Impact of radiation for dental implants in cancer patients

Dental Tribune International

Thu. 4 July 2024

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OSLO, Norway: Head and neck cancer is the seventh-most diagnosed cancer group globally, and among its treatment modalities is radiotherapy, used as the primary therapy, as an adjuvant or palliatively. The treatment of head and neck cancer with radiotherapy presents a range of issues for the dental health of patients due to radiation injury to the surrounding normal tissue. A key means of expediting a return to regular oral function has been through the use of dental implants, though the question of whether to place these before or after radiotherapy has been debated. Recent PhD research from the University of Oslo has systematically explored the issue, yielding some highly significant results.

Oral impacts of head and neck cancer treatment

As confirmed by recent scientific research, the implications of head and neck cancer treatment for oral health are numerous and varied. Firstly, what comes as a great shock to many patients is that they may require extraction of teeth with poor prognoses before radiotherapy in order to minimise extraction after therapy, because of the lifelong risk of osteoradionecrosis. Once patients receive radiation to the affected areas, many may experience oral mucositis, fungal infections and loss of taste. Other possible consequences of radiotherapy are reduction of saliva production, leading to caries; tissue fibrosis, causing trismus and pharyngo-oesophageal stenosis; and thin and hypersensitive mucosa, making it uncomfortable to wear removable dental prostheses. An important corollary of these painful and debilitating physiological effects is that patients understandably experience a reduced quality of life, significant emotional difficulties and social impacts.

Implants as a way to restore oral function

The role of osseointegrated implants in restoring oral function among head and neck cancer patients is well established. However, as Dr Lisa Printzell describes in her recently completed PhD thesis, the use of implants in patients who have undergone or are to undergo radiotherapy presents a range of challenges, mainly related to the reduced ability of irradiated soft tissue and bone to heal. In news on the university’s website, Dr Printzell stated: “The survival of dental implants placed in irradiated jawbone is significantly lower than those placed in non-irradiated patients.”

To circumvent this issue, an increasingly used strategy has been to place implants before radiation has been applied to the head and neck region, giving osseointegration a head start and improving patients’ quality of life sooner through final prosthetic restorations. However, Dr Printzell’s research shows that this approach is not without its shortcomings, particularly the concern of back scatter of radiation by titanium implants, reflecting it on to surrounding tissue and subsequently intensifying the damaging effects of radiotherapy. “When ionising radiation is directed at a cancerous tumour and there is a titanium implant in the radiation field, not all the radiation will penetrate the metal. Instead, it will reflect back to the surrounding tissue,” she explained.

Understanding back scatter better

In order to determine whether back scatter from titanium is of greater threat to osseointegration than the impaired healing capacity of previously irradiated bone, a key part of Dr Printzell’s research has been to systematically explore the effect of back scatter upon two of the most important cell types for bone healing and osseointegration of implants, namely, mesenchymal stem cells and osteoblasts. Using a variety of radiation doses, ranging from 2 Gy to 10 Gy, Dr Printzell measured the extent of the effect of back scatter upon these cell types.

Her results were highly revealing: “We also found that the highest dose of 10 Gy inhibited both cell types’ ability to move from one place to another on titanium, while lower doses (2 and 6 Gy) neither caused significant DNA damage nor affected the cells’ ability to move. The results indicate that back scatter radiation from titanium at doses of 2 Gy does not cause greater cell damage than the same dose does without an implant present.” Such findings thus cast light upon the crucial issue of whether or not it is effective and safe to place implants in head and neck cancer patients before they undergo radiotherapy.

Editorial note:

Dr Lisa Printzell’s thesis, titled The Impact of Radiation Backscatter on Cells Involved in the Osseointegration of Titanium Dental Implants, is available here.