Effect of reapplication on pull-out bond strength of fibre post to root dentin: An in vitro study.

Purpose: Post removal may be necessary for many reasons and is inevitable after the re-application of a dental post. The present study investigated the bond strength between root dentin and a re-applied fibre-reinforced composite (FRC) post by a pull-out test. Materials and methods: After root canal treatments of 30 extracted human maxillary canine teeth, post spaces were prepared (10 mm), and FRC posts (Hi-Rem Post; Overfibres, Imola, Italy) were luted with self-adhesive resin cement. The samples were than randomly divided into test and control groups (n = 15 in each). The FRC posts were removed in the test group, and new posts were cemented. The pull-out test (1 mm/minute speed) was used to measure the bond strength. Failure types were determined using a stereomicroscope. Mann-Whitney U, chi-square and Fisher-Freeman-Halton exact tests were used for statistical analysis. Results: The bond strength values of the test (119.5 ± 36.86 N) and control (115.55 ± 55.44 N) groups did not differ significantly (p >.05). In terms of the percentage of failure types, there was a significant difference only in the test group between the mixed failure type and the other failure types (p <.05). Conclusions: The re-application of FRC post did not seem to affect the bond strength. The distribution of failure types was similar between the control and test groups.

Effect of Different Universal Bonding Agent Procedures on Repair of Feldspathic and Hybrid Ceramics.

PURPOSE: To perform application of universal bonding agent based only on the manufacturer's instructions for CAD/CAM-manufactured feldspathic and hybrid ceramics and to investigate the bond strength of the composite resin to these ceramics. MATERIALS AND METHODS: A total of 120 samples (2-mm thickness) were obtained from three different CAD/CAM-manufactured ceramics each: a feldspathic ceramic (Vitablocs Mark II), a hybrid ceramic (Cerasmart, GC), and a dual-network ceramic (Vita Enamic). Each of these restorative materials was divided into six subgroups (n = 20 each) in order to apply universal adhesives: All-Bond Universal, Clearfil Quick Universal, Premio Bond, Optibond XTR, Prime&Bond, and Tokuyama Universal Bond. Each bonding agent was applied according to the manufacturer's instructions. Microshear bond strength test was performed at a crosshead speed of 1 mm/min. Two-way analysis of variance (ANOVA) and Tukey post hoc tests were used for statistical analyses. RESULTS: The data suggested a significant impact of bonding agent on all restorative materials applied (P < .001); however, only Prime&Bond demonstrated different effects between materials, with a significant difference between Vitablocs Mark II and Cerasmart restorative materials (P = .001). CONCLUSION: All universal bonding agents provided an acceptable bond strength for each ceramic. Since different universal bonding agents affected the bond strength between ceramics and composite resin, selecting the most suitable bonding agent for each material will increase the bond strength and clinical success.

Comparison of CAD/CAM manufactured implant-supported crowns with different analyses.

BACKGROUND: Present study compared the failure load of CAD/CAM-manufactured implant-supported crowns and the stress distribution on the prosthesis-implant-bone complex with different restoration techniques. METHODS: The materials were divided into four groups: group L-M: lithium disilicate ceramic (LDS, monolithic), group L-V: LDS ceramic (veneering), group ZL-M: zirconia-reinforced lithium silicate ceramic (ZLS, monolithic), group ZL-V: ZLS ceramic (veneering). Crown restorations were subjected to load-to-failure test (0.5 mm/min). Failure loads of each group were statistically analyzed (two-way ANOVA, post hoc Tukey HSD, α = 0.05). Finite element analysis (FEA) was used to compare the stress distribution of crown restorations. RESULTS: Group L-M had the highest failure load (2891.88 ± 410.12 N) with a significant difference from other groups (p < 0.05). Although there was a significant difference between group ZL-M (1750.28 ± 314.96 N) and ZL-V (2202.55 ± 503.14 N), there was no significant difference from group L-V in both groups (2077.37 ± 356.59 N) (p > 0.05). CONCLUSIONS: The veneer application had opposite effects on ceramics, increased the failure load of ZLS and reduced it for LDS without a statistically significant difference. Both materials are suitable for implant-supported crowns. Different restorative materials did not influence the stress distribution, but monolithic restorations reduced the stress concentration on the implant and bone.

Effects of mouthrinses on discoloration of CAD-CAM manufactured restorative materials.

