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At least 865 records · Page 48Linked to original sources
PubMed1991

Horizontal rotation of the condyle after sagittal split osteotomy of the mandible.

Displacement of the proximal segment of the condyle such that the condyle is no longer in its correct position has been cited as a major factor in postsurgical skeletal relapse after mandibular, sagittal split osteotomy. This study examined the effects of sagittal split osteotomy on the horizontal rotation of the condyle in 16 dissected mandibles for which clamp, screw, and wire fixations were used to advance the mandible or set it back. The results showed that, after sagittal split osteotomy, horizontal rotation usually occurred, regardless of the position of the distal segment or the type of fixation used. Our finding that 82% of the condylar angles increased after surgery indicates that the lateral pole of the condyle had rotated anteriorly, while the medial pole had rotated posteriorly. There were no consistent differences in horizontal rotation between the condyles on the side where the proximal segment had been fixed first and those on the side where it had been fixed second; nor did the sizes of the original intercondylar angles affect the magnitudes of change in the postoperative intercondylar angles. The only statistically significant difference (p = 0.005) between the angles after fixation by the three different methods was between screw and wire osteosyntheses when the distal segments were in the forward position. The reason for this difference is unclear.

Bone Screws↗
PubMed1992

The biomechanical effects of a sagittal split ramus osteotomy on the relationship of the mandible, the hyoid bone, and the cervical spine.

The effects of a sagittal split ramus osteotomy in correcting mandibular retrognathism and prognathism were studied cephalometrically in a group of 25 patients. The patients were divided into two groups, 18 patients with retrognathic mandibles and 7 patients with prognathic mandibles to be corrected by means of a sagittal split ramus osteotomy according to Obwegeser Dal Pont. The major complications of this type of surgical intervention have been documented in literature and are known as (1) a certain degree of relapse, i.e., mandibular instability and (2) the development of a permanently disturbed head balance. The displacement of the dental, skeletal, and neuromuscular components within the craniomandibular complex requires a large adaptive capacity and suggests that the patient will develop a forward head posture (anteroposition of the head) after both types of surgical intervention. In mandibular advancement, however, the initiating mechanism to develop a forward head posture starts in the cervicothoracic transition (C6-C7-T1-T2). In mandibular set-back, the discussed mechanism will start in the upper cervical area (C0-C1-C2-C3). The different pattern of movement of C2 and C3 in mandibular advancement and mandibular set-back, respectively, confirmed the conclusion that the initiating mechanisms, may be found in the cervicothoracic transition and the upper cervical region, respectively.

Adolescent↗
PubMed2005

Transverse growth of the maxilla and mandible in untreated girls with low, average, and high MP-SN angles: a longitudinal study.

INTRODUCTION: The purpose of this study was to investigate maxillary and mandibular transverse growth in untreated female subjects with low, average, and high mandibular plane angles longitudinally from ages 6 to 18. METHODS: Eighty-one untreated white girls with low (< or = 27 degrees , n = 16), average (> 27 degrees to < 37 degrees , n = 41), and high (> or = 37 degrees , n = 24) mandibular plane angles at age 6 were selected from the Bolton-Brush and Burlington Growth Studies. For each subject, longitudinal posteroanterior cephalograms at different ages (from ages 6 to 18) were traced, and the widths of maxilla and mandible were measured. All the measurements were converted by using a magnification factor of 8.5% (the subject-to-film distance was set at 13 cm). RESULTS: At age 6, the high-angle group had narrower maxillary and mandibular widths than the low-angle group, and this trend continued until age 18. From ages 6 to 14, maxillary width showed a steady and similar rate of increase for all 3 groups (0.90-0.95 mm per year), yet a plateau was reached at age 14 for all groups. Mandibular width increased at a steady rate (about 1.6 mm/year) for all 3 groups until age 14, and a plateau was reached for the high-angle group. For the low- and average-angle groups, mandibular growth continued from ages 14 to 18 but at a slower rate (0.85 mm and 0.39 mm per year, respectively). CONCLUSIONS: Vertical facial patterns (with low or high mandibular plane angles) might play a strong role in the transverse growth of the maxilla and the mandible.

Adolescent↗
PubMed2005

Relationship between masticatory function and internal structure of the mandible based on computed tomography findings.

INTRODUCTION: The purposes of this study were to investigate bone mineral density as a part of bone construction in human skulls and to examine the relationship between dentofacial morphology and masticatory function by using computed tomography (CT) findings. Changes in bone mineral density in the mandible because of loss of masticatory function were tested in rats by experimentally producing an environment that inhibited mastication by the molars. METHODS: Data for the human study were obtained from 27 modern male Japanese skulls (mean age, 28 years) from the University of Tokyo. Cortical bone thickness (CBT) and CT value (CV) were measured by each CT scan of the first and molars. For the animal study, a metal cap was inserted between the maxillary and mandibular incisors to prevent the molars from biting in 6-week-old male Wistar rats. The rats were killed after 2, 4, or 6 weeks, and bone mineral density was measured in cancellous and cortical bone equivalent to the first molar region by using peripheral quantitative computed tomography. RESULTS: In the human skull study, significant negative correlations were observed between CV in the regions of the buccal side of the second molar and the angle between the Frankfort horizontal and mandibular planes. Significant negative correlations were also observed between the gonial angle and CV in the buccal and basal sides. In the animal study, cancellous bone mineral density began to decline 4 weeks after the start of the experiment in the masticatory hypofunction group compared with the control group. By week 6, cancellous bone density had declined by 11.6% on the buccal side, 16.7% on the lingual side, 12.3% at the bifurcation of the root, and 38.1% at the root apex. Cortical bone density declined by 8% to 12% on the lingual side. CONCLUSIONS: The results support our hypothesis that a functional adaptive response by the mandible to mechanical stress resulting from mastication occurs not only in the muscle insertion area, but also in mandibular alveolar bone in the molar region.

Adaptation, Physiological↗
PubMed2004

Gene expression in the developing rat mandible: a gene array study.

To analyse the molecular events that occur in the developing mandible, gene arrays containing probes for 1176 known genes were used. Total RNA was extracted from the mandibles of 1- and 6-day-old rats. Radiolabeled probes were then synthesised and used to probe the DNA arrays. Of the 1176 genes examined, 306 were detectable, and the latter were analyzed by bioinformatics algorithms. K-means clustering grouped 72 genes into Up, 56 genes into Down and 178 genes into NO change. A large number of genes related to cell receptors (by ligands) were grouped into the Down cluster. Gene array technology appears to be a useful tool for studying the complex process of mandibular development.

Animals↗
PubMed2005

Ultrasound to stimulate early bone formation in a distraction gap: a double blind randomised clinical pilot trial in the edentulous mandible.

OBJECTIVE: In a double blind randomised clinical pilot trial, it was investigated whether low intensity pulsed ultrasound therapy stimulates early bone formation in a distraction gap created in a severely resorbed mandible. DESIGN: Eight patients underwent a mandibular vertical distraction over an average distance of 6.6+/-1.1mm. Ultrasound self-therapy or placebo therapy was started on the first day of distraction and continued daily until the implants were inserted. After 31+/-3.8 days of consolidation, the distraction device was removed, a transmandibular biopsy was taken, and two endosseous implants were inserted. RESULTS: All patients complied well with ultrasound therapy. During an average of 30.1+/-4.1 months follow-up, no complications did occur. Microradiographic examination of the biopsies revealed a comparable mean area of mineralised tissue in the distraction gap of 1.9+/-1.7mm(2) in the ultrasound treatment group and 1.9+/-1.3mm(2) in the placebo treatment group. Histological examination indicated that active woven bone was present within the distraction gap just adjacent to the osteotomy plane, with no apparent differences between the treatment groups. The lamellar bone formation outside the distraction gap appeared to have started as well. CONCLUSION: During a 31-day consolidation period, ultrasound treatment does not appear to stimulate bone formation in the severely resorbed vertical distracted mandible and it seems that this period is too short to evaluate properly if there is an effect. Therefore, a longer consolidation period has to be studied.

