Use of yellow plastic food wrap to retard composite resin polymerization

Background: 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. Purpose: 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). Materials and Methods: 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: 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. Conclusions: 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.