Effect of proanthocyanidins and photo-initiators on photo-polymerization of a dental adhesive.

OBJECTIVES

To evaluate the effects of proanthocyanidins (PA) and photoinitiator type on the degree of conversion (DC) and polymerization rate (PR) of a model dental adhesive.

METHODS

Three types of photo-initiation systems were introduced into the Bis-GMA/HEMA co-monomer mixture, resulting in four resin formulations including CQ/A (0.5wt% CQ and EDMAB), CQ/A/I-1 (0.5wt% CQ, EDMAB and DPIHP), CQ/A/I-2 (1.0wt% CQ, EDMAB and DPIHP), and TPO (2.1wt% TPO). For each resin formulation, adhesives containing 0%, 2.5%, 5% and 10% of PA with respect to the weight of resin were produced after mixing the resin with various amount of PA/ethanol solution. When light-cured, the RP and DC of each adhesive was determined using ATR-FTIR spectroscopy.

RESULTS

Across and within the initiator groups, the DC followed the general trend of CQ/A<CQ/A/I-1<CQ/A/I-2<TPO and 0-PA>2.5-PA>5-PA>10-PA, respectively. The change of PR with respect to photo-initiation systems and PA content was in a similar but less pronounced pattern.

CONCLUSION

PA hampered the polymerization of all adhesives regardless of photoinitiators used. The initiator formulations CQ/A/I-2 and TPO are better fit for PA-containing adhesives, both leading to >65% DC in the presence of 5% PA.

CLINICAL SIGNIFICANCE

The inclusion of PA in dental adhesives has been limited by its interference with the light-curing of adhesive resins. This study found photo-initiation formulations that could maintain a satisfactory degree of monomer conversion while a significant amount of PA is incorporated.