The Cytotoxic effects of orthodontic bonding materials on cell metabolism

Abstract

Orthodontic bonding materials· are present in the oral cavity, bathed in oral fluids and may be in contact with hard and soft tissues for extended periods of time. Therefore, it is important to be aware of the potential toxicity than can result from the components that may leach out of the materials over time. The purpose of this study was to determine the effects of orthodontic bonding materials and sealants (Phase II w/ fluoride--F, Phase II w/o fluoride--NF, Phase II Dual Cure w/light--DCL, Phase II Dual Cure w/o light-- DCN, Light Bond Sealant--LC, and Phase II Sealant--CC) on cell metabolism. Sample disks were aseptically fabricated according to the manufacturer's recommendations. Eluates of materials were prepared by daily transfer of the discs to fresh culture medium (DMEM + 5% ~S) over an 8-day period. Oral epithelial cells were plated in 96 well plates, and after 24 .h of incubation at 37°C and 5% C02, the cells were fed eluatecontaining medium. After an additional 24 h incubation, viable cell numbers were . determined using the MTS assay. DNA and RNA synthesis were determined by labeling ·the cells with eH] thymidine and uridine, respectively. Medium-containing eluates and radioisotopes were added to pre-plated cells as described previously. The raw data from each assay were converted to percent control values. Multifactor AN OVA ( a.=0.05) and least square means analysis were performed on the DNA, RNA and MTS data to evaluate significant effects of days of elution and specimen types. DNA data from day 1 eluates · showed significant stimulation by all specimen types ( 143.3-176.0%) compared to control (p=0.0001), whereas RNA synthesis assay showed significant inhibition by all materials (28.7-59.5%, p=O.OOOl). MTS data revealed that only Phase II w/o fluoride, Phase II Dual Cure w/light and Phase II Sealant produced significant reduction in enzyme activity with day 1 eluates (90.7, 95.8 and 96.6%, respectively) compared to control (p=O.OOOl). Significant differences between specilnen types and days were also noted on other days for each assay. These results suggest that orthodontic bonding materials may have both inhibitory and stimulatory effects on various aspects of cell metabolism and these reactions are time dependent. (Wilmer Eames Study Club and MCG Biocompatibility Progratn)