The influence of parotid gland sparing on radiation damages of dental hard tissues

The aim of the present study was to evaluate whether radiation damage on dental hard tissue depends on the mean irradiation dose the spared parotid gland is subjected to or on stimulated whole salivary flow rate. Between June 2002 and October 2008, 70 patients with neck and cancer curatively irradiated were included in this study. All patients underwent dental treatment referring to the guidelines and recommendations of the German Society of Dental, Oral and Craniomandibular Sciences prior, during, and after radiotherapy (RT). During the follow-up period of 24 months, damages on dental hard tissues were classified according to the RTOG/EORTC guidelines. The mean doses (D (mean)) during spared parotid gland RT were determined. Stimulated whole saliva secretion flow rates (SFR) were measured before RT and 1, 6, 12, 24 months after RT. Thirty patients showed no carious lesions (group A), 18 patients developed sporadic carious lesions (group B), and 22 patients developed general carious lesions (group C). Group A patients received a D (mean) of 21.2 +/- 11.04 Gy. Group B patients received a D (mean) of 26.5 +/- 11.59 Gy and group C patients received a D (mean) of 33.9 +/- 9.93 Gy, respectively. The D (mean) of group A was significantly lower than the D (mean) of group C (p < 0.001). Additionally, the mean SFR 6 months after RT of group A was significantly higher than the mean SFR of group C (p < 0.01). Irradiation damage on dental hard tissue correlates with increased mean irradiation doses as well as decreased salivary flow rates. Parotid gland sparing resulting in a dose below 20 Gy reduces radiation damage on dental hard tissues, and therefore, the dose may act as a predictor for the damage to be expected.