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PubMed1977

Biologic laws governing functions of muscles that move the mandible. Part III. Speed of closure--manipulation of the mandible.

The character of the occlusal surfaces of teeth programs the functions of muscles that move the mandible and imposes specifications upon the dentist within which he must work in manipulating the patient's mandible. If he exceeds those specifications, protective responses that inhibit his efforts are elicited in the patient's musculature. A knowledge of the laws governing functions of the muscles that move the mandible enables the dentist to acquire mandibular-manipulation skills necessary for diagnosis and effective occlusal treatment. A model in which the dentist visualizes the patient, the patient's protective reflexes, the components of the patient's gnathostomatic system, and himself as four independent personalities participating in the jaw manipulation is a useful tool in acquiring mandibular-manipulation skills. This article is Part III of a series presented in four parts on the "Biologic Laws Governing Functions of Muscles That Move the Mandible."

Biomechanical Phenomena↗
PubMed1976

The flared mandible sign of the flail mandible.

A useful radiographic finding is described for the diagnosis of a flail mandible. The flail mandible removes forward support for the tongue, which may result in airway obstruction. Immediate radiographic diagnosis allows quick surgical correction of the fractured mandible and relief of the obstruction, decreasing the time during which an endotracheal or tracheostomy tube is needed to keep the airway open.

Airway Obstruction↗
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↗
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↗
PubMed1976

[Functionally stable osteosynthesis of the mandible by means of an excentric-dynamic compression plate. Results of a follow-up of 25 cases].

The stability of internal fixation is enhanced by axial compression on the fracture ends. If internal fixation of the mandible is achieved by a compression plate at the lower border of the mandible (compression side), distraction of the fracture ends on the occlusal side occurs which has to be counteracted without damaging the roots of the teeth on the occlusal side (traction side) or without damaging the inferior alveolar nerve. From experiments on models it was seen that an acceptable solution to this problem is given by the use of the combined compression plate and tension band plate or the "Excentric Dynamic Compression Plate" (EDCP). In this paper 25 clinical cases of internal fixation of the mandible by means of the EDCP are examined and discussed. The following relevant facts were reviewed on all patients: -- kind of trauma -- age -- dentition -- localization of the fracture -- local and general additional injuries -- time of operation -- material used for internal fixation -- type of occlusal immobilisation during operation -- use of antibiotics -- skin closure -- mobilisation -- hospital stay -- duration of work disability -- complications -- scarring -- neurological disablement -- malocclusion In this paper emphasis is layed upon internal fixation by means of the EDCP. The clinical evaluation of the 25 cases clearly demonstrates that the main indication for internal fixation with the EDCP is given in fractures of the horizontal ramus of the mandible, because in this localisation the plate has to be applied beneath the inferior alveolar nerve. A further indication for internal fixation with the EDCP are fractures of the angle of the mandible. In these cases the tension band principle by means of a tension banc archbar or a tension band plate cannot be applied, because of missing teeth on the proximal fragment, or a non erupted wisdom tooth. These indications can be summarized as follows: -- In fractures of the angle of the mandible--when ever possible compression plate and tension band plate, otherwise EDCP -- In fractures of the horizontal ramus--EDCP -- In fractures of the mandibular front--DCP.

Bone Plates↗
PubMed1975

The human mandible: lever or link?

The mammalian mandible, and in particular the human mandible, is generally thought to function as a lever during biting. This notion, however, has not gone unchallenged. Various workers have suggested that the mandible does not function as a lever, and they base this proposition on essentially two assertions: (1) the resultant of the forces produced by the masticatory muscles always passes through the bite point; (2) the condylar neck and/or the temporomandibular joint is unsuited to withstand reaction forces during biting. A review of the electromyographic data and of the properties of the tissues of the temporomandibular joint do not support the non-lever hypothesis of mandibular function. In addition, an analysis of the strength of the condylar neck demonstrates that this structure is strong enough to withstand the expected reaction force during lever action. Ordinarily the human mandible and the forces that act upon it are analyzed solely in the lateral projection. Moments are then usually analyzed about the mandibular condyle; however, some workers have advocated taking moments about other points, e.g., the instantaneous center of rotation. Obviously it makes no difference as to what point is chosen since the moments about any point during equilibrium conditions are equal to zero. It is also useful to analyze the forces acting on the mandible in the frontal projection, particularly during unilateral biting. The electromyographic data suggest that during powerful unilateral molar biting the resultant adductor muscle force is passing between the bite point and the balancing (non-biting side) condyle. Therefore, in order for this system to be in equilibrium there must be a reaction force acting on the balancing condyle. This suggests that reaction forces are larger on the balancing side than on the working side, and possibly explains why individuals with a painful temporomandibular joint usually prefer to bite on the side of the diseased joint.

Biomechanical Phenomena↗
PubMed1976

The retrognathic mandible--surgical correction.

