Fahad A. Al-Harbi

Purpose: To assess the internal and marginal gaps and the fracture load of different machinable ceramics for an inlay acting as a support for a removable partial denture. Materials and Methods: Sixty extracted human teeth (first maxillary premolar) were collected ( n = 10 for each group). Intact teeth served as the negative control group, and there were six experimental groups: direct composite resin group (positive control); IPS Empress Direct composite (EDC); Feldspathic ceramic, VITABLOCS Mark II (FLD); Leucite glass‐ceramic IPS Empress CAD (LGC); zirconia‐reinforced lithium silicate Celtra Duo (ZLS); and zirconium oxide IPS E.max ZirCAD (ZRC). Disto‐occlusal inlay cavities were prepared in the assigned teeth. For ceramic groups, teeth were scanned using a Trios III intraoral scanner (IOS). Inlays were virtually designed to incorporate a rest seat and then milled. The three‐dimensional (3D) internal and marginal gaps were assessed with a replica technique combined with a second scan of the fit checker applied before inlay cementation. 3D inspection software was used for the superimposition of scans and the calculation of the internal and marginal gaps. Inlay restorations were cemented using a dual‐polymerizing resin cement, then subjected to thermocycling and cyclic loading, followed by load till failure. The internal and marginal gap and fracture load values were recorded and statistically analyzed using One‐way ANOVA with post hoc Tukey test for comparisons ( α = 0.05). Failure patterns were analyzed. Results: The least significant marginal gap was seen with the ZRC group (68 ± 7 µm), while the ZLS group presented the highest marginal and internal gap values (135 ± 9, 199 ± 61 µm), respectively. Internal gap comparison revealed non‐significant differences among the FLD, LGC, and ZRC groups. ZRC group demonstrated significantly the highest fracture load value (1830 ± 97 N). On the contrary, composite resin and FLD groups showed the lowest fracture load in comparison to the tested groups ( p < 0.001). Failure pattern with the ZRC group revealed predominance of tooth failure, as well as adhesive failure associated with debonding of the restoration. LGC and ZLS groups revealed common performance with prevalence of tooth and restoration failure of mixed type, while both direct composite restoration and FLD groups showed predominately cohesive restoration failures. Conclusion: Indirect machinable ceramic surveyed inlays revealed acceptable gap values in addition to outstanding fracture load when compared to direct composite inlays.

Purpose: To measure the effect of daily immersion in varying beverages (distilled water, tea, carbonated beverage, and orange juice) on surface roughness and color stability of 3D‐printed denture base resins.Materials and Methods: 160 acrylic resin discs (15 × 2.5 mm) were made from heat‐polymerized (HP), and 3D‐printed resins (FormLabs, ASIGA, and NextDent). Resin discs (N = 40) were immersed in different solutions (distilled water, tea, carbonated beverage, or orange juice; (n = 10/group)). Surface roughness (R_a, µm) was measured initially (T₀), 6 months post immersion (T₁), and 12 months post immersion (T₂) using a non‐contact profilometer. Color change (∆E₀₀) was calculated using CIEL2000 at T₁ and T₂ using a spectrophotometer. The data were analyzed using Mann‐Whitney U test and Kruskal‐Wallis test in addition to general linear modeling (α = 0.05).Results: Significant differences in surface roughness (R_a) were found between the baseline and immersion in distilled water, carbonated beverage, and orange juice (p < 0.05). HP resin showed increased roughness with all immersion solutions compared to T₀ with the highest value seen at T₁ with tea. ASIGA resin had the highest mean R_a of 1.78 (0.43) after carbonated beverage immersion, while FormLabs resin had the lowest mean R_a of 0.88 (0.06) after distilled water immersion. Tea immersion did not significantly affect R_a among the resins (p > 0.05). Noticeable color changes were observed after immersion in tea, carbonated beverage, and orange juice. All resins exceeded perceptibility and acceptability thresholds at T₁ and T₂. The combined effect of time and resin on color change was statistically significant (p < 0.001), while the combined effects of time/immersion solution, immersion solution/resin, and immersion solution/resin/time were not.Conclusion: Carbonated beverage, tea, and orange juice increase the surface roughness of 3D‐printed resins. Tea, carbonated beverage, and orange juice resulted in noticeable color changes of HP and 3D‐printed denture base resins and this change was time‐dependent.

