Observations on Some Jaw Relationships During Swallowing As Related to Prosthetic Dentistry

Laird, William Ronald Edwards (1973) Observations on Some Jaw Relationships During Swallowing As Related to Prosthetic Dentistry. Doctor of Medicine and Surgery thesis, University of Glasgow.

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Abstract

This work has investigated some of the jaw relationships which may occur during swallowing in both dentulous and edentulous persons. The study was stimulated by an appreciation of the problems which may be encountered in the registration of correct relationships between the mandible and the maxilla when constructing dentures for edentulous patients. These relationships exist in both vertical and horizontal planes. When they are recorded incorrectly, it is a common clinical experience that the comfort and function of complete dentures is adversely affected. Numerous methods are used to determine and record jaw relationships, and the literature on the subject is extensive. This literature has been reviewed and discussed and the various methods for recording jaw relationships have been summarised as a) nonfunctional methods, and b) functional methods. Non-functional methods may be used either before or after extraction of the natural teeth. In general, however, they do not appear very reliable. Functional methods are based on movements of the jaws and associated parts, in the edentulous state. They include speech, mastication and swallowing. Of these functions, swallowing is a simple and natural procedure which most persons can perform, is not easily disturbed and appears to be a particularly suitable method for recording jaw relationships of edentulous patients. The rationale behind this method is based on the belief that in dentulous persons, swallowing is accompanied by contact of the occlusal surfaces of the opposing posterior teeth. It is also believed that in the edentulous state, the relationship of the mandible to the maxilla during swallowing is similar to that which occurs with the natural teeth present. The recording of this position therefore would permit a clinician to construct complete dentures to natural jaw relationships. Reports regarding jaw relationships in dentulous persons during swallowing reflect a diversity of opinion, whilst the information regarding jaw relationships during swallowing for edentulous persons and persons wearing complete dentures is sparse and inadequate. The present study therefore, was directed to the investigation of jaw relationships during swallowing with particular reference to the incidence and position of occlusal tooth contact in dentulous subjects, and the level of vertical jaw separation in edentulous subjects. In addition observations were made regarding jaw relationships during swallowing in subjects wearing complete dentures, and the effect which certain modifications of these dentures had on the jaw relationships. The major part of the investigation employed fluorographic techniques, although some investigations on dentulous subjects were performed using an intra-oral transmitting coil linked to a potentiometric recorder. In the fluorographic study, subjects were exposed to X-rays while swallowing water. An image was produced on a fluorescent screen and photographed by a television camera which was built into the apparatus. Viewing was carried out as sequences were performed and the television picture was also recorded on video tape for later analysis. The apparatus incorporated an electronic image intensifier, which by increasing the brightness of the fluorescent screen resulted in a considerable reduction in radiation dosage. Investigations, which were restricted to the sagittal plane, were performed on 70 volunteer subjects, both dentulous and edentulous. Analysis of the results used both visual and measurement techniques. As direct measurement from the video tape was impossible, each sequence was filmed from the television screen using a 35 mm camera with a motorised transport system. A frame analysis was performed and in order to obtain more detailed measurements, prints were made from relevant frames. All measurements were made relative to an established reference position. Errors in the materials used, the techniques employed and the methods of analysis were examined. It was concluded that errors in the materials used and measurement and observer errors in the techniques employed were small, and unlikely to have any appreciable effect on the results. The methods of analysis, however, occasionally demonstrated some bias towards the reference measurement and where present this has been stated. Random errors were also examined, and although they could not be entirely eliminated were controlled and considered to be minimal. The results of the investigation on the selected sample of subjects confirmed the opinion that, in dentulous subjects, occlusal tooth contact does occur during swallowing. It was not present in all subjects however, and some subjects demonstrated contact in some swallowing sequences and not in others. The position of contact when present was normally with the teeth in the intercuspal position as defined in the study. Edentulous subjects demonstrated a reproducible vertical jaw relationship during swallowing. This finding confirmed the rationale of using the action of swallowing to establish jaw relationships in the vertical plane.

Item Type: Thesis (Doctor of Medicine and Surgery)
Qualification Level: Doctoral
Keywords: Dentistry
Date of Award: 1973
Depositing User: Enlighten Team
Unique ID: glathesis:1973-78623
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:08
Last Modified: 30 Jan 2020 15:08
URI: http://theses.gla.ac.uk/id/eprint/78623

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