Early shear bond strength of a one-step self-adhesive on orthodontic brackets

Objective: The purpose of this study was to determine whether a self-adhesive universal cement, RelyX Unicem (3M ESPE, Seefeld, Germany), can be used successfully to bond orthodontic brackets to enamel. Materials and Methods: Forty human molars were cleaned, mounted, and randomly divided into two groups: 20 orthodontic brackets were bonded to teeth using RelyX Unicem, and 20 brackets were bonded using the Transbond XT (3M Unitex, Monrovia, Calif) adhesive system. The teeth were debonded within 30 minutes after initial bonding using a universal testing machine. After debonding, the enamel surface was examined under 10X magnification to determine the amount of residual adhesive remaining on the tooth. Student's t-test was used to compare the shear bond strength (SBS) of the two groups, and the chi-square test was used to compare the Adhesive Remnant Index (ARI) scores for the two adhesive systems. Results: The mean SBS of the brackets bonded using the RelyX Unicem was 3.7 +/- 2.1 MPa and was significantly lower (t 2.07, P =.048) than the SBS of the brackets bonded with the Transbond system ((x) over bar = 5.97 +/- 4.2 MPa). The comparisons of the ARI scores between the two groups (chi(2) = 17.4) indicated that bracket failure mode was significantly different (P =.002) with more adhesive remaining on the teeth bonded with Transbond XT. Conclusions: The SBS of the self-adhesive universal cement needs to be increased for it to be successfully used for bonding orthodontic brackets.