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PubMed1991

Quantitative description of the shape of the mandible.

The purpose of this study was to provide quantitative data on the shape of the mandible at the period around the pubertal growth spurt and to test the hypothesis that early mandibular shape may influence the amount and direction of subsequent mandibular growth. Longitudinal data from lateral cephalograms of 55 white female and 39 white male subjects were used. The mandibular outline from articulare to gnathion was analyzed into cosine curves, according to the Fourier equation. The resulting Fourier coefficients, representing mandibular outline shape, were analyzed statistically in relation to age, sex, craniofacial pattern, and mandibular growth rotation. Statistically significant growth changes of the Fourier coefficients were observed, especially during the postpubertal period, indicating a decrease in the gonial angle with age. Sex-related differences in shape were observed at all ages, male subjects showing a more rounded shape of the mandible than female subjects. Mandibular shape, as represented by the Fourier coefficients, was correlated to cephalometric variables, indicating mandibular inclination, but only poorly to cephalometric variables, indicating anteroposterior jaw relation. Total rotation of the mandible during growth could not be predicted by mandibular shape.

Cephalometry↗
PubMed1994

Individual augmentation of the atrophic mandible based on CAD/CAM-manipulated computed tomography data--in vitro results.

The problems of shaping a stable alveolar ridge form favorable for prosthodontic treatment by the various methods of ridge augmentation raise the question of whether computer-aided design (CAD) may be used for geometric modeling of the implant. Helical computed tomography (CT) data were used to create a three-dimensional (3-D) model of the atrophic mandible. This numerically based model served as the basis for a free-form-surface design of the implant's form, height, and position. The idealized data required for this geometric modeling were also derived from numerically based serial sections of 104 mandibles of dried skulls. The modeling procedure followed the formula "idealized mandibular geometry minus patient's geometry", yielding the geometric data of the implant. These numerically control (NC) a milling machine to fabricate the individual implant. The augmentation of an atrophic mandible of a dried skull is presented as the first in vitro trial of this new method.

Alveolar Bone Loss↗
PubMed1992

Distraction osteogenesis of the mandible. An experimental study on sheep.

Distraction bone healing has been studied in long bones but there are only few experiments reported in relation to the mandible. The histological pattern of the healing process after mandibular distraction is described. After osteotomy the mandibles of 17 growing sheep were lengthened by gradual distraction using an external fixation device. The follow-up varied from 0 to 52 weeks. The results indicate that bone healing in mandibles is principally the same as in long bones. Four phases can be observed during the repair process: 1) formation of collagen aligned in the direction of distraction, 2) bone formation over the collagen template, 3) bone union across the distraction gap, and 4) remodelling of the lengthened segment. Some increased osteoblast activity was also seen in the control side.

Animals↗
PubMed1996

The role of magnetic resonance imaging and scintigraphy in the diagnosis of pathologic changes of the mandible after radiation therapy.

A prospective study of 85 patients with oral cancer, treated with high-dose radiation therapy, was performed to assess the value of magnetic resonance imaging (MRI) and scintigraphy for diagnosis of pathologic changes in the mandible. During postradiotherapeutic monitoring, radiation osteomyelitis occurred in 12 cases, tumor recurrences infiltrating the mandible in five cases, and progressive periodontal disease in nine cases. MRI permitted early diagnosis of radiation osteomyelitis in 11 out of 12 cases; only two cases were false positive. In scintigraphy with 99mTc-HDP, all alterations of the mandible, such as osteoradionecrosis, tumor infiltration, and periodontitis, showed a high uptake, resulting in a sensitivity of up to 100%, but a low specificity of 57%. Scintigraphy permitted assessment of the extension and location of the lesions. Both methods were superior to conventional radiography and clinical examination and should be integrated into a comprehensive follow-up program after radiation therapy.

Adult↗
PubMed1997

Treatment of chronic suppurative osteomyelitis of the mandible.