Purpose: To compare the strength, surface roughness, and hardness of newly introduced permanent three‐dimensional (3D)‐printed resin in comparison with computer‐aided design and computer‐aided manufacturing (CAD‐CAM) milled materials.Materials and Methods: Three 3D‐printed resins (NextDent C&B, Formlabs Permanent Crown, and VarseoSmile Crown plus) and two CAD‐CAM milled (IPS e.max ZirCAD LT and VITA Enamic) resins were used to fabricate discs specimens. A total of 200 disc specimens were fabricated according to manufacturer recommendations. Within each group, half of the specimens were subjected to thermal cycling (5°C–55°C, the 30 s, 5000 cycles). Aged and nonaged specimens were evaluated for biaxial flexural strength (BFS), surface roughness, and hardness. Results were statistically analyzed using analysis of variance (ANOVA) and t‐tests (α = 0.05).Results: Significant differences (p < 0.05) were observed in the BFS, surface roughness, and hardness between the 3D‐printed and milled groups, before and after thermal aging. Overall, the CAD‐CAM milled ceramic group had superior strength, surface roughness, and hardness when compared to all other groups (p < 0.001), except for surface roughness after thermal aging, which was similar in all groups (p = 0.063). Within each group, there was no significant difference (p > 0.05) in surface roughness after thermal aging. BFS values of 3D‐printed materials were statistically similar. In terms of surface roughness, Formlabs specimens displayed the highest value before and after thermal cycling, when compared to other 3D‐printed materials. Regarding hardness, the VarseoSmile Crown plus group demonstrated the highest values compared to other 3D‐printed materials, before and after thermal cycling.Conclusion: Permanent 3D‐printed resins have lower strength than CAD‐CAM milled materials. 3D‐printed permanent resin materials exhibited high roughness and comparable hardness to CAD‐CAM materials. Thermal aging negatively affected the properties of 3D‐printed permanent crowns. Owing to the low strength of 3D‐printed permanent resins, they may not be recommended for clinical practice until further improvements in flexural strength are made to meet clinical standards.

Purpose: The aim of the study was to investigate the effect of surface treatment and repair materials on the flexural strength of repaired 3D‐printed denture base resins after thermal aging.Materials and methods: Bar‐shape specimens (64 × 10 × 3.3 mm) were designed as intact (control) specimens while repair specimens were printed in sections with 2.5 mm space for repair material. Printing was performed with either ASIGA or NextDent denture base material. In each material, one group received no surface treatment, while other repair groups were subjected to one of three surface treatments: (1) monomer application, (2) aluminium oxide particles‐abrasion, or (3) both methods (aluminum oxide particles‐abrasion and monomer application). Pairs were fixed in a customized mold then repaired with either autopolymerizing acrylic resin or flowable composite (n = 9). Repaired specimens were incubated for 48 h at 37°C in distilled water and then subjected to thermal cycling (5000 cycles). A 3‐point bending test was used to evaluate the flexural strength using a universal testing machine, and mode of failure determined followed by fractured surface analysis using scanning electron microscope. Data were analyzed using ANOVA and post hoc Tukey test (α = 0.05).Results: Both resin materials showed a significant decrease in the flexural strength of repaired specimens when compared to control ones (p < 0.001). Groups with no surface treatment had significantly lower flexural strength than those with surface treatment (p < 0.001). Groups treated with monomer application, and with aluminum oxide particles abrasion plus monomer application had similar flexural strength values (p > 0.05), which were higher than those treated with aluminum oxide particles abrasion alone (p < 0.001). Specimens repaired with composite resin showed higher flexural strength than those repaired with auto‐polymerized resin (p < 0.05) however, specimens treated with aluminum oxide particles abrasion alone had similar values for both repair materials (p = 0.95). Adhesive failure was dominant in all repaired groups with auto‐polymerized while cohesive and mixed were dominant with composite repair groups.Conclusion: Surface treatment improved the repair strength of 3D‐printed denture base resins. Using composite resin for repair shows better strength with dominant cohesive and mixed failure suggesting that surface treatment and composite repair are suitable procedures for 3D‐printed denture base repair.

