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At least 181 records · Page 10Linked to original sources
PubMed2005

The identification of mandible fractures by helical computed tomography and panorex tomography.

The introduction of computed tomography (CT) in 1972 revolutionized the radiographic evaluation of patients who have experienced trauma. However, panoramic tomography (PT) continued to be superior in sensitivity to CT in the identification of mandible fractures and has been considered the gold standard for the past 3 decades. In 1989, a faster, higher-resolution spiral or helical CT (HCT) became widely available, and its efficacy in multiplanar evaluation and diagnosis of fractures of the upper two thirds of the face has been well established. The sensitivity of this new-generation HCT in comparison to PT in the detection of mandible fractures has not been determined. The purpose of this study was to compare the sensitivity, physician interpretation error, and interphysician agreement of HCT and PT in the identification of mandible fractures. The number and anatomical location of mandible fractures identified by HCT and PT was not significantly different. However, the number and location of 96% of fractures identified by HCT was agreed on by neuroradiologists compared with only 91% of fractures identified by PT. Furthermore, the interphysician agreement when no fracture was identified was 96% by HCT versus only 81% by PT. In conclusion, HCT has enhanced imaging quality, equivalent sensitivity in identification of fractures, decreased interpretation error, and greater interphysician agreement in the identification of mandible fractures. HCT has surpassed PT as the current gold standard for the radiographic evaluation and diagnosis of mandible fractures.

Humans↗
PubMed2003

Early function of splinted implants in maxillas and posterior mandibles using Brånemark system machined-surface implants: an 18-month prospective clinical multicenter study.

BACKGROUND: There are limited clinical data available for immediately or early loaded implants placed in posterior mandibles and maxillas. This is probably because bone density often is low in these areas, making it difficult to establish good initial implant stability. By eliminating countersinking and using slightly tapered implants (Brånemark System , Mk IV, Nobel Biocare AB, Gothenburg, Sweden), however, high initial implant stability might be achieved in these regions. PURPOSE: The aim of this study was to investigate the possibility of early application of implant function in oral locations where the bone density is often low, namely the maxilla and posterior mandible. MATERIALS AND METHODS: Thirty-one patients were included consecutively in the study, and 36 edentulous areas in maxillas and posterior mandibles were treated. All patients were nonsmokers in good general health. Bruxism and uncontrolled periodontal disease were exclusion criteria. One hundred twenty-four machined-surface implants were placed using an insertion torque of at least 40 Ncm. Temporary prostheses with narrow occlusal platforms, flat cusps, and light occlusal contacts were generally placed within 1 week and not exceeding 20 days from implant placement. RESULTS: Of the 124 implants installed, 4 failed, 1 in each of four patients, giving an overall survival rate of 96.8% after 18 months. Two implants failed in maxillas and two in mandibles. One implant in a maxilla and one in a mandible were lost in an early stage, and the other two were lost a few months after placement. The prostheses' survival was 100%. CONCLUSIONS: This study shows that early implant function rehabilitation in maxillas and posterior mandibles is viable using the present clinical protocol. The results are comparable with those of conventional two-stage protocols.

Adult↗
PubMed2006

[Functional recovery with prosthetic management for segmental resection of the mandible without reconstruction].

PATIENT: The patient, a 54-year-old male, consulted the Oral Surgery Department of Iwate Medical University Hospital with a complaint of a mass in the left oral base in June 1992. In September 1992, the patient was diagnosed as having cancer in the left mandibular base, and the tumor was excised by resection of the entire cervical region on the left side. Since radiation osteonecrosis in the left mandible and mandibular fracture were detected, segmental excision of the left mandible was performed in March 1993. Although the postoperative course was good without reconstruction, the patient consulted the Second Prosthetic Department to achieve functional recovery in February 1996. This patient had no occlusal contact between the maxilla and mandible because the mandible shifted to the affected side. After fixation of a mandibular prosthetic appliance for the defective mandible, a palatal plate for the maxilla in occlusal contact with the mandibular dentition and mandibular prosthetic appliance were fixed in November 1997. After fixation of a new mandibular prosthetic appliance and dentures for the maxilla with palatal ramp in April 2001, masticatory function was observed to have improved with control of the mandible. DISCUSSION: To prevent the mandibular shift and improvement of the masticatory function, a palatal plate with a palatal ramp in the occlusal contact region was fixed, and a balance of the masticatory muscles could be maintained. An evaluation of the level of improvement in the masticatory function and the pronunciation function indicated that the mandibular prosthetic appliance and palatal plate with a palatal ramp in the occlusal contact region increased the kind of food that the patient could take. Moreover, by enlarging the narrow Donders space, the pronunciation was improved. CONCLUSIONS: Fixation of a palatal plate with a palatal ramp in the occlusal contact region without reconstruction of the mandibular bone was useful for the control of mandibular deviation to the affected side and improvement of the masticatory function.

