The stereostethoscope--an instrument for clinical gnathosonics

Duration patterns of percussion sound in healthy and periodontally affected teeth

Ten periodontally affected subjects and 10 healthy subjects were selected in order to examine the duration patterns of percussion sounds in all upper teeth, excluding the 8's. Probing depth, loss of attachment, tooth mobility by 'Periotest', bone loss and percussion sound duration via occlusal sound analyser were recorded during the pretreatment period. The following results were obtained from the study: (i) the normal duration of percussion sounds ranged from 4.40-5.33 ms; (ii) percussion sound values of periodontal patients were of longer duration than those of healthy subjects; (iii) a close correlation between duration and other individual parameters was found in all upper teeth, with the exception of molars.

Relative influence of plaque control, scaling and root planing on occlusal sounds

Nine periodontally affected subjects and eight healthy subjects were selected in order to examine the effect of initial periodontal treatment on occlusal sounds. Gingival Index, probing depth, tooth mobility and occlusal sound duration via an occlusal sound analyser were recorded at the baseline. The nine periodontal patients were then treated by plaque control, root planing with general scaling and were re-examined at 1 month and 3 months post-operatively. The following results were obtained: (i) The normal duration of an occlusal sound is less than 10 ms. (ii) Occlusal sounds of periodontal patients were of longer duration compared with values in healthy subjects, but decreased and approached the normal value after treatment.

Post-orthodontic occlusal function

The significance of orthodontic treatment in the aetiology of temporomandibular dysfunction continues to be a matter of controversy. However, the evidence of any association has been generally negative. This investigation involved the examination of a study group of 87 post-orthodontic patients, the average time out of all retention being 52 months. They were compared with an untreated control group. Signs and symptoms of temporomandibular disfunction were assessed for both groups. In only one instance, soft joint click, was there found to be a significant association between the treatment category and the occurrence of the symptom, there being a higher rate of soft clicks in the post-treatment group. While this may be ascribed to orthodontic treatment, there was also a different restorative pattern in the two groups. No other significant associations were found.

The reproducibility of gnathosonic recordings over time

Gnathosonic recordings are obtained on rapid closure of the teeth to occlusion. A general relationship between gnathosonic tracings and occlusal contact patterns has been demonstrated. Variation of gnathosonic recordings over time for the same individual has not been satisfactorily investigated. The present study suggests that recordings taken at the same sitting are relatively reproducible but reproducibility over time is not high. The series of recordings obtained in this study suggests caution when interpreting a single series of gnathosonic tracings.

The clinical significance of median occlusal position

The harmony of the occlusal components of the teeth, mandibular joint and muscles, were investigated in 180 human subjects by clinical, dental articulator, radiographic and electrodiagnostic methods. Significant correlations were found between disharmony of these components at median occlusal position (MOP), and with pain-dysfunction of the masticatory system. Using the standardized stimuli of opening the jaw wide and snapping it shut automatically into MOP, temporalis and masseter muscle co-ordination and somesthetic reflex effects were quantified. The interval from tooth contact (s) to reinstitution of EMG activity (x), and the EMG silent-period duration (SP), were prolonged in the patients but returned to within the control range with elimination of the pain-dysfunction. Muscle incoordination with mandibular dysfunction was prevalent in the patients, and the incidence of osteoarthritis was greatest in those with persistent symptoms. The hypothesis was supported that disharmony of MOP exists in pain-dysfunction patients--while successful occlusal therapy leads to the restoration of the harmony within the biologic range. This implies physiological significance to this hitherto clinically neglected occlusal position.

Tooth tapping ability of young and elderly males and females

The ability to perform high frequency tooth tapping movements was studied in young dentulous, elderly dentulous and elderly edentulous subjects of both sexes as a possible test of the overall efficiency of the masticatory motor apparatus and related structures. Tapping frequency was measured during a test period of 90s by counting the number of taps per 5 s intervals. It was found that observed values of tapping frequency could be fitted to an exponential equation with a high degree of fit for 90% of the young subjects and for 60% of the elderly subjects. The values of the remaining elderly subjects were best fitted to straight lines. The elderly subjects could thus be regarded as belonging to two different populations which were differently affected by advanced age and loss of teeth regarding their tooth tapping ability. Young dentulous subjects had the highest starting frequency (6-1 Hz) followed by elderly dentulous (5-5 Hz) and elderly edentulous subjects (4-9 Hz). The lower limits were 4-6 Hz for young dentulous subjects, 4-1 Hz for elderly dentulous and 3-7 Hz for elderly edentulous subjects. The average group means pointed all in the same direction that increased age and loss of teeth change the functional ability by deteriorating it.