PROSTHETIC RECONSTRUCTION OF DENTITIONS SERIOUSLY COMPROMISED BY PERIODONTAL-DISEASE

Dentitions seriously compromised by periodontal disease are often in need not only of cause-related periodontal therapy of high quality but also of relevant prosthetic rehabilitation. Contrary to traditional claims, clinical investigations published during the last 2 decades demonstrate that, if adequately treated and controlled, such dentitions can carry fixed, cross-arch bridges on an extremely reduced amount of periodontium, with a good long-range prognosis. It has also been shown that a markedly reduced but healthy and favourably distributed periodontium supporting such constructions can withstand occlusal forces of considerable magnitude. Another controversal topic, related to fixed bridges, involves indications and contra-indications for cantilever segments. Some clinical investigations demonstrate a markedly increased risk of failure if the fixed bridge is provided with cantilever units, while other controlled studies with defined specifications on the design of the constructions exhibit a high success rate after 8 years or more also for bridgework where 2 or 3 cantilever units are included. The force pattern along cantilever segments of both tooth-supported and implant-supported bridges has been extensively studied. The results show that the force distribution depends not only on the occlusal contact pattern and the dimensioning of the cantilever beam, but also on the type of prosthetic construction in the opposite jaw occluding with the cantilever segment. The free-standing, implant-supported bridge has recently become an important treatment modality for rehabilitation of the partially edentulous jaw, and follow-up studies demonstrate a high success rate. Prosthetic connections between natural teeth and implants have also been reported to have a good prognosis without incorporation of elastic elements in the constructions, provided that factors such as occlusal force pattern, tooth mobility and beam dimensioning are taken into consideration. Other factors influencing the force distribution in such constructions are size, type and number of implants as well as the jaw bone quality.