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PubMed1977

Morphologic analysis of the "spina mentalis" in adult mandibles of Brazilian whites and negroes.

This study was carried out to verify the morphology of the spina mentalis. We observed 275 human adult mandibles of both sexes and ethnic groups. An analysis of the results allows the following conclusions: 1. The spina mentalis exists in 90.04% +/- 1.8 of the mandibles of Whites and Negroes; 2. The typical form with four tubercles, as described by some authors, is rarely found; 3. In most cases it characterized by the presence of two upper tubercles (27.27% +/- 7.2); two superior tubercles and one inferior (24.72% +/- 6.7), and one elongated median tubercle (24.0% +/- 6.6); 4. The forms and volumes of the tubercles are very irregular and seem not to depend on age, sex or ethnic group; 5. The spina was absent in 9.8% +/- 3.2 of the cases, especially in mandibles of White teethless individuals; 6. An hypertrophic spina mentalis, generally formed at the expenses of the upper tubercle, is observed in only 1.45% +/- 0.5 of the cases.

Black People↗
PubMed1983

[Osteogenesis of the rat mandible during development].

The author studied the mandibular osteogenesis process in Wistar rats during extrauterine development using macroscopic and microscopic investigations. Macroscopic investigations were carried out on rats aged 1, 5, 10, 20, 30 and 70 days, for establishing changes in the structure of the mandible and its elements, and autoradiographic determination of the sites of increased osteogenetic activity using Cr-51 chromium was obtained. Microscopic investigations were carried out in rats aged 1 and 5 days. The purpose of these investigations was a study of the morphological structure of the mandible, autoradiographic demonstration of the sites of increased cellular proliferation using 3H thymidine in rats aged 1 day, and osseous matrix formation in rats aged 1 and 5 days using 3H proline. The reported investigations showed that the periosteum and perichondrium were the source of mandibular bone formation. Proliferation of the cartilage of the condylar process and coronoid process occurs from the side of the perichondrium covering both these processes. This type of cartilage growth differs from the growth of the cartilage on the anterior part of mandibular corpus which showed additionally evidence of enchondral proliferation of cells. The process of osteogenesis was most active in the mandibular processes, anterior part of the mandibular corpus and the sites of attachments of muscles. This finding is explained as a result of function influence on the growing mandible. The results of macroscopic autoradiography performed with Cr-51 were confirmed by microscopic examinations.

Aging↗
PubMed1981

[A mechanical carrier for the functional load of the mandible (author's transl)].

An apparatus is described in which mandibles can be suspended according to natural conditions. The masticator muscles can be simulated so that static equilibrium is ensured between these muscles, the two joints, and a resting point corresponding to the site of the incisors. As far as this is possible direction and force of the simulated muscles are respected. The total force at site of the incisors is about 24 kg. Holes were perforated at chosen sites in the compact bone. The deformation of these holes produced by tension or compression in the compact bone was measured by a capacitive transducer. In the 8 mandibles measured, tension characterized the pars alveolaris, compression the inferior edge of the corpus mandibulae. The highest values (tensions) were observed at the angular mandibulae (superior edge) and the lowest at the inferior edge of the protuberantia mentalis. Three mandibles were fractured and reconstructed with osteo-synthesis-plates. The load of 24 kg were applied at a rate of 1 to 2 per sec for approx. 15 min. The dislocation of the bony fragments produced by these loads oscillated between 19 and 47 micrometer. Repeated application of the load never produced a systematic increase of the displacement. The sites of measurement did not always show the displacement that might have been expected.

Biomechanical Phenomena↗
PubMed1982

[Application of a 3-dimensional model using computer technology in the study of the structure of the mandible].

Previous studies employing a plane "model" on the hemi-mandible confirmed the concept of a "bees-nest" structure of the mandible. As this plane model did not permit demonstration of maximal zones of iso-stress in the horizontal rami, the whole mandible was examined by means of a three-dimensional model. This gave more precise information, and thus produced more realistic results confirming previous findings. This new reliable type of model can be employed for any such exploratory procedure, and in studies totally different from those for which it was developed.

