Problems Related to Occlusion with Complete Upper and Partial Lower Dentures

Abstract

The main objectives in the construc­ tion of complete upper dentures and partial lower dentures should be the restoration of masticatory efficiency and “ the perpetual preservation of the re­ maining structures,” (M. M. DeVan). The other objectives, retention, stability, comfort, esthetics and patient satisfac­ tion, should of course be recognized and striven for by the operator. The problem of occlusion is related to the satisfactory completion of the above objectives. This problem is simplified if the partial lower denture is primarily tooth-borne, for then the problems would be comparable to those involved in constructing a complete upper denture to occlude with a full complement of natural mandibular teeth. This discussion, however, will consider only those problems arising when a pa­ tient is completely edentulous in the upper jaw and has six lower anterior teeth. An intelligent understanding of oc­ clusion presupposes a knowledge of mandibular movements for it is during masticatory function that the prosthetic appliances will be placed under the great­ est stress. The physiologic act of mastica­ tion can be divided into incision, the actual mastication and finally, the swal­ lowing of the bolus of food. The lips, cheek, tongue, palatal area, all asso­ ciated musculature and mucosa, as well as the teeth and their supporting struc­ tures are directly related to this masti­ catory cycle and are dependent on one another for its successful completion. This paper will be primarily concerned with the direction of the forces exerted on the teeth and their support during the actual mastication of food. This mandibular movement can be roughly classified in two divisions; the functional and nonfunctional movements. There is some overlapping of these divisions which will be explained later. The nonfunctional movements also can be placed in two categories: ( 1) the mandibular glide, or movement determined solely by the tem­ poromandibular articulation and its mus­ cles and ligaments and the occlusal or incisal surfaces of the remaining teeth and (2) the “ free movements” 1 of the mandible where there is no tooth contact. Unfortunately, in the past, functional mandibular movements have been de­ scribed as being synonymous with the nonfunctioning glide. Theories of occlu­ sion were based on this nonfunctional movement and articulators were devised to follow these movements. “ It is not for one moment disputed that workers who use individual measurements of condyle