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PubMed1986

Displacement of the mandible after removal of the intermaxillary fixation following oblique sliding osteotomy.

In an earlier study (Rosenquist et al., 1985) on oblique sliding osteotomy in 14 patients, operative repositioning and postoperative displacement of the mandible during intermaxillary fixation were presented. In the present stereometric study on the same patients displacement of the mandible after removal of the intermaxillary fixation is presented. A continuous anterior and a minor initial cranial translation and an anterior rotation of the mandible were found. Proclination of both upper and lower incisors was recorded. Correlations were found between operative repositioning and postoperative displacement of the mandible after removal of the intermaxillary fixation. Possible relapse mechanisms are discussed.

Cephalometry↗
PubMed1999

Does 2 years' nocturnal treatment with a mandibular advancement splint in adult patients with snoring and OSAS cause a change in the posture of the mandible?

The aim of this pilot study was to investigate the effects of 2 years' nocturnal treatment with a mandibular advancement splint in adult patients with snoring and obstructive sleep apnea syndrome with respect to possible development of a forward position of the mandible or other dentofacial changes. Thirty snoring and sleep apnea patients, mean age 55.3 years (SD, 8.61; range, 46.5 to 79.8 years), referred from the Ear, Nose, and Throat Department, were treated with an acrylic splint with full tooth coverage that advanced the mandible 5 to 8 mm (70% of maximal protrusion) and used 5 mm opening vertically. The splint was used 6 to 8 hours per night and 5 to 7 nights per week. Two lateral head radiographs were taken in centric occlusion, 1 before and 1 after 2 years of treatment. A small but statistically significant forward and downward change in mandibular position was found after treatment; mean was 0.4 mm (SD, 0.53; range, 0.0 to 2.0 mm; P <.001) and 0.3 mm (SD, 0.43; range, 0. 0 to 1.5 mm; P <.001), respectively. The forward and downward movement of the mandible was accomplished by a statistically significant increase in mandibular length-mean was 0.4 mm (SD, 0.62; range, 0.0 to 2.5 mm; P <.01)-and a significant decrease in overjet (P <.001) and overbite (P <.05). However, none of the patients reported any permanent sense of altered occlusion, and the anteroposterior distance between habitual occlusion (intercuspal position) and centric relation (retruded position) did not exceed 1. 0 mm in any of the patients either before or after the treatment. The change in mandibular position might be a result of a condylar and/or glenoid fossa remodeling or condylar position changes within the fossa as a compensatory reaction to the advancement of the mandible (bite jumping). However, to visualize and analyze such possible changes in detail, additional studies using lateral tomography of the temporomandibular joints or magnetic resonance imaging are required. Furthermore, because the treatment of snoring and OSAS patients is considered to be lifelong, long-term studies are needed to analyze if the small change in mandibular position will continue with further treatment.

Adaptation, Physiological↗
PubMed1999

Distraction osteogenesis in Silver Russell syndrome to expand the mandible.

Distraction osteogenesis is a method commonly used to activate bone regeneration in nonunions and osseous defects and for lengthening procedures of tubular bones. This technique involves the sectioning of a bone and the subsequent deliberate, controlled movement of the opposing sectioned edges to lengthen, widen, or reposition a bone, or all three. In this report, a patient with Silver Russell syndrome and severe mandibular hypoplasia was treated by means of distraction osteogenesis of the midsymphysis to widen the mandible in concert with sagittal-ramus osteotomies to lengthen the mandible. This treatment created significantly increased arch length in the mandible, which was necessary to facilitate the patient's orthodontic treatment. We believe this is the first reported case of distraction osteogenesis to widen the mandible with the use of a tooth-borne appliance.

Cephalometry↗
PubMed1995

Factors influencing the patterns of invasion of the mandible by oral squamous cell carcinoma.

