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.

Polymerization efficiency of curing lamps: a universal energy conversion relationship predictive of conversion of resin-based composite.

A universal energy-conversion relationship (ECRu) predictive of conversion of a resin-based composite (RBC) polymerized with any light source has been described. This relationship was derived from an energy conversion relationship for RBC polymerized with a tungsten-halogen lamp and the lamp's efficiency relative to a hypothetical standard lamp. The ECRu was then used to predict conversion throughout RBC polymerized with an LED lamp using the lamp's relative efficiency compared to the standard lamp.

An energy conversion relationship predictive of conversion profiles and depth of cure for resin-based composite.

Predicting the polymerization throughout resin-based composite (RBC) has been reduced to a set of variables involving irradiance of the light source, exposure duration and RBC transmission properties, together with an energy-conversion relationship (ECR) derived from Fourier Transform Infrared Spectroscopic analysis (FTIR) of a single shade of photo-polymerized RBC. The ECR describes the localized energy density required to achieve a desired conversion independent of shade. Using this ECR, conversion was predicted and experimentally verified throughout different opacities of RBC based on knowledge of their transmission properties and the incident radiant energy density (irradiance times exposure time).

The effect of filler and silane content on conversion of resin-based composite.

Objective: This study examines the influence of filler loading and silane content on the conversion of photoactivated, resin-based composites as determined using Fourier transform infrared spectroscopy (FTIR).

Method: Zirconia/silica filler was processed with a silane coupling agent (gamma-methacryloxypropyltrimethoxysilane) to achieve a range of silane-to-filler compositions. Treated fillers were compounded with a photoactivated BisGMA/TEGDMA resin to yield a series of pastes all containing 72 wt% total solids.

Energy dependent polymerization of resin-based composite.

Objective: This study explores the relationship between the extent of polymerization and the radiant energy (dose) applied during the photopolymerization of resin-based composites.

Method: FTIR was used to measure the 5-min and 24-h conversion of four resin-based composites prepared in a thin film and polymerized under conditions of decreasing intensity and a constant exposure time (30s) using a tungsten halogen curing light. The measured conversion was obtained over a wide range of applied radiant energy.