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PubMed1999

Using restorations borne totally by anterior implants to preserve the edentulous mandible.

BACKGROUND: This study quantifies the changes in bone height of the posterior area of the edentulous mandible when the load of complete dentures is borne entirely by anteriorly placed osseointegrated implants. METHODS: Thirty-three patients, of whom there were radiographs from the beginning of implant loading and from a follow-up visit at least three years later (a mean of 6.6 years later), were included in the study. Working with panoramic radiographs, the authors took height measurements in the premolar area (15 millimeters distal to the most distal implants). A valid correction factor was available because implants of known length were proximal to the area being evaluated. RESULTS: The authors calculated descriptive statistics using means, standard deviations, medians and proportions as appropriate. A P-value of less than .05 was considered significant. Of the 33 subjects, most showed increases in bone height--29 (87.9 percent) on the right side and 28 (84.9 percent) on the left side. The mean change in all subjects was +1.0 mm (range -0.8 to +3.3 mm). A comparison of mandibular height at implant placement vs. follow-up showed a statistically significant increase bilaterally (P < .001). CONCLUSIONS: This study demonstrates that dentures for edentulous mandibles that are borne totally by implants in the anterior area conserve or enhance the bone of the posterior portion of the mandible. An important future study should test the effect of implant-assisted restorations for the edentulous mandible that load the posterior ridge (a bar clasp, for example). CLINICAL IMPLICATIONS: One of the considerations in planning treatment for the edentulous mandible should be the preserving effect of totally implant-borne restorations vs. the continued resorption of the body of the mandible with conventional dentures.

Adult↗
PubMed1996

Analysis of mandible of newly developing strain of Japanese white rabbit (Nib:JWNS).

In the present paper, we applied analysis of the mandible to a new strain of Japanese White rabbit being developed (Nib: JWNS), at 5th and 8th generations (F5 and F8), and evaluated the process of establishment, making comparison with the parent colonies (I, K and L), and other established JW colonies (A, E, O and R). The mandibles were measured at 12 sites and the data obtained were calculated by principal component analysis and discriminant analysis. As a result of principal component analysis, the parent colonies were found to be close to one another with intermediate size of the mandible and height of condyloid and angular processes, but in F5 and F8 the mandibles were slightly shorter in height and different from those in the parent colonies. On the other hand, results of discriminant analysis revealed that mandibles were discriminated correctly 100% in colonies A, O and R, and 90% in E and I. Colonies A, O, R, E and I were therefore regarded as established strains. In the developing colonies, the discriminant rate was 70% in F5 and 80% in F8. One mandible from F5 and two from F8 were wrongly classified to the parent colony L, which was the lowest discriminant rate among the colonies examined (61.5%). The results of both statistical analyses suggest that the JWNS are almost established at 8th generation as a new strain.

Animals↗
PubMed1994

Study of hereditary trends in the shape of the murine mandible.

Inbred mice are a suitable material for genetic studies, and mandibular shape in particular provides a highly quantitative hereditary trait. We investigated which genetic trait in F1, F2 and N2 hybrid mice was most strongly affected by the presence of a large or small mandible in the parents. Ten C57BL/6By strain mice as parents with a small mandible and 10 MRL/n strain mice as parents with a large mandible were employed. Twenty-five (C57BL/6By male X MRL/n female) F1 and 67 F2 hybrids, and 28 (F1 male X C57BL/6By female) N2 backcross hybrids were obtained by laboratory mating. The inter-landmarks of the right mandible were measured by an electronic digitizer. Each mean value of horizontal dimensions in F1 mice resembled that in MRL/l mice, and that in N2 mice was intermediate between C57BL/6By and MRL/n mice. On the other hand, the mean values of vertical dimensions in F1, F2 and N2 hybrids were intermediate between those of C57BL/6By and MRL/n mice. Hence we suggest that horizontal dimensions are predominantly inherited by mice with a large mandible, and that vertical dimensions show intermediate inheritance between mice with large and small mandibles in the C57BL/6By and MRL/n strains.

Animals↗
PubMedDate not supplied

The mandibular angles of dry adult human mandibles from north eastern arid zone of Nigeria.

