Curing characteristics of a composite - part 1: cure depth relationship to conversion, hardness and radiant exposure.

Objective: As the first part of a larger study on curing characteristics of a resin-based composite (RBC), the major objectives were to create an energy-hardness relationship (EHR) that relates Knoop hardness (KHN) with radiant exposure (H), and to do the same for degree of conversion (DC) in the form of an energy-conversion relationship (ECR). Both of these are meant to be universal relationships that satisfy reciprocity between irradiance and time for a given H value.
Methods: RBC specimens were made by curing the material in 6mm diameter, stainless steel molds for 10-40s and allowing the material to cure for 24h. Cure depths were determined by a scrape-back method. KHN and DC values were determined along the central axis of the specimens, and these values were related to the internal H values using a measured transmission relationship, T(d), for the RBC.
Results: Suitable EHR and ECR relationships were developed for the RBC material that can be used to describe the curing characteristics under various curing conditions. However, predictive accuracy is affected for incident radiant exposures below about 12J/cm(2) to some extent. A relationship between KHN and DC was established.
Significance: For the RBC examined, KHN measurements can be used as an alternate method or in conjunction with DC for describing the curing characteristics.
(Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)