Chronic suppurative osteomyelitis of the mandible is often considered difficult to treat and may lead to refractory osteomyelitis. Sixteen patients with chronic suppurative osteomyelitis of the mandible were treated with a relatively simple protocol, consisting of sequestrectomy or decortication and i.v. antimicrobial therapy for one week, followed by oral penicillin for three weeks. Only one case showed recurrence of symptoms, which was treated successfully in a second session. It is concluded that combined surgical and antimicrobial therapy should be sufficient to cure most cases of chronic suppurative osteomyelitis of the mandible.

Administration, Oral↗
PubMed1998

Functional reconstruction of the mandible: a modified titanium mesh system.

This paper describes a method for mandibular reconstruction utilizing autogenous cancellous bone in a titanium mesh. The mesh is designed preoperatively based on a duplicate of the patient's mandible which is modified to simulate an anatomically correct edentulous segment in the region to be reconstructed. The duplicate mandible is articulated with a maxillary dental cast, and a locating splint is fabricated for intraoperative use to aid the positioning of the mesh in relation to the upper teeth. The method facilitates future rehabilitation with dental implants and results in a symmetric and highly functional reconstruction of the mandible.

Adult↗
PubMed1992

Proteinase, phosphatase and glucuronidase activities in the growing mandible and temporomandibular joint of the guinea pig.

This study investigated the effect of muscle function and occlusal form on the activity levels of several enzymes present in the mandible or temporomandibular joint of the guinea pig. Restriction of maxillary width and asymmetric function of the mandible was caused in 12 animals at the age of 10 days, as described in the accompanying paper (Isotupa et al. 1992). Tissue samples from six anatomical sites were obtained from the animals sacrificed 4, 8, or 12 weeks after manipulation (4 animals in each group). Six age-matched animals acted as controls. Five samples were from the following sites of the mandible: the condylar cartilage, the lower and upper parts of processus angularis, and the anterior and posterior halves of the condyle neck. A sample was also obtained from fossa mandibularis of the temporal bone. Buffer extracts of powderized samples were studied for acid and alkaline phosphatase, glucuronidase and two types of proteolytic activity. Although the asymmetric manipulation of occlusion caused observable, localized asymmetric growth, the enzyme findings were not consistently asymmetric. Manipulation generally increased all enzyme activities regardless of whether apposition or resorption was involved. The activities of alkaline phosphatase more consistently showed this pattern, and changes in enzyme activities seemed to be sensitive, reflecting cellular or molecular level of growth. The enzyme activities may also reflect a certain type of after-effect of irritation, or a healing period. The inclusion of several types of enzyme determinations is recommended to complete macroscopic measurements. Subsequent chromatographic and electrophoretic studies are also useful.

Acid Phosphatase↗
PubMed1997

The medial axis branch point in the human mandible.

The medial axis method was applied to radio-cephalometric images of the mandible in 20 adults and 18 children and to panoramic X-ray images of these children, and also directly to 50 halves of dry mandibles. It was found that the location of the posterior branch point coincided almost invariably with the mandibular foramen/lingula. The foramen may be regarded as the posterior limit of the mandibular body, from which the condylar and coronoid processes branch off. The medial axis appears to reflect the developmental and functional anatomy of the human mandible.

Adult↗
PubMed1997

2/3 osteotomy for lengthening the mandible in dogs by gradual distraction.

Successful lengthening of the mandible by gradual distraction has been reported previously. There are various methods for osteotomy before distraction osteogenesis. In this paper, a new type of osteotomy, performed on growing dogs as a model, is reported. Ten mongrel dogs, aged 6 months, were studied. A unilateral 2/3 osteotomy was performed, and an external lengthening device was fixed to the mandible perpendicular to the osteotomy. Seven days after the operation, the mandible was lengthened by 1 mm per day. The dogs were sacrificed for histological study at the end of the distraction on days 14, 28, 56 and 120 following completion of the distraction.

