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At least 127 records · Page 7Linked to original sources
PubMed2003

Evaluation of lingual vascular canals of the mandible with Computed Tomography.

PURPOSE: To assess the anatomy of the mandibular lingual vascular canals with the use of computed tomography (CT). MATERIALS AND METHODS: Seventy consecutive patients underwent preimplantation CT of the mandible. CT images were obtained on axial plane by using a bone reconstruction algorithm and then processed with dedicated software (Dentascan). The number of lingual vascular canals, the diameter of their entrance foramina and the distance of the foramina from the symphysis menti and from the lower edge of the mandible were measured in each patient. The median superior canal (MSC), the median inferior canal (MIC), the lateral mesial canals (LMC) and the lateral distal canals (LDC) were evaluated separately. RESULTS: 0 to 5 canals were found in each patient. The MSC was found to be present in 98.6% of cases; the mean diameter of the entrance foramen was 0.85+/-0.28 mm located adjacent the symphysis menti and 11.3+/-2.6 mm from the inferior margin of the mandible. The MIC was found to be present in 32.9% of cases; the mean diameter of the entrance foramen was 0.58+/-0.21 mm located adjacent the symphysis menti and 5.5+/-2.2 mm from the inferior margin of the mandible. LMCs were found to be present in 38.6% of cases; the mean diameter of their entrance foramina was 0.60+/-0.24 mm located 5.1+/-2.5 mm from the symphysis menti and 6.3+/-3.2 mm from the inferior margin of the mandible. LDCs were found to be present in 48.6% of the patients; the mean diameter of their entrance foramina was 0.58+/-0.19 mm located 19.3+/-7.3 mm from the symphysis menti and 6.6+/-5.4 mm from the inferior margin of mandible. CONCLUSIONS: Dental CT detects the lingual vascular canals of the mandible in a high percentage of subjects and allows a good demonstration of their number, location and entrance foramen diameter. The evaluation of these canals is important in the preoperative planning of dental implants or in the planning of dental surgery in general so as to avoid bleeding due to damage of the vessels present in these canals.

Adolescent↗
PubMed2005

[Research methods in dentistry 9. Follow-up of permucosal implants in an edentate mandible using panoramic radiography].

Panoramic radiographs are frequently used for routine follow-up of mandibular implants. The objective of this study was to determine whether measurement on a panoramic radiograph of the vertical dimension of the mandible near by an implant, using the known implant length as a reference, is a reliable method. In 11 patients, 2 permucosal implants were placed in the anterior part of the edentulous mandible. During the first year after implantation, 2 panoramic radiographs and 2 sets of standardized oblique lateral cephalometric radiographs were made. Oblique lateral cephalometric radiographs are the golden standard for measuring the vertical dimension of an edentulous mandible. The length of the implants and the vertical dimension of the mandible dorsally to the implants were measured on all oblique lateral cephalometric radiographs. The measured and known implant length were used to calculate the image enlargement factor. This factor was used to calculate the real vertical dimension of the mandible. The same measurement procedures were performed on the panoramic radiographs. Using a paired t-test, the calculated values of the vertical dimensions of the mandibles found on panoramic radiographs were compared with the calculated values found on oblique lateral cephalometric radiographs. No statistically significant differences were found. It was concluded that under the described circumstances, panoramic radiographs can be used for reliable measurement of the vertical dimension of the mandible near by permucosal implants.

Cephalometry↗
PubMed2005

[Value of multislice spiral CT scanning and three-dimensional reconstruction in selecting optimal length and shape of mandible internal fixation material].

OBJECTIVE: To investigate the value of multislice spiral CT (MSCT) scanning and three-dimensional reconstruction in selecting optimal length and shape of mandible internal fixation material. METHODS: Three-dimensional reconstruction of the mandible was performed in 5 cases by MSCT scanning and the length of the mandible for operation was measured. Some isometric points were chosen on the mandibular curve and the distance from these points to the two ends of the curve was measured to depict the mandibular curve using a self-designed skeletal curve-depicting software. The optimal length and shape of the material for internal fixation was then determined. RESULTS: After removal of the soft tissues and other irrelevant bones from the reconstructed three-dimensional mandible with clear view from any directions, the length of the mandible was accurately measured with the software. The physiological curve of the mandible was generated after determination of the distances from the chosen points on the mandibular curve and to the two ends of the curve for precise determination of the length and shape of the material for internal fixation. CONCLUSION: Three-dimensional mandible reconstruction with MSCT and measurement facilitates the determination of the optimal length and shape of the internal fixation material to enhance the attachment between the material and the bone surface and consequently the therapeutic effects.

Adolescent↗
PubMed2005

Phylogenetic and environmental components of morphological variation: skull, mandible, and molar shape in marmots (Marmota, Rodentia).

The phenotype is a product of its phylogenetic history and its recent adaptation to local environments, but the relative importance of the two factors is controversial. We assessed the effects of diet, habitat, elevation, temperature, precipitation, body size, and mtDNA genetic divergence on shape variation in skulls, mandibles, and molars, structures that differ in their genetic and functional control. We asked whether these structures have adapted to environment to the same extent and whether they retain the same amount of phylogenetic signal. We studied these traits in intra- and interspecific populations of Eurasian marmots whose last common ancestor lived 2-5 million years ago. Path Analysis revealed that body size explained 10% of variation in skulls, 7% in mandibles, and 15% in molars. Local vegetation explained 7% of variation in skulls, 11% in mandibles, and 12% in molars. Dietary category explained 25% of variation in skulls, 11% in mandibles, and 9% in molars. Cyt b mtDNA divergence (phylogeny) explained 15% of variation in skulls, 7% in mandibles, and 5% in molars. Despite the percentages of phylogenetic variance, maximum-likelihood trees based on molar and skull shape recovered most phylogenetic groupings correctly, but mandible shape did not. The good performance of molars and skulls was probably due to different factors. Skulls are genetically and functionally more complicated than teeth, and they had more mathematically independent components of variation (5-6-in skulls compared to 3-in molars). The high proportion of diet-related variance was not enough to mask the phylogenetic signal. Molars had fewer independent components, but they also have less ecophenotypic variation and evolve more slowly, giving each component a proportionally stronger phylogenetic signal. Molars require larger samples for each operational taxonomic unit than the other structures because the proportion of within-taxon to between-taxon variation was higher. Good phylogenetic signal in quantitative skeletal morphology is likely to be found only when the taxa have a common ancestry no older than hundreds of thousands or millions of years (1% to 10% mtDNA divergence)--under these conditions skulls and molars provide stronger signal than mandibles.

Animals↗
PubMed1990

[A study of the internal structure of the Japanese edentulous mandible].

With the aim of improving understanding of the transition the mandible internal structure undergoes between the dentulous and edentulous states, the thickness of the substantia compacta, the ratio of trabecular bone to the total substantia spongiosa, and the thickness of the trabecular bone were measured in 9 edentulous mandibles aged 45 to 65 years. The measurements were made with an image-treatment device outfitted with a personal computer. Results 1. Thickness of the substantia compacta The thickest zones (3.00-3.81 mm) were located on the lingual side of the anterior teeth; the second thickest zones (2.20-2.48 mm) were located on the superior lingual and buccal side of the molars. The thinnest zones (1.66-1.67 mm) were located on the labial side of the anterior teeth; the second thinnest zones (1.71-1.75 mm) were located on the buccal side of the premolars. Little difference (1.90-2.18 mm) was observed in the bases of the mandibular areas. In the region of the lingual side, the thickest zones occurred in the premolars. Little difference in thickness was observed between the premolar and molar zones. On the labial-buccal side, thicknesses increased from the premolar to the molar zones (which were the thickest) and decreased gradually from the mental to the premolar zones. Comparisons showed that the anterior teeth zoon in the edentulous mandible the substantia compacta is thinner on the labial side and thicker on the lingual side than it is in the dentulous mandible. Little difference between the dentulous and edentulous mandibles was observed in the lingual side of the molar zone, although the buccal side was thinner in the edentulous than in the dentulous mandible. 2. Ratio of trabecular bone to the total substantia spongiosa The highest ratios (74.03-89.62%) occurred in the mental zone; the second highest (69.07-82.92%) occurred in the incisor zone. The lowest ratios (30.61-39.61%) occurred in the superior and middle regions of the premolar zone. The inferior area of the premolar zone, however, was relatively wider (42.83-55.66%) than the superior and middle areas. The following ratios of trabecular bone to total substantia spongiosa were observed: The highest ratio occurred in the zone of the anterior teeth, the next highest ratio in the molar zone, and the lowest ratio in the premolar zone. Although, differences in ratios between dentulous and edentulous mandibles were only slight, a lower ratio occurred in the inferior area of the premolar zone. 3. Thickness of trabecular bone within the substantia spongiosa.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1982

[General partial resection of the mandible in para-osteal cancers of the mouth and oropharynx].

The mandibles of 24 patients with a squamous cell carcinoma of the floor of the mouth or the tongue or the tonsils (all were T2N1b and T3N1b), were histologically examined. It could histologically be shown, that the bone will be destroyed by 2 modalities: 1. Atrophy of the mandible, caused by the pressure of the tumor, leaving the periosteum intact 2. Infiltration of the tumor into the bone. Tumor cells could not be found in the lymphatic system of the periosteum. Since the periosteum is a barrier against tumor growth, the indicator for the resection of the mandible was made after shaved off the periosteum. Resulting from our findings we propose the following concept: 1. If the tumor reaches the mandible (distance tumor to bone = 0 mm) or is fixed to the periosteum and the compacta shows no errosion, after shaving off the periosteum, the mandible can be preserved. 2. If the tumor grows through the periosteum, a marginal resection of the mandible is necessary. 3. If the bone shows errosion, a partial resection of the anterior part of the mandible or a hemimandibulectomy is indicated.

Carcinoma, Squamous Cell↗
PubMed2004

The correlation between mandible fractures and loss of consciousness.

PURPOSE: The purpose of the study was to evaluate the relationship between mandible fractures and loss of consciousness (LOC) in patients sustaining maxillofacial trauma in a level I trauma center. PATIENTS AND METHODS: The study was a retrospective chart review performed at Lincoln Medical and Mental Health Center, a level I trauma center. A total of 225 hospital charts of patients who sustained mandible fractures during the period from 1997 to 2001 were reviewed. The site of fracture, number of fractures per mandible, degree of displacement, and mechanism of injury were recorded. Percentages of each category were compared among patients with positive and negative LOC. Patients with any concomitant craniofacial fractures or injuries were excluded from the study. RESULTS: The incidence of LOC in patients sustaining mandible fractures was 17.6%. Young men were most likely to sustain mandibular fractures. The male-to-female ratio was 5.6:1. More than 70% of mandible fractures were due to interpersonal violence. Among various causes of interpersonal violence, use of a fist was most common. Overall, the number of fractures per patient, the incidence of singular versus multiple mandibular fractures, and the degree of displacement were less in the group with positive LOC. Body and angle regions were subjected to higher numbers of fractures, with slight variation among the 2 groups. The most common locations for mandibular fractures were the body (26% in negative LOC group; 42% in positive LOC group) and the angle (31% in negative LOC group; 26% in positive LOC group). CONCLUSION: Nearly 1 in 5 mandible fractures was associated with positive LOC. The patient group with a positive LOC, on average, sustained fewer fractures. It is possible that when the mandible sustained fewer fractures, the dissipation of energy was reduced and more force was transmitted to the cranial vault, thereby resulting in a higher incidence of LOC.

Adolescent↗
PubMed2003

Treatment of fractures of the mandible and maxilla by mini titanium plate fixation systems in dogs and cats.

Mini titanium plates were used to repair certain fractures of the maxilla and mandible in dogs and cats, under general anaesthesia. The location of the fractures treated were: corpus mandible, one dog; corpus mandible and symphysis, two dogs; caudal mandible, two dogs; rostral mandible, one dog; maxilla, one dog; nasal bone, one dog; corpus mandible and symphysis, one cat; caudal mandible, one cat; and maxilla, one cat. The healing periods varied from 6 to 9 weeks. In seven cases, implants were removed after a period of 3.5 to 18 months. In four cases the implants were left in place. The follow up period was between 8 and 36 months. In ten cases the procedure was successful, however in one case the outcome was not satisfactory due to a broken plate. There were no instances of dental malocclusion, nonunion, malunion, osteomyelitis or soft tissue infection. Eating, playing with toys, a fast transition to solid food and a quick return to normal jaw movements were observed. In our hands, the mini titanium plate fixation system was a safe and effective method for repairing certain maxillary and mandibular fractures in dogs and cats.

Animals↗
PubMed1994

Maxillary molar extraction decreases stiffness of the mandible in ovariectomized rats.

Although osteoporosis is a major public health concern, the effect of this condition on oral bone has not been determined. Using the ovariectomized rat as a model, we examined whether acute estrogen depletion affects the mandible of the ovariectomized rat with and without maxillary molar extraction. Twenty-two ovariectomized and 20 sham-ovariectomized 90-day-old Sprague-Dawley rats were divided into the following groups: (1) sham-ovariectomized, baseline control; (2) ovariectomized, baseline control; (3) ovariectomized; (4) ovariectomized, tooth extraction; (5) sham-ovariectomized; and (6) sham-ovariectomized, tooth extraction. On day eight, sham-ovariectomized and ovariectomized rats had all their maxillary molars extracted, and the baseline control sham-ovariectomized and ovariectomized rats were killed. On day 35, the remaining animals were killed. After teeth were harvested, the right mandible was tested to failure in three-point bending. The bone mineral density of the left mandible was measured with dual-energy x-ray absorptiometry. The area fraction and area moment of inertia of a section of mandible were determined. Neither ovariectomy nor tooth extraction significantly affected the bone mineral density or structural properties of the rat mandible. However, there was an interaction between ovariectomy and maxillary molar extraction on the stiffness of the rat mandible (p < 0.008). Maxillary molar extraction decreased the stiffness of the mandible by 25% (p < 0.05) in the ovariectomized rat, whereas it did not do so in the sham-ovariectomized rat.

Alveolar Bone Loss↗
PubMed2005

[Epidemiological profile of mandible fractures treated at the Federal University of São Paulo-Paulista Medical School].

BACKGROUND: Mandible fractures can result in esthetic, functional and financial problems and their epidemiological patterns have changed in many locations. This study was carried out to detect these changes, aiming to compare data of patients with mandible fractures treated at the Sao Paulo Hospital (UNIFESP-EPM) from June 1999 to March 2002 with data of patients treated from January 1991 to March 1996. METHODS: Information on most affected gender and age, most often fractured mandible segment, associated injuries, treatment and complications of 98 victims of mandible fracture admitted from June 1999 to March 2002 were compared to the same data of 166 patients treated from January 1991 to March 1996. RESULTS: the most affected gender and age ranges remain the same. Aggressions surpassed traffic accidents as the main etiology. Incidence of associated injuries and multiple fractures in the mandible decreased, a fact probably related to the change in etiology. The most affected segment is still the body of the mandible. The most used type of treatment in both samples was internal rigid fixation with miniplates and the number of complications decreased, due to the higher standard of patient care. CONCLUSION: Mandible fractures in the São Paulo population have undergone epidemiological changes and this knowledge enables local authorities to establish adequate measures for prevention and treatment.

Accidents, Traffic↗
PubMed1999

[Effect of unilateral condylar fracture on stress distribution in the mandible].

OBJECTIVE: To investigate the effect of unilateral condylar fracture on stress distribution in the mandible in order to realize primarily the biomechanical mechanism of temporomandibular joint disorders (TMD) resulted in by joint injury. METHODS: The stress distributions in the mandible of a normal human and a patient with TMD induced by right condylar fracture following malposition healing were analyzed and compared quantitatively during centric occlusion by three-dimensional finite element method. RESULTS: The patient contained the unbalanced stress distribution in the mandible, such as different nature and value of stress. The stress in the fractured side was higher than the non-fractured side, in which condyle is more evident. The maximum principal stress and minimum principal stress of each region in his mandible were much higher than that in a normal mandible. Its stress quality changes also. The stress in his mandible was distributed asymmetrically. CONCLUSION: Unilateral condylar fracture not only damaged its structure, but also induced the badness of its biomechanical environment, in which condyle was the most sensitive region during the stresses in the mandible were changed. It was preliminarily thought that unbalanced stress distribution, evidently increased stress and varied stress character were one of biomechanical mechanism of TMD.

Adult↗
PubMed1991

Mandible reconstruction with vascularized bone grafts. A histologic evaluation.

To our knowledge, a histologic evaluation of bone healing after mandible reconstruction with vascularized human bone grafts has not been previously reported. Serial sections through both the decalcified graft and the junction between mandible and graft were evaluated in four patients who required surgical removal of their reconstructed mandibles. A failed scapular bone graft that had been wrapped within a pectoralis major myocutaneous flap for salvage following pedicle thrombosis showed markedly resorbed but viable bone with a fibrous union to the native mandible. Viable vascularized grafts without evidence of ongoing resorption characterized an iliac osteocutaneous bone graft and two scapula osteocutaneous grafts that healed with continuity of healthy bone between graft and mandible. Observations from the evaluation of these specimens are made regarding bone circulation, bone union, and bone graft survival as they occur clinically. Implications regarding the techniques of bone plating and indications for use of vascularized bone in mandible reconstruction are discussed.

Bone Transplantation↗
PubMed2004

Intrabony course of the inferior alveolar nerve in the edentulous mandible.

The purpose of this study was to investigate the vertical positioning and intrabony branching patterns of the inferior alveolar nerve (IAN) in 39 edentulous human cadaveric mandibles by buccal microdissection. Dissected mandibles were classified on the basis of the height of the IAN within the body of the mandible and the branching pattern of the IAN. The IAN was located in the superior part of the body of the mandible in 30.7% (12/39) of cases, all of which showed a small posterior molar plexus of branches. In 69.2% (27/39) of cases the IAN was half-way or closer to the inferior border of the mandible. Of these latter cases, 41% demonstrated a small, posterior molar plexus of branches, 37% showed posterior and anterior plexuses, and 22% showed either no branches or a single trunk with a small number of single branches directed at the superior border of the mandible. These findings were rendered in 3D computer format for instructional purposes.

Aged↗
PubMed2005

Metastatic adenocarcinoma of the colon presenting as a mass in the mandible.

BACKGROUND: Metastatic adenocarcinoma of the colon is a frequently encountered medical situation. Metastasis to the mandible from adenocarcinoma of the colon is very unusual and rarely reported. We report the case of a 73-year-old man with metastatic adenocarcinoma to the mandible. METHODS: The patient was referred for evaluation of a mass of 2 months' duration in the right parotid gland. He gave a history of watery bowel movements of unknown duration. Physical examination revealed a 7- x 6-cm hard mass, which seemed to be fixed to the right mandible. A CT scan revealed a destructive process involving the ramus and condyle of the right mandible that invaded the pterygopalatine fossa, pterygoid muscles, and middle cranial fossa. CT scans of the abdomen and pelvis revealed a 5-cm mass in the sigmoid colon with metastases to the liver. RESULTS: A biopsy of the mass in the mandible was performed, and metastatic adenocarcinoma of colonic origin was diagnosed. Colonoscopy and biopsy of the colonic mass substantiated that the sigmoid colon was the primary site of the cancer. Because the patient had disseminated disease, he declined treatment, and he died shortly thereafter. CONCLUSIONS: Although rare, metastatic adenocarcinoma from the colon to the mandible and parotid area should be included in the differential diagnosis of masses in this area. After analysis of our case and a review of the literature, we conclude that metastasis from adenocarcinoma of the colon is quite rare and represents incurable disseminated disease.

Adenocarcinoma↗
PubMed1994

Sex-related changes in the bone mineral content of atrophic mandibles.

