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PubMed1976

Primary tumors of the mandible. A study of 49 cases.

Forty-nine cases of primary tumors of the mandible have been reviewed. The anatomic location, pathologic features, sites of metastases, survival rates, and treatment methods were evaluated. Lesions studied included ameloblastoma, osteogenic sarcoma, reticulum cell sarcoma, fibrosarcoma, chondrosarcoma, myxosarcoma, epidermoid carcinoma, adenocarcinoma, and giant cell sarcoma. An in-depth discussion of primary osteogenic sarcoma of the mandible is presented. Because of upper cervical lymph node metastases in two cases of osteogenic sarcoma of the mandible, an upper neck dissection should be considered in the primary treatment. Also presented in this study are the first reported cases or primary myxosarcoma of the mandible and giant cell sarcoma of the mandible. Recent methods of treatment of ablative resection of the mandible followed by immediate or delayed repair are discussed. A revised technic for mandibular replacement which has met with success in six of seven cases is presented.

Adenocarcinoma↗
PubMed1976

Posterior accessory foramina of the human mandible.

A study was performed on 150 dry, adult, human mandibles from cadavers of unspecified sex and unknown ethnic background, which had been imported from India. These mandibles were placed in the "standard basal position" and topographically divided into 11 bilateral areas posterior to the second bicuspid teeth. The accessory foramina in these areas were studied to determine their mean diameter, incidence of occurrence, and the areas in which they occurred. The medical surfaces of the mandibles exhibited foramina more frequently and in greater numbers than did the lateral surfaces. The right and left halves of the mandibles showed remarkable similarity. Much of the data obtained correlated with previous investigations, indicating that neurovascular components enter and leave the body on the mandible in the posterior region. Foramina 0.4 mm. or larger in diameter were evaluated separately. These larger foramina occur most often in the superior and middle thirds on the medial surface of the ramus (areas 6 and 7). They also occur fairly frequently in the retromolar area (area 11). This information can be usefully applied to future dissection studies concerning the soft-tissue components of these foramina. The data obtained reveal that these foramina occur frequently and in approximately the same locations. This suggests that these foramina are functionally important in supplying neural and/or vascular components to the mandible.

Adult↗
PubMedDate not supplied

Osteoradionecrosis of the mandible: pathogenesis.

Although the precise pathogenic mechanisms are not fully understood, osteoradionecrosis of the mandible is caused by radiation-induced cellular injury, ultimately resulting in a chronic, nonhealing wound. This etiology does not explain the strong predisposition of the mandible to radionecrosis relative to the maxilla, and overlooks the contribution of ischemic necrosis due to radiation-induced disturbances in circulation. In this study, irradiated mandibles with and without osteoradionecrosis and nonirradiated mandibles were examined histologically. Our findings show that osteoradionecrosis of the mandible is an ischemic necrosis due to radiation-induced obliteration of the inferior alveolar artery, while revascularization by branches of the facial artery is disturbed by radiation-induced vascular disease and periosteal damage. The most vulnerable part of the mandible is the buccal cortex of the premolar, molar, and retromolar regions.

Humans↗
PubMed1986

The effects of mandibular retractive force on the growing rat mandible.

The purpose of this study was to investigate the three-dimensional effects of a mandibular retractive force on the growing rat mandible and mandibular growth after the force was removed. Eighty 4-week-old male Wistar rats served as experimental animals and 100 4-week-old male Wistar rats served as the control group. The experimental rats were divided into four groups. Thirty grams of retractive force was applied to each mandible for 4 weeks. Each group was then killed after 4-, 8-, 10-, 12-, or 16-week periods. At the time of death, tibia, skull, and mandible were removed, measurements of those bone specimens were taken, and histologic examinations were performed. Compared with the control group, the experimental group demonstrated no significant differences in body weight nor in the length of measurements of the tibia, skull, and proximal end of the tibia. The mandibles of the experimental group demonstrated shorter anteroposterior length, higher coronoid processes, and a thicker corpus in the retromolar region and condylar neck. The condylar cartilages of the experimental group showed moderate adaptation in the histologic sections. However, mandibles of the experimental animals did not show any catch-up growth behavior after removal of the force. It was concluded that the mandibular retractive force could produce overall growth retardation and transformation of growing rat mandibles, but the force had no effect on the growth behavior after the appliance was removed.