Purpose: To evaluate the effect of different printing orientations and post‐polymerization time with thermal cycling on the translucency of 3D‐printed denture base resins.Methods: Heat‐polymerized (HP) acrylic resin specimens were fabricated and 3D‐printed denture base materials (NextDent, ASIGA, FormLabs) were printed with different printing orientations (0, 45, 90 degrees) and subjected to different post‐polymerization times (15‐, 30‐, 60‐, and 90‐min). All specimens were polished and immersed in distilled water for 1 day at 37°C. CIEDE2000 was used to measure the translucency parameters (TP₀₀) before and after thermal cycling (5000 cycles) recording the color parameters (L^*, a^*, b^*) against a black and white background using a spectrophotometer. k‐factors ANOVA followed by post hoc Tukey's test (α = .05) was performed for statistical analysis.Results: The k‐factors ANOVA test showed a significant effect of resin material, post‐polymerization time, and printing orientation on translucency (p < 0.001). In comparison to HP, all 3D‐printed resins showed lower translucency with all post‐polymerization times and printing orientation (p < 0.001) except FormLabs resin (p > 0.05). For all 3D‐printed resins, the translucency increased, with increasing the post‐polymerization time (p < 0.001) and 60‐ and 90‐min showed the highest translucency. For printing orientation, 90 and 45 degrees significantly showed high translucency in comparison to 0 degrees (p < 0.001). FormLabs showed significantly higher translucency when compared with NextDent and ASIGA per respective printing orientation and post‐polymerization time. The translucency significantly decreased after thermal cycling for all tested resins (p < 0.001).Conclusion: The findings of this study demonstrated that the translucency of 3D‐printed resins is influenced by the printing orientation, post‐polymerization time, and resin type. As a result, choosing a resin type, and printing orientation, with a longer post‐polymerization time should be considered since it may improve the esthetic appearance of the 3D‐printed resins.

The aim of this report was to digitize traditional denture relining using a digital duplication method, in addition to assessing the wear resistance of three‐dimensional (3D) printed denture teeth. A complete denture was relined using light body impression. The denture with impression was scanned yielding a standard tessellation language file that was designed to print the denture base and teeth. The printed teeth were fitted into the sockets of the printed denture base and then bonded using auto‐polymerized acrylic resins, followed by finishing and polishing. Dentures were inserted and fit and occlusion were adjusted as needed, and the patient was scheduled for follow‐up appointments at one week, three months, and six months. At each follow‐up visit, dentures were scanned using a 3Shape E3 desktop scanner and scans were superimposed. The occlusal wear was assessed in reference to the first scan after the denture insertion visit. The accuracy of the intaglio surface of dentures was within clinically acceptable limits. The clinical evaluation of inserted dentures in terms of retention, occlusion, esthetic, and patient satisfaction was encouraging. Using digital duplication, conventional dentures could be relined. The advantages of digital records include eliminating polymerization dimensional changes, and reducing cost and clinical time by minimizing the number of visits, which is particularly helpful with geriatric patients.

