Objectives: To compare the effects of curing direction and type of curing lights on the strength of pre-coated brackets
Methods: Eighty human extracted 1st and 2nd bicuspids were selected and embedded in acrylic resin. The specimens were randomly assigned into 8 groups, (N=10 per group). All specimens were bonded with premolar 80-mesh pre-coated stainless steel orthodontic brackets (APC II, 3M) per manufacturer's instructions. Specimens were cured either from Buccal (B) or Mesial-Distal (MD) directions with Halogen (Demetron 501, Kerr), Plasma Arc (Sapphire, DenMat) and LED (Valo, Ultradent) lights. The groups were: 1) Halogen Buccal; 2) Halogen Mesial-Distal; 3) Plasma Arc Buccal; 4) Plasma Arc Mesial-Distal; 5) LED with standard power mode Buccal; 6) LED with standard power mode Mesial-Distal; 7) LED with plasma mode Buccal; and 8) LED with plasma mode Mesial-Distal. Specimens were then incubated in water (37°C) for 24 hours. Testing was carried out after incubation using Universal Testing Machine (Instron 5566A, Norwood, MA) with cross head speed 1mm/min. Statistical analysis was accomplished with One-way ANOVA, with post-hoc analysis conducted through Tukey-Kramer analysis. Significance for statistical tests was predetermined at p<0.05.
Results:
Group | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
Curing Time (Sec) | 20 | 10 | 6 | 3 | 20 | 10 | 10 | 5 |
Mean (MPa+SD) | 13.57±2.27 | 11.8±2.12 | 10.89±1.28 | 10.42±2.24 | 12.65±3.01 | 14.24±3.35 | 11.9±2.01 | 13.92±3.67 |
Conclusion: Pre-coating orthodontic brackets yielded no effect on the shear bond strength with different curing lights. There was no statistically significant difference in bond strengths of pre-coated orthodontic brackets with different directions and type of curing light.
Sponsored in part by Ultradent, Inc.