Humans↗
PubMed1978

The adaptive mandible: a product of the relative osteo-neural growth.

The growth interrelation existing between the developing brain and its bony case (with the brain representing the morphogenetically determining structure to the shape and size of which the neurocranial bony envelope is adapted) is to be conceived just as a special case of a general phenomenon, the osteo-neural relation, which works throughout the entire vertebrate body. The morphological manifestations of this relation may be disclosed in the axial as well as in the appendicular skeleton. In the present communication the osteo-neural concept is applied to the morphogenesis of the facial skeleton with special reference to the mandible. The more or less elongated shape of the mandible in various species of vertebrates depends on the phylogenetically established higher or lesser degree of growth potentiality of the mandibular nerve. With the increasing size of the brain in the course of hominization the growth-in-length capability of the mandibular nerve is (compensatorily?) decreased with corresponding shortening of the mandible and with appearance of the chin. The proposed interpretation is supported by a model experiment. The highly characteristic shortening and angulation of the lower beak which may be produced experimentally in the chick embryo by a great variety of teratogens, is related most probably to the same underlying mechanism, viz., to the primary inhibition of the highly susceptible neural growth with the secondary adaptive deformity of the beak. Pierre-Robin-Syndrome (cleft palate and micrognathia) may be readily explained by a growth insufficiency of the palatine and mandibular nerves.

Animals↗
PubMed1995

Constrained and unconstrained postures of the mandible--a break with tradition?

Evaluation of detailed electrognathographic recordings of various movements of the mandible (and points on it) suggested interpretations at variance with some traditional concepts. Data previously accumulated from several sources were subjected to critical analysis. An objective was to assess the manner in which two rotations of the mandible influenced its postures during trials of mastication and deliberate lateral excursions. Rotations about a vertical and an antero-posterior axis appear to facilitate a greater functional posturing potential of the mandible than has previously been reported. In most instances the influence of the rotations upon mandibular posture is considerably greater than the size of the recorded angles would suggest. Some of the resulting postures seem to challenge concepts derived strictly from cadaverine anatomy. For example, during mastication the condyle does not simply glide forward and backward relative to the eminence but may be distracted downward away from it for a part of the time. Furthermore, the ability of a subject to effect a considerable variety of mandibular postures challenges traditional reliance upon constrained mandibular movements as a means of evaluating function.

Humans↗
PubMed1995

A review of 60 consecutive fibula free flap mandible reconstructions.

Sixty consecutive fibula free flap mandible reconstructions were performed for oncologic defects. Patient age averaged 46.7 years. Eighty-one percent were primary reconstructions. Sixty-two percent were lateral defects; 22 percent were anterior; and the remainder had combined defects. The bone gap averaged 9.4 cm. A skin island was included with the fibula in 85 percent of patients but was actually needed in only 62 percent. Miniplate fixation was used in 96 percent. Templates derived from radiographic studies were used as an aid in shaping the fibula. Average anesthesia time was 14.54 hours; the transfusion requirement, 3 units; and hospitalization, 22 days. Fifty-nine flaps were successfully transferred. Ninety percent of skin islands raised were completely viable. Average postoperative interincisal opening was 35.2 mm. Osseointegrated implants were placed in 56 percent of suitable candidates, and all implants integrated into bone. Aesthetic results were usually good when the soft tissue defect was limited, but poor when it was extensive. Donor site morbidity was usually mild and transient. The most significant problem was delayed healing in patients closed with a skin graft. Postoperatively, all patients ambulated normally, and none used assist devices. Reoperation for donor site problems was rare. The fibula has many assets that together make it an ideal choice for the reconstruction of most mandible defects. The skin island is usually reliable if it is designed and raised properly. Donor site morbidity is largely inconsequential. The primary contraindication to the use of the fibula for mandible reconstruction is severe peripheral vascular disease.