The pattern of tumour invasion of the mandible depends on the extent of invasion. Both the width (P = 0.02) and depth (P = 0.01) in patients with an invasive or infiltrative pattern of disease were greater than in tumours showing the less aggressive erosive pattern in which the tumour mass is separated from the resorbing bone by a connective-tissue layer. Evidence in this study suggests that the erosive pattern develops through a mixed pattern to the invasive pattern of disease as the tumour progresses through the bone. The invasive pattern of disease was evident at a much shallower depth in the molar region of the mandible (mean 9 mm), with a decreased ratio of alveolar to basal bone, than in the premolar and parasymphyseal region (mean 25 mm) (P = 0.02). The hypothesis to explain this phenomenon is that the more superficial alveolar bone responds by resorbing in advance of the tumour, but the basal bone is unable to respond in the same way and becomes widely infiltrated. The attached mucosa with its firm collagen attachment to bone is proposed as the main route of tumour entry into the mandible in both dentate and edentulous mandibles.

Alveolar Process↗
PubMed1996

Magnetic resonance appearance of bone marrow in the mandible at different ages.

To differentiate pathologic states of bone marrow from normal age-related marrow conversion, magnetic resonance appearances of the mandible were analyzed cross-sectionally according to age in 73 normal volunteers. Low signal intensities of red marrow first changed to high signal intensities in the anterior region of the mandibular body. With increase in age, marrow conversion was observed in the premolar/molar region, angle, ramus, and condyle regions in that order. No red marrow was recognized in the body of the mandible of subjects more than 30 years old. After the age of 30, the majority of the subjects showed high signal intensities in the entire bone marrow of the mandible. However, one subject over 30 years of age showed some portions of red marrow in the ramus and condyle. This knowledge about age-related marrow conversion of the mandible on magnetic resonance imaging will be useful in the visual differentiation from abnormal bone marrow, such as anemias, inflammatory diseases, infiltrative neoplastic disorders, and metastatic diseases.

Adolescent↗
PubMed1998

Primary temporary AO plate reconstruction of the mandible.

OBJECTIVE: This study assessed the incidence of complications and revisions after primary temporary AO plate reconstructions of the mandible performed from 1971 through 1996. STUDY DESIGN: In a retrospective record review, the data of 51 patients undergoing primary temporary AO plate reconstructions after composite mandibular resection were analyzed according to age, gender, date of reconstruction, anatomic location of reconstruction, use of additional radiotherapy and/or flap surgery, and incidence of associated complications and revisions. RESULTS: Associated complications and revisions accompanying primary temporary AO plate reconstructions were evaluated through use of the incidence rates of associated complications (IACs) and revisions (IARs), which are reported as the numbers of associated complications and revisions, respectively, per 100 patients. Of the entire sample, the highest incidence rate of associated complications was associated with infection (33.5); this was followed by the rates for plate exposure (27.9) and plate fracture (10.7). With an overall incidence rate of 38.3 revisions per 100 patients, the corresponding site-related incidence rates of associated revisions were found to be 55.0 for reconstructions of the anterior mandible crossing the midline, 37.1 for those of the body segment of the mandible, and 31.1 for reconstructions involving the ramus and/or condyle area of the mandible. Revision rates were observed to be significantly higher in irradiated (53.6 vs 31.5) and non-flap-added reconstructions (43.2 vs 24.8). Analysis of treatment group-related incidences revealed irradiated non-flap-added reconstructions to be associated with the highest failure rates, whereas additional flap surgery resulted in a significant reduction in complications (50.0 vs 108.0) and revisions (20.0 vs 65.7). CONCLUSIONS: This study showed primary temporary AO plate reconstructions after composite mandibular resection to be associated with a high rate of complications and revisions. The results emphasize the need to relate outcome measures to site-related and treatment-related parameters.

Adult↗
PubMed2000

Oblique lateral cephalometric radiographs of the mandible in implantology: usefulness and accuracy of the technique in height measurements of mandibular bone in vivo.

