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Biomedical subjects

R G Behrents

Publications and source records attributed to R G Behrents.

At least 19 recordsLinked to original sources
PubMed2000

Vertical components of overbite change: a mathematical model.

The purpose of this study was to better understand the multidimensional nature of overbite changes that occur during adolescence. The study used longitudinal cephalograms of 181 untreated children (102 males, 79 females) taken at ages 10 and 15. Four major components that directly affect overbite were measured: (1) maxillary vertical displacement, (2) mandibular vertical displacement, (3) upper incisor vertical change within the bone, (4) lower incisor vertical change within the bone. Cranial base, maxillary, and mandibular superimpositions were performed for each subject to assess the vertical changes that occurred in these 4 components and to assess overbite. A multiple regression analysis was used to develop a mathematical model describing the relationships of these components to changes in overbite. The model was validated with an independent subsample and a comparison of subjects whose overbites decreased and those whose overbites increased. The results showed that overbite changed minimally (0.2 mm) over the 5-year period; variation ranged from a 2.4 mm decrease to a 5.6 mm increase. The regression model indicated that the mandibular skeletal changes were twice as important as the mandibular dental changes and about 2.5 times as important as the maxillary changes in effecting overbite change. Within the mandibular skeletal component, vertical growth was more important than mandibular rotation in determining overbite change. The model demonstrated that a multivariate approach is necessary to understand overbite changes. More effective orthodontic treatment might be achieved by focusing on the primary components effecting overbite change, especially those with the greatest potential for therapeutic modification.

Adolescent↗
PubMed1996

The effect of orthodontic treatment on centric discrepancy.

The purpose of this study is to investigate the effects of orthodontic treatment on centric discrepancy. Thirty-six orthodontic patients who had been treated with an edgewise appliance were selected for this study while 30 persons who had no history of orthodontic treatment were used as a control group. After recording centric relation using a leaf gauge, centric prematurity, and centric slide were compared using a SAM2 articulator and mandibular position indicator. Results indicated that the number of subjects with one prematurity was significantly greater in the control group (86.7%); however, the number of subjects with two or more prematurities was greater in the orthodontic treatment group (41.6%). The orthodontic treatment group showed more bilateral prematurities. There were no differences between the two groups with regard to the teeth involved in centric prematurities. Just considering the anatomic portion of teeth, centric prematurities were significantly associated with the buccal incline of the maxillary palatal cusp. There were no significant differences in the amount or direction of centric slide between the orthodontic and control groups. This study indicates that orthodontic treatment does not generally result in an increase in centric discrepancy.

Adult↗
PubMed1995

Adult versus adolescent Class II correction: a comparison.

The interest of the adult patient in orthodontics has increased as the demographics of the specialty of orthodontics has changed. There are major intreatment and posttreatment differences in Class II malocclusion correction between the adolescent and the adult. This article outlines the differences--and the similarities--between adolescent and adult Class II malocclusion correction. The differences and similarities are illustrated with case reports of a representative adolescent from the adolescent group and a representative adult from the adult group.

Adolescent↗
PubMed1994

Effects of patient age on postorthodontic stability in Class II, division 1 malocclusions.

The increase in the proportion of adults in the typical orthodontic practice merits closer scrutiny of the treatment differences involved in adult vis-à-vis adolescent patients. Orthodontic treatment in the adolescent relies heavily on growth; in the adult, the practitioner must reposition teeth within the nongrowing arches. This difference may create the potential for greater postretention relapse in the adult; alternatively, continued growth in the subadult might detract from stability of the case. Two samples of Class II, Division 1 cases, all treated by one specialist, were examined an average of 5 years out of treatment. One group had been treated during adolescence (approximately 12 years of age), the other in adulthood (approximately 28 years). The orthodontic corrections were stable in both groups, but for different reasons: Posttreatment changes in the bony and dental structures of the adults were minimal. Bony changes (i.e., continued midface and mandibular growth) were appreciable in adolescents, and this growth--notably growth of the mandible--compensated for unfavorable drift of the dental elements (primarily mesial shift of the maxillary molar) after treatment. In sum, orthodontic corrections in adults were found to be at least as stable as those in the conventional adolescent patient.