Adolescent↗
PubMedDate not supplied

Anatomical considerations relevant to implant procedures in the mandible.

The authors review anatomical facts significant for preoperative planning of implant procedures in the mandible. This planning includes the precise evaluation of distinct anatomical factors, such as the position of the mandibular canal, the width of the mandibular cortical plates and the degree of involutive changes of the inferior dental artery. The mandibular canal is usually situated centrally in the mandibular corpus, slightly closer to the lingual cortex in its distal parts; towards the front, it approaches the vestibular cortical layer. Mesially from the mental foramen, a clearly defined incisive canal is present in only one third of the edentate mandibles. Mandibular corpus of the edentate mandibles consists of cancellous bone enclosed by a shell of compact cortical bone. Cortical layers demonstrate significant variations in width; nevertheless, the widths of lateral cortical layers, generally, enable safe placement of endosseous implants. Finally, in patient's preoperative assessment, involutive changes of the inferior dental artery should also be considered. During the involution of the mandibular alveolar process, it shows changes of direction and calibre, changes in arborization and, sometimes, complete occlusion of the main trunk. The degree of these involutive changes points out the mandibular vascular supply and the regenerative capacity of the tissues needed for the success of the implant procedure.

Dental Implantation, Endosseous↗
PubMedDate not supplied

A three-dimensional finite element study on two versus four implants in an edentulous mandible.

The difference in stress distribution in the bone around dental implants was determined under conditions where either two or four implants were placed in the interforaminal region of the mandible. The purpose was also to determine the influence of the height of the mandible on the stress distribution. The stress distribution around the implants was investigated using three-dimensional finite element models of the interforaminal region of two mandibles with two different stages of resorption. It was concluded that there is no reduction of the extreme principal stresses when the load is distributed over an increasing number of implants. There is a tendency for a gradual stress increase as mandibular height decreases.

Alveolar Bone Loss↗
PubMed1994

The mandibular lingual foramen: a consistent arterial foramen in the middle of the mandible.

The lingual foramen in the midline of the mandible causes confusion in terminology, incidence of occurrence and contents. A survey of 314 dried mandibles showed the foramen to be present in 311 specimens (99.04%). Sectioning of cadaver specimens illustrated a canal traversing the bone to approximately 50% of the buccolingual dimension of the mandible. The contents of the foramen were found to be an artery, which was an anastomosis of the sublingual branches of the right and left lingual arteries. Wire markers were placed in the foramen and the genial tubercles were covered with lead foil to illustrate the radiographic relationship between them. The radio-opacity peripheral to the foramen as seen on a radiograph is produced by the wall of the canal and not the genial tubercles as previously reported. While the foramen is not seen on many radiographs of the lower incisor region, this can be accounted for by a change in orientation of the x-ray beam. A pilot study revealed an incidence of 49% of the lingual foramen on periapical radiographs of the mandibular incisor region in an adult population, the previous reported incidence being 28%.

Arteries↗
PubMedDate not supplied

[An analysis of isometric reflections in morphology exemplified by the mandible of the rat (Rattus, Rodentia)].

Individual, age, sex, and species differences of morphological shape is treated as a result of general shape formation process. It is assumed that mutual reflections of these differences could be described by continuous and discontinuous transformations. The first type of these reflects equilibrium properties of shape formation, while the second type reflects its non-equilibrium properties. Equilibrium process is strongly canalized and is able to generate quite limited diversity of shapes. Contrary to this, non-equilibrium process can generate a lot of different shapes, as it destroys canalized relations between characters. Idea of equilibrium process provides a background for formulation of null hypothesis about anticipated relations between characters. Statistically significant deviations from these relations allow to recognize characters that mark areas of possibly non-equilibrium transformations. Analysis of localizations of all such characters allows to formulate more meaningful hypothesis about shape transformations for a particular morphological object. Some easily available statistical methods of recognizing characters that reflect either continuous of discontinuous transformations are exposed using mandible of three rat species as an example. It is shown that discontinuous transformations are located mainly in the same areas of mandible in all modes of inter-reflections. Characters (linear measurements between morphometric landmarks) with continuous inter-reflections describe transformations of general shape of the mandible. Characters with discontinuous inter-reflections mark boundaries between functional blocks and areas with the heaviest dynamic loads.

