Shrinkage Stress and Temperature Variation in Resin Composites Cured via Different Photoactivation Methods: Insights for Standardisation of the Photopolymerisation

Author(s)

Sousa, Guilherme dos Santos ^[1] ; Guimaraes, Gabriel Felipe ^[2] ; Marcelino, Edilmar ^[1] ; Petit Rodokas, Jose Eduardo ^{[1, 3]} ; de Oliveira Junior, Arilson Jose ^[2] ; Cesarino, Ivana ^[2] ; Leao, Alcides Lopes ^[2] ; Riccardi, Carla dos Santos ^[2] ; Arjmand, Mohammad ^[4] ; Simoes, Rafael Plana ^{[1, 2]}

Affiliation

^[1] Sao Paulo State Univ UNESP, Med Sch, Ave Prof Mario Rubens Guimaraes Montenegro S-N, BR-18618687 Botucatu, SP - Brazil

^[2] Sao Paulo State Univ UNESP, Sch Agr, Dept Bioproc & Biotechnol, St Jose Barbosa de Barros 1780, BR-18610034 Botucatu, SP - Brazil

^[3] Sao Paulo State Univ UNESP, Sch Engn, Ave Eng Luiz Edmundo Carrijo Coube 14-01, BR-17033360 Bauru, SP - Brazil

^[4] Univ British Columbia UBC, Sch Engn, 3333 Univ Way, Kelowna, BC V1V 1V7 - Canada

• Document type: Journal article
• Source: POLYMERS; v. 13, n. 13 JUL 2021.
• Web of Science Citations: 0

Abstract

The literature has shown that there is no consensus regarding the best resin composite photoactivation protocol. This study evaluated the efficiency of the conventional, soft-start, pulse-delay and exponential protocols for photoactivation of resin composites in reducing the shrinkage stress and temperature variation during the photopolymerisation. The photoactivation processes were performed using a photocuring unit and a smartphone app developed to control the irradiance according each photoactivation protocol. These photoactivation methods were evaluated applying photoactivation energies recommended by the resins manufactures. Three brands of resin composites were analysed: Z-250, Charisma and Ultrafill. The cure effectiveness was evaluated through depth of cure experiments. All results were statistically evaluated using one-way and multi-factor analysis of variance (ANOVA). The use of exponential and pulse-delay methods resulted in a significant reduction of the shrinkage stress for all evaluated resins; however, the pulse-delay method required too long a photoactivation time. The increases on the temperature were lower when the exponential photoactivation was applied; however, the temperature variation for all photoactivation protocols was not enough to cause damage in the restoration area. The evaluation of the depth of cure showed that all photoactivation protocols resulted in cured resins with equivalent hardness, indicating that the choice of an alternative photoactivation protocol did not harm the polymerisation. In this way, the results showed the exponential protocol as the best photoactivation technique for practical applications. (AU)

• FAPESP's process: 17/08188-0 - Study of light intensity variation in photoactivation processes of dental composite resins and their effects to minimize the polymerization contraction
• Grantee: Gabriel Felipe Guimaraes
• Support Opportunities: Scholarships in Brazil - Scientific Initiation