observations indicate that surface architecture, determined by AM technology and build angle, modulates early \u003cem\u003eS. gordonii\u003c/em\u003e adhesion.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e presents the quantitative assessment of \u003cem\u003eS. gordonii\u003c/em\u003e adhesion, as determined by CFU counting. Two-way ANOVA revealed a significant interaction between printing technology and build angle (F\u003csub\u003e(2, 102)\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;24.88, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), as well as a significant main effect of printing technology (F\u003csub\u003e(1, 102)\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;6.813, p\u0026thinsp;=\u0026thinsp;0.0104). The main effect of build angle was not significant (F\u003csub\u003e(2, 102)\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;2.821, p\u0026thinsp;=\u0026thinsp;0.0642).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn the MJ group, \u003cem\u003eS. gordonii\u003c/em\u003e adhesion at 45\u0026deg; was significantly lower than that at both 0\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0001) and 90\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), with no significant difference between 0\u0026deg; and 90\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.6519). In the DLP group, a significant difference was found only between 0\u0026deg; and 45\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0158), whereas comparisons between 0\u0026deg; and 90\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.9984) and between 45\u0026deg; and 90\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0511) revealed no significant differences.\u003c/p\u003e\u003cp\u003eTo evaluate the effect of AM technology at identical build angles, pairwise comparisons were performed between MJ and DLP specimens at 0\u0026deg;, 45\u0026deg;, and 90\u0026deg;. At 0\u0026deg;, \u003cem\u003eS. gordonii\u003c/em\u003e adhesion was significantly higher on MJ-printed specimens compared to DLP-printed ones (p\u0026thinsp;=\u0026thinsp;0.0031). No significant difference was found at 45\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.9959), while MJ-printed specimens again showed significantly higher adhesion than DLP-printed ones at 90\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0120). To evaluate the effect of build angle within each printing technology, further intra-group comparisons were conducted. In the MJ group, adhesion at 45\u0026deg; was significantly lower than at both 0\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0001) and 90\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), whereas no significant difference was found between 0\u0026deg; and 90\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.6519). In contrast, in the DLP group, adhesion at 45\u0026deg; was significantly higher than at 0\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0158), while no significant differences were found between 0\u0026deg; and 90\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.9984), or between 45\u0026deg; and 90\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0511).\u003c/p\u003e\u003cp\u003eTaken together, the annotated SEM observations and CFU data show that S. gordonii adhesion depends on the specific combination of AM technology and build angle (interaction p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), with a significant main effect of technology (p\u0026thinsp;=\u0026thinsp;0.0104) but no isolated main effect of angle (p\u0026thinsp;=\u0026thinsp;0.0642). Accordingly, the second null hypothesis is rejected.\u003c/p\u003e\u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cp\u003eThe effects of AM technology and build angle on surface morphology, surface texture parameters, wettability, and early \u003cem\u003eS.gordonii\u003c/em\u003e adhesion were evaluated in this study. Comparisons were performed between printing technologies at identical build angles and within each technology across different angles.\u003c/p\u003e\u003cp\u003eSEM and surface texture parameter measurements together with WCA data revealed clear differences among groups. Two-way ANOVA confirmed that both AM technology and build angle had significant effects on surface texture metrics (Sa, Str, Sdr, Vvv) and on wettability (all p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), indicating that surface characteristics depend on both factors. Thus, the first null hypothesis is not supported. For \u003cem\u003eS. gordonii\u003c/em\u003e adhesion, the results depended on the specific combined effect of AM technology and print angle (F(2,102)\u0026thinsp;=\u0026thinsp;24.88, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), with a significant main effect of technology (F(1,102)\u0026thinsp;=\u0026thinsp;6.813, p\u0026thinsp;=\u0026thinsp;0.0104) and no isolated main effect of angle (F(2,102)\u0026thinsp;=\u0026thinsp;2.821, p\u0026thinsp;=\u0026thinsp;0.0642). These findings demonstrate that adhesion is governed by technology\u0026ndash;angle combinations, thereby refuting the second null hypothesis.