Curing characteristics of a composite – Part 1: Cure depth relationship to conversion, hardness and radiant exposure

Abstract

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 6 mm diameter, stainless steel molds for 10–40 s and allowing the material to cure for 24 h. 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 12 J/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.

Introduction

Understanding the light-curing characteristics of resin-based composite (RBC) materials is of interest in developing guidelines for clinical use of these materials. It is of particular interest to be able to understand the relationship between degree of conversion (DC) with depth and incident radiant exposure ( H 0 ), and to be able to predict what it will be for differing H 0 values. A relationship for the depth of cure, as defined by the scrape-back depth ( D SB ) for RBC, was provided by Cook , and in simplified form is given as:

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D SB = 1 α [ Log A I 0 t ]
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Nov 25, 2017 | Posted by in Dental Materials | Comments Off on Curing characteristics of a composite – Part 1: Cure depth relationship to conversion, hardness and radiant exposure
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