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PubMed2006

Determination of dimensions and angles of mandible in the fetal period.

The aim of the present study was to determine the dimensions of the mandible during the fetal period, the relationship between the growth rates of the angle of the mandible and the dimensions of the mandible. Furthermore the angle of union of the two halves of the body of the mandible on the horizontal mandibular plane, which was not described elsewhere, is explored in this study. One hundred and sixty-one human fetuses (83 males and 78 females) without any cranio-facial or mandibular asymmetry, external pathology or anomaly and aged between 9 and 40 weeks of gestation were used in the study. Cases were stratified into four groups according to their developmental ages, that is, first trimester, second trimester, third trimester, and term fetuses. Cranio-facial parameters in addition to bi-condylar, bi-gonial, bi-mental tubercular, condyle-gonion, gonion-mental tubercle, condyle-mental tubercle, gonion-pogonion distances were measured. The degree of the angle of the mandible, angle of union of the two halves of the body of the mandible and sagittal length of the base of the mandible were calculated. The means of the parameters with respect to gestational weeks and groups were computed. While there were no sex differences in any of the parameters (P>0.05) there were very significant relationships between gestational age and parameters (P<0.001). The mean degree of the angle of the mandible during the fetal period was 122+/-8 degrees . The mean alpha angle of the base of the mandible was 65+/-8 degrees . None of these angles varied significantly throughout the fetal period. Height of the ramus of the mandible increased more than the length of the body of the mandible and bi-gonial distance in the first and second trimesters while in the third trimester and term period they increased at the same rate. Comparisons of groups for the ratio of the transverse to the sagittal lengths of the mandible revealed significant differences between first and second trimesters with term group (P<0.05). Accordingly, bi-gonial distance of the mandible increased more during the third trimester and term time than the first and second trimesters, compared with the sagittal length of the mandible. The morphometric features and architectural changes observed in the mandible do not totally occur during the fetal period but continue later in childhood and adulthood.

Body Weights and Measures↗
PubMed2006

Neural symmetry and functional asymmetry of the mandible.

Even in the absence of malformation or skull base asymmetry, the mandible may be physiologically asymmetric and this remains a major challenge in the orthodontic treatment. The mandible is a bone formed by a primary subunit, i.e., the neural part, with different functional secondary subunits, so we suggest that in a normal mandible the asymmetry was caused by the secondary functional subunit and the neural part is nearly symmetric. Eighty-three dry human mandible samples were studied. The measurements of the size of the mandible (corpus, ramus, mandible notch, condylar process, the angle of the mandible) and the neural subunit (the mandibular canal and the position of the mental and mandibular foramina) were measured bilaterally. The left and right sides were compared according to the dental status: 60 dentate and 23 edentulous mandibles. The calculation of the symmetry was based on the paired Student t test, the absolute difference |R-L| and the relative absolute difference |R-L|/|R+L|x100. The mandibular canal and the position of the foramina were symmetric, except for the position of the mandibular foramen in relation to the mandible notch. The symmetry was not modified by the dental status. The total length of the mandible and the length of the ramus were greater on the left side independently from the dental status. The length of the corpus and the mandible angle were symmetric in each group. The mandible notch was always asymmetric and its height was greater in the dentate group. The condylar process was the most asymmetric structure in each group. The primary subunit of the mandible, surrounding the mandibular canal, is a symmetric component of the mandible and is not modified by the dental status. The angle of the mandible between the corpus and ramus is another symmetric parameter that is important for the facial architecture. The ramus and especially the mandibular notch as well as the condylar process are the most asymmetric subunits influenced by the functional matrices.

Analysis of Variance↗
PubMed2002

The fetal mandible: a 2D and 3D sonographic approach to the diagnosis of retrognathia and micrognathia.

