Journal of Dental Medicine

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Many different methods are suggested to restore endodontically treated teeth. Prefabricated posts can not be indicated for all teeth and cast posts require extra time and cost. In addition, with the introduction of full ceramic restorations, achieving the ideal esthetic with metal post underneath them may be problematic or impossible because the darkness of the metallic posts may show through the highly translucent all ceramic restorations. In this article the review of litature and describiton of applied methods of different procedure in restoring the root canal therapied teeth and few techniques of non metallic posts fabrication such as fiber reinforced composite and zirconium oxide posts have been described.

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Background and Aim: Considering flexural strength of fiber-reinforced composites (FRC) and also the role of conservative cavities in protecting sound tissue of abutments, the aim of this study was to evaluate the fracture resistance of these bridges by handmade samples in vitro.

Materials and Methods: In this experimental in vitro study, 44 sound newly extracted teeth were used to make 22 fixed inlay bridges including 11 three unit anterior upper inlay bridges substituting clinical model of upper central and 11 three unit posterior lower inlay bridges substituting clinical model of lower first molar. Specimens were prepared with FRC and mounted with artificial PDL in acryl. Cases were exposed to final load by using Universal Testing Machine (Instron 1195) with the speed of 1 mm/min. Statistical analysis was performed by Kolmogorov- Smirnov, independent sample T and Kaplan-Meier tests with p<0.05 as the level of significance.

Results: Based on the statistical tests, the 95% confidence interval of mean was 450-562 N in anterior and  1473- 1761 N in posterior area. Fracture strength was high in the studied groups. Fractures in both groups occurred on composite facing, and the framework remained intact. The highest percentage of fracture in posterior teeth was in the middle of pontic towards the distal connector and in the anterior teeth in the lateral connector, between central pontic and lateral abutment. Using the independent sample T  test a significant statistical difference was observed between two groups (P<0.001). The fracture resistance of anterior samples was lower than the posterior ones.

Conclusion: Based on the results of this study regarding the high fracture resistance in both areas FRC inlay bridges could be recommended for upper anterior and lower posterior teeth in clinical dentistry certainly more studies are needed to ascertain this treatment option.

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Background and Aims: Metal-free and fiber-reinforced composite (FRC) restorations have drawn considerable attention and interest in recent years for restoring in the posterior area due to their improved esthetics. Fracture resistance is one of the most important mechanical properties of materials because of 500-600 N load of occlusion. The restorations should tolerate this load. The purpose of this in vitro study was to compare the fracture resistance of FRC with that of zirconia all-ceramic for posterior partial dentures.

Materials and Methods: Forty extracted human intact teeth (20 first premolars and 20 first molars) selected for fabricating 10 pairs of fiber-reinforced composite and 10 pairs of zirconia all-ceramic bridges. After receiving standard tooth preparation, the teeth were mounted with 7.5 mm distance between each other. The bridges were made and cemented on the teeth. Then the restorations were stored in 37ºC water for 30 days. The fracture resistance was measured using mechanical testing machine with cross-head speed of 1mm/min. Data were evaluated by Independent Sample T test.

Results: The mean fracture resistance in the ceramic group was 1329.41 N and for the F.R.C group was 1118.528 N with significant differences between them (P=0.034). The failure modes were mainly cohesive at pontic area for ceramic samples, but adhesive for FRC samples at pontic area.

Conclusion: Both systems showed sufficient fracture resistance for using in posterior area.

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Background and Aims: The main objective of this study was to determine the effect of polyethylene fibers and veneering composites in fiber-reinforced resin systems on the opacity (contrast ratio).

Materials and Methods: The specimens were divided into four groups. Two groups were used as the control groups, with no reinforcement. The fibers of polyethylene (Fibre-Braid) with special basement composites were used as the reinforced framework materials. Filtek Z250 and GRADIA (shade A2) were used as veneering materials. The total thickness of samples was 3 mm with 13 mm diameter. Specimens were prepared in disk shaped metal mold. The composite materials were light-cured according to their manufacturers' instructions. The contrast ratio (CR) of each specimen was determined on black and white backgrounds using reflection spectrophotometer. Reflectance was measured at intervals of 10 nm between 400 nm and 750 nm. Data were analyzed by two-way ANOVA and Tukey HSD test.

Results: When contrast ratio were compared among the different types of materials statistically significant differences were observed in both veneering composites (P<0.05). The Z250 resin composite had the lowest CR. It was shown that CR tended to decrease as the wavelength of incident light increased from 400 nm to 750 nm. On the other hand, the most differences in CR between groups were found in longer wavelengths.

Conclusion: It was found that polyethylene fibers reduced the amount of the translucency in FRC samples. The results of this study indicate that light reflectance characteristics, including the wavelength dependence, play an important role for the CR of a fiber-reinforced composite.