Use of yellow plastic food wrap to retard composite resin polymerization.

Abstract

Dental chair lights can rapidly polymerize light-reactive composites beyond the point of workability, preventing adequate time for the shaping and sculpting of large direct composite restorations. The purpose of this study was to determine whether yellow plastic food wrap placed over a dental chair light would perceptibly retard the polymerization rate of a light-cured composite (Esthet-X, shade A1, Dentsply/Caulk, Milford, DE, USA). Zero, one, and two thicknesses of yellow plastic food wrap (Reynolds Metals Company, Richmond, VA, USA) were, in turn, used in the following scenarios: (1) placed in a spectrophotometer and compared for percentage transmission of 470 nm light; (2) placed over a curing unit light wand and compared for milliwatts of output on a radiometer; (3) placed over a dental chair light positioned 64 cm from 0.22 mm thick composite specimens, with Fourier Transform Infrared Spectrometry readings made every 40 seconds to measure degree of composite polymerization; (4) placed over a dental chair light positioned 64 cm from a direct veneer preparation (clinical simulation), which was then restored by four experienced clinicians who reported working times. Results for the scenarios were as follows: (1) zero sheets 100%, one sheet 34%, two sheets 6%; (2) zero sheets 580 mW, one sheet 190 mW, two sheets 20 mW; (3) percent conversion at 80 seconds--zero sheets 8%, one sheet 0.65%, two sheets 0.76%; percent conversion at 120 seconds--zero sheets 19.11%, one sheet 12.22%, two sheets 0.42%; (4) mean working times--zero sheets 34 seconds, one sheet 72 seconds, two sheets 155 seconds. Yellow plastic food wrap placed over a dental chair light markedly extended the working time of a light-cured composite in each of four assessments performed. Two sheets of plastic wrap were more than twice as effective as one sheet. The suggested filtering technique with yellow plastic wrap placed over a dental chair light is a highly effective, expedient, and inexpensive method for increasing the working time of light-cured composites.