Impact of hypo-salivation on severe tooth wear: A ten-year cohort of patients received radiotherapy for nasopharyngeal carcinoma.

OBJECTIVES: This study was conducted to examine the tooth wear status of nasopharyngeal-carcinoma (NPC) patients who had received radiotherapy at least 5-year previously, and to investigate the salivary parameters that may be associated with the tooth wear. METHODS: Tooth wear status of NPC survivors were clinically assessed using the Exact Tooth Wear Index. A tooth was graded to have severe wear when more than one-third of its buccal/occlusal/lingual surface had dentine loss. At the subject-level, percentages of anterior/posterior/all teeth with severe wear were calculated. Age, number of teeth, flow-rate/buffering capacity/pH of stimulated whole (SWS) and parotid (SPS) saliva's were collected. Correlation and multiple-linear regression tests were performed at the significance level alpha = 0.05. RESULT: Sixty-eight participants (mean age of 60.0 +/- 8.9), 697 anterior and 686 posterior teeth were examined with a mean of 10-years post-radiotherapy. Severe tooth wear was found in 63 (92.6 percent) participants, 288 anterior and 83 posterior teeth. The mean percentage of anterior/posterior/all teeth with severe wear were 42.3 +/- 28.1, 14.5 +/- 19.9 and 30.0 +/- 21.7. Anterior teeth, particularly the incisal surface of central incisors were most affected. The mean flow-rate of SWS and SPS were 0.1 +/- 0.1 ml/min and 0.03 +/- 0.07 ml/min respectively. Thirty (44.1 percent) and 48 (70.6 percent) participants were found to have low/no buffering capacity of SWS and SPS respectively. Multiple-regression analyses revealed the SWS flow-rate was associated with the percentage of anterior teeth with severe wear (p=0.03). CONCLUSION: Anterior tooth wear is a significant dental problem among NPC survivors and was associated with hypo-salivation. CLINICAL SIGNIFICANCE: Patients with hypo-salivation should be being monitored for tooth wear particularly on the anterior teeth.