POLYMERIZATION EFFICIENCY OF CHEMICALLY CURED AND VISIBLE-LIGHT-CUREDORTHODONTIC ADHESIVES - DEGREE OF CURE

The use of light-cured orthodontic adhesives in combination with the n ew generation of ceramic brackets has become popular from an esthetic standpoint. The purpose of this article was to evaluate the degree of cure (DC) of selected light-cured and chemically cured adhesives bonde d to ceramic and stainless steel brackets. The optical properties of e ight types of brackets (single-crystal alumina, polycrystalline alumin a, polycrystalline alumina with polycarbonate base, and stainless stee l) were evaluated by diffuse visible light transmittance spectroscopic analysis. The degree of cure (DC) of a visible light-cured orthodonti c adhesive bonded to these brackets under direct (20 seconds through t he bracket) and indirect (2 x 10 seconds from the incisal and cervical edges of the bracket) irradiation was measured by micro-MIR FTIR spec troscopy. Brackets bonded to a chemically cured, two-paste orthodontic adhesive were used as a control group. According to the results the s ingle-crystal alumina brackets showed the highest diffuse transmittanc e values at 468 nm followed by polycrystalline alumina and polycarbona te-base alumina types. Direct irradiation resulted in low DC values th at were strongly correlated to the diffuse transmittance measurements at 468 nm (r = 0.73, p < 0.05). Indirect irradiation manifested signif icantly higher DC values than direct irradiation in the stainless stee l bracket group, which yielded values comparable to those found in som e indirectly irradiated polycrystalline bracket groups.