Inventory and supply control.

In Germany, occupational skin disease (OSD) in dental technicians (DT) has been steadily rising in recent years and causing considerable costs for medical care and rehabilitation. Our objective in this study was to: (i) examine affected workers; (ii) perform patch tests to identify causative agents; (iii) develop strategies of prevention. 7 dental laboratories were inspected as to materials used, working habits, safety regulations, etc. A computer data base was developed for products (trade name, active ingredient, additives, etc.). A questionnaire regarding development of OSD was sent out to 1132 dental technicians (45 questions). 55 DT with suspected OSD were examined and patch tested with the standard series, an extensive series of methacrylates, and own materials. Working conditions, and knowledge of potential hazards, varied greatly in the laboratories visited. The safety data sheets of working materials were of little use and required supplementation by the computer data base, which provided rapid access to allergological information (e.g., type of acrylate, concentration). In the questionnaire (173 answers), 36% reported skin lesions attributed to work and 1/3 suspected plastic materials as their primary cause. Among the 55 DT examined, allergic contact dermatitis was diagnosed in 63.6% and irritant contact dermatitis in 23.6%. Most of the allergens identified (74%) were found in plastic materials (methyl methacrylate (MMA), 9 patients (16%); 2-hydroxyethyl methacrylate (2-HEMA), 18 patients (33%); ethyleneglycol dimethacrylate (EGDMA), 15 patients (27%)). In 16 patients, multiple sensitizations to various methacrylates were found. The fingertips were primarily involved in allergic contact dermatitis (93%), whereas in irritant contact dermatitis, the dorsa of the fingers (especially of the dominant hand) were affected (80%). 9 patients also showed lesions on the face, neck and forearms. The main irritant factors included wet work, contact with plaster, mechanical friction and thermal changes. Based on experience with DT, various preventive measures have been tried and found to be effective (reduction of skin contact, 4H Gloves, etc.). In conclusion, better knowledge of OSD in dental laboratories (in physicians, DT and their employers) would lead to a reduced rate of new cases.

Dental Materials↗

PubMed1995

Fracture toughness determination of dental materials by laboratory testing and finite element models.

This study assessed the effectiveness of finite element analysis in predicting the stress intensity factor (KIC) for three types of dental materials: a glass ionomer, a dental amalgam, and a composite resin. Laboratory tests were conducted on small single-edge notch specimens loaded in three-point bending to determine values for fracture toughness (KQ). Using the dimensions measured for each laboratory specimen, a J integral approach was employed to calculate KIC using finite element analysis. Both two-dimensional plane strain and three-dimensional models were used in determining KIC for each specimen, and these values were compared to the KQ values obtained from laboratory tests. The results indicated that no significant differences existed between laboratory results and those obtained from both two- and three-dimensional finite element models (P > .85). For the three-dimensional model, values for KIC were found to vary across the specimen thickness, with the values at the center of the specimen closely paralleling those obtained from the two-dimensional plane strain model. It was concluded that the two-dimensional plane strain J integral technique was as effective as the three-dimensional technique in calculating values for KIC.

Dental Materials↗