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PubMed1982

Histologic study of the attachment of muscles to the rat mandible.

The relationship of muscle to periosteum, tendon and ultimately to bone was studied in histological sections of rat mandibles aged 19 days in utero to 56 days postnatal. The following stains were employed: Van Gieson, Masson trichrome, Couciero and Friere, Gomori, orcinol-new fuchsin and Fullmer. Three modes of muscle attachment to the growing rat mandible were described according to the arrangement of collagen and reticular fibres at the interface between the bone and muscles. The morphological characteristics of the three modes persisted even in 56-day-old rats. The structure of the muscle-bone interface suggested a single mechanism of adaptation of muscles to bone during growth. With maturation, the size, number and variety of cells decreased and the size and thickness of collagen fibres increased in the muscle attachments. Each muscle was attached to the mandible by one or more types of attachment defined in this study. A schematic map of the distribution of the different attachment modes associated with muscles of the rat mandible was constructed. Distinction between these modes of attachment may be important in relating the form of a bone to its function.

Animals↗
PubMed1993

A three-dimensional, finite-element analysis of bone around dental implants in an edentulous human mandible.

The design of dental superstructures influences the loading on dental implants and the deformation of the anterior interforaminal bone in an edentulous mandible. This deformation causes stress in the bone around the implants and may lead to bone resorption and loss of the implant. The stress distribution around dental implants in an edentulous mandible was calculated by means of a three-dimensional, finite-element model of an entire lower jaw. This model was built from data obtained from slices of a single human mandible and was provided with two endosseous implants in the interforaminal region. The implants were either connected with a bar or remained solitary, and were loaded with a horizontal bite force of 10 N, a vertical bite force of 35 N, or an oblique bite force of 70 N. The most extreme principal stresses in the bone were always located around the neck of the implant. Stress around the implant was, therefore, not only caused by the local deformation of the bone due to movement of the implant and interface relative to the surrounding bone but also by the bending of the mandible. The most extreme principal stress was found with oblique bite forces. The highest maximum and lowest minimum principal stresses were 7.4 and -16.2 MPa in the model without the bar and 6.5 and -16.5 MPa in the model with the bar. When differences in the amount of bite force were eliminated, the vertical bite force resulted in the lowest stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Bite Force↗
PubMed1992

Reduction of the compact and cancellous bone substances of the edentulous mandible caused by resorption.

Examination of various bone sections of edentulous atrophic mandibles showed that the body of the mandible loses up to 60% of its original bone substance during progressive atrophy. Most of the bone loss occurs in a relatively early stage of the atrophic process. The greatest extent of bone reduction can be observed in the area of the second premolar and the first molar. In the interforaminal region, which is situated mesial from them, resorption, in most cases, is not as progressive as in the premolar/molar area. The compact and cancellous bone substances are most often equally affected by resorption. Moreover, it could be observed that the cancellous bone substance of extremely atrophic mandibles particularly in the interforaminal region, is marked by a significant increase in density. This might be interpreted as a restructuring process to compensate for bone losses and to secure the stability of the atrophic body of the mandible.

Alveolar Bone Loss↗
PubMed1994

A comparison of different imaging modalities and direct inspection after periosteal stripping in predicting the invasion of the mandible by oral squamous cell carcinoma.

OBJECTIVE: To compare the predictability of orthopantomograms (OPG), bone scans, computerised tomography (CT), magnetic resonance imaging (MRI) and periosteal stripping with direct inspection in predicting both the presence and extent of tumor invasion of the mandible. DESIGN: Prospective study. SETTING: Queen Elizabeth Hospital, Birmingham; Wordsley Hospital, Stourbridge; North Staffordshire Royal Infirmary, Stroke-on-Trent. SUBJECTS: 35 consecutive patients requiring a mandibular resection as part of their treatment for oral squamous cell carcinoma. MAIN OUTCOME MEASURES: The prediction of the extent of bone invasion for each of the investigations and direct inspection after periosteal stripping. The actual extent of invasion of the mandible from a detailed histological assessment. RESULTS: The OPG underpredicted the width and depth of invasion by on average 13 mm and 2 mm. There were 5 false negative reports. Bone scans overpredicted the width and depth by 14 mm and 15 mm with 1 false negative. CT scans underpredicted the width of invasion by 5 mm and overpredicted depth by 3 mm, but 7 false negatives were returned. MRI scans overpredicted width and depth of invasion by 19 mm and 10 mm with 1 false negative. Direct inspection after periosteal stripping underpredicted the width and depth of invasion by 5 mm and 3 mm with 1 false negative. CONCLUSION: OPG's and bone scans are useful for the initial assessment of all tumours in the region of the mandible. MRI is a more useful investigation than CT in the assessment of mandibular invasion by oral squamous cell carcinomas. Exploratory periosteal stripping at the time of resection can accurately predict the presence of tumour invading the mandible.

Adult↗
PubMed1992

Bone strain following application of a rigid bone plate: an in vitro study in human mandibles.

This study evaluated the effect of a bone plate on mandibular bone strain patterns during static loading. A stainless steel bone plate was unilaterally attached to five human mandibles, which were then subjected to static loads of 60 kiloponds. Four strain gauges attached to the cortical bone were used to measure the strain patterns within the mandible both before and after the bone plate was attached. The results showed that statistically significant alterations in the strain patterns occurred following plating of the mandible. The mandible with the plate attached became more stiff, presumably due to the difference in modulus of elasticity between the plate and the bone. However, this increase in stiffness was relatively small when compared with both total strain under load and strain produced by tightening of the bone screws.

Adult↗
PubMed1989

Does the mandible alter its functional position during activator treatment?

The study aimed at revealing possible changes, in activator-free periods, in the positions and movements of the mandible induced by the wearing of an activator. Twenty-one children being treated with three different types of activator for the correction of Angle Class II, Division 1 malocclusion were studied. The movement capacity of the mandible, the rest position, and the position of tooth contact during chewing were recorded with a Sirognathograph before treatment and repeatedly during the first year of treatment. With the exception of a slight increase in the maximal protrusion, no changes in mandibular movement capacity were found. The anteroposterior position of the mandible in the rest position was constant during the period of treatment, but the freeway space increased. No changes in the position of the point of tooth contact during chewing were found. The study produced no evidence of a treatment-induced forward positioning of the mandible in activator-free periods.

Activator Appliances↗
PubMed2004

Three-dimensional changes in the condyle during development of an asymmetrical mandible in a rat: a microcomputed tomography study.

A rapidly growing postnatal animal model was used to study changes in the calcified tissue of the mandibular condyle during altered muscle function. A maxillary occlusal splint was designed to shift the mandible laterally (left) during closure. Groups of 5 Wistar rats were killed at 5, 9, 15, 21, 30, and 40 weeks (n = 30), with an equal number of controls. The experimental animals developed shorter, asymmetrical mandibles compared with the control animals. The left condyle became larger and thicker than the right condyle. Microcomputed tomography assessment of the left and right condylar trabecular bone indicated that both had less bone volume than the control condyle. The right masseter muscle significantly lost fiber size and type IIA oxidative fibers, suggesting that the right masseter muscle was used with less tension development. In contrast, the left masseter maintained its fiber size and was similar to the control masseter fiber diameters. Comparison in the sequence of changes indicated that the morphologic changes occurred first in the ramus (age, 5 weeks), before the corpus (age, 15 weeks), and before changes in masseter fiber size and composition (age, 9 weeks). This study showed that both the mandible and the condyle modified their shape and size, as well as the trabecular bone of the condyle, during shifting of the mandible to one side as it closed.

Animals↗
PubMed2005

A new guide to mandibular resection for oral squamous cell carcinoma based on the Cawood and Howell classification of the mandible.

