Patch test reactions to dental materials

Background Patch testing is used when delayed-type hypersensitivity to dental materials is suspected, but no European baseline series exists for patients with suspected allergy to dental materials. Objectives To describe patch test positivity to a 24-allergen dental series, assess the added yield of late readings at D6/7 and characterise methacrylate reactivity patterns. Methods In this retrospective single-centre study, 439 adults referred between 2016 and 2025 for suspected allergy to dental materials were patch tested with an institutional 24-allergen dental series comprising 11 metals, 8 methacrylates and 5 other substances. Reactions were read on D3 and D6/7 and scored by ICDRG criteria. Results Overall, 50.1% of patients had at least one positive reaction, and 41.0% had a positive metal reaction. Nickel (23.0%) and palladium (16.6%) were the most frequent allergens. Amongst methacrylates, HEMA (3.6%), HPMA (3.0%) and EGDMA (2.5%) were most frequent. Amongst methacrylate-positive patients, 44.4% had two or more positive reactions, 40.7% were HEMA-negative and 14.8% were HEMA-negative but HPMA-positive. Across all allergens, 19.8% of positive reactions were detectable only at D6/7, corresponding to a 24.7% relative increase in detection compared with D3 alone. Conclusions Late readings improved detection, and methacrylate reactivity was not fully captured by HEMA alone.