\u003c/p\u003e\u003cp\u003eThe differences in surface morphology and texture parameters between test groups arose from the differing working principles of MJ and DLP technologies, as well as how the materials behaved differently depending on the build angle during fabrication (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea). The MJ printing employs a droplet-based jetting process, where both model and support inks, composed of nanoparticle suspensions, are deposited via multiple nozzles [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Interlayer diffusion occurs during printing, especially at a 45\u0026deg; angle, resulting in the formation of wave-like surface textures (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb) [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. This effect is reinforced by the thermal evaporation of carrier solvents and subsequent planarization by a roller, resulting in complex and anisotropic surface patterns [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. In contrast, DLP printing relies on voxel-wise layer exposure and uses a projected light source, resulting in more uniform, stepwise textures aligned with the stacking direction (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb) [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The voxel-based architecture becomes more pronounced at a 90\u0026deg; build angle, manifesting as regular linear grooves along the build axis [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eQuantitative texture metrics confirmed these morphological distinctions (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec). The S\u003csub\u003ea\u003c/sub\u003e values, which reflect the mean surface height deviation, were elevated in MJ-45\u0026deg; and DLP-45\u0026deg; groups, consistent with SEM observations, where oblique angles produced undulating surfaces. In MJ, droplet diffusion and stacking irregularities resulted in wavy morphologies [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. In contrast, in DLP, stair-step edges formed due to voxel-based layering [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. S\u003csub\u003etr\u003c/sub\u003e values indicate surface isotropy, with S\u003csub\u003etr\u003c/sub\u003e values\u0026thinsp;\u0026lt;\u0026thinsp;0.3 indicating a directionally dominant (anisotropic) surface and S\u003csub\u003etr\u003c/sub\u003e values\u0026thinsp;\u0026gt;\u0026thinsp;0.5 representing an isotropic texture [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. DLP-90\u0026deg; exhibited the lowest S\u003csub\u003etr\u003c/sub\u003e values, consistent with the aligned microgrooves observed in SEM images. In contrast, MJ-printed surfaces at 0\u0026deg; and 45\u0026deg; showed higher S\u003csub\u003etr\u003c/sub\u003e values (p\u0026thinsp;\u0026gt;\u0026thinsp;0.5), corresponding to visually uniform and non-directional surface features. The S\u003csub\u003edr\u003c/sub\u003e and V\u003csub\u003evv\u003c/sub\u003e parameters, which represent developed surface area and void volume in valleys, further highlight surface complexity [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. MJ-45\u0026deg; showed the highest S\u003csub\u003edr\u003c/sub\u003e, consistent with its irregular folded features seen in SEM. Additionally, the DLP-45\u0026deg; also exhibited elevated S\u003csub\u003edr\u003c/sub\u003e and V\u003csub\u003evv\u003c/sub\u003e values, which are attributable to regular but deep stepwise structures.\u003c/p\u003e\u003cp\u003eWettability measurements revealed that both the AM technology and build angle significantly influenced the surface wettability of 3D-printed zirconia (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). In all groups, WCA values ranged between approximately 65\u0026deg; and 94\u0026deg;, suggesting partial wettability without reaching the hydrophobicity threshold (100\u0026deg;) [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. In all groups, MJ-0\u0026deg; exhibited the lowest contact angle (65.3\u0026deg; \u0026plusmn; 3.3), indicating the strongest hydrophilicity, with MJ-45\u0026deg; showing the highest (94.2\u0026deg; \u0026plusmn; 7.1). Surface texture parameters provided partial insight into these variations. Although DLP-45\u0026deg; had the highest S\u003csub\u003ea\u003c/sub\u003e, S\u003csub\u003edr\u003c/sub\u003e, and