Animals↗
PubMed2005

ESR and U-series analyses of enamel and dentine fragments of the Banyoles mandible.

The Banyoles mandible presents a puzzle. Its anatomy has been described as pre-Neandertal, but the travertine in which it was found has been dated to 45,000 +/- 4000 years. By this time, any pre-Neandertals had supposedly been absent from the European fossil record for more than 100,000 years. It was therefore proposed that the age of the travertine may represent a minimum age estimate, with the mandible possibly having been reworked from older deposits. We carried out a non-destructive ESR analysis of an enamel fragment removed from a molar and performed a series of in situ laser ablation U-series analyses on dentine fragments adjacent to the enamel piece. The analyses resulted in an apparent combined ESR-U-series age of 66,000 +/- 7000 years. The encasing travertine matrix was also analyzed for U-series isotopes and showed signs of U-mobilization. It cannot be excluded that the travertine matrix is older than the previously determined age. If the mandible was not reworked, then the combined ESR-U-series result on the tooth enamel would give its best age estimate. If, on the other hand, the mandible was reworked from another deposit, the actual ESR-U-series age will depend on the external dose rate from the previous matrix and the depth of its burial, which controls the degree of the attenuation of the cosmic dose rate over time. Considering a range of possible burial histories, the mean age of the mandible would lie somewhere between the combined ESR-U-series age and the previously determined age of the travertine matrix. Regarding the morphology of the mandible, a review of its features in the context of larger Neandertal samples indicates that the anatomy of the specimen is not incompatible with such a young age determination, although it further highlights morphological variation in the late Neandertal sample.

Age Determination by Teeth↗
PubMed2003

Postural stability of the human mandible during locomotion.

Movements of the head and of the mandible relative to the head were measured in human subjects walking and running on a treadmill at various speeds and inclinations. A miniature magnet and piezo-electric accelerometer assembly was mounted on the mandibular incisors, and a Hall-effect sensor along with a second accelerometer mounted on a maxillary incisor along a common vertical axis. Signals from these sensors provided continuous records of vertical head and mandible acceleration, and relative jaw position. Landing on the heel or on the toe in different forms of locomotion was followed by rapid deceleration of the downward movement of the head and slightly less rapid deceleration of the downward movement of the mandible, i.e., the mandible moved downwards relative to the maxilla, then upwards again to near its normal posture within 200 ms. No tooth contact occurred in any forms of gait at any inclination. The movement of the mandible relative to the maxilla depended on the nature and velocity of the locomotion and their effects on head deceleration. The least deceleration and hence mandibular displacement occurred during toe-landing, for example, during "uphill" running. The maximum displacement of the mandible relative to the head was less than 1mm, even at the fastest running speed. The mechanisms that limit the vertical movements of the jaw within such a narrow range are not known, but are likely to include passive soft-tissue visco-elasticity and stretch reflexes in the jaw-closing muscles.

Acceleration↗
PubMed1997

Characteristics of the cancellous bone of edentulous mandibles.

Trabecular bone volume and trabecular connectivity (trabecular bone pattern factor) of edentulous mandibles were examined using undecalcified bone sections from the region of the 1st premolar to investigate atrophy-related changes in mandibular cancellous bone. The mean trabecular bone volume was 21.8% in female mandibles and 36.6% in male mandibles. The mean trabecular bone pattern factor was -0.22 mm-1 for female mandibles and -2.29 mm-1 for male mandibles. The difference between the sexes was statistically conspicuous for both parameters, but did not attain statistical significance. A notable fact was the extreme range of variation in both trabecular bone volume and trabecular connectedness. A difference of 65% between the highest and the lowest trabecular bone volumes measured in the present study (min, 7.6%; max, 73.6%, both male) reflects the possible variation in trabecular density of edentulous mandibles.

Aged↗
PubMed2000

Variation in shape of the lingula in the adult human mandible.

The lingulae of both sides of 165 dry adult human mandibles, 131 males and 34 females of Indian origin, were classified by their shape into 4 types: 1, triangular; 2, truncated; 3, nodular; and 4, assimilated. Triangular lingulae were found in 226 (68.5%) sides, truncated in 52 (15.8%), nodular in 36 (10.9%) and assimilated in 16 (4.8%) sides. Triangular lingulae were found bilaterally in 110, truncated in 23, nodular in 17 and assimilated in 7 mandibles. Of the remaining 8 mandibles with different appearances on the 2 sides, 6 had a combination of triangular and truncated and 2 had nodular and assimilated. The incidence of triangular and assimilated types in the male and female mandibles are almost equal. In the truncated type it was double in the male mandibles while the nodular type was a little less than double in the female mandibles.