Animals↗
PubMed2000

Accuracy and precision of spiral CT in the assessment of neoplastic lesions associated with the mandible.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine the accuracy (validity) and precision (reliability) of spiral computed tomographic (CT) images by using film- and computer graphics-based measurements of simulated neoplastic lesions associated with the mandible. MATERIALS AND METHODS: Four cadaver heads, each with two simulated tumors containing contrast medium positioned medial to the mandibles, were examined by using a subsecond spiral CT scanner. Data were transferred to film and to a computer workstation. With computer graphics, data were analyzed by using multiplanar reconstructed images. Linear measurements of the length, width, and depth of simulated tumors were made by two observers, twice each, on the film scans by using manual calipers and on the multiplanar reconstructed images by using computerized measurements. The soft tissues were then removed from the cadavers and the same measurements made by using the same calipers. RESULTS: No statistically significant differences between computer graphics- or film-based measurements and physical measurements (P > .05) or between inter- and intraobserver measurements (P > .05) were found. CONCLUSION: The authors found high reproducibility of measurements for all dimensions. Spiral CT allows accurate computer graphics- and film-based measurements of neoplastic lesions associated with the mandible.

Aged↗
PubMed1998

Preliminary evaluation of hydroxyapatite cement as an augmentation device in the edentulous atrophic canine mandible.

OBJECTIVE: The purpose of this study was to answer the following two questions: (1) Can hydroxyapatite cement in combination with demineralized freeze dried bone feasibly augment the dimension of an atrophic edentulous canine mandible? (2) What is the histologic fate of an augmentation graft composed of hydroxyapatite cement and demineralized freeze dried bone placed on the surface of an atrophic edentulous canine mandible? STUDY DESIGN: Each of four mixed-breed canines (weighing 50 to 60 pounds) underwent bilateral mandibular dental extraction (canine to second molar) and radical alveolectomy. After 4 months of healing, a bilateral subperiosteal mandibular augmentation graft was put into place, with hydroxyapatite cement/demineralized freeze dried bone on the surface of one hemimandible and porous granular hydroxyapatite and demineralized freeze dried bone on the surface of the other hemimandible. The animals were killed after functioning on a soft diet for 9 months, and the grafted hemimandibles were harvested. RESULTS: Both hydroxyapatite cement and granular hydroxyapatite grafts appeared to augment the edentulous atrophic canine mandible. On histologic exam, the hydroxyapatite cement grafts showed osteoconduction and subperiosteal and endosteal osteonal bone formation, whereas the granular hydroxyapatite grafts showed only osteoconduction. Neither graft material showed chronic or acute inflammation. CONCLUSION: Hydroxyapatite cement can function feasibly as a mandibular augmentation device. The histologic fate of hydroxyapatite cement is different from that of granular hydroxyapatite. It has a fate comparable to autograft or allograft cortical bone grafts.

Alveolar Ridge Augmentation↗
PubMed2000

Quantitative trait loci for directional but not fluctuating asymmetry of mandible characters in mice.

Non-directional variation in right minus left differences in bilateral characters, referred to as fluctuating asymmetry (FA), often has been assumed to be largely or entirely environmental in origin. FA increasingly has been used as a measure of developmental stability, and its presumed environmental origin has facilitated the comparisons of populations believed to differ in their levels of stability. Directional asymmetry (DA), in which one side is consistently larger than the other, has been assumed to be at least partially heritable. Both these assumptions were tested with interval mapping techniques designed to detect any quantitative trait loci (QTLs) affecting FA or DA in 15 bilateral mandible characters in house mice resulting from a cross of the F1 between CAST/Ei (wild strain) and M16i (selected for rapid growth rate) back to M16i. For purposes of the analysis, all mandibles were triply measured and 92 microsatellite markers were scored in a total of 350 mice. No significant QTLs were found for FA, but three QTLs significantly affected DA in several characters, confirming both assumptions. The QTLs for DA were similar in location to those affecting the size of several of the mandible characters, although they accounted for an average of only 1% of the total phenotypic variation in DA.

