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At least 1,081 records · Page 60Linked to original sources
PubMed2000

Three dimensional model of the human mandible.

A new biomechanical three-dimensional (3D) model for the human mandible is proposed. A simple two-dimensional model cannot explain the biomechanics of the human mandible, where muscular forces through occlusion and condylar surfaces are in a state of dynamical 3D equilibrium. All forces are resolved into components according to a selected coordinate system. The muscular forces, which during clenching act on the jaw, along with the necessary force level for chewing, also act as some kind of stabilizers of the mandibular condyles preventing dislocation and loading of nonarticular tissues.

Biomechanical Phenomena↗
PubMed2000

Free omental transfer for osteoradionecrosis of the mandible.

Osteoradionecrosis (ORN) of the mandible can arise following therapeutic radiotherapy for head and neck cancer. The incidence is quoted as 10-15%. Conservative and surgical therapies used for ORN have included vascularized osteocutaneous flap transfers, hyperbaric oxygen and ultrasound therapy. We have used an omental transfer for ORN without a segmental resection. We wrapped the affected mandible within the omentum in order to promote revascularization and neocellularity. Four patients suffering from ORN have undergone omental transfers. Two cases developed pathologic fractures postoperatively that were successfully treated by conservative management. In all cases, the patients' intractable pain improved, and no patient showed recurrence of ORN or wound dehiscence. Postoperative bone scintigrams showed the same degree of accumulation in the lesion as in normal adjacent bone. These results demonstrate the effectiveness of omental transfer and suggest that omental transfer has a promising place in the management of ORN.

Aged↗
PubMed1975

[Prosthetic aids in the resection of the middle portion of the mandible].

Prosthetic aids in resections of the middle piece of the mandible. The authors describe a prosthesis which is inserted during the resection of the middle piece of the mandible. Due to its construction it prevents the soft tissues of the floor of the mouth from sinking back. Such a prosthesis has been used in 18 cases. Respiratory complications did not occur; no tracheotomy was necessary. During the postoperative phase, the prosthesis came up to expectations, but it could not prevent cicatricial contraction in the operating area. Occlusion-conformable positioning of the fragments will be achieved only it the remaining teeth are suited for function-stable prosthetic care. Consequently, secondary osteoplasty should not be abandoned.

Denture Design↗
PubMedDate not supplied

A comparative clinical investigation of 2 early loaded ITI dental implants supporting an overdenture in the mandible.

The purpose of this prospective clinical study was to evaluate the efficacy of early loading of implants and to provide evidence to support simplified treatment of mandibular edentulism by using an implant designed for 1-stage surgery, combined with ball abutments to circumvent the need for a fixed prosthodontic superstructure. Historically, the recommended time between the placement and functional loading of dental implants has been 3 months in the mandible. This recommendation is the result of a systematically chosen healing time during development of implant treatment. In recent years, histologic and experimental studies have shown that specially designed implants can result in increased bone-to-implant contact at earlier healing times. Accordingly, these implants can be placed into function faster than previously recommended. In this study, 21 patients aged between 61 and 85 years with edentulous mandibles were included. All received 2 titanium plasma-sprayed, solid-screw dental implants in the interforaminal region. Ten patients had the implants loaded with an overdenture connected with ball abutments after 3 months (control group). The other 11 patients (test group) had prostheses connected to the ball abutments after a maximum of 3 weeks. Marginal bone resorption, Periotest values, and patient satisfaction were evaluated. The cumulative post-loading implant survival rate was 100% for both groups after 24 months. Marginal bone resorption after 1 year around all implants ranged from 0 to 2 mm (no significant differences between groups; P < .05). Periotest values for all implants 1 year after loading were below zero (range -1 to -6). The results of this clinical trial suggest that successful early loading of 2 implants is possible provided there is uncomplicated implant placement.

Aged↗
PubMedDate not supplied

Bone mineral density in the growing human mandible.

The objective of this study was to investigate bone mineral density (BMD) in the growing human mandible by dual-energy X-ray absorptiometry, comparing densitometric data with the nature of the dentition and hence, indirectly, with variation of mechanical stresses. Postero-anterior scans were performed on 58 dried mandibles (between 15 months and 14 years) by a Hologic QDR 1000 X-ray densitometer with "Ultra-Hi-Resolution" software (Hologic Inc., Waltham, MA). The analyses were performed on a polygonal area corresponding to the infero-median region of the mandibular body, and divided into three sections. The sample was divided into two groups according to the appearance of the first permanent molar. A high correlation is detectable between BMD values and age in the group with decidual dentition, while BMD values are significantly less correlated with age in the group with mixed dentition. There are no significant differences between the BMD values of males and females.