PURPOSE: To investigate the in vitro effect of four different mouthrinses on discoloration of popular CAD-CAM blocks. METHODS: 40 specimens were prepared and then were divided into five groups (n = 8) for each CAD-CAM block (Vitablocks Mark II, IPS e-max CAD, GC LRF, Enamic, Cerasmart). In total, four different mouthrinses for each group (Listerine Zero, Parodontax, Kloroben, Oral B Pro-Expert) and distilled water for the control group were used. The specimens were immersed in 20 ml solution for 2 minutes, twice a day for 21 days with a 12-hour interval. Color changes were measured with a digital spectrophotometer (Vita Easyshade) after 7, 14 and 21 days and specimens were prepared. For statistical analysis, color changes ( ΔE) were calculated and Kruskal Wallis and Wilcoxon tests were used. RESULTS: There was not a significant difference in ΔE1 and ΔE2 values (P> 0.005) while there was a significant one in ΔE3 (P= 0.001) after Bonferroni correction for CAD-CAM materials were carried out as it is independent of the mouthrinse. Listerine Zero brought about the most noticeable color change in all CAD-CAM materials except e.Max after 21 days. CLINICAL SIGNIFICANCE: Discoloration effect of the tested mouthrinses on various CAD-CAM materials was different depending on the usage period. However, these differences did not exceed the clinically perceptible values.

Comparison of radiopacity of current restorative CAD/CAM blocks with digital radiography.

OBJECTIVE: While the radiopacity of restorative material affects the radiographic diagnosis of the teeth, there is no data about the radiopacity of current restorative computer-aided design (CAD)/computer-aided manufacturing (CAM) materials. Therefore, the present study compared the radiopacity values of current restorative CAD/CAM blocks to facilitate the material choice within such a wide variety of materials. MATERIALS AND METHODS: Specimens were prepared from 13 different restorative CAD/CAM blocks to compare with enamel and dentin. The specimens placed on the occlusal phosphor plate were imaged with aluminum step wedge and tooth section. The radiopacity values were calculated using the Image J program. The radiopacity values of the specimens were converted to mmAl values with the Curve Expert 1.4 program. RESULTS: The difference between the radiopacity values of dentin and e.max CAD was not significant, however, they exhibited a significant difference from the other 14 groups (P < .05). Enamel and Obsidien, Suprinity, and Celtra Duo had greater radiopacity values with significant differences from the other 12 materials whereas the difference within these groups was not significant (P > .05). CONCLUSIONS: The evaluated restorative CAD/CAM materials have significantly different radiopacity values. Among these permanent restoration blocks, the highest radiopacity value was observed in Celtra Duo, the lowest in Block HC. CLINICAL SIGNIFICANCE: Cerasmart, Lava Ultimate, Obsidian, Vita Suprinity, Celtra Duo Blocks have adequate radiopacity for inlay, onlay and crown restorations, however, the use of Vita Enamic, Vita Mark II, GC LRF blocks and the others which have lower radiopacity value than dentin for the same kind of restorations depend on the radiopacity of the luting cement for the purpose of recurrent caries detection.

Effect of different mouthwashes on discoloration of plaque-free tooth surfaces.

PURPOSE: To evaluate the tooth discoloration effect of the daily use protocol of six different mouthrinses. METHODS: 70 extracted caries-free central incisors were divided into seven groups (n=10/per group) : Group 1: Curasept Anti Discoloration System; Group 2: CB12; Group 3: Listerine Zero; Group 4: Listerine Cool Mint; Group 5: Colgate Plax; Group 6: Kloroben. The teeth were exposed to the mouthrinse for 2 minutes daily for 3 weeks. Color measurement was performed four times: at the beginning of the study, and after 1, 2 and 3 weeks, with a digital spectrophotometer (Vita Easyshade Advanced). Color changes (ΔE) were calculated and ANOVA and post hoc Tukey's test were used for statistical analysis. RESULTS: Although there was no statistically significant difference between the Colgate Plax and control groups, both groups had a significant difference from the other groups within all ΔE1, ΔE2 and ΔE3 values. CLINICAL SIGNIFICANCE: Among the mouthrinses tested, Listerine Cool Mint group exhibited the most tooth discoloration, while Colgate Plax demonstrated the least noticeable color change.