Changes in caries resistance by irradiation

Abstract

In patients undergoing radiation therapy, the likelihood of caries becomes high because of the reduced saliva secretion and changes in its composition in response to the radiation. Another cause is the possibility of radiation therapy having direct effects on the dental hard tissues, which is controversial. This study examined whether caries resistance in teeth was changed because of the alteration of the physical properties of the enamel, cementum and dentin surfaces after radiation therapy. For this, using 60 extracted teeth, this study examined whether the caries resistance of the crown and the root prior to irradiation was different from after irradiation by measuring the depth, area of caries, and the density of caries. In addition, to investigate methods for improving the caries resistance, the teeth surface were treated with fluoride varnish, 1.1 % NaF, 5 % hydroxyapatite (HA) and chlorohexidine under a range of conditions prior to irradiation, and the change in caries resistance was examined. To examine the effective methods for treating the tooth with caries developed after irradiation, caries was induced artificially, treated with fluoride varnish, 1.1 % NaF, or 5 % hydroxyapatite (HA), and the remineralization pattern was examined.The difference in caries with or without radiation was compared. A polarized microscopy examination showed that more caries developed after irradiation (p<0.05). Moreover, the caries resistance of the cementum area of the root area was enhanced when fluoride varnish (Cavity Shield, 3M/ESPE. St Paul. MN. U.S.A) was applied and subsequently irradiated (p<0.05). When the remineralization capacity was examined after the induction of artificial caries, remineralization was achieved successfully in the group without irradiation using fluoride varnish. On the other hand, remineralization could not be achieved in the irradiation group regardless of the treatments.