Clinical and pathological characteristics of polymethylmethacrylate and hyaluronic acid in the rat tongue

Adverse effects on the oral mucosa after the use of dermal fillers have been increasingly reported due to their increased use for facial aesthetics. The objective of this study was to evaluate the clinical and histologic effects of two types of product, 10% polymethylmethacrylate and 20 mg/ml hyaluronic acid, locally and at long distance, examining initial and late reactions. Each substance was randomly and separately injected in rats’ tongues (polymethylmethacrylate, n = 16; hyaluronic acid, n = 18). They were compared with the control group (n = 16) at 3 observation times (7, 60 and 90 days) for clinical analysis, intensity of local inflammatory response (haematoxylin and eosin staining), amount of newly formed blood vessels and macrophages (immunohistochemical assays), density of collagen fibres (picrosirius staining) and systemic migration of the product to the liver and kidney (haematoxylin and eosin staining). The results showed inflammation triggered by the injection of the material, suggesting that both substances cause responses in local tissue, although there was biocompatibility with hyaluronic acid. This research highlights the importance of experimental studies on this subject, since adverse reactions have been observed routinely in dental practice.