The preceding case reports demonstrate the excellent results available to the patient with a retrognathic mandible. Etiology, adverse effects, and the modalities used in evaluation of the underdeveloped mandible have been discussed. The age at which surgical intervention is undertaken needs additional input by clinicians. Several surgical procedures have been and are employed to advance the mandible. The C osteotomy is recommended since the final result has been excellent and consistent. The surgeon has constant surgical control and vision. The advanced portion of the mandible can be firmly held by intraosseous wires. There is minimak disturbance of muscle position and the inferior alveolar nerve. We have not encountered unusual loss of blood, immediate postoperative problems with the airway, infection, or unfavorable relapse. A postoperative regimen that has been found rewarding is discussed. We have come to the conclusion that most patients can tolerate lengthy surgical procedures with few adverse side effects. Our colleagues in anesthesia and nursing provide superb operative and postoperative care. When the preoperative work-up indicates that more than one procedure is indicated, we recommend that the total surgical treatment plan be carried through at one operation, although occasionally this approach may be contraindicated. We should strive for perfection and can fall short of this goal when a patient will not return for additional surgical procedures which could have been accomplished during the first operation. Although good results have been experienced with both the C osteotomy and the sagittal split osteotomy, we believe that the C osteotomy is a superior procedure. However, this does not imply that the sagittal split osteotomy should not be a part of the armamentarium of the oral surgeon. In conclusion, the C osteotomy, the sagittal split osteotomy, genioplasty, and additional procedures--such as a mandibular alveolar osteotomy to intrude supraerupted teeth--when indicated, can provide very favorable results in cases of retrognathia or micrognathia of the mandible.

Adolescent↗
PubMed1977

Effect of protein-energy malnutrition on the growth of mandible and long bone in newborn male and female rats.

Several parameters were measured in the growth centers of mandible and long bone of rat pups suckled on dams fed 25% or 6% protein diets. No sex-related differences were found in any parameter either during normal growth or in response to malnutrition. While the total contents of protein, DNA, RNA and calcium were reduced in both tissues, mandible was less affected than long bone, although it appeared to be affected earlier. Moreover, malnutrition reduced the number of cells in the mandible without changing cell size or calcium content. In contrast, long bone appeared to be affected later than mandible, and to be modified differently. In this case, not only cell number, but also cell size and cellular content of calcium were reduced. The results can be interpreted to mean that the critical periods of growth for mandible and long bone are different. Moreover, some suggestion of differences in relative sensitivity to malnutrition of these two hard tissues was also observed.

Age Factors↗
PubMed1979

Physical and biochemical changes of the mandible and long bone in protein-energy malnourished newborn rats.

The activities of alkaline and acid phosphatases, the linear dimensions and volumes of mandibles and long bones, and the level of calcitonin in serum of rat pups suckled on dams fed 25 or 6% protein diets were determined. In both mandibles and long bones, alkaline phosphatase activity corresponded to the calcification pattern, and acid phosphatase activity paralleled organic matrix formation. The calcitonin level in blood serum of the malnourished pups differed from that of controls only on day 5. The linear dimensions and volume were consistently more affected in long bones than in mandibles. These results may be explained in terms of the critical growth periods of these bones. In the mandible, the critical growth period appears to occur prenatally, whereas in the long bone it occurs postnatally, when the nutritional stress of this experiment was applied. Long bones were thus generally more affected than mandibles.

Acid Phosphatase↗
PubMed1975

[Bone statics of the face: the frontal-sphenoid-pterygoid bone pillars as biomechanic equivalents of the mandible].

In general biomechanics, trabecular osteo-architectonics is considered as a response to the mechanical strains present in the bone (compression or traction). The facial and cephalic skeleton is no exception to this law. The study of the bony architectionic provides the proof, since we have demonstrated in the fixed facial bone mass (at the limits of the facial skeleton and the skeleton of the base of the skull) the biomechanical equivalent of the mandible: the cranio-facial pterygo-spheno-frontal bony pillars. Paired, symmetrical and with a medio-frontal junction, they represent an embryological, anatomical and functional entity. Their ossification (mixed) may be compared to that of the mandible. They are made up of directional trabecular bone which may be analysed by stereology, electron microscope scanning and by strain gauges. Each pillar is made up of: - A part free of musculature corresponding to the supra-orbital frontal arch, which receives the four vertical pillars (naso-maxillary and maxillo-malo-frontal) of the superficial system of the face which transmit to the supra-orbital frontal arch the ascending mechanical strains of mastication registered in the spongy hard palate. The supra-orbital frontal arch is the biomechanical homologue in the fixed facial mass of the tooth bearing bony base of the mandible. - A spheno-pterygoid part, into which are inserted the alimentary muscles of the cephalic region (masticators, velar and superior pharyngeal). There is further functional homology between the ascending ramus of the mandible and the pterygoid greater wings and apophyses complex of the sphenoid. The 2 pterygo-spheno-frontal pillars also participate in the osseous statics of the orbit and the osseous statics of the temporo-mandibular joint. The basi-sphenoid plays a role of first importance in the general statics of the cephalic region. Thus the two pterygo-spheno-frontal pillars, biomechanical homologues of the mandible in the fixed facial mass, underline the functional interdependence of the osseous, dental and muscular systems of the cephalic region, a region which should be viewed as being in a stade of permanent dynamic equilibrium during growth and in the adult.

