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At least 829 records · Page 46Linked to original sources
PubMed1983

The increase in vivo by electric currents of the 99mTc-methylene diphosphonate uptake and cyclic AMP content of the bone of the cat mandible.

Technetium-99-methylene diphosphonate (99mTc-MDP) bone images were obtained from live cats whose mandibles had been stimulated non-invasively and unilaterally with electric current (12 +/- 2 microA) for 1 week. The images were obtained using a gamma camera interfaced to a digital computer for quantitative comparison of the mandible. Radionuclide uptake by the stimulated sides increased by 59 +/- 26 per cent when compared with the contralateral control sites. Immunohistochemical staining of mandibular sections for adenosine 3',5'-monophosphate (cyclic AMP) showed that periosteal osteoblasts opposite the electrodes were intensely stained. Thus 99mTc-MDP scintigraphy is a sensitive non-invasive technique for determining in vivo enhanced bone remodelling activity. The immunohistochemistry indicates that the stimulation of bone cells was limited to surfaces adjacent to both cathode and anode.

Animals↗
PubMed1994

Temporal distribution of endogenous retinoids in the embryonic mouse mandible.

Retinoids play an important part in embryonic pattern formation. They are necessary for normal differentiation of odontogenic tissues and, in excess, disrupt the pattern of tooth formation. Excess retinoids produce supernumerary buds of the dental lamina in the diastema region of the mouse embryonic mandible where teeth do not normally form. This effect is coincident with an increase in epithelial proliferation and an alteration in epidermal growth factor mRNA expression (a gene product necessary for tooth formation). It was found by high-performance liquid chromatography that endogenous retinoids are present in the developing murine mandible and that concentrations of some retinoids reach a peak at the time of the initiation of odontogenesis (dental lamina formation).

Animals↗
PubMed1994

In vitro strain measurements in the condylar process of the human mandible.

Although there have been a number of experimental studies of temporomandibular joint loading, the precise relation between condylar load and condylar strain is incompletely understood. This in vitro study determined the magnitudes and directions of the principal components of strain on the four surfaces of the condylar process of human cadaver mandibles during loading with selected simulated muscle forces, with simultaneous measurement of occlusal and joint forces. Rosette strain gauges were placed on each of the four surfaces and the mandibles were loaded by a load cell to simulate the action of the masseter and medial pterygoid muscles. Force and strain values were measured at five different bite positions and nine different positions of the resultant muscle force. Forces and strain values were highest when the resultant muscle force was closest to the joint and the bite position was furthest from the joint. The ratios of bite force to joint force and the ratios of forces between the two joints conformed to theoretical predictions of many previous models, with the balancing-side joint being loaded more heavily than the working-side joint. At all gauge positions the maximum principal strain was tensile, the minimum principal strain was compressive, and the absolute strain values were correlated with the magnitude of the force on the condyle. However, under the chosen loading regimen, the ratio of compressive to tensile strain differed among the four surfaces. The highest levels of tensile strain occurred on the anterior and lateral surfaces and the highest compressive strain occurred on the posterior surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Spatial distribution of endogenous retinoids in the murine embryonic mandible.

Retinoids play an important part in pattern formation during embryonic development. Exogenous retinoids alter the pattern of skeletal, neural and odontogenic tissues. Endogenous retinoids have been demonstrated previously in the murine embryonic mandible, reaching a concentration peak during the initiation of odontogenesis. It was now found that endogenous retinoids are present in a concentration gradient in the embryonic mouse mandible at the time of the initiation of the dental lamina. All-trans-retinoic acid was more concentrated in the incisor region and retinol in the molar region. These results, and the fact that exogenous retinoids produce supernumerary incisors and missing molars, suggest that all-trans-retinoic acid may instruct incisor morphology.

Animals↗
PubMed1996

Spatial and temporal distribution of Indian hedgehog mRNA in the embryonic mouse mandible.

Hedgehog genes are involved in pattern formation during embryonic development. A recent report showed that Sonic hedgehog is expressed in the mouse mandible in the presumptive incisor region. In the present study, Indian hedgehog (Ihh) transcripts were present from gestational day 9 to 14 in the mouse mandible (reverse transcription/polymerase chain reaction analysis). Ihh mRNA was present in the dental lamina in both incisor and molar regions and in the developing whiskers (in-situ hybridization). Ihh may be involved in the site-specific proliferation of mandibular epithelium during the formation of the dental lamina. This is consistent with the observation that endogenous synthesis of retinoic acid is necessary for the initiation of odontogenesis and that retinoic acid induces hedgehog expression.