OBJECTIVES: To study and document the mandibular angle of Nigerians from the north eastern arid zone, and investigate its role as an anthropological parameter for racial and or population groups differential diagnosis, its utilization in laryngoscopy and for successful inferior alveolar nerve anesthesia. DESIGN: A cross sectional study. SETTING: Department of Anatomy, College of Medical Sciences, University of Maiduguri, Maiduguri, Borno State, Nigeria. SUBJECTS: 60 dry adult mandibles from Nigerians who lived in Maiduguri (Borno State Capital) and its environ until their death. MAIN OUTCOME MEASURES: Measurements of the right and left mandibular angles, length and height of the mandibles and the comparison of the mean angle with that of other racial and or population groups. RESULTS: The mean mandibular angle (118.75 +/- 0.395 i.e. mean +/- SEM) was smaller than that of other African populations but was wider than that of the Neanderthals and similar to that of the Chinese and Peruvians. The mandible had a shorter ramus, slightly longer length resulting in a smaller angle than that of the Zimbabwean mandible. Highly significant differences occurred between the mean angle of the Nigerian mandible and those of other African population groups (p < 0.0001) except the mandibular angle of Natal Nguni and Cape Nguni populations from South Africa. There was no mutual dependence and no significant departure from linearity between the mean angle, length and height. CONCLUSION: The mandibular angle in conjunction with other anthropological parameters may be useful anthropological tools in racial and or population diagnosis. The configuration of the mandible of Nigerians from the northeast arid zone may predispose them to difficult laryngoscopy and/or intubation.

Adult↗
PubMed2001

[Relations of mechanical properties of human mandible to strain rate and density under tension load].

OBJECTIVE: To study the biomechanical properties of human mandible under tension load and deduce the constitutive equation. METHODS: 100 specimens taken from five mandible of fresh human cadavers were examined on INSTRON by a group of tensile tests at different strain rates (0.0003/s, 0.0030/s, 0.0300/s, 0.3000/s). Bone mineral density of every individual mandible was measured. The effect of strain rate (epsilon), bone mineral density (rho) on young modulus (E), strength (sigma u) and ultimate strain (epsilon u) was studied and the constitutive equation was deduced using the following model: Y = a rho b epsilon c. RESULTS: (1) sigma u = 126.36 rho 1.88 x epsilon 0.044 (P < 0.01), (2) E = 25,170.97 rho 0.44 x epsilon 0.052 (P < 0.01), (3) epsilon u = 0.0088 rho 1.89 x epsilon -0.028 (P < 0.01), (4) sigma u = 6,309.57 rho 0.96 epsilon 0.056 x epsilon 0.80 (P < 0.01). CONCLUSIONS: Strain rate and bone mineral density are important factors for the biomechanical properties of human mandible under tension load. The results above may modelize and characterize the constitutive relation within small strain rates. From the constitutive equation, we could estimate the stress level of the mandible and assess the possibility and degree of mandible injury.

Biomechanical Phenomena↗
PubMed2003

Effect of mandibular positioning on preimplant site measurement of the mandible in reformatted CT.

The purpose of this study was to evaluate the effect of mandibular positioning on measurement of the reformatted cross-sectional image of the mandible in computed tomography (CT) according to the area on the mandible. Five dried mandibles, partially edentulous in the premolar and molar areas, were selected. The inferior border of the mandible was placed at 0-, 5-, 10-, 15-, and 20-degree angles to the CT scanning plane, and CTs were taken. The marked area of the reformatted cross-sectional image taken at each angle was found, and the distance from the most superior border of the mandibular canal to the alveolar crest was measured. As the angle between the CT scanning plane and mandibular plane increased, the distance from the most superior border of the mandibular canal to the alveolar crest also increased. The degree of increase was more pronounced in the posterior portion of the mandible than in the anterior portion of the mandible. As mandibular positional change in the CT gantry can affect the vertical measurement of the reformatted cross-sectional image, a correct guiding plane is necessary to accurately position the jaw to the CT scanning plane.

Anatomy, Cross-Sectional↗
PubMed2003

[Department of a finite element model of the Head Model of HYBRID III Dummy with the Human Mandible].

OBJECTIVE: To analyze the biomechanics of impact injury in the condition of the simulate impact on mandible. METHODS: A finite element model of human mandible was developed from the CT scan images by the technologies of three-dimensional reconstruction, image processing and meshing. The mandible model was connected to a modified head model of HYBRID III dummy with joint according to the anatomic structure and mechanical characteristics of the temporomandibular joint. RESULTS: A finite element model of human head with true anatomic structure mandible has been developed. This model has been validated with the cadaver test results. The higher stress was showed in the condyle rejoins and coracoid in the model when mandible was in impact simulation. CONCLUSIONS: This model can be used to research the mechanism of craniofacial blunt-impact injury and assess the injury severity. The model of HYBRID III dummy with the human mandible was helpful for the boundary design of mandibular model in the impact simulations.

Biomechanical Phenomena↗
PubMed2005

[Effects of simulated weightlessness on rats mandible, lumbar vertebra and femur].