Aged↗
PubMed2005

Tissue-specific expression of Fgfr2b and Fgfr2c isoforms, Fgf10 and Fgf9 in the developing chick mandible.

Experimental evidence has demonstrated the importance of FGF signalling in morphogenesis of the mandibular processes. FGFs transmit their signals through four tyrosine kinase transmembrane receptors (FGFRs). Alternative splicing in FGFRs including FGFR2 generates different isoforms that exhibit different ligand-specificities, exclusive tissue distributions and specific biological functions. Despite extensive information regarding the isoform-specific patterns of expression Fgfr2c and Fgfr2b during morphogenesis of many organs, a comparative analysis of these specific isoforms in the chick mandible has not been reported. To better understand the function of FGFR2 in mandibular morphogenesis, we have analysed the expression Fgfr2b, Fgfr2c and their putative ligands Fgf10 and Fgf9, in the developing chick mandibular processes by in situ hybridisation and RT-PCR. Our observations show that Fgfr2b was primarily expressed in the mandibular epithelium while Fgfr2c was expressed in the mandibular mesenchyme including Meckel's cartilage. Fgf9 and Fgf10 were expressed in a variety of craniofacial regions including the mandibular epithelium and mesenchyme respectively. The temporal and spatial distributions of Fgfr2b, Fgfr2c, Fgf10 and Fgf9 in the developing mandible reported in this study make them attractive candidates for involvement in epithelial-mesenchymal signalling interactions that are known to be necessary for proper mandibular outgrowth and morphogenesis.

Animals↗
PubMed2006

Man as living bioreactor: fate of an exogenously prepared customized tissue-engineered mandible.

In 2004, we reported a novel method of repairing a human mandible by in vivo tissue engineering. The patient served as his own bioreactor as the exogenously prepared customized mandible replacement was grown inside his latissimus dorsi muscle prior to transplantation to repair the existing defect. Our technique was developed through extensive experience with an animal model. We describe our and the patient's experiences with this procedure. We give details to the benefits and limitations of this technique as it stands and outline issues that should be addressed in future human clinical trials.

Biopsy↗
PubMed2005

Distraction osteogenesis with subperiosteal devices in edentulous mandibles.

Nine patients with severely atrophic edentulous mandibles were treated by distraction osteogenesis with subperiosteal distractors for vertical augmentation of the anterior alveolar bone before insertion of implants. All the patients had severe complications and we conclude that the use of subperiosteal devices for vertical augmentation of edentulous mandibles is hazardous and offers no advantage over other surgical methods.

Adult↗
PubMed2005

Expression of bone morphogenetic protein-2 and proliferating cell nuclear antigen during distraction osteogenesis in the mandible in rabbits.

We examined the expression of bone morphogenetic protein-2 (BMP-2) and proliferating cell nuclear antigen (PCNA) during distraction osteogenesis in the mandible in rabbits. Twenty-four rabbits each had an osteotomy of the left mandibular body, and distraction devices were fixed. The bone was distracted at a rate of 1mm/day for 10 days. Four rabbits were killed at each of 1, 3, 7, 14, and 28 days after completion of distraction, and the mandibles examined radiographically, histologically, and immunohistochemically. Four rabbits that had not been operated on served as controls. Immunohistochemical analysis showed that BMP-2 and PCNA both appeared initially at the edge of the osteogenesis, but tended to disappear after 14 days. After 1, 3, 7, and 14 days after distraction, the ratio of stained cells was significantly higher than in the control group (p<0.05), during the period that active bone formation was shown radiographically and histologically. These results suggest that BMP-2 plays an important part in the induction of bone formation during distraction osteogenesis.

Animals↗
PubMed2006

Immediate mechanical stability of sagittal split ramus osteotomy fixed with resorbable compared with titanium bicortical screws in mandibles of sheep.