Dental Prosthesis↗
PubMed1984

Effects of caffeine on the growth of mandible and long bone in protein-energy malnourished newborn rats.

Rat dams with eight pups each were divided into six groups upon delivery; the first three were fed 6, 12 or 20% protein diets, and the second three the same diets but with caffeine added in the amount of 2 mg/100 g body wt. At Day 15, randomly selected pups were injected with [14C]proline to determine collagen synthesis of mandible and long bone. Other pups were used to determine the calcium content of these bones. The body, mandibular, and long bone weight of the pups whose dams were fed the 6% protein diet with caffeine increased compared to the noncaffeine group. Calcium content of the mandible and the collagen synthesis of the long bone were also increased. However, calcium content of long bone, collagen synthesis of mandible, and hydroxyproline content of mandible and long bone showed no difference between the caffeine and noncaffeine groups. In the pups whose dams were fed the 12% protein diet with caffeine, body and mandibular weight, collagen synthesis, and hydroxyproline and calcium contents in mandibles and long bones of pups showed no difference from those of the noncaffeine group, but long bones were heavier. In the pups whose dams were fed the 20% protein diet with caffeine, the body and long bone weight and hydroxyproline and calcium contents of the long bone of pups were lower than those of the noncaffeine group. Mandibular weight, calcium content, and hydroxyproline showed no difference between caffeine and noncaffeine animals, but collagen synthesis of the mandible was increased. Current data indicate that nutritional state and caffeine intake of the mother have a close relation to growth and development of the offspring.

Animals↗
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↗
PubMed2001

[A study of the magnification of mandible pantomography image].

OBJECTIVE: To study the degree of magnification of mandible pantomography image. METHODS: The pantomography of 50 mandible specimens marked with lead pellets were taken by TROPHY XL-90C. The distances between each markers on film and in specimen were measured. RESULTS: The mean magnification(MM) of mandible pantomography image with TROPHY XL-90C was 1.22. MM of horizontal axle was 1.14. MM of vertical axle was 1.29. MM of horizontal axle was greatest (1.24) in the body of mandible,and lest (1.08) in genion. MM of vertical axle is similar among each regions. MM of vertical axle was greater than that of horizontal axle in all regions. CONCLUSION: The MM parameters of mandible pantomography image were useful to estimate the size of mandible lesions and provided a basis for dental implant more exactly.

English Abstract↗
PubMed1997

Resection and immediate microvascular reconstruction in the management of osteoradionecrosis of the mandible.

BACKGROUND: Management of osteoradionecrosis (ORN) remains a difficult and challenging problem. The traditional approach using debridement, antibiotics, and occasionally hyperbaric oxygen is usually successful in treating minimal ORN. However, when bone and soft-tissue necrosis is extensive, the conservative approach usually requires intensive care over a long period of time and often yields unsatisfactory functional and cosmetic results. METHODS: Within the past 5 years, we have used radical resection of the mandible with immediate microvascular reconstruction in the treatment of extensive ORN of the mandible. This aggressive surgical approach was used in six patients with advanced ORN of the mandible, all of whom had failed initial conservative treatment, including hyperbaric oxygen therapy in three. A fibular free graft with microvascular anastomosis was used in all patients. RESULTS: All the patients healed primarily with minimal postoperative morbidity and excellent cosmetic results. Two patients subsequently required removal of some of their hardware. One patient had placement of osseointegrated implants with an excellent cosmetic and functional result. CONCLUSION: Microvascular reconstruction with its own blood supply seems to expedite bone healing and limit further osteoradionecrosis of the remaining mandible. Although prevention is the primary goal in radiation injury, our experience suggests that radical resection with free microvascular reconstruction offers significant advantages to selected patients with extensive ORN of the mandible.

Dental Implantation, Endosseous↗
PubMed2000

Serial homology of the mandible and maxilla in the jumping bristletail Pedetontus unimaculatus Machida, based on external embryology (Hexapoda: Archaeognatha, Machilidae).