Various radiographic techniques are used for longitudinal studies of changes in the height of the mandible with implants. Advantages and disadvantages of panoramic radiographs, lateral cephalometric radiographs, periapical films and modern CT- and MRI-techniques are briefly discussed. In this study, the usefulness of a conventional radiographic technique for measuring the height of the mandible, i.e. oblique lateral cephalometric radiography (OLCR) is evaluated in vivo. In 16 patients with permucosal implants in the anterior mandible OLCRs were repeated the same day. The mean total error for the radiographic procedure and analysis was 0.38 mm. The intra-observer error for the determination of the mandibular height by means of the image analysis procedure was 0.16 mm (analysis error). In 12 other patients pairs of radiographs of the same area of the mandible were made using both a "standard" horizontal X-ray beam direction and an individually determined "optimal" horizontal X-ray beam direction; the maximum difference between these two angulations was plus or minus 7.5 degrees. The effect of this different angulation on the height measurements is comparable to the above-mentioned total error of the measurement procedure (positioning error). An accurate positioning of the patient seems important for reliable measurements. The described radiographic (OLCR) and analysis (IBAS) technique can be used relatively simply for clinical studies. The described methods appear to be useful for measuring the mandibular height in longitudinal studies in patients with or without implants.

Cephalometry↗
PubMed2002

Augmentation of the mandible with GTR and onlay cortical bone grafting. An experimental study in the rat.

The aim of the present study was to evaluate the effect of augmenting the mandible with onlay mandibular bone grafts that were covered with e-PTFE membranes according to the principle of guided tissue regeneration (GTR). The experiment was carried out in 30 rats. The inferior border of the mandible and parts of the mandibular body were exposed on both sides. On one side, an autogenous bone graft that was harvested from the angle of the mandible was placed on the inferior border of the mandible and was fixed with a titanium microimplant. Subsequently, the graft was covered with an e-PTFE membrane. The contralateral side, serving as control, was treated the same way except for the placement of the membrane. Groups of six animals were sacrificed 15, 30, 60, 120 and 180 days following surgery, and specimens that were prepared from the experimental and control sites were analyzed histologically. The bone graft underneath the membrane initially presented superficial resorption but, subsequently, the space that was created by the membrane gradually became filled with bone. After 180 days, the area underneath the membrane was completely filled with bone and it was impossible to distinguish between the bone graft and the newly formed bone. Generally, the bone grafts at the control sides were characterized by a gradual resorption during the entire experimental period. At 180 days after transplantation, only a few grafts at the control sites had retained their height, and there was frequently a lack of continuity between the bone graft and the underlying mandibular bone. It can be concluded that onlay mandibular bone grafts combined with GTR may improve the predictability of mandibular augmentation, in comparison to bone grafting alone.

Alveolar Ridge Augmentation↗
PubMed2002

Vertical distraction of the severely resorbed edentulous mandible: a clinical, histological and electron microscopic study of 10 treated cases.

The aim of this study was to evaluate the clinical and histomorphological results of distraction of the severely resorbed edentulous mandible. In a group of 10 edentulous patients suffering from insufficient retention of their mandibular denture related to a severely resorbed mandible, the anterior segment was augmented as a preimplant surgical procedure using the nonvoluminous Groningen Distraction Device (GDD). Two months after the last day of distraction, a bone biopsy was taken with a trephine, both distraction screws were replaced by endosseous implants and the guide screw was removed. The biopsies were examined by means of light microscopy (LM) and transmission electron microscopy (TEM). Radiographical and histomorphological examination of the biopsies revealed the presence of two cortical zones, one at each end of the biopsies, a poorly mineralized, fibrous interzone in the middle of the distraction gap, and two zones of mineralization between the central fibrous and the peripheral cortical zones. Formation of lamellar bone parallel to the distraction vector was clearly visible in the mineralization zone as well as signs of remodelling at the borderline between the native cortical bone and the generate. Clinical examination showed in all patients that the anterior segment distracted from the mandible body was sufficiently enlarged to enable insertion of endosseous implants with a length of at least 12 mm. One implant was lost during the healing phase, but was successfully replaced thereafter. Implant retained overdentures were fabricated 3 months after implantation. All patients have good function 11.2 +/- 4.3 months after the end of treatment. From this study it is concluded that the GDD has proven to be a reliable tool for augmentation of the anterior segment of a severely resorbed edentulous mandible enabling osseointegration of endosseous load-bearing implants.

Aged↗
PubMed2003

Bone mineral density of the mandible in ovariectomized rats: analyses using dual energy X-ray absorptiometry and peripheral quantitative computed tomography.

