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PubMed1988

A macroscopic study of the effect of oxygen on the growth of the rat mandible and femur in vivo.

The effect of oxygen on the growth of the mandible was studied in 40 Long-Evans/Turku rats. Pregnant rats were exposed to increased oxygen tension for 16 days from 7 to 23 days of gestation. After parturition the young rats were kept under normal laboratory conditions until the age of 50 days and then killed for macroscopic examination. Fifteen rats were exposed to increased oxygen tension from 15 to 50 days postnatally and then killed. The control animals were kept under normal laboratory conditions throughout. A prenatal increase in oxygen tension had no marked effects on the dimensions of the mandible at the age of 50 days, although the height of the mandible was increased when the dimensions were corrected for body weight. A postnatal increase in oxygen tension reduced the length of the mandible but increased its height. Although low oxygen tension has been thought to favor cartilage formation, and although function is considered necessary for the growth of the mandibular condyle, it seems that the latter process is stimulated by increased oxygen tension and reduced by loading.

Animals↗
PubMed1993

Effect of food consistency on the shape of the articular eminence and the mandible. An experimental study on the rabbit.

The aim of this investigation was to ascertain what changes masticatory function could elicit in the shape of the articulating surface and the growth of the mandible in a growing rabbit. Forty-seven rabbits were divided into two groups, a control group fed whole pellets and a 'soft' group fed softened pellets and having their incisors shortened once a week. All the rabbits were killed at the age of 50 days and roentgenographed, after which the heads were freed of soft tissues, and the shape of the articulating eminence, the dimensions of the mandible and the maxilla, and intermaxillary relations were measured. The articulating surface of the glenoid fossa was steeper in the soft group, the lower border of the articulating eminence was located more inferiorly, and the mandible was more retrognathic. It is concluded that the difference in functional stress affects the shape of the articular eminence and the intermaxillary relationship. When the condyle is functioning more on the eminence, the latter becomes flatter, and the mandible moves forwards.

Animal Feed↗
PubMed1996

Differences in biologic response of the mandibular condyle to forward traction or opening of the mandible. An experimental study in the rat.

The effect of different mandibular postures on the growth of the mandible was studied. A total of 60 female Wistar rats were divided into 3 groups, and all the animals were anesthetized for 6 h daily from the age of 30 days onwards. The first group served as controls. The second had the mandible maintained in a protracted position, and the third had the mandible in an open position during the anesthesia. Macroscopic measurements showed the growth of the mandibular condyle to be increased in a posteroinferior direction and also in a superior direction in the animals with the mandible in an open position. The cartilage layer containing collagen type II was significantly thinned, whereas cell proliferation had significantly increased in the posterosuperior region. In association with mandibular protrusion the thickness of the cell layer containing collagen type II had increased, and cell proliferation in the posterosuperior region had significantly decreased. Significant differences in the growth of the condylar process were observed histologically and histochemically between the experimental animals, implying that the most rewarding aspect of the regulation of condylar growth seems to be the possibility to regulate the maturation rate of the cartilage cells.

Adaptation, Physiological↗
PubMed1996

Downregulation of Msx-2 expression results in chondrogenesis in the medial region of the avian mandible.

Homeobox-containing genes are thought to be regulators of pattern formation during vertebrate development. We have previously characterized regions in the developing chick mandible expressing either Msx-1 or Msx-2 in terms of their chondrogenic potential, rates of cell proliferation, and their correlation with regions of cell death. These experiments suggest that Msx-1 may be involved in outgrowth of the mandibular arch, and Msx-2 may be involved in delineating the non-chondrogenic region of the medial part of the mandibular arch. To further examine the possibility that expression of Msx-2 may be involved in preventing chondrogenesis in the medial region, mandibular arch explants from stage 23 chick embryos were cultured for 4 days in media in the absence of serum but in the presence of 20-30 microM Msx-2 sense or antisense oligonucleotides (18 mers). In explants grown in either control media or with the sense oligonucleotide two rods of cartilage separated by a cartilage free area located in the medial region of the mandible were formed. In explants treated with Msx-2 antisense oligonucleotide cartilage formation was observed in the medial region of the mandible resulting in the fusion of the two bilateral rods at the midline. These results suggest a negative relationship between Msx-2 expression and chondrogenesis in the medial region of the developing mandible.

Animals↗
PubMed1984

Time-dependent effects of a 'functional'-type orthopedic appliance on the rat mandible growth.

The modus operandi and the time-dependent variations in the effects of the LSU-activator, an orthopedic appliance currently used in human orthodontic therapy, was experimentally analyzed in growing rats. This appliance causes a forward positioning of the lower jaw and a restriction of mandibular motility. After a 4-week treatment, the following changes were observed: (i) the growth rate of the condylar cartilage was accelerated, this growth-promoting effect being more pronounced when the LSU-activator was worn during the animal's rest span. (ii) the direction of condylar growth became more backward-oriented; no significant difference between day and night treatment, i.e. during the rest and activity spans could be detected; (iii) the supplementary lengthening of the mandible was greater in rats treated during rest than in rats treated during waking and (iv) the number of serial sarcomeres in the lateral pterygoid muscle was smaller. This growth retardation of the muscle was greater in rest-time than in waking-time treated individuals. The LSU-type activator's action implies a two-step effect: during the time of wearing the appliance, the more forward positioning of the mandible causes a reduced growth of the lateral pterygoid muscle; during the time the LSU-type activator is not worn, the mandible is functioning in a more forward position such a way that it stimulates the growth rate of the condylar cartilage and the subperiosteal ossification of the posterior border of the ramus. It is therefore essential, for a few hours every day, that the mandible be allowed to move freely from the appliance in a more forward position.

Activity Cycles↗
PubMedDate not supplied

The position and dimensions of the mental foramen in adult Malawian mandibles.

BACKGROUND: The mental foramen is found on the anterolateral aspect of the mandible and transmits the mental nerve and vessels. The identification and actual location of this foramen is very important in clinical dentistry as well as in the microscopic and macroscopic evaluation of the morphology and maturity of the human mandible. METHODOLOGY: We determined the position and dimensions of this foramen from seventy adult indigenous Malawian mandibles of both sexes. The shape, number and orientation of the mental foramen were determined by visual examination and its transverse and vertical diameters measured using a digital venier caliper. RESULTS: In the majority of cases, the mental foramen was oval in shape, oriented posterosuperiorly, and bilaterally symmetrical. The modal position of the foramen with respect to the mandibular teeth was inferior to the second premolar tooth. Its vertical position was slightly below the midpoint of the distance between the lower border of the mandible and the alveolar margin. CONCLUSION: The shape and orientation of the mental foramen shown in our study correspond to what have been documented in most previous studies. However, variations do exist in the modal position of this foramen in different population groups. We therefore stress the importance of palpation of the foramen during administration of local anaesthesia and in the interpretation of radiographs prior to surgery.

Adult↗
PubMedDate not supplied

Application of capacitively coupled electric field enhances periimplant osteogenesis in the dog mandible.

PURPOSE: Expeditious postoperative ingrowth of bone into dental implants is desired for clinically successful fixation of oral implants. The present study was performed to evaluate the effect of applying a capacitively coupled electric field (CCEF) on periimplant osteogenesis in the dog mandible. MATERIALS AND METHODS: Twelve adult male beagles were used in this study. All of the premolars on both sides of the mandible were removed from each dog. A POI (Ti-6Al-4V) 3-piece implant (3.7 mm in diameter and 8.0 mm in length) whose surface had been treated with anodic oxidation was placed into each test site by self-tapping. Daily application of CCEF (8 h/day) was initiated on the day following the surgery and was continued through the day of sacrifice. A CCEF was induced by an external source delivering 10-Vp-p, 60-kHz sine-wave signals through an oral electrode plate. One side of the mandible of each dog was treated with CCEF, while the other side was not. On the control side, an oral electrode plate was attached for 8 hours per day, but CCEF was not applied. The effect of daily application of CCEF on the ingrowth of bone into the implant was examined at 14, 21, or 30 days after implant placement. A fourth control group was not treated with CCEF and was maintained for 90 days to confirm that CCEF treatment enhances bone ingrowth in dental implants. RESULTS: Daily application of CCEF significantly increased the bone-contact ratio at days 14, 21, and 30 after implant placement in comparison with the respective controls. The bone-area ratios of the 14- and 21-day CCEF-treated groups were significantly larger than those of the respective controls and were similar to those of the 90-day control group. CONCLUSION: CCEF treatment increases periimplant osteogenesis in the dog mandible, confirming its usefulness in oral implantology.

Alloys↗
PubMed2000

The arrangement of the trabecular bone in the vestibular surface of the human fetus mandible. A scanning electron microscopy study.

The characteristics of trabecular bone in human fetuses at seven to nine months of intra-uterine life were studied in the vestibular surface of the mental and body portions of the mandible. In the mental portion, many circular trabeculae joined by "bridges" were observed in the alveolar region (AR). In the 8-month old fetus are trabeculae with tortuous disposition in the medium region (MR). Oblique trabeculae with superior and inferior dispositions defining a triangular area (future mental fossae) are verified in 9-month old fetuses. Trabeculae circularly disposed and vascular foramina are present close to the apex of this area. In the basilar region (BR) some trabeculae obliquely oriented are observed disposed near to the mandibular symphysis. The longitudinal bundles of collagen fibers assume an antero-posterior direction. At 9-month age the vascular foramina range from 6 to 20 microns and the osteocyte lacunae ranging from 1 to 4 microns diameter, are present in mandibles from all ages examined. In the body portion the presence of circular trabeculae joined by "bridges" is the main characteristic of the AR. In the MR most of the trabeculae are circular and the longitudinal trabeculae of this region assume an antero-posterior direction. The laminar, antero-posterior and juxtaposed trabeculae lying parallel to mandible base are a characteristic of the BR. The bundles of collagen fibers exhibit the same pattern of the trabeculae. The vascular foramina of the BR are smaller than that of the precedent regions. In the body portion of the mandible from all ages examined the osteocyte lacunae range from 1 to 4 microns in diameter.

Female↗
PubMed2000

Dislocation of the mandible: a case report.

Dislocation of the mandible is a possible complication of direct tracheal laryngoscopy. The temporomandibular joint (TMJ) is unique in that any movement of the bone always causes movement in both joints simultaneously. The entire TMJ is surrounded by a ligamentous capsule and is stabilized by 3 ligaments. Four muscles of mastication move the mandible with great power. The lateral pterygoid muscle has nearly horizontal muscular fibers and is chiefly responsible for dislocating the mandibular condyle and articular disc past the articular eminence into the infratemporal fossa, causing the patient great pain and distress. If mandibular dislocation should occur, prompt recognition and treatment of the dislocation is recommended. There are steps, used by dentists, which can be employed by the nurse anesthetist to relocate the mandible. The technique for intraoral bimanual relocation of the mandible is described.

Aged↗
PubMed2000

[Effects of the occlusal splint on stress distribution of the mandible with temporomandibular joint disorders].

OBJECTIVE: To investigate the biomechanical mechanism of occlusal splint therapy of temporomandibular joint disorders (TMD). METHODS: The changes of stress distribution on the mandible with TMD before and after occlusal splint therapy were simulated and analyzed by three-dimensional finite element method. RESULTS: Occlusal splint influenced the character of stress distribution on the mandible. It might distinctly decrease maximum and minimum principal stresses on each region of the mandible with TMD, among which the stress on condylar surface of ill side was reduced more significantly, and the stress distribution of bilateral condyles was close to equality and balance. Meanwhile, the stress symmetry on every position of the mandible was improved slightly. CONCLUSIONS: Occlusal splint can alleviate even eliminate the injury to the temporomandibular joint, and make unbalance of joint inner environment adjusted and restored by improving the stress distribution. This is primarily thought to be one of the main biomechanical mechanism of occlusal splint treatment.

Biomechanical Phenomena↗
PubMed2002

Reconstruction of the mandible by fibula free flap.

BACKGROUND: The most frequent cause of defect in the mandible is tumor-related surgery. Larger defects or anterior arch defects cause severe morbidity due to disturbances in function and esthetics. OBJECTIVES: To assess the outcome of free tissue transfer for mandible reconstruction. METHODS: Since 1998 we operated on 11 patients with mandible defects using the fibula flap as the reconstruction method. We performed immediate reconstruction in eight patients after ablative surgery, and late reconstruction due to radiation-induced complications in three. RESULTS: All patients achieved good functional and esthetic outcome. During the follow-up period two patients died of their malignant disease and one patient died from a non-related cause. Although two patients underwent reoperation in the first 3 months after their primary operation due to fixation failure, there were no other major complications. CONCLUSIONS: According to the literature and our limited experience, the fibula flap is a safe and reliable option for mandible reconstruction.

Adult↗
PubMed1977

[The choice of a surgical method for the correction of sagittal over and under development of the mandible].

The experience gathered in the correction of sagittal mandibular over- and under-development allows to make the following conclusions:--In the choice of osteotomy it is necessary that careful consideration be given not only to the proportions of the body and ramus of the mandible, but also to the angular interrelationships of mandibular bones.--Osteotomies in the body of the mandible are indicated especially in those cases where it is only necessary for parallel shifts to be made in the sagittal plane.--Osteotomies performed in the region of the angle of the mandible and the ramus of the mandible (Obwegeser-Dal Pont) enable both longitudinal compensation or adjustment in the sagitta. plane and correction of transverse deformities and unfavorable angular relationships.--In the case of backward and forward displacement of the lower jaw it is essential that the position of the chin be considered already in the stage of planning the surgical operation. Suitable corrections can be made in the course of one surgical intervention.--Preliminary orthodontic treatment, because of the creation of optimum conditions of occlusion, will in many cases provide most favorable prerequisites of a surgical intervention.

Adult↗
PubMed1992

Growth of the skeletal units of the rat mandible in acute renal failure experimental model.

A study of the effect of acute renal failure (ARF) on the growth of the skeletal units of the mandible was performed. Male Wistar rats weighing 35-40 g were assigned to three groups. One of the groups received a basal choline-deficient diet ad libitum. A second group was pair-fed with the first one and was given a basal diet supplemented with 0.35 g choline chloride/100 g of diet. The third group was fed a basal diet plus 0.35 g choline chloride/100 g of diet ad libitum and used as the normal control. Body length, renal function parameters and measurements of the mandible were recorded at the end of a 12-day period on the different diets. Food intake and body weight were recorded every day. Plasma urea and creatinine concentrations markedly increased over the first 12 days of exposure to a choline-deficient diet. Significant increases in urine volume and significant depressions in urine osmolality were also observed. The average body weight and body length gains for rats given the choline-deficient diet were lower than those of control rats. There were no significant differences between the average body weight and body length of pair-fed and normal rats. All skeletal measurements of the mandible of the choline-deficient group differed significantly from those of the control group. These differences varied between 7% and 30%. The skeletal units of the mandible of the pair-fed group did not differ significantly from ad libitum controls. This study suggests that this rat model can be used for the investigation of the different alterations observed in uremia.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed2004

[A review of 11 cases of immediate free flap transfer for treating the advanced osteoradionecrosis of mandible].

OBJECTIVE: To assess the effectiveness and reliability of free flap transfer for treating the advanced osteoradionecrosis (ORN) of mandible. METHODS: Eleven cases of free flap transfer for treating the advanced ORN of mandible from October 1999 to February 2003 were reviewed. Data concerning the operation included site, stage and histology of primary tumor, dosage of radiotherapy, defect description, design of free flap, recipient vessel, free flap survival and complications. RESULTS: There were 8 males and 3 females, with age ranged 29-65 years old. Fifteen free flaps were used for reconstructing the defects, 12 were fibula flap, 2 were rectus abdominis myocutaneous flap, and 1 was radial forearm flap. All the free flaps survived completely without partial or total necrosis. The complication rate was 36.4%. All patients had complete resolution of ORN symptoms. No evidence of ORN recurrence was observed in any patient. CONCLUSION: Free flap transfer provides a reliable and effective means for treating the advanced ORN of mandible. Free fibula flap is the workhorse flap for reconstruction of mandible.

Adult↗
PubMedDate not supplied

Dental rehabilitation using an implant-supported overdenture after repair of a fracture in a severely resorbed edentulous mandible: a case report.

Treatment of mandibular fracture in senior citizens with severely resorbed edentulous mandibles is extremely difficult. Such treatment must achieve successful osteosynthesis and restore functional mastication. A severely resorbed (Class V) mandible was successfully reconstructed with an autogenous bone graft on the inferior border of the mandible and a titanium mesh plate after a failed attempt to fix the fracture. After the placement of endosseous implants in the mandible, the patient was rehabilitated with an overdenture to restore masticatory function.

Aged↗
PubMedDate not supplied

The varying shape of the coronoid process of the mandible.

The coronoid process (meaning crow) is a flattened triangular bony process of the ramus of the mandible. It is usually directed upwards and slightly forwards in the living subject. The coronoid process is of clinical significance to the maxillofacial surgeon for reconstructive purposes. Several authors have described the varying shapes of the process. In the present study, the variable shape and surface area of the coronoid process were observed in a collection of 154 south Indian mandibles. Using the criterion proposed by Isaac and Holla (2001), the coronoid process of each side was inspected for the shape and direction, and surface area of the ramus and the coronoid process was also calculated. The shape of the coronoid process was bilaterally triangular in 16.2%, hook-shaped in 45.5%, rounded in 18.2% rounded and hook-shaped in 4.5%, and unilaterally triangular in 12.3%, hook-shaped in 11.7%, and rounded in 7.1% of the mandibles. The coronoid processes faced directly upward in 55.4%, forward in 40.7% and backward in 3.8% of the mandible.

Adult↗
PubMed2005

[The preliminary study on the characteristics of mandible and condyle in dentin matrix protein-1 gene knockout mice].

OBJECTIVE: To study the characteristics of mandible and condyle in Dmp1 gene knockout mice, and to investigate the role of Dmp1 in the osteogenesis and mineralization of bone and cartilage. METHODS: Dmp1-/-mice were executed at birth, 2 weeks, 2 months, 3 months and 5 months, and the mandible was taken out for physical, radiography, transmission electron microscopic, and histological examination. The difference between Dmp1 knockout mouse (ko) and wild type mouse (wt) in bone development, bone densitometry and histology were compared. RESULTS: There were obvious changes in the mandible and condyle of Dmp1-/-mouse, such as incomplete ossification, low density, decreased volume and condyle cartilage degeneration. CONCLUSIONS: Dmp1 is the key factor in the formation of growth plates and secondary ossification center, and plays an important role in the process of bone and cartilage formation and bone nodule remodeling. Dmp1 may be the candidate gene that controls the development of mandible and cartilage.

Animals↗
PubMedDate not supplied

Distraction osteogenesis assisted by tissue engineering in an irradiated mandible: a case report.

Distraction osteogenesis (DO) can provide predictable bone regeneration without grafting procedures but requires long treatment time and forms less bone transverse to the direction of distraction. To promote 3-dimensional bone formation and shorten the consolidation period, tissue-engineered osteogenic material (injectable bone) was applied in a patient who was being treated with vertical DO with an osteocutaneous fibular flap to reconstruct the mandible. The material, which comprised autologous mesenchymal stem cells culture-expanded then induced to be osteogenic in character and platelet-rich plasma (PRP) activated with thrombin and calcium chloride, was infiltrated into the distracted tissue at the end of distraction and injected into a space created labially with a titanium mesh at implant placement. The infiltration contributed to full consolidation of the regenerate for 3 months, and the injection thickened the regenerated ridge and bridged a gap between the native mandible and distracted fibula. The reconstructed mandible was expanded from 10 mm to 25 mm in height despite a lacerated and opened labial periosteum in the distracted area. Six implants 18 mm in length were placed and subsequently achieved osseointegration. The cutaneous flap covering the implants was trimmed, and the palatal mucosa was transplanted to the regenerated ridge for vestibuloplasty. These raw surfaces were covered with PRP; within 3 weeks, they had attained an epithelium. The implants have supported a fixed prosthesis with adequate surrounding bone and attached mucosa. DO was assisted by tissue engineering and became effective in restoring the compromised mandible.

Blood Platelets↗