[The in-vivo determination of dosage intensification due to dental alloys in the therapeutic irradiation of the oral cavity].

BACKGROUND

In the course of therapeutic irradiation of regions in the mouth cavity dosage increase due to the emission of secondary electrons in the vicinity of dental materials can be observed. This could induce local destruction of the mucous membrane in contact with metallic dental crowns and fillings. As at now, only rough estimates of this dosage increase could be made with the help of measurements carried out with models.

METHODS

The degree of dosage increase in the immediate surrounding of metallic dental material was measured in an in-vivo study during therapeutic irradiation with 60Co gamma rays in the area of mouth cavity of 11 patients. Measurements were carried out by thermoluminescent dosimetry at permanently fixed golden teeth and alloy specimens containing gold and palladium and amalgam.

RESULTS

The following relative dosage values according to a simultaneously measured reference value were measured at the surface of the different dental materials: 161% near fixed golden caps, 168% near the specimen containing gold in a high percentage, 133% near the specimen of palladium and 161% near the specimen of amalgam.

CONCLUSIONS

The in vivo measured dosage increases due to metallic dental prosthesis are less than values obtained using back scatter arrangements for irradiating phantoms. Despite this, they could be of clinical relevance. Thus the usage of a mucous membrane protection during irradiation with 60Co, as a means of preventing local lesions of the oral mucosa, due to dental alloys within the treatment volume remains inevitable.