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Biomedical subjects

W H Bell

Publications and source records attributed to W H Bell.

At least 109 records · Page 6Linked to original sources
PubMed1980

Cephalometric analysis of dentofacial normals.

A comprehensive cephalometric analysis of "normal" adults was accomplished by examining a carefully selected subject group. Fifty-six adult Caucasians with Class I skeletal and dental relationships and good vertical facial proportions were analyzed morphologically with a computerized craniofacial model. By the incorporation of a large number of soft-tissue measurements, facial profile and proportionality were analyzed and compared with methods that are presently used to evaluate facial esthetics. The data provide relevant measurements that are useful in the diagnosis and treatment of adults with dentofacial deformities. Horizontal soft-tissue chin prominence was nearly equal for males and females relative to subnasale, soft-tissue nasion, and glabella.

Adult↗
PubMed1980

Control of the transverse dimension with surgery and orthodontics.

Control of the transverse dimension through surgical techniques now available for use by the orthodontist is a valuable treatment consideration for orthodontic therapy in the nongrowing patient. In this article, proper diagnosis of relative and absolute transverse maxillary deficiency or excess is stressed as being imperative prior to completion of definitive orthodontic and/or surgical treatment planning. Therapeutic alternatives designed to facilitate correction of transverse discrepancies concomitant with treatment objectives in the sagittal and vertical dimensions are discussed and illustrated with case reports.

Adult↗
PubMed1980

Biomechanics of differences in lower facial height.

A two-dimensional model which allows calculation of mechanical advantage of the human temporalis and masseter muscles is presented. The model is manipulated to demonstrate how selected differences in facial morphology affect the mechanical advantage of the muscles. The model is then used to evaluate the differences in mechanical advantage between patients with the long face syndrome and those with the short face syndrome. Differences in facial morphology between these two groups result in significant differences in the mechanical advantages of their muscles. Mechanical advantage may, in part, explain observed differences in bite force between the two groups. The model suggests that some surgical procedures used to correct facial disharmonies may have a significant effect on the mechanical advantage of the jaw muscles.

Adolescent↗
PubMed1980

Surgical-orthodontic correction of maxillary retrusion by Le Fort I osteotomy and proplast.

The combined efforts of the orthodontist and surgeon are necessary for successful treatment of most patients with maxillary retrusion. Both the aesthetic and functional manifestations of this dento-facial deformity can usually be effectively treated by maxillary advancement, augmentation of the midfacial region and orthodontics. Treatment planning, pre- and post-surgical orthodontic treatment principles, and surgical considerations in treating 25 adults with maxillary retrusion are described and illustrated. Surgical advancement of the maxilla by Le Fort I osteotomy, proper alignment of the teeth by orthodontics, and augmentation of the paranasal, canine fossae and malar regions with Proplast, were the common denominators of successful treatment.

Adolescent↗
PubMed1980

Biomechanical considerations in the surgical correction of mandibular deficiency.

A two-dimensional model is presented that allows calculation of mechanical advantage for the human masseter and temporalis muscles. Ten patients with high-angle mandibular deficiency and vertical maxillary excess had greatly reduced mechanical advantages with an anticipated elevated muscle activity. Superior repositioning of the maxilla with mandibular advancement, however, increased the overall mechanical efficiency of the masticatory system. When compared with mandibular advancement alone, the bimaxillary procedure resulted in a 13% increase in the mechanical advantage of the temporalis muscle and a 21% increase for the masseter muscle. This model suggests that various surgical procedures designed to correct facial disharmonies may have either desirable or undesirable effects on jaw biomechanics and long-term stability. Biomechanical influences are important considerations for the clinician in planning surgical procedures to correct dentofacial deformities.

Biomechanical Phenomena↗
PubMed1979

Combined orthodontic-surgical correction of moderate mandibular deficiency.

Carefully planned, coordinated, and executed orthodontic and surgical treatment is a viable alternative to traditional orthodontic treatment of patients with moderate mandibular deficiency. Recognition of their clinical manifestations is essential to distinguish between relative and absolute mandibular deficiency. If after clinical analysis of the Class II patient, esthetic priorities are established to maintain a balanced relationship between the upper lip and nose and not reduce the prominence of the upper lip, mandibular deficiency must be treated by surgical advancement of the mandible, superior repositioning of the maxilla, and consequent autorotational movement of the mandible forward and upward, or a combination of these procedures. The common denominator of successful therapy of absolute mandibular deficiency involves surgery to advance the mandible; relative mandibular deficiency, on the other hand, is treated by maxillary surgery to reposition the maxilla superiorly to allow forward and upward movement of the retropositioned mandible (autorotation). In actual clinical practice many patients manifest a combination of absolute and relative mandibular deficiency and are treated by maxillary and mandibular surgery. Lateral maxillary osteotomies, in concert with rapid maxillary expansion and genioplasty to alter the dimensions of the chin, are essential adjunctive surgical procedures to achieve three-dimensional esthetic and occlusal balance.

