Survival analysis of occlusal bite blocks bonded without liquid resin

Abstract

OBJECTIVE: To evaluate the role of mechanical interlocking in the mechanism of enamel adhesion of composite resin in vivo. METHODS: Twenty patients had bilateral occlusal bite blocks bonded on posterior teeth to raise the bite during fixed orthodontic therapy. Depending on the individual clinical situation and enamel quality, the choice of the occlusal surfaces of teeth for the bite blocks included 35o & 45o, 16o & 26o and 36o & 46o. Composite resins (Z100, 3M) were syringed out of the capsules directly onto the acid etched and thoroughly dried enamel surfaces which had no liquid resin applied. The composite resins were light-cured and checked for even contacts between the left and right sides. The service durations of occlusal bite blocks recorded were analyzed by Kaplan Meier product limit method. RESULTS: 37 out of 40 (92.5%) of all the occlusal bite blocks lasted up to the end of their intended treatment purposes. They stayed on average for 36.1 months (range 1.5 to 45.6 months) to completely serve their purposes in this case series. Three out of 40 occlusal bite blocks failed at 1.5, 4.1 and 5.7 months, respectively. The one that failed at 1.5 months was replaced to finish off the treatment. The other 2 bite blocks failed slightly before the treatment finished. They were not replaced. 17 out of 20 patients (85%) experienced no failure of the occlusal bite blocks during their orthodontic treatment. CONCLUSIONS: Composite resin bonds to enamel without liquid resin seems to work well in the clinical context over a prolonged period, even under heavy occlusal stresses. The hypothesis of mechanical interlocking does not seem to have a major role to play in the mechanism of enamel adhesion in vivo.