INTRODUCTION: Although previous studies have shown that maxillary molar extraction in ovariectomized (OVX) animals causes mandibular loss of bone, it is still questionable as to whether estrogen deficiency affects mandibles with functional occlusion. MATERIALS AND METHODS: To answer this question, 13-week-old female Sprague-Dawley rats were bilaterally OVX or sham-operated. After 109 days, the bone mineral density (BMD) of the femurs and mandibles was measured using dual-energy X-ray absorptiometry (DEXA) and peripheral quantitative computed tomography (pQCT). RESULTS: In DEXA analysis, although the BMD of the total mandible of the OVX rats was similar to that of the sham-operated rats, the BMD of the condylar region in the OVX rats had decreased by 12.5%. In pQCT analysis, decrease in trabecular BMD of the mandibular bone was detectable but low in the molar region (maximal 13%), whereas no difference was seen in cortical BMD. In the femurs, the trabecular bone prominently decreased in OVX rats (30% decrease in pQCT analysis) as previously reported. CONCLUSION: This study revealed regional differences in the mandibular bone decrease in OVX rats. Although the mechanism of low susceptibility of the mandible to estrogen-deficient conditions remains unknown, it is likely that mechanical stress derived from functional occlusion is preventing bone loss in this pathological condition. Furthermore, this study demonstrated the advantage of pQCT in analyzing rat mandibular bone.

Absorptiometry, Photon↗
PubMed1997

Effect of axial plane deviation on cross-sectional height in reformatted computed tomography of the mandible.

OBJECTIVE: To assess the effect of angular deviation on the measured height of the mandible in reformatted cross-sectional CT scans. METHODS: Reformatted cross-sectional CT scans were obtained from three dried mandibles, at three angulations, in a special holding and positioning device for perpendicular measurements. The radiographic lengths of 321 measurements were compared with the actual bone length. RESULTS: The mean difference between actual bone length and image length, with transaxial planes parallel to the lower border, was 0% (s.d. 3.6). Deviations of 10 degrees and 20 degrees from the lower border of the mandible resulted in a mean error of 1% (s.d. 4.5) and 2.8% (s.d. 8.0) respectively. When the angulation between the deviated transaxial plane and the lower border was greater than 10 degrees, the maximum error was about +/- 30%. CONCLUSION: The use of different transaxial planes along the mandible may result, in a small proportion of cases, in discrepancies in height when measured from the cross-sectional images obtained. This may lead to incorrect interpretation of the depth of bone available for implants.

Dental Implantation, Endosseous↗
PubMed2002

Three-dimensional magnetic resonance image of the mandible and masticatory muscles in a case of juvenile chronic arthritis treated with the Herbst appliance.

The present report documents, in a case of juvenile chronic arthritis (JCA) with mandibular retrognathia, three-dimensional (3D) changes in the mandible and the relationship between the mandible and the masticatory muscles resulting from treatment with the Herbst appliance after cessation of growth. Magnetic resonance scanning of the whole head was carried out before and after treatment. The mandible, the masseter, and the medial and lateral pterygoid muscles were segmented bilaterally and reconstructed in 3D for both stages. Superimposition of the datasets was carried out according to anatomical structures in the brain (cranial base). Mandibular superimposition was performed according to the mandibular symphysis and the lower mandibular border. The mandible moved forward and downward relative to the anterior cranial base. In addition, bone apposition was observed at the superior and posterior surfaces of both mandibular condyles and at the roof of the glenoid fossa. The masticatory muscles remained relatively stable in position in relation to the anterior cranial base. To our knowledge, such information in JCA patients has not previously been published in the literature. Using magnetic resonance imaging (MRI), it was possible to gain improved insight into the 3D morphology including soft tissues without the overlap of the surrounding tissues observed in the conventional radiographs. Accordingly, it is suggested that 3D magnetic resonance analysis is a more useful method for the follow-up of the JCA patients than radiographic techniques.

Adolescent↗
PubMed2000

Kinematic and kinetic observations on ballistic depression and elevation of the human mandible.

