In vivo Biodegradation of Dental Composite Resin

Objectives: To establish methods for reproducibly measuring composite-resin biodegradation products released in vivo.

Methods: Class V composite restorations were placed in adult patients (University of Toronto Research Ethics Reference #15482) using adhesive (Scotchbond MPTM, 3M) and composite-resin (Z250, 3M). Three sets of collection protocols were completed and compared (n=10/group): a two-minute rinse protocol using saline mouth rinse with and without 20% ethanol; 4- and 8-minute rinse protocols with ethanol; and 2-minute rinse with ethanol and concurrent plaque and gingival crevicular fluid (GCF) samples . All samples were collected prior to, immediately after, and 7 days after restoration placement. The samples were analysed for the presence of degradation products using high performance liquid chromatography combined with ultraviolet spectroscopy and mass spectrometry. Independent t-tests and ANOVA with Bonferroni multiple comparisons were used to test for statistical significance (p<0.05). Results: The bisGMA breakdown product, bishydroxypropoxyphenylpropane (BisHPPP), was detected in rinse samples obtained from the oral cavity immediately after composite-resin placement. The ethanol rinse protocol extracted a higher amount (1.01µg/mm²±0.75) than saline alone (0.29µg/mm²±0.36, p=0.017). The 4-minute ethanol rinse extracted significantly less BisHPPP (0.07µg/mm²±0.08) than the 2-minute protocol (p=0.002). There was no difference between the 8- (0.44µg/mm²±0.59) and 2-(p=0.091) or 8- and 4-minute ethanol rinses (p=0.454). The 4- and 8-minute ethanol rinse protocols were subjectively less acceptable to patients than the 2-minute protocol. BisHPPP was not detected in any of the plaque or GCF samples, while it was detected in rinse samples for each of the same patients.

Conclusions: The composite-resin biodegradation product, BisHPPP, is measurable in rinse samples obtained from the oral cavity immediately after composite-resin placement. 20% ethanol in saline rinse with a 2-minute rinse protocol extracted the greatest amount of composite-resin biodegradation products while remaining acceptable to patients. Acknowledgements: CIHR.