In Vivo Biodegradation of bisGMA and Urethane-Modified bisGMA-Based Resin Composite Materials

The aim of this study was to compare the levels of in vivo chemical degradation sustained by bisphenyl-glycidyl-dimethacrylate (bisGMA)-based and urethane-modified bisGMA-based resin composites. A cohort of 58 patients was recruited for the study. Human salivary esterase activity (HSDE) was measured for each patient prior to restoration placement. Class V or III composite restorations without occlusal contacts were placed in adult patients using a 3-step adhesive (Scotchbond MP, 3M) and 1 of 2 resin composites: a traditional bisGMA-based (Z250; 3M) ( n = 28) or a urethane-modified bisGMA-based composite (TPH Spectra, Dentsply) ( n = 30). Patients followed a 2-min rinse (saline containing 20% ethanol) protocol before, immediately after, and 7 days after restoration placement. The rinse samples were analyzed for the presence of bisphenol A (BPA) and bishydroxypropoxyphenylpropane (bisHPPP), a bisGMA breakdown product, using high-performance liquid chromatography in combination with mass spectrometry. The overall mean ± standard error (SE) HSDE activity was 23.4 ± 1.9 U/mL, with no statistical difference between the Z250 (22.6 ± 2.8 U/mL) and TPH (24.1 ± 2.1 U/mL) groups ( P = 0.69). BPA was not detected from any rinse samples. BisHPPP was detected from both composites only in rinse samples immediately after resin composite placement (0.59 µg/mm² ± 0.16 and 0.68 µg/mm² ± 0.16 for Z250 and TPH, respectively, P = 0.767). There was no statistically significant correlation between HSDE and amount of bisHPPP obtained from the saliva for the Z250 group ( r = 0.071, P = 0.723), TPH group ( r = 0.266, P = 0.155), and both groups combined ( r = 0.080, P = 0.549). Conventional commercial resin composite materials used in the current study did not release any detectable amount of BPA and only showed detectable levels of bisHPPP for a short term after placement, suggesting that hydrolytic consumption of any available resin substrate is fast and the generated products are rapidly diluted below the detection level limit (<20 ppb) in the oral cavity. This short-term release of bisHPPP was not significantly affected by material type or esterase level in the saliva. Knowledge Transfer Statement: This clinical study demonstrated that the duration and degree of biodegradation of 2 representative formulations of resin composites was limited in both duration and amounts of detectable matrix derived degradation products. No significant level of potential biohazards was released following the application of the resin composites. The results of this study can help oral care professionals address concerns from their patients about possible health issues regarding the application of resin composite restorative materials.