Aging↗
PubMed1994

The edentulous mandible opposed by natural maxillary teeth: a report of six cases treated with implant-retained prostheses.

Dental restoration of the edentulous mandible opposing natural maxillary teeth is often associated with a number of problems, particularly in the occlusion, and an accelerated rate of alveolar bone resorption in the edentulous mandible resulting from occlusal loading. The advent of osseointegrated implants would seem to provide a new means of treating these cases. Accordingly, the cases of six patients for whom either fixed partial dentures or over-dentures supported by Brånemark implants were provided, are reviewed. Three of the mandibles were normal and three had bone grafts. Results so far indicate that this is a viable alternative for treating such cases.

Dental Implantation, Endosseous↗
PubMed1993

[An observation of the effects of rat's condylar cartilage after application of retractive force on the mandible].

The changes of histologic structure and matrix secreting of rat's condylar cartilage after application of upward retractive force to the mandible were investigated by means of histology and histochemistry. After the force application, the condylar cartilage became thinner, the amount of the cells in the germ zone decreased, and that in the transition and transform zone were extremely or even disappeared. Sometimes a calcification zone was discovered in the cartilage and some cells of the mature zone were embed in it. The amount of acid mucopolysaccharide in the matrix also decreased. The result indicated that the retractive force inhibited the proliferation and differentiation of condylar cartilage remarkedly. This was the mainly morphologic bases of the shorted mandible which as a result of the retractive force applied to the mandible.

Animals↗
PubMed1993

Evaluation of the caudoventral portion of the mandible as a donor site for corticocancellous bone for periodontal surgery in dogs.

Corticocancellous bone graft was obtained from the caudoventral portion of the mandible of 8 dogs. The recipient site was an alveolar jugal and alveolar defect from vital root amputation of the mesiobuccal root of the maxillary fourth premolar. Anatomic observations of 20 canine cadavers indicated that guidelines for harvesting bone from the caudoventral portion of the mandible of dogs were the mesial aspect of the masseteric fossa, the distal aspect of the roots of the first mandibular molar, and the ventral aspect of the mandibular canal. The mean weight of corticocancellous bone harvested was 0.4 +/- 0.1 g. Harvested corticocancellous bone was adequate to fill recipient sites measuring a mean volume of 105.0 +/- 28.5 mm3. Histologic evaluation of the recipient site revealed progressive osseous integration of the bone-graft site during a mean follow-up period of 3.5 +/- 1.9 months. There was normal bone healing of the donor site without adverse effects on the mandibular molars or neurovascular structures of the mandibular canal. Vital amputation sites receiving silver amalgam had evidence of plasmacytic/lymphocytic inflammation associated with residual silver amalgam in the bone-graft area. The caudoventral portion of the mandible may be used as a donor site for autogenous corticocancellous bone in periodontal surgery of dogs.

Animals↗
PubMed1995

Linear unsharp mask filtering of linear cross-sectional tomograms of the posterior mandible.

Linear unsharp mask filtering is a digital image processing technique which can enhance diagnostic information by subtracting from the original image the linear blur which was formed in the direction of the linear tomographic movement. It was applied to linear cross-sectional tomograms of the posterior mandible aiming at retrieving cross-sectional outline information. This study demonstrated that the current Orthophos Program 16 with a 6.72 degrees tomographic angle does not provide accurate cross-sectional outline information of the posterior mandible. Linear unsharp mask filtering of these images also failed to provide more information. A larger tomographic angle of 10 degrees was employed with the Polytome to simulate the modified Program 16 with a wider beam. The resulting tomographic images showed better defined cross-sectional outlines, and after the linear unsharp mask filtering, the outlines were more readily retrieved. In order to get cross-sectional outline information of the posterior mandible, the tomographic angle of the Orthophos program 16 should be increased to more than 10 degrees which can be achieved by increasing the width of the x-ray beam.

