Modulated photoactivation methods: Influence on contraction stress, degree of conversion and push-out bond strength of composite restoratives

Cunha, Leonardo Goncalves; Alonso, Roberta Caroline Bruschi; Pfeifer, Carmem Silvia Costa; Correr-Sobrinho, Lourenço; Ferracane, Jack Liborio; Sinhoreti, Mário Alexandre Coelho

doi:10.1016/j.jdent.2006.10.003

« Previous Next »Journal of Dentistry
Volume 35, Issue 4 , Pages 318-324, April 2007

Modulated photoactivation methods: Influence on contraction stress, degree of conversion and push-out bond strength of composite restoratives

Leonardo Goncalves Cunha
- Department of Restorative Dentistry, Dental Materials Area, Piracicaba, School of Dentistry, UNICAMP Av. Limeira, 901, Bairro Areião, CEP 13414-018, Piracicaba, São Paulo, Brazil
- Corresponding author. Tel.: +55 19 3412 5374; fax: +55 19 3412 5218.
Roberta Caroline Bruschi Alonso
- Department of Restorative Dentistry, Dental Materials Area, Piracicaba, School of Dentistry, UNICAMP Av. Limeira, 901, Bairro Areião, CEP 13414-018, Piracicaba, São Paulo, Brazil
Carmem Silvia Costa Pfeifer
- Department of Dental Materials, School of Dentistry, University of São Paulo, USP, Av. Prof. Lineu Prestes, 2227 São Paulo, Brazil
Lourenço Correr-Sobrinho
- Department of Restorative Dentistry, Dental Materials Area, Piracicaba, School of Dentistry, UNICAMP Av. Limeira, 901, Bairro Areião, CEP 13414-018, Piracicaba, São Paulo, Brazil
Jack Liborio Ferracane
- Department of Restorative Dentistry, Division of Biomaterials and Biomechanics, Oregon Health and Science University, OHSU, 611 Campus Drive, Portland, OR, USA
Mário Alexandre Coelho Sinhoreti
- Department of Restorative Dentistry, Dental Materials Area, Piracicaba, School of Dentistry, UNICAMP Av. Limeira, 901, Bairro Areião, CEP 13414-018, Piracicaba, São Paulo, Brazil

Received 14 July 2006; received in revised form 29 September 2006; accepted 10 October 2006.

Abstract

Objectives

Verify the influence of curing methods on contraction stress, stress rate, and degree of conversion (DC) of a restorative composite and on bond strength of composite restoratives.

Methods

For the stress test, composite (0.84mm thick) was applied between two 5-mm diameter glass rods, mounted in a servohydraulic machine. Stress rate was taken by the value of stress/time at each second. DC was measured by micro-FTIR. Bond strength testing was performed using a push-out test. The C-factor in all tests was 3.0. Four curing methods were tested: continuous light (CL), soft-start (SS), and two pulse delay methods using different initial irradiances—150mW/cm² (PD150) and 80mW/cm² (PD80). Results were analyzed by ANOVA and Tukey's test (α=0.05).

Results

Stress values ranged from 7.9MPa (PD80) to 10.3MPa (CL). No statistical difference was verified among CL, SS, and PD150. PD80 presented statistically lower stress values compared to CL and SS. CL presented the highest maximum stress rate, followed by SS, PD150 and PD80. Mean DC values ranged from 54.2% (PD150) to 55.9% (PD80), with no difference observed among the methods. For the bond strength test, values ranged from 26.4MPa (CL) to 35.5MPa (PD150). PD150 and PD80 were both statistically superior to SS and CL. SS presented statistically higher bond strength compared to CL.

Conclusions

Modulated curing methods were shown to be effective in reducing contraction stress rate and improving the strength of the bonded interface, and without compromising the DC of the restorative composite.

Keywords: Curing methods, Restorative composite, FTIR, Contraction stress, Bond strength, Composite restoratives