Elution of leachable components from resin composites after plasma arc vs. standard or soft-start halogen light irradiation

Abstract

Objectives. To determine the release of leachable components from resin based composites (RBC) after plasma arc vs. standard or soft-start halogen curing. Methods. The tested RBC were the fine hybrids Herculite XRV (Kerr), Solitaire 2 (Kulzer) and Z250 (3M), the micro-fill Silux Plus (3M) and the polysiloxane-containing Definite (Degussa). The irradiation protocols included halogen standard irradiation at three different intensities (TriLight, ESPE), ramp curing (dito), step curing (HiLight, ESPE), pulse polymerization (VIP Light, BISCO) and plasma curing (Apollo 95E, DMDS; PAC Light, ADT). Initial solubility was determined applying RBC into simulated cavities (molds of 6 mm inner diameter and 2 mm height fabricated from pressed ceramics) and eluting 24 h in demineralized water at 37 °C. Medium-term solubility was evaluated using plain RBC specimens of equivalent dimensions stored dark (37 °C, 24 h) and extracted in 50% CH 3OH (37 °C, 72 h). After drying the specimens to constant weight, solubility and sorption were determined gravimetrically. Results. Medium-term solubility/sorption were higher than initial ones. Irradiation at reduced intensity increased solubility and sorption, whereas ramp curing, step curing and pulse polymerization (for most materials) maintained low values. Plasma arc curing worked well for Z250 and Herculite XRV, compared to medium or low intensity halogen irradiation for Silux Plus and Definite and produced moderately (PAC Light) or very (Apollo 95E) high solubility for Solitaire 2. Conclusions. Reducing irradiation intensity does and soft-start protocols do not compromise solubility and sorption. The efficiency of plasma arc curing depends markedly on the types of photo-initiators used.