In 25 edentulous anatomical mandible specimens (15 female, age range 69-90 years; 10 male, age range 68-88 years), the bone mineral content (BMC) was measured by dual-photon absorptiometry (DPA) and analyzed in a standardized area of the mandibular body. The results of our BMC examinations showed that there was a significant difference (P = 0.05) between the two sexes. Another notable fact was that, with advancing age, the values measured in the male mandibles tended to increase slightly but in a statistically significant way. Those of the female mandibles tended to decrease with age. A possible explanation for this observation may be derived from the fact that a reduction of the mandibular height leads to a reduction of the moment of resistance. As functional adaptation in order to preserve the stability of the atrophic body of the mandible, the amount of inner cortical bone of the male mandibles increases, leading to a reduction of the cancellous portion. In the mandibles of women, postmenopausal osteoporosis seems to prevent an analogous compensation mechanism.

Absorptiometry, Photon↗
PubMed1988

Bone mineral content by photon absorptiometry of the mandible compared with that of the forearm and the lumbar spine.

A new method for measuring the bone mineral content (BMC) of the mandible by dual-photon absorptiometry (DPA) has recently been introduced. The purpose of the present investigation therefore was to examine the long-term precision for 32 months in vitro and in vivo for assessment of BMC in the mandible and to examine the relationship in vivo among BMC of the mandible, the forearms, and the lumbar spine as measured by DPA and/or single-photon absorptiometry (SPA). For comparison, the relationship between forearm BMC as measured by DPA and SPA was studied. The long-term precision of the mandibular BMC was 0.8% in vitro, independent of age and change of radioactive source, and 2.1% by assessment in vivo. A significant relationship (P less than 0.01) was found between BMC of the lumbar spine and the forearms and between the two sets of forearm BMC measured by DPA and SPA. Thus, relative BMC changes of the forearms can be compared without respect to type of forearm bone scanner used. The BMC changes of the mandible can only be evaluated by scanning of the mandible itself. The present DPA bone scanner is suitable for follow-up analyses of the BMC changes of the mandible and the forearms.

Adult↗
PubMed2005

Changes in the edentate mandible in the elderly.

Resorption of alveolar bone is the best recognized feature of mandibular aging in the edentate subject. The other consequences of the loss of teeth in the elderly are less well known. An anthropometric study of the mandible by antero-posterior and lateral radiographs of subjects older than 70 years both dentate and edentate but without any maxillo-mandibular dysmorphosis has been done to demonstrate the differences, which exist between the dentate and edentate mandible. The edentate mandibles showed a diminution in the height of the symphysis and increase in the height of the mandibular incisure. A diminution in the height of the body and an increase in the gonial angle in the significant manner. No significant difference was seen for the height of the ramus and the length of the mandible, the minimum width of the ramus and the bigonial width. The diminution in the height of the mandibular symphysis and of the body is explained by the resorption of the alveoli part of the mandible. The increase in the mandibular angle and the diminution in the height of the mandibular incisure may be explained by disequilibrium between the elevator and depressor muscles of the mandible, as a function of the elevator muscles or by the absence of the molar buttress.

Aged↗
PubMed2005

An experimental and theoretical composite model of the human mandible.

The purpose is to design and manufacture a composite mandible replicate suitable for testing the influence of prosthetic materials on the stress distribution of bone. Composite mandibles made of a poly(methylmethacrylate) core and a glass reinforced outer shell are manufactured and characterised through mechanical tests assisted by the finite element analysis. The mandible replicate has been conveniently equipped with strain gauges, moreover a video extensometer has also been used in order to measure the arch width change during loading. A close agreement is found between the experimental data and the theoretical predictions. By laterally loading the mandibles the maximum values of stress and strain take place in the premolar-incisal region. By varying technological parameters such as the fiber volume fraction and orientation, it is easy to replicate the behaviour of mandibles having different stiffnesses. The results obtained by laterally loading the composite mandibles through the condyles or through the gonion regions are consistent with literature data relative to the arch width decrease of natural jaws during opening and closing. This novel synthetic system coupled with the Finite Element model constitutes an experimental-theoretical model suitable to investigate the biomechanical effects of oral rehabilitations on mandibular bone.

Humans↗