The purpose of this study was to estimate the degree of cure (DC) of a ligh
t-cured, and a two- and a one-phase (no-mix) chemically-cured, as well as a
dual-cured commercially available orthodontic adhesive resin. Forty stainl
ess steel brackets were divided into four groups of 10 brackets each, and t
he bracket bases were covered with a standardized volume of adhesive. They
were then pressed firmly onto a yellowish background surface of 75 per cent
reflectance covered with cellulose film to facilitate detachment of the sy
stem and recovery of the set material. The visible light- and dual-cured ad
hesives were photopolymerized by irradiation from the incisal and cervical
edges of the bracket for 10 seconds each, while another group of ceramic br
ackets was used to assess the differential interference of transparent rela
tive to opaque material in the DC. Micro-multiple internal reflectance Four
ier transform infrared spectroscopy was employed for the estimation of the
DC of the adhesives (alpha = 0.05, n = 10), utilizing a method proposed pre
viously. The dual-cured product demonstrated the highest DC followed by the
light-cured combined with the ceramic bracket, and the no-mix and the chem
ically-cured adhesives. The combination of the metallic bracket with the li
ght-cured product resulted in a DC comparable with that of the chemically-c
ured material.