To study mandibular motions with respect to time (kinematics) and the forces causing and resulting from these motions (kinetics), four subjects generated rapid depression and elevation of the mandible (displacement of 0.224 m; peak velocity of 0.237 m s(-1) during depression and 0.269 m s(-1) during elevation). The motion of depression (duration of 0.195 s; kinetic energy of 2.072 x 10(-3) J) could be divided into a phase of acceleration (2.742 m s(-2); +/- 0.28 gn) and a phase of deceleration (2.264 m s(-2); - 0.23 gn), and the terminal excess kinetic energy of depression was absorbed and dissipated by, primarily, the temporomandibular joint. Similarly, the ensuing motion of elevation (duration of 0.182 s; kinetic energy of 2.948 x 10(-3) J) could be divided into a phase of acceleration (3.498 m s(-2); + 0.36 gn) and a phase of deceleration (2.931 m s(-2); -0.30 gn), and the terminal excess kinetic energy of elevation was absorbed and dissipated by, primarily, the dentitions and, secondarily, by the temporomandibular joint. Rapid depression of the mandible appeared to be under the central control of a preprogrammed motor command, and ensuing rapid elevation of the mandible appeared to be under the peripheral control of a segmental and/or transcortical reflex. During rapid depression and elevation of the mandible, the anterior suprahyoid, anterior temporalis, and sternocleidomastoid muscles were myoelectrically active 56%, 73%, and 71% of the time, respectively, and myomechanically active 42%, 59%, and 57% of the time, respectively. Over a follow-up period of 12 months, the studied mandibular motions did not cause injury to the dentitions and temporomandibular joint.

Biomechanical Phenomena↗
PubMed2002

Effect of calcium supplementation on bone dynamics of the maxilla, mandible and proximal tibia in experimental osteoporosis.

The effect of calcium supplementation on the bone dynamics in the hard palate of the molar region (maxilla), mandible and proximal tibia in experimental osteoporotic rats was examined. Ninety ovariectomized (OVX) and 45 sham-OVX Wistar female rats were used in this study. All the rats received surgical operation at 6 weeks of age. Ovariectomized rats were fed on a low calcium diet (0.02%) for 12 weeks post-operation, and then randomly divided into the two following groups. One group was fed on high calcium diet (2.30%) (OVX-HCa) and the other group was remained on the low calcium diet (OVX-LCa). Sham-OVX rats were fed on regular calcium diet (1.15%) during the experimental period (Sham-OVX). Histomorphological analysis was carried out from 12 to 32 weeks post-operation. On undecalcified thin section, bone volume, eroded surface, osteoid surface and bone formation rate were calculated for cortical bone of the maxilla, and for cancellous bone of the mandible and proximal tibia. In the OVX-LCa group, compared with the Sham-OVX group, decrease of the bone volume and increase of the bone resorption and formation parameters were detected throughout the observation periods. In the OVX-HCa group, compared with the OVX-LCa group, increase of the bone volume and temporarily increased parameters of bone formation at 1 week after feeding on high calcium diet were observed in the maxilla, but these changes were not observed in the mandible and proximal tibia. Moreover, the bone resorption and formation parameters in the maxilla, mandible and proximal tibia in the OVX-HCa group became equivalent to the Sham-OVX levels with the passage of time.

Analysis of Variance↗
PubMedDate not supplied

Developmental integration in a complex morphological structure: how distinct are the modules in the mouse mandible?

The mouse mandible has long served as a model system for studying the development and evolution of complex morphological structures. We used the methods of geometric morphometrics to reassess the hypothesis that the mandible consists of two separate modules: an anterior part bearing the teeth and a posterior part with muscle attachment surfaces and articulating with the skull. The analyses particularly focused on covariation of fluctuating asymmetry, because such covariation is due exclusively to direct interactions between the developmental processes that produce the traits of interest, whereas variation of traits among individuals also reflects other factors. The patterns of fluctuating asymmetry and individual variation were only partly consistent, indicating that developmental processes contribute differentially to variation at different levels. The results were in agreement with the hypothesis that the anterior and posterior parts of the mandible are separate develop-mental modules. Comparison of all alternative partitions of the landmarks into two contiguous subsets confirmed the hypothesis for the location of the boundary between modules but also underscored that the separation between them is not complete. Modularity is therefore manifest as the relative independence of parts within the framework of overall integration of the mandible as a whole-it is a matter of degrees, not all or nothing.

Analysis of Variance↗
PubMed2001

Preprosthetic vertical distraction osteogenesis of the mandible using an L-shaped osteotomy and titanium membranes for guided bone regeneration.