V\u003csub\u003evv\u003c/sub\u003e, its contact angle remained modest (65.7\u0026deg; \u0026plusmn; 5.8), indicating that increased roughness did not necessarily reduce wettability [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. In contrast, MJ-45\u0026deg; displayed moderately high roughness values but reached the highest WCA, suggesting a different surface wetting regime, possibly influenced by the geometry and continuity of surface features. Moreover, S\u003csub\u003etr\u003c/sub\u003e, which indicates surface isotropy, was not consistently related to WCA. For instance, DLP-0\u0026deg; had the highest S\u003csub\u003etr\u003c/sub\u003e (0.79) but a higher contact angle compared to MJ-0\u0026deg;, suggesting that an isotropic surface alone does not guarantee better wettability. These findings underscore that the relationship between surface roughness and wettability is complex and non-linear [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Parameters such as S\u003csub\u003ea\u003c/sub\u003e, S\u003csub\u003edr\u003c/sub\u003e, and V\u003csub\u003evv\u003c/sub\u003e offer proper quantification. However, surface morphology\u0026mdash;especially the spatial arrangement and feature shape\u0026mdash;may impact wetting behavior, possibly through transitions between Wenzel and Cassie\u0026ndash;Baxter states [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe adhesion of \u003cem\u003eS. gordonii\u003c/em\u003e was significantly affected by both the AM technology and the build angle (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). In the DLP group, \u003cem\u003eS. gordonii\u003c/em\u003e adhesion was significantly higher in the 45\u0026deg; specimens compared to the 0\u0026deg; specimens (p\u0026thinsp;=\u0026thinsp;0.0158), and modestly higher than in the 90\u0026deg; specimens, although the difference did not reach statistical significance (p\u0026thinsp;=\u0026thinsp;0.0511). This pattern was accompanied by concurrent variations in surface texture parameters [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. Among the three DLP build angles, DLP-45\u0026deg; exhibited the highest S\u003csub\u003ea\u003c/sub\u003e (4.46 \u0026micro;m\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24), S\u003csub\u003edr\u003c/sub\u003e (17.43% \u0026plusmn; 0.01), and V\u003csub\u003evv\u003c/sub\u003e (0.54 mL/m\u0026sup2; \u0026plusmn; 0.06), indicating a rougher surface with increased interface area and greater void volume [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. While DLP-45\u0026deg; and DLP-90\u0026deg; showed S\u003csub\u003etr\u003c/sub\u003e values\u0026thinsp;\u0026lt;\u0026thinsp;0.3, indicating anisotropic textures [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e], DLP-0\u0026deg; exhibited a markedly higher S\u003csub\u003etr\u003c/sub\u003e (0.79\u0026thinsp;\u0026plusmn;\u0026thinsp;0.26), suggesting a more isotropic and evenly distributed surface pattern.\u003c/p\u003e\u003cp\u003eConsidering the correlation between surface roughness and microbial adhesion, these topographic characteristics could enhance bacterial colonization through several mechanisms [\u003cspan additionalcitationids=\"CR49 CR50\" citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]. A larger developed area related to S\u003csub\u003etr\u003c/sub\u003e may increase the available contact surface, while higher V\u003csub\u003evv\u003c/sub\u003e values may contribute to liquid pooling and local microenvironmental retention, favoring microbial settlement [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]. The observed anisotropy may also promote linear accumulation patterns along grooves or step edges. In the DLP-45\u0026deg; group, bacteria were frequently found in the stepped valley structures, suggesting that such topographic confinement may help protect adherent bacteria against shearing forces, promoting their retention [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e, \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn the MJ group, \u003cem\u003eS. gordonii\u003c/em\u003e adhesion followed a markedly different pattern from that observed in the DLP group. The 90\u0026deg; build angle exhibited the highest bacterial adhesion, significantly greater than both 45\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) and 0\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0381) angles. Interestingly, this adhesion trend did not directly coincide with variations in surface texture parameters. For instance, MJ-45\u0026deg; exhibited the highest S\u003csub\u003ea\u003c/sub\u003e (2.51\u0026micro;m\u0026thinsp;\u0026plusmn;\u0026thinsp;0.47), S\u003csub\u003edr\u003c/sub\u003e (16.13% \u0026plusmn; 4.53) and V\u003csub\u003evv\u003c/sub\u003e (0.41 mL/m\u0026sup2; \u0026plusmn; 0.06) in the MJ group, while MJ-90\u0026deg; showed lower S\u003csub\u003ea\u003c/sub\u003e (1.65\u0026micro;m\u0026thinsp;\u0026plusmn;\u0026thinsp;0.35), S\u003csub\u003edr\u003c/sub\u003e (3.89% \u0026plusmn; 0.96) and moderate V\u003csub\u003evv\u003c/sub\u003e (0.25 mL/m\u0026sup2; \u0026plusmn; 0.07). These findings suggest that, unlike in DLP, bacterial adhesion in MJ may not be strongly associated with increased surface complexity or void volume [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. One possible explanation is that the nature of the surface morphology produced by MJ printing differs substantially from that of DLP, even when the texture parameters appear similar [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e]. For example, MJ-90\u0026deg; surfaces exhibited vertically aligned groove-like features, possibly resulting from layer-by-layer droplet stacking and drying along the Z-axis [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. Such directional microstructures may provide elongated contact tracks or anchoring valleys to facilitate bacterial accumulation, despite lower S\u003csub\u003edr\u003c/sub\u003e and V\u003csub\u003evv\u003c/sub\u003e values [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. By contrast, the MJ-45\u0026deg; surface, despite its higher roughness and void volume than MJ-0\u0026deg; and MJ-90\u0026deg;, showed the lowest bacterial adhesion in this group. SEM images of MJ-45\u0026deg; revealed more irregular and folded topographic features without clearly defined recesses, possibly limiting effective attachment areas or disrupting bacterial spreading [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. Additionally, although MJ-45\u0026deg; exhibited the highest WCA (94.2\u0026deg; \u0026plusmn; 7.1), its adhesion level differed significantly from MJ-90\u0026deg;, which had a similar WCA. This suggests that within MJ-printed specimens, surface wettability is not the sole determinant of \u003cem\u003eS. gordonii\u003c/em\u003e adhesion, and that other factors such as surface morphology and texture parameters may play a more influential role [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAltogether, these findings highlight that the relationship between surface texture and bacterial adhesion strongly depends on the AM strategy. In the DLP group, higher S\u003csub\u003ea\u003c/sub\u003e, S\u003csub\u003edr\u003c/sub\u003e, and V\u003csub\u003evv\u003c/sub\u003e value\u003cb\u003es\u003c/b\u003e of 45\u0026deg; group compared to 0\u0026deg; and 90\u0026deg; group were associated with increased \u003cem\u003eS. gordonii\u003c/em\u003e adhesion, suggesting that standard texture metrics may effectively reflect adhesion-prone features such as stepped valleys and confined topographic characteristics. In the MJ group, no single roughness parameter consistently aligned with the observed bacterial adhesion trends, and the pattern also did not fully correspond to the changes in wettability. This discrepancy suggests that early S. gordonii adhesion on MJ-printed surfaces is not predominantly governed by roughness magnitude or hydrophilicity alone, but rather by the spatial arrangement, orientation, and continuity of surface features generated by the printing process [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]. The interplay between these morphological characteristics may influence micro-scale contact points, sheltering effects, and nutrient accessibility [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. This may modulate bacterial attachment in ways that are not captured by conventional surface metrics. Overall, these findings highlight that microbial responses to printed zirconia depend on a complex interplay between surface geometry, topographic accessibility, and fabrication-induced architecture.\u003c/p\u003e\u003cp\u003eSeveral limitations should be acknowledged despite the comprehensive characterization of surface features and microbial adhesion in this study. First, only \u003cem\u003eS. gordonii\u003c/em\u003e was employed as a representative early colonizer [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. Other microbial species, particularly those participating in multispecies biofilms, may mount different responses to surface characteristics [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e]. Second, although surface texture parameters offered quantitative insights, their biological relevance was inferred rather than directly validated. Therefore, further investigations using correlation analyses or regression modeling are necessary to clarify these relationships. Third, all the experiments were conducted under static in vitro conditions. In vivo environments, involving factors such as salivary pellicle formation [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e], dynamic shear forces [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e], and host immune responses [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e], may influence microbial adhesion in ways not explored in the present study. Future studies should examine how AM-induced surface features and wettability influence biofilm development over time.