Analysis of Variance↗
PubMed1998

Comparison of Brånemark fixture integration and short-term survival using one-stage or two-stage surgery in completely and partially edentulous mandibles.

The aim of this prospective study was to compare the clinical integration and survival of Brånemark fixtures when using the conventional 2-stage surgical procedure to 1-stage surgical approach in completely and partially edentulous mandibles. A total of 85 patients were consecutively treated for partial (n = 35) or complete (n = 50) mandibular edentulousness. Fixtures removed because of mobility, pain or infection were counted as failures. The first 10 patients of each group were selected for radiographical analysis of crestal bone changes 1 year after prosthesis insertion. In 33 patients with edentulous mandibles, 170 fixtures were placed in a 1-stage approach. In this group, 4 fixtures (2.4%) were lost prior to prosthetic restoration. Seventeen edentulous patients received a total of 70 fixtures in a 2-stage procedure. Out of these, 5 fixtures (7.1%) were lost at abutment connection. In 17 partially edentulous patients, 41 fixtures were inserted in a 1-stage approach. Two fixtures (5%) were lost in this group. Finally, 18 partially edentulous patients received a total of 49 fixtures in a 2-stage procedure. Out of these, 6 fixtures (12%) were lost at abutment connection. In total 313 of the 330 installed mandibular implants were loaded between 6 and 12 months (94.8% success). No further losses occurred in the implants functioning at least 1 year (267 implants) or at least 2 years (59 implants). Statistical analysis (Chi square test) revealed no difference in fixture survival between the treatment modalities. Radiographical analysis after 1 year of functional loading showed the typical bone resorption changes up to the most coronal implant thread in both modalities. Although this study pertains to relatively early loading of 2 years, the results seem to indicate that in the mandible a 1-stage surgical approach with Brånemark fixtures may be as predictable as the conventional 2-stage procedure.

Adult↗
PubMed1998

Densitometric measurements of the mandible: accuracy and validity of intraoral versus extraoral radiographical techniques in an in vitro study.

In this study a comparison is made between intraoral and extraoral radiographical techniques for quantitative measurements of bone density in the edentulous mandible. A phantom model, composed of a dry mandible surrounded by a soft tissue substitute was used. Radiographs were made of aluminium implants of known volumes. Intra- and extraorally placed reference wedges of aluminium or a combination of aluminium and plexiglas were used for the measurement of the aluminium volume of the above-mentioned implants and compared with the real volume. The IBAS image analysis system was used for image processing and measurements. A systematic deficit in the measured volume of 15 to 29% was found. This error was irrespective of the radiographical technique and indicates a constant underestimation of the aluminium volumes. The differential influence of the secondary radiation on the images of the jaw and the wedge is proposed to be a possible cause of this constant underestimation. The intraoral and extraoral techniques do not display significant statistical differences in the levels of validity or accuracy. Obtaining serial intraoral radiographs of adequate quality in the atrophic edentulous mandible can be problematic. It is concluded from this in vitro study that in these cases Oblique Lateral Cephalometric Radiographs may provide a valuable alternative for quantitative image analysis.

Absorptiometry, Photon↗
PubMed2000

Anisotropic elastic properties of cancellous bone from a human edentulous mandible.

The elastic moduli have not been reported for cancellous bone from the edentulous mandible. Accurate values are needed for finite element modeling of the mandible. The aim of this study was to determine elastic modulus values in three orthogonal directions for cancellous bone taken from an edentulous jaw and to relate these values to apparent density and volume fraction. Seven samples were obtained from the edentulous mandible of a 74-year-old female. Young's modulus was determined by compression testing of cubes cut with the faces aligned with the anatomic axes. Bone volume fraction averaged 0.33 (SD 0.14) and apparent density averaged 0.55 g/cc (SD 0.29). Young's modulus was greatest in the mesio-distal direction (mean 907 MPa, SD 849 MPa), followed by the bucco-lingual (mean 511 MPa, SD 565 MPa) and infero-superior direction (mean 114 MPa, SD 78 MPa). The infero-superior direction was less than the bucco-lingual (P = 0.03) and mesio-distal (P = 0.002). The mesio-distal and bucco-lingual directions could not be shown to be different (P = 0.32). This suggests a model of transverse isotropy for cancellous bone in the jaw, where the symmetry axis is along the infero-superior (weakest) direction.

