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The use of hydroxylapatite mixed with autogenous bone to augment the area posterior to the mental foramen is described. This method is combined with an interposed bone graft technique in the symphyseal area. The clinical implications are discussed in relation to potential nerve damage, height to be gained, and effects on lip-chin profile, and the results in 29 patients are reported.
PURPOSE: The purpose of this study was to determine the precise in situ location of the lingual nerve in the third molar region using high-resolution magnetic resonance imaging. PATIENTS AND METHODS: Ten healthy volunteers (20 sides) with mandibular third molars underwent bilateral axial and coronal high-resolution magnetic resonance imaging (MRI) examinations of the posterior mandible and floor of the mouth from the lingula to the mental foramen. Three trained individuals made measurements of each image to determine the vertical and horizontal position of the lingual nerve in the third molar region. RESULTS: The mean vertical (2.75 +/- 0.97 mm [range, 1.52-4.61]) and horizontal (2.53 +/- 0.67 mm [range, 0.00-4.35]) distances to the lingual crest and lingual plate of the mandible were determined. In the third molar region, there were only 2 of 20 cases (10%) in which the nerve was above the lingual crest, and there were 5 of 20 instances (25%) in which the nerve was in direct contact with the lingual plate. CONCLUSIONS: This study precisely documents the in situ location of the lingual nerve in the third molar region, and reconfirms the relative vulnerable position of this structure during third molar surgery.
A clinical study on 54 patients, who underwent augmentation of the atrophic mandible by interposed bone-grafts, but in whom routine follow-up vestibuloplasty was deliberately avoided, is presented. The results show a reduced rate of bone resorption in the anterior region and less interference with lip and chin sensibility. An additional study is included concerning the fate of the elevated ridge and associated bone-graft in the body region posterior to the mental foramen. Results suggest that the resorption pattern in this area is very similar to that of a subperiosteal bone-graft. Modification of surgical technique in this regard has produced encouraging results.
The purpose of this study was to evaluate the effect of muscle function and occlusal form on mandibular growth in guinea pigs. We hypothesized that restriction of maxillary width and asymmetric function of the mandible would lead to mandibular asymmetry. The hard palate of 12 animals was exposed at the age of ten days, and cyanocrylate was used to close the midpalatal suture in order to restrict transverse maxillary growth. The right incisors and right molars were ground obliquely at the time of surgery and every two weeks thereafter until the animals were sacrificed 4, 8 and 12 weeks later (four animals in each time group). Six age-matched animals served as controls. Dorsoversal x-rays were taken at sacrifice, followed by the removal of small biopsies from six different sites of the maxillomandibular skeleton for biochemical studies, which will be reported separately. Relative to controls, the treated animals exhibited a narrow maxilla and asymmetry in the height of the ramus and in the length of the mandible from the mental foramen to the angular process. The maximum width between the angular processes of the mandible was extremely narrow, as was the condylar neck especially on the right side. It was concluded that abnormal masticatory muscle function caused by occlusal deviation led to a narrowing and a slight asymmetry of the mandible in the growing guinea pig.
AIMS: The purpose of our protocol is to study neurosensory disturbances following genioplasty, sagittal split mandibular osteotomy, or both procedures in combination. Many authors assessed the incidence and degree of neurosensory disturbances of the inferior alveolar nerve following orthognathic surgery but often results are difficult to interpret and compare due to a lack of standardization of methods. PATIENTS: Fifty patients (24 males and 26 females) were tested with qualitative (touch sensation, sharp/blunt test, cold sensation and hot sensation) and quantitative methods (localization test, two point static and dynamic test) at least 1 year after orthognathic surgery. The patients were divided into the following groups: 10 patients in group 1 (controls); 12 patients in group 2 (genioplasty alone or in association with maxillary osteotomy or vertical mandibular ramus osteotomy); 10 patients in group 3 (sagittal split osteotomy alone); 18 patients in group 4 (sagittal split osteotomy with concomitant genioplasty). METHOD: On both sides four areas were tested: centre of chin and lip (cutaneous and mucosal sides), 2 cm lateral to the chin centre (cutaneous and mucosal sides), 3 cm lateral to the chin centre i.e. approximately at the mental foramen (cutaneous and mucosal sides) and vermilion. Tests were always performed by the same person. All patients were also asked to indicate whether the altered sensation was considered subjectively as being disabling. RESULTS: None of the patients showed persistent anaesthesia in the tested areas according to the qualitative tests. In group 2 the quantitative sensory tests revealed normal or slight hypoaesthesia (17%) in all areas tested; in 30% of the patients of group 3, minimal quantitative sensory disturbances were noted, while the incidence of objective sensory deficits increased in patients who had undergone a concomitant genioplasty (40% among group 4). Among the tested areas the vermilion and oral commissure were affected most often in all groups. Statistical analysis (using STATA 6.0) revealed that these differences were significant (p<0.05). There were also significant differences between group 1 and groups 3 and 4 for tactile sensitivity, location tests and sharp-blunt discrimination, while two point discrimination (quantitative test) showed statistically significant differences between group 1 and all other groups (2-4). No statistically significant differences among the four groups were found for thermal sensation (hot and cold). CONCLUSIONS: The combination of genioplasty and sagittal split osteotomy seems to be more detrimental for the lip sensibility than genioplasty or sagittal split alone. Thermal sensation is less affected than tactile sensation, location and two point discrimination tests (static and dynamic). Despite that, sensory deficit was never considered as disabling by the patients subjectively.
In general, carcinoma of the lower lip has a good prