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At least 955 records · Page 53Linked to original sources
PubMed1999

Evaluation of bone density in the mandibles of young Australian adults of Mongoloid and Caucasoid descent.

OBJECTIVES: To evaluate the bone density in the mandibles of young Australian adults of Mongoloid and Caucasoid descent. METHODS: A panoramic radiograph (Orthophos C, Siemens AG, Bensheim, Germany) was obtained of 79 dental students from the School of Oral Health Sciences, The University of Western Australia. Exposure factors were varied for males and females. The films were automatically processed in a single batch and the optical density measured blindly at two locations by two examiners. The optical density was compared by race and sex to detect bone density differences. Individual lifestyle habits (exercise, alcohol consumption, smoking and diet) was recorded in a self-administered questionnaire. Multiple regression analysis was used to analyse the effects of physical, environmental and medical characteristics. RESULTS: The Mongoloid subjects were found to have approximately 20% higher bone density at the angle of mandible than Caucasoid subjects (P = 0.0094 for males, P = 0.0004 for females). CONCLUSION: Race is the most important variable associated with bone density. Mongoloid subjects should be given a higher exposure for panoramic radiography than that normally used for Caucasoid subjects.

Adolescent↗
PubMed1989

An evaluation of the relationship between rest position of the mandible and malocclusion.

Rest position of the mandible and integumental change in a control group of Class I occlusions is compared and contrasted with a study group of Class II malocclusion and a study group of Class III malocclusion. Change from centric occlusion to rest position of the mandible was suggestive of simulated correction of the malocclusion and improved facial esthetics.

Cephalometry↗
PubMed2006

Functional lateral deviation of the mandible and its positional recovery on the rat condylar cartilage during the growth period.

The objective was to examine the effects of a lateral functional shift of the rat mandible and the effects of a shift release on the condylar cartilage during the growth period. Fifty 5-week-old male Wistar rats were initially divided into three groups: shift, recovery, and control. At 5 weeks of age, each animal in the shift and recovery groups received an appliance designed to produce a lateral functional shift of the mandible to the left side. For the recovery group, the appliance was removed after 2 weeks. For the shift group, the appliance was used for 4 weeks. Total cartilage thickness, 5-bromo-2'-deoxyuridine-labeling index, and toluidine blue and tartrate-resistant acid phosphatase-positive cell number in the condylar cartilage at 1, 2, 3, and 4 weeks were compared with those in age-matched controls that had no appliances. In the shift group at 2 weeks, the cartilage thickness and labeling index increased in the central region on the contralateral side, whereas these decreased in the lateral region on the ipsilateral side. However, in the recovery group, 1 to 2 weeks after appliance removal, the cartilage thickness and labeling index in both investigated regions became similar to the control groups. These results emphasize the importance of early treatment to normalize occlusion and create appropriate conditions for normal occlusal development.

Acid Phosphatase↗
PubMed1995

Visual word recognition in two facial motion conditions: full-face versus lips-plus-mandible.

The present study used a new method to develop video sequences that limited exposure of facial movement. A repeated-measures design was used to investigate the visual recognition of 60 monosyllabic spoken words, presented in an open set format, for two face exposure conditions (full-face vs. lips-plus-mandible). Twenty-six normal hearing college students and 4 adults with bilateral sensorineural hearing loss speechread a video laserdisc presentation of a male talker under the two face exposure conditions. Percent phoneme correct scores were similar in the part-face and full-face conditions. However, scores significantly improved for the repeated measure independent of the face exposure condition observed. The results suggested that speechreaders (a) can recognize monosyllabic words in video sequences that provide information only about movements of the lips-plus-mandible region and (b) are sensitive to practice effects.

Adult↗
PubMed1997

Gonial angles and condylar and ramus height of the mandible in complete denture wearers--a panoramic radiograph study.

It has been accepted that the shape of the mandibular base, and especially the gonial angle of the mandible, correlates with the function of the jaw closing muscles. The gonial angles of the mandible and condylar and ramus heights of 30 complete denture wearers (18 women, 12 men, mean age 61 years, range 42-74 years) coming for renewal of their dentures were measured using panoramic radiographs. The mean period of edentulousness was 26 years (range 10-53 years). No statistically significant difference was observed between the sexes in the the sizes of gonial angles and condylar and ramus heights. The right gonial angle was statistically significantly smaller than the left one and correlated negatively with the ramus height in both sides but positively with the increased EMG activity in the right masseter muscle. The size of the gonial angle and the condylar and ramus heights did not correlate with the age of the patients, edentulous period or alveolar ridge resorption.

Adult↗
PubMed1998

Pathological bone changes in the mandibles of wild red deer (Cervus elaphus L.) exposed to high environmental levels of fluoride.

A macroscopic, microscopic and scanning electron microscope study was performed on the pathological bone changes of the mandibles of wild red deer (n = 61) exhibiting severe dental fluorosis. The animals originated from a highly fluoride polluted area in Central Europe (Ore mountains and their southern foreland, Czech-German border region) and constituted 11.2 % of the studied red deer sample (n = 545) from this area. Pathologically increased wear and fracture of fluorosed teeth caused a variety of mandibular bone alterations, including periodontal breakdown, periostitis, osteitis and chronic osteomyelitis. As a further consequence of severe dental attrition, opening of the pulp chamber and formation of periapical abscesses were occasionally observed. In case of severe periodontal breakdown, loss of teeth from the mandibles was found. In addition to the inflammatory bone changes, the occurrence of osteofluorotic alterations was also diagnosed in the specimens with the highest bone fluoride concentrations (> 4000 mg F-/kg dry wt). These changes comprised extended apposition of periosteal bone onto the mandibular cortex as well as deformation of the mandibular body, which was attributed to a fluoride-induced osteomalacia. The present study provided circumstantial evidence that, in addition to fluoride induced dental lesions, the occurrence of marked periodontal disease and tooth loss is an important factor responsible for a reduction of life expectancy in severely fluorotic wild red deer.

Animals↗
PubMed1999

Histochemical and immunohistochemical analysis of the mechanism of calcification of Meckel's cartilage during mandible development in rodents.

It is widely accepted that Meckel's cartilage in mammals is uncalcified hyaline cartilage that is resorbed and is not involved in bone formation of the mandible. We examined the spatial and temporal characteristics of matrix calcification in Meckel's cartilage, using histochemical and immunocytochemical methods, electron microscopy and an electron probe microanalyser. The intramandibular portion of Meckel's cartilage could be divided schematically into anterior and posterior portions with respect to the site of initiation of ossification beneath the mental foramen. Calcification of the matrix occurred in areas in which alkaline phosphatase activity could be detected by light and electron microscopy and by immunohistochemical staining. The expression of type X collagen was restricted to the hypertrophic cells of intramandibular Meckel's cartilage, and staining with alizarin red and von Kossa stain revealed that calcification progressed in both posterior and anterior directions from the primary centre of ossification. After the active cellular resorption of calcified cartilage matrix, new osseous islands were formed by trabecular bone that intruded from the perichondrial bone collar. Evidence of such formation of bone was supported by results of double immunofluorescence staining specific for type I and type II collagens, in addition to results of immunostaining for osteopontin. Calcification of the posterior portion resembled that in the anterior portion of intramandibular Meckel's cartilage, and our findings indicate that the posterior portion also contributes to the bone formation of the mandible by an endochondral-type mechanism of calcification.

Alkaline Phosphatase↗
PubMed1988

An experimental orthopedic treatment of the rat mandible using a functional appliance alters the fibre and myosin types in masticatory muscles.

Masticatory muscles mediate the action of functional orthopedic appliances on mandible growth. When young rats were treated for four weeks with a postural hyperpropulsor of the mandible, an appliance designed to increase condylar cartilage growth rate, the proportion of fast non-fatigable fibres in the lateral pterygoid muscle increased significantly. Concomitantly, the amount of slow-myosin light chains increased in fibre extracts. This slow myosin originated from IIA fibres. By functional orthopedic treatment, the lateral pterygoid muscle was enriched in less fatigable fibres; the changes observed in the lateral pterygoid muscle were close to changes observed in other muscles after training.

Adenosine Triphosphatases↗
PubMed2001

Proliferation of masseter myocytes after distraction osteogenesis of the porcine mandible.

PURPOSE: Long-term success of distraction osteogenesis depends on the ability of the surrounding soft tissues to tolerate distraction forces and to adapt to the resulting increase in skeletal length and volume. The hypothesis tested in this study was that mandibular elongation by distraction induces myocyte proliferation. MATERIALS AND METHODS: Unilateral mandibular angle osteotomies were performed in 16 Yucatan minipigs. The hemimandibles were lengthened using semiburied distraction devices (Synthes Maxillofacial, Paoli, PA) with 0-day latency, 1, 2, or 4 mm/d distraction rates, and a neutral fixation period of twice the gap size in days. In 2 additional animals, the dissection and osteotomies were performed, and distraction devices were placed without activation (sham control). At the end of neutral fixation, tissues were taken from masseter muscle overlying the osteotomy and the equivalent region on the unoperated side (contralateral control). Proliferation of myocytes was estimated using immunohistochemical localization with antibodies against proliferating cell nuclear antigen (PCNA). RESULTS: Muscle overlying the distracted mandible showed 6-fold more PCNA-positive myocytes (16.8% +/- 11.3%) than the contralateral control side (2.8% +/- 1.1%, P < .0001). In the 2 sham-control animals, there was a low index of PCNA-positive myocytes on both the osteotomy (2%, 5%) and the contralateral sides (1%, 2%). CONCLUSIONS: The results of this study suggest that distraction of the porcine mandible by the protocol described induces myocyte proliferation in the masseter muscle. A proliferative response may contribute to improved long-term stability of mandibular expansion by distraction osteogenesis.

Animals↗
PubMed2001

Intraoral distraction osteogenesis of the mandible in hemifacial microsomia.

PURPOSE: Lengthening of the mandible by distraction osteogenesis is the preferred method for treatment of hemifacial microsomia in children. Use of an intraoral distraction technique and horizontal oblique ramus osteotomy in such patients is presented. PATIENTS AND METHODS: Mandibular ramus lengthening was performed in 11 patients aged 6 to 12 years with hemifacial microsomia. During the age of mixed dentition in hemifacial microsomia patients with a hypoplastic mandible, the unerupted molars buds are located high in the retromolar region and are in danger of being damaged by the osteotomy. Therefore, an intraoral approach exposing the mandibular ramus and angle was performed, and a horizontal oblique ramus osteotomy was made, preserving the inferior alveolar nerve. An intraoral device was placed along the ramus, and distraction was started on the third postoperative day at the rate of 1 mm/d and continued for 2 to 3 weeks or as long as necessary. The device was maintained for retention an additional 6 weeks and was then removed. RESULTS: Clinically, the face became more symmetric. The postdistraction posteroanterior cephalometric radiographs demonstrated elongation of the affected ramus and improvement in facial symmetry. CONCLUSIONS: The advantages of this method are that it allows device placement along the ramus, permitting the ramus elongation necessary in treatment of hemifacial microsomia, that it prevents damage to the tooth buds which, during the age of mixed dentition, are in a higher position in the retromolar area, and that it prevents injury of the inferior alveolar nerve.

Cephalometry↗
PubMed2003

An experimental study on the growth of condylar cartilage, using a new vascularized mandible heterotopic transplant model.

PURPOSE: To clarify the influence of external and dynamic factors on the growth of mandibular condyle, we developed vascularized mandible heterotopic transplant (VMHT) model. In this report, we discuss histologic changes in the mandibular condylar cartilage in the absence of external factors, using VMHT models. MATERIALS AND METHODS: Thirty VMHT model using male Lewis rats aged 6 weeks were produced. Six VMHT rats were randomly selected for death at 1, 2, 4, 7, and 14 days after transplantation. We histologically investigated the mandibular condyles of the grafts and controls, the left mandibles of recipient rats. RESULTS: In the transplanted mandibular condyle of VMHT models, the cell arrangement became increasingly irregular with the passage of time, with a concomitant, irregular thickening or thinning of the cartilage layer. There was heterotopic fibrous ossification, extending horizontally under the proliferative cell layer in these regions of thin cartilage. After these events, cartilage cells had disappeared almost completely by 14 days after transplantation. CONCLUSIONS: This study indicated that external and dynamic factors are not necessary for the differentiation and proliferation of the condylar cartilage cells. Instead, these factors affect the maintenance of the orderly growth of the cartilage cells and may serve a critical role in the differentiation of undifferentiated mesenchymal cells into chrondroblasts.

Animals↗
PubMed1999

Non-free osteoplasty of the mandible in maxillofacial gunshot wounds: mandibular reconstruction by compression-osteodistraction.

We have treated 33 young men with medium to large (3-8 cm) bony and soft tissue defects of the lower third of the face caused by gunshot wounds. After debridement, collapsing the proximal segments for primary approximation of soft and hard tissues and a closed osteotomy of a small fragment of mandible, we used an original compression-distraction device, designed in 1982 and tested during 1983 (analogous devices were absent at that time) to reposition the mandible and cause callus to form (during distraction) between the fragment and to use the remaining stumps of bone to fill in the defect. The soft tissues were repaired at the same time. Twenty-eight of the patients presented within a few hours of injury, and the remaining five had old injuries. The only complications were in the group with old injuries where four patients developed abscesses that required drainage, but these did not interfere with the process of osteogenesis. All 33 patients had good functional and aesthetic results within 3-4.5 months. The method allows a bloodless minimally traumatic procedure which can be carried out in one stage. The results compare very favourably with the classic methods of the treatment of mandibular gunshot injuries.

