David M. Watt

Temporomandibular joint sounds

Abstract The sounds of temporomandibular (TM) joints are described on the basis of a study of 191 patients with TM joint symptoms. Gnathosonic records were made for all of these patients, but synchronous mandibular movement records were made for only 30. A classification is proposed which takes into account the nature of the sounds (click or crepitus), their quality (hard or soft), their positions relative to mandibular movement (near, middle or wide) and whether the sounds occur on opening or closing of the jaws. Synchronous records of mandibular movement and of the sounds of the occlusion and TM joints are discussed. Possible causes of the sounds are suggested and reasons given for the alteration of the position of the sounds on opening and closing.

Gnathosonics—A study of sounds produced by the masticatory mechanism

Abstract A technique was described for recording the sounds produced by the masticatory mechanism. Findings indicated a relationship between the sounds of tooth contact, the quality of the muscle activity, and the nature of tooth contact. Separation noise created during mandibular opening was described and discussed. Tentative observations were made on gnathosonic data collected from a control group of 19 students and a group of 23 patients. The clinical applications of gnathosonics will be discussed in another article.

Tooth positions on complete dentures

Abstract Complete dentures should be constructed to fill the denture space, which may be defined as ‘that space in the edentulous mouth which was formerly occupied by the teeth and their supporting tissues which have since been lost’. The artificial teeth should be placed in the approximate positions occupied by the natural teeth. Various guides to the placement of artificial teeth in these positions are discussed: 1. 1. The form of the lips, the nasolabial and horizontal labial angles and the effect of nose form and tooth inclination on these angles. 2. 2. The relationship of the maxillary incisors to the incisive papilla. 3. 3. General rules for the arrangement of anterior teeth in cases of jaw and lip malformation. 4. 4. The location of the remnant of the linguogingival margins in the edentulous mouth and placement of upper teeth in relation to it. 5. Placement of lower teeth in relation to the lower ridge, tongue, cheek and lips.

Clinical applications of gnathosonics

Abstract Records of the sounds of occlusion of the teeth were made before, during, and after treatment of 23 patients. Where treatment resulted in improvement of the occlusion, the duration of the occlusal sounds diminished. Deterioration of the occlusion caused the sounds to be prolonged. The clinical applications of gnathosonic records were discussed, particularly in relation to the diagnosis and treatment of oral dysfunctions.

An analysis of temporomandibular joint sounds

Abstract Six thousand nine hundred and nineteen temporomandibular joint sounds made by 110 patients in 2200 opening- and-closing cycles were classified and analysed. On average there were three TMJ sounds in each cycle. Fifty-nine per cent of the sounds occurred on opening and 41 per cent on closing. Only 27 per cent of the sounds were clicks and 73 per cent were crepitus. The average duration of hard TMJ clicks, excluding background crepitus, was 10 ms and the average duration of soft clicks was 14 ms. Eighty-six per cent of all the sounds (clicks and crepitus) were soft and 14 per cent were hard. Ninety-four of the patients were studied more closely: 17 had only opening clicks, 7 had only closing clicks and 43 had reciprocal sounds; 28 had groups of 20 consecutive sounds, but in only 5 did they occur in both opening and closing. The significance of these findings is discussed.

Gnathosonics in occlusal evaluation

Abstract 1. The technique of gnathosonic recording is outlined. 2. Evidence is presented which supports the hypothesis that the visual records of sounds of tooth impact provide analogues of occlusion. 3. A tentative functional classification of occlusion is suggested. 4. The use of gnathosonic records to evaluate occlusion during the treatment of patients is illustrated.

Biometric trays for complete denture construction

Abstract Biometric impression trays are designed to support the lips and cheeks in their pre-extraction positions. The tray design is based on the average buccolingual breadth measurements of the dentulous alveolar process. The transference of these measurements is possible as the remnants of the lingual gingival margins can be identified on edentulous casts. The method of making the trays is described. The advantages of biometric impression trays are such that over the past five years they have replaced conventional impression trays for complete denture work in Edinburgh.