PURPOSE: Vertical osteodistraction is a new alternative method for alveolar ridge augmentation of the mandible. The purpose of this article is describe a technique using an L-shaped osteotomy and titanium membranes for guided bone regeneration (GBR) in the distraction gap. PATIENTS AND METHODS: Ten patients with severe atrophy of the edentulous molar region of the mandible underwent vertical callus distraction in 13 sites using intraoral microplate distractors. An L-shaped osteotomy with a short vertical part mesially and a longer horizontal part ending in the retromolar region was made, and the osteotomized segment was fixed to the mandibular ramus at its distal edge by a microplate, which became the center of rotation when distraction began. In this way, more callus generation could be achieved mesially than in the distal molar region. Follow-up computed tomography (CT) scans reconstructed axially to the axis of the mandible revealed semilunar excavations of the generated bone buccally in the distraction gap in the first cases. Clinical inspection on removal of the distractors showed fibrous connective tissue in the gap. Therefore, to prevent this from happening, titanium membranes covering the distraction gap were applied in subsequent cases. RESULTS: Ten patients (13 sites) were treated by vertical callus distraction. In 4 cases, GBR was achieved using titanium membranes. In all cases, the increase in alveolar height was sufficient to make dental implantation possible. In 1 patient, a fracture of the distractor occurred, and dehiscence was observed in 2 cases. These complications did not change the plan of therapy nor did they influence the results. The CT scans showed a homogenous surface on the regenerated mandible in the cases of GBR application. CONCLUSION: Both an L-shaped osteotomy and the application of titanium membranes for GBR in the distraction gap are of great value for mandibular augmentation, producing a physiologically shaped alveolar ridge.

Adult↗
PubMed2003

Histomorphometric evaluation of short-term changes in masseter muscle after lengthening the rabbit mandible by distraction osteogenesis.

PURPOSE: Structural changes in muscles may affect the process during and after distraction osteogenesis (DO) of the mandible. However, the response of the masticatory muscles is still not well defined after gradual lengthening of the mandible. In this experimental study, short-term structural changes in masseter muscles of the rabbits are evaluated after mandibular DO. MATERIALS AND METHODS: Left mandibles of 10 New Zealand rabbits were lengthened by DO for 7 days in the rate of 1 mm/day. Mandibles of all animals were removed at the end of the consolidation period. Muscle biopsy samples of distracted and contralateral sides were histopathologically investigated, and histomorphometric results were statistically analyzed. RESULTS: Atrophy, hypertrophy, regeneration, and concomitant mild interstitial edema and fibrosis were found more evident in experimental side biopsy samples 30 days after distraction. Histomorphometric analysis revealed a statistically significant decrease in the mean regions of masseter muscle fibers of the distracted sides compared with the control sides (P <.05). CONCLUSION: This experimental study showed that the structure of masseter muscle is influenced during and shortly after mandibular distraction osteogenesis. Atrophic changes of the ipsilateral masseter muscles may be regarded as regenerative response that occurs during and shortly after distraction period.

Animals↗
PubMed2002

Effect of zinc on rat mandibles during growth.

Zinc is a constituent of enzymes such as alkaline phosphatase and is an essential trace element involved in bone formation. The purpose of this study was to examine the effects of low levels of zinc intake on bone density and the area of cortical and trabecular bone in rat mandibles during the growth stage with peripheral quantitative computed tomography. The cartilaginous ossification in the femur was also measured. In the mandible, the low-zinc group showed significantly lower trabecular bone density compared with the control group, whereas the zinc-deficient group showed significantly lower levels of cortical bone density and trabecular bone density in the area. On the other hand, in the femur, both the zinc-deficient group and the low-zinc group showed a significantly lower value in cortical bone density and trabeculae bone density when compared with those of the control group. Moreover, the area of cortical bone and trabecular bone in the zinc-deficient group showed significantly lower values than those of the control group, whereas the low-zinc group only showed a significantly lower area of cortical bone than that of the control group. These results suggested that changes in zinc intake might exert an effect on the osseous tissue of the mandible and femur, and the femur was more sensitive to change of dietary zinc content than mandibles.

Animal Feed↗