Animals↗
PubMed1987

Reconstruction of the middle third of mandible.

The radial forearm flap is established as a suitable method of providing bone with soft tissue lining or skin cover in reconstruction of the mandible. A simple and effective method of modelling the radius to provide the appropriate contour to the anterior arch of the mandible is described.

Humans↗
PubMed1988

Primary reconstruction of the mandible after excision of large benign lesions.

Small benign lesions occurring in the mandible, such as dental cysts or adamantinoma, are treated adequately by the dental surgeon using an intraoral approach and curettage (Brånemark et al., 1975). However, larger and recurrent lesions are better treated via the submandibular route (Boyne, 1969). After lesion clearance, the bone gap in the mandible needs to be bridged properly to avoid disabling functional and cosmetic results. This paper describes a modified conventional method of reconstruction which is simple and effective and gives excellent long-term results.

Adolescent↗
PubMed1977

Autogenous bone graft procedures for atrophic edentulous mandibles.

Using a joint oral surgery-prosthodontic team approach, five patients with extreme atrophy of the edentulous mandible were selected for augmentation of the mandible with autogenous bone grafts from the crest of the ilium. All were wearing restorations considered adequate, but they had difficulty tolerating the lower dentures. An extraoral submandibular surgical approach was employed with few postoperative complications. Sulcus extension procedures were unnecessary after surgery, and four of the five patients received lower prostheses in approximately 3 months. The oral surgeon, the prosthodontist, and the five patients considered the results successful.

Adult↗
PubMed1977

Biologic laws governing functions of muscles that move the mandible. Part I. Occlusal programming.

Many factors, other than the proprioceptive inputs originating from occlusal contacts of teeth, program jaw position and the functions of the muscles that move the mandible. However, once the mechanism by which specific occlusal contacts program specific muscle functions is clearly understood, it becomes a relatively simple matter to make an accurate diagnosis and select the most direct approach to treatment. This article is Part I of a series presented in four parts on the "Biologic Laws Governing Functions of Muscles That Move the Mandible."

Biology↗
PubMed1982

Determination of the physiologic equilibrium point of the mandible by electronic means.

The location of the physiologic equilibrium point of the mandible was determined by electronic means while the subjects clenched their teeth in centric relation with a force of 24 pounds. A total of 20 occlusal relationships were observed. In 14 Angle's Class I occlusal relationships, the equilibrium point, when projected at right angles to the midsagittal plane, was observed lined up within the mesial third of the mandibular first molar. In four Angle's Class II occlusal relationships, it was lined up within the distal half of the mandibular second premolar; and in two Class III Angle's occlusal relationships, it was lined up within the middle third of the mandibular first molar. When referenced to the maxillary arch, 16 occlusal relationships lined up within the mesial third of the first molar and four within the distal half of the second premolar. In the coronal plane, the equilibrium point was estimated as being in or close to the midsagittal plane. The biomechanical significance of the equilibrium point was discussed. The location of the equilibrium point was expressed mathematically using a model of the mandible as a beam on resilient supports. Further studies considering the clinical significance of the equilibrium point in relation to centric occlusion registrations and orthodontic treatment are suggested.

Adolescent↗
PubMed1984

Errors in oblique cephalometric radiographic projections of the edentulous mandible. Part I: Geometric errors.

Geometric errors that occur in oblique cephalometric radiographic projections of the edentulous mandible were calculated for different focal-spot-to-object distances (1500, 3000, and 6000 mm). The horizontal errors from tolerance of the porion and nasion fixation in the cephalostat were calculated. The same was done for the vertical errors caused by the variability of the rest position. From the results of this study it can be concluded that the distance between focal spot and object should be as large as possible. It was also found that it is important to minimize the differences in enlargement that may occur on radiograms of different subjects because of changes in the position of the mandible. This position can be standardized by the use of an individual support.

Cephalometry↗
PubMed1992

Biomechanical model of the human mandible: a hypothesis involving stabilizing activity of the superior belly of lateral pterygoid muscle.

