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At least 217 records · Page 12Linked to original sources
PubMed2001

Clinical application of a new compact CT system to assess 3-D images for the preoperative treatment planning of implants in the posterior mandible A case report.

When treatment planning before placing dental implants in the posterior region of the mandible, the locations of the inferior alveolar nerve and mental foramen need to be ascertained, as they determine the bone height available and the implant length selected. The purpose of this study was to introduce the clinical application of a newly developed compact computed tomography system (Ortho-CT) to assess three-dimensional (3-D) images for the preoperative treatment planning of implants in the posterior region of the mandible. To evaluate the 3-D images, we scanned using the Ortho-CT system the mandible with a radiopaque template placed in the posterior region. The Ortho-CT images provided excellent information for evaluating the morphology of the mandible, and for showing the location of the inferior alveolar nerve, mental foramen and the relationship of the template to the bone. We consider that Ortho-CT is a useful aid to preoperative treatment planning of implant therapy in the mandible.

Contrast Media↗
PubMed2002

Restoration of occlusal function using osseointegrated implants in the canine mandible reconstructed by rhBMP-2.

Bone morphogenetic proteins have been found to be one of the most promising osteoinductive substances and they are expected to be utilized clinically for the reconstruction of defective mandibles. However, newly formed bone induced by recombinant human bone morphogenetic protein-2 (rhBMP-2) has not yet been proven able to withstand the masticatory force applied by oral implants. In this study, we examined the qualitative changes in an rhBMP-2-induced mandible from the functional force of osseointegrated oral implants. Segmental (30 mm) bone defects were created in the mandibles of beagles. A poly D,L-lactic coglycolic acid-coated gelatin sponge impregnated with rhBMP-2 was grafted to the resected canine mandible. The new bone was formed 8 weeks after surgery and the Brånemark system fixtures were implanted into the reconstructed mandible. After another 8 weeks, the prosthesis was placed over the oral implants. The prosthesis was maintained in occlusion with the opposing natural dentition for 0, 4, 12, 24, or 48 weeks before the animal was euthanized. The quality of regenerated bone was then evaluated histologically and the osseointegration ratio between oral implants and the bonemeasured. During the first 4 weeks, the ratio remarkably increased from 48.9% to 64.5%. After 48 weeks, the ratio approached about 74.5%. The bone loaded for 48 weeks had undergone extensive remodeling and consolidation; its quality was better and maturer than that of bone that was not loaded. These results indicated that the newly formed bone induced by rhBMP-2 was able to withstand the masticatory force applied by oral implants and had become as functionally mature as a natural bone.

Analysis of Variance↗
PubMed2002

Staged reconstruction of the severely atrophic mandible with autogenous bone graft and endosteal implants.

PURPOSE: Vastly different surgical techniques have been advocated for osseous reconstruction of the severely atrophic mandible. Endosseous implants placed in autologous bone grafts have been proposed to minimize graft resorption and restore function; however, sufficient bone must exist to support the implants and prevent pathologic fracture. The purpose of this retrospective analysis was to assess the efficacy of autologous bone grafting and the subsequent placement of endosteal implants as a staged procedure in patients with severely atrophic mandibles. MATERIALS AND METHODS: The records of all patients presenting to The University of North Carolina for treatment from 1997 to 1999 with atrophic mandibles (vertical mandibular height <7 mm as measured on panoramic radiographs in at least 1 site at the mandibular midline and at the thinnest portion of the mandibular body) were reviewed. Bone height was assessed preoperatively, immediately postoperatively, at the time of implant placement (4 to 6 months), and again at 12 and 24 months after bone grafting from posterior iliac crest to the mandible via an extraoral approach. Five endosteal implants were subsequently placed in each patient as a delayed procedure 4 to 6 months after bone grafting, and prosthetic rehabilitation was completed with implant supported prostheses. RESULTS: Fourteen consecutive patients were identified with a median preoperative bone height of 9 mm (interquartile range, 25th to 75th percentile [IQ], 7 to 10 mm) in the mandibular midline and 5 mm (IQ, 2 to 5 mm) in the body region. There were no perioperative complications. Median estimated blood loss during the bone graft procedure, as estimated by the surgeon and the anesthesiologist, was 300 mL (IQ, 150 to 1,100 mL), and 1 patient required blood transfusion secondary to symptomatic anemia. The mean loss of vertical bone height after grafting and during the 4 to 6 months before implant placement was 33%. After implant placement and at 12 months, the vertical bone loss was negligible in the implant-supported region and less than 11% in the body region. CONCLUSION: Reconstruction of the severely atrophic mandible using autogenous corticocancellous bone grafts followed by placement of osseointegrated implants in 4 to 6 months can restore and maintain mandibular bone sufficient to support implants and facilitate successful restoration of occlusion. A prospective study is planned to identify predictors of successful outcomes compared with other surgical/prosthetic treatment.