Adult↗
PubMed2003

The growth and morphogenesis of the early mouse mandible: a quantitative analysis.

Three-dimensional reconstruction and BrdU incorporation have been used to quantify the development and growth of the mouse mandible and to analyse its relationship to Meckel's cartilage and the molar teeth. The mandible anlage is first histologically detectable at E13.5 as paired plates of osteoid tissue within condensed mesenchyme (approximately 0.9 mm long and approximately 0.36 mm deep) that are lateral to the two arms of Meckel's cartilage. Over the next 3 days, each plate lengthens to approximately 3.6 mm, and extends medially at its superior and inferior edges, folding over to enclose the alveolar nerve and Meckel's cartilage and producing additional processes that form the molar tooth sockets (E15.5). At around E15.5, the first molar tooth socket forms from two processes that extend from the medial and distal parts of the mandible to surround the tooth. By E16.5, this process is complete in the distal region where Meckel's cartilage is beginning to degenerate. Mandible ossification begins at E14 with proliferation restricted to the outer surface. BrdU incorporation rates are particularly high at the proximal and distal ends where lengthening occurs, and at the superior and inferior edges as they extend medially to surround Meckel's cartilage. Incorporation rates slow at the distal ends of each mandible at E16.5 as they approach each other at the symphysis. The results indicate that the mandible mainly grows at its periphery, and the pattern of mandibular growth and morphogenesis suggests that these processes are mainly directed and constrained by paracrine signalling from Meckel's cartilage and the tooth buds.

Animals↗
PubMed2003

[Quantitative analysis of contrast enhanced MRI of the inferior alveolar nerve in inflammatory changes of the mandible].

PURPOSE: To evaluate the role of contrast enhanced MRI in quantifying signal changes of the inferior alveolar nerve following inflammatory changes of the mandible. MATERIAL AND METHODS: 30 patients with inflammatory changes of the mandible underwent MRI of the face. Both sides of the mandible, the affected as well as the unaffected healthy side were evaluated retrospectively. Regions of interest were placed at 5 defined places on both sides to assess signal intensity before and after intravenous application of paramagnetic contrast agent. The results of the measurements were compared between the healthy and the affected side (t-test, p < 0.05) and correlated with clinical findings (t-test, p < 0.05). RESULTS: All patients with hypesthesia of the inferior alveolar nerve in areas of the lips or chin (n = 4) showed a marked increase in signal intensity from 35 % to 83 % distal to the inflammatory process. Patients without sensitivity disorders showed less increase in signal intensity with a maximum of 51 % distal to the inflammatory process. In nearly all patients no contrast enhancement was observed distal to the first molar on the unaffected side. CONCLUSIONS: Quantitative analysis of contrast enhanced MRI of the neurovascular bundle is able to show pathologic mandibular lesions. In case of inflammatory changes of the mandible the neurovascular bundle is able to show pathologic mandibular lesions. In case of inflammatory changes of the mandible, the neurovascular bundle shows a significant increase in signal intensity distal to the lesion compared to the unaffected healthy side of the mandible.

Adolescent↗
PubMed2001

Translation and rotation of the mandible during habitual mouth opening movement in children with anterior reverse bite in the primary dentition.

Translation and rotation of the mandible during habitual mouth opening movements were studied in 13 children with skeletal-based anterior reverse bite (reverse bite group) and in 13 children with normal occlusion (normal occlusion group) whose dental stage was the primary dentition. Movements were recorded by an opto-electronic movement-analyzing system that could measure mandibular movements with six degrees of freedom. Inferior translation of the mandible was analyzed at the left primary central incisor, both of the primary canines, and both of the primary second molars. Anterior translation of the mandible was analyzed at both of the condyles. Rotation of the mandible was measured in the sagittal plane. The results showed that the associations between the translation and rotation of the mandible during habitual mouth opening in the reverse bite group differed from those in the normal occlusion group. The reverse bite group had greater anterior translation of both of the condylar points than did the normal occlusion group. No significant differences were found in the inferior translation or rotation of the mandible between the two groups.

