Development and characterization of bulk fill dental composite containing elastomeric monomer with different photoinitiators

Author(s)

Mateus Garcia Rocha

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2019-07-29

Examining board members

Américo Bortolazzo Correr; Ivo Carlos Corrêa; Lucas Fernando Tabata; Mario Fernando de Goes; Regina Maria Puppin Rontani

• Advisor: Américo Bortolazzo Correr

Abstract

The aim of this study was to develop and characterize a new bulk fill composite (BFC) containing elastomeric monomer with lower polymerization stress and higher wear resistance. Besides that, evaluate the influence of the beam profile of multi- peak LED light curing unit on the curing efficiency of BFC containing different photoinitiators systems. Therefore, this study was performed in two steps. First, the chemical structure of an elastomeric urethane methyl methacrylate monomer (Exothane 24, Esstech) was characterized using elemental analysis, infra-red spectroscopy and nuclear magnetic resonance. Six BFCs were made containing Exothane 24 (E) or UDMA (U) in three different concentrations (E10, E25 and E50 or U10, U25 and U50). The Vickers hardness as a function of depth was evaluated through each millimeter of each bulk fill increment up to 4 mm. The degree of conversion (DC) was assessed using ATR-FTIR spectroscopy. The flexural strength (FS) and flexural modulus (FM) were assessed by a three-point bending test. The polymerization stress was measured using the universal testing machine with a video extensometer method. Data were analyzed according to the different experimental designs ('alpha'=0.05 and ß=0.2). E25 was the only BFC where no significant statistical difference was found in the VHN from the top up to 4 mm in depth. However, E25 had a lower degree of conversion than U10, U25, U50, and E10. All BFCs had similar flexural strength, except for E50. However, the composites E25 and E50 had lower flexural modulus and polymerization stress. E25 had the lowest volumetric wear loss and wear rate among all BFCs. In the second part, the multi-peak LED (Bluephase G2, Ivoclar Vivadent) was characterized using spectrophotometric and beam profiling analysis. The composite E25 was produced containing equal molar concentrations of either CQ-amine or CQ-amine/TPO. The degree of conversion in depth through, tight-transmittance, polymerization stress and volumetric shrinkage of the BFC were assessed. Data were analyzed according to the different experimental designs ('alpha'=0.05 and ß=0.2). No statistical differences were found between CQ-amine and CQ-amine/TPO for the DC at 4mm in depth and volumetric shrinkage, however, CQ- amine/TPO had higher FM, PS and DC on the top part of the restoration. Thus, the use of elastomeric monomers reduced the PS increased the wear resistance of BFCs. However, the use of CQ-amine/TPO light cured using a multi-peak LED increased the DC only on the top part of the restoration and increased the PS without increasing the DC at 4mm in depth of the restoration (AU)

• FAPESP's process: 16/06019-3 - PHYSICOCHEMICAL PROPERTIES AND WEAR RESISTANCE OF COMMERCIAL AND EXPERIMENTAL BULKFILL DENTAL COMPOSITES BASED ON ELASTOMERIC MONOMER
• Grantee: Mateus Garcia Rocha
• Support Opportunities: Scholarships in Brazil - Doctorate