Biomedical subjects
Publications and source records attributed to H Jakstat.
An expert system for treatment planning in cast clasp partial denture cases is presented. The system may be used both to verify the construction principles of proposed clasp constructions and to develop new constructions. At first, it is intended to use this expert system for teaching in university dental schools.
In this study the clenching force was measured, which 12 patients used, while the needle-point tracing was in progress. The patients were not instructed about the measurement. The results show, that 10 of 12 test persons used higher clenching forces, when they had to do border movements according to verbal instructions then when doing free movements of the mandibula. All test persons showed peaks in the level of the clenching force, which were clinically accompanied with swallowing.
The effect of the positioning of the needle in the horizontal plane and the applied clenching force on the result of the needle point tracing was investigated. The results show a strong influence of the applied clenching force. The results on the variation of the needle position leaded to the conclusion, that in the progress of the needle point tracing the lower jaw is balanced over the central bearing point.
Chewing forces were measured in a needle point tracing while the patients could view their actual and the proposed chewing forces (5 N, 10 N and 30 N) on a computer screen (biofeedback). Most probands used less than the proposed forces in the experiments. All probands approached the proposed level of force step by step. Fatigue of the chewing muscles led to a change in the Fourier-transformation of the recorded samples: An increase in short-waved components (frequencies of approximately 1 Hz) was found.
Acrylic, plaster and polyether were evaluated for their accuracy in indexing needle point registration. Additionally, a new experimental system was tested, that permits the dentist do immediately verify the accuracy of the recording. Best results were obtained when the indexes were not removed from the occlusal plane plates. When the indexes were dislodged, acrylic and plaster demonstrated the most accurate results in repositioning the occlusal plane plates. The experimental system demonstrated comparable accuracy to both, acrylic and plaster.
The prevalence of prosthetic reconstructions among 1534 German recruits (mean age 21.8 years) was evaluated. Of the total number of single crowns (n = 552), 72% were found in the upper jaw. Forty-one per cent of the crowns were situated in the upper incisor region. Four per cent of the probands received mostly three-unit-bridges and 0.9% removable partial dentures. In 3.7% of the cases all missing molars of a quadrant were not prosthetically replaced. The number of single crowns and bridges was not associated with the final school education, which in its term is closely associated with the social stratum. Between the level of school education and the need of prosthetic treatment a highly significant association was found.
In several experiments it was examined, whether slight deviations from the using reglementation for the PERIOTEST-device alter the measurement results. Tilting of the handpiece against ground or variation of the distance between handpiece and the surface of the tooth within the suggested intervals did not alter the PERIOTEST-value. If the measurement was done more incisal then specified, the PERIOTEST-value increased, if the measurement was done more cervical, the value decreased. Tilting the handpiece against the tooth surface within +/- 8 degrees in horizontal and +/- 6 degrees in vertical direction gave only little effect on the PERIOTEST-value on clinical firm upper front teeth.
With the help of video- and computer techniques is investigated in what respect the forces operating in intraoral tracing pin registration have an influence on the mandibular movement at the sagittal plane. The results significantly show this dependence.
The mobility of soft tissue points used for measuring the rest vertical dimension was assessed in 29 probands with full dentitions and 24 edentulous subjects. A video-aided procedure was used for recording the measuring pictures. Similar results were obtained with fully dentulous and edentulous subjects. For the upper jaw the point of the nose was the mark undergoing the least fluctuations, due to the action of the mimic muscles. For the lower jaw the least mobile skin area was between the labiomental sulcus and the gnathion.
In a survey the methods and materials used for making complete dentures were collected from 603 dentists. The impression material most frequently used for primary impressions was alginate and elastic impression material for functional impressions. Compared with an earlier survey the percentage of dentist using needle point tracing for recording jaw relations increased from 6 to 40%. Remounting complete dentures was done by 64% of the dentists whenever required; 9% applied this method as a routine.
It was the purpose of this study to assess the influence of the applied clenching force and the positioning of the needle in the sagittal plane on the results of needle point tracings. The results show a direct influence of the applied force, whereas the influence of the position of the needle point showed great interindividual variations.
Overjet was measured three times in 46 edentulous patients treated with complete dentures with cuspless teeth: 3 to 5 days after insertion of the new dentures, after 4 weeks and after 10 months. Despite the lack of cusps for fixing the occlusion we found only little overjet reduction.