Adolescent↗
PubMed1993

Sexual dimorphism in normal craniofacial growth.

The purpose of this investigation is to re-evaluate an existing sample of Caucasian individuals, of mostly Northern European ancestry and undefined ethnic origins, who have been characterized as having excellent occlusions and balanced facial proportions (from a subjective assessment). The focus is the emergence of sexual dimorphism in the skeletal and dental relationships. Serial lateral cephalograms of 51 subjects were obtained from the Bolton-Brush Study at ages 6, 9, 12, 14, 16 and 18 yrs. At each age, the records of 16 males and 16 females were selected. Cephalometric evaluation indicated that the length of the anterior cranial base was larger in males but the cranial base angle was similar for both sexes at all age intervals studied. The effective lengths of the maxilla and mandible were similar in both sexes up to 14 years; thereafter in females this length remained relatively constant while in males it increased. The direction of facial growth was similar for both sexes, with a tendency towards a more horizontal growth pattern in females.

Adolescent↗
PubMed1992

Metacarpophalangeal length changes in humans during adulthood: a longitudinal study.

Total lengths of the 19 diaphyseal hand bones were measured from standardized radiographs of healthy American whites as young adults (ca. 21 years) and again at ca. 55 years of age. The four hand-bone rows exhibit distinctive length changes: Distal and middle phalanges continue to increase significantly in length, proximal phalanges constitute a transition zone of little change, and metacarpals uniformly decrease in length. Clear-cut sex differences are noteworthy: Males change more (lose more in some bone rows, gain more in others) than females. Progressive elongation was greatest in the distal phalanges where apposition around the distal aspect ("tufting") is not constrained by a joint or epiphysis. Loss of bone length in the metacarpals by subchondral resorption is consistent with documented reductions in activity levels and grip strength with age, as well as diminished joint spaces which alter loading of the joints.

Adult↗
PubMed1992

An example of regional variation in the tempos of tooth mineralization and hand-wrist ossification.

Two groups of adolescent orthodontic patients, one from the Midwest and one from the Midsouth, were compared to test the clinical impression that the permanent teeth of southern children form and erupt at significantly later ages. Indeed, a marked difference is documented, with the Midsouth series achieving mineralization stages at least 1 1/2 years later on average. This suggests that regional differences are appreciably greater than previously suspected. Clinical consequences revolve on the use of conventional (generally Northeast-based) norms for tooth formation and eruption and predictive models of facial growth. In contrast, the analysis of rates of hand-wrist development (bone age) of these same subjects disclosed no difference; this further confirms the essential independence of development of the dental and osseous tissue systems.

Adolescent↗
PubMed1991

The premaxillary-maxillary suture and orthodontic mechanotherapy.

Even though there has been debate over whether a separate premaxilla exists in the human being, it has been suggested that the premaxillary-maxillary suture remains patent into adolescence and provides an explanation for the action of certain orthodontic and orthopedic appliances. To assess whether this suture is pertinent to an understanding of appliance effects, the skulls of 50 subadult subjects were scrutinized to determine patency with regard to age. Remnants of a premaxillary-maxillary suture may be present on the surface of the palate at all ages studied, and often this suture extends deep to the surface. However, in no case was the suture continuous so as to distinguish a distinct premaxilla. These findings disprove the claim that the premaxillary-maxillary suture system provides an explanation for any form of orthodontic or orthopedic therapy.

Adolescent↗
PubMed1991

Education, research, and personnel needs in orthodontics.

Because of changing patterns of dental care delivery, the nature of orthodontic education, research, and personnel needs has changed markedly in recent times. Changes have occurred in the university environment, dental education, and undergraduate and graduate orthodontic education. Orthodontic research is shifting to more clinically oriented topics. Orthodontic personnel needs are being addressed by changing levels of specialist and general practitioner involvement.

Education, Dental, Graduate↗
PubMed1991

Extraction versus periodontal-orthodontic treatment: a case report.

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.

Adult↗
PubMed1990

Temporomandibular synovial fluid pressure response to altered mandibular positions.

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.

Animals↗
PubMed1990

The anterior component of occlusal force. Part 2. Relationship with dental malalignment.

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.

Adult↗