Shear bond strength of a resin composite to enamel treated with an APF gel.

The purpose of this study was to evaluate the effect of an APF gel treatment on the shear bond strength of a resin composite to enamel. A total of 45 noncarious human extracted permanent molars were used. A flat enamel surface was obtained with 600 grit silicon carbide paper and cleansed with a rubber cup and a water slurry of fine flour of pumice. The teeth were randomly distributed into three groups of 15 teeth each: Group 1: Etched for 30 sec with 37% orthophosphoric acid gel (control); Group 2: APF treatment (Topex gel--Sultan Dental Products, Englewood, NJ) for 1 min and then etched as in Group 1; Group 3: APF gel treatment for 4 min and then etched as in Group 1. After etching, rinsing, and drying, an unfilled resin (XR-Bond--Kerr Manufacturing Co., Romulus, MI) was applied thinly with a brush and cured for 20 sec. A nylon ring (internal diameter: 6.69 mm2) was placed over the area and filled with a light-cured composite resin (Herculite XR--Kerr Manufacturing Co., Romulus, MI). The teeth were thermocycled (x500), mounted in plastic cups and plaster, and sheared with a knife-edged blade in an Instron Testing Machine (Instron Engineering Corp., Canton, MA) running at a crosshead speed of 0.5 mm/min. The results in MPa were as follows: Group 1: 24.88 +/- 6.16; Group 2: 23.20 +/- 5.11; Group 3: 21.29 +/- 8.44. An ANOVA and Student-Newman-Keuls procedure revealed no statistically significant difference among the groups.(ABSTRACT TRUNCATED AT 250 WORDS)