A new guide for mandibular resection in the management of oral squamous cell carcinoma based on the Cawood and Howell classification of the jaws is suggested. This was a retrospective review of case records and pre-operative orthopantomograms (OPG), bone scintigraphy and magnetic resonance imaging (MRI). The classification of the mandible was based on the residual bone height as measured in the molar region of the OPG to be equivalent to the Cawood and Howell classification of the mandible (Class I-II dentate or immediate post-extraction), Class III-IV >20mm well-rounded or knife-edge ridge, and Class V-VI <20mm (flat or depressed ridge form). Of the 77 patients, 58% (22/38) of Class I-II, 43% (9/23) of Class III-IV and 6% (1/16) of Class V-VI were treated with a marginal (rim) resection of the mandible. The predictability of the pre-operative investigations was more accurate in the edentulous mandible (Class III-VI). A simple guide is suggested for mandibular resection taking into account the pre-operative investigations, the estimation of invasion clinically, and the Cawood and Howell classification of ridge resorption.

Adult↗
PubMed2006

Numerical estimation of bone density and elastic constants distribution in a human mandible.

In this paper, we try to predict the distribution of bone density and elastic constants in a human mandible, based on the stress level produced by mastication loads using a mathematical model of bone remodelling. These magnitudes are needed to build finite element models for the simulation of the mandible mechanical behavior. Such a model is intended for use in future studies of the stability of implant-supported dental prostheses. Various models of internal bone remodelling, both phenomenological and more recently mechanobiological, have been developed to determine the relation between bone density and the stress level that bone supports. Among the phenomenological models, there are only a few that are also able to reproduce the level of anisotropy. These latter have been successfully applied to long bones, primarily the femur. One of these models is here applied to the human mandible, whose corpus behaves as a long bone. The results of bone density distribution and level of anisotropy in different parts of the mandible have been compared with various clinical studies, with a reasonable level of agreement.

Bone Density↗
PubMed2006

Validation of a musculo-skeletal model of the mandible and its application to mandibular distraction osteogenesis.

Mandibular distraction osteogenesis will lead to a change in muscle coordination and load transfer to the temporomandibular joints (TMJ). The objective of this work is to present and validate a rigid-body musculo-skeletal model of the mandible based on inverse dynamics for calculation of the muscle activations, muscle forces and TMJ reaction forces for different types of clenching tasks and dynamic tasks. This approach is validated on a symmetric mandible model and an application will be presented where the TMJ reaction forces during unilateral clenching are estimated for a virtual distraction patient with a shortened left ramus. The mandible model consists of 2 rigid segments and has 4 degrees-of-freedom. The model was equipped with 24 hill-type musculotendon actuators. During the validation experiment one subject was asked to do several tasks while measuring EMG activity, bite force and kinematics. The bite force and kinematics were used as input for the simulations of the same tasks after which the estimated muscle activities were compared with the measured muscle activities. This resulted in an average correlation coefficient of 0.580 and an average of the Mean Absolute Error of 0.109. The virtual distraction model showed a large difference in the TMJ reaction forces between left and right compared with the symmetric model for the same loading case. The present work is a step in the direction of building patient-specific mandible models, which can assess the mechanical effects on the TMJ before mandibular distraction osteogenesis surgery.

Adult↗
PubMed2004

Resorbable mesh as a containment system in reconstruction of the atrophic mandible fracture.

PURPOSE: The purpose of this article is to introduce the use of a resorbable material (L-lactide, Co DL-lactide) to help contain the bone graft used during the reconstruction of the edentulous atrophic mandibular fracture. TECHNIQUE: After the mandibular fracture was reduced and fixated with a large reconstruction plate, the resorbable mesh was contoured with scissors and a hot water bath. The mesh was secured into position with 1.5-mm tacks to the inferior border or buccal cortical plate of the mandible. The material was then filled with particulate bone graft harvested from the medial aspect of the anterior iliac crest. RESULTS: Two patients had augmentation of the superior aspect of the mandible and one patient had augmentation of the inferior aspect of the mandible. All patients were augmented at least 10 to 12 millimeters. The mean follow-up was 25 months. All went on to heal to complete bony union. CONCLUSION: This material can be used as a containment system when bone grafting the edentulous atrophic mandible fracture.