OBJECTIVE: To observe the effect of weightlessness simulation on rats mandible, lumbar vertebra and femur. METHOD: Twenty five Wistar rats were randomly arranged into control group (n=10) and tail-suspension group (n=15 rats). The experiment lasted for 28 d. Then the mandible, lumbar vertebra and femur were excised and the histological structure of condylar process of mandible, molar and premolar area of mandible body, first lumbar, head, middle segment and condyle of femur were examined. RESULT: After tail-suspension there was no distinct change in bone density and bone mass of condylar process. But the degree of interlacement of trabecular bone increased. The bone substance of mandible was very dense in both control and experimental groups. There was no stimulated difference of bone structure and bone mass between the two groups. There was no marked change in the thickness of periodontal membrane. The bone lamella in premolar area of experimental group arranged regularly. And its maturity was higher than that in molar area. The line of bone hyperplasia in molar area of experimental group arranged disorderly and irregularly, which means that much bone remodeling occurred. The component of trabecular bone decreased in femur and lumbar vertebra and the thickness was uneven. The interlacement and connection among trabecular bones was poor. CONCLUSION: Four weeks of stimulated weightlessness can lead to osteoporosis in acantha and femur [correction of feurar] but has no distinct effect on mandible.

Animals↗
PubMed1990

A precise radiographic method to determine the location of the inferior alveolar canal in the posterior edentulous mandible: implications for dental implants. Part 1: Technique.

In severely atrophic or osteoporotic mandibles, the location of the inferior alveolar nerve may vary considerably, both superoinferiorly and mediolaterally. A clinician's ability to reliably locate this nerve within the mandible would permit the surgical planning of implant placement in the posterior edentulous mandible. Eight edentulous cadaver mandibles were studied. A technique that precisely locates the inferior alveolar nerve within the mandible is described. The technique will aid the surgeon in planning a surgical approach to the posterior mandible with reduced risk of injury to the inferior alveolar nerve.

Adult↗
PubMed1989

[Stress-generated potential (SGP) on the surface of fluid-filled monkey mandible].

Previous studies have shown that stress generated potential (SGP) with bone deformation caused by orthopedic force have an important role in regulation on bone remodeling. The purpose of this study was to evaluate the effects of the chin cap on bone remodeling by elucidating the characteristics and distribution of SGP at various parts on the mandible. Experiment was carried out using a mandible of macaca irus monkey which was kept in moisture with 0.9% saline. SGP was recorded using Ag-AgCl electrode from the 32 sections on the surface of the mandible. The force (3 kg) was applied to the chin with six load conditions. It simulated the force generated by chin cap. Temporomandibular joints and the soft tissue except masseter muscle were kept intact. The results were summarized as follows. 1. SGP was generated only when the load was applied or removed. No SGP was generated when the load was steady, even the absolute value was large. 2. When the interval between "on" and "off" of the load was shorted, generated SGP with "off" timing decreased, while that with "on" timing unchanged. 3. When the load was applied in the low pull direction under the centric occlusion, rather larger negative SGP was recorded at the chin, posterior sections of mandibular body and inferior border of the mandible. 4. When jaw was in closing position, high pull loading generated larger SGP at the alveolar bone and the mandibular body than that with low pull loading, although their electric sign was the same at each recorded sections. 5. When jaw was in opening position, low pull loading generated larger SGP at the posterior parts of the alveolar bone and the mandibular body than that in closing position. 6. When a bite block was placed between the upper and lower teeth, larger amplitude in SGP was the evidence in all the recorded sections especially around the bite block. 7. SGP recorded at the posterior part of the mandible increased with the sliding of the location of the bite block towards posterior portion. 8. The electric sign and the amplitude in SGP and that of the stress analyzed by a finite element method were similar at the each sections on the mandible. This suggests SGP is related with the stress generated in the bone. The results suggested that effects of chin-cap on the bone remodeling might be dependent on the direction of the load, tooth contact, existence of bite block, and its location. Also dynamic loading was suggested to be more effective.

Animals↗
PubMed2001

Prenatal development of the human mandible.

