A. Albert Yurkstas

Force analysis of prosthetic appliances during function

Abstract A study has been conducted to evaluate the vertical forces that are placed on the teeth of full and partial dentures during mastication. Relatively small forces were required for the mastication of most foods commonly found in the diet. Maximum forces up to 12 kg. have been recorded while chewing rolls and certain breads in the prosthetic situations. Six to eight kilograms were the most common maximum forces required. Most foods required an average force ranging from 0.3 to 1.8 kg. for mastication. Even though the average maximum biting force that denture wearers can exert is approximately 12 kg., they still possess an adequate force capacity to masticate the great variety of foods appearing in the diet. Full denture and partial denture wearers utilized similar forces during mastication. Ingestion of liquids with certain foods by two denture wearers reduced the maximum forces and the total kilogram strokes used during mastication by about one-half. Cooking foods reduced the maximum forces by 50 to 75 per cent and also reduced the total forces needed to reach the swallowing point by 83 to 96 per cent.

Dietary selections of persons with natural and artificial teeth

Abstract The food preference of subjects with natural dentitions was compared with the food items selected by subjects wearing dentures. Results indicated that denture patients tended to avoid foods that were difficult to chew, such as meats, raw vegetables, sandwiches, and salads. Patients with natural teeth ate less cheese, processed fruit, fish, raw fruit, eggs, cereals, bread, and cooked vegetables.

The effect of missing teeth on masticatory performance and efficiency

Abstract Masticatory performance and efficiency data from the laboratory of Oral Physiology at Tufts College Dental School have been assembled in groups according to teeth in occlusion. This was an attempt to evaluate the effect of missing teeth on masticatory performance and efficiency. A series of 741 individual determinations have been presented in table form. It was noted that the loss of the first molar tooth resulted in a drop of 33 per cent efficiency. Losing the second and third molar resulted in a drop of 44 per cent. A first and third molar loss resulted in a drop of 66 per cent. The average masticatory efficiency of denture wearers was 24 per cent. Wide variations in masticatory efficiency were demonstrated among individuals possessing the same types and numbers of teeth in occlusion. Counting the number of teeth in occlusion was of little or no value in determining masticatory efficiency.

The influence of geometric occlusal carvings on the masticatory effectiveness of complete dentures

Abstract A study of 20 edentulous subjects was made to evaluate the effect of 4 cuspless geometric occlusal patterns on the chewing efficiency of complete dentures and to compare the masticatory effectiveness of these grooved patterns with similar patterns of raised metal inserts. Results of the tests showed no significant difference in effectiveness among the patterns tested. However, after a year of experience with a given pattern, masticatory efficiency was significantly improved. After three months of experience with metal insert patterns, the patients showed a definite improvement in masticatory performance. Dentures with occlusal configurations on both upper and lower posterior tooth segments seemed to be more effective than dentures with one or both opposing segments free of occlusal markings.

A functional evaluation of fixed and removable bridgework

Abstract Removable and fixed prosthetic appliances were constructed for each of twenty subjects in order to replace a missing first molar. (In two cases the second bicuspid was also restored.) Masticatory performance tests with soft and tough foods were made before, immediately after, and one and two weeks following the insertion of the appliance. The degree of pulverization before swallowing and the time and chewing strokes required per mouthful were obtained for each subject at each period. The insertion of either fixed or removable appliances caused a statistically significant increase in masticatory performance with both hard and soft foods. The two appliances were about equivalent in their effect. Masticatory performance was generally higher after appliances were in place for a two-week period, indicating that individuals learned to use both fixed and removable appliances more efficiently within this time. The duration of this learning period has not been determined. Subjects with a diminished masticatory capacity swallowed larger particles of food than did those with a normal or superior masticatory performance. Upon the insertion of fixed and removable appliances, most individuals immediately used fewer strokes to pulverize their food finer at the swallowing point. After two weeks of usage, the patients required seven fewer masticatory strokes and six seconds less time per mouthful and at the same time achieved 16 units greater pulverization than they did previous to the insertion of the partial appliances.

Decreased masticatory function in denture patients

Abstract A group of denture subjects were studied for their ability to chew a test food at 10, 20, 40, 60, and 80 strokes. Comparison of findings with those of subjects with natural teeth indicates that most denture patients are even more handicapped than had previously been supposed. The group studied had an average efficiency of 12 per cent, less than one half that of previous findings.

The sublingual crescent extension and its relation to the stability and retention of mandibular complete dentures

The extension of the flange in the sublingual crescent region is an important factor for mandibular denture stability and retention. Making the impression with minimal pressure on the floor of the mouth while the tongue is at rest allows greater mobility of the underlying muscles without denture dislodgment and without occlusion of the sublingual gland ducts. The anatomy of the sublingual crescent region and the clinical procedure for recording the anterior lingual seal region are described. Upon completion of the impression, resistance to dislodgment is usually achieved.

The coronomaxillary space: Literature review and anatomic description

The dental literature has used a variety of terms to describe the distal buccal boundaries of the maxillae. The coronomaxillary space has been suggested as a more consistent descriptive term. It has been noted in the literature that this space narrows on mandibular opening. However, some authors recommend that overfilling this space aids retention. Explanations for this seeming contradiction in opinions have been suggested: In individuals with straight coronoid processes, the space can narrow on opening. The coronomaxillary denture may have to be thinned to maintain retention in function. In individuals with flared coronoid processes, the space can widen or remain constant on opening. The denture borders may have to be widened in contour to achieve retention.