Effect of changing application times on adhesive systems bond strengths

To examine and compare the effect of increasing the priming time and the adhesive resin pre-curing time on shear bond strength of new dentin bonding systems (DBS).

Two multi-step/total etch DBS, Scotchbond Multi-Purpose Plus (SBMP+) and OptiBond FL (OB FL), and one one-bottle/total etch DBS, Single Bond (SB), were used. One hundred flat dentin specimens were prepared from extracted human molars. Approximately 1 mm of dental structure was ground to expose superficial dentin. The specimens were randomly assigned to the three DBS, and minimum of five specimens were used for each test condition. For each multi-step DBS, 40 specimens were divided into four groups with priming times of 10, 20, 30, and 40 seconds. Each group was further subdivided into two subgroups with adhesive resin pre-curing times of 20 and 40 seconds. The SB specimens were divided into four subgroups with a waiting time of 10, 20, 30, and 40 seconds before drying and curing of its one-bottle adhesive. Shear bond strength tests were performed using a universal testing machine (Instron) at a crosshead speed of 0.5 mm/minute. Results were analyzed using ANOVA and Duncan's multiple range tests.

For the multi-step DBS, increasing the priming time up to 30 or 40 seconds caused a significant increase in the mean shear bond strength values (P < 0.0001). Lengthening the adhesive resin pre-curing time did not cause any significant increase (P = 0.05) in the mean shear bond strength values except with 30-second and 40-second priming times. For SB, increasing the one-bottle adhesive waiting time before drying and curing to 30 seconds resulted in a statistically significant increase (P < 0.002) in the mean shear bond strength.