Influence of cutting instruments and adhesive systems on hybrid layer formation.

Influence of cutting instruments and The aim of this study was to analyze the hybrid layer in noncarious dentin prepared by different cutting instruments and restored with composite resin. The cavities were randomly prepared in 40 specimens using a high-speed diamond bur (KG Sorensen 1013) and an ultrasonic tip (CVDentus C22). The cavities were restored with composite resin by varying the adhesive system between the Adper™ Single Bond (2 x 1 system, primer+adhesive) and the Prompt L-Pop™ (3 x 1 system, self-etching). The restorations were hemisected longitudinally and analyzed in the SEM (Scanning electron microscopy) in order to evaluate the hybrid layer and resinous tags characteristics, using scores ranging from 1 to 6. The Pearson test revealed a high correlation coefficient and good significance levels for both intra- and inter-raters values (r=0.90). The data were statistically analyzed using the Mann-Whitney test (P≤0.05). A larger proportion of regular hybrid layers with numerous tags were observed in the dentin prepared using the high-speed diamond burs and restored with a 2 × 1 adhesive system. Alternatively, the 3 × 1 adhesive system promoted the generation of a thin hybrid layer with few tags. After preparation using an ultrasonic tip revealed few or no tags after the preparation and 2 × 1 or 3 × 1 adhesive system application. The high-speed diamond burs produced a dentin surface that was more favorable to restorative material adhesion than the ultrasonic tips, regardless of the adhesive system used.

Evaluation of the dentin-pulp complex after cavity preparation with ultrasonic diamond tip.

AIM: The aim of this paper was to compare the dentin-pulp complex response to cavity preparation in human teeth using ultrasonic chemical vapor deposition (CVD) diamond tip and high-speed diamond bur. METHODS: Class V buccal cavities were randomly prepared in 40 premolars from 14 patients aged 11 to 15 years. The cutting time was recorded and the cavities had the axial walls protected with gutta-percha and were filled with glass ionomer cement. The teeth were extracted at intervals of 0, 5, 10 and 20 days, and were decalcified, sectioned and stained by Hematoxylin & Eosin, Masson's Trichrome and Brown & Brenn techniques. The inflammatory response and cell disorganization were blindly evaluated by two examiners. The remaining dentin thickness (RDT) was measured by a linear scale using computer software. Statistical analysis by one-way ANOVA showed no statistically significant difference (P≤0.05) among the cavities prepared with either type of instrument, with mean RDT of 1132.50 mm. Cutting time and the pulp-dentin complex responses were analyzed statistically by Kruskal-Wallis and Dunn tests (P≤0.05). RESULTS: The ultrasonic CVD diamond tip took 5 times longer to prepare the cavities and there were no typical inflammatory pulp responses in cavities prepared with either type of cutting instrument, only mild to moderate cell disorganization was present. CONCLUSION: Even taking longer to cut the dental substrate, the ultrasonic CVD diamond tip produced similar pulp response compared to the conventional high-speed diamond bur.

Evaluation of the microtensile bond strength of composite resin restoration in dentin prepared with different sizes of aluminum oxide particles, using the air abrasion system.

AIM: The purpose of this in vitro study was to evaluate the influence of the abrasive technique on the microtensile bond strength of composite resin restorations. In addition, any differences in the microtensile bond strength were observed when different aluminum oxide particle sizes were used. METHODS: Flat coronal dentin surfaces were randomly distributed into 3 groups, according to surface treatment: Group A27 Air-abraded dentin with 27 microm aluminum oxide particles; Group A50-Air-abraded dentin with 50 microm aluminum oxide particles; Group HS cut dentin with a #1013 diamond bur in high-speed rotary instrument. After the bonding procedure (Single Bond/Z100), the teeth were stored in distilled water at 37 masculineC for 48 h prior to sectioning. Then, each bonded tooth was longitudinally sectioned producing sticks with a cross-sectional area of 0.81 mm2. The tensile load was applied at a crosshead speed of 0.5 mm/min, until the stick fractured. The data were analyzed by one-way ANOVA and post hoc multiple comparisons using Tukey's test. RESULTS: No difference was observed in composite bond strength when 27 and 50 microm aluminum oxide particles were used for dentin surface preparation using an air abrasion system. However, air-abraded dentin, using 27 microm aluminum oxide particles, demonstrated a higher bond strength when compared to dentin prepared by the conventional method (bur in high-speed). CONCLUSIONS: The air-abraded dentin, using 27 microm alumina powder, demonstrated higher composite bond strength when compared to bur-cut dentin, raising the possibility that this method may increase restoration longevity.