Effect of Temperature on the Degree of Conversion and Working Time of Dual-Cured Resin Cements Exposed to Different Curing Conditions

Author(s)

Oliveira, M. ^[1] ; Cesar, P. F. ^[2] ; Giannini, M. ^[3] ; Rueggeberg, F. A. ^[4] ; Rodrigues, J. ^[5] ; Arrais, C. A. ^[1]

Affiliation

^[1] Univ Guarulhos, Dept Operat Dent, Guarulhos - Brazil

^[2] Univ Sao Paulo, Dept Dent Mat, Sao Paulo - Brazil

^[3] Univ Estadual Campinas, Dept Restorat Dent, Piracicaba - Brazil

^[4] Georgia Hlth Sci Univ, Sch Dent, Augusta, GA - USA

^[5] Univ Guarulhos, Dept Restorat Dent, Guarulhos - Brazil

• Document type: Journal article
• Source: Operative Dentistry; v. 37, n. 4, p. 370-379, 2012.
• Web of Science Citations: 26

Abstract

Objectives: This study evaluated the degree of conversion (DC) and working time (WT) of two commercial, dual-cured resin cements polymerized at varying temperatures and under different curing-light accessible conditions, using Fourier transformed infrared analysis (FTIR). Materials and Methods: Calibra (Cal; Dentsply Caulk) and Variolink II (Ivoclar Vivadent) were tested at 25 degrees C or preheated to 37 degrees C or 50 degrees C and applied to a similar-temperature surface of a horizontal attenuated-total-reflectance unit (ATR) attached to an infrared spectrometer. The products were polymerized using one of four conditions: direct light exposure only (600 mW/cm(2)) through a glass slide or through a 1.5- or 3.0-mm-thick ceramic disc (A2 shade, IPS e.max, Ivoclar Vivadent) or allowed to self-cure in the absence of light curing. FTIR spectra were recorded for 20 min (1 spectrum/s, 16 scans/spectrum, resolution 4 cm(-1)) immediately after application to the ATR. DC was calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios precuring and 20-min postcuring as well as during each 1-second interval. Time-based monomer conversion analysis was used to determine WT at each temperature. DC and WT data (n=6) were analyzed by two-way analysis of variance and Tukey post hoc test (p=0.05). Results: Higher temperatures increased DC regardless of curing mode and product. For Calibra, only the 3-mm-thick ceramic group showed lower DC than the other groups at 25 degrees C (p=0.01830), while no significant difference was observed among groups at 37 degrees C and 50 degrees C. For Variolink, the 3-mm-thick ceramic group showed lower DC than the 1-mm-thick group only at 25 degrees C, while the self-cure group showed lower DC than the others at all temperatures (p=0.00001). WT decreased with increasing temperature: at 37 degrees C near 70% reduction and at 50 degrees C near 90% for both products, with WT reduction reaching clinically inappropriate times in some cases (p=0.00001). Conclusion: Elevated temperature during polymerization of dual-cured cements increased DC. WT was reduced with elevated temperature, but the extent of reduction might not be clinically acceptable. (AU)

• FAPESP's process: 08/04970-6 - Pre-heating of dual-cured resin cements during the simulation of indirect ceramic restorations: effects on the degree of conversion after different curing modes
• Grantee: César Augusto Galvão Arrais
• Support Opportunities: Regular Research Grants
• FAPESP's process: 08/07557-2 - Pre-heating of dual-cured resin cements during the simulation of indirect ceramic restorations: effects on the degree of conversion after different curing modes
• Grantee: Michele de Oliveira
• Support Opportunities: Scholarships in Brazil - Master