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Bond strengths of Dyract AP compomer material to dentin of permanent and primary molars: phosphoric acid versus non-rinse conditioner.

PURPOSE
The purpose of this in vitro study was to determine the shear bond strengths (SBS) of Non-Rinse Conditioner (NRC, Dentsply) combined with Prime & Bond NT (PBNT, Dentsply), a 1-bottle adhesive. The null hypothesis tested was that the use of NRC with PBNT would not result in SBS different from those obtained with conventional phosphoric acid (PA) etching and bonding application to permanent and primary dentin.


METHODS
Extracted human third molars and primary molars were mounted length-wise in acrylic resin. The occlusal surfaces were ground to expose a flat dentin surface, and then polished to 600 grit silicon carbide paper to create smear layers similar to those created with high-speed burs. The teeth were randomly assigned to 4 groups (N = 10) according to the etchant/conditioner (PA vs NRC) and dentin (permanent vs primary) used: (Group I: permanent dentin, PA, PBNT; Group II: primary dentin, PA, PBNT; Group III: permanent dentin, NRC, PBNT; Group IV: primary dentin, NRC, PBNT). Specimens were then secured in a split mold, having a 5 mm diameter opening and a polyacid-modified resin composite (Dyract AP, Dentsply) were inserted and light cured incrementally onto the treated dentin surfaces. All specimens were stored in water for 24 hours prior to shear strength testing using a Franell testing machine at a crosshead speed of 0.8 mm/minute.


RESULTS
The mean dentin SBS values (MPa) for the groups were: Group I (13.32 +/- 6.6); Group II (15.21 +/- 5.25); Group III (8.87 +/- 3.12); and Group IV (7.42 +/- 2.98). Analysis of variance and Duncan's multiple range tests indicated significant differences among groups at P < 0.05.


CONCLUSIONS
In general, the SBS were remarkably greater in the 2 groups etched with PA in comparison with the 2 groups conditioned with NRC. However, the type of dentin tissue did not influence SBS.