Adult↗
PubMed1979

Surgical-orthodontic correction of horizontal maxillary deficiency.

Selected maxillary osteotomies in concert with rapid maxillary expansion appliances are dependable adjuncts to treatment of the various clinical manifestations of horizontal maxillary deficiency and the accompanying crossbite. The important diagnostic, treatment planning, and technical considerations necessary for successful surgical-orthodontic correction of horizontal maxillary deficiency were discussed.

Adult↗
PubMed1978

Comparative study between the SFS and LFS rotation as a possible morphogenic mechanism.

Cephalometric tracings of twenty-seven untreated adult Caucasians, selected on a clinical impression of reduced lower facial height were studied and compared with tracings of nine untreated adult Caucasians with increased lower facial height. Various linear and angular measurements for both groups were analyzed and compared. As has been previously described for the SFS, the LFS group can be subdivided into at least two subtypes. Subtype I is characterized by a long ramus, increased OP-PP, an increased SN:MP-angle, and excessive lower anterior facial height. These persons manifest the most typical clinical characteristics of the long face syndrome and have excessively long faces. In Subtype II, however, extreme backward and downward rotation of the mandible, combined with a short or extremely short ramus, is associated with an increase in lower anterior facial height. The increase in posterior maxillary height was not striking in this subtype. It was demonstrated that many of the characteristics of the LFS group and the SFS group can be explained by clockwise or counterclockwise rotation of the mandible "in concert" with the hyoid, tongue, pharynx, and cervical spine. The LFS group was characterized by a clockwise rotation of the mandible "in concert" with the hyoid, tongue, pharynx, and cervical spine. The mandible of the SFS group rotated similarly, but in the opposite counterclockwise direction. The vital need to maintain patency of the upper airway at the level of the base of the tongue may account for rotation in the LFS.

Cephalometry↗
PubMed1978

The short face syndrome.

Cephalograms of twenty-seven untreated adult Caucasians, selected on the basis of a clinical impression of reduced lower facial height, were studied. Various linear and angular measurements were studied and compared to the Bolton standards. The short face syndrome SFS is a clinically recognizable facial type with reduced lower facial height as the common denominator. On the basis of the FPI (facial proportion index), the RH (ramus height), the OP-PP distance (or posterior maxillary height), and the SN:MP angle, two subgroups were distinguished in the SFS group. SFS, was characterized by a long ramus, sharply reduced SN:MP angle, an FPI close to 10, and a slightly reduced posterior maxillary height. In contrast, SFS2 was characterized by a short ramus, a slightly reduced SN:MP angle, an FPI with values around or below zero, and a sharply reduced posterior maxillary height. The latter group was designated as vertical maxillary deficiency.

Adolescent↗
PubMed1978

Revascularization after surgical repositioning of one-tooth dento-osseous segments.

Vascularization, revascularization, and bone healing were studied after two different surgical techniques for surgical repositioning of single-tooth dento-osseous segments in adult mongrel dogs. Microangiographic and histologic studies of both one-stage and two-stage techniques for immediate surgical repositioning of single-tooth dento-osseous segments showed early but transient vascular ischemia, minimal osteonecrosis, and osseous union between most of the osteotomized segments. The attached soft tissue provided an adequate vascular pedicle for immediate repositioning of small dento-osseous segments by interdental and subapical osteotomies. The results of these clinically analogues studies support the clinical use of techniques that maximize the attachment of the gingiva to the mobilized dento-osseous segment.

Alveolar Process↗
PubMed1978

Correction of the atrophic alveolar ridge by interpositional bone grafting: a progress report.

A retrospective study of postoperative stability and osseous changes was made on nine patients with maxillary or mandibular atrophy who were treated with interpositional bone grafting techniques. There was minimal discernible positional change or resorption of the portion of the maxilla or mandible that was moved by interpositional grafting procedures. Sequential radiographs and cephalometric tracings showed early consolidation of the grafted bone, minimal resorption of the respositioned osseous segments, and a small decrease of alveolar ridge height during an average potsoperative follow-up period of seven months.

Alveoloplasty↗
PubMed1977

Surgical correction of the long face syndrome.

The combined efforts of different specialists are needed for the successful treatment of patients with the long face syndrome. Both surgeons and orthodontists who recognize their own capabilities and limitations must combine their skills to achieve the best possible occlusion and facial esthetics. The surgical and orthodontic plan of therapy is designed to correct the patient's dentofacial deformity. Surgical reduction of facial height and proper alignment of the teeth by orthodontic means are common denominators of successful treatment. By properly planned and executed Le Fort I maxillary osteotomies, the vertical dimensions of the face can be shortened to improve the esthetic balance between the nose, upper lip, teeth, and chin and achieve lip competency. Variable open-bite and nonopen-bite maxillary deformities in forty adults with the long face syndrome were corrected by Le Fort I osteotomy and orthodontic treatment. The technical problems encountered in planning and executing treatment are discussed and illustrated by selected case reports.

Adolescent↗