In an effort to better understand the interrelationship of the growth and development pattern of the mandible and condyle, a sequential growth pattern of human mandibles in 38 embryos and 111 fetuses were examined by serial histological sections and soft X-ray views. The basic growth pattern of the mandibular body and condyle appeared in week 7 of fertilization. Histologically, the embryonal mandible originated from primary intramembranous ossification in the fibrous mesenchymal tissue around the Meckel cartilage. From this initial ossification, the ramifying trabecular bones developed forward, backward and upward, to form the symphysis, mandibular body, and coronoid process, respectively. We named this initial ossification site of embryonal mandible as the mandibular primary growth center (MdPGC). During week 8 of fertilization, the trabecular bone of the mandibular body grew rapidly to form muscular attachments to the masseter, temporalis, and pterygoid muscles. The mandible was then rapidly separated from the Meckel cartilage and formed a condyle blastema at the posterior end of linear mandibular trabeculae. The condyle blastema, attached to the upper part of pterygoid muscle, grew backward and upward and concurrent endochondral ossification resulted in the formation of the condyle. From week 14 of fertilization, the growth of conical structure of condyle became apparent on histological and radiological examinations. The mandibular body showed a conspicuous radiating trabecular growth pattern centered at the MdPGC, located around the apical area of deciduous first molar. The condyle growth showed characteristic conical structure and abundant hematopoietic tissue in the marrow. The growth of the proximal end of condyle was also approximated to the MdPGC on radiograms. Taken together, we hypothesized that the MdPGC has an important morphogenetic affect for the development of the human mandible, providing a growth center for the trabecular bone of mandibular body and also indicating the initial growth of endochondral ossification of the condyle.

Embryonic and Fetal Development↗
PubMedDate not supplied

Patterns of spread of squamous cell carcinoma within the mandible.

The patterns of spread of squamous cell carcinoma within the mandible were investigated in 43 nonirradiated (33 edentulous and 10 partially dentate) and 16 irradiated mandibles. Two modes of spread were identified: (1) spread in relation to the inferior alveolar nerve, and (2) spread in spaces between cancellous bony trabeculae. Although nerve-related spread was significantly more frequent in the edentulous than in the partially dentate nonirradiated mandible, the difference in incidence between all nonirradiated mandibles and irradiated mandibles was not significant. The patterns of spread in cancellous bone in irradiated and nonirradiated mandibles differed little. Spread of tumor within the medulla, deep to an intact cortex beyond the extent of extraosseous soft tissue tumor, was seen infrequently.

Carcinoma, Squamous Cell↗
PubMed1998

Assessment of tumour invasion into the mandible: the value of different imaging techniques.

In oral carcinomas close to the mandible, tumour invasion of the mandible is important in selecting segmental or marginal resection. Imaging may play a role in assessing tumour invasion. This study compares the accuracy of panoramic X-ray, CT and MR imaging in assessing invasion of the mandible in 29 patients. At histopathology, 6 patients had mandible erosion, 12 had invasion and 11 had an intact mandible. Magnetic resonance imaging had the highest sensitivity (94%), but a low specificity (73%), with 3 of 11 intact mandibles interpreted as positive. Furthermore, MR often overestimated the extent of tumour invasion. On the other hand, CT and panoramic X-ray had a lower sensitivity (64 and 63%, respectively) and a higher specificity (89 and 90%, respectively). Computed tomography (using 5-mm sections) and panoramic X-ray had a similar accuracy, and negative findings do not exclude invasion. Magnetic resonance imaging was the most sensitive technique but had more false positives and frequently overestimated the extent of tumour invasion. Because none of the radiological techniques are accurate enough, clinical examination seems at present to remain the most important modality in deciding between segmental and marginal resection. Tumour invasion at CT or panoramic X-ray is a strong argument for a segmental resection.

Adult↗
PubMed1997

Unicystic ameloblastoma of the mandible: a long-term follow-up.

PURPOSE: This article presents the long-term results of treatment for a series of unicystic ameloblastoma of the mandible. PATIENTS AND METHODS: Twenty-one patients were seen within a 15-year period. The median age at onset of symptoms was 18 years, with a median delay before presentation of 4 years. The male/female ratio was 1.3:1. Treatment was enucleation with primary closure in 11 patients (52.4%) whose lesions were in the horizontal body of the mandible. Five patients (23.8%) had excision of the lesion and the encompassing dentoalveolar process with preservation of the lower border of the mandible. Because the disease involved the ascending ramus of the mandible in five patients (23.8%), full-thickness resection of the affected mandible was done. RESULTS: There were three recurrences: Two in patients managed with enucleation and one in a patient who had resection of the lesion with preservation of the lower border of the mandible. CONCLUSION: The findings show that unicystic ameloblastoma often can be treated successfully with less aggressive surgery than that needed for multicystic ameloblastoma.

Adolescent↗
PubMed2002

Management of fractured mandibles without the use of intermaxillary wire fixation.

