Laboratory evaluation of a self-etching primer for orthodontic bonding

The aim of the present study was to compare the mean bonding time, mean shear bond strength and mean survival time of stainless steel brackets with a micro-etched base bonded with a light-cure composite using a self-etching primer (SEP) or a conventional two-stage etch and prime system. Brackets were bonded to 30 premolars with each bonding system. The bonding time was recorded for each specimen using a stopwatch. After storage in a humidor at 37degreesC for 24 hours, the shear debonding force was measured at a crosshead speed of 0.5 mm/minute. Another 10 premolars were bonded with each bonding system and used to assess survival time following the application of mechanical stress in a ball mill for 100 hours. The mean bonding time of the SEP group (111.5 seconds) was significantly less than that of the two-stage bonding group (170.5 seconds) [mean difference 59 seconds; 95 per cent confidence interval (CI) 51.8-66.2 seconds, two sample t-test P < 0.001]. The mean shear bond strength of the SEP group (2.88 MPa) was significantly less than that of the two-stage bonding group (3.71 MPa) (mean difference 0.83 MPa; 95 per cent CI 0.23-1.42 MPa; two sample t-test P = 0.008). For the survival study, only one of the two-stage bonding group failed within 1 hour in the ball mill. The SEP significantly reduced bracket bonding time. The mean shear bond strength of the brackets bonded with the SEP was significantly less than those bonded with a conventional two-stage etch and prime system. There was no difference in survival time of brackets bonded by each bonding system.