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At least 397 records · Page 22Linked to original sources
PubMed2006

[Establishment of a three-dimensional finite element model of mandible with dental implants for immediate loading].

PURPOSE: To establish a three-dimensional finite element model of mandible with dental implants for immediate loading, which will provide a basis for study of the biomechanical characteristics of the immediate loading implant-bone interface. METHODS: A female edentulous mandible was adopted for CT scanning, the scanned data were saved with the form of DICOM, and then input into compute. Universal Surgical Integration System which was developed by ourselves and ANSYS 10.0 were used to divide mesh and establish finite element model. Three dental implants simulating the real shape of ITI thread implant were embedded in the anterior region of the mandible, of which implant-bone interface was granted with situation of smooth friction simulating the case of immediate loading. RESULTS: The accurate finite element model of mandible with dental implants for immediate loading was established, which included 127811 tetrahedron elements with 182252 nodes. A single dental implant model comprised 13924 elements with 21420 nodes, the thread of it was continuous and smooth. CONCLUSION: The biomechanical similarity, the geometrical analogy and clinical indication of the model were quite good. The three-dimensional finite element model developed by this method can apply for precise analysis of the rule of biomechanics on the implant-bone interface for immediate loading.

Dental Implants↗
PubMed1991

[Study on the bias axis stress-strain relationship of the human mandible].

This paper presents our study on the bias axis elastic properties of the human mandible. The elastic coefficients were determined by the composite materials mechanical testing methods. From these values the "technical constants" were calculated to be: EL = 18.823GPa, ET = 12.777GPa, GLT = 5.564GPa, vLT = 0.302, vTL = 0.205. Variation of elastic constants of the human mandible with the orientation to its long axis was investigated. A brief description of the variation law is given. The bias axis stress-strain relationship of the human mandible is established. The data indicate that the human mandible is a living, anisotropic and nonhomogeneous composite biomaterial. Its mechanical properties have a close relation to its location, orientation and structure.

Adult↗
PubMed1991

A review of the intraosseous course of the nerves of the mandible.

A review of the literature revealed that a common feature of all human mandibles is a large nerve (inferior alveolar nerve, IAN) between the mandibular and mental foramina. This nerve sends branches directly to the teeth or contributes a variable number of branches to a plexus of nerves which does the same. The plexus originates from a separate nerve that enters the mandibular foramen. The nerve plexus has been demonstrated by dissections and not by radiology. The buccal-lingual and superior-inferior positions of the IAN were not consistent among mandibles. The intramandibular IAN frequently ran a concave curve with a posterior segment descending as it progressed anteriorly and an anterior segment that ascended to the mental foramen. A bony canal was not always observed between the mandibular and mental foramina. The canal frequently lacked definite walls, especially near the mental foramen. Bilateral symmetry (location of the canal in each half of the mandible) was common, whereas duplications of the canal were rare. Nutrient canals and other branches of the mandibular nerve have been observed within the mandible. These may have been confused for the IAN or may contribute to the plexus of nerves.

Humans↗
PubMed1990

[The role of the condyle in the growth of the mandible and in facial balance].

The condyle is not responsible for the growth of the body of the mandible, as the latter does not extend in length caudally at the expense of the ascending rami (through the classical relocation phenomenon), but does so deep to these, at the level of the lower insertions of the sphenomandibular ligaments (i.e., from the inlet inner border of the inferior dental canals). Philogenetically and ontogenetically, its appearance reflects the adaptation of the mandible of mammals to the morphologic and functional changes that took place in their cephalic skeleton (more erect posture, more vigorous mastication). Its chief role in man is to stabilize the mandibular body and to allow it to be properly mobilized, although contributing also to its forward and downward movements (namely in its posterior aspect). As such, it plays an active role in mandibular growth, and this role varies according to the primary "potential" of the condylar cartilage. Such primary-type potential for condylar growth may be adequately assessed by studying the shape of the mandible, as well as through an analysis of craniofacial architecture. Most of the conventional diagrams depicting mandibular growth are defective. Another figurative system has to be innovated, that will differentiate each skeletal unit--body, condyle, coronoid process, angle, alveolodental arch--, the sum of which confers the shape, the size, and the multiple variations to the mandible as a whole.

Animals↗
PubMed1989

The functional significance of morphological variation of the human mandible and masticatory muscles.

A review is given of what is known about the functional significance of variation of the morphology of the human mandible and jaw muscles. First, the mandible is a lever transferring muscular forces to the teeth. The angle between corpus and ramus and the width of the ramus are particularly relevant in this respect as they determine the mechanical advantage of the lever system and the capacity for sagittal (open-close) movement. The stability of the mandible in asymmetric bites is especially affected by the ratio between the intermolar and intercondylar distances. The repertoire of bite forces that can be generated at any tooth and the loading pattern of the temporomandibular joint are strongly dependent on the relative size of the masseter, temporalis and medial pterygoid muscles. Second, executing its function as a lever, the mandible is subjected to shearing, bending and torsional forces. The bony parts harbouring the teeth, joints and muscle attachments serve to counter these forces; additional strength is needed in three areas i.e. in the symphysis, the condylar neck and in the transition area between corpus and ramus. In human populations there are clear-cut patterns of correlation between some facial skeletal traits, jaw joint morphology and strength and line of action of the jaw muscles. As a result, facial morphologies can be distinguished with marked differences in mechanical performance of their masticatory apparatus. It is suggested that they emerge as a result of diverging environmental influences during postnatal growth.

Humans↗
PubMed1978

[The arterial blood supply of the human mandible].

The arteries of 22 mandibles injected with Kallocryl M were examined. The first group consisted of mandibles with the full complement of teeth. At the inner side, there were numerous anastomoses between the submental artery, the sublingual artery, the ascending palatine artery and the mylohyoid ramus. Furthermore, the dental rami branched into the periost. At the outside, the mental artery as well as the submental and inferior labial arteries contributed to the arterial supply. In the second group of mandibles (with intact incisors), these war a marked reduction of the anastomoses of the inferior alveolar artery in the middle region. The third group of mandibles (which were edentulous) showed anastomoses of the submental and sublingual arteries in the region of the incisors. The outside was supplied by the submental and inferior labial arteries. The mental artery exislar artery was demonstrated in 4 cases. The reduction of anastomoses concerned the inferior alveolar artery.

Aging↗
PubMed1989

The shape of the mandible in the domestic sheep: a biomechanical analysis using EMG as an estimator of muscle force.

Analysis of the maximal loads to which a skeletal element is subjected in vivo offers attractive possibilities of explaining the shape of the element. The underlying assumption is that the element will be constructed in such a way that deformations (strains) which result from mechanical stress will not exceed certain limits and that stresses will be evenly distributed. The sheep mandible shows a number of characteristic morphological features that invite this kind of explanation. We investigated the patterns of activity of the masticatory musculature by multichannel electromyography, expressing the activity of any particular muscle during a given interval as a percentage of the highest activity recorded for the muscle in question. In combination with data on the physiological cross sections of the muscles, which provide indications of the maximal forces which can be exerted by the muscles, three-dimensional patterns of relative muscular forces acting on the mandible can be constructed for successive stages of a masticatory cycle. No absolute forces can be measured or even estimated by this technique. A two-dimensional finite element model of the mandible was designed, by means of which predictions of stress and strain resulting from the muscular loading can be made. Calculations were based on the highest loads that occurred, during the power stroke of rumination. It is concluded that mechanical loading of the mandible provides a partial explanation of the form, and that a more satisfactory model should include other than purely mechanical influences.

Animals↗
PubMed1988

[Mandible magnitude in Crouzon syndrome].

The authors describe Crouzon syndrome in 5 patients aged 9, 10, 13, 40 and 43 years. Typical image of Crouzon syndrome has been found in the woman and three children and its abortive form--in the man. The authors present their own studies on branch height, length of the body of the mandible and the angle value of the mandible according to the Costaras-Volarich and Pruzancky method in their paper. The ratio of the branch to the body is 1:1 in all patients under examination and it is not equal to the normal ratio of 2:3. The angle of the mandible is also greater than the normal value. The authors put forward a hypothesis that pseudomesioclusion in the sick with Crouzon syndrome can be conditioned not only by maxilla dysplasia but also by excessive height of the branch and increased angle value of the mandible basing on their own observations. This hypothesis, however, exact further radiocephalometric studies and close cooperation of obstetricians, paediatricians and orthodontists.