Adult↗
PubMed2002

The effect of a unilateral costochondral graft on the growth of the marmoset mandible.

PURPOSE: The purpose of the investigation was to examine growth of the mandible after costochondral grafting with special reference to the amount of cartilage included in the grafts. MATERIALS AND METHODS: The material consisted of 5 growing and 3 adult marmoset monkeys, Callithrix jacchus, in which the condylar process was removed unilaterally and replaced with a costochondral graft (CCG) containing either a short or long cartilage end. Growing animals were followed for 15 months until they attained maturity; and adult animals were followed for 13 months. Measurements made on frontal radiographs performed bimonthly, and direct measurements made on dry mandibles and crania at the end of the experiment, were used to evaluate the growth of the mandible and glenoid fossa. RESULTS: Longitudinal cephalometric evaluation revealed a gradual deviation of the lower dental midline to the unoperated side in growing monkeys with a long cartilage transplant. In all other animals, virtually no midline deviation occurred. Measurements on dry mandibles showed that the length and ramus height were longer in growing animals with long cartilage transplants compared with those with short cartilage transplants. In adult animals, the amount of cartilage did not make any difference with regard to the mandibular measurements. Enlargement of the articulating head on the grafted side was recorded in all animals. A morphologic change in the glenoid fossa of growing monkeys with a long cartilage transplant was also noted. CONCLUSIONS: The findings of this investigation indicate that depending on the amount of cartilage in a unilateral CCG, a tissue-separating force is generated in growing monkeys, capable of propelling the mandible to the unoperated side. This gradual overgrowth occurs during the entire growth period, indicating a strong hormonal and growth factor influence on the growth process. Jaw function may have an effect on the articulating surface of the CCG, seen as enlarged articulating head on the grafted side in all animals.

Adaptation, Physiological↗
PubMed2002

Functional reconstruction of the non-human primate mandible using recombinant human bone morphogenetic protein-2.

The purpose of this study was to evaluate the long-term functional properties of regenerated bone induced by recombinant human bone morphogenetic protein-2 (rhBMP-2) in segmental bone defects of primate mandibles. The 30-mm defects were created in the mandibles of six young monkeys and the mandibles were fixed with titanium plates. Then 9 mg of rhBMP-2 permeating a poly-D, L-lactic-co-glycolic acid-coated gelatin sponge (PGS) was implanted into the bone defect. Dental implants were placed into the regenerated mandible 20 weeks after surgery, then suprastructures were placed and masticatory force loading was begun 8 weeks after the insertion of the dental implants. Bone formation and the quality of new bone were evaluated radiologically and histologically at 15 and 30 weeks after surgery, and 4 and 24 weeks after masticatory force loading. The resected mandibles were completely regenerated with the rhBMP-2-induced bone. Excellent remodelling and consolidation of new bone were observed after loading. This study demonstrated that the new bone induced by rhBMP-2 in large segmental defects was maintained and functional for at least 1 year. Bone regeneration induced by rhBMP-2 holds promise as a future therapy and may be an effective alternative to autogenous bone grafts for implant dentistry and reconstructive surgery.

Absorbable Implants↗
PubMed2000

Experimental and finite element study of a human mandible.

