The surgical ablation of head and neck cancer followed by radiotherapy often leads to unfavorable functional and aesthetic outcomes. Studies have demonstrated that these outcomes can significantly impact quality of life. Dental implants play a crucial role in rehabilitation by facilitating the use of suprastructures and obturators. However, the long-term survival of dental implants in patients who have undergone radiotherapy remains uncertain, raising several questions. These include determining the optimal timing for dental implantation (before or after radiotherapy), identifying the radiotherapy threshold for implant loss, and considering the role of hyperbaric oxygen therapy. These and other related concerns will be addressed in the following article.
Key points
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Dental implant installation in irradiated patients is not significantly less successful than the general population.
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Implantation should be carefully considered, taking into account additional risks associated with radiation therapy.
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The timing of dental implant installation, whether before or after radiation therapy, is a subject of ongoing debate.
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It is recommended to wait for a minimum of 6 months after the completion of radiation therapy before proceeding with dental implant installation.
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In cases whereby radiation therapy is below 40 to 50 Gy it is rare to see dental implant failure.
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Consulting with the radiation oncology team and reviewing dosimetry fields are recommended steps in planning the position of dental implants for irradiated patients.
Introduction
Survivors of head and neck cancer face ongoing challenges due to post-ablative changes that significantly impact their quality of life. These changes often result in defects in both hard and soft tissues, leading to functional impairments and aesthetic concerns. Radiation therapy (RT), whether used alone or as part of a multimodal treatment approach, can have enduring side effects that severely debilitate patients over the Long-term.
In recent decades, the quality of life of head and neck oncology patients has emerged as a crucial concern that cannot be overlooked. In our current era, there has been a shift in focus toward not only curing patients of their malignancy but also preserving and enhancing their quality of life. The absence of teeth has a profound impact on patients’ lives, and dental rehabilitation is a significant step toward oral restoration and overall recovery. Patients without teeth often experience social isolation and poor quality of life. Patients with edentulous head and neck cancer who did not receive implant-retained prostheses experienced significant psychological morbidity, reporting lower levels of self-esteem and body satisfaction. Furthermore, speech, swallowing, and chewing, which are particularly challenging in the absence of teeth, were identified as critical factors in quality-of-life assessments.
Dental implants are increasingly used in head and neck oncology patients to address missing teeth and provide support for various types of prosthetic suprastructures, including removable overdentures and obturators. , , , , Implant-retained rehabilitation offers several benefits, such as improved mastication of solid foods, enhanced speech intelligibility, support for facial soft tissues, and better aesthetics.
However, rehabilitation in this population presents significant challenges due to microstomia, scar bands, and limited mouth opening. In the setting of xerostomia and fragile mucosa following RT, dental implants can ease the use of overdenture and reduce the overloading of vulnerable soft tissues. The literature on the survival rates of dental implants in irradiated patients is sparse, and the available evidence is often contradictory. Additionally, there is considerable debate surrounding the timing of dental implant installation—whether it should be done before or after RT, and its influence on survival rates. The survival of dental implants following RT is multifactorial and depends on various factors. Tanaka categorized these factors into 3 main groups: RT-related factors (such as dosage and modality), dental implant-related factors (such as timing of installation and integration, and anatomic site), and patient-related factors (such as smoking, bruxism, and occlusion stability).
Opponents of dental implants in irradiated head and neck patients argue that this is an elective procedure and better to avoid because of the risk for serious complications such as peri-implantitis, implant loss, and osteoradionecrosis. Early publications from the end of the last century showed a disappointing low survival rate of implants. They question the appropriateness of using dental implants in irradiated patients. ,
Nevertheless, there is a broad agreement in the contemporary literature that dental implants are no longer contraindicated in these patients. That being said, it is worth noting that financial coverage serves as one of the obstacles to dental implantation, varying between countries, and potentially restricting its utilization in irradiated patients.
The purpose of this article is to review the existing literature regarding the long-term survival of dental implants among head and neck cancer irradiated population.
Survival of dental implants installed after radiation therapy (secondary implants)
The majority of studies discuss the placement of dental implants after the completion of RT. Despite requiring an additional surgical procedure, this approach is preferred for several reasons. The functional limitations become clearer postsurgery and RT, enabling better planning for implant-based rehabilitation. Additionally, the positioning and angulation of secondary implants tend to be more precise, making them preferable for successful prostheses, particularly fixed appliances. Moreover, secondary implants are favored when considering the possibility of tumor recurrence. On the other hand, some patients may be hesitant to undergo a secondary procedure for dental implant placement due to physical and mental exhaustion following extensive oncologic treatment, which will leave them partially or completely edentulous.
