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A Journal on Dentistry and Maxillofacial Surgery
Minerva Stomatologica 2009 January-February;58(1-2):1-8
language: English, Italian
Indirect resin composite restorations: evaluation of polymerization of luting agents by means of micro-Raman spectrophotometry
Acquaviva P. A., Vieno S. 1, Madini L. 1, Barabanti N. 1, Gagliani M. 3, Bollero P., Cerutti A. 4
1 School of Dentistry University of Brescia, Brescia, Italy
2 Department of Mechanical and Industrial Engineering University of Brescia, Brescia, Italy
3 School of Dentistry University of Milan, Milan, Italy
4 Head of Restorative Department School of Dentistry University of Brescia, Brescia, Italy
Aim. The degree of conversion of a luting composite cement influences its clinical performance. Aim of the study was to evaluate the degree of conversion of 4 different composite cements by means of micro Raman spectrophotometry.
Methods. Forty-four cylindrical onlays of different and defined thickness (1, 2, 3, 4 mm) were built using a custom made template. The onlays were made in composite material (Signum, Heraeus; shade A 3,5) and cemented onto a glass plate with different luting materials: dual curing (Variolink II, Calibra) and light curing (Venus flow, Tetric flow). The lamp tip was shielded in order to have the light reach the cement only through the onlay. Samples were divided into 12 groups (N.=3), differing in onlay thickness and luting material. Each sample was examined in three spots by a micro-Raman spectrophotometer (Dilor Hr-Labram). The conversion degree was evaluated by analyzing the variations in intensity of the 1 638 cm-1 aliphatic peak (C=C), characteristic of all Bis-GMA containing materials, related to the invariant 1 608 cm-1 (C-C of the aromatic ring).
Results. All materials show good polymerisation results below 1 mm and 2 mm onlays. Below onlays thicker than 3 mm a constant degree of conversion throughout the surface of samples could not be found: spots with satisfactory polymerisation and spots with insufficient polymerisation were found.
Conclusion. Onlay thickness has a key role in cement conversion. The thicker the onlay, the less predictable the conversion.