The development of the mandible and maxilla is examined with the scanning electron microscope in the Archaeognatha. Serial homology is discussed to elucidate the general construction of the hexapod mandible. The part comparable to the maxillary palp does not develop in the mandible. Thus, the mandible is coxopodal in origin, and not telognathic but coxognathic. The mandible proper is subdivided into two in late embryonic development, and the smaller proximal and larger distal parts are homologized with the maxillary cardo and stipes, respectively, being subcoxal and coxal in nature. The partition into the "mandibular cardo" in which the mandibular monocondyle is formed and the "mandibular stipes" is recognized as a cuticular ridge or the "mandibular basal ridge" in the postembryonic stages including the imaginal. The molar and incisor are comparable in position and homologized with the maxillary lacinia and galea, respectively. The lacinia and galea could be morphologically interpreted as being the endites of the maxillary coxae I and II, respectively, and the molar and incisor might represent the mandibular coxae I and II as their constituents or endites.

Animals↗
PubMed2003

Variations in cortical material properties throughout the human dentate mandible.

Material properties and their variations in individual bone organs are important for understanding bone adaptation and quality at a tissue level, and are essential for accurate mechanical models. Yet material property variations have received little systematic study. Like all other material property studies in individual bone organs, studies of the human mandible are limited by a low number of both specimens and sampled regions. The aims of this study were to determine: 1) regional variability in mandibular material properties, 2) the effect of this variability on the modeling of mandibular function, and 3) the relationship of this variability to mandibular structure and function. We removed 31 samples on both facial and lingual cortices of 10 fresh adult dentate mandibles, measured cortical thickness and density, determined the directions of maximum stiffness with a pulse transmission ultrasonic technique, and calculated elastic properties from measured ultrasonic velocities. Results showed that each of these elastic properties in the dentate human mandible demonstrates unique regional variation. The direction of maximum stiffness was near parallel to the occlusal plane within the corpus. On the facial ramus, the direction of maximum stiffness was more vertically oriented. Several sites in the mandible did not show a consistent direction of maximum stiffness among specimens, although all specimens exhibited significant orthotropy. Mandibular cortical thickness varied significantly (P < 0.001) between sites, and decreased from 3.7 mm (SD = 0.9) anteriorly to 1.4 mm posteriorly (SD = 0.1). The cortical plate was also significantly thicker (P < 0.003) on the facial side than on the lingual side. Bone was 50-100% stiffer in the longitudinal direction (E(3), 20-30 GPa) than in the circumferential or tangential directions (E(2) or E(1); P < 0.001). The results suggest that material properties and directional variations have an important impact on mandibular mechanics. The accuracy of stresses calculated from strains and average material properties varies regionally, depending on variations in the direction of maximum stiffness and anisotropy. Stresses in some parts of the mandible can be more accurately calculated than in other regions. Limited evidence suggests that the orientations and anisotropies of cortical elastic properties correspond with features of cortical bone microstructure, although the relationship with functional stresses and strains is not clear.

Aged↗
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↗
PubMedDate not supplied

Preoperative evaluation of the mandible in patients with carcinoma of the floor of mouth.

Preoperative evaluation of the mandible for invasion by tumor has always been a difficult problem. Various methods have been used, including clinical evaluation, panoramic x-rays, dental films, routine mandible films, bone scans, computed tomographic (CT) scans, and magnetic resonance imaging (MRI) scans. The diagnostic accuracy of these methods has not been totally satisfactory from the clinical standpoint. We compared the diagnostic effectiveness of clinical evaluation, panorex films, and CT scans in 60 patients with carcinoma of the floor of mouth. The relative value of these tests was studied in relation to marginal or segmental mandibulectomy. Our data showed that CT scanning was not very helpful, mainly because of the presence of irregular dental sockets and artifacts. Clinical evaluation was the most accurate, both to determine bone invasion and to decide the type of mandibular resection necessary in association with the primary tumor. Panoramic films were helpful in evaluating the gross extent of mandibular invasion. However, they were not of any help in determining minimal bony invasion or cortical invasion. Even though CT scanning has made a tremendous impact in other areas of head and neck surgery, it is not of much help in making the critical decisions in the type of mandible resection, marginal or segmental, in patients with carcinoma of the floor of mouth. Our experience demonstrates that clinical evaluation is superior in preoperative evaluation of the mandible, and especially in deciding the type of mandible resection.

False Negative Reactions↗
PubMed1995

Maxillary molar extraction causes increased bone loss in the mandible of ovariectomized rats.