\u003c/p\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eWithin the limitations of this in vitro study, the following conclusions can be drawn:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eBoth the AM technology and the build angle significantly influenced the surface morphology, surface texture parameters, and WCA of 3D-printed zirconia.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eDLP-45\u0026deg; and MJ-45\u0026deg; exhibited the most complex surface textures, reflected by elevated S\u003csub\u003ea\u003c/sub\u003e, S\u003csub\u003edr\u003c/sub\u003e, and V\u003csub\u003evv\u003c/sub\u003e values.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe interaction between printing technology and build angle significantly affected \u003cem\u003ethe adhesion of S. gordonii\u003c/em\u003e.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eIn DLP, greater adhesion was aligned with higher surface roughness and void volume; in contrast, in MJ, vertical structural features at 90\u0026deg; appeared more influential.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eStandard texture metrics must be interpreted in conjunction with morphology and AM-specific surface architecture to understand microbial behavior.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThese findings highlight the significance of process-aware surface design in optimizing biofilm resistance in 3D-printed zirconia restorations.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e3D: Three-dimensional\u003c/p\u003e\n\u003cp\u003eAM: Additive manufacturing\u003c/p\u003e\n\u003cp\u003eMJ:\u0026nbsp;Material jetting\u003c/p\u003e\n\u003cp\u003eDLP:\u0026nbsp;Digital light processing\u003c/p\u003e\n\u003cp\u003eSEM: Scanning electron microscope\u003c/p\u003e\n\u003cp\u003eWCA: Water contact angle\u003c/p\u003e\n\u003cp\u003eBHI: Brain-heart infusion\u003c/p\u003e\n\u003cp\u003eOD: Optical density\u003c/p\u003e\n\u003cp\u003ePBS: Phosphate-buffered saline\u003c/p\u003e\n\u003cp\u003eCFU: Colony forming unit\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003ea\u003c/sub\u003e: Arithmetic mean height\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003ez\u003c/sub\u003e: Maximum height\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003etr\u003c/sub\u003e: Texture aspect ratio\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003epc\u003c/sub\u003e: Arithmetic mean peak curvature\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003edr\u003c/sub\u003e: Developed interfacial area ratio\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003eq\u003c/sub\u003e: Root mean square height\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003esk\u003c/sub\u003e: Skewness\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003eku\u003c/sub\u003e: Kurtosis\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003ep\u003c/sub\u003e: Maximum peak height\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003ev\u003c/sub\u003e: Maximum valley depth\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003eal\u003c/sub\u003e: Auto-correlation length\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003etd\u003c/sub\u003e: Texture direction\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003edq\u003c/sub\u003e: Root mean square gradient\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003epd\u003c/sub\u003e: Peak density\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003ek\u003c/sub\u003e: Core roughness depth\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003epk\u003c/sub\u003e: Reduced peak height\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003evk\u003c/sub\u003e: Reduced valley depth\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003emr1\u003c/sub\u003e: Material ratio at 1% level \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003emr2\u003c/sub\u003e: Material ratio at 2% level \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eS\u003csub\u003exp\u003c/sub\u003e: Extreme peak height\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eV\u003csub\u003evv\u003c/sub\u003e: Valley void volume \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eV\u003csub\u003evc\u003c/sub\u003e: Core void volume \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eV\u003csub\u003emp\u003c/sub\u003e: Peak material volume\u003c/p\u003e\n\u003cp\u003eV\u003csub\u003emc\u003c/sub\u003e: Core material volume \u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number:\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials:\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThe data supporting the findings of this study are obtainable from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThe study was financed by the National Natural Science Foundation of China (82301134), Guangdong Basic and Applied Basic Research Foundation (2021A1515111140), Key Clinical technique of Guangzhou Municipal Health Commission (2023C-ZD07). The authors acknowledge the financial support from Guangzhou Medical University.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions:\u003c/strong\u003e KW was responsible for the study conception, design, experiments, statistical analysis, interpretation, and drafting of the manuscript. TW performed microbial adhesion test, statistical analysis, visualization, and contributed to manuscript drafting. FL contributed to the surface characterization test, interpretation and critical revision of the manuscript. JL participated in language polishing and critical revision of the manuscript. BA contributed to the study conception, design, interpretation, and critical revision of the manuscript. FW assisted in the critical revision of the manuscript. ZW contributed to the study conception, design, and critical revision of the manuscript. PL was involved in the study design, partial drafting, and critical revision of the manuscript. All authors have given their final approval and agree to be accountable for all aspects of the work, ensuring its integrity and accuracy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e The authors acknowledge the support from the Key Clinical technique of Guangzhou Municipal Health Commission (2023C-ZD07).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCesar PF, Miranda RB de P, Santos KF, Scherrer SS, Zhang Y. Recent advances in dental zirconia: 15 years of material and processing evolution. Dent Mater Off Publ Acad Dent Mater. 2024;40:824\u0026ndash;36.\u003c/li\u003e\n\u003cli\u003eOh S-E, Park J-M, Kim J-H, Shim J-S, Park Y-B. Mechanical properties and crown accuracy of additively manufactured zirconia restorations. Dent Mater. 2024;40:1546\u0026ndash;56.\u003c/li\u003e\n\u003cli\u003eHuang B, Chen M, Wang J, Zhang X. 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Improving wettability, antibacterial and tribological behaviors of zirconia ceramics through surface texturing. Ceram Int. 2022;48:3702\u0026ndash;10.\u003c/li\u003e\n\u003cli\u003eWassmann T, Kreis S, Behr M, Buergers R. The influence of surface texture and wettability on initial bacterial adhesion on titanium and zirconium oxide dental implants. Int J Implant Dent. 2017;3:32.\u003c/li\u003e\n\u003cli\u003eChoi S, Jo Y-H, Luke Yeo I-S, Yoon H-I, Lee J-H, Han J-S. The effect of surface material, roughness and wettability on the adhesion and proliferation of \u003cem\u003eStreptococcus gordonii\u003c/em\u003e, \u003cem\u003eFusobacterium nucleatum\u003c/em\u003e and \u003cem\u003ePorphyromonas gingivalis\u003c/em\u003e\u003cem\u003e☆\u003c/em\u003e. J Dent Sci. 2023;18:517\u0026ndash;25.\u003c/li\u003e\n\u003cli\u003eKang D-H, Choi H, Yoo Y-J, Kim J-H, Park Y-B, Moon H-S. Effect of polishing method on surface roughness and bacterial adhesion of zirconia-porcelain veneer. 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Competitive dynamics and balance between Streptococcus mutans and commensal streptococci in oral microecology. Crit Rev Microbiol. 2025;51:532\u0026ndash;43.\u003c/li\u003e\n\u003cli\u003eMarsh PD, Do T, Beighton D, Devine DA. Influence of saliva on the oral microbiota. Periodontol 2000. 2016;70:80\u0026ndash;92.\u003c/li\u003e\n\u003cli\u003eLiu Y, Qv W, Ma Y, Zhang Y, Ding C, Chu M, et al. The interplay between oral microbes and immune responses. Front Microbiol. 2022;13.\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":"Zirconia, Additive manufacturing, Surface characteristics, Microbial adhesion, Material jetting, Digital light processing","lastPublishedDoi":"10.21203/rs.3.rs-7475480/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7475480/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eMicrobial colonization on 3D-printed zirconia abutments elevates the risk of peri-implantitis. While additive manufacturing (AM) parameters significantly influence surface roughness and morphology, evidence regarding their impact on bacterial adhesion remains unclear. This study investigated the effects of AM technology and build angles on the surface characteristics and initial microbial adhesion of 3D-printed zirconia.