The effectiveness of different polymerization protocols for class II composite resin restorations

de Jong, Lieke C.G.; Opdam, Niek J.M.; Bronkhorst, Ewald M.; Roeters, Joost J.M.; Wolke, Joop G.C.; Geitenbeek, Bas

doi:10.1016/j.jdent.2007.02.002

« Previous Next »Journal of Dentistry
Volume 35, Issue 6 , Pages 513-520, June 2007

The effectiveness of different polymerization protocols for class II composite resin restorations

Lieke C.G. de Jong
- Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, P.O. Box 1901, 6500 HB Nijmegen, The Netherlands
- Corresponding author. Tel.: +31 24 3616410; fax: +31 24 3540265.
Niek J.M. Opdam
- Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, P.O. Box 1901, 6500 HB Nijmegen, The Netherlands
Ewald M. Bronkhorst
- Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, P.O. Box 1901, 6500 HB Nijmegen, The Netherlands
Joost J.M. Roeters
- Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, P.O. Box 1901, 6500 HB Nijmegen, The Netherlands
Joop G.C. Wolke
- Department of Periodontology and Biomaterials, Radboud University Nijmegen Medical Centre, P.O. Box 1901, 6500 HB Nijmegen, The Netherlands
Bas Geitenbeek
- Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, P.O. Box 1901, 6500 HB Nijmegen, The Netherlands

Received 27 September 2006; received in revised form 2 February 2007; accepted 12 February 2007.

Abstract

Objectives

To investigate the effect of reduced light exposure times on Vickers hardness (VH) of class II composite resin restorations.

Methods

Class II restorations were made in vitro in three 2mm thick increments in a human molar. Two composite resins (Clearfil AP-X; Esthet-X) were polymerized with four light-curing units (Halogen; Astralis 10, LED; The Cure, L.E.Demetron I, Smartlite) following four curing protocols. Three protocols with exposure times of 10s, 20s or 40s (control) per layer. In the fourth protocol, 10s irradiation per layer was combined with additional lateral curing for 10s from buccal and palatal after removal of the metal matrix. VH of the axial surface was determined at top and bottom layers directly after light-curing and after 7 days storage. Linear regression analysis was performed to analyze the effect of protocol variables.

Results

Directly after light-curing VH of both composite resins was significantly influenced by curing protocols. After 7 days, curing protocols had no significant effect on VH of Clearfil AP-X, except for the Smartlite. VH of Esthet-X was still influenced by curing protocol, but differences were smaller than directly after light-curing.

Conclusions

With high intensity light-curing units, exposure times of 10s/2mm increment can be sufficient to obtain under in vitro conditions a high degree of conversion, depending on materials and curing protocols. With additional lateral curing of a class II composite resin restoration a higher degree of cure can be obtained in less time.

Keywords: Dental material, Polymerization, Degree of conversion, Composite resin, Curing light, Hardness