The present study evaluated the connection between temporomandibular disorders (TMD), maximum voluntary bite force and oral health-related quality of life (OHRQoL) in patients with oral cancer. Twenty-six prosthetically rehabilitated patients with partial resection of the upper and/or lower jaw with segmental mandibulectomy, with and without reconstruction, were examined. The examination comprised the Research Diagnostic Criteria for TMD (RDC/TMD), determination of the individual pain threshold, evaluation of the maximum voluntary bite force, and OHRQoL according to the Oral Health Impact Profile (OHIP) questionnaire. Male pain thresholds were significantly higher than female pain thresholds (P=0.003). Patients with maxillary resection showed higher pain threshold values than patients with (segmental) mandibulectomy. Bite force was significantly (P=0.000014) lower in resected jaw areas than in healthy ones. Patients with resections of the maxilla showed higher voluntary bite forces than patients with resections of the mandible; males showed higher bite forces than females. The prevalence of negative responses ("often"-2 and "very often"-1) on the OHIP items was 10.39%, whereas the prevalence of positive responses ("from time to time"-3, "seldom"-4, and "never"-5) was 89.60%. The prevalence for negative responses was 2.46% in male patients and 8.07% in female patients. Patients with resections in the maxilla suffered from negative responses of 3.92%, patients with resection of the mandible of 6.64%. According to the OHIP, the psychological disposition of these patients clearly referred to coping mechanisms.
In a dentate subject a jaw relation can either be determined in maximum intercuspation and is as such given by the occlusal morphology, or the mandibular position can be allocated according to the centric position of the condyles. For comprehensive restorative treatment or analytic measures of the occlusion it is important to record the centric condylar position. Various registration methods have been described in the literature, but there is no consensus on which is the 'best'. The aim of the present study was therefore to assess the accuracy of various registration methods and evaluate a possible influence of the used materials. Four dentists were involved in the clinical part of the study, another was responsible for the measurements. Impressions were taken from 81 fully dentate volunteers. The casts were mounted by face-bow transfer and central-bearing-point (CBP) registration into Dentatus articulators. Subsequently the centric condylar position was determined with six different methods and materials, respectively. Each method was reproduced twice so that a total of 18 registrations was performed per patient. The mandibular positions which resulted from the individual registrations were then repeatedly compared in the condylar area using a computer supported specially modified measuring articulator. The accuracy was found best for the unrefined wax wafer registration (x=0.33 mm) and with an average of 0.44 mm worst when using acrylic wafers. The CBP and frontal jig methods as well as tin-foil and refined wax wafers showed an accuracy in-between these boundaries. The biggest measured mandibular displacement between any two registrations were considerably 2.0 mm. However, the described differences in accuracy between the various methods and materials proved statistically not significant. All investigated jaw registrations showed an accuracy of about 20 times the tactile fine sensibility of natural teeth which has to be taken into account when inserting fixed prosthetic restorations in centric condylar position. Despite meticulous clinical and technical procedures small occlusal adjustments are therefore almost unavoidable.
Orthodontic therapy of frontal crowding is not just an esthetic problem but can be of special importance in the prevention of stress-related reactions in the masticatory system.
The conventional fabrication of complete dentures involves two separate clinical sessions for functional impression making and jaw registration. The presented method combines both procedures in one session. The aim of this study was to survey the three-dimensional tooth positions in complete dentures with reference to the ridges to establish arbitrary guideline values that could be used for the manufacturing of tooth-position analogue plastic rims on functional impression trays. New complete dentures were fabricated by supervised undergraduate students in the conventional manner for 104 edentulous patients. The position of the maxillary teeth was surveyed in the horizontal plane using the Schmuth 'vizor-measuring plate'. The vertical dimension of occlusion, represented as the distance between opposing ridge areas of the dentures in maximum intercuspation, was measured at different sites by means of a Gutowski gauge. The tooth positions on the dentures varied widely, e.g. the horizontal distances between the incisive papilla and the maxillary incisors was 7.1 +/- 2.3 (3-14) mm. The vertical dimension of occlusion, which is most important in the jaw registration, varied equally with an anterior inter-alveolar distance between 12 and 33 (20.4 +/- 4.0) mm. Arbitrary moulding of the tooth position-analogue plastic rims does not seems to be an ideal method of pre-shaping functional impression trays, because the individual anatomical variation is considerable. Alternatively, the horizontal and vertical tooth positions of functionally and aesthetically pleasing dentures should be measured to pre-shape the rims of functional impression trays in the maxillary and the mandibular jaw. Such trays are a valuable tool for functional impressions and an immediate preliminary jaw registration in the fabrication of new complete dentures. This method allows a first try-in of the full set-up in the third clinical visit without loosing precision.
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