Adolescent↗
PubMed2000

[Reconstruction of the mandible and soft tissue defects with the osteomyocutaneous free fibula flap].

OBJECTIVE: In order to ascertain a material that is ideal both for reconstruction of the composite mandibular defects and for osseointegrated implantation. METHODS: Fifteen osteomyocutaneous fibula flaps were transferred for reconstruction of the mandible and surrounding soft tissues. The characters of the blood supply of the flap, the operation course, the relation of the fibula and dental implants were observed. RESULTS: The osteomyocutaneous fibula flap was supplied by double vessels. The blood supply was reliable even after the fibula was cut into several segments. Periosteal circulation was its main blood supply. The postoperative contour and function of the mandibular region were good. The flap also favours dental implants and denture. CONCLUSION: The osteomyocutaneous fibula flap was the ideal material to reconstruct the defects of mandible and surrounding soft tissues.

Adult↗
PubMed1999

[Vascularized illiac bone grafts and reconstruction of the mandible].

OBJECTIVE: To investigate method of reconstructing large mandible defects. METHODS: Seven cases of mandibular defects were reconstructed with vascularied illiac bone grafts supplied by circumflex illiac vessels and Bränemark osseointegration implants immediately. RESULTS: Six months after operation, X-rays showed osseointegration between implants and graft bone. After 6 months to 36 months of follow-up, all implants were stable and no radiolucency was found and the functions were satisfactory in mastication, pronunciation and facial contour. CONCLUSION: Reconstruction of large mandible defects by vascularized illiac bone grafts supplied by circumflex illiac vessels and Bränemark osseointegration implants immediately is promising.

Adolescent↗
PubMed1997

Treatment of comminuted fractures of the mandible.

Management of comminuted mandible fractures requires careful planning. Treatment is based on a thorough understanding of the medical management of severely injured patients, biology of these injuries, the biomechanics of the mandible, and principles of fracture fixation.

Anti-Bacterial Agents↗
PubMed2002

[Fractures of the atrophic mandible--our experience at Tel-Aviv Medical Center].

UNLABELLED: Fractures of the atrophic edentulous mandible are relatively uncommon. The treatment poses a real challenge due to the underlying medical condition of the geriatric population affected. The complication rate such as infection or malunion is higher compared to fractures in younger patients. Twenty-three cases of fractures of edentulous mandible were reviewed and analyzed. CONCLUSION: The geriatric maxillofacial trauma patients can be treated with open reduction and rigid fixation which allows a quick return to normal function. The conservative approach "close reduction with Gunning-type splints is still an adequate mode of treatment in clinical settings where a more aggressive surgical approach is contraindicated.

Accidental Falls↗
PubMedDate not supplied

Morphological features in the embryological development of the anterior arch of the mandible.

OBJECTIVES: Our study is focused on the typical morphological features of the development of the mandible. There were investigated both specific elements for the ossification process as well as aspects of the developing tooth germs. METHODS: We performed transmission electron microscopy analyses on sections obtained from 15 human embryos aged between 6 and 20 weeks. The sections were acquired from specific areas of the anterior arch of the mandible, corresponding to the sites of development of the tooth germs, namely the incisors and the canines. RESULTS: There were observed some characteristic elements for the intramembranous ossification process (mesenchymal cells, collagen fibers, osteoblasts, bony spicules), and for the different stages of odontogenesis (bud, cap). CONCLUSIONS: The results confirm the important role of this territory and highlight the primary elements of the intramembranous ossification and of the odontogenesis, as essential steps in the development of the head and the face.

Humans↗
PubMed2002

The compensation of dental arch and teeth in patients with skeletal protrusion and deviation of mandible.

OBJECTIVE: To investigate the compensation of dental arch and teeth in patients with skeletal protrusion and deviation of mandible. METHODS: Measurement of 11 dental models was performed, midline of palate was defined as central line, the distance of every contact point to the midline was measured in each side. The dental arch symmetry was observed. Occlusion plane was defined as conference plane, the buccal or lingual inclination of posterior teeth in upper and lower arch was measured. RESULTS: Upper arch was asymmetry in these patients, the arch width of deviated side (the side that the chin was deviated to) was broader than the other side. The posterior teeth of upper and lower arch were more buccally and lingually inclined respectively. CONCLUSIONS: Skeletal protrusion and deviation of mandible may result in compensation of dental arch and teeth, the de-compensation is important in pre-operative orthodontic treatment.

Dental Arch↗
PubMed2002

Thin-plate spline graphical analysis of the mandible in mandibular prognathism.

The chin cup has been used to treat skeletal mandibular prognathism in growing patients for 200 years. The pull on the orthopedic-force chin cup is oriented along a line from the mandibular symphysis to the mandibular condyle. Various levels of success have been reported with this restraining device. The vertical chin cup produces strong vertical compression stress on the maxillary molar regions when the direction of traction is 20 degrees more vertical than the chin-condyle line. This treatment strategy may prevent relapse due to counter-clockwise rotation of the mandible. In this report, we describe a new strategy for using chin-cup therapy involving thin-plate spline (TPS) analysis of lateral cephalometric roentgenograms to visualize transformation of the mandible. The actual sites of mandibular skeletal change are not detectable with conventional cephalometric analysis. A case of mandibular prognathism treated with a chin cup and a case of dental Class III malocclusion without orthodontic treatment are described. The case analysis illustrates that specific patterns of mandibular transformation are associated with Class III malocclusion with or without orthopedic therapy, and that visualization of these deformations is feasible using TPS graphical analysis.

Cephalometry↗
PubMed2002

[A histomorphologic and enzyme histochemical study of masticatory muscles affected by distraction osteogenesis of mandible].

OBJECTIVE: The purpose of this study was to study the masticatory muscles affected by distraction osteogenesis of the mandible. METHODS: The distraction osteogenesis (DO) was applied to distract the left mandible of 6 mongrel dogs that were divided into three experimental groups. After different distraction phase and consolidation phase, the masseter and the digastric muscle were taken out. The specimens were stained using hematoxylin/eosin and enzyme histochemistry. Afterwards, the specimens were observed with a light microscope to study the morphologic changes of the muscles. The contents of enzyme in the different groups were measured by VIDAS. RESULTS: The masseter showed consequently atrophy, but the digastric muscle showed a progress of histomorphologic reconstruction, including atrophy and hypertrophy. The changes of the contents of enzyme and histomorphology were identical in the masticatory muscles. CONCLUSION: The digastric muscle parallel to the vector of mandibular distraction adapts the distraction by the way of atrophy, regeneration and hypertrophy. And the contents of enzyme appear to decrease at the beginning, increase afterwards, and return to the normal level finally. But the masseter perpendicular to the vector of mandibular distraction shows consequent atrophy, and the contents of enzyme consequently decrease, which means the metabolism decrease.

Adenosine Triphosphatases↗
PubMedDate not supplied

Immediate functional loading of Brånemark system implants in edentulous mandibles: clinical report of the results of developmental and simplified protocols.

PURPOSE: This report evaluates the 5-year results of 9 of 10 patients in a clinical investigation of immediate functional loading of Brånemark System implants in edentulous mandibles, and of 24 patients treated with a simplified protocol for the same indication. The purpose of the paper is to suggest a simple, reliable, and documented method for immediate implant loading of complete-arch mandibular prostheses. MATERIALS AND METHODS: Ten healthy patients in need of full-arch mandibular implant reconstruction (development group) were treated between December 1993 and December 1994 with 130 Brånemark System standard Implants, placed in fresh extraction and healed sites. Four implants per patient were immediately loaded with acrylic resin fixed prostheses. The prostheses were replaced by metal-framework conversion prostheses approximately 6 weeks later, and definitive metal-reinforced prostheses incorporating all implants were placed after second-stage surgery. An additional 24 patients were treated with a simplified protocol using a total of 144 implants placed between March 1997 and October 2000. In these patients, the acrylic resin prostheses were not disturbed for 3 months, and fewer implants were used with an increasing ratio of implants loaded. Eventually, all Implants were loaded immediately for the last patients treated. RESULTS: The prosthesis survival rate was 100% for the total material. In the developmental group, the implant cumulative survival rate was 80% for the immediately loaded implants after 5 years, while the 2-stage implants reached 96%. Bone level measurements showed no differences between immediate and 2-stage protocols for this group. The implant cumulative survival rate was 97% for the simplified treatment group. DISCUSSION AND CONCLUSION: A predictable and simple concept for loading of immediate implant prostheses in edentulous mandibles was demonstrated. Results from the development of this technique suggest that it may be essential to maintain the initial implant splinting over a healing period of about 3 months and that implant placement between the mental foramina provides optimal support.