Although osteoporosis is a major public health concern, its effect on oral bone has not been determined. More important may be the effect of estrogen depletion on the response of oral bone to dental treatments such as tooth extraction or pathologic processes such as periodontal disease. Our objective was to determine if maxillary molar extraction increases mandibular bone loss in the ovariectomized compared with a sham-operated control. Fifty-three ovariectomized and 53 sham-operated 6-month-old Sprague-Dawley rats were randomly assigned to the following groups: (1) ovariectomized, adult; (2) sham-operated, adult; (3) ovariectomized, adult, extraction; (4) sham-operated, adult, extraction; (5) ovariectomized, old; (6) sham-operated, old; (7) ovariectomized, old, extraction; and (8) sham-operated, old, extraction. Fourteen days following ovariectomy, the extraction groups had their bilateral maxillary molars extracted. The adult and old rats were sacrificed 114 and 200 days postovariectomy, respectively. The right mandible was tested to failure in three point bending. The bone mineral density (BMD) of the left mandible was measured with high resolution dual energy X-ray absorptiometry. The area fraction and area moment of inertia of mandible sections were determined using image processing software. In the ovariectomized rats, maxillary molar extraction resulted in decreases (p < 0.05) in the failure load (21%), stiffness (39%), BMD (3%), and bone area fraction (8%) of the mandible. However, in the sham-operated rats, these decreases following maxillary molar extraction were less (p < 0.05) than those in the ovariectomized rats and only present in the mandibles of the aged rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed2001

Mandible reconstruction and autogenous frozen bone graft: experimental study on rats.

The aim of this study was to evaluate the biological behaviour of a frozen bone graft in orthotopic and heterotopic sites in the rat. The previous experimental study on this subject was published 25 years ago without sufficient detail about the histology and comparison between the orthotopic and ectopic sites. Therefore, being very important for future clinical application, we decided to evaluate the frozen bone graft using rats. The procedure was performed on two groups of five rats each (Charles River). After wide dissection of the inferior border of the mandible from the surrounding muscle, an inferior segmental resection 4 mm in length was performed, taking care not to fracture the superior part and to maintain mucosal integrity. This segment was placed in liquid nitrogen for two periods of 10 minutes each with a third period to allow it to reach room temperature. In the first group (A), the frozen segment was placed ectopically in a gluteal muscle pocket, and in the second group (B), the frozen bone was fixed in the same position in the same mandible. After 1 month of follow-up, the animals were killed, the bone graft was removed, and histology was performed. Results were consistent in both groups. In group A, the segment was surrounded by strong inflammatory reaction, with no vital cells or bone cells, but some vascular penetration. We concluded that there was no bone deposition and no bone rehabitation. In group B, the initial segment was strongly fixed to the remaining mandible, there was an increase of the macroscopic dimension that paralleled the increase in the dimension of the remaining mandible and the growth of the animal. The cortical part had thinned down, the medullary part presented signs of bone deposition as well as bone resorption and vascular penetration. The periosteum from the adjacent normal mandible was growing and covering the frozen bone graft, offering additional stimulus to the bone deposition. In conclusion, the frozen bone graft acts as a normal bone graft. It needs to be placed in contact with vascularised bone and surrounded by well vascularised soft tissue to allow deposition of new bone. If the frozen graft is placed ectopically, it will be surrounded by chronic inflammatory reaction with no bone deposition.

Animals↗
PubMed1985

Study of the mandible under static constraints by holographic interferometry. New biomechanical deductions.

In order to try to determine the nature of the mechanical structure of the mandible, the authors have compared, with the help of holographic interferometry, the behavior of the fresh mandible of a corpse, of a representative iron angle, and of a block of carbon-carbon under static constraint. There are no similarities between the behavior of the human mandible and that of a polycrystalline steel. On the contrary, the behavior of the mandible and of the carbon-carbon block are very similar. It would be hasty to state that bones are a heterogeneous composite. We can only prove, in a first approach, that they behave similarly under identical experimental conditions. The authors also demonstrated that the mandible presents a "mechanical hysteresis" phenomenon. This means that, when subjected to a small strain, its shape changes, but this change tends to neutralize itself in part in the course of time.

Aged↗
PubMed1988

Bone mineral content of mandibles: normal reference values--rate of age-related bone loss.