OBJECTIVE: To define parameters that enable the objective diagnosis of anomalies of the position and/or size of the fetal mandible in utero. DESIGN: Fetuses at 18-28 gestational weeks were examined by two- and three-dimensional ultrasound. The study included normal fetuses and fetuses with syndromes associated with known mandible pathology: Pierre Robin sequence or complex (n = 8); hemifacial microsomia (Treacher-Collins syndrome, n = 3); postaxial acrofacial dysostosis (n = 1). Fetuses with Down syndrome (n = 8) and cleft lip and palate without Pierre Robin sequence or complex (n = 18) were also studied. Retrognathia was assessed through the measurement of the inferior facial angle, defined on a mid-sagittal view, by the crossing of: 1) the line orthogonal to the vertical part of the forehead at the level of the synostosis of the nasal bones (reference line); 2) the line joining the tip of the mentum and the anterior border of the more protruding lip (profile line). Micrognathia was assessed through the calculation of the mandible width/maxilla width ratio on axial views obtained at the alveolar level. Mandible and maxilla widths were measured 10 mm posteriorly to the anterior osteous border. RESULTS: In normal fetuses, the inferior facial angle was constant over the time span studied. The mean (standard deviation) value of the inferior facial angle was 65.5 (8.13) degree. Consequently, an inferior facial angle value below 49.2 degree (mean - 2 standard deviations) defined retrognathism. All the fetuses with syndromes associated with mandible pathology had inferior facial angle values below the cut-off value. Using 49.2 degree or the rounded-up value of 50 degree as a cut-off point, the inferior facial angle had a sensitivity of 1.0, a specificity of 0.989, a positive predictive value of 0.750 and a negative predictive value of 1.0 to predict retrognathia. In normal fetuses, the mandible width/maxilla width ratio was constant over the time interval studied. The mean (standard deviation) value was 1.017 (0.116). Consequently, a mandible width/maxilla width ratio < 0.785 defined micrognathism. Mandible width/maxilla width ratio values were below this cut-off point in eight and in the normal range in four fetuses with syndromes associated with mandible pathology. CONCLUSIONS: Retrognathia and micrognathia are conditions that can be separately assessed. The use of inferior facial angle and mandible width/maxilla width ratio should help sonographic recognition and characterization of fetal retrognathic and micrognathic mandibles in utero.

Cephalometry↗
PubMed2003

Maxillae and mandibles of male mosquitoes and female autogenous mosquitoes (Diptera: Culicidae).

Maxillae and mandibles of males of 44 species of 12 mosquito genera and females of three autogenous genera and two partially autogenous species were examined under light microscopy and scanning electron microscopy. The maxillae and mandibles of male mosquitoes are delicate, tape-like structures with lengths characterizing genera or higher level classification units. Five patterns are recognized: (A) long maxillae and mandibles with mandibles longer than maxillae in Anopheles; (B) long maxillae and mandibles with maxillae longer than mandibles in Toxorhynchites; (C) short or intermediate lengths of maxillae with short mandibles in Aedes, Armigeres, Culex, Ochlerotatus, Orthopodomyia, and Uranotaenia; (D) short or intermediate length of maxillae with no mandibles in Mimomyia and Tripteroides; and (E) no maxillae and mandibles in Malaya and Topomyia. Maxillary and mandibular lengths of male mosquitoes show a positive correlation. Length of maxillae and mandibles of autogenous females are reduced to the same level as conspecific males. In contrast, females of partially autogenous species have complete maxillae and mandibles as in females of anautogenous species.

Animals↗
PubMed2000

Elastic properties and masticatory bone stress in the macaque mandible.