Aged↗
PubMed2001

Bone mineral density in mandibles of ovariectomized rabbits.

The purpose of this study was to evaluate the association between loss of ovarian function and bone mineral density changes in the mandibles of ovariectomized rabbits using peripheral quantitative computed tomography. Twenty-four adult female Japanese white rabbits were used in this experiment. The mandibular incisors were initially extracted to create implant bone. Twelve animals were bilaterally ovariectomized and the other twelve sham-ovariectomized 12 weeks after tooth extraction. All rabbits were sacrificed at 4 and 12 weeks after ovariectomy and sham-ovariectomy, with 6 rabbits in each of the four resultant groups. The edentulous parts of distal mandibular bodies were measured by peripheral quantitative computed tomography. There were significant decreases in total bone mineral density and trabecular bone mineral density in the mandibles of rabbits at 12 weeks post-ovariectomy. The results demonstrate the mineralized bone loss in the mandibles of ovariectomized rabbits.

Animals↗
PubMed1999

An in-vitro evaluation of a dental subtraction radiography system using bone chips on dried human mandibles.

The aim of this in vitro study was to evaluate the ability of digital subtraction radiography to detect small differences in bone density between 2 dental images captured with the Digora radiographic imaging system. 5 dried human mandibles were held in a fixed position and cortical bone chips were superimposed on the alveolar bone between the 1st molar and 2nd premolar teeth. For each mandible, a reference image was obtained without bone chip placement. Subsequently, another image without a bone chip and a series of 10 images with bone chips ranging from 1.2 to 35.3 mg, were recorded. Each of the initial images of the 5 mandibles was then compared to the 11 subsequent images using digital subtraction radiography. The difference in density between the 2 images, at the site between the 1st molar and 2nd premolar, was calculated and represented as a volume equivalent of aluminium. Regression analysis demonstrated a close relationship between the weight of the bone chips and the aluminium equivalent density difference between the 2 radiographs (r2 = 0.96). Good results were obtained with the smaller bone chips that more closely resembled the dimensions of bone changes likely to be of clinical interest (1-8 mg). It is concluded that this subtraction radiography system is suitable for clinical investigations of localised small changes in alveolar bone and for the diagnosis and monitoring of destructive forms of periodontal diseases.

Absorptiometry, Photon↗
PubMed2001

Effect of experimental diabetes on mandible growth in rats.

The aim of the present work was to assess the effects of experimental diabetes on mandible growth in rats. Experimental diabetes was induced in rats, aged 26 d, by a single dose of 100 mg/kg b.w. of Streptozotocin (STZ). Thirty-one d post STZ or vehicle injection, the animals were killed. Mandibles were resected to determine Mandibular Skeletal Units dimensions (MSU) and overall mandible growth. Statistical analysis of results revealed, for STZ treated animals as compared to the control group: 1) a decrease in b.w.; 2) an increase in food intake; 3) an increase in glucemia (200%); 4) normal hemoglobin, creatinine and plasma urea values; 5) a reduction in growth of symphyseal (9%), coronoid (16%), and alveolar (13%) heights, condyloid (11%), angular (8%), and base (3%) lengths, and condyloid width (8%). Mandibular length (4%), height (8%) and length of base (6%) were significantly lower in diabetic animals as compared to the control group. No significant differences in length of symphyseal process, alveolar length and height of base were found between groups. Rats on a restricted diet, resulting in a decreased b.w., and the control group exhibited similar mandibular dimensions. These data show that STZ-induced diabetes reduces mandibular growth, resulting in some deformity of the structure.

Alveolar Process↗