A 7-year prospective quasi-experimental study of the effects of removing dental amalgam in 76 self-referred patients compared with 146 controls

Abstract

Background Dental amalgam has been suggested to cause long-term physical and mental problems. Claims that removal of the amalgam may lead to dramatic improvements in health have not been tested empirically in controlled studies with a long follow-up period. Purpose To investigate the long-term effects of removal of dental amalgam on physical and mental symptoms in self-referred patients who complained of multiple somatic and mental symptoms attributed to dental amalgam fillings. Methods In a quasi experimental study, changes in the mental and physical symptoms in 76 patients who had their dental amalgam removed 7 years ago were compared with changes in symptoms among patients with known chronic medical disorders seen in alternative ( n=51) and ordinary ( n=51) medical family practices and noncomplaining patients with similar amounts of dental amalgam fillings ( n=44) seen in an ordinary dental practice. The assessments included written self-reports, a 131-item somatic symptom checklist, Eysenck Personality Questionnaire (EPQ), the General Health Questionnaire (GHQ) and Toronto Alexithymia Scale (TAS). Results Subjects who removed their dental amalgam reported reduced physical and mental symptom load compared to status prior to removal, but only to a level comparable with that reported by the other groups with chronic medical disorders. The dental control group consistently reported lower symptom load during the whole period. In a hierarchical three-step regression model, pretreatment physical symptom load ( P<.01), age ( P<.10) and removal of dental amalgam ( ns) predicted 26% of the variance in posttreatment physical symptom load. Conclusion In a self-referred group of subjects with health complaints attributed to dental amalgam who remove their dental amalgam, the symptom load at follow-up corresponds to the level seen in chronic medical disorders despite the strong implicit placebo effect of the present quasi-experimental design. The finding does not support the hypothesis that removal of dental amalgam will reduce health complaints to normal levels and seriously questions the hypothesis that dental amalgam is an important cause of distress and health complaints.