Adolescent↗
PubMed1986

Stability of the mandible after sagittal ramus osteotomy for correction of prognathism.

The change in the position of the mandible after sagittal ramus osteotomy was evaluated on lateral cephalograms and in dental casts in 44 patients with mandibular prognathism. The postoperative relapse of the mandible at four landmarks was less than 1 mm on cephalograms and 1.1 mm at the first molar on the side with the larger posterior movement. The tendency to relapse was greater in cases in which large posterior and/or lateral movements of the mandible occurred at surgery. The importance of proper postoperative care and avoidance of lateral shift of the mandible to minimize relapse is stressed.

Adolescent↗
PubMed1997

The in vivo and in vitro effects of bone morphogenetic protein-2 on the development of the chick mandible.

During embryonic development, neural crest derived mesenchymal (ectomesenchymal) cells in the chick mandible give rise to cartilage and membrane bone. Signaling molecules involved in the development of the mandible are less understood. To examine whether BMP-2 is involved in morphogenesis and growth of the mandible in vivo, agarose beads, loaded with BMP-2 at concentrations of 5 to 150 ng/microliter were implanted into the mandible at HH stage 22 and embryos were maintained in shell-less culture. To examine whether BMP-2 is involved in osteogenic or chondrogenic differentiation, mandibular ectomesenchyme from HH stage 22 embryos was cultured in the absence of mandibular epithelium, but in the presence of BMP-2 or BMP-2 and/or type IV collagen. Chondrogenesis and osteogenesis were examined by histological, histochemical and immunohistochemical methods. Implantation of BMP-2-containing beads in vivo retarded mandibular growth and morphogenesis in a dose-dependent manner. BMP-2 induced localized death of ectomesenchymal cells in the vicinity of the implanted bead and in proportion to the concentration of BMP-2 applied. Neither BMP-2 alone, nor BMP-2+collagen type IV, was sufficient to initiate osteogenesis in vitro in the absence of epithelium. BMP-2 inhibited chondrogenesis both in vivo and in vitro. Cartilage morphology was rod-like in the absence of BMP-2 but nodular in ectomesenchyme cultured in the presence of BMP-2. These results are discussed in relation to the stimulatory and inhibitory effects of BMPs on skeletal development.

Animals↗
PubMed1996

Properties of the elastic modulus from buccal compact bone of human mandible.

The aim of this study was to elucidate the elastic modulus of the mandible, which is an important factor in analysis of its physical dynamics. To meet this need, three point bending tests of small bone specimens were performed. The authors concluded that the elastic modulus of the mandible varied with site and orientation. When the specimens were obtained from regions paralleling the mandibular plane, the values in the lower portions were generally higher than those in the upper portions, indicating that these regions are more rigid. The elastic modulus in the marginal portions of the mandible, such as the mandibular plane, had comparatively high values. Relatively lower values were found as the angle to the margin of the mandible increased. In the incisal and premolar regions, anisotropic characteristics approximated those of unidirectional fiber reinforced composite materials. In the molar regions, there was a broad distribution of values, reflecting the complexity of mandibular structure.

Anisotropy↗
PubMedDate not supplied

Endoscopically assisted repair of subcondylar fractures of the mandible: an evolving technique.

OBJECTIVE: To review one surgeon's experience with the endoscopic approach to assist with reduction and rigid fixation of subcondylar fractures of the mandible. DESIGN: Chart review of all cases in which endoscopic techniques were used to assist with the reduction and, when possible, repair of these fractures. The numbers of fractures approached, successfully repaired with the use of plates and screws, and not successfully plated with this approach were documented. SETTING: All surgeries were performed in the operating room at a university hospital. PATIENTS: All patients who underwent endoscopic exploration of a single or bilateral subcondylar fractures of the mandible were included. Seventeen explorations were carried out in 12 patients (age range, 16-39 years). Associated mandibular and other facial fractures were noted. INTERVENTIONS: Endoscopic exploration via a transoral approach. A secondary port in the submandibular region was made in 13 of 17 fracture explorations, and this second port was used primarily for the application of downward traction on the angle of the mandible. Plates were introduced transorally, while screws were placed through a transbuccal trochar. MAIN OUTCOME MEASURE: Success was judged by the successful reduction of the fracture and application of a rigid fixation plate by means of the limited, endoscopically assisted approach, a measure of the ability to accomplish the procedure, not an evaluation of functional results. (With these criteria, 9 of 10 successes had normal function at last follow-up, as did the 10th after revision.) RESULTS: Rigid plate fixation was completed endoscopically for 10 fractures, and 2 were plated after conversion to a full open approach. Four were reduced but could not be plated, and in 1 exploration, a bent plate was removed, but a new plate was not applied. Nine of the 10 fractures plated endoscopically resulted in normal occlusion and function. In the 10th case, a persistent malocclusion necessitated reexploration and refixation, resulting in a successful functional outcome with normal occlusion. CONCLUSION: The endoscopically assisted approach for the repair of subcondylar fractures of the mandible is a feasible but challenging technique.