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eZirconia discs were fabricated using material jetting (MJ) and digital light processing (DLP) technologies with three build angles (0\u0026deg;, 45\u0026deg;, and 90\u0026deg;), respectively. The surface topographic features and roughness were analyzed using scanning electron microscopy and laser scanning microscopy, respectively. The surface wettability was evaluated via water contact angle measurements. Streptococcus gordonii (S. gordonii) was used to assess bacterial adhesion, which was evaluated via colony-forming unit counts (n\u0026thinsp;=\u0026thinsp;6) and visualized through SEM imaging. Two-way ANOVA and post hoc Tukey tests were performed for statistical analyses.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eAM technology and build angle significantly affected the surface characteristics of 3D-printed zirconia. Significant interactions were observed for S\u003csub\u003ea\u003c/sub\u003e, S\u003csub\u003edr\u003c/sub\u003e, S\u003csub\u003etr\u003c/sub\u003e, and V\u003csub\u003evv\u003c/sub\u003e (all p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). DLP-45\u0026deg; showed the roughest surface, while DLP-0\u0026deg; was the smoothest. Water contact angle varied significantly with both factors (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), with MJ-45\u0026deg; showing the highest wettability. For S. gordonii adhesion, a significant interaction was found (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and AM method showed a main effect (p\u0026thinsp;=\u0026thinsp;0.0104), while build angle alone was not significant (p\u0026thinsp;=\u0026thinsp;0.0642). The least adhesion occurred in MJ-45\u0026deg; and DLP-0\u0026deg;, with no consistent correlation between S\u003csub\u003ea\u003c/sub\u003e and bacterial adhesion.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e\u003cp\u003ePrinting layer thickness and build angle significantly influenced DLP-printed zirconia\u0026rsquo;s surface roughness and water contact angle. Furthermore, they significantly impacted the adhesion of S. gordonii to zirconia surfaces.\u003c/p\u003e","manuscriptTitle":"Effects of additive manufacturing technology and build angle on surface characteristics and microbial adhesion of 3D-printed dental zirconia: An invitro study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-17 08:43:45","doi":"10.21203/rs.3.rs-7475480/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-07T06:16:28+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-06T21:14:14+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-06T11:20:18+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-01T16:45:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"234292855234196614660115093971357306674","date":"2025-10-01T13:23:31+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"263165793944862744583459594128880327655","date":"2025-10-01T11:53:33+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-26T14:49:32+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"68666660258570840177693630236038853980","date":"2025-09-15T05:03:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"198293310065095911243799769461759851638","date":"2025-09-14T03:40:29+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"252792133822809076889854793195830418363","date":"2025-09-13T23:24:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"49732701462758811696730371835513953079","date":"2025-09-09T15:22:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"144156226384001843874080258522917205980","date":"2025-09-09T13:54:24+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-09T13:43:29+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-09-08T12:05:24+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-01T06:59:35+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-01T06:57:31+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2025-08-28T02:12:24+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":"cdbdfc6a-9b3f-43b4-909c-a5cc9e39073e","owner":[],"postedDate":"September 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-15T16:01:23+00:00","versionOfRecord":{"articleIdentity":"rs-7475480","link":"https://doi.org/10.1186/s12903-025-07379-z","journal":{"identity":"bmc-oral-health","isVorOnly":false,"title":"BMC Oral Health"},"publishedOn":"2025-12-08 15:57:34","publishedOnDateReadable":"December 8th, 2025"},"versionCreatedAt":"2025-09-17 08:43:45","video":"","vorDoi":"10.1186/s12903-025-07379-z","vorDoiUrl":"https://doi.org/10.1186/s12903-025-07379-z","workflowStages":[]},"version":"v1","identity":"rs-7475480","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7475480","identity":"rs-7475480","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}