Antonio Alberto de Cara

Reattachment of rehydrated dental fragment using two techniques

UNLABELLED The reattachment of dental fragments is a conservative treatment and should be considered in the restoration of anterior tooth fractures. This study compared the fracture strength of dehydrated and rehydrated tooth fragments submitted to two different bonding techniques. MATERIALS AND METHODS Sixty human central and lateral mandibular incisors were divided into six groups and sectioned 3 mm from the incisal edge, using a diamond disk. Two reattachment techniques were applied: (a) bonding, using the Single Bond adhesive system and FiltekZ250 composite resin, followed by placement of a chamfer on the fracture line that was filled with composite resin (Groups 1, 3 and 5); and (b) use of the same bonding technique after dentin removal from the tooth fragment (Groups 2, 4 and 6). The following hydration treatments were applied to the fragments before bonding: (a) 48-h hydration (Groups 1 and 2); (b) 48-h dehydration (Groups 3 and 4); (c) 48-h dehydration followed by rehydration 30 min before bonding (Groups 5 and 6). The reattached teeth were mounted in acrylic resin cylinders and stored in distilled water for 24 h. The specimens were fractured at a speed of 1 mm min(-1) in a universal testing machine. RESULTS The following mean fracture strengths (kgf) were recorded: (G1) 12.9 +/- 0.6; (G2) 18.8 +/- 4.8; (G3) 7.3 +/- 1.5; (G4) 15.2 +/- 2.4; (G5) 13.4 +/- 2.2; and (G6) 17.1 +/- 3.2. Analyses using two-way anova and the Tukey test (P < 0.01) revealed significant differences between the restorative techniques and the hydration treatments. CONCLUSIONS The bonding technique that incorporated dentin removal from the fragment before bonding showed greater fracture strength across all groups. Fragment dehydration for 48 h caused a reduction in fracture strength, which was recovered by a 30-min rehydration.

Micro-tensile bond strength to bovine sclerotic dentine: Influence of surface treatment

OBJECTIVE The objective of this study was to evaluate the influence of the surface treatment and acid conditioning (AC) time of bovine sclerotic dentine on the micro-tensile bond strength (micro-TBS) to an etch and rinse adhesive system. MATERIALS AND METHOD Thirty-six bovine incisors were divided into six groups (n=6): G1 sound dentine submitted to AC for 15s; G2-G6 sclerotic dentine: G2-AC for 15s; G3-AC for 30s; G4-EDTA and AC for 15s; G5-diamond bur and AC for 15s; G6-diamond paste and AC for 15s. An adhesive system was applied to the treated dentine surfaces followed by a hybrid composite inserted in increments and light cured. After 24h storage in water at 37 degrees C, the specimens were perpendicularly cut with a low-speed diamond saw to obtain beams (0.8 mm x 0.8 mm cross-sectional dimensions) for micro-TBS testing. Data was compared by ANOVA followed by Tukeys test (p<or=0.05). RESULTS The mean micro-TBS was G1: 18.87+/-5.36 MPa; G2: 12.94+/-2.09 MPa; G3: 11.73+/-0.64 MPa; G4: 11.14+/-1.50 MPa; G5: 22.75+/-4.10 MPa; G6: 22.48+/-2.71 MPa. G1, G5 and G6 presented similar bond strengths significantly higher than those of all other groups. CONCLUSION The surface treatment of sclerotic dentine significantly influenced the bond strength to an adhesive system. Mechanical treatment, either using a diamond bur or a diamond paste was able to improve bonding to bovine sclerotic dentine, reaching values similar to bonding to sound dentine.

Micromorphological and hardness analyses of human and bovine sclerotic dentin: a comparative study.

The purpose of this study was to test the hypothesis that both human and bovine sclerotic dentin have similar hardness properties, in addition to similar micromorphological characteristics. Sixteen teeth (8 human and 8 bovine) exhibiting exposed dentin in the incisal edge and showing characteristics typical of sclerosis were used. Vickers surface microhardness testing was conducted. Three areas of the dentin surface of each specimen were selected. All teeth were processed for scanning electron microscopy in order to estimate the amount (in percentage) of solid dentin on the sclerotic dentin surface. The data were compared by Students t test (α = 0.05). The micromorphological and microhardness data were compared by Pearsons linear correlation test (α = 0.05). The mean percentages of solid dentin of human and bovine sclerotic dentin were similar (human 90.71 ± 0.83 and bovine 89.08 ± 0.81, p = 0.18). The mean microhardness value (VHN) of human sclerotic dentin was significantly higher than that of bovine sclerotic dentin (human 45.26 ± 2.92 and bovine 29.93 ± 3.83, p = 0.006). No correlation was found between the microhardness values and the amount of solid dentin in the sclerotic dentin, irrespective of the species considered (human R² = 0.0240, p = 0.714; bovine R² = 0.0017, p = 0.923; and combined R² = 0.038, p = 0.46). We concluded that although both bovine and human sclerotic dentin present a similar amount of solid tissue, human sclerotic dentin presents higher microhardness than bovine sclerotic dentin.

Resistência à fratura de restaurações diretas com cobertura de cúspide em pré-molares superiores endodonticamente tratados

Endodontically treated teeth are considered more susceptible to fracture because of the loss of tooth structure. The aim of this study was to evaluate the increase of resistance to fracture of upper bicuspids that underwent endodontic access and were restored with composite resin, with cuspal coverage. Forty extracted human maxillary premolars were divided in 4 groups: I--intact teeth; II--teeth with endodontic access and MOD preparation, restored with composite resin, without cuspal coverage; III--teeth with endodontic access, MOD preparation and occlusal reduction, restored with composite resin, with cuspal coverage; IV--teeth with endodontic access and MOD preparation, without any restoration. The test specimens were submitted to compression test up to their fracture. The test of Turkey and the ANOVA analysis were used to compare and test the results. The teeth from group III (with cuspal coverage) presented with significantly greater resistance to fracture, when compared with those from groups II (restored without cuspal coverage) and IV (not restored). The composite restoration with cuspal coverage can be considered an alternative for endodontically treated premolars.