Aged↗
PubMed2003

[Study of estrogen deficiency impact on manganese levels in teeth and mandible of rats after ovariectomy].

Deficiency of the estrogens occurring after menopause or ovariectomy leads to osteopenia and osteoporosis. It was confirmed by noninvasion examinations of bones--skeleton, maxilla mandible and teeth. Demineralization of the hard tissues were connected with loss of calcium and phosphorus, however the role of microelements is not completely known (for example role of Mn). The aim of the study was an attempt of explanation of manganese behave in the structure of hard tissues of masticatory system when the level of estrogens was decreased. Experiment was realized on Wistar female rats. They were divided into seven following groups: CL--control, SH--sham operated, OV--after ovariectomy, OVO--ovariectomized which administered "oleum pro injectione", OVH1--OVH3--ovariectomized which administered 17 beta-estradiol in three doses: 1.25 micrograms, 12.5 micrograms, 125.0 micrograms (dose on the rat) twice a week. After ovariectomy the level of manganese in teeth as well as in mandible decreased in compared with control group. Differences were statistically significant. Administration of 17 beta-estradiol of ovariectomized female rats caused increase of manganese content inconsiderable. These results may suggest that ovarian estrogens play an important role in mineralization of bones and teeth and in prophylaxis of postmenopausal osteoporosis.

Animals↗
PubMed2002

The loss of alveolar processus, mandible density and bone tissue structure in reference to the computerized analysis of intraoral radiography.

98 patients treated in the Department of Dental and Maxillofacial Surgery, Medical University and Institute of Rural Medicine in Lublin had radiovisiographically tested premolar teeth area on the left side. Reviewing radiovisiographical picture, there were defined bone mineral density and mandible bone structure and degree of loss of alveolar processus. It was concluded that the degree of loss of alveolar processus is significantly correlated with the researched patients' age, and is inversely correlated with mineral density and equivalent of mandible bone mineral contents. The achieved results prove that demineralisation changes can significantly influence teeth loss.

Absorptiometry, Photon↗
PubMed2002

Influence of estrogen deficiency on the copper level in rat teeth and mandible.

On the basis of atomic absorption spectrophotometry rat teeth and mandible copper levels in experimental postmenopausal osteoporosis and after administration of 17 beta-estradiol were measured. The results showed that estrogen deficiency leads to decrease in copper content in rat teeth and mandible, and giving of 17 beta-estradiol positively influence the content of mineral components in the examined tissues.

Animals↗
PubMedDate not supplied

Immediate occlusal loading of Osseotite implants in the completely edentulous mandible.

PURPOSE: This article reports the preliminary data from a clinical study of immediately loaded, full-arch, screw-retained prosthesis with distal extensions (hybrid prosthesis) supported by Osseotite implants placed in the edentulous mandible. MATERIALS AND METHODS: Fifteen patients who received 103 implants were enrolled in this study. The first 2 patients received both immediately loaded and submerged implants, while the remaining patients had all implants immediately loaded. The first 9 patients received a temporary prosthesis within 4 hours of surgery, and the hybrid prosthesis, made of a titanium framework and acrylic resin teeth, was placed after 6 months. The last 6 patients received the same type of hybrid prosthesis within 36 hours of surgery. Marginal bone loss was monitored via periapical radiographs by a computerized technique. RESULTS: One failure (out of the 92 immediately loaded implants) occurred after 3 weeks of function because of infection. A cumulative success rate of 98.9% was achieved for up to 48 months of follow-up, while the prosthetic cumulative success rate for the same period was 100%. Marginal bone loss at the immediately loaded implants was within the generally accepted conventional limits for standard delayed loading protocols. DISCUSSION: This technique can reduce treatment time but should be applied with caution. CONCLUSION: The preliminary results of this study suggest that rehabilitation of the edentulous mandible by an immediately loaded hybrid prosthesis supported by 5 to 6 implants may represent a viable alternative treatment to the classical delayed loading protocols.

Acrylic Resins↗