One important limitation of mechanical analyses with strain gages is the difficulty in directly estimating patterns of stress or loading in skeletal elements from strain measurements. Because of the inherent anisotropy in cortical bone, orientation of principal strains and stresses do not necessarily coincide, and it has been demonstrated theoretically that such differences may be as great as 45 degrees (Cowin and Hart, 1990). Likewise, relative proportions of stress and strain magnitudes may differ. This investigation measured the elastic properties of a region of cortical bone on both the buccal and lingual surfaces of the lower border of the macaque mandible. The elastic property data was then combined with macaque mandibular strain data from published and a new in vivo strain gage experiment to determine directions and magnitudes of maximum and minimum principal stresses. The goal was to compare the stresses and strains and assess the differences in orientation and relative magnitude between them. The main question was whether these differences might lead to different interpretations of mandibular function. Elastic and shear moduli, and Poisson's ratios were measured using an ultrasonic technique from buccal and lingual cortical surfaces in 12 macaque mandibles. Mandibular strain gage data were taken from a published set of experiments (Hylander, 1979), and from a new experiment in which rosette strain gauges were fixed to the buccal and lingual cortices of the mandibular corpus of an adult female Macaca fascicularis, after which bone strain was recorded during mastication. Averaged elastic properties were combined with strain data to calculate an estimate of stresses in the mandibular corpus. The elastic properties were similar to those of the human mandibular cortex. Near its lower border, the macaque mandible was most stiff in a longitudinal direction, less stiff in an inferosuperior direction, and least stiff in a direction normal to the bone's surface. The lingual aspect of the mandible was slightly stiffer than the buccal aspect. Magnitudes of stresses calculated from average strains ranged from a compressive stress of -16.00 GPa to a tensile stress of 8.84 GPa. The orientation of the principal stresses depended on whether the strain gage site was on the working or balancing side. On the balancing side of the mandibles, maximum principal stresses were oriented nearly perpendicular to the lower border of the mandible. On the working side of the mandibles, the orientation of the maximum principal stresses was more variable than on the balancing side, indicating a larger range of possible mechanisms of loading. Near the lower border of the mandible, differences between the orientation of stresses and strains were 12 degrees or less. Compared to ratios between maximum and minimum strains, ratios between maximum and minimum stresses were more divergent from a ratio of 1.0. Results did not provide any major reinterpretations of mandibular function in macaques, but rather confirmed and extended existing work. The differences between stresses and strains on the balancing side of the mandible generally supported the view that during the power stroke the mandible was bent and slightly twisted both during mastication and transducer biting. The calculated stresses served to de-emphasize the relative importance of torsion. On the working side, the greater range of variability in the stress analysis compared to the strain analysis suggested that a more detailed examination of loadings and stress patterns in each individual experiment would be useful to interpret the results. Torsion was evident on the working side; but in a number of experiments, further information was needed to interpret other superimposed regional loading patterns, which may have included parasagittal bending and reverse parasagittal bending.

Animals↗
PubMed1976

The remodeling of the edentulous mandible.

In a sample of mandibles having complete or nearly complete loss of dentition, the left half of each mandible was serially sectioned. The entire perimeter of each section was analyzed for the distribution of resorptive and depository periosteal surfaces, and from this information, the fields of remodeling were mapped for the mandible as a whole. The most common patterns of combined resorption-deposition and the range of variations were then determined. The over-all distribution of remodeling fields in the edentulous mandible differs markedly from that in the young, growing mandible. In most of the edentulous specimens, the surface of the basal bone on both the medial and lateral sides of the corpus is of a depository nature. The overlying alveolar regions on both the lingual and buccal sides, however, are characteristically resorptive. Significantly, the placement of the reversal line between the alveolar resorptive and the basal depository areas is much lower (i.e., at the level of the mental foramen) on the buccal side. Except for its inferior part, the lateral side of the ramus tends to be largely resorptive in character, and the posterior half of the lingual side also tends to be resorptive. Unlike the child's mandible, the posterior border of the ramus is resorptive, and the posteroanterior dimension of the ramus (not the whole mandible) becomes reduced and narrowed in conjunction with resorption along the anterior border. However, the amount removed from the anterior ramus is actually added to the dimension of the corpus, which becomes longer. Further, removal from the posterior ramus border does not affect the over-all length of the mandible unless condylar reduction is also involved. Also, over-all arch length is not decreased, because the surface of the mental protuberance is retained as a depository type of field (or at least does not become actively resorptive). The corpus-ramus angle (not gonial angle) is increased in the antegonial region. Because of the opening of this angle, over-all mandibular length as well as arch length is increased. In about half of the specimens, arch width was not decreased, because the lateral side of the corpus is usually of a depository nature. Notching of the anterior side of the condylar neck and the inferior part of the anterior ramus border is associated with resorptive fields in these regions, changes that are presumed to be a consequence of pressure contacts made with the articular tubercle and the maxillary tuberosity, respectively, in conjunction with a forward rotation of the whole mandible. The inferior direction of corpus realignment relative to the basal part of the ramus also increases the notching effect in the antegonial region, an effect augmented by the presence of the resorptive field in the notch itself. Certain specific variations commonly occur in several major regions of the mandible on both the lateral and medial sides...

Alveolar Process↗
PubMed2000

The oblique radiographic technique for bone height measurements on edentulous mandibles: a preclinical study and an introduction to the clinical use.

OBJECTIVE: The aim of this study was to quantify the effect of mandibular angulation, position, and shape of the edentulous mandible on the distortion of its image on lateral oblique radiographs in a preclinical study. Suggestions for the clinical use of this technique are made. STUDY DESIGN: Five edentulous dry mandibles were used, varying in size from small to wide and equipped with metal bars in and on top of the mandible. The mandibles were radiographed at 9 different positions by tilting the mandible around the intercondylar axis and by using the oblique projection technique in a cephalostat. RESULTS: The length of the images of the metal bars varied significantly when we tilted the mandibles from 20 degrees to -20 degrees. As a result of the effects of magnification and distortion, the image size varied from between 0.96% and 1.06% of the real size. Neither the size of the mandible nor the position of the bars was related to the degree of magnification. CONCLUSION: The oblique projection technique has limited geometric errors in depicting the edentulous mandible. For evaluative bone height measurements in patients with extremely resorbed mandibles treated with dental implants, it is a promising technique if the patient (specifically the mandible) can be positioned reproducibly in the apparatus.

Analysis of Variance↗
PubMed1997

Bone height measurements on panoramic radiographs: the effect of shape and position of edentulous mandibles.

OBJECTIVE: The aim of this study was to quantify the effect of mandibular angulation, position, and shape of an edentulous mandible on the distortion of its image in panoramic radiographs. STUDY DESIGN: Five edentulous dry mandibles varying in size from small to wide and equipped with metal bars in and on top of the mandible were used. The mandibles were radiographed at nine different positions by tilting the mandible posteriorly around a transversal axis, using an orthopantomograph. RESULTS: The length of the images of the bars on top of the mandible increased significantly by tilting the mandibles from +20 degrees to -20 degrees. The magnification factor of the images of the intrabony bars in the mandible was the largest at 0 degrees and decreased significantly by both decreasing or increasing the inclination. The size of the mandible was not related to the magnification factor. CONCLUSION: For both diagnostic and evaluation purposes of the edentulous mandible, the panoramic radiograph is not a reliable radiographic technique unless meticulous precautions are taken for reproducible positioning of the patient in the apparatus.

Acrylic Resins↗
PubMed1996

Median cleft of the lower lip and mandible: case reports, a new embryologic hypothesis, and subdivision.

Median clefts of the lower lip and mandible are rare. In the literature so far, about 62 cases have been described. In addition, three more patients are presented here. These cases show a broad variation in the severity of this deformity, ranging from a simple notch in the vermillion to a complete cleft of the lip involving the tongue, the chin, the mandible, the supporting structures of the median of the neck, and the manubrium sterni. Several hypotheses concerning the pathogenesis of median clefts of the lip and mandible have been proposed. Most authors consider it to be a failure of fusion of the first pair of branchial arches or failure of mesodermal penetration into the midline. From our embryologic point of view, however, instead of paired branchial arches, only one first branchial arch develops during the early embryonic period (< or = 17 mm crown-rump length). Within this first branchial arch, two mandibular processes grow out, separated by a groove in the median. These mandibular processes do not fuse but merge during the late embryonic period (> or = 17 mm to < or = 60 mm crown-rump length). In the same developmental period, there is formation of the lip and the alveolar process and the anlage and outgrowth of one membrane bone center in each mandibular process, resulting in the formation of the mandible with its symphysis. As a consequence of the preceding, we propose the following subdivision of the median clefts of the lip and/or mandible: Hypoplasia of the mandibular processes during the early embryonic period will lead to the severest cleft of the mandible extending into the neck. During the late embryonic period, the less severe median clefts will develop. Disturbances of the outgrowth of bone centers of the mandible, resulting in nonformation of its symphysis, cause clefting of the mandible with involvement of all related soft tissues. Defects in the merging process produce just a notch of the vermilion or a higher cleft of the lower lip with or without involvement of the alveolar process of the mandible. In conclusion, the variety of the clefts in the median of the lower lip and/or mandible as well as the low rate of incidence can be explained by the embryologic hypothesis proposed here.

Female↗
PubMed2001

Occurrence of neanderthal features in mandibles from the Atapuerca-SH site.

Analysis of variation and distribution of evolutionary novelties is meaningful in understanding evolutionary processes. The mandible, as a morphological complex, comprises a large number of derived Neanderthal features. The present study investigates whether the features usually considered as European lineage apomorphies evolved independently; the occurrence of these features is studied in the mandibles from the Sima de los Huesos (SH) site (Atapuerca, Spain). For comparative purposes, a large sample of Neanderthal mandibles as well as older fossil Homo specimens have been used for the study. Chi-square tests were employed to test for independence. The SH mandibles present a set of features that clearly show the basic architecture of the Neanderthal mandible. A highly significant association is detected in the variation of the position of the mental foramen, the lateral prominence, and the anterior marginal tubercle, as well as in the development of retromolar space. However, a much weaker association is detected in the features of the internal aspect of the mandible, with a few exceptions. Features of the external aspect of the mandible occur chronologically earlier than those observed in the internal aspect. The hypothesis that two distinct and consecutive morphological processes have driven the emergence of the European lineage throughout the Middle Pleistocene is proposed. A first transformation affects the mandible by means of backwards displacement of the structures located at the external aspect, as well as the position of the condyle. A second process would modify the features of the internal aspect of the mandible, in which the relief of the masseteric and pterygoid fossae are affected, in association with a spatial rearrangement of the corpus and ramus. Analyzed individually, some of the considered features may be questioned as Neanderthal apomorphies (Trinkaus,1993; Franciscus and Trinkaus, 995); however, the joint occurrence of many of them suggests that the complex is an evolutionary novelty.

Adolescent↗
PubMed2002

Patterns of invasion and routes of tumor entry into the mandible by oral squamous cell carcinoma.

BACKGROUND: An understanding of the patterns, spread, and routes of tumor invasion of the mandible is essential in deciding the appropriate level and extent of mandibular resection in oral squamous cell carcinoma. METHODS: A prospective study of histologic patterns of tumor invasion and routes of tumor entry into the mandible was performed in a consecutive series of 100 previously untreated patients. RESULTS: The pattern of tumor invasion of the mandible depended on the depth of invasion both in the hard (p =.001) and soft tissues (p =.001). There was evidence that the pattern of invasion was related to histologic prognostic indicators of the disease, such as extracapsular spread from invaded lymph nodes (p =.03). The route of tumor entry was at the point of abutment to the mandible (direct) in all 13 cases, invading the dentate part of the mandible. Fifty-five percent (23 of 42) of tumors invading the edentulous ridge entered through the occlusal (superior) surface. Direct entry to the mandible in the edentulous ridge was more likely for tumors arising in the tongue, floor of the mouth and the buccal mucosa compared with alveolar or retromolar sites (p =.003) CONCLUSIONS: Larger or more deeply invading tumors in the soft tissue are more likely to invade the mandible and show the more aggressive (invasive) form of tumor spread, reducing the options of a more conservative (rim) resection. Tumors tend to enter the mandible at the point of abutment, which in both the dentate and edentulous jaw is often at the junction of the reflected and attached mucosa. A point of tumor entry below the occlusal ridge or gingival crest should be assumed when planning rim or marginal resections of the mandible.

Adult↗
PubMedDate not supplied

Routes of entry of squamous cell carcinoma to the mandible.

A recent preliminary report of a study to determine the patterns of invasion of squamous cell carcinoma to the nonirradiated edentulous mandible indicated that tumor entered mainly through the residual alveolar occlusal ridge. This study has now been extended and includes both nonirradiated and irradiated mandibles. Of a total of 46 nonirradiated mandibles (10 partially dentate and 36 edentulous) invaded by tumor, 41 were invaded through the occlusal surface. This confirms the findings of the preliminary report. These findings indicate that there is a rational basis on pathologic grounds for adopting a conservative approach to the nonirradiated mandible. In 16 irradiated mandibles, the routes of tumor entry were found to be much more variable than in the nonirradiated mandible. In 16 irradiated mandibles, the routes of tumor entry were found to be much more variable than in the nonirradiated mandible, and multiple foci of tumor invasion of the bone were often present wherever tumor in adjacent soft tissues approached the bone. This variability of tumor entry means that a conservative approach to mandibular excision cannot be pursued in the previously irradiated mandible and full-thickness segmental resection is necessary if bone involvement appears likely.

Carcinoma, Squamous Cell↗
PubMed2004

Quantitative assessment of post-extraction healing and alveolar ridge remodelling of the mandible in female rats.

OBJECTIVE: To quantitatively evaluate the healing and bone changes in the mandible of adult female rats following unilateral extraction of the mandibular molars and the incisor. METHODS: Six-month old female rats had their mandibular molars and the incisor on one side of the mandible extracted. Nine rats were sacrificed at 0, 14, 28, 56 and 112 days post-extraction. Bone mineral density (BMD) as observed by dual energy X-ray absorptiometry (DEXA) and histomorphometric measurements of total bone volume (TBV/TV%) as well as changes in size; height and width on backscattered electron microscopy images of cross-sections of the mandible were evaluated. RESULTS: There was a total increase of 28% in BMD of the body of the mandible and 35.1% increase in TBV/TV% at 112 days post-extraction. A maximal increase of 25% in BMD was observed at 14 days post-extraction. TBV/TV% increased by 9.5% at 14 days post-extraction and further increased by 15.9% (P < 0.001) from 14 to 28 days and by 9.2% (P < 0.001) from 28 to 56 days. A further slight but non-significant increase of 6% (P = 0.108) occurred from 56 to 112 days post-extraction. Regression equations demonstrated that the maximal increase in TBV/TV% and BMD occurred between 0 and 28 days, which subsequently slowed down between 28 and 56 days and further declined between 56 and 112 days post-extraction. Healing was associated with a reduction in cross-sectional area (32.89%), height (21%) and width of the mandible (12.84%). CONCLUSIONS: BMD of the edentulous mandible following extraction of mandibular molars and the incisor on one side of the mandible increases up to 56 days, but that total bone volume increases up to 112 days post-extraction. This indicates that bone volume measurement is more sensitive than BMD measurements in detecting small increase in bone formation at later stages of healing, possibly because of changes in geometry of the edentulous mandible following teeth extraction. The edentulous mandible undergoes a significant reduction in size as a result of reduction in both height and width up to 112 days post-extraction.

Absorptiometry, Photon↗
PubMed1994

[Fundamental study on effects of different form of mouthguards on modal shape and damping ratio of human dry mandible].

Effect of 6 types of mouthguards on the vibratory characteristics of the human dry mandible was investigated by means of modal analysis with the impact test method. In this study, 20 test points were established on the mandible and the modal shape and damping ratio of the vibration of the mandible itself and the mandible each attached with a mouthguard were analyzed by using the FFT analyzer (CF-6400) and personal computer (PC-9801FA) with a modal analyzing software (VIBRANT-PC). The results were as follows: 1. With regard to the modal shape, there was almost no difference among the mandibles and each mandible with 6 types of mouthguard. 2. With regard to the damping ratio, there was a significant difference between the mandible itself and mandible with each mouthguard. And the effect of the mandible with each mouthguard on the damping ratio was different.

Biomechanical Phenomena↗
PubMedDate not supplied

[Chronic recurrent multifocal osteomyelitis of the mandible: report of three cases].

OBJECTIVE: To report three cases of chronic recurrent multifocal osteomyelitis of the mandible, an inflammatory disease affecting one or more bones with absence of isolated microorganisms in affected areas. DESCRIPTION: The first case is a 13 year-old female presenting with pain and fever after dental treatment. The patient received antibiotic treatment for osteomyelitis, but developed progressive enlargement of the mandible and palmoplantar pustulosis. Bone scintigraphy showed intense and diffuse uptake in the mandible. The swelling decreased after indomethacin and hyperbaric oxygen therapy. Case 2 is a 9 year-old female patient with recurrent pain and edema of the right mandible for three years. The diagnosis of osteomyelitis was established and amoxicillin introduced. After three months, tomography showed diffuse mandible osteolysis. Indomethacin and hyperbaric oxygen therapy were introduced, however the patient presented a relapse and was treated with prednisone, rofecoxib and methotrexate. Patient 3, a 10 year-old male, had palmoplantar pustulosis and recurrent enlargement of the mandible. Tomography showed diffuse mandible osteolysis and scintigraphy revealed intense and diffuse uptake in the mandible. The patient was treated with prednisone. Rofecoxib was replaced after two relapses. COMMENTS: Chronic recurrent multifocal osteomyelitis of the mandible is often associated with prolonged pain periods and periods of activity and remission of the inflammatory process. Its recognition is important to prevent the patient from being submitted to prolonged antibiotic therapy and unnecessary invasive procedures.