Aged↗
PubMed1995

[Evaluation of the usefulness of autogenic bone grafts in reconstruction of the mandible].

The treatment of reconstructions of mandible by means of autogenic bone graft in 64 patients has been presented (Fig. 1). In 55 cases the bone material was taken from the iliac crest, in 5--the skin-muscle flap, in 4--the free bone graft from VIII rib and tibial bones. The resection in 47 patients was performed because of malignant neoplasms, in 4 cases--oral and mandibular benign neoplasms, in 3 cases a part of the mandible was resected because of the osteodystrophy, in 3 cases due to osteoradionecrosis, in 3 cases--congenital anomalies, in 2 cases because of a cyst, while in other 2--after an injury. Clinical parameters were evaluated: cosmesis, mastication, deglutition, diet, speech, and the use of dentures. The positive result was obtained in 84% cases. Cosmesis was improved in patients who had immediate restoration of mandibular reconstruction due to previous scarring. Mastication was poorer in the reconstructed group due to scarring, loss of the muscles of mastication, and inhibition of compensation of mandibular motion. Deglutition was not improved in patients who had mandibular continuity resorbed. Problems with deglutition were related to soft tissue resection. Speech and prosthetic rehabilitation was poor in both groups in patients. In 5% of patients, there was a slight extraoral graft denudation and the development of organic inflammatory process in the surrounding tissues and the graft itself. Application of the appropriate pharmacological and local treatments was sufficient for the maintenance of the graft and its normal healing. Negative result of the mandible reconstruction was observed in 11% of cases. In the patients with immediate reconstruction, more than 50% of the bone grafts resorbed.

Adult↗
PubMed1996

Site of the mandible prone to trauma: a two year retrospective study.

The objectives of this retrospective study were to determine the most common site of trauma to the mandible observed at an urban centre. The study, completed at the Manchester Royal Infirmary UK, comprised patients presenting with mandibular fractures in the calendar years 1991 and 1992. A total of 147 fractures were seen in 96 patients, with the majority of patients being males in the age group 20-29 years who sustained injury due to interpersonal assault. The pattern of injury was mostly unilateral due to low velocity impact and the site of the mandible that was most vulnerable to trauma was the angle of the mandible.

Accidental Falls↗
PubMed1997

[A case of basilar impression treated with mandible splitting transoral approach].

We report a case of basilar impression treated with mandible splitting transoral approach surgery. A 39-year-old man presented a ten-year history of gait disturbance. He had experienced acceleration of his spastic paraparesis for the past few years. Neurological examination on admission demonstrated tetraparesis (MMT4/5), severe hyperreflexia in his arms and legs, severe sensory loss below C2, urinary retention and inability to open his mouth widely. Radiological findings showed the dens and the body of C2 are deeply invaginated to the atlas and the foramen magnum and medulla and upper cervical cord were markedly compressed by this basilar invagination. After carrying out posterior decompression and occipito-cervical fixation, we attempted to remove the invaginated dens and the C2 vertebral body using a conventional transoral approach. But limitation of mouth opening made operative fields narrow. Consequently because of insufficient anterior decompression his neurological deficits could not be alleviated. Employment of mandible splitting procedure brought about a wide operative view so that complete removal of the residual dens and 70% drilling out of the C2 body was made possible. Postoperative complications were negligible. Finally, great alleviation of his deficits was achieved. Mandible splitting procedure is effective for obtaining a wide operative field on the anterior approach to the craniocervical junction.

Adult↗