Evaluation of the cytotoxic and genotoxic effects of orthodontic bonding adhesives upon a human gingival papillae through immunohistochemical expression of P53, P63 and P16

BACKGROUND: Numerous in vitro studies have shown that composite materials, commonly used for restorations in conservative dentistry, and in orthodontics to anchor brackets to the tooth enamel, have cytotoxic and genotoxic effects. The study determined expression of p53, p63 and p16, biomarkers useful for predicting potential genotoxicity. PATIENTS AND METHODS: p53, p63 and p16 expression was determined immunohistochemically in the gingival papillae of 99 patients (69 banded orthodontically for at least one year, brackets bonded to teeth with filled flowable composite resin, 30 without orthodontic banding as controls). The papillae samples were removed surgically and examined to evaluate morphological and biological alterations. RESULTS: In no case were morphological alterations visible by microscopy out of the 69 banded patients; four (5.80%) were positive for p53 and two for p63 expression in the basal and suprabasal layers (2.90%). One patient was positive for p16 (1.45%). No control case was positive for any of the biomarkers (0.00%). CONCLUSION: The significance of p53, p63 and p16 positivity, and whether these proteins may serve as biomarkers to predict the risk of developing oral lesions (dysplasia, oral cancer) is still unclear. Although details of the mechanisms leading to cell death, genotoxicity and cell-cycle delay are not fully understood, resin monomers may alter cell function in the oral cavity.