Abstract
Rehabilitation with implant-retained prostheses is a key step in the rehabilitation of patients after ablative head and neck surgery. Data of patients who underwent mandibular restoration with Astra Tech implants were gathered consecutively and analyzed retrospectively. Implant survival was calculated by Kaplan–Meier analysis, and Cox models were used to identify any association between implant failure and contributing factors. In total, 136 implants were placed in 33 patients. The main reason for ablative surgery was squamous cell carcinoma. Twenty-one patients received adjuvant radiotherapy with a cumulative radiation dose of 56–76 Gy prior to implantation. Failure occurred in six patients, resulting in the loss of 17 implants. The cumulative implant survival rate was 92.7% after 1 year and 87.5% after 20 months. Smoking and alcohol consumption were associated with a significantly higher implant failure rate. Most patients had a stable implant status after 20 months.
Bone and soft tissue reconstruction techniques were developed in the early 20th century. These techniques were later revolutionized following the introduction of microvascular surgery and the subsequent development of vascularized bone grafts. Successful occlusal rehabilitation with an implant-retained prosthesis is a key step in restoring function in the midst of challenges such as poor tissue quality and scarring after radiation and surgery. Despite careful planning, implant survival in such metabolically challenged conditions is deemed to be less successful than in normal tissues. The Astra Tech implant system has favourable attributes, including a semi-rough, fluoride-enhanced surface, a nonaggressive drilling protocol, and a wide array of prosthetic options. These interdependent features together improve aesthetics and enhance the natural healing process. Microthreads allow optimal load distribution and reduce stress around the neck of the implant, leading to marginal bone preservation. The conical connection below the marginal bone level transfers loads deeper into the bone, reducing peak stresses; marginal bone preservation can thereby be achieved.
Long-term implant survival plays a critical role in the quality of life of these patients. The aim of this study was to assess the implant survival rate of this implant type in a serial cohort of patients with head and neck tumours and to identify variables contributing to implant loss.
Materials and methods
Patients who underwent mandibular restoration with Astra Tech implants after ablative head and neck surgery were evaluated retrospectively by analyzing accrued data independent from their underlying disease. The same surgical and prosthodontic team treated all patients between December 2006 and April 2012. The data were gathered consecutively by reviewing files from the study institution and a private practice office.
Due to limitations in our health insurance system, all implants were placed during a second procedure, at 6 months after the ablative surgery or 12 months after completion of radiotherapy. Implant sites were selected according to the radiation dose planning diagram, clinical evaluation (by minimal exposure of the proposed implant site), and assessment of bone vitality by pilot drilling. The isodose was not available for two patients who underwent three-dimensional conformal radiation therapy (3D-CRT). Therefore, the radiation dose per implant was not included in the survival analysis, which is a limitation of this study. This has also been a limitation in previous studies. All implants were placed in the area of primary radiation or directly adjacent to this area. Implants were placed in a two-stage protocol. Vestibular plasty and epithelialized tissue grafting were performed in all patients in whom implants were placed in free vascularized tissue.
Patients of any age and sex who underwent ablative head and neck surgery and received implants in the native or reconstructed mandible between December 2006 and April 2012 were included in this study. All patients were included independent of additional treatment with adjuvant therapy ( Table 1 ). The protocol for implant surgery and prosthodontic treatment, including dental laboratory steps with the protocol for maintenance after incorporation of the superstructure, was presented to and approved by the regional ethics commission.
