Radiation caries

Radiation caries is a side effect that can occur in patients after radiation in the head and neck area. Aetiologically, there appears to be a synergistic combination of damage: on the one hand, the ionizing radiation on the teeth leads to direct damage to the odontoblasts with retraction of the odontoblast processes, so that less dentin can be newly formed and the antimicrobial defence of the teeth against cariogenic bacteria is also reduced. On the other hand, the teeth become more susceptible to caries due to possible radioxerostomia, i.e. the lack of saliva flow.

Radicular caries usually results in a chalky to opaque change in the enamel. It loses its shine and transparency. At the same time or after a delay, real substance defects appear on the neck of the tooth or on the incisal edges. Starting from this disease process, the destruction typical of radiation caries develops, undermining the enamel and often leading to the loss of large areas of the enamel mantle. This is therefore chronic radiation damage to the tooth structure ("radiation caries").

In order to reduce the risk of radiation caries, the dentition should be completely restored before the start of radiotherapy. Already in this phase, oral hygiene and the patient's willingness to cooperate should be improved through comprehensive oral hygiene instructions. However, oral hygiene measures alone cannot prevent the development of radiation caries. Saliva substitutes are another option, but they have no caries-preventive effect and can even damage the tooth structure. Some saliva substitutes have a low pH value and can have an erosive effect. Regular local fluoridation during and after irradiation is a key adjunctive therapy for patients with head and neck irradiation. Stimulating the flow of saliva with sugar-free sweets or chewing gum and drinking plenty of fluids is helpful symptomatically. Frequent mouth rinsing removes the thick saliva and facilitates oral hygiene. Pronounced dry mouth can be alleviated with artificial saliva, but this does not solve the problem of tooth decay.

The erosion of the enamel, which can turn brownish to black, progresses within a few months. The exposed dentin core shows softening, cavities and progressive destruction of the entire tooth crown. However, spontaneous or thermal pain is often absent.

Regular fluoridation of the teeth before and during radiotherapy is therefore recommended as a prophylaxis against radiation caries. A fluoridation tray (Fig. 3) can be prepared for this purpose, which is filled with a small amount of fluoride gel (e.g. Elmex Gelée®) twice a day after brushing the teeth and inserted for approx. 2 minutes.

1. Beech N et al. (2014) Dental management of patients irradiated for head and neck cancer. Aust Dent J 59:20-28.