Ten fresh mandibles from adult sheep were stripped of all soft tissues and sectioned in the midline. We did sagittal split osteotomies and 5 mm advancement on all the 20 hemimandibles. Ten hemimandibles were fixed with three 2.0 mm x 13 mm titanium bicortical screws, and the other 10 were fixed with three 2.0 mm x 13 mm poly-l-lactic acid/polyglycolic acid (PLLA/PGA) bicortical screws in an inverted L pattern. All the hemimandibles were then mounted in a servohydraulic testing unit and tested to permanent deformation. Maximum forces that the mandibles resisted before breaking, maximum displacements, and the displacement values under 20, 60, 120, and 150 N were compared using the Mann-Whitney U-test. There were no significant differences in stability between the bones fixed with titanium and those fixed with resorbable screws.

Absorbable Implants↗
PubMed2005

Actinomycosis complicating fibula flap mandible reconstruction: a report of two cases.

Two patients undergoing fibula flap mandible reconstruction developed chronic intraoral wounds and salivary fistulae. After initial attempts at salvage, tissue biopsies demonstrated Actinomycosis infection. With antibiotic treatment and debridement, one reconstruction was salvaged while one was lost. Actinomycosis infection should be considered a possible agent in chronic wounds complicating mandible reconstructions with microsurgical flaps.

Actinomycosis↗
PubMed2006

Distraction osteogenesis in the irradiated rabbit mandible.

PURPOSE: The potential use of distraction osteogenesis in mandibular reconstruction has been limited by its questionable efficacy in previously radiated bone. The purpose of this study was to evaluate the effects of irradiation on mandibular distraction osteogenesis (DO). MATERIALS AND METHODS: Six rabbits received a unilateral irradiation (group R) in the mandible with a total dose of 27.0 Gy in five 5.4 Gy fractions (equivalent to 50 Gy/25 fractions). The contralateral side served as control (group C). Bilateral osteotomy was made 3 months after completion of irradiation. After a 1-week latency period bone distraction was activated at a rate of 0.5 mm twice daily for 8 days, followed by a consolidation phase of 6 weeks. New bone underwent radiographic, densitometric, histological and histomorphometric analysis. RESULTS: Two rabbits were excluded from the study, one due to infection on both sides and death in another animal. After 6 weeks of consolidation, the irradiation group had no significantly lower BMD than control group. No difference was found between the percent area of new bone in both groups. New bone was more mature and organised of group C than in groups R. Larger chondroid islands were found evident in distracted bone of group R than group C. CONCLUSIONS: It seems that DO can be feasible in previously irradiated rabbit mandible.

Absorptiometry, Photon↗
PubMed2006

Mandibular advancement and morphological changes in the mandibles of female mice of different ages.

Mandibular advancement (MA) by means of functional orthopedic techniques is currently used in young patients to stimulate mandibular growth. The aim of this study was to evaluate the morphological changes in the mandibles of 2-, 7-, and 16-month-old female mice after MA. Every 3 days during 1 month, the lower incisors were trimmed by 1mm to induce protrusion when the animal was feeding. The left mandibles of the 30 experimental and 28 control individuals were subsequently dissected and digital images were obtained to analyze nine linear/angular measurements. The condylar microstructure was also analyzed by scanning electron microscopy (SEM). The linear/angular measurements showed a growth response in different mandibular regions in 2- and 16-month-old individuals. SEM showed that, in the 7-month-old mice, the condylar cartilage had regenerated in the treated individuals but not in the controls. The results suggest that MA produces mandibular growth in 2- and 16-month-old female mice. Although there was no mandibular growth in 7-month-old mice, regeneration of the condylar cartilage was detected, thus demonstrating that different responses to the MA stimulus occur in female mice of different ages.

Aging↗
PubMed2004

Neurosensory deficits after bilateral sagittal split ramus osteotomy of the mandible--influence of soft tissue handling medial to the ascending ramus.