Knowledge of the complex biomechanical behaviour of the human mandible is of great importance in various clinical situations. Various approaches can be used to evaluate the physical behaviour of bony specimens. In the course of this study, we investigated mandibular deformation under mechanical loads in an experimental setting and compared them with results derived from finite element analysis (FEA). A special apparatus was developed to apply various forces under defined conditions on an explanted human mandible in vitro. Strains on the surface of the mandible were measured with strain gauges and subsequently a voxel based finite element mesh was generated. Strain patterns of the mandible were calculated in the FE analysis and matched with the experimental data. Comparing the numerical with the experimental data, we found a good correlation between in vitro measurements and mathematical modelling (correlation coefficient = 0.992). Then the FE model was used to evaluate mandibular biomechanics relative to aspects of load transfer, stress distribution and displacements. It is concluded that the applied procedure of generating the FE model is a valid and accurate, non-invasive method to predict different parameters of the complex biomechanical behaviour of human mandibles.

Biomechanical Phenomena↗
PubMed1991

[Hyperbaric oxygen in the treatment of osteoradionecrosis of the mandible].

Osteoradionecrosis (ORN) of the mandible is one of the most dreaded complications in the treatment of cancer of the head and neck. If conservative and surgical treatment have not been successful, very often the only remaining solution is surgical intervention into the bone continuity of the mandible. In a group of eight patients suffering from ORN of the horizontal ramus of the lower jaw we gathered first experiences with hyperbaric oxygen therapy in combination with an operation to preserve the bone continuity (debridement of the bone and closing of the soft tissues). Hyperbaric oxygen was given during a time span of 13 to 52 hours (average: 36 hours). It was only with those two patients who received more than 50 hours of hyperbaric oxygen therapy that we achieved our aim of "total recovery from ORN of the mandible while saving its bone continuity". In one case where there was no clinically manifest recidivation of the tumour, the tumour showed rapid growth under hyperbaric oxygen therapy. In three cases partial resection of the mandible had to be performed without reconstruction for cure of ORN. Despite the loss of bone continuity these patients are only slightly cosmetically impaired and nutrition causes no problems. In two patients ORN still exists. On the basis of our first experiences with a small group of patients and in accordance with various publications, we conclude that hyperbaric oxygen therapy is a significant adjunct in the treatment of the mandible if a well-founded diagnosis is established and if it is followed by a well-adjusted therapy.

Adult↗
PubMed1983

The effect of prenatal protein-energy malnutrition on the development of mandibles and long bones in newborn rats.

To evaluate the role of gestational protein-energy malnutrition on fetal hard-tissue growth and metabolism, we measured several variables in the growth centres of mandibles and long bones of newborn rats. Control pups and pups of malnourished dams had approximately the same extent of reduction in body-weight, mandibular weight and long-bone weight. The malnourished group had more cells in the mandible although cell size was the same as that of controls. In contrast, in the long bones, the malnourished group had fewer cells than did controls whereas cell size was unchanged. Calcium content was the same in long bones of both groups, but was less in the mandibles of pups from malnourished dams. Ca metabolism as measured by 45Ca uptake was unchanged in the long bones, but was increased in the mandibles of the malnourished group shortly after birth. Calcification patterns at birth in these bones correlated well with alkaline phosphatase (EC 3.1.3.1) activity. These findings indicate that the mandibles and long bones of offspring are affected differently by protein-energy malnutrition during the mother's gestation. Prenatal nutritional stress resulted in a disturbance of the pituitary-adrenal system. Increased adrenal corticosterone could possibly be related to the different observed changes in bone metabolism.

Animals↗
PubMed2000

Variation in mandible shape in Thrichomys apereoides (Mammalia: Rodentia): geometric analysis of a complex morphological structure.

The model of development and evolution of complex morphological structures conceived by Atchley and Hall in 1991 (Biol. Rev. 66:101-157), which establishes that changes at the macroscopic, morphogenetic level can be statistically detected as variation in skeletal units at distinct scales, was applied in combination with the formalism of geometric morphometrics to study variation in mandible shape among populations of the rodent species Thrichomys apereoides. The thin-plate spline technique produced geometric descriptors of shape derived from anatomical landmarks in the mandible, which we used with graphical and inferential approaches to partition the contribution of global and localized components to the observed differentiation in mandible shape. A major pattern of morphological differentiation in T. apereoides is attributable to localized components of shape at smaller geometric scales associated with specific morphogenetic units of the mandible. On the other hand, a clinical trend of variation is associated primarily with localized components of shape at larger geometric scales. Morphogenetic mechanisms assumed to be operating to produce the observed differentiation in the specific units of the mandible include mesenchymal condensation differentiation, muscle hypertrophy, and tooth growth. Perspectives for the application of models of morphological evolution and geometric morphometrics to morphologically based systematic biology are considered.

Animals↗
PubMed1986

Genetic variation in the shape of the mouse mandible and its relationship to glucocorticoid-induced cleft palate analyzed by using recombinant inbred lines.

Variation in mandible shape has been investigated in a set of recombinant inbred (RI) lines of mice, the C57BL/6J X A/J (BXA;AXB) RI lines. Considerable genetic variation was detected between the RI lines, but most lines were intermediate in shape when compared with the parent lines. Variation in mandible shape could not be explained by any single gene differences known between the parent lines including the H-2 locus. Some RI lines had mandible shapes unlike either parent, and one in particular, line BXA1, had an unusual shape with a pronounced condyloid process. It was concluded that mandible shape has a complex inheritance involving a number of genes, each with small effects. In some cases, recombination of the genes can produce bone shapes quite different from those of the original parent line.--There was no evidence that the variability in steroid-induced cleft palate incidence in the BXA;AXB RI lines is related to the variation in adult mandible shape as detected in this study.

Animals↗
PubMed1977

Effect of protein-energy malnutrition on the growth of mandible and long bone in newborn male and female rats.

Several parameters were measured in the growth centers of mandible and long bone of rat pups suckled on dams fed 25% or 6% protein diets. No sex-related differences were found in any parameter either during normal growth or in response to malnutrition. While the total contents of protein, DNA, RNA and calcium were reduced in both tissues, mandible was less affected than long bone, although it appeared to be affected earlier. Moreover, malnutrition reduced the number of cells in the mandible without changing cell size or calcium content. In contrast, long bone appeared to be affected later than mandible, and to be modified differently. In this case, not only cell number, but also cell size and cellular content of calcium were reduced. The results can be interpreted to mean that the critical periods of growth for mandible and long bone are different. Moreover, some suggestion of differences in relative sensitivity to malnutrition of these two hard tissues was also observed.

Age Factors↗
PubMed1979

Physical and biochemical changes of the mandible and long bone in protein-energy malnourished newborn rats.

The activities of alkaline and acid phosphatases, the linear dimensions and volumes of mandibles and long bones, and the level of calcitonin in serum of rat pups suckled on dams fed 25 or 6% protein diets were determined. In both mandibles and long bones, alkaline phosphatase activity corresponded to the calcification pattern, and acid phosphatase activity paralleled organic matrix formation. The calcitonin level in blood serum of the malnourished pups differed from that of controls only on day 5. The linear dimensions and volume were consistently more affected in long bones than in mandibles. These results may be explained in terms of the critical growth periods of these bones. In the mandible, the critical growth period appears to occur prenatally, whereas in the long bone it occurs postnatally, when the nutritional stress of this experiment was applied. Long bones were thus generally more affected than mandibles.

Acid Phosphatase↗
PubMed2005

Congenital fusion of the maxilla and mandible.

Congenital fusion of the maxilla and mandible (syngnathia) is rare and can present in a wide range of severity from single mucosal bands (synechiae) to complete bony fusion (synostosis). Congenital synostosis of the mandible and maxilla is even less common than synechiae, with only 25 cases reported in the literature. Most of them presented as an incomplete, unilateral fusion. A 4-year-old boy was referred to the authors' emergency unit with asphyxia after vomiting. The authors found the child could not open his mouth. His upper and lower jaws were fused, with only a 2- to 3-mm gap in the anterior part. X-rays and computed tomography scans showed that there was a bony fusion of the ramus of the mandible to the zygomatic complex and the posterior part of the maxilla. In addition, there was significant mandible hypoplasia. After performing an osteotomy (to treat the fusion between the bilateral ramus mandible, maxilla, and zygoma), the authors performed a temporomandibular joint reconstruction using a silicon block. After the completion of these procedures, they observed that the mouth could be opened 32 mm. After 2 years of mandibular lengthening performed with an external distracter, the patient's facial appearance and occlusion became more acceptable. An extremely rare case is described, and the existing literature is reviewed.

