Biomedical subjects
Publications and source records attributed to R G Behrents.
This paper reports the management of a patient with severe localized periodontitis accompanied by drifting and extrusion of a central incisor. Although the traditional treatment approach to this condition often includes extraction and prosthetic replacement, the approach presented here provides an alternative to extraction by combining periodontal and orthodontic treatment.
Hydrostatic synovial fluid pressure within the superior aspect of the temporomandibular joint space of the growing pig, Sus scrofa domesticus, was examined in response to various acute and chronic alterations of mandibular position. Bilateral measurements of pressure were recorded with chronically implanted wick catheters in three 8-week-old pigs before and at the time of appliance placement and then at 2-day intervals until the animals were 20 weeks old. Besides confirming the observations of a previous study, we noted that forward positioning of the mandible caused an increase in synovial fluid pressure that decayed to baseline levels within 2 hours. Posterior positioning of the mandible effected a larger increase in pressure that partially decayed over 2 hours but did not return to baseline levels over the entire course of the experiment. These results may have significance in the understanding of the physiology of the temporomandibular joint, local control mechanisms involved in the normal and treatment-aided growth of the mandible, and disorders of the temporomandibular joint.
The objective of this study was to determine the relationship between the anterior component of occlusal force and malalignment of the mandibular anterior teeth. The anterior component of occlusal force that resulted from axially loading the second molars was measured in 15 subjects with varying degrees of mandibular anterior dental malalignment. Malalignment of the mandibular anterior teeth was found to be related to the magnitude of the anterior component of occlusal force and to the tightness of interproximal contacts in the mandibular posterior segments.
An orthodontic uprighting technique for effective treatment of impacted third molars, exposed or unexposed, is described. When used with conventional fixed appliances, this technique presents a viable option to extraction or prediction of eruption. Several applications illustrate that, with proper intervention, this uprighting technique is simple and effective in positioning malposed third molars.
The purpose of this investigation was to design and develop instrumentation to measure the anterior component of occlusal force generated by a single tooth under a known axial load. An additional objective was to quantify the distribution and dissipation of this force as it progressed anteriorly. The anterior component of the occlusal force generated by the left second molar was calculated from frictional force measurements at each contact mesial to the first molars in both dental arches. The distribution of this force and its dissipation were determined for 15 subjects. When a load was placed on the posterior teeth, the anterior component of the occlusal force was found to progress anteriorly through interproximal contacts and not to progress beyond open contacts. The mean magnitude of this force for a conservative occlusal load of 20 pounds was unexpectedly high: 5 pounds against the premolars and 1 pound against the canines. In some subjects this force crossed the dental midline and continued around the arch to the canine of the contralateral side. The distribution and dissipation of the anterior component of the occlusal force anteriorly approximated an exponential decay function.
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Attainment of a Class I molar relationship (Angle) is often a prime treatment objective. In addition to considerations of improved function and skeletodental harmonies, a Class I relationship often is deemed the "correct" and stable situation. This study assessed the relative stability of the sagittal molar relationship in orthodontically untreated persons with full dentitions who were followed longitudinally from young (approximately 20 years) to older (approximately 55 years) adulthood. The Class I relationship is indeed most stable; none of 69 cases (sides) starting in a Class I cusp-in-groove relationship moved from that condition. In contrast, Class II relationships naturally became significantly "more" Class II (that is, greater distoclusion), and Class III cases shifted significantly to greater mesioclusion.
A seven-year-old male with localized severe periodontal destruction at the maxillary central incisior region presented for treatment. There was a history of acute trauma, but local factors were inconsistent with the clinical picture. Initial treatment consisting of palliative nonsurgical debridement coupled with systemic tetracycline resulted in a more chronic lesion with progressive bone loss. Surgical entry revealed an elastic band close to the apices of the central incisors. Removal of the etiologic agent has resulted in increased radiographic bone density and decreased probing depths. Periodontal lesions induced by elastic bands are difficult to diagnose but have several features in common that may aid in rapid diagnosis and treatment.
A method of curing light-cured composite resins by transillumination to cement acid-etched fixed partial dentures was adapted to bond solid mesh-backed lingual orthodontic brackets. Results of this investigation showed that the bond strengths of the orthodontic brackets bonded with light-cured composite resins were significantly less (P less than 0.05) than the bond strengths of the orthodontic brackets cemented with traditional adhesives and orthodontic composite resins. Notwithstanding, the bond strengths achieved with the transilluminated light-cured composite resins should be adequate to withstand the forces of mastication and orthodontic movements. There was no correlation of bond strengths of the brackets cemented with the transilluminated light-cured composite resins when compared to the faciolingual widths of the teeth.
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A statistical comparison of cross-sectional cephalometric records of Class III malocclusion subjects from ages 5-15 with serial Class I controls, finding strong tendencies for early appearance of distinctive characteristics.
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For the past twenty years it has been argued that the growth of the face is governed by the growth of a variety of contiguous soft tissues and functioning spaces (functional matrices). Recently, extensive data have been marshalled to suggest that the growth of the functional matrices is controlled by "trophic" influences from nerves. Accordingly, the present study sought to evaluate the role of the trigeminal nerve in the regulation of facial growth by placing unilateral stereotaxic lesions in the trigeminal nerve (root, ganglion, or major sensory branch) of the 10- to 20-day-old rat. The unoperated side and a number of sham animals served as controls. In all, 323 operations were performed, with 119 animals surviving until the age of 50 days. The location and extent of the lesions were controlled histologically. Cephalometric analysis revealed subtle but statistically significant distortions of the facial skeleton; however, the magnitude of the effect was quite small. Thus, although a modest case can be made for the contention that the trigeminal nerve exerts a trophic influence on the craniofacial complex, the conclusion that trophic effects constitute a major factor in the regulation of craniofacial growth cannot be supported.
Synovial fluid hydrostatic pressure within the temporomandibular joint of the pig, Sus scrofa domesticus, was examined, utilizing the "wick method" for the determination of fluid pressure. Acute hydrostatic pressure levels were monitored in seven surgically exposed TMJ capsules of five animals. In six out of seven of the surgically exposed TMJ capsules, synovial fluid hydrostatic pressure was subatmospheric with the jaw in the resting position (mean = -3.8 mm of mercury). Fluid pressure increased as a response to operator-manipulated jaw position and returned to original levels upon release. In addition, an attempt was made to study fluid pressure in TMJ cavities of a functioning experimental animal model by chronically implanting a wick catheter in the joint space. Successful implantation was accomplished in two animals, and fluid pressure was monitored at 10- and 14-day intervals. Similar but slightly less negative mean "resting values" were obtained. Fluid pressures were greatly elevated during mastication.
A method is presented wherein the attachment of linear potentiometers to the electrode carrier of a standard stereotaxic headholder permits the use of a reference voltage and an X-Y recorder to generate rapid, accurate graphic representations of various neural structures within the field of the electrode. The method is described in application to studies in rat and cat.
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