In a retrospective study, two mandibular prosthetic rehabilitation strategies supported by implants in oral cancer patients were evaluated: implants placed in the non-resected edentulous symphyseal area during ablative surgery (DAS implants); or at a later stage (postponed (P) implants). Medical files of patients from two head-neck oncology groups from 2000 to 2005 were screened for study inclusion. DAS protocol was used in one group and P protocol in the other. After a 5 year follow-up of 261 edentulous patients with oral cancer in the second group, P implants were placed in 27 patients to support an overdenture. Of the 249 edentulous patients in the first group, 82 patients were given an implant supported overdenture using the DAS implant protocol. Regarding implant loss, no statistically significant differences were seen between the DAS and P implants. In the DAS group, more patients benefited from an implant-supported lower overdenture (39 versus 11%, respectively), and they received their overdenture on average 20.0 months sooner (sd = 11.01, p < 0.001) after ablative surgery. 17.1% of DAS implants and 4.6% of P implants were never loaded due to tumour and patient related factors including unfavourable implant soft tissue, tumour recurrence near the implant, or radiotherapy induced trismus.
Oral cancer is an increasing global problem. The annual estimated incidence is around 275,000 with a wide geographical variation. Two-thirds of these cases occur in developing countries (South and Southeast Asia). In the Netherlands the incidence of squamous cell carcinoma of the oral cavity is 4.1 per 100,000 in the male population and 2.7 per 100,000 in the female population. These numbers have increased over the past few decades and this trend is continuing. This trend is also seen in the UK. The increasing incidence is mostly attributed to excessive use of alcohol and smoking, but also to the proportional rise in the ageing population.
Surgery, on indication followed by radiotherapy, is the curative treatment of choice. Ablative surgery for oral cancer results in altered anatomical relations and physiology. Besides being permanently disfigured, patients suffer from diminished or lost essential oral functions, such as speech, chewing and swallowing. Because oral tumours are mainly located on the tongue and the floor of the mouth postoperative radiation with or without chemotherapy results in significant additional side effects such as diminished tongue mobility, tongue sensation and xerostomia. This has a considerable impact on the patients’ emotional and social well being and consequently a significant adverse effect on the quality of life (QOL).
Improvement of oral functions may be achieved by implant-supported prosthetic rehabilitation. The timing of oral rehabilitation is still subject to debate. To date, implant survival in oncological patients is thought to be less than in non-oncological patients. Up to 35% of the implants placed in irradiated bone were reported to be lost. Thereby, the survival of implants in grafted bone was lower compared to those in non-grafted bone.
In general, two methods are being proposed for implant placement in the edentulous symphyseal region: direct placement during ablative surgery (DAS implants) or postponed (P implants) placement ( Fig. 1 ). Postponed means more than 6–12 months after initial oncological treatment. DAS implants have the advantage that the implantation site has not been compromised as a result of radiotherapy, thereby bypassing, for example, the need for preventive antibiotics and hyperbaric oxygen therapy prior to implantation to reduce the risk of osteoradionecrosis. The main disadvantage of primary implantation is that proper positioning of the implants is more difficult, especially if the tumour is located near the interforaminal region. In those cases, the soft tissue contour is often unpredictable, sometimes resulting in an improper implant position and frustrating oral rehabilitation as a consequence. In addition, DAS implants may have to be removed in case of tumour recurrence, the incidence of which is highest during the first postoperative year.
In two large Dutch head and neck oncology centres, different protocols for implant placement were used. In the Radboud University Nijmegen Medical Centre (RUNMC) implants were placed, if possible and feasible, in the original non-reconstructed mandible during ablative surgery (DAS protocol). In the University Medical Centre Utrecht (UMCU) all edentulous patients were seen after oncological treatment during a multidisciplinary consultation to evaluate the opportunities for prosthetic rehabilitation with or without the use of dental implants. As such, implants were placed during the post-therapy phase provided that no recurrence had occurred in the meantime and depending on tumour-treatment related sequelae (postponed (P) protocol).