Child, Preschool↗
PubMed2003

Mechanisms of cancer invasion of the mandible.

There is little evidence that the tumor enters the mandible preferentially through the occlusal surface, the periodontal membrane, or named foramina. Tumor enters the mandible at the point of contact, which is often at the junction of the attached and reflected mucosa, which lies below the crest of the ridge in all but grossly resorbed mandibles. Angulation of the bone cut in rim or marginal resection of the mandible is advised. The erosive pattern of disease is associated with shallow mandibular invasion and smaller tumors in the soft tissue. This finding supports the principle of marginal resection in such cases. There is little evidence to support the principle that the tumor spreads preferentially along the inferior alveolar nerve or the bone marrow. The inclusion of the neurovascular bundle in marginal resections of the mandible is not necessary. Preoperative assessment should include plain radiography combined with a sensitive scan (bone scintigraphy, single photon emission computerized tomography, or MRI) and inspection of the bone surface after periosteal stripping at the time of the resection.

Female↗
PubMed2004

Distraction osteogenesis of the porcine mandible: histomorphometric evaluation of bone.

Distraction osteogenesis is a technique for skeletal lengthening that exploits the body's innate capacity for bone formation in response to tension forces on the repair callus. The authors developed a distraction osteogenesis model with a semiburied device in the Yucatan minipig mandible because of similarities between human and porcine mandibular anatomy, temporomandibular function, chewing patterns, and bone turnover rates. The purpose of this study was to measure histomorphometric bone fill after different latency periods, rates of distraction, and duration of neutral fixation in the minipig mandible. In addition, the relationship between histomorphometric bone fill and clinical stability was investigated. Mandibular osteotomies in 20 female Yucatan minipigs weighing 25 to 30 kg were distracted with modified semiburied distraction devices. Variables included 0-day or 4-day latency; 1-mm, 2-mm, or 4-mm daily distraction rates; gap size of 7 or 12 mm; and evaluation after neutral fixation for various lengths of time. Specimens were fixed in 2% paraformaldehyde, pH 7.4, before being embedded in methylmethacrylate. Sections were prepared from the region just below the inferior alveolar canal. The area of new bone formation within the gap was measured and expressed as a percentage of the total area of the distraction gap. Bone fill ranged from 0 to 100 percent. A pilot study with 7-mm advancements showed similar bone fill with 0-day or 4-day latency, but with poor reproducibility. Mandibles that were distracted to 12 mm at 1 mm per day exhibited nearly complete bone fill, either with 0-day latency (average, 93 percent) or 4-day latency (average, 100 percent). Mandibles that had been distracted for 3 days at 4 mm per day showed moderate osteogenesis and clinical stability with increasing time of neutral fixation. Bone fill was significantly correlated with clinical stability (Spearman r = 0.801, p = 0.001). Histological examination showed exuberant periosteal osteogenesis in distracted mandibles, even in those that showed poor bone fill and clinical stability. Thus, the periosteum appears to be a major source of new bone formation. These results show that osteogenesis was nearly complete with 1 mm per day and 0-day or 4-day latency. These results are consistent with the authors' previously reported clinical and radiographic observations that a latency period is not necessary for successful healing of the mandibular distraction osteogenesis wound.

Animals↗
PubMed2005

The determinants of successful distraction osteogenesis of the mandible in hemifacial microsomia from longitudinal results.

