RESUMO
BACKGROUND AND OBJECTIVES: As root filled teeth often have insufficient coronal tooth structure, placement of a post is occasionally necessary to provide adequate retention for the core and final restoration. The aim of the present study was to investigate (i) the impact of post fit (form-congruence) and (ii) the influence of post length on the fracture resistance of severely damaged root filled extracted teeth. MATERIALS AND METHODS: Forty single-rooted human teeth were root filled and divided into four groups (n = 10 per group). Post spaces were prepared with a depth of 6 mm (groups 1, 3) and 3 mm (groups 2, 4). Form-congruence with a maximal fit of the post within the root canal space was obtained in groups 1 and 2, whereas there was no form-congruence in groups 3 and 4. In all groups, glass fiber reinforced composite (FRC) posts were adhesively cemented and direct composite crown buildups were fabricated without a ferrule. Specimens were subjected to thermocycling and cyclic loading followed by application of static load until failure. Loads-to-failure [in N] were compared among the groups. RESULTS: Post fit did not have a significant influence on fracture resistance, irrespective of the post length. Both groups with post insertion depths of 6 mm resulted in significantly higher mean failure loads (group 1: 274.27 N; group 3: 277.16 N) than the groups with post space preparation of 3 mm (group 2: 250.40 N; group 4: 255.48 N). INTERPRETATION AND CONCLUSION: Within the limitations of this study, the fracture resistance of teeth restored with FRC posts and direct resin composite crowns without ferrules was not influenced by post fit within the root canal. These results imply that excessive post space preparation aimed at producing an optimal circumferential post fit is not required to improve fracture resistance of roots.
RESUMO
CONTEXT: Natural antioxidants have capacity to neutralize the action of free radicles, therefore, effective in reversal of compromised bond strength. AIMS: The aim of this study was to investigate the effect of three different antioxidant treatments on the bond strength of composite resin to bleached enamel. MATERIALS AND METHODS: Ninety extracted human anterior teeth were divided into five groups: Group I (n = 10) - control group no bleaching, Group II (n = 20) - bleaching with 35% carbamide peroxide gel, Group III (n = 20): bleaching with application of 10% sodium ascorbate, Group IV (n = 20): bleaching with application of 6.5% proanthocyanidin, and Group V (n = 20) - bleaching with application of 50% Aloe vera. These groups were further subdivided into two subgroups based on whether composite buildup was done immediately (Subgroup A) or after a delay of 2 weeks (Subgroup B). Shear bond strength of the specimens was tested under universal testing machine. STATISTICAL ANALYSIS USED: Data were statistically analyzed using Student's unpaired t-test, ANOVA test, and Tukey's Kramer multiple comparison test. RESULTS: The mean bond strength of Group IVA was significantly higher (4.27 ± 1.86) which indicated that immediate application of proanthocyanidin showed higher bond strength after bleaching (P < 0.05). CONCLUSION: Within the limitations of this study, it can be concluded that immediate application of antioxidants on bleached enamel before composite restoration reversed the bond strength of composite restoration. The immediate application of proanthocyanidin proved superior followed by A. vera.