The literature presents varying perspectives on the long-term survival of secondary dental implants in irradiated patients, with some studies reporting significant correlations between implant failure and RT. Hessling and colleagues conducted a retrospective review of secondary implants in irradiated patients with oral cancer. They discovered a statistically significant correlation between implant loss and RT (40–66 Gy), with a 5-year implant survival rate of 97.1%. Notably, the majority of implant failures occurred in transplanted bone grafts and free osteocutaneous flaps. In another retrospective study by de la Plata, secondary implants in irradiated patients (50–70 Gy) exhibited a survival rate of 92.6% over 5 years, compared with 96.5% in nonirradiated patients. Ettl and colleagues observed prospectively the outcomes of secondary implants in irradiated patients (40–72 Gy), noting a significant association between radiation therapy and implant failure. They reported a 95% survival rate more than 1 year and they observed a higher incidence of failures in irradiated transplanted bone.
While these short-term studies may present promising dental implant survival rates in irradiated patients, they might not fully capture the long-term effects of RT on dental implants, as demonstrated by longer-term investigations. Yerit and colleagues conducted an 8-year follow-up study on secondary mandibular implants in chemo-radiated patients (50 Gy) with oral cancer, revealing a significantly lower implant survival rate of 72% compared with 95% in non-irradiated patients. Interestingly, survival rates were 93% and 90% after 2 and 3 years, respectively. These findings highlight the importance of long-term studies in assessing implant outcomes. Doll and colleagues conducted a follow-up study spanning up to 20 years on secondary implants in chemo-radiated patients (50–72 Gy) with oral cancer. They reported a cumulative implant survival rate of 90% and identified chemoradiation as a significant factor influencing implant survival, with a 1.9-fold higher risk of implant loss compared with patients treated exclusively by surgery. Similarly, Visch and colleagues analyzed the prospectively survival of secondary implants over an extended period, revealing a 10-year survival rate of 78%.
Meta-analyses and systemic review as well confirm that irradiation negatively affects dental implant survival. Scheignits and colleagues conducted a meta-analysis, focusing on studies with a mean follow-up of at least 5 years. They observed a significantly lower survival rate of dental implants in irradiated bone (89.3%), compared with nonirradiated bone (95.8%). Additionally, implants placed in irradiated grafted bone were more prone to failure compared with native bone, with survival rates of 81.4% and 91.8%, respectively. Another meta-analysis also affirmed the negative impact of irradiation on dental implant survival, with a risk ratio of 2.18 and an overall risk of 16.4% of losing dental implants following RT. Chambrone and colleagues’s systematic review similarly identified a significant increase in the risk of implant failure among irradiated patients.
It is important to note that several other publications have found the correlation between implant failure and RT to be less pronounced. Shaw and colleagues retrospectively reported a secondary implant survival rate of 85% in irradiated patients (40–66 Gy) over a 14-year period. While they observed a higher failure rate in vascularized bone grafts, they did not find a significant correlation between irradiation and implant loss. Similarly, Patel and colleagues conducted a retrospective study that found a dental implant survival rate of 97% in irradiated patients (61 Gy), suggesting that the association between RT and dental implant survival was not statistically significant and lower than that reported by other studies. Additionally, Laverty and colleagues found retrospectively that the 5-year survival rate of secondary implants was 95.5% in irradiated patients (50–70 Gy), with a trend suggesting increased implant failure following RT, although it did not reach statistical significance. Notably, failure rates were statistically higher in cases involving bone grafts or free flaps.
When considering secondary implants, it is recommended to follow a protocol that includes the cessation of smoking, using an atraumatic surgical technique with minimal periosteal reflection, and extending the integration time by 3 months. It is also advised to ensure that the bone bleeds during dental implant preparation before proceeding to implant installation.
Timing of dental implant installation following radiation therapy
It is believed that the timing of dental implant placement significantly influences its long-term success. The optimal timing for secondary implant installation remains a topic of debate in the literature. Although various opinions exist regarding the most suitable timing, there is a consensus that implants should not be installed before at least 6 months have elapsed since the completion of RT. , , , , , Some recommend waiting specifically for 6 months after RT, , while others suggest waiting for a longer duration, such as 12 months, , or even 24 months. Additional considerations for the timing of secondary implants include the fact that the first 12 months following the completion of RT are considered a high-risk period for recurrence. , Consequently, it is sensible to delay rehabilitation and dental implant installation during this period. Furthermore, waiting for 6 to 12 months before proceeding with implant placement helps to avoid early complications of surgery and RT. , This cautious approach allows for better healing and reduces the risk of adverse effects on implant success. Two antagonistic effects in the recovery of irradiated bone over time were described. In the short-term following RT, there is a positive effect of improved bone healing capacity. However, in the Long-term, there is a negative effect of increased (and cumulative) vascular damage and decreased bone healing. , Therefore, it was recommended for an optimal time window for secondary implant installation to take place between 6 and 24 months from the completion of RT ( Fig. 1 ). Visch and colleagues did not find significant differences in outcomes between dental implants installed less than 12 months and those installed more than 12 months after irradiation. Charcnovitz and colleagues had similar results. Werkmeister holds the same opinion, reporting that dental implants installed 2 years following RT were less likely to integrate. The suggested timeframe provides a balance between the positive and negative effects of irradiated tissue recovery.
