F. J. Lieshout & C. P. Bots
- Decay of teeth, erosion and disintegration of hard dental tissue are a clinically often seen side effect after radiotherapy for tumours in the head and neck region.
- Most radiation oncologists treat their patients with “conventional fractionation.” The destructive properties of this type of irradiation in the head and neck region have many additional consequences to the oral tissues and oral function. Most consequences are temporary, 1, 30, 32, 37 and other consequences have a more permanent character 30, 32, 37.
- The parotic and submandible salivary glands could be affected too which means a reduction in quantity (hyposalivation) as well as a reduced quality of the saliva 26, 30, 33.
- Clinically an often observed side effect is a rapid deterioration of the dental hard tissue. Dental hard tissue consists of enamel and dentin and is separated by the dentinoenamel junction (DEJ) 1, 17, 25, 30, 32, 37.
- Radiotherapy will affect the oral function for the rest of the patients’ life and has a big influence on the quality of life 27; however, it is still unclear which factors cause the destruction of teeth.
Purpose of the Review
- Present an overview on what is known in the literature about the changes on different levels in the dental hard tissues like enamel, dentine and the DEJ after radiation.
- Describe the share of these changes in the destruction of teeth.
- This information could be used to make a more adequate preventive and restorative treatment plan for patients before and after radiotherapy in the head and neck region.
- Fairly recent larger treatment centres in the world changed from the conventional 2 or 3 lateral-field technique to the intensity-modulated radiotherapy (IMRT). With this 360° rotation radiation therapy, the primary target still receives the total amount of radiation necessary for the treatment, while the dose to the adjacent critical structures and organs at risk is constrained 31, 34.
- IMRT in combination with the surgical transfer of the submandibular gland to a more anterior position would even more prevent hyposalivation or reduced flow rate in a lot of studied cases 36.
- Even with this IMRT irradiation method, some of the teeth are still in the targeted area and alterations of hard dental tissue and mechanical properties cannot be prevented. In the literature, no consensus can be found to what extent all these separate alterations and damages of the dental hard tissues contribute to the rapid decay of teeth.
- Although no differences could be detected between decay in non-irradiated and irradiated teeth 9, 12–14, 16 all the hard dental structures, enamel, dentin and the DEJ, are changed or damaged. Irradiation causes a total loss of prismatic structure. So, significant micromorphometric differences can be seen in the demineralisation behaviour of irradiated enamel 7.
- The results of this systematic review show a great amount of changes and damages at all levels of the hard dental tissues, enamel, DEJ and dentin. These findings substantiate the idea that the formation of recurrent and atypical patterns of dental caries in irradiated teeth is not only due to, loss of saliva but a combination of both hyposalivation and the direct effects on hard dental tissue. The formation of atypical caries is furthermore increased due to poor oral hygiene, the increase of soft and carbohydrate-rich substance and changes of the bacterial micro flora and proteins.