The authors’ hypothesis is that, for implants placed in the edentulous symphyseal area in patients with a primary squamous cell carcinoma (SCC) in the oral cavity, the DAS protocol will result in faster prosthetic rehabilitation than postponed installed implants, without increase in the complication rate.
Materials and methods
The files of all patients treated for oral cancer between 2000 and 2005 in RUNMC and UMCU were screened thoroughly. Nine hundred and ten consecutive patients diagnosed with a primary SCC in the oral cavity were screened. Patients were only included if they were edentulous prior to ablative surgery or became edentulous during ablative surgery with a curative intend. Five hundred and ten patients (56%) were edentulous at the time of diagnosis or became edentulous because of therapy. In the RUNMC, 249 patients (139 (55.82%) men, 110 (44.12%) women) were involved, in the UMCU, 261 patients (155 (59.39%) men, 106 (40.61%) women).
In the RUNMC, in all patients, 2–4 Brånemark ® Mk II/III two-phase implants were placed during tumour resection, in the UMCU all patients received 2–4 Frialit ® two-phase implants. The implants were exclusively placed in the inter-foraminal area. Patients who had mandibular reconstructions using micro revascularized bone grafts or homologous bone transplants were excluded. All patients had a regional (levels I–III) or modified radical (levels I–V) neck dissection. The ablative oral defects were closed primarily, covered with a split-thickness skin graft or revascularized soft-tissue free flap.
Based on the histological findings, postoperative radiotherapy was offered in accordance with Dutch guidelines in a dose of 60–68 Gy within 6 weeks of ablation of the tumour on the primary tumour site.
In the UMCU, prior to implant placement in the P protocol, all patients received additional hyperbaric oxygen therapy, on condition that 1 year after therapy no recurrence of oral SCC was diagnosed. The period of implant insertion until abutment placement was kept to a minimum of 3 months in non-radiated patients, whereas in irradiated patients a minimum interval of 6 months was taken into account. Data collected during the 5 year follow up included dates of the ablative surgery, the implant placement procedure, the time of becoming functional (i.e. the time of abutment placement) and implant survival. Only if osseointegration failed was an implant considered lost. An inventory was made of the tumour location, TNM classification, pathological characteristics of the resection specimen, number and length of implants placed, radiation dose, complications, the need for surgical corrections and if hyperbaric oxygen therapy was administered.
Data are given with a percentage and/or standard deviation. Statistical analysis was performed using SPSS 12.0 (SPSS Inc., Chicago, USA). Differences were considered significant at p < 0.05.
Of 910 patients with oral SCC treated between 2000 and 2005, 510 (56%) were edentulous at the time of diagnosis or became edentulous because of therapy. Fifty percentage of all 510 patients received postoperative radiation 31 days (sd = 6.29) after surgery. In the RUNMC, 249 patients were involved, in the UMCU, 261 patients. Analyses of both groups revealed no statistical differences for tumour classification, tumour characteristics, pathology features of the resection specimens and therapy. ( Table 1 ) The hazard ratios that were calculated were small, indicating small relative difference between the variables, also for the differences in implant systems used.
In the UMCU, 29 of 261 patients finally received implants (P protocol). During the same period at the RUNMC, 99 of 249 patients were implanted according the DAS protocol ( Table 2 ). Ultimately, 82 of these 99 patients (82.8%) were rehabilitated with an implant-supported overdenture on 2–4 implants. Of the total of 249 implants placed, 24 implants were lost (9.6%) ( Table 3 ).
|Population size||Percentage||RT+/total patient group||Implants||RT−/total patient group||Implants|
|Total patient group/implants placed||Implant supported overdenture/number of implants used||Percentage implant supported overdentures||Implant loss|
|DAS-implant group||99/249||82/205||82.8%||24 (=9.6%)|
|P-implant group||29/65||59/27||93.1%||6 (=9.2%)|