Comparison of bond strength between orthodontic brackets bonded with halogen and plasma arc curing lights: An in-vitro and in-vivo study

Introduction: This study assessed in-vitro shear bond strength and in-vivo survival rate of orthodontic brackets bonded with either a halogen or a plasma arc light. Methods: Ninety extracted premolars were divided into 6 groups of 15. Stainless steel brackets were bonded to the teeth by using either a halogen light with a 20-second curing time or a plasma arc light with a 2-, 6-, or 10-second curing time. Brackets were debonded either within 30 minutes of bonding or after thermocycling for 24 hours. Bond strengths were tested on a testing machine at a crosshead speed of 1 mm/minute. The bracket failure interface was measured with a modified adhesive remnant index score. Data were analyzed by using ANOVA and Tukey-Kramer multiple comparison tests. For the in-vivo study, a split-arch design was used to determine the bracket-failure rate and distribution in 25 patients. The patients were followed for a mean period of 1.1 years (386 days). Survival analysis was carried out to compare the failure rates of the 2 techniques. Results: No significant differences in bond strengths were found 30 minutes after bonding between the halogen light (13.6 ± 3.8 MPa) and the plasma arc light with 2-, 6-, or 10-second curing times (9.6 ± 2.9, 14.2 ± 4.6, 16.0 ± 3.0 MPa, respectively). Similar bond strengths were also found between the halogen light with a 20-second (16.1 ± 3.6 MPa) curing time and plasma arc light with 6 seconds (18.2 ± 4.6 MPa) of curing time after 24 hours of thermocycling. For the in-vivo study, no significant difference was found in bracket failure rates between the 2 light sources (4.9% in both groups). No significant differences were found between ARI scores for the halogen light and the plasma arc light at either 30 minutes or 24 hours after debonding. Conclusions: These results indicate that the plasma arc light with a 6-second curing time can produce similar bond strength and bracket-failure rates as the halogen light that requires a longer curing time.