Overdentures Versus Fixed Prostheses

Two concepts of prosthetic restorations exist for the edentulous jaw: the fixed prosthesis (mostly screw retained) and the overdenture. It appears that overdentures are preferably placed in old patients and in compromised situations. Since the eighties, a series of studies - including longterm results - have demonstrated the reliability of treatment with fixed prostheses for the upper and lower jaw. An increasing number of studies on mandibular overdentures supported by only two implants give evidence of the effectiveness of this treatment modality. Comparable data for maxillary overdentures are still missing. While dentists tend to base the selection of the prosthetic design on the number of implants that can be placed, other criteria have to be considered: esthetic appearance, facial morphology and restitution of lost hard and soft tissues, costs of implant-prosthodontic treatment, stability of the prostheses, complications and adjustments required, assessment of individual needs. From an economic point of view overdentures supported by two to four implants might be preferred. Prosthetic methods in general and related to implants are not evidence based. They relay on clinical experiences, patients’ demands technical considerations and reports of success and failure. However, from clinical experience, well-designed clinical concepts have evolved and the benefit of the patients concerned appears to be high and obvious. The lecture will discuss the use of implants for prosthodontic rehabilitation in the completely edentulous jaw. Indications and various types of removable prostheses are presented and variations of design discussed. Biomechanical aspects of fixation and stabilization of prosthesis complete the overview

Prosthetic considerations

Implants have changed prosthodontics more than any other innovation in dentistry. Replacement of lost teeth by a fixed or removable prosthesis is considered to be a restitutio ad similem, while implants may provide a feeling of restitutio ad integrum. Implant prosthodontics means restoring function, aesthetics, and providing technology; biology and technology are combined. Placement of implants is a reconstructive, preprosthetic surgical intervention and is therefore different from most goals in oral surgery that consist of tooth extraction, treating infection and removing pathology from soft or hard tissues. Thus, implants are part of the final prosthetic treatment which encompasses functional, aesthetic and social rehabilitation. The patient's needs and functional status determine the goal of prosthetic treatment. Treatment outcomes in implant prosthodontics are survival of implants and prostheses, impact on physiological and psychological status, oral health-related impact on quality of life, and initial and maintenance costs. A variety of prosthetic solutions are available to restore the partially and completely edentulous jaw and more recently specific methods have been developed such as computer guided planning and CAD-CAM technologies. These should allow more uniform quality and passive fit of prostheses, and simultaneously enables processing of biologically well-accepted materials

Titanlegierung vs. CoCr-Legierung in der Teilprothetik : eine klinische Studie

Different types of titanium-alloys instead of CoCr-alloys have been tested as material for the framework of removable partial dentures (RPD). Adequate casting and processing techniques have been developed which enable to fabricate frameworks of complex designs and the problem limits porosity. This opened new possibilities for the use of titanium-alloys with improved properties (E-module). The aim of this study was to summarise the use of titanium in removable prosthodontics and to evaluate prospectively the use of the Ti6A17Nb-alloy for RPDs in a small group of patients. Two identically designed RPDs from CoCr-alloy (remanium GM 800+) and Ti6A17Nb-alloy (girotan L) were produced for ten patients. They had to wear each RPD during six months, first the CoCr-RPD and then the Ti6A17Nb-RPD. A questionnaire (visual analogue scale = VAS) was completed by the patients after one, three and six months of function for each RPD. Prosthetic complications and service needed were recorded. After the end of the entire observation period of twelve months, the patients remained with the Ti6A17Nb-RPD and answered the questionnaire after another six months. All parameters regarding the design of the RPDs were positively estimated by the dentist. Minimal, not significant differences were noted by the patients concerning comfort, stability and retention (VAS). Clinically, no differences in technical aspects or regarding biological complications were observed after six-months periods. The Ti6A17Nb-alloy (girotan L) for the framework of RPDs was judged by patients and professionals to be equivalent to RPDs made from CoCr-alloy. No differences in material aspects could objectively be observed. The Ti6A17Nb-alloy can be beneficial for patients with allergies or incompatibility with one or several components of the CoCr-alloy