Adolescent↗
PubMed2006

Single osteotomized iliac crest free flap in anterior mandible reconstruction.

While the iliac crest flap provides a natural contour for the lateral segment of the mandible, for the anterior segment en bloc, the use of the iliac graft, even harvested in a V shape, fails to yield a three-dimensional natural-shaped reconstruction. In this report, we present our experience with reconstruction of the anterior segment of the mandible using a single osteotomized free iliac crest flap in 5 patients. The study comprised 4 male patients and 1 female patient, their ages ranging between 34-82 years. In all patients, composite iliac osteomusculocutaneous flaps were harvested based on the deep circumflex iliac artery in the standard manner, and the bony segment of the flap was divided into two segments, performing a single osteotomy. The fixation of bone segments was performed in new positions, sliding the segments in different planes to provide the original shape of the resected mandible segment, and in a manner appropriate to the defect. The overall flap success rate was 100%. In no cases were wound infections or hematomas observed. X-rays showed bone healing without resorption. In conclusion, the use of a single osteotomy for an iliac crest flap in the reconstruction of the anterior segment of the mandible is a simple and safe procedure, and provides a natural and acceptable jaw appearance. The risk of devascularization is quite low when compared with the multiple osteotomy procedure, and it does not need to be fixed with complex devices such as reconstruction plates or external fixators.

Adult↗
PubMed1985

Study of the deformations of the isolated mandible under static constraints by simulation on a physicomathematical model.

The authors have studied the deformations of a mandible isolated from its muscular environment and submitted to statical constraints, with the help of a "modified model" and the finite elements method: the general deformation of the mandible and its modifications according to the direction of the application of the pressure, the rotation phenomenon or "torsion" in cross sections (identified by computer) of the mandible, the respective deformations of the internal and external corticals have successively been calculated. Particular mechanical phenomenons corresponding to the areas where the anatomo-clinical forms of the mandibular fractures take place have clearly been shown. The authors draw the conclusion that the mandible behaves mechanically in a similar way to a tridimensional composite.

Humans↗
PubMed1990

Relative efficiencies of various wiring configurations commonly used in open reductions of fractures of the angle of the mandible.

Many fractures of the angle of the mandible require direct intraosseous fixation in addition to intermaxillary fixation. In the past, various configurations of intraosseous wiring were used both at the lower and upper borders of the mandible. This study investigated which of four configurations offers the greatest mechanical resistance to a typical displacing force. Twelve baboon mandibles were cleared of all soft tissues and sectioned in the midline, and the most distal erupted molar tooth was extracted. Jigs were constructed to ensure that each mandible was sectioned in a standard fashion and that holes for wiring were drilled at a standard distance from the cut line. Mandibular halves, wired under standard conditions, were placed in an Instron tensile testing machine and subjected to a constant force that simulated the action of the major elevator muscles. Graphic recordings of force versus displacement were made. The results were subjected to an analysis of covariance, and to Scheffe's test for multiple comparisons. Results indicate that under experimental conditions, without jagged fracture surfaces, upper border mandibular wiring is less efficient than lower border wiring. At the lower border, a figure-of-eight wire is more effective than a combination figure-of-eight and straight wire, and at the upper border, the figure-of-eight wire is more effective than the straight wire.

Animals↗
PubMed1994

Hyperbaric oxygen treatment of osteoradionecrosis of the mandible with repeated pathologic fracture. Report of a case.