Analysis of Variance↗
PubMed2003

The geometry of the marmot (rodentia: sciuridae) mandible: phylogeny and patterns of morphological evolution.

Marmots have a prominent role in the study of mammalian social evolution, but only recently has their systematics received the attention it deserves if sociobiological studies are to be placed in a phylogenetic context. Sciurid morphology can be used as model to test the congruence between morphological change and phylogeny because sciurid skeletal characters are considered to be inclined to convergence. However, no morphological study involving all marmot species has ever been undertaken. Geometric morphometric techniques were applied in a comparative study of the marmot mandible. The adults of all 14 living marmot species were compared, and mean mandible shape were used to investigate morphological evolution in the genus Marmota. Three major trends were observed. First, the phylogenetic signal in the variation of landmark geometry, which describes mandible morphology, seems to account for the shape differences at intermediate taxonomic levels. The subgenera Marmota and Petromarmota, recently proposed on the basis of mitochondrial cytochrome b sequence, receive support from mandible morphology. When other sciurid genera were included in the analysis, the monophyly of the genus Marmota and that of the tribe Marmotini (i.e., marmots, prairie dogs, and ground squirrels) was strengthened by the morphological data. Second, the marmotine mandible may have evolved as a mosaic of characters and does not show convergence determined by size similarities. Third, allopatric speciation in peripheral isolates may have acted as a powerful force for modeling shape. This hypothesis is strongly supported by the peculiar mandible of M. vancouverensis and, to a lesser degree, by that of M. olympus, both thought to have originated as isolated populations in Pleistocene ice-free refugia.

Adaptation, Biological↗
PubMed2004

Volumetric assessment of the distracted human mandible.

The mandibles of five patients who underwent unilateral or bilateral distraction osteogenesis were analyzed using computed tomography scans. The mandibles were reconstructed in three dimensions using General Electric computed tomography software. The total volume of each hemimandible was determined before and after distraction and compared. The mandibles were then segmented at 1-cm intervals, and the volumes of the segments were determined. The volumes of the mandibular segments before and after distraction were compared to determine the distribution of new bone through the mandible and the quantity of bone generated by distraction. The distracted hemimandibles increased in total volume by an average of 19.9% (statistically significant by the Student paired t test; P < 0.0001), whereas the nondistracted hemimandibles increased in total volume by an average of 5.2%. The segmental volumes of the distracted mandible were of similar or greater volume when compared to the preoperative mandibular segments. In addition, the distribution of regenerate bone mirrored the physiological distribution of the preoperative mandibular bone. This study indicates that distraction not only creates new bone but distributes that bone through the remodeled mandible in an anatomical pattern similar to that of the preoperative bone.

Bone Density↗
PubMed1997

A CT scan technique for quantitative volumetric assessment of the mandible after distraction osteogenesis.

Distraction osteogenesis has become an accepted method of treatment for patients requiring reconstruction of hypoplastic mandibles. We present a quantitative analysis of volumetric changes after distraction osteogenesis in a series of 10 patients. Group I (n = 5 patients, 3 unilateral craniofacial microsomia, 1 Goldenhaar syndrome, and 1 bilateral craniofacial microsomia) underwent unilateral distraction of the mandible. Group II (n = 5 patients, 1 Nager syndrome, 1 bilateral craniofacial microsomia, 1 developmental micrognathia, and 2 Treacher Collins syndrome) underwent bilateral distraction of the mandible. Predistraction and postdistraction axial and three-dimensional computed tomographic (CT) scans were digitized and transferred to a computer for analysis with image-processing software to determine the changes in volume of the mandible and bony regenerate. The CT-derived volume method was validated by scanning three dry cadaver mandible specimens and comparing the volume data with those derived from a water-displacement method. The difference between the two methods was less than 5 percent. The mean distracted length, as recorded from the calibrated device, was 22.6 mm in the 10 patients. In the unilateral distraction group, the mean increase in hemimandibular bone volume was 2.8 cc, with a mean percentage increase of 27 percent in the distracted hemimandible. In the bilaterally distracted patients, the mean increase in total mandibular volume was 7.9 cc, with a mean percentage increase in bone volume of 25 percent. This study represents the first attempt to quantify the increase in bone volume resulting from distraction osteogenesis. Quantitative volumetric analysis of CT scans is an accurate method to measure the amount of bone regenerate in patients undergoing distraction osteogenesis of the mandible or the extremities. The concept and utility of quantifying the volumetric changes in bone following distraction osteogenesis may become more important as multiplanar devices are developed and used in other areas of the craniofacial skeleton.

