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T L Hansson

Publications and source records attributed to T L Hansson.

48 records · Page 3Linked to original sources
PubMed1986

Malocclusion associated with temporomandibular joint changes in young adults at autopsy.

The purpose of this study was to identify variables of malocclusion that might be associated with previously reported temporomandibular joint morphologic findings. Before removing the left TMJ from each of 96 cadavers (age means equals 26.4 +/- 6.8 years), an intraoral examination was performed. Angle classification, crossbite, overbite, and overjet were evaluated. These parameters were analyzed with respect to their association with the following TMJ features: overall shape of the condyle and temporal bone, gross and histologic evidence of remodeling, and position of the articular disk. When combined with age, Angle Class II and III dentitions were associated with temporal and condylar deviation in form (DIF) (P less than 0.05) and more Class II dentitions were accompanied by histologic evidence of remodeling changes in the TMJs. Crossbite was associated with increasing presence of DIF in all components (P less than 0.01). Anterior crossbite was associated with DIF on the articular eminence (P less than 0.01). Deep overbite was more common in persons with flat condyles, open mandibular fossae, and anterior extension of the temporal articular surfaces (P less than 0.05). Abnormal overjet was more evident in those with DIF in the disk (P less than 0.05); greater overjet was associated with disk displacement (P less than 0.05). Considered together, abnormal overbite and overjet were associated with more extensive DIF on the condyle (P less than 0.05). In conclusion, malocclusion was associated with morphologic changes in the TMJ, particularly when combined with age. This evidence supports the belief that longer exposure to malocclusion may be associated with more extensive TMJ changes.

Adolescent↗
PubMed1986

Electromyographic power-spectrum changes during repeated fatiguing contractions of the human masseter muscle.

During 7 sessions at weekly intervals, 10 healthy males performed the same endurance test three times by isometrically contracting the masseter muscles at 20, 30, 40, 50, 60, 75 or 90 per cent of maximal electromyographic activity. The interval between the tests in any one session was 30 s. Changes in the surface electromyogram were monitored by calculating the changes in mean power frequency (MPF) of the signals. With the higher contraction levels, endurance times were shorter, the MPF shifted to lower frequencies more rapidly and the MPF value was lower at the end of the test. At these levels, the subjects reported lack of power as the sole reason for stopping the test but at low levels, pain was the important reason. The endurance time and the rate of MPF shift for the second and third test of each experiment were the same. For the first test, the endurance time was longer (p less than 0.025) and the rate of MPF shift was lower (p less than 0.05). Thus the analysis of specific electromyographic (MPF) indicators provides information about the development of muscle fatigue.

Adult↗
PubMed1986

Electromyographic screening of myogenous and arthrogenous TMJ dysfunction patients.

Sixty patients, clinically examined for TMJ dysfunction, were also electromyographically screened. The TMJ dysfunction pain in forty patients was evaluated to be mainly of a myogenous origin and in fourteen patients of a mainly arthrogenous origin. Due to lack of findings in the clinical examination six patients were not to be classified into either of the two groups. They were excluded from the EMG study. For the EMG examination the patients were asked to clench for 30 s in the intercuspal position at 50% of the maximum EMG activity of the masseter muscles. Surface electromyograms of the right and the left masseter and anterior part of the temporalis muscles were monitored. The amplitude of the EMG signal, the duration of the silent period and the changes in the frequency composition of the signal during the 30 s contraction were analysed. Statistically significant differences between the two patient groups were found in EMG amplitude and in silent period duration. However, the difference in silent period duration was due to the dependency of the silent period on the activation level of the muscle. No statistically significant difference in silent period was found when this dependency was corrected for in the data. The EMG parameters related to muscular fatigue phenomena did not show any difference between the two groups. The difference in EMG amplitude and consequently the difference in silent period duration support the clinically made distinction into mainly a myogenous or mainly an arthrogenous origin of TMJ dysfunction pain.

Adult↗
PubMed1985

Histomorphometric analysis of cartilage and subchondral bone in mandibular condyles of young human adults at autopsy.

After demineralization, sagittal sections were made from the lateral, the central and the medial parts of 33 mandibular condyles from people aged 20 to 36 years, and studied for undifferentiated mesenchymal (UM) cells, cartilage and subchondral bone, the thickness of which were measured. Two condyles showed a continuous layer of UM cells extending all over. In 13 condyles, UM cells were absent; 18 condyles showed variability in UM cell occurrence in one or more out of the nine standardized areas. In 14 condyles, non-hypertrophic cartilage was present, 10 condyles showed hypertrophic cartilage and in nine condyles hyperplastic cartilage. Hyperplastic cartilage was associated with minimal numbers of UM cells. In combination with hypertrophic cartilage the UM cell layer appeared less irregular. Of nine condyles with incongruence of the cartilage-bone interface and the articular surface, seven showed hyperplastic cartilage. Six out of these seven were free of bony changes. A negative correlation was found between the presence of UM cells and the condylar-cartilage thickness (p less than 0.05). These results suggest that condylar changes are initiated by alterations in the cartilage and that changes in the bone are secondary.

Adult↗
PubMed1985

The temporomandibular joint in young adults at autopsy: a morphologic classification and evaluation.

Macroscopic features of temporomandibular joints (TMJs) were studied in young adults who comprise the largest portion of individuals seeking TMJ treatment. Deviation in form (DIF), arthrosis, size, shape and disc displacement were evaluated on ninety-five autopsied TMJs. Few TMJs (13%, 12/95) showed no intracapsular changes. Thirty-nine per cent (37/95) of the TMJs displayed mild-to-marked DIF in all three TMJ components. Smaller changes were more prevalent and tended to appear in the younger TMJs. Condylar changes were more exuberant and extensive compared to the other components. Minor arthrotic lesions were visible in 3% (3/95), and all displayed DIF. Disc displacement was found in 12% (11/95) and was more common in women (P greater than 0.05). Folding and deformation of the articular disc was associated with disc displacement (P less than 0.01), the direction of which was mostly anteromedial. Most of the unchanged condyles' components had curved, slightly rounded, convex, and elliptical shapes when viewed from different planes (P less than 0.01). Applied in diagnosis, the presence of DIF can be inferred from features which deviate from the above shapes. The concept that the above macroscopic changes might be a precursor to TMJ arthropathy in susceptible individuals is compatible with the results of this study, but the most apt characterization is that TMJ changes in this age group are adaptive phenomena occurring in order to cope with the details of articular fit and function.

Adolescent↗
PubMedDate not supplied

Condylar-mandibular asymmetry, a reality.

The aim of this study is to evaluate the possibility to recognize a condylar-mandibular asymmetry through a panoramic radiograph. Results from a previous work, in which 100 skulls from the Museum of the Institute of Anatomy of the University of Pavia were studied and measured, showed the presence of asymmetry. Using the same skulls we examined the possible correlation between morphological and radiological data. We did not find out correlation's between the condylar asymmetry evaluated at the anatomical level and the radiological asymmetry which was indeed found. This is probably due to the different positioning of the jaws during the two different measuring processes. Nevertheless our results confirm the daily experience of dentistry: asymmetry of mandibular condyle can be one of the mayor causes for the asymmetry of the stomatognatic apparatus.

Algorithms↗