PURPOSE: The aims of this retrospective clinical study were to compare the management of unilateral angle fractures of the mandible using the traditional approach of open reduction with internal fixation (ORIF) and intermaxillary wire fixation (IMF) with the technique of ORIF without IMF. PATIENTS AND MATERIALS: Thirty-one patients who presented with isolated unilateral angle fractures of the mandible were randomly divided into 2 treatment groups. Both groups underwent open reduction with a single upper border miniplate and screw fixation (ORIF). Eleven of the 31 patients in the study had IMF to aid in the fracture reduction, and 20 patients had no IMF so the fracture was reduced by hand manipulation. Records of operating and discharge times, postreduction radiographs, and occlusal outcomes were examined and tabulated. RESULTS: Patients in both treatment groups were closely matched in terms of age, gender, site of injury (ie, isolated angle fracture of mandible), and incidence of teeth in the fracture line. The mean operating time for traditional ORIF with IMF of angle fractures of the mandible was 98.5 minutes, and these patients were discharged an average of 1.82 days after surgery. The mean operating time for ORIF of angle fractures of the mandible without the use of IMF was 40.2 minutes, and these patients were discharged an average of 1.35 days after surgery. Postoperative outcomes in terms of the postreduction anatomic alignment of the fractures and functional occlusion at 6 weeks were similar in the 2 treatment groups. CONCLUSIONS: We found that the use of IMF for the management of angle fractures of the mandible is unnecessary provided there is a skilled assistant present to help manually reduce the fracture site for plating. Discarding the use of IMF not only helps improve patient comfort but also reduces the operating time by up to 1 hour and accelerates discharge times by up to half a day.

Adolescent↗
PubMed2001

Treating chronic diffuse sclerosing osteomyelitis of the mandible with saucerization and autogenous bone grafting.

OBJECTIVE: Chronic diffuse sclerosing osteomyelitis of the mandible is a difficult-to-treat disease characterized by recurrent symptoms. The purpose of this study was to determine the results of particulate cancellous bone and marrow grafting after saucerization in the surgical treatment of diffuse sclerosing osteomyelitis of the mandible. STUDY DESIGN: Six patients with chronic diffuse sclerosing osteomyelitis of the mandible were treated by particulate cancellous bone and marrow grafting after saucerization and were retrospectively evaluated. Treatment results were evaluated with repeated comprehensive clinical investigation and radiologic/scintigraphic analysis. RESULTS: After the surgical procedure, all patients indicated maintenance of mandible continuity, contour, and function. Furthermore, 3 patients were symptom-free and the remaining 3 patients exhibited improvement. CONCLUSIONS: The partial resection of the mandible is associated with disadvantages, including loss of mandibular support, dysfunction, and problems related to mandibular reconstruction. Therefore, it would be reasonable to choose saucerization combined with particulate cancellous bone and marrow grafting, which is a relatively conservative surgical treatment for chronic diffuse sclerosing osteomyelitis of the mandible.

Adolescent↗
PubMed2001

Stafne's bone cavity in the anterior mandible: a possible diagnostic challenge.

Stafne was the first to report the presence of "bone cavities" in the angle of 35 mandibles. Such cavities generally appear in the area between the mandibular first molar and the mandibular angle, and are not considered rare. One of their primary radiological diagnostic features is the characteristic location below the mandibular canal. Stafne's bone cavity is relatively rare in the anterior mandible. The mandibular canal is not present in the anterior mandible. As a result, diagnosis in the anterior mandible may be missed. Needless treatment modalities such as endodontic treatment, bone trephining, and bone exploration may be conducted. The purpose of the present report is to describe a new case of Stafne's bone cavity in the anterior mandible and discuss the differential diagnosis process. The dental computerized tomography scan is suggested as the most suitable noninvasive diagnostic and follow-up modality for this bony configuration in the anterior mandible.

Diagnosis, Differential↗
PubMed2001

Injuries associated with mandible fractures sustained in motor vehicle collisions.

Motor vehicle collisions are second only to altercations as the most common cause of mandible fractures. This article details in a retrospectively studied group the incidence of isolated mandible fractures and associated injuries in patients who were involved in motor vehicle collisions. This group consisted of 148 patients with mandible fractures listed in the University of Mississippi's trauma registry during the past 5 years. In almost all patients, associated injuries occurred with mandible fractures that were caused by motor vehicle collisions, with an incidence of 99.3 percent. Facial and head lacerations and facial fractures were the leading associated injuries, occurring in more than half of the patients who had a mandible fracture. Closed head injury is the major life-threatening associated injury and cause of mortality. The life-threatening injuries occurred in 64.8 percent of patients in this study. The mortality rate in this group of patients was 8.1 percent. These data suggest that mandible fractures from motor vehicle collisions should never be viewed as an isolated injury but rather as part of a spectrum of significant and sometimes life-threatening injuries that require thorough trauma evaluation at the time of presentation.

Accidents, Traffic↗