Adolescent↗
PubMed1997

The influence of the dentition on the shape of the mandible.

In the course of life the mandible undergoes substantial morphological and dimensional changes. The changes concerning mandibular angle, relation between the length of the mandibular corpus and ramus as well as roughness in the place of insertion of masseteric and pterygoid muscles do not depend upon age or sex but (apodictical) exclusively upon the dentition. In the complete dentition all masticatory muscles take part in chewing and grinding. The function of the temporal and masseter muscle is (reduced) weakened in partial or complete loss of teeth. The most evident morphological change of the lower jaw consists of an apparent elongation of its corpus resulting in a characteristic senile appearance. Measurements have been performed on 114 macerated mandibles of individuals ranging from 4 months to 68 years of age. The following measures have been taken: number of teeth in the lower jaw, angle between the corpus and ramus of mandible, length of the mandibular corpus, height of the mandibular ramus and angle of the mandibular incisure. The angle between the mandibular corpus and ramus is significantly lower in mandibles with 11 and more teeth (p < 0.001). The length of the mandible is significantly larger (p < 0.02) in mandibles with less than 11 teeth. The mandibular ramus is significantly higher in mandibles with more teeth (p < 0.01). There were no significant differences in the angle of the mandibular incisure within the groups (p > 0.05). The discriminant analysis reveals that 62.3% of the variability of mandibles is dependent upon the number of teeth. The rest of proportional variability of 37.7% is probably due to new circumstances and adjustment of the mandible in the period from tooth extraction.

Adolescent↗
PubMedDate not supplied

Paget's sarcoma of the mandible.

BACKGROUND: Sarcomatous change occurs in less than 1% of patients with Paget's disease. It has been reported in only 9 patients in the mandible, and has been uniformly fatal. Comparison of Paget's sarcoma of the mandible to osteosarcoma of the mandible and to osteosarcoma in other locations was made to attempt to explain and improve the outcome of patients with these tumors. METHODS: Two 78-year-old women with Paget's sarcoma of the mandible treated with radical resection are reported. The literature is reviewed to compare the clinical presentation and prognosis of patients with mandibular Paget's sarcoma to patients with osteosarcoma in non-Pagetoid mandibles and with osteosarcoma outside of the head and neck. RESULTS: Both patients died within 2 years of lung metastases. The patients with mandibular Paget's sarcoma were markedly older, with an average age of 65.6 years, compared to 32.5 years for mandibular osteosarcoma. Paget's sarcoma of the mandible was uniformly rapidly fatal; in non-Pagetoid mandibles the 5-year survival is 40%. There have been reports of only 7 patients who have survived with Paget's sarcoma in other locations. In osteosarcoma of the extremities 5-year disease-free survival exceeds 75% with multimodality therapy. CONCLUSIONS: Paget's sarcoma of the mandible is a rare tumor which affects elderly patients. It progresses rapidly and has a much poorer prognosis than osteosarcoma occurring in a non-Pagetoid mandible. The prognosis may be improved with early detection and treatment with multimodality therapy.

Adult↗
PubMed1999

The control of mandible movements in the ant Odontomachus.

Ants use their mandibles to manipulate many different objects including food, brood and nestmates. Different tasks require the modification of mandibular force and speed. Besides normal mandible movements the trap-jaw ant Odontomachus features a particularly fast mandible reflex during which both mandibles close synchronously within 3 ms. The mandibular muscles that govern mandible performance are controlled by four opener and eight closer motor neurons. During slow mandible movements different motor units can be activated successively, and fine tuning is assisted by co-activation of the antagonistic muscles. Fast and powerful movements are generated by the additional activation of two particular motor units which also contribute to the mandible strike. The trap-jaw reflex is triggered by a fast trigger muscle which is derived from the mandible closer. Intracellular recording reveals that trigger motor neurons can generate regular as well as particularly large postsynaptic potentials, which might be passively propagated over the short distance to the trigger muscle. The trigger motor neurons are dye-coupled and receive input from both sides of the body without delay, which ensures the synchronous release of both mandibles.

Journal Article↗