Objective The aim of this study was to evaluate the surface roughness, contact angle, and adhesion of Candida albicans to computer-aided designing/computer-aided manufacturing (CAD/CAM) and heat-polymerized (HP) denture base materials. Materials and Methods Specimens were allocated to six groups based on the composition of studied denture base materials, HP acrylic resin, milled resins (AvaDent and IvoCad), and 3D-printed resins (ASIGA, FormLabs, and NextDent). Ten specimens per group were used for each test (n = 10/test). Surface roughness and contact angles were analyzed using profilometer and goniometer, respectively. Adhesion of C. albicans was counted using colony-forming unit (CFU/mL). Means and standard deviations were calculated, and then one-way analysis of variance (ANOVA), followed by Tukey's post hoc test. Correlation of Candida adhesion and surface parameters was determined by using Pearson's correlation analysis. Results No statistically significant difference was noted in surface roughness between HP, milled, and 3D-printed denture base resins except NextDent, which showed significantly higher roughness in comparison to all other resins (p = 0.001). In terms of contact angle, milled resins had the lowest value, followed by HP, ASIGA, and FormLabs, whereas NextDent showed the highest contact angle (p = 0.001). C. albicans adhesion showed no significant difference between all denture base resins. A positive and significant correlation was found between C. albicans adhesion and contact angle (p = 0.003), while no correlation was reported between C. albicans adhesion and surface roughness (p = 0.523). Conclusion Adhesion of C. albicans was similar in all tested specimens. Surface roughness showed no significant difference between all groups except NextDent, which had the highest value. Milled denture base resins had the lowest contact angle among all groups.

The aim of this study was to assess the influences of different CAD/CAM ceramic compositions and thicknesses on the surface roughness and hardness of ceramic restorations. Four different ceramics were used in the current study: lithium disilicate (LD), leucite reinforced (LE), advanced lithium disilicate (ALD), and zirconia-reinforced lithium silicate (ZLS). Each group included 30 specimens subdivided into three different ceramic thicknesses (0.5, 1 and 1.5 mm thicknesses). The microhardness was measured for all the specimens using a microhardness testing machine, while the surface roughness was measured using a non-contact optical profilometer at three intervals (before toothbrushing and after toothbrushing, with and without toothpaste). Three-way and two-way ANOVA were used to determine the factors influencing the surface roughness and microhardness. There was a significant difference in the surface roughness between the studied groups for all the thicknesses. The findings showed that ALD had the lowest surface roughness, while ZLS showed the highest surface roughness. Moreover, ALD, followed by ZLS, had the highest hardness, while LD and LE had the lowest hardness values. Regarding the thicknesses, both the 0.5 and 1 mm ceramic thicknesses showed a significantly lower surface roughness than the 1.5 mm thickness, while the 1.5 mm thickness showed a significantly higher microhardness than the 0.5 mm thickness. The surface roughness and hardness were significantly affected by the ceramic composition and type of filler. It is recommended to use 1.5 mm-thick ceramic materials for the fabrication of definitive full-coverage ceramic restorations, while veneers require 0.5 mm-thick materials. ALD is a promising CAD/CAM material that can be used for the fabrication of restorations with a proper strength in both anterior and posterior regions.

Purpose. Investigate the effect of low nanodiamond (ND) addition and autoclave polymerization on the flexural strength, impact strength, and hardness of polymethylmethacrylate (PMMA) denture base. Methods. A total of 240 heat polymerized PMMA were fabricated with low ND concentrations of 0.1%, 0.25%, and 0.5%, and unmodified as control. The specimens were divided equally into group I: conventionally polymerized PMMA by water bath and group II: polymerized by the autoclave. The impact strength, flexural strength, and elastic modulus were tested using the Charpy-type impact-testing machine and three-point bending test, respectively. A scanning electron microscope (SEM) was used to analyze the fractured surfaces. Surface hardness was measured by a hardness tester with a Vickers diamond. The bonding and interaction between the PMMA and ND particles were analyzed by the Fourier-transform infrared (FTIR) spectroscope. ANOVA and post hoc Tukey test were used for data analysis (α = 0.05). Results. ND addition significantly increased the flexural strength of groups I and II ( , ); it was highest (128.8 MPa) at 0.25% ND concentration for group I and at 0.1% for group II. Elastic modulus increased at 0.1% ND for both groups ( , ), but the increase was statistically significant for group I only. Impact strength showed no significant change with the addition of ND in groups I and II ( , ), as well as surface hardness in group I ( ). Hardness decreased significantly with 0.25%ND in group II. Conclusion. The addition of ND at low concentration increased the elastic modulus and flexural strength of conventionally and autoclave polymerized denture base resin. Autoclave polymerization significantly increased the flexural strength, impact strength, and hardness of unmodified PMMA and hardness of 0.5% ND group.