Treatment of patients with osteoradionecrosis of the mandible with a pathologic fracture consists in almost all cases of a continuity resection of the mandible. This leads to functional and esthetic problems that can only be solved by often extensive surgery. In this case report we present a 38-year-old woman who developed osteoradionecrosis of the mandible with a pathologic fracture 1 1/2 years after combined surgical and radiation therapy of an adenocarcinoma of the right parotid gland. The patient had a subcondylar pathologic fracture together with osteolysis in the right mandibular body, normally an indication for partial resection of the mandible. Because of the absence of denuded bone, fistulation, and the poor quality of the surrounding soft tissues, a more conservative approach was chosen. Treatment consisted of hyperbaric oxygen and dental extractions with alveolectomy with the patient under local anesthesia. During follow-up, a second pathologic fracture occurred in the region of the right first and second molar. No additional treatment was given. Six and one-half years after the initial treatment and 5 1/2 years after the last fracture, the patient is free of complaints, the fractures have healed and both esthetic and functional results are good.

Adenocarcinoma↗
PubMedDate not supplied

Mandible fracture patterns: a suburban trauma center experience.

PURPOSE: Mandible fractures are among the most frequently seen injuries in the trauma center setting. Recent shifts in the mechanism and age distribution of patients sustaining these injuries are well documented. This study attempts to define current, predictable patterns of fracture based on patient characteristics and mechanism of injury. MATERIAL AND METHODS: The charts of 134 patients with 225 mandible fractures treated over a 7-year period by the Otolaryngology-Head and Neck Surgery, Plastic and Reconstructive Surgery and Oral-Maxillofacial Surgery services, our institution, were retrospectively reviewed. Patients were categorized based on age, mechanism of fracture, and anatomic location of fracture. Multivariate analysis of data was performed to determine significant relationships among groups. RESULTS: Violent crimes such as assault and gunshot wounds accounted for the majority of fractures (50%) in this study, with motor vehicle accidents less likely (29%). Overall, parasymphyseal fractures were most frequent (35%), whereas angle and body fractures were also common (15% and 21%, respectively). There was a statistically significant association of motor vehicle accidents with parasymphyseal fractures (45%), and gunshot wounds with body fractures (36%), whereas assault victims had a higher than predicted frequency of angle fractures (27%) and fewer parasymphyseal fractures (19%). Patients aged 17 to 30 were more likely to suffer from gunshot wounds, whereas older adults (age 31-50) were more likely to be assault victims. Patients over age 50 suffered fractures from falls at a higher than expected rate. Although children and young adults seemed to suffer more parasymphyseal fractures and older adults body fractures, these correlations failed to show statistical significance. Parasymphyseal fractures were most frequently associated with fractures at other sites within the mandible, ipsilateral body fractures being the most common. CONCLUSIONS: Updated data on the association of patient age and mechanism of injury with fracture pattern can guide treating physicians in anticipating and diagnosing traumatic mandible fractures.

Accidents, Traffic↗
PubMed2006

Cytogenetic and fluorescence in situ hybridization analysis of a basal cell adenocarcinoma of the mandible.

Basal cell adenocarcinoma (BCAC) of the salivary glands is rare. Distant metastasis to the mandible from a salivary gland tumor is also considered rare. The cytogenetic finding of a case of metastatic BCAC of the mandible is described. We are unaware of earlier reports regarding cytogenetic findings of BCAC either at the primary site or at a distant metastasis site. An 80-year-old female with primary BCAC of the parotid salivary gland underwent parotidectomy and chemotherapy. One year later, a metastatic lesion in the mandible was found. Tissue specimens from the mandibular lesion were tested by the following pathologic methods: hematoxylin-eosin and immunohistochemistry for CK8/18, CK/903, vimentin, and smooth muscle actin. The characteristic histologic architecture of BCAC found in the mandible was similar to that of the earlier findings of the tumor in the parotid gland. A fresh sample from the mandibular lesion was examined by cytogenetics and fluorescence in situ hybridization (FISH), using centromeric probes for chromosomes 4, 8, 10, 18, and 22. A paraffin-embedded sample of the primary tumor was also examined by FISH. Cytogenetic and FISH analyses of the mandibular metastatic lesion revealed a clone with a pericentric inversion of chromosome 17 and a clone with trisomy 4, respectively. Trisomy 4 was also found in the paraffin-embedded samples of the primary parotid tumor.

Adenocarcinoma↗