Showing papers by "Andrea Nóbrega Cavalcanti published in 2007"

Effect of surface treatments and bonding agents on the bond strength of repaired composites.

Abstract: Statement of the Problem: An adequate repair procedure depends on high bond strength between the existing composite and the new composite. Purpose: To evaluate the effect of surface treatments and bonding procedures on the bond strength of repairs performed 24 hours after composite polymerization. Materials and Methods: Composite specimens were stored in distilled water at 37°C for 24 hours. Specimens were allocated into 12 groups (N=10) according to the combination of surface treatment (none, air abrasion, diamond bur) and bonding procedure (none, Single Bond after H3PO4 cleansing, Clearfil SE Bond after H3PO4 cleansing, Clearfil SE Bond without H3PO4 cleansing). The ultimate tensile strength (UTS) of the composite was tested in nonrepaired specimens. Twenty-four hours after repair, specimens were sectioned into three slabs and trimmed to an hourglass shape (1 mm2 area). Slabs were tested under tension and mean bond strengths analyzed with two-way analysis of variance/Tukey and Dunnett tests (α=5%). Results: Two groups resulted in repair bond strengths similar to composite UTS: air abrasion combined with Clearfil SE Bond after H3PO4 cleansing, and air abrasion combined with Clearfil SE Bond without H3PO4 cleansing. Combinations of surface treatments and bonding procedures were not statistically different. Conclusions: When repair procedure was performed 24 hours after composite polymerization, different combinations of surface treatments and bonding procedures affected repair bond strength similarly. There was no statistical difference between the repair bond strength of groups air-abraded and bonded with the self-etching system and composite UTS. CLINICAL SIGNIFICANCE Only air abrasion associated with a self-etching system provided repair bond strength comparable to composite UTS.

Influence of adhesive systems and flowable composite lining on bond strength of class II restorations submitted to thermal and mechanical stresses.

Abstract: The purpose of this study was to evaluate the effect of adhesive systems and flowable composite lining on bond strength to gingival margins of Class II restorations after thermal/mechanical stresses. Proximal cavities were prepared in 90 bovine incisors. Teeth were assigned into nine groups (n = 10), according to the combination of bonding agent [Single Bond (SB), Optibond Solo Plus (OP), Prime & Bond NT (NT)] and layer (1 mm) of flowable composite Filtek Flow (FF) [absent, one layer, two layers]. Materials were applied according to manufacturers' instructions, and FF layers were photoactivated separately. Restorations were concluded with composite resin and were submitted to thermal (1000x, 5-55 degrees C) and mechanical stresses (100,000x, 80 N). For microtensile evaluation, slabs from the gingival bonded interface were obtained, tested under tension, and their failure mode was observed by scanning electron microscopy. Bond strength data were analyzed using two-way ANOVA/Tukey's test. No interaction was observed between adhesive systems and FF lining (p = 0.89). Also, no significant difference was found between bond strength values, whether or not FF layers were used (p = 0.33). However, bonding systems demonstrated significant differences (p = 0.01). SB and NT presented means higher than those observed with OP. Fracture modes varied considerably between experimental groups, and a greater frequency of cohesive failures was noted when FF layers were used.

Effect of salivary contamination at different steps of the bonding process on the microleakage around Class V restorations

Abstract: This study aimed to investigate the influence of the moment of salivary contamination during the bonding procedure (before or after acid conditioning) on the microleakage around composite resin restorations. Sixty bovine incisors received two Class V preparations (one with dentin margins and other with enamel margins). Teeth were randomly assigned into three groups (n=20): 1) control (not contaminated); 2) salivary contamination before etching with 34% phosphoric acid; and, 3) salivary contamination after acid etching. Cavities were restored using Prime & Bond NT (Dentsply) adhesive system and TPH Spectrum (Dentsply) composite according to manufacturer instructions. Teeth were thermocycled (500x, 5-55°C, 60s/bath), immersed in 2% methylene blue buffered solution (pH 7.0), and sectioned into two halves. Three examiners measured the extent of dye penetration on dentin and enamel margins in a stereoscope microscope, using four representative scores. Statistical analysis were performed with Kruskal-Wallis/Wilcoxon tests (α=5%). The results showed that enamel and dentin margins did not present significant differences (p>0.05). However, significantly higher dye penetration was observed on substrates etched and further contaminated with saliva. It was concluded that salivary contamination after acid etching increases the microleakage around composite resin restorations, especially at dentin margins. However, acid etching subsequent to the contamination can avoid negative effects on restorations margins.