Light-curing of orthodontic bracket adhesive by transillumination through dentine and enamel

Abstract Bonding properties of light-curing adhesive cured by transillumination through the tooth were compared to those achieved by the conventional technique. The study analyzed the degree of cure (DC%), debonding force (DF) and adhesive remnant index (ARI) when light was transmitted through dental hard tissues. Slices of dentin and enamel of 1？mm in thickness were combined with total thicknesses of 3 or 4？mm to simulate tooth structure without the pulp tissue. DC% with curing time of 20？s, 40？s and 60？s and irradiance power was measured for each group (n？=？5). Brackets were bonded using transillumination on extracted incisors (n？=？6) and premolars (n？=？10), and DF was measured and ARI was scored. No statistical difference was found in light transmission between the simulated samples and incisors (p？>？.05). Increasing the curing time from 40？s to 60？s enhanced the DC% only in premolars (p？<？.05). An adequate DF was achieved through transillumination both in incisors and premolars, but in premolars, the DC% remained low compared to conventionally cured brackets. Most of the bracket failures resulted from weak bracket-adhesive bond