The use of implant retained mandibular prostheses in the oral rehabilitation of head and neck cancer patients. A review and rationale for treatment planning

Abstract

Surgical treatment of malignancies in the oral cavity (tongue, floor of the mouth, alveolus, buccal sulcus, oropharynx) often results in an unfavourable anatomic situation for prosthodontic rehabilitation. The outcome is a severe disturbance of oral functioning despite the improved surgical techniques for reconstruction that are currently available. Radiotherapy, which often is applied postsurgically, worsens oral functioning in many cases. Main problems that may hamper proper prosthodontic rehabilitation of these patients include a severe reduction of the neutral zone, an impaired function of the tongue, and a very poor load-bearing capacity of the remaining soft tissues and mandibular bone. Many of these problems can, at least in part, be diminished by the use of endosseous oral implants. These implants can contribute to the stabilisation of the prostheses and intercept the main part of the occlusal loading. Surgical interventions after radiotherapy are preferably avoided because of compromised healing, which may lead to development of radionecrosis of soft tissues and bone as well as to increased implant loss. If surgical treatment after radiotherapy is indicated, measures to prevent implant loss and development of radionecrosis have to be considered e.g. antibiotic prophylaxis and/or pre-treatment with hyperbaric oxygen (HBO). To avoid this problem, implant insertion during ablative surgery has to be taken into consideration if postoperative radiotherapy is scheduled or possibly will be applied. This approach is in need of a thorough pre-surgical examination and multidisciplinary consultation for a well-established treatment planning. The primary curative intent of the oncological treatment and the prognosis for later prosthodontic rehabilitation have to be taken into account too.

Introduction

Surgical treatment of malignancies involving the oral cavity often results in an altered anatomical situation, which may severely hamper oral functioning. Surgical treatment is often combined with radiotherapy, which further worsens oral functioning. Amongst others salivary secretion is reduced, and speech, chewing (mastication), swallowing and aesthetics are in general impaired.[1], [2], [3], [4], [5], [6], [7], [8], [9] Due to the changed intra-oral conditions the possibilities to obtain proper stability and retention of a mandibular prosthesis are seriously at risk.[1], [9], [10], [11], [12] For example, particularly after radiotherapy, the load-bearing capacity of both the native and reconstructed tissues is compromised. [7], [10], [13], [14]

Until recently neither reconstructive surgery nor conventional prosthodontic techniques were capable to address these problems successfully.[15], [16] A proper choice of reconstruction techniques in combination with implant supported or retained prosthodontics probably can attribute to better functional results in the oral rehabilitation of these patients.[6], [8], [10], [12], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26] As a first effect, implants are used with increasing frequency for prosthetic support in patients who are treated for malignancies in the lower region of the oral cavity.[9], [11], [13], [20], [26], [27] This includes reconstruction of the mandible and insertion of implants in patients who have been treated with radiotherapy, in spite of the well-documented adverse biologic changes that occur when soft and osseous tissues have been exposed to ionising radiation.[3], [4], [7], [20], [28], [29], [30], [31]

Irradiated sites are thought to be at significant risk for tissue necrosis and loss of implants, if subjected to implant surgery.³² Thus, the appropriateness of using implants in irradiated patients has been seriously questioned.¹⁸ Because of the radiation hazards mentioned, it might be reasonable to place implants prior to postoperative radiotherapy, preferably simultaneously with ablative surgery.[2], [15], [27], [33]

In this paper the literature regarding the treatment outcome of the use of implants for oral rehabilitation in edentulous patients within the scope of the oncological treatment in the lower region of the oral cavity is reviewed and a rationale for treatment planning is given.