Outcome of Dental Extraction and Implants in Irradiated Head and Neck Cancer Patients

Abstract

In the past, implant rehabilitations were thought to be contraindicated in irradiated patients. However, advances in surgical and radiation techniques over the past decades have led to an increase in the use of dental rehabilitation in irradiated patients. In this study, we investigated the implant outcome in patients who previously received RT for head and neck malignancies and provide guidelines for tooth extraction and implantation after RT.We retrospectively reviewed 27 patients who received RT for head and neck cancer between January 2008 and December 2018 and who received dental implants afterwards. Total 90 implants were analyzed. The cumulative implant survival rate was calculated using the time frame between the date of prostheses placement and the date of implant failure or last follow-up. The factors contributing to cumulative implant survival rate were analyzed by univariate and multivariate Cox proportional hazards regression analysis with robust variance. In addition, the implant success was assessed with the Health Scale for Dental Implants. This scale incorporated clinical and radiographic evaluations to categorize implants into one of the following groups: success, satisfactory survival, compromised survival or failure. Logistic regression analysis was used to identify risk factors of compromised survival or failure.The median interval between RT completion and the prostheses placement date was 28.2 months. The median value for mean radiation dose at the implant site was 35.7 Gy. The median follow-up after implantation was 15.4 months. During follow up, 16 implants failed to survive. The estimated implant survival at 5 years was 75.4%. Mean radiation dose at the implant site were identified as independent prognostic factor for implant survival. No implant failed if prior radiation dose was less than mean 37.9 Gy. When the mean RT dose was less than 50 Gy, a total of 5 implants failed and all of the 5 implants were implants that were placed more than 2 years after RT. Regarding implant success, 49 implants were in the success group, 3 were in the satisfactory survival group, 20 were in the compromised survival group, and 18 were failures. In multivariate analysis, implants placed in the bone graft and mean radiation dose at the implant site were independent risk factors of compromised implant survival or implant failure.Our findings demonstrate that dental implantation after RT is feasible in head and neck cancer patients. Mean radiation dose at the implant site was significantly associated with implant failure. Dental implants can be safely considered in cases of mean radiation dose lower than 37.9 Gy. When the mean radiation dose was less than 50 Gy, the implant failure rate was 7.4%, which was similar to the normal implant failure rate of 5-10%. In the case of more than 50 Gy, delicate monitoring was required because the implant failure rate was high even if the implant was placed more than 2 years after RT.