Amalgam has been used as a dental restorative material for centuries, but its potential health effects and biopersistance has lead to a decreased use especially in the Nordic countries. New materials have been introduced, partly to replace the mercury containing amalgam and partly because of esthetical reasons. The possible health effects of amalgam have been studied extensively and the material has been replaced with other less well-examined materials during the last few decades. The prevalence of side effects of dental materials is considered to be low in relation to the vast number of dental treatments undertaken. With the introduction of new and more complex materials, side effects related to dental treatment may increase. Epidemiological data suggest that the side effects of dental resins that have almost completely replaced amalgam fillings in Scandinavia, possess a risk for adverse reactions; however, the causal relation has not been fully established. Therefore, the type and extent of side effects caused by resin-based materials are of great interest. The aims of the study were: - to describe the change in health over time for patients with problems related to their dental materials. The hypothesis was that the patients could be divided into subgroups based on their symptoms and that the ability to recover differs between these groups [Paper I]. Furthermore, to determine whether factors such as the replacement of dental restorative materials and follow-up time had any impact on the perceived health. - to assess the long-term development of symptoms and their social consequences among patients referred for diagnosis and treatment of symptoms related to dental materials [Paper II] - to investigate the possible risks with dental restorative materials other than amalgam [Paper III]. - to describe side effects assessed to be caused by resin-based materials that occurred in a group of patients as well as treatment and long-term consequences of the reactions [Paper IV]. A questionnaire was sent to 614 patients [Paper I and II] that had been referred to the School of Dentistry, Umeå, Sweden, with symptoms allegedly caused by dental materials. The questionnaire contained questions on, among others; civil status, present health, medical and dental treatment and other measures and precautions taken because of psychosocial problems related to current employment situation, feelings, self-image and coping behavior. Moreover, information was collected [Paper III] from the Swedish Dental Materials Register 2003 (DentMr), a compilation of MSDS for 487 materials, and information from the user guide of the materials. The Material Safety Data Sheets (MSDS) included in the DentMR were examined regarding the given composition of the products, the occurrence of CAS-numbers and the risk- and safety phrases of the substances. Information was collected [Paper IV] on 36 patients with reactions to resin-based restorative materials from the Swedish National Register of Side-Effects of Dental Materials. Patients with complex symptoms had a more unfavorable long-term prognosis concerning persistent complaints than those with local symptoms only. Furthermore, the results indicate that the patients might experience health improvements after removal of their dental restorative materials. However, the reason for this improvement was unclear. Replacement of dental restorative materials had no significant impact on the ability to recover completely. Our results also indicate a relationship between patients’ self-related health and social consequences in daily life. Those with remaining complex symptoms had more often stopped working or had decreased their work hours because of their symptoms The information about hazards with dental materials seems insufficiently described in MSDS and there might be materials with side effects unknown to both patients and dental professionals. A literature search indicated that some of the listed substances had possible hazards, e.g. substances with embryotoxic and neurotoxic potential. The patients were very heterogeneous; a few with only local symptom free reactions while other had more complex symptoms. The latter group would gain from a multidisciplinary approach, i.e. dental, medical, as well as social and psychological factors have to be considered when developing care management programs for this group of patients. Furthermore, there is a need for stronger regulations of dental materials, such as those applied to pharmaceutical drugs. Finally, it was found that the majority of symptoms suspected to be caused by resin-based materials were local or a combination of local and extra-oral symptoms that appeared within the first 24 hours after treatment. The most frequent adverse effect reported was skin problems/dermatitis. It appears as though immediate reactions to resin based materials are not uncommon and more prevalent than allergic reactions. Still, we have had, difficulties in verifying associations between the dental restorative materials and adverse reactions and also to identify the offending component.