Absorbable Implants↗
PubMed2004

Effect of various stress models on lidocaine pharmacokinetic properties in the mandible after masseter injection.

PURPOSE: The aim of this study was to investigate the role of stress (trauma, cold swimming, and adjuvant rheumatoid arthritis) on lidocaine concentrations as well as lidocaine's protein binding in the mandible. MATERIALS AND METHODS: Forty male Wistar rats were used. The animals were divided into four groups. Group A served as control. Group B underwent mandible osteotomy. Group C was submitted to cold swimming stress. Group D was subjected to experimental arthritis. Additionally, all the groups received 5 doses of lidocaine, 1 dose of lidocaine (3 mg/kg) intramuscularly every 2 hours. Two hours after the last dose, the animals were killed. Lidocaine concentrations were estimated in plasma. Furthermore, the mandible was isolated, and both lidocaine concentrations and lidocaine protein binding were assessed. RESULTS: In groups under stress, lidocaine concentrations in serum showed a marked elevation. In addition, these animals demonstrated a significant decrease in the percent of lidocaine binding in the mandible. CONCLUSIONS: Stress can modify local anesthetics pharmacokinetic properties, resulting in alterations both in their concentration in serum and their protein binding in mandibular bone.

Adrenal Glands↗
PubMed2001

A three-dimensional, quantitative computed tomographic study of changes in distribution of bone mineralization in the developing human mandible.

The three-dimensional distribution of highly mineralized cortical bone on the buccal surface of the mandible was evaluated using quantitative computed tomography. The study was completed in 34 living persons (21 females and 13 males) between the ages of 9 and 32 yr of age with symmetrical mandibles. The geometrical distribution of the highly mineralized areas (>1250 mg/cm(3)) was determined by three-dimensional reconstruction of images. The pattern of distribution was evaluated by superimposing a 9 by 9-mesh grid over the lateral view of the mandible and adapting it to the same anatomical landmarks for different aged participants. Individuals demonstrated four different patterns of distribution of highly mineralized buccal cortical bone. The youngest had highly mineralized bone in the corpus of the mandible and along the anterior ramal border. In older individuals, the mineralization changed to include the mid- and posterior ramus. Highly mineralized bone was not found within the condylar, coronoid, or gonial angle regions of any participant. A comparison of the mineralization pattern between the left and right lateral mandibular views showed bilateral symmetry with similar patterns of distribution. Comparison of the number of grids occupied by highly mineralized cortical bone with the age of the participant, mandibular length, gonial angle, and cross-sectional area of the masseter muscle produced the highest correlation coefficient with the size of the masseter muscle.

Adolescent↗
PubMed1982

Simultaneous mobilization of the maxilla and mandible: surgical technique and results.

Simultaneous mobilization of the entire maxilla and mandible is a versatile procedure that can be used to correct multiple dentofacial deformities. The procedure is especially useful in correcting open bite deformities, as well as sagittal, vertical, and transverse dysplasias of the maxilla and mandible, and cases of asymmetry involving both the maxilla and mandible. Mock surgery performed on cephalometric tracings and study models provide a blueprint for the planned surgery. The use of an interim splint, constructed from sectioned models mounted on a semiadjustable articulator from a face bow transfer, is advocated to aid in accurate placement of the maxilla. The correct position of the maxilla is required to determine the ultimate position of the mandible; there is no room for error with this step if the procedure is to be accurate. Stabilization of the mobilized segments by direct osseous fixation, suspension wires, and maxillomandibular fixation is suggested. Maintenance of rigid maxillomandibular fixation for six weeks combined with an additional four weeks of guided mandibular function with skeletal elastics assures proper healing and position of segments.

Adult↗
PubMed1998

Vertical ramus compartment resection of the mandible for deeply invasive tumors.

PURPOSE: Vertical ramus compartment resection of the mandible is indicated in the management of pathology that originates in the ascending ramus or condyle of the mandible and invades the pterygomaxillary fossa, infratemporal space, parapharyngeal space, masseter muscle, or medial pterygoid muscle. This article describes the technique, presents a review of the relevant literature, and reports the outcome of five cases. PATIENTS AND METHODS: A retrospective review of all cases operated on by the senior author (R.A.O.) over the last 5 years at the University of Maryland was performed. The records of these cases were reviewed to identify patient sex, age, pathologic diagnosis, use of adjuvant therapy, and status after resection. RESULTS: Five surgical cases in which a vertical ramus compartment resection of the mandible was necessary were identified. The histologic diagnoses of these five cases were as follows: grade II chondrosarcoma, peripheral neuroectodermal tumor, high-grade central mucoepidermoid carcinoma, invasive squamous cell carcinoma, and odontogenic keratocyst. Four of the five patients are alive and well at follow-up of 16 to 43 months. The only death occurred in a 70-year-old man with squamous cell carcinoma that recurred intracranially by local extension. CONCLUSIONS: When indicated by local extension or tumor biology, vertical ramus compartment resection of the mandible is a viable surgical modality that allows clearance of local disease in most well-selected cases.

Adult↗
PubMed1981

Musculoskeletal adaption to surgical advancement of the mandible.

This study was carried out in order to evaluate musculoskeletal adaption to surgical advancement of the deficient mandible. 10 adult individuals with mandibular deficiency were studied before and 3 months after surgical advancement of the mandible via lateral cephalometric radiography, kinesiometry, and electromyographic instrumentation. 10 adult controls were studied at the same intervals, but underwent no surgery. The data was entered into a DEC System-10 computer for morphometric comparison and statistical analysis. The results of this investigation demonstrate that musculoskeletal adaptions occur within the stomatognathic system following surgical advancement of the mandible. 3 months following surgery, the clinical and physiological rest positions of the mandible as well as the masticatory electromyographic activity were unchanged in both the control and the surgery groups. The rapid, functional adaptions that occurred in the surgery group are apparently due to changes in posterior ramus-mandibular body relations and neuromuscular adaption within the masticatory and suprahyoid musculature.

Adaptation, Physiological↗
PubMed1984

Morphological study of unnamed foramina in north Indian human mandibles and its possible role in neurovascular transmission.

The present study was undertaken to investigate the different unnamed foramina in the mandible, placing more emphasis on the foramen present on the medial aspect of the mandible near the last molar teeth. Macerated mandibles in 4% of cases showed the presence of foramen. These were investigated for their possible role in neurovascular transmission. The unnamed medial foramen and the incisive foramen may transmit fibres from the nerve to mylohyoid, to supply the lower last molars and incisors, respectively, thereby providing escape of pain fibres to these teeth after the inferior dental nerve block by the local anaesthesia at the mandibular foramen. Mandibles dissected along with the attached muscles showed transmission of blood vessels through the foramina present at the insertion of muscles.

Humans↗
PubMed1980

A new method of anatomical reconstruction of extensive defects of the mandible with autogenous cancellous bone.

The mandible and adjacent area is a frequent site of various primary malignant tumours. Therefore resection of this bone is quite often indicated. The main problems associated with defects of the mandible resulting from extensive tumour surgery are: 1. the disadvantage of intermaxillary fixation for immobilization of the stumps of the mandible; 2. the risk of infection; 3. rigid fixation of the stumps of the mandible plus transplant; 4. the different shapes of those regions that have to be replaced (e.g. angle or chin); 5. the poor conditions for revascularisation of the transplant expecially after combined therapy (surgery and radiation). In order to find a way to solve these problems we have developed the three-dimensionally bendable defect bridging plate (3-DBDB plate). Further more we have developed a special technique for the transplantation of compressed cancellous bone. In the first part of the paper the 3-DBDB plate and the principles of transplanting compressed cancellous bone, as well as the specially developed instruments are explained. The second part deals with a typical case and problems of infection.

Aged↗