The purpose was to obtain the normal sex- and age-related reference values for the bone mineral content (BMC) in the bones of the mandible and the forearms, as estimated by dual-photon absorptiometry; to examine the effect of tooth loss on the mandibular BMC, i.e., BMC in the basal part of the mandible; and to analyze the rate of the sex- and age-related BMC loss in the mandible in normal old edentulous individuals greater than or equal to 70 years of age and its relationship to the corresponding BMC loss in the forearm bones. The following groups were measured: young dentate adults (n = 100; women (W): men (M) = 1:1), young, long-term edentulous W (n =15), and old edentulous individuals (n = 24 W, 10 M). In the old group the BMC measurements were repeated after 2- or 3-year period (n = 18 W, 10 M). The analyses indicate that the mandibular BMC reference values differ by sex and age; but correction for the state of dentition seems of minimal benefit. The average BMC loss (%) in the bones of the mandible and the forearms seems to be higher in old W (1.5 and 1.4% per year) than in old M (0.9 and 0.7% per year), but of the same magnitude in each sex. The relationship between the BMC loss (%) in the two sites was significant (P less than 0.01) but rather weak. Thus, it seems important to follow the sex- and age-related BMC loss in the mandible separately.

Adult↗
PubMed2000

Expression of major bone extracellular matrix proteins during embryonic osteogenesis in rat mandibles.

It is not known how bone proteins appear in the matrix before and after calcification during embryonic osteogenesis. The present study was designed to investigate expressions of the five major bone extracellular matrix proteins--i.e. type I collagen, osteonectin, osteopontin, bone sialoprotein and osteocalcin--during osteogenesis in rat embryonic mandibles immunohistochemically, and their involvement in calcification demonstrated by von Kossa staining. Wistar rat embryos 14 to 18 days post coitum were used. Osteogenesis was not seen in 14-day rat embryonic mandibles. Type I collagen was localized in the uncalcifed bone matrix in 15-day mandibles, where no other bone proteins showed immunoreactivity. Osteonectin, osteopontin, bone sialoprotein and osteocalcin appeared almost simultaneously in the calcified bone matrix of 16-day mandibles and accumulated continuously in 18-day mandibles. The present study suggested that type I collagen constitutes the basic framework of the bone matrix upon which the noncollagenous proteins are oriented to lead to calcification, whereas the noncollagenous proteins are deposited simultaneously by osteoblasts and are involved in calcification cooperatively.

Animals↗
PubMedDate not supplied

Three-dimensional mandible reduction: correction of occlusal class I in skeletal class III cases.

BACKGROUND: The human face is a three-dimensional structure. However, many studies on mandible reduction procedures are based on a two-dimensional concept, with a particular focus on one dimension: the width of the lower face. Many Korean individuals have class I occlusion with a skeletal class III pattern. When a conventional mandible reduction procedure is used on such individuals to reduce the width of the lower face, an unsatisfactory facial outcome may result because the changes in the other two dimensions of the lower face, vertical height and anteroposterior distance, are disregarded. This is true because the skeleton of the lower face is well developed in all three dimensions. METHODS: Bimaxillary surgery that reduces all three dimensions of the lower face was planned and conducted by the authors. This mandible reduction procedure reduced the protrusion of both the maxilla and the mandible and, at the same time, shortened the lower face height. The procedure consisted of a Le Fort I osteotomy for superior and/or posterior repositioning of the maxilla, followed by mandibular counterclockwise rotation and setback via a bilateral sagittal split osteotomy. Genioplasty was performed as necessary. RESULTS: With this procedure, the entire lower face volume is reduced, and the overall profile is improved. CONCLUSIONS: Three-dimensional mandible reduction greatly enhances the aesthetic outcome by improving the skeletal characteristics of the face common in the Korean population so that the facial measurements more closely approach normal values.

Adult↗
PubMed2000

Variations in the pattern of mental spines and spinous mental foramina in dry adult human mandibles.

The frequency and morphology of mental spines and spinous mental foramina was studied in 1200 adult human mandibles of Indian origin. The mental spines were present in 1178 mandibles (98.2%). The usual textbook description of four spines, arranged in two pairs one above the other was found only in 231 mandibles (19.6%). Mandibles with only two superior mental spines were seen in 842 cases (71.4%) which were associated with either a median vertical ridge below them (47.7%) or with a rough impression in place of the median ridge (23.7%). Spinous mental foramina (one to three) close to the midline and in between the spines were found in 1165 mandibles (97.57%). The presence of these foramina has not been mentioned in most textbooks of anatomy.

Adult↗