Temperature Effects on Pre-cure and Post-cure Properties of Dental Resin Composites

Abstract

Resin-based composites (RBCs) with good aesthetic and mechanical properties have been extensively studied. The successful placement of RBCs mainly depends on their pre-cure properties, which are related to material composition and viscosity. Various strategies, including modifications of the material composition and application of ultrasound energy, have been introduced to reduce viscosity. In accordance with the Arrhenius Equation, pre-heating will reduce viscosity to improve flowability and ease extrusion during handling. Increased monomer mobility also improves the degree of conversion and post-cure mechanical properties [1-3]. However, pre-heating also has potential risks of damaging the dental pulp tissues. This study aimed to investigate temperature effects on the pre-cure and post-cure properties of Viscalor, a thermo-viscous bulk-fill composite and compare it with a wide range of commercial photo-cured RBCs. Viscalor was pre-heated using a Caps Warmer device in T3 mode (at 68 °C) for 30 s and 3 min, respectively. Stickiness and packability were measured via a Texture Analyzer using different experimental settings and temperatures. The extrusion force was determined using a universal testing machine. Regarding post-irradiation properties, FTIR was used to measure the degree of conversion and polymerization kinetics at 5 min and 24 h post-cure. Polymerization shrinkage strain kinetics were measured using the bonded-disk technique. Surface micro-hardness, surface properties after three-body abrasion and static creep behaviour of RBCs were also investigated. Fracture toughness of several bulk-fill composites was measured using a single-edge notch three-point bending method. The measured properties varied with material composition. A 3 min pre-heating period improved pre-cure properties of Viscalor but did not adversely influence its post-cure properties. Interim conclusions recognise the benefits of pre-heating Viscalor for 3 min. However, more research is necessary to investigate the clinical relevance of pre-heated Viscalor.  

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Watts (Supervisor) & Nick Silikas (Supervisor)