CHAPTER 8

Comparison of Treatment Strategies for Implant Overdentures

Daniel Wismeijer and Geert T. Stoker

Implants can be used to restore the edentulous mandible in different ways. For many patients, a fixed prosthesis can be placed on four or more dental implants, and long-term results for implant-retained fixed prostheses have been documented in the literature by various authors.^1-4 Implant-supported removable overdentures using two or more implants are also a possible treatment option for patients who have problems with conventional dentures.^5-14

Overdentures obtain support and retention from a superstructure attached to the implants. This superstructure defines the character of the denture that can be created. One can differentiate between tissue-supported, tissue-implant-supported, and mainly implant-supported overdentures. In the tissue-supported overdenture on two implants, the retentive mechanism is a magnet or a ball attachment.The denture rests on the mucosal tissues and the attachments ensure retention only during lateral and extrusive movements.

A tissue-implant-supported overdenture provides retention via a superstructure on two implants interconnected by a bar attached to two gold caps that are screwed onto the implants. This denture rests on the mucosal tissues on the dorsal denture-bearing areas and on the bar and implants in the anterior regions; the bar is the axis over which the denture can rotate Retention is ensured during lateral and extrusive forces. During “intrusive” forces, the implants carry the occlusal loading of the denture in the anterior region, but in the dorsal region of the denture-bearing area, the mucosal tissues are loaded.

An implant-supported overdenture placed on four implants rests primarily on the superstructure connected to the implants. In most situations, the superstructure is placed on four interconnected implants. During occlusal function the mucosal denture-bearing areas are minimally loaded.

There are several arguments in the literature to indicate a preference for one of the three treatment strategies. Challenges are discussed such as pain caused by denture pressure, the amount of available bone, the expected level of oral hygiene, patient expectations of the new appliance, and the maxillomandibular relationship, as well as therapy cost effectiveness. ^10,14 While many studies have been published on implants and overdentures, only a few have compared the above-mentioned treatment options. The only study design that allows for a comparison of different types of treatment for patients with the same problem is a randomized controlled clinical trial.^15,16 Several randomized clinical trials on implant overdentures can be found in the literature.^17-26

Treatment success is determined by more factors than the survival of the implants alone. An important factor in patient treatment is patient satisfaction. When there are multiple treatment options for edentulous patients, it is important to determine how the patient perceives the treatment and how satisfied he or she is after treatment. It also is important to consider the clinical perfo rmance of the entire treatment strategy. Next to peri-implant and radiographic parameters, problems concerning prosthetic maintenance must be taken into consideration. Another important consideration is the efficacy of the treatment. Evaluation of the total results of patient satisfaction, costs, and treatment aftercare provides insight into the total treatment result and can be compared for the three different treatment strategies.

This chapter describes the patient satisfaction, type and amount of prosthetic aftercare, and clinical perfo rmance associated with mandibular overdentures on dental implants. Overdentures on four interconnected implants are significantly more expensive to provide than are overdentures on two implants, and both types of denture are equally acceptable to patients. This means that mandibular overdentures on two implants is the more favorable option in implant overdenture treatment. Furthermore, the two-implant overdenture with bar retention is more cost-effective than the two-implant overdenture with ball retention, mostly because patients were more satisfied with the fo rmer while the long-term costs involved with the aftercare of both is about the same.