Adult↗
PubMed2001

Bone regeneration using recombinant human bone morphogenetic protein-2 (rhBMP-2) in alveolar defects of primate mandibles.

The efficacy of bone morphogenetic protein (BMP) for bone reconstruction has been widely studied in numerous animal experiments, but insufficient information exists about its ability to regenerate bone in primates. The purpose of this study was to evaluate the effects of recombinant human BMP-2 (rhBMP-2) on bone formation in alveolar bone defects in the mandibles of young primates. Marginal bone defects were created in the mandibles of nine 5-year-old rhesus monkeys and rhBMP-2 permeated in a polylactic-co-glycolic acid-coated gelatin sponge (PGS) was implanted into the bone defects. The resected bone treated with rhBMP-2 regenerated completely at 12 weeks postoperatively, and remodelling and consolidation of new bone were seen histologically. This study provides evidence of considerable bone regeneration in alveolar defects after surgical implantation of rhBMP-2 in non-human primates. This technique may be an effective alternative to autogenous bone grafts for reconstructive surgery in clinical practice.

Absorbable Implants↗
PubMed2001

Complete bony fusion of the mandible to the zygomatic complex and maxillary tuberosity: case report and review.

Congenital craniofacial disorders represent approximately 20% of all birth defects. One of these disorders is syngnathia, of which only 24 cases have been reported since 1936. Twenty cases involved fusion of the alveolar processes of the maxilla and mandible. Only four are similar to the presented case, which includes bony fusion of the ascending ramus of the mandible to the zygomatic complex and the posterior part of the maxilla. This case report will present details from the 23rd week of gestation to 8 months of age when the infant underwent the first attempt to free the syngnathia. The literature is discussed and a causative mechanism and new classification are proposed.

Adult↗
PubMed2002

A recurrent case of odontogenic ghost cell tumour of the mandible.

Odontogenic ghost cell tumour (OGCT), also referred to as dentinogenic ghost cell tumour, is an extremely rare tumour classified as a neoplastic variant of calcifying ondontogenic cyst (COC). To date, only 13 cases of OGCT arising in the maxilla or mandible have been reported. We describe an OGCT that recurred after segmental resection of the mandible in a 59-year-old man. Histopathological examination revealed tumour invasion of the surrounding cortical bone, areas containing numerous calcifying flaky cell nests, and dentinoid matrix near epithelial cell nests. No atypical mitosis was found. There has been no evidence of recurrence or metastasis in the 4 years after operation.

Dentin↗
PubMed2002

Osteodistraction of a previously irradiated mandible with or without adjunctive hyperbaric oxygenation: an experimental study in rabbits.

The purpose of this study was to analyse the effects of irradiation and hyperbaric oxygenation (HBO) on mandibular osteodistraction (OD). Eighteen rabbits were divided into three groups: 1. Irradiation (R), 2. Irradiation+HBO (R-HO), and 3. Control group (C). Animals of groups R and R-HO received in the mandible irradiation 22.4 Gy in four 5.6 Gy fractions (equivalent to 50 Gy/25 fractions). In addition, group R-HO was given HBO at 2.5 ATA for 90 min per day 18 times preoperatively. Unilateral osteotomy was made 1 month after completion of radiotherapy. After a 1 week latency period bone distraction was started at rate of 1 mm per day, continued for 2 weeks, and left to consolidate for 4 weeks. Amount of new bone was measured histomorphometrically from midsagittal sections. Area of new bone was equal in all groups. Bone was more mature and bone spicules better organized in group C than in groups R and R-HO. Cartilaginous cells were found in distracted bone in all groups but larger chondroid islands were evident only in group R. It seems that despite delayed bone formation, OD can be performed after radiotherapy. HBO had a beneficial effect on bone quality of a previously irradiated mandible.

Animals↗
PubMed2003

Treatment of vascular malformations of the mandible: a description of 12 cases.

This study evaluated the treatment of intraosseous vascular malformation of the mandible. We analysed the medical records of 12 patients treated at the Salpêtrière Hospital (Paris, France) for vascular malformation of the mandible between 1965 and 1996. There were six male and six female patients, with a mean age of 16 years. The mean follow-up time was ten years. The treatment was surgery (enucleation or resection) or interventional radiology (arterial embolization or transosseous transcutaneous embolization). There are several indications for treatment, including age, and the size and type of vascular malformation (active or passive).

Adolescent↗