Introduction: The aim of this study was to in-vestigate the effect of irradiation duration and distance of light tip to prepared samples in two different light curing unites on the degree of conversion of resin composite. Materials and Methods: Conventional halogen and blue Light emitting diode (LED) units were used for polymerization of an Opalis resin com-posite. The conversion measurements w...

statement of problem: one of the factors affecting the degree of polymerization of light-cured composites is the type of light-curing unit used. in addition, physicomechanical properties of composite resins depend on the degree of conversion and polymerization. objectives(s): since the type of initiator in new composite resins is not explained by manufacturers, this study is an attempt to compa...

OBJECTIVE The aim of this study was to determine the effects of light intensity and type of light unit (quartztungsten-halogen [QTH] or light-emitting diode [LED]) on the hardening of various resin cements and a resin composite restorative. METHODS Disk specimens were prepared from 4 dual-cured resin cements (Variolink II, Calibra, Nexus 2 and RelyX ARC). Two QTH light-curing units (Visilux 2...

PURPOSE The aim of this study was to compare postoperative sensitivity following placement of posterior composite restorations using the fast- or step-curing modes of an LED curing light. MATERIALS AND METHODS Thirty patients participated, with each having two homologous contralateral posterior teeth with Class II carious lesions. One restoration was cured using the fast-curing mode of the LE...

OBJECTIVES Excessive heat produced during the curing of light-activated dental restorations may injure the dental pulp. The maximum temperature excursion at the pulp-dentin junction provides a means to assess the risk of thermal injury. In this investigation we develop and evaluate a model to simulate temperature increases during light-curing of dental restorations and use it to investigate the...

To reduce volumetric shrinkage of the commercially available polymeric dental composite during curing reaction, (2,2-bis [4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) (bis-GMA) derivatives, i.e., (2,2-bis[3-methyl, 4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propan) (DMBis-GMA) and (2,2bis[3,5-dimethyl, 4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) (TMBis-GMA) were sy...

This study evaluated in vitro the pulp chamber temperature rise induced by the light-activated dental bleaching technique using different light sources. The root portions of 78 extracted sound human mandibular incisors were sectioned approximately 2 mm below the cementoenamel junction. The root cavities of the crowns were enlarged to facilitate the correct placing of the sensor into the pulp ch...

The purpose of this study was to examine the effects of LEDs on the polymerization of dental composite resins. Three composite resins and two LED units were used to evaluate the latter's effects on microhardness and temperature rise. In particular, two composite resins contained a coinitiator in addition to camphorquinone (CQ). The emission peak of the tested LEDs matched well with the absorpti...

Delivering an inadequate amount of light to a light-cured resin will result in a resin that is inadequately cured. This study measured the radiant exposure that students delivered to a simulated restoration to determine if instruction with immediate feedback increased the amount of light they delivered. The amount of light (radiant exposure in J/cm(2)) delivered to a simulated restoration by si...

Growing patient demands for esthetics and concerns about environmental contamination by amalgam have led to a large increase in restorations using dental composites. Polymerization of dental composites occurs through a chain reaction that is induced by free radicals. If composite is exposed to air during this process, oxygen in the air decreases the excitability of the photo initiator and stabi...