Degree of conversion of three composite materials employed in the adhesive cementation of indirect restorations: A micro-Raman analysis

Acquaviva, Pier Antonio; Cerutti, Francesca; Adami, Gianmaria; Gagliani, Massimo; Ferrari, Marco; Gherlone, Enrico; Cerutti, Antonio

doi:10.1016/j.jdent.2009.04.001

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Volume 37, Issue 8 , Pages 610-615, August 2009

Degree of conversion of three composite materials employed in the adhesive cementation of indirect restorations: A micro-Raman analysis

Pier Antonio Acquaviva
- Department of Dental Materials and Restorative Dentistry, University of Siena, Italy
Francesca Cerutti
- Department of Restorative Dentistry, Faculty of Medicine, University of Brescia, Italy
Gianmaria Adami
- Department of Restorative Dentistry, Faculty of Medicine, University of Brescia, Italy
Massimo Gagliani
- Department of Restorative Dentistry and Endodontics, Faculty of Medicine, University of Milan, Italy
Marco Ferrari
- Department of Dental Materials, University of Siena, Italy
Enrico Gherlone
- Department of Operative Dentistry, University Vita Salute San Raffaele, Milano, Italy
Antonio Cerutti
- Department of Restorative Dentistry, Faculty of Medicine, University of Brescia, Italy
- Corresponding author at: Department of Restorative Dentistry, School of Dentistry, University of Brescia, P.le Spedali Civili 1, 25123 Brescia, Italy. Tel.: +39 030 3995780, +39 335 284370 (mobile); fax: +39 0381 71006.

Received 3 November 2008; received in revised form 24 March 2009; accepted 3 April 2009. published online 15 April 2009.

Abstract

Objectives

Adhesive luting of indirect restorations can be carried out employing dual- or light-curing materials. This in vitro study evaluated the degree of conversion (DC) of the materials employed in this procedure, seeking how the combination of time and power of curing applied during polymerisation, as well as the temperature of the light-curing composite, influenced the DC.

Materials and methods

One hundred and eighty onlays of different thicknesses (2mm, 3mm, 4mm) were luted with three different composites: two dual-curing cements (Variolink^® II and Calibra^®) and a light-curing composite (Venus^®). The same halogen lamp was used with three different modalities selected to provide a constant quantity of energy. The time/power combinations tested were 400mW/cm² for 120s, 800mW/cm² for 60s and 1200mW/cm² for 40s. The light-curing composite was employed at room temperature and after preheating at 54°C. Each sample was examined in three positions using the Micro-Raman Dilor HR LabRam spectrometer to evaluate the polymer conversion degree. The data were analysed using analysis of variance and the Student–Newman–Keuls test (p=0.05).

Results

The dual-curing materials showed average conversion percentages close to 64%, although onlays thickness clearly influence the degree of conversion, the light-curing composite showed satisfactory results only when onlays thickness was thin, however preheating significantly improved the performance of the light-curing composite under onlays of great thickness.

Conclusions

Optimal luting of indirect restorations is clearly dependent from light source power, irradiation time and dual-cure luting cement or light-curing composite chosen. It should be calibrated for each material to acquire high DCs. Preheating of light-curing only composites allows for the materials to reach optimal conversion degrees.

Keywords: Adhesive cementation, Degree of monomer conversion, Indirect restorations, Micro-Raman analysis, Polymerisation