Survival of dental implants installed before radiation therapy (primary implants)
A limited number of studies have explored the placement of dental implants during ablative surgery, prior to RT. This approach enables the first stage of osteointegration with a low risk of RT-related complications such as osteoradionecrosis and implant failure. , The majority of osteointegration occurs within the first 6 weeks following implant placement, a timeframe typically before the commencement of RT. Moreover, this approach expedites dental rehabilitation and increases patient satisfaction. , , It was shown that patients who received dental implants during resection surgery were able to have their implant-retained overdentures fitted after 7 months, whereas those who underwent implant placement after RT required an average of 27 months for the same outcome. While the approach of placing dental implants during ablative surgery seems reasonable, especially when RT is anticipated, there are potential drawbacks to consider. These implants are sometimes misplaced, particularly in cases involving extensive tissue ablation. , Additionally, some implants may lack keratinizing mucosa around them, necessitating additional surgical procedures. Furthermore, surgical teams may hesitate to install implants during ablative surgery, preferring to postpone the procedure until the patient’s prognosis is clearer and their functional needs are better understood. This approach also accounts for additional surgery time and added financial costs which should also be considered. In cases involving free flaps, primary implant installation may pose risks to the blood supply and increase ischemic time. For these and other reasons, usually, dental implants are not installed prior to RT in oncologic patients. , , This method is not popular, and contradictory results in the literature raise doubt that this is a better solution than secondary implants. However, there are recently new encouraging reports that primary implant installation is becoming more common. , , , ,
The primary implant long-term survival rate was found to be about 90% according to a few studies. , , Several articles compared the long-term survival rate of primary and secondary implants. While some articles found a higher survival rate in primary implants, others did not find it to be significant. , , , , , Pitorro and colleagues in a systematic review reported a better survival rate of primary implants (89.4%–97%) compared with secondary implants (80%–100%). They attribute this difference to the compromised osseointegration process caused by RT and advocate for dental implant installation during ablative surgery as the most appropriate timing. However, Colella and colleagues’s systematic review of the literature did not find significant differences between primary and secondary implants, with similar failure rates of 5.4% and 3.2%, respectively. Mizbah and colleagues did not find a significant difference in implant survival rate whether placed before or after RT. Both methods demonstrated approximately a 91% survival rate during a 5-year follow-up period. Interestingly, they observed that in the post-RT group, a higher percentage of implants were functional (93.1%) compared with implants that were installed during ablative surgery (82.8%). This discrepancy could be attributed to several factors. When implants are installed during surgery and before RT, the oncologic outcome is still uncertain, and there may be unfavorable soft tissue profiles or recurrences that prevent the use of these implants. In contrast, implants installed after RT are more likely to be used effectively. On the other hand, a year after oncologic treatment, fewer patients received implants due to decreased motivation for rehabilitation, compared with primary implants. Others came to similar conclusions, finding primarily an implant survival rate of 97% but with only a 75% prosthetic success rate due to tumor recurrence, metastases, and psychological reasons. , ,
Anecdotal reports challenge the approach of primary implants due to concerns regarding potential damage caused by radiation scattering from the implants, such as osteoradionecrosis, and the risk for tumor recurrence around implants that were placed primarily. In cases whereby dental implants are used, particularly for fixed prostheses, there is a risk that the diagnosis of a second primary or recurrence around the implant may be delayed, as it can mimic a benign peri-implant complication.
In our view, careful patient selection is imperative when considering the primary installation of dental implants ( Fig. 2 ). Our experience indicates that not all patients with head and neck cancer necessitate dental implants. Some individuals may experience fatigue and exhaustion, and may not be inclined toward additional interventions, while others may have apprehensions about undergoing another surgery. In several cases whereby we installed dental implants primarily during ablative surgery, the rehabilitation process remained incomplete. This observation has also been noted by others. , Therefore, we advocate for a meticulous assessment of each case, taking into account the unique needs and motivations of the patient. Furthermore, we stress the importance of fostering a strong collaboration with experienced prosthodontists, given the significant degree of customization required in such complex cases.