Biomechanical Phenomena↗
PubMed1978

Morbid changes of the mandible in familial polyposis of the colon.

The study was made to ascertain whether the radiographs of the mandible of patients with familial polyposis of the colon show osteomas. Orthopantomography of the mandible was taken in 10 cases of familial polyposis of the colon and 6 cases of the unaffected family members. And radiographic and histological studies were performed in another autopsied case. As a result, radiographic studies revealed sclerotic masses of the mandible in 10 of the 11 cases. In some cases, the changes were also found in the maxilla. The number of sclerotic masses ranged from 2 to 11, and they were associated with odontomas in 2 cases and impacted teeth in one case. Two of the 6 unaffected family members were found to have one or two sclerotic masses. At autopsy of a case died of cancer of the sigmoid colon, a radiographic study of the excised mandible revealed 11 sclerotic masses measuring 5 mm in diameter each, as well as one impacted tooth. A bucco-lingual cross action through the mandible in the canine area revealed central osteomas. Histological examination showed the osteomas were composed primarily of mature, lamellar bony tissue.

Adolescent↗
PubMedDate not supplied

[The phantom mandible].

The authors report a case of "phanton mandible" (phantom bone, disappearing bone, massive osteolysis affecting the mandible), describing the clinical colrse and radiological appearance of the condition. From a diagnosis of non-specific osteitis of the premolar region, they observed their patient until there was virtually total disappearance of the osseous structure of the mandible. Studying the world literature, they have collected 11 cases of the disorder involving the mandible, and, in some cases, the facial skeleton. They distinguish this condition from senile atrophy of the mandible and, after histological study, feel that it is not possible to classify this case in the context of Gorham's disease: in fact, haemangiomatosis was proved histologically in only three of the eleven cases described in the facial area.

Bone Diseases↗
PubMed1977

[The choice of a surgical method for the correction of sagittal over and under development of the mandible].

The experience gathered in the correction of sagittal mandibular over- and under-development allows to make the following conclusions:--In the choice of osteotomy it is necessary that careful consideration be given not only to the proportions of the body and ramus of the mandible, but also to the angular interrelationships of mandibular bones.--Osteotomies in the body of the mandible are indicated especially in those cases where it is only necessary for parallel shifts to be made in the sagittal plane.--Osteotomies performed in the region of the angle of the mandible and the ramus of the mandible (Obwegeser-Dal Pont) enable both longitudinal compensation or adjustment in the sagitta. plane and correction of transverse deformities and unfavorable angular relationships.--In the case of backward and forward displacement of the lower jaw it is essential that the position of the chin be considered already in the stage of planning the surgical operation. Suitable corrections can be made in the course of one surgical intervention.--Preliminary orthodontic treatment, because of the creation of optimum conditions of occlusion, will in many cases provide most favorable prerequisites of a surgical intervention.

Adult↗
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↗
PubMed1978

Experimental fractures of monkey mandibles.

Forty vervet monkey half mandibles, 20 with unerupted third molars and 20 with erupted third molars, were partially embedded in acrylic and loaded in an Instron tensiometer. Mandibles with unerupted third molars fractured at 15.8 +/- 2.5 kg while those having erupted third molars fractured at 26.4 +/- 4.2 kg. Mandibles having unerupted third molars were shown to be significantly weaker than the mandibles with erupted third molar (t = 8.45, P less than 0.001).

Animals↗
PubMed1977

In vivo bone strain in the mandible of Galago crassicaudatus.

Single element foil strain gages were bonded to mandibular cortical bone in eight specimens of Galago crassicaudatus. The gage was bonded below the Pm4 or M2 adjacent to the lower border of the mandible. The bonded strain gage was connected to form one arm of a Wheatstone bridge. Following recovery from the general anesthetic, the restrained Galago bit either a piece of wood, a food object, or a bite force transducer. During these biting episodes, mandibular bone strain deformed the strain gage and the resulting change in electrical resistance of the gage caused voltage changes across the Wheatstone bridge. These changes, directly proportional to the amount of bone strain along the gage site, were recovered by a strip chart recorder. Bone strain was measured on both the working and balancing sides of the jaws. Maximum values of bone strain and bite force were 435 microstrain (compression) and 8.2 kilograms respectively. During bending of the mandible, the correlation between bone strain (tension or compression) and bite force ranged from -0.893 (tension) to 0.997 (compression). The experiments reported here demonstrate that only a small percentage of the Galago bite force is due to balancing side muscle force during isometric unilateral molar biting. In addition, these experiments demonstrate that the Galago mandible is bent in a predictable manner during biting. The amount of apparent mandibular bone strain is dependent on (1) the magnitude of the bite force and (2) the position of the bite point.

Animals↗