A new biomechanical analog for the human mandible is proposed. The biomechanics of the human mandible can be explained by a simple support model, where muscular forces are produced by the masseter, medial pterygoid, temporal, and superior lateral pterygoid muscle components, and reaction forces are produced by the occlusal surfaces and condyle. All forces are resolved into components orthogonal and parallel to the temporal articular plane (articular eminence). In this model, one component of muscular forces is parallel to the temporal articular plane. The influence of the inclination of the occlusal plane, the inclination of the temporal articular plane, the position of the resultant of the occlusal reactions, and the relative contribution of the different jaw elevator muscles on the parallel and orthogonal components are evaluated according to a computer model of the system. The muscular force parallel to the temporal articular plane may be produced by the superior lateral pterygoid muscle, which during clenching acts as a stabilizer of the mandibular condyle to prevent posterior dislocation and compression of nonarticular tissues.

Biomechanical Phenomena↗
PubMed1993

Effect of bone mineral density in skeleton and mandible on extraction of teeth and clinical alveolar height.

Residual ridge resorption of the maxillae and mandible after tooth extraction adversely affects many edentulous people. The jaws of 355 postmenopausal women were examined clinically, and the number of teeth and the clinical height of alveolar ridges in edentulous jaws were determined. Each subject was asked when the last teeth had been extracted. To study the bone mineral status of each woman, the bone mineral densities of the femoral neck and the lumbar spine were measured by dual-energy x-ray absorptiometry. For 77 edentulous or almost edentulous women, the bone mineral density of the mandibular cortex and the spongiosa were measured by quantitative computed tomography. The results were studied to determine whether the general status of osteoporosis or the local bone mineral densities in the mandible affect the time of extraction of teeth or the remaining height of edentulous alveolar ridges. Neither the time when the teeth were lost nor the number of teeth was dependent on the general bone loss, but in some regions, the clinical height was affected.

Alveolar Process↗
PubMed1993

Osseointegrated implants in microvascular fibula free flap reconstructed mandibles.

In the past, prosthodontic rehabilitation of patients who underwent segmental mandibular resection relied on removable prostheses, which were less than ideal. The advent of the microvascular free flap has provided improved appearance and function through reconstruction of the skeletal integrity of the mandible. In select patients osseointegrated implants strategically placed in the reconstructed mandible can be used to restore masticatory function. Patient selection criteria and techniques are discussed.

Adolescent↗
PubMed1993

Osseointegrated implant rehabilitation of the previously irradiated mandible: results of a limited trial at 3 to 7 years.

The use of osseointegrated dental implants in patients with defects of the head and neck acquired as a result of ablative surgery for malignancy is an accepted and valuable extension of the well-documented use of these implants for the treatment of edentulism. In patients who have received ionizing radiation as part of tumor therapy, the use of dental implants is poorly documented. A limited trial of 21 Brånemark implants placed in the previously irradiated mandibles of four patients is reported here. The implants have been in place and functioning for periods of 3 to 7 years. No implants have been lost. Patient selection, treatment, and complications encountered are discussed. Guidelines for further use of osseointegrated implants in patients with previously irradiated mandibles are suggested.

Carcinoma↗
PubMed1975

Central adenocarcinoma of the mandible.

A seemingly straightforward clinical diagnosis of ameloblastoma was made of a large radiolucent, multicystic lesion in the mandible. Biopsy and metastatic tumor work-up revealed the tumor to be primary in the mandible. A histopathologic diagnosis of papillary adenocarcinoma of salivary gland origin was made. This article reports a well-documented primary mandibular salivary gland tumor. A review of the literature and light and electron microscopic interpretation of this tumor are presented.

Adenocarcinoma, Papillary↗
PubMed1980

The relationship between dental disease and radiation necrosis of the mandible.

Preirradiation panoramic radiographs of forty-six dentate patients were examined for the presence of significant dental disease. The occurrence of necrosis of the mandible after these patients received radiation therapy was then determined. Evidence of a positive association between dental disease present before radiation therapy and subsequent necrosis of the mandible was found (p = 0.09), leading to a recommendation that significant disease be eradicated before irradiation of oral tissues. Two cases are reported to illustrate the complications that can arise in dentate patients following radiation to the oral cavity. Considerable suffering results from bone necrosis, which can be reduced by careful and rational dental diagnosis and treatment.

Carcinoma, Squamous Cell↗