The purpose of this study was to investigate sagittal, vertical, asymmetric skeletal characteristics that could determine successful distraction osteogenesis (DO) of the mandible in patients with hemifacial microsomia using longitudinal follow-up data. Lateral and posteroanterior cephalometric radiographs before DO (T0), after DO (T1), and after retention (T2) were analyzed to investigate initial skeletal characteristics, DO effect, and retention. From the measurements at T2, patients were classified into group 1 (good retention results, N = 10) and group 2 (poor results, N = 9). Sagittal, vertical, dental, and asymmetric variables were measured. The differences at each stage and during T0-T1 and T1-T2 between two groups were compared by Mann-Whitney u test, Wilcoxon signed rank test and ANOVA test. Pruzansky type significantly influenced the success or failure of DO. At T0, group 2 showed more retrognathic mandible, smaller ramus height, larger gonial angle, more inward ramus inclination of the affected side, and more chin point deviation to the affected side than did group 1. The major effects of DO on group 1 were lengthening of the ramus height, forward positioning of the mandible, increase of gonial angle, counterclockwise rotation caused by a decrease of the articular angle, increase of ramus inclination of the affected side, and improvement of occlusal canting and chin point deviation. However, by DO, group 2 showed clockwise rotation of the mandible, and less increase of the ramus height than did group 1. After retention, group 2 showed counterclockwise rotation of the mandible and little growth of the ramus height. Group 1 showed reverse tendency. These factors could contribute to the difference in long-term results between two groups.

Analysis of Variance↗
PubMed1990

Regulation of alkaline phosphatase and alpha 2(I) procollagen synthesis during early intramembranous bone formation in the rat mandible.

We have studied intramembranous bone formation in the developing rat mandible. In this system discrete developmental stages can be readily distinguished: mesenchymal condensation, osteoid deposition, and mineralization. In mandibles of 14-day rat embryos avascular condensed mesenchymal cells can be discerned in a region lateral to Meckel's cartilage and anterior to the first molar bud. In 18-day embryos primary bone structures with mineral deposition are evident, and at 2 days postnatally the mandible is extensively mineralized. In the developing mandible we investigated the pattern of bone/liver/kidney/placenta (BLKP) alkaline phosphatase (ALP) and alpha 2(I) procollagen expression in the differentiating osteoblasts. The level of ALP activity in loose mesenchymal tissue is close to background levels. In contrast, the condensed mesenchymal cells in 14-day embryos, which will subsequently form bone, display intense ALP activity prior to discernible osteoid or mineral deposition. ALP activity in the condensed mesenchymal cells can be inhibited by levamisole, indicating activity of the BLKP gene product. We could not detect a corresponding increase in transcript level for either ALP or alpha 2(I) in the condensed mesenchyme in 14-day embryo using in situ hybridization, probably due to low message abundance. At 18 days, cells throughout the developing mandible express ALP activity, and intense in situ hybridization to BLKP ALP probes is evident in cells lining the developing bone trabeculae. Alpha 2(I) procollagen transcripts have accumulated in cells of the developing mandibular bone, but are not specifically localized to osteoblastic cells. Our results demonstrate that ALP activity is a very early marker of differentiation of cells of the osteogenic lineage, since a marked increase in ALP enzyme activity is clearly detectable in condensed mesenchymal cells prior to osteoid or mineral deposition. In contrast, Wright and Leblond, using the same model system and immunohistochemistry, could not localize type I collagen to preosteoblastic cells surrounding the developing bone trabeculae, and demonstrated localization of type I collagen to osteoblasts bordering developing trabeculae, indicating a substantial increase in type I collagen expression (at least at the protein level) during preosteoblast to osteoblast differentiation. These results indicate a discrete pattern of regulation for both the ALP and alpha 2(I) genes during osteogenic differentiation, which may involve both transcriptional and posttranscriptional regulation.

Alkaline Phosphatase↗
PubMed2006

Incidence of mylohyoid bridging in 13th century Byzantine mandibles.

Mylohyoid bridging on the mandible is a hyperostotic variation considered as one of the cranial non-metric characteristics. Most researchers have indicated that such non-quantitative traits can be used for the investigation of population history and these traits show differences according to societies. In the present study, we investigated the incidence of mylohyoid groove bridging on 89 half-mandibles (48 right sides, 41 left sides; 39 complete mandibles, nine right and two left half-mandibles) from the Byzantine period, dated approximately eight centuries back. We observed that the incidence of mylohyoid bridging was 8.9% for the Byzantine mandibles with no side predilection. The incidence of bridging observed in the present sample was compared with those of earlier studies. Mylohyoid bridging may be useful as a non-metric feature in population studies when used in combination with other characteristics.

Adult↗