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Objective: The aim of this study was to evaluate the micro-shear bond strength between a dual cured resin cement and five different types of ceramics in composition and techniques of construction, using two different surface treatments. Materials & methods: A total of 50 ceramic disks were made and divided into 5 equal groups according to material type IPS Empress CAD, IPS e.max Press, IPS e.max CAD, Vita Suprinity and PM9 (n = 10). Each group was subdivided into 2 subgroups according to surface treatment they will be subjected to (n=5). Subgroup I: Bonding surfaces were etched with 5% HF acid, then coated with Monobond S. Subgroup II: Monobond Etch & Prime was applied on the bonding surfaces. For standardization of bonding surface area, 5 plastic tubings distributed on the bonding surface of each disk were used to place the dual resin cement. The samples were then subjected to micro-shear bond strength. Results: Results showed insignificant difference in micro-shear mean values between the IPS Empress CAD subgroups while significant differences were found between the other subgroups within the same group. Monobond Etch & Prime surface treatment resulted in higher micro-shear bond strength compared with HF surface treated subgroups for all the tested materials except for the PM9 and IPS e.max CAD. Conclusions: It was found that ceramic microstructure as well as the fabrication technique affects the selection surface treatment type. Also, Monobod Etch and Prime as a single step surface treatment produced clinically accepted and comparable results to that of HF treatment.

Statement of the problem:The wide use of digital dentistry in fixed prosthodontics using 3D printers and CAD/CAM in fabricating crowns and partial fixed dental prosthesis created a need for more information about their marginal gap and internal fit.Purpose: This study aimed to evaluate the effect of fabrication technique using CAD/CAM manufactured and heat pressed lithium dislicate crowns made from milled wax and 3D printed resin patterns on their marginal gap and internal fit. Material & Methods:A total of 50 prepared mandibular first molar resin models were used and divided into two main groups according to their fabrication phase: Patterns group and fully fabricated crowns group. Patterns group was subdivided into milled wax patterns (W) (n=10) and 3D printed resin patterns (P) (n=10). Fully fabricated crowns group was subdivided according to fabrication technique of lithium disilicate crowns into: Machinable ceramics (M), using IPS e-max CAD blocks (n=10), Pressable ceramics (Pw), using IPS e-max press ingots following wax milling (n=10) and Pressable ceramics (Pp), using IPS e-max press ingots following 3D resin printing (n=10). All patterns and ceramic crowns were cemented with Rely-X self-adhesive resin cement. Marginal and internal adaptations were measured using SEM at 300 × magnification. Kruskal-Wallis and Wilcoxon signed-rank tests were applied to compare between the groups. Data were presented as median and range values. The significance level was set at P ≤ 0.05.Results: P group showed a significant higher median total marginal gap of 111.4 μm (80.8-139.7) than W group of 51.3 μm (45.1-57.8) before heat pressing. While M group showed the significant highest median marginal gap of 138.4 μm (83.4-191.8) and no significant difference between heat pressed groups (Pw and Pp) (P ≤ .05). Regarding changes after heat pressing, Pw group showed no significant decrease, while Pp group showed a significant decrease in median total marginal gap. For internal fit, there was no significant difference between the pattern groups (2780)

Purpose To verify whether 3D surface deviation analysis software can detect the surface changes of composite veneered polyetheretherketone posterior crowns following wear simulation compared to optical digital profilometry. Materials and methods Twenty dental crowns, fabricated from CAD‐CAM polyetheretherketone (PEEK) and veneered with high impact polymer composite (HIPC), were subjected to wear test (50N, 5/55°C; 120,000 chewing cycles). Optical digital profilometry and 3D surface deviation using Geomagic design X software was used before and after the wear test to measure volumetric wear loss (mm3). The data were statistically analyzed with Wilcoxon signed‐rank test to compare the two methodologies. The significance level was set at p ≤ 0.05. Results There was no statistically significant difference between the two assessment methods (p‐value = 0.075, Effect size = 0.854). Regarding the optical digital profilometry analysis, HIPC veneered PEEK crowns showed 0.01686 (0.018‐0.02155) mm3 as a median volumetric wear loss value. While the crowns analyzed by 3D surface deviation showed –0.0398 (–0.0913 to –0.0042) mm3 as a median volumetric loss value (p‐value = 0.075, Effect size = 0.854). In addition, there was no statistically significant correlation between wear measurements by optical digital profilometry and 3D surface deviation analyses (ρ = –0.177, p‐value = 0.685). Conclusions There was no significant difference or correlation between optical digital profilometry and 3D surface deviation analyses for volumetric wear loss of veneered PEEK crowns.

Statement of problem: Veneered polyether ether ketone (PEEK) is a recent alternative choice for fixed dental prostheses. There is a lack of data about the color stability of veneered CAD/CAM PEEK crowns using different veneering composite techniques. Purpose: To verify the effect of thermocycling and different mouth rinses on color stability of CAD/CAM composite versus conventional nanohybrid composite veneered PEEK crowns. Methods: Forty-two duplicated epoxy resin dies of prepared mandibular first molar to receive a ceramic crown were fabricated. 42 CAD/CAM PEEK cores were fabricated and divided into two groups (n=21) based on the veneering technique; group (C): nanohybrid crea.lign composite veneered PEEK cores (control) and group (H): HIPC veneered PEEK cores. Each group was further subdivided based on the mouth rinse into 3 groups (n=7): Listerine-alcohol free, Hexitol and Distilled Water (control). The color at baseline, after thermocycling equivalent to clinical 6 months service and 1-week immersion in mouth rinses were measured utilizing a spectrophotometer. The data were statistically analyzed using ANOVA, pair-wise Tukey's post-hoc and student t-tests to reveal the significance between groups (P ≤ 0.05). Results: All specimens showed visually unperceptible color differences after thermocycling and immersing in mouth rinses (∆E*<3.3). Based on material, C group showed statistically significant higher color change values than H group. ANOVA test revealed that the highest color change was for Hexitol followed by Listerine then Distilled Water (p=<0.0001<0.05). Tukey's post-hoc test showed a non-significant difference between Hexitol and Listerine. The interaction between the effect of mouth rinses and type of veneering composite materials was statistically non-significant for C group (P>0.05) while significant for H group (P<0.05). Conclusions: Although visually nonperceptible, HIPC or nanohybrid composite veneered PEEK crowns showed a color difference after thermocycling and immersion in different mouth rinses.