Partial mandibulectomy may be necessary in severe cases of ORN. The mandible can be reconstructed to provide continuity for esthetics and function. A multidisciplinary cancer team that includes oncologists, oncology nurses, maxillofacial prosthodontists, general dentists, hygienists, and physical therapists is appropriate for management of these patients.
Necrosis and secondary infection of previously irradiated tissue is a serious complication for patients who have undergone radiation therapy for head and neck tumors. Acute effects typically involve oral mucosa. Chronic changes involving bone and mucosa are a result of the process of vascular inflammation and scarring that in turn result in hypovascular, hypocellular, and hypoxic changes. Infection secondary to tissue injury and osteonecrosis confounds the process.
Soft tissue necrosis can involve any mucosal surface in the mouth, though nonkeratinized surfaces appear to be at moderately higher risk. Trauma and injury are often associated with nonhealing soft tissue necrotic lesions, though spontaneous lesions are also reported. Soft tissue necrosis begins as an ulcerative break in the mucosal surface and can spread in diameter and depth. Pain will generally become more prominent as soft tissue necrosis becomes worse. Secondary infection is a risk.
Musculoskeletal syndromes may develop secondary to radiation therapy and surgery. Lesions include soft tissue fibrosis, surgically induced mandibular discontinuity, and parafunctional habits associated with emotional stress caused by cancer and its treatment. Patients can be instructed in physical therapy interventions such as mandibular stretching exercises and the use of prosthetic aids designed to reduce the severity of fibrosis. It is important that these approaches be instituted before trismus develops. If clinically significant changes develop, several approaches can be considered, including the following:
- Stabilization of occlusion.
- Use of trigger-point injection and other pain management strategies.
- Use of muscle relaxants.
- Use of tricyclic medications.
Trismus has been associated with significant morbidity post–radiation therapy, with significant health implications, including reduced nutrition due to impaired mastication, difficulty in speaking, and compromised oral hygiene. Limitations in jaw opening have been reported in 6% to 86% of patients who received radiation to the temporomandibular joint and/or masseter/pterygoid muscles, with frequency and severity that are somewhat unpredictable.
The loss of function and range of mandibular motion from radiation therapy appears to be related to fibrosis in and damage to the muscles of mastication. Studies have demonstrated that an abnormal proliferation of fibroblasts is an important initial event in these reactions. Additionally, there may be scar tissue from radiation therapy or surgery, nerve damage, or a combination of these factors. Regardless of the immediate cause, mandibular hypomobility will ultimately result in degeneration of both muscle and temporomandibular joint.
Radiation therapy involving the temporomandibular joint, the pterygoid muscles, or the masseter muscle is most likely to result in trismus. Tumors related to this type of radiation can appear in the following locations:
- Oral cavity.
- Base of tongue.
- Salivary gland.
- Maxilla or mandible.