Allergic contact dermatitis in dental laboratory technicians part II: Major allergens and their clinical relevance

Patch testing of dental technicians is difficult due to the big array of dental materials these patients are dealing with daily. Based on the information of major manufacturers a list of substances was compiled and arranged in two series for diagnostic patch testing. After testing with these series on 126 patients in the period of 1995 to 1999 a clear picture of the sensitizers is visible. The major sensitizers in the series 'acrylates' were ethyleneglycol dimethacrylate (EGDMA, 15.9 % positive), 2-hydroxyethyl methacrylate (2-HEMA, 15.1%), 2-hydroxypropyl methacrylate (2-HPMA, 12.7 %), methyl methacrylate (MMA, 9.6 %) and acrylated epoxy oligomer (9.6 %). The high number of positive reactions to EGDMA, 2-HEMA and 2-HPMA is in contrast to their limited usage in dental resin systems. Therefore, the high number of sensitizations can be explained either by technical contamination of other methacrylates or by cross reactivity. MMA is used in nearly all dental resins. Therefore, the clinical relevance of positive patch tests is nearly 100 %. The methacrylates 1,4-butanediol dimethacrylate (BUDMA) and urethane dimethacrylate (UDMA) are used intensively. Due to only 4.8 % of positive reactions to BUDMA and only 3 doubtful reactions to UDMA these substances seem to be weak sensitizers. In the series 'additives' the overall reactivity was much lower except for melamine formaldehyde resin (16.2 %). This resin is used intensively in dental plasters. Most of the reactions showed clinical relevance. For sulfonacid melamine formaldehyde resin, an alternative to melamine formaldehyde resin, positive patch tests were observed in only 2.9 %. Benzoyl peroxide was tested positive in 10.5 % but clinical relevance was very low. Nickel was positive in 26.2 %; although sensitization was due to former contacts with fashion jewellery, 5 cases were considered to be occupationally relevant. Based on the results two series for patch testing of dental technicians can be recommended: the 'major series' contains acrylates and methacrylates (15 materials), the 'additional series' various additives (13 materials).