Adolescent↗
PubMed2006

Management of mandible fractures.

LEARNING OBJECTIVES: After studying this article, the participant should be able to: 1. Review the incidence and etiology of mandible fractures. 2. Discuss indications and techniques for closed and open treatment of mandible fractures. 3. Review complications of mandible fractures. BACKGROUND: Mandible fractures are among the most common types of facial fractures treated by plastic surgeons. They must be managed carefully to maintain the function of the mandible, reestablish proper occlusion, and minimize secondary complications. METHODS: Current methods of management include combinations of soft diet, intermaxillary fixation, open reduction with plate fixation, and, rarely, external fixation. RESULTS: Decision-making depends on the age of the patient, type of fracture identified, and concomitant medical conditions or injuries. CONCLUSION: The authors review the diagnosis and current trends in management of mandible fractures.

Adult↗
PubMed1985

In vivo measurement of bone mineral content of mandibles by dual-photon absorptiometry.

The purpose of this study was 1) to reveal the short- and long-term precision of noninvasive in vivo measurements of bone mineral content (BMC) in larger and smaller parts of mandibles and in forearm bones by a new two-dimensional dual-photon attenuation system GT45; 2) to develop normal reference values and ranges for mandibular BMC in individuals between 20-40 yr of age without known systemic diseases and with normal oral state, (n = 56, F:M = 1:1), and 3) to relate mandibular BMC with forearm bone BMC, sex and age, by comparing BMC values of a well-defined normal old test group (n = 24, F:M = 1:1, 70-81 yr of age) with the normal reference values. The analyses indicated: 1) the in vivo short- and long-term precision of the methods is high. 2) BMC of mandibles and forearm bones is significantly related to sex and age (P less than 0.01, and in mandibles of young females/males: P = 0.02). 3) BMC in mandibles and forearm bones is significantly correlated in both age groups (P less than 0.01) with relatively weak coefficients of correlation. GT45 may be used to follow BMC changes in mandibles in groups or single individuals after surgical treatment and to evaluate sex and age dependent BMC changes in mandibles and forearm bones.

Adult↗
PubMed2000

Biomechanics of the mandible.

In this review the biomechanical behavior of the mandibular bone tissue, and of the mandibular bone as a whole, in response to external loading is discussed. A survey is given of the determinants of mandibular stiffness and strength, including the mechanical properties and distribution of bone tissue and the size and shape of the mandible. Mandibular deformations, stresses, and strains that occur during static biting and chewing are reviewed. During biting and the powerstroke of mastication, a combination of sagittal bending, corpus rotation, and transverse bending occurs. The result is a complex pattern of stresses and strains (compressive, tensile, shear, torsional) in the mandible. To be able to resist forces and bending and torsional moments, not only the material properties of the mandible but also its geometrical design is of importance. This is reflected by variables like polar and maximum and minimum moments of inertia and the relative amount and distribution of bone tissue. In the longitudinal direction, the mandible is stiffer than in transverse directions, and the vertical cross-sectional dimension of the mandible is larger than its transverse dimension. These features enhance the resistance of the mandible to the relatively large vertical shear forces and bending moments that come into play in the sagittal plane.

Animals↗
PubMed2002

Edentulation alters material properties of cortical bone in the human mandible.

Ridge resorption following edentulation has been documented clinically, but the effects of tooth loss on the material properties of mandibular cortical bone have received little study. Material properties and their structural basis are essential for our understanding of bone quality in the edentulous mandible and are of interest as a tissue-level model for functional adaptation. This study's aim was to determine material property variability in the edentulous mandible, and to compare it with data from a previous study of dentate mandibles. Forty-four cortical samples were removed from each of 10 adult fresh edentulous mandibles. Cortical thickness and density were measured. Material properties were calculated from ultrasonic velocities. Mandibular cortical bone in the edentulous mandibles differed from that of dentate mandibles in cortical thickness, elastic and shear moduli, anisotropy, and orientation of the axis of maximum stiffness. These results suggest that cortical microstructural changes accompany ridge resorption following edentulation.

Aged↗