Radiation therapy is mainly used in Oral cavity to treat malignant lesions which lead to many oral changes as the effect of radiation is seen on many oral tissues. As oral cavity consists of radiosensitive, vegetative and differentiating intermitotic cells in the mucous membrane. The most common change seen in the oral mucous membrane after two weeks of radiation therapy is marked rednes and inflammation which is called as Mucositis.
Due to the effect of Radiation Therapy on tissues of the oral cavity there are secondary infections or symptoms seen. Some of the secondary symptoms seen are Dry mouth due to the changes which take place in salivary glands along with secondary infections like Candidiasis caused due to Candida Albicans which is a result of Radiation therapy. Many complain of loss of taste sensation which is seen due to the effect of radiation on taste buds.
Let us look at all the changes which take place on tissues of the Oral cavity in detail –
Cells: Effect of radiation on cells is harmful leading to both structural and functional changes in the cell organelles which can lead to death of the cell. In most cases there is arrest in cell division. The Nucleus is more sensitive to radiation in comparison to cytoplasm. There are changes seen in the Chromosomes and DNA inside the Nucleus due to Radiation exposure which lead to chromosomal abberations.
Effect of Radiation on Teeth: The tooth is made up of mineralized part – Enamel and Dentin and tissue part – Pulp. The mineralized portion of the tooth is resistant to Radiation but the soft tissue part which is the pulp exhibits fibroplasty on Radiation exposure. Even the mineralized part (Enamel and Dentin) is succeptible to Radiation during the developmental stages and shows developmental disturbances.
Effect of Radiation although not direct but secondary effect is seen due to changes in other structures of the oral cavity. The secondary changes in the oral cavity due to Radiation which lead to Rampant caries in Teeth are as follows:
Salivary Glands are affected which lead to decrease in the production of Saliva and leads to Dry motuh.
- Reduced Flow of Saliva due to decrease in quantity of saliva
- Increased Viscosity of Saliva – More Mucous and less serous saliva is seen
- Decrease in pH as saliva becomes more acidic it leads to demineralization of the teeth
- The buffering capacity of saliva is decreased which leaves teeth more succeptible to caries
Due to these changes in the oral cavity mostly due to the lack of saliva the effect on teeth is seen which leads to increased incidence of Dental caries in postirradiation period.
Effect of Radiation on Bone: The Maxilla and Mandible are the Bones of the Oral cavity and Mandible is the most affected part of the Oral cavity due to Radiation Exposure. The first change due to radiation in the mandible is seen in the Vasculature. The most affected part of the bone is the bone marrow.
Osteoradionecrosis is the most commonly seen problem due to Radiation exposure, it is caused due to the decreased healing potential or decreased capacity of the bone to resist infection usually after Trauma to the bone most commonly after Tooth extraction. It is seen in about 11-15% of patients who have undergone radiotherapy. Most common symptoms of Osteoradionecrosis is Foul Odor, Exposed Necrotic bone, Severe Pain, Discharging fistulae and Mucosal defects are seen.
Precautions to be taken to avoid Osteoradionecrosis are – Extraction should be performed three weeks prior to Radiation therapy. Extraction of teeth after radiation therapy should be avoided till radiation mucositis is resolved.
Effect of Radiation on Salivary Glands: Most changes to the teeth are due to decrease in saliva and changes to saliva. Salsivary glands are exposed to radiation during treatment of tumors in the Head and Neck region. The Parenchymal cells in the Salivary glands are the most Radiosensitive. Parenchymal degeneration is caused due to inflammatory response to serous acini along with increase in serum amylase which leads to progressive fibrosis, adiposis, loss of fine vasculature. With the loss of parenchymal cells there is decrease in saliva production which in turn decreases the flow of saliva, decrease in pH and increase in viscosity of the saliva in the oral cavity, all of which lead to Caries in teeth.
Effect of Radiation of Taste Buds: These are severly affected due to radiation as there is extensive degeneration of normal histologic pattern of the taste buds. Taste buds are exposed to radiation during therapy to either mandible or Head and neck region. The degeneration of taste buds leads to loss of taste senssation and decrease in apetitie to the patient taking Radiation treatment.