Cancer is one of the important emerging public health concerns in India. Statistics from the Hospital Based cancer registries (HBCR) report close to 1.39 million cancer cases in 2020. Cancers involving the head and neck region account for about one-third (31.2% )of these cases in males. Mouth cancer contributes to the highest number of cases related to the use of tobacco followed by lung and tongue as other primary sites.
High morbidity is associated with cancers of the head and neck; as several vital structures are involved in physiological functions such as mastication, deglutition, speech and facial expression. Pathological involvement of these anatomical structures is imperative as these functions result in compromised physical, psychological and emotional well-being.
There are several advantages of using prosthetic rehabilitation over surgical reconstruction. These include shorter surgery duration, quicker post-surgery recovery and the amenability of the site for future cancer surveillance. This article highlights the role of a dentist in the rehabilitation of these patients which can go a long way in improving their quality of life.
Prostheses commonly used in Oral Oncology
These can be primarily classified as
- Prosthesis during Radiation Therapy
- Maxillary Obturators
- Prosthesis following resection of mandible-mandibular guidance flange prosthesis
Prosthesis during Radiation Therapy
The primary role of these prostheses is to allow for effective delivery of radiation doses to the desired sites, displace or to shield the adjacent healthy structures from post-radiation effects.
Radiation stents are of the following types
• Radiation carriers – 1 Pre-loaded
• Positioning stents -1 Position maintenance device
2 Peri oral cone positioning device
• Protecting stents-1 Shielding stents
2 Tongue Depressing stent
3 Tissue recontouring stent
These help to administer the radiation to a particular area without exposing the adjascent normal healthy structures. They carry the radiation source close to the site of the lesion or directly into the tumor. In the case of pre-loaded carriers, the radioactive material is incorporated within polyethylene tubes which is in turn is incorporated within the stent and a corrobend shield (Low fusing alloy made of Bi,Pb,Sn,Cd) is added. The disadvantage is unnecessary exposure to both therapist and patient during placement. For loaded carriers, the radioactive elements are placed after the carrier is in position. The radiation source is implanted directly into the tumor using either stainless steel or nylon tubes depending upon the use of a permanent or removable implantation technique. This is useful in soft tissue tumors like Ca Cheek and buccal mucosa.
Position maintaining stents
These help to maintain movable structures like the like tongue and soft palate in position during radiotherapy. It is useful in patients undergoing multiple treatment sessions where the structures need to be positioned in a fixed and reproducible manner.
Perioral cone positioning device
This is used to prevent the movement of the cone during radiation. It is helpful in the treatment of superficial lesions on the anterior floor of the mouth, and soft and hard palate.
These are used to protect and shield the adjacent normal healthy anatomical structures from the effects of radiation. Stents can be fabricated to shield the tongue, salivary glands, etc. Shielding materials are usually low fusing alloys like Cerrobend, which is melted and poured into a hollow cavity that is related to the structure to be protected. This is then encased in an auto polymerizing resin.
Tongue Depressing Stents
These help to depress and protect the tongue from unnecessary exposure. These stents rest between the upper and lower teeth with aplate extending lingually which serves to depress the tongue. There is an opening in the anterior segment into which the tip of the tongue is placed.
Tissue Recontouring Stents
These are useful for treating lesions on the lips. These help to flatten the lips to ensure a uniform dosage of radiation to the entire lip.
Obturators are useful in patients undergoing maxillectomy for cancers involving the Maxillary sinus, Maxillary alveolar ridge, or the palate. The rehabilitation of these patients varies widely and depends upon the remaining dentition if any, presence of Oro antral/ nasal communication, involvement of the soft palate, the extent of Supero-Inferior, Antero- Posterior and Medio- Lateral involvement.
This prosthesis helps in replacing the missing structures in the maxilla, occludes Oro Antral communication, prevents Oro Nasal regurgitation, and also aids in speech and deglutition.
There are three distinct phases in obturator prosthesis namely Surgical Obturator- inserted during surgery to hold the surgical packing post-operation; Interim Obturator- given 1 week post-surgery, which is removable and adjustable during the post-operative healing period; and the Definitive Obturator given 3-4 months post-surgery when the maxillary defect becomes stable.
The success of the obturator is determined by the extent of the defect, remaining teeth arrangement and opposing occlusion which affects retention, and stability of the prosthesis, overlying quality of the mucosa which if thin, friable and easily irritated can result in poor patient acceptance and difficulty in wearing of the prosthesis, and patients prior experience with such prosthesis.
Mandibular Guidance Prosthesis
Tumors involving the mandible, both benign and malignant often require excision of the lesion along with extensive resection of the mandible. In the case of marginal mandibulectomy, where the continuity of the mandible remains intact, is not as debilitating as a segmental resection. Segmental resection is associated with compromised function, as there is a deviation of the mandible because of muscular imbalance, alteration in the maxilla mandibular relationship and reduced tooth to tooth contacts. Using definitive prostheses in these patients requires adequate post-reconstruction healing and acceptance of the osseous graft. The use of the definitive prosthesis depends upon the extent of mandibular resection, and also the effects of radiation and chemotherapy. During the interim period, a guide flange prosthesis is helpful to limit deviation and provide an acceptable masticatory function.
The guide flange prosthesis helps the patients to achieve tooth to tooth contact as the mandible is guided into position during mouth closure. This helps to eliminate deviation and uncoordinated movements of the lower jaw and therefore helps in improved masticatory performance.
The final prosthesis post-reconstruction may be implant supported to provide a fixed replacement of teeth, which is better accepted by the patient.
In conclusion, the rehabilitation of patients undergoing Onco- surgery has improved immensely following innovations in material science and the accessibility of digital scanning that helps in designing a customized prosthetic workflow.
Dr. Preeti L. Anand
Senior Dental Surgeon, Oral Pathologist & Implantologist
Kauvery Hospital Chennai