Newsletters for MDs

Dental Implants and Cancer Patients

Cancer therapy in and around the mouth does not end with surgery, radiation and chemotherapy. The success of prosthodontic devices, such as obturators and speech appliances, is dependent on how rigidly these devices can be anchored. When there aren’t adequate teeth to support the device, dental implants can be placed and serve as the necessary anchor.

The history of dental implants goes back at least to ancient Egypt where mummies have been found with brass implants supporting artificial teeth. In the last forty years there have been a large variety of methods and materials used in attempts to develop an effective dental implant, most of which were long term failures. Starting in the early eighty’s with the introduction of osseointegration and the development of titanium cylindrical implants we have gained the ability to achieve high levels of success. The twenty-five year success rate for these implants in healthy patients, according to the worst statistics, is approximately 85% in the upper jaw and 92% in the lower jaw. In fact, the success rate appears to be much higher.

Dental implants can best be compared to using a molly in a plaster wall to support a picture. First you drill a small hole and place the molly in the wall. Once secure, you place the support screw in the molly extending it into the room, so you can hang the picture. With a dental implant, the cylindrical implant is placed in the bone and not stressed for a healing period of approximately four months in the mandible and six months in the maxilla. The top of the implant is then exposed and the attachments necessary to support the teeth or device are added to the implant. The prosthesis can then be retained by a firm foundation, based on the implant’s attachment to bone. The number and location of the implants, the density of the bone, and the nature of the defect determine the type of prosthesis and the rigidity of the attachment of the prosthesis to the implants. Results range from devices that can only be removed by the dentist, to devices that are routinely removed by the patient, from rigidly retained devices, to those with a range of motion. Dental implants can also be placed in the facial areas to support artificial ears, noses and orbital prostheses.

When the treatment protocol requires radiation therapy, there are several potential side effects in the mouth. In relation to implants, the most important of these is the decrease in the size and number of blood vessels in the area of radiation. This reduction in the blood supply to the irradiated bone, raises the possibility of osteoradionecrosis following surgical placement and/or implant failure, and has always been an impediment to the placement of dental implants in areas of previous radiation therapy. Studies of dental implants placed in patients with previously irradiated bone have been accomplished in several medical centers. In five and seven year studies the success rate has been demonstrated as twenty to thirty percent lower than implants placed in the same areas that have not been irradiated. Since the normal success rate is in excess of 90% this still gives approximately a 65% success rate for individual implants placed in radiated bone. More important than the success rate was the finding that failed implants rarely cause osteoradionecrosis, but rather result in bone loss in areas related to the implant. It should be noted, however, that the number of cases reported is small and can not therefore be assumed to represent universal results. Several dives in a hyperbaric oxygen chamber have been used to decrease the effects of radiation on bony vascularity prior to implant placement. Radiation therapy occurring after implants have been in place for several months, seems to have little effect on the success rate of the implants. My experience with implant failures matches the literature, but I have also found an increase in minor complications around the implants. When possible, however, dental implants supporting a prosthesis can be the key to a patient being able to live a normal life.

The placement of an implant demands adequate height and width of bone to provide the implant with proper support. When it isn’t adequate, bone augmentation is possible. Traditional dental procedures can reliably increase the width of the remaining bone, but adding height has not been as reliable to date, except in the area of the sinuses. Augmenting the inferior portion of the maxillary sinus effectively increases the height of the remaining dental ridge allowing implant placement in atrophic areas. When a graft is placed after radiation therapy, the grafted area is non-radiated bone. These grafts are capable of supporting dental implants without fear of osteoradionecrosis. Vascularized grafts, if placed after radiation can be used to support dental implants as soon as viability is assured.

The bottom line on the use of dental implants for the support of maxillofacial devices is that they are an excellent adjunct, allowing a more rigid retention of the prosthetic devices, thereby improving the patients quality of life. When possible the dental implants should be placed prior to radiation therapy. Placement of dental implants in previously irradiated bone should only be done when the higher rate of failure is justified by the need for retention of the prosthesis. When dealing with heavily irradiated bone, hyperbaric oxygen treatment should be considered.

As always, early involvement of the prosthodontist allows me to determine the need for implantation and the best location of the implants. If the decisions are made early in the treatment planning, the best timing and best results can be attained. Teamwork is everything.

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