Orthodontic composite resin bond strength with conventional light and Power Slot curing

OBJECTIVES: the purpose of this clinical trial was to compare the clinical performance of a new composite resin using two different kind of light curing systems, one conventional and one turbo boosted in a split-mouth design, by using both systems for direct bonding of orthodontic stainless steel brackets in every patient. MATERIALS AND METHODS: fifty patients, 32 females and 18 males, of which 13 were adults (> 18 years of age) with fixed appliances were followed for a mean period of 12 months (range 6-16 months). The performance of 1200 steel brackets was evaluated: 600 were bonded with a conventional light curing (Kulzer light curing machine), curing every bracket for 20 seconds using Quick Cure Composite resin (Reliance Orthodontics), 600 were bonded with a new curing light machine (Reliance Ortho 2000 curing light with Power slot), curing every bracket for 6 seconds. Brackets were bonded both on permanent and on deciduous teeth, since many of these patients were growing patients. RESULTS: the conventional light curing recorded an overall failure rate (26 brackets - 4,3%) significantly higher (p< 0.0360) than Power Slot light curing (13 brackets -2,3%). There were no statistically significant differences (p>0.07) between the failure rates in the upper and lower arches with either light curing systems and also in between anterior and posterior areas. A significant difference was evident, however, among the failure rate of upper total and lower total (p<0.0463) brackets bonded with both systems and was more evident in upper arches bonded with conventional curing system (p<0.0170). It was evident also a higher failure rate in the upper arch compared to the lower arch bonded with conventional light (p<0.0269). CONCLUSIONS: the Power Slot light curing was more effective. But both bonding systems failed mainly at the enamel-adhesive interface, without causing damage to the enamel.