Deficits in the neurosensory function (NF) of the inferior alveolar nerve (IAN) are often encountered after bilateral sagittal split osteotomy of the mandible. A prospective follow-up study was performed to examine the long-term effect of especially gentle handling of the soft tissues on the medial side of the ascending ramus. After the initial incision, the soft tissues of the ramus were either retracted extremely gently and minimally (test side) or, as was the earlier routine, more widely (contralateral control side). NF was tested with 2-point discrimination (2-PD) and vitality scanner tests (VST) preoperatively and four times postoperatively up to 1 year. Patients' subjective sensations were also assessed. The results showed a difference between the sides, which was most distinct at the 6-month follow-up (P=0.028) measured with VST, while 2-PD did not show any statistical differences. Our findings support the earlier intraoperative neurophysiologic reports that dissection trauma to the IAN around the mandibular foramen may cause NF deficits in the IAN even before the actual splitting of the mandible. Therefore, minimal distraction of the soft tissues in the ramus is indicated. Higher age is an evident risk factor, and subjective sensation correlates with 2-PD in the lower lip.

Adipose Tissue↗
PubMed2005

Implications of radiation dosimetry of the mandible in patients with carcinomas of the oral cavity and nasopharynx treated with intensity modulated radiation therapy.

Intensity modulated radiation therapy (IMRT) is a newer method of delivering highly conformal, salivary gland sparing radiation treatment that is finding increasing applications in head and neck malignancies. However, the radiation dose distribution to the mandible is rarely considered with IMRT, and the potential risks of osteoradionecrosis or osseointegrated implant failure are not well characterized for this modality. In a series of 10 patients with oral cavity and nasopharyngeal cancers who previously underwent IMRT, examination of the three-dimensional mandibular dose distribution was undertaken. The findings indicate a modest potential risk of osteoradionecrosis and osseointegrated implant failure in cases where IMRT optimization constraints are not specifically aimed at sparing the mandibular bone. Significantly higher mandibular doses (P < 0.04) were received in cases of oral cavity as opposed to nasopharyngeal cancers with IMRT. Efforts to optimize IMRT to further reduce doses to the mandible should be considered, and development of software tools to integrate three-dimensional dose distributions into planning of post-radiotherapy osseointegration would be beneficial.

Carcinoma↗
PubMed2005

The use of SPECT to evaluate growth cessation of the mandible in unilateral condylar hyperplasia.

In unilateral condylar hyperplasia, for surgical intervention to be effective, the status of condylar bone growth has to be assessed correctly. Previously this assessment relied on serial clinical observations. This study aimed to evaluate the MDP-SPECT method of assessing condylar growth in unilateral condylar hyperplasia. Twenty-six MDP-SPECT of the mandible had been performed; 21 were diagnosed as condylar hyperplasia and five as non-mandibular disease. Three isotope parameters: isotope counts, pixel counts and counts per pixel were summed for each condyle per subject. The percentage difference in isotope uptake of the three parameters between the two condyles was calculated as the ratio of the combined counts of the two sides. These differences significantly correlated with each other (Pearson r=0.78-0.98) and with the clinical status of bone growth (Spearman rho=0.72-0.86). There was a significant difference for the count per pixel between the 'growing' condyle (transaxial, T: 15.05+/-7.14, coronal, C: 12.29+/-7.88), the 'no further growth' condyle (T: 5.22+/-4.08, C: 5.67+/-3.88) and the 'normal' condyle (T: 0.82+/-0.76, C: 1.34+/-0.66). This method was able to separate 'active growth' from 'growth cessation' of the condyle by a single MDP-SPECT of the mandible. However, further studies are needed to confirm this finding.

Adult↗
PubMed2005

Response of diffuse sclerosing osteomyelitis of the mandible to alendronate: follow-up study by 99mTc scintigraphy.

We report a case of diffuse sclerosing osteomyelitis of the mandible responded to alendronate, after a poor response to intravenous antibiotics, antibiotic irrigation-perfusion, and decortication. The patient was given an intravenous infusion of 10mg of alendronate. Pain resolved within 24 h. There were no severe adverse events. Increased uptake of 99mTc in the mandible almost completely disappeared 3 months after treatment.

Adult↗