Retarding Composite Resin Polymerization with Yellow Plastic Food Wrap

Objectives: Dental unit-emitted light can rapidly polymerize highly light-reactive composite resins beyond the point of workability, preventing adequate time for the shaping and sculpting of large direct composite resin restorations. The purpose of this study was therefore to determine if the use of a yellow plastic food wrap over a dental unit light would retard the polymerization rate of a very photosensitive composite resin (Esthet-X, Shade A1, L.D. Caulk). Methods: 0, 1, and 2 thicknesses of yellow plastic food wrap (Reynolds Metals Company) were, in turn: (A) placed in a spectrophotometer and compared for percentage transmission of 470 nm light; (B) placed over a curing unit light wand and compared for mW output on a radiometer; (C) placed over a dental unit light positioned 25 inches away from .2 mm thick composite resin specimens, with FTIR readings then made every 40 seconds to measure degree of composite polymerization; (D) placed over a dental unit light positioned 25 inches away from a direct veneer preparation (clinical simulation) that was then restored by four experienced clinicians who reported working times. Results: (A) 0 sheets, 100%; 1 sheet, 34%, 2 sheets, 6%; (B) 0 sheets, 580 mW; 1 sheet, 190 mW, 2 sheets, 20 mW; (C) Percentage of carbon bonds formed: (at 1m20s) 0 sheets, 8%; 1 sheet, 0.65%; 2 sheets 0.76%; (at 2m00s) 0 sheets, 19.11%, 1 sheet, 12.22 %, 2 sheets, 0.42%; (D) Mean working times: 0 sheets, 34s; 1 sheet, 1m12s; 2 sheets, 2m35s. Conclusions: yellow plastic food wrap placed over a dental unit light markedly extended the working time of a highly light sensitive composite resin in each of four assessments performed. Two sheets of plastic wrap were more than twice as effective as 1 sheet. Performed under USAF Surgeon General-approved Clinical Investigation No. FDG 20020020E.