Shear bond strengths produced by composite and compomer light cured orthodontic adhesives

Objectives: To test the shear bond strengths obtained when orthodontic brackets were bonded ex vivo using a composite resin and a compomer orthodontic adhesive. Methods: Specimens were tested in a special jig made to fit an Instron testing machine. After debonding, the adhesive remaining on bracket bases and enamel surfaces was mapped. Results: Bond strengths ranged from 8 to 23 MPa with the composite resin producing higher strengths than the compomer for similar combinations of variables. Bond strength was increased by longer curing and a longer debond interval and was higher for brackets with mesh bases than undercut bases. More compomer remained on the enamel surface after debonding than did the composite resin. Conclusion: The compomer produced bond strengths within the range considered to be clinically acceptable in other studies. If it was clinically successful as an orthodontic adhesive a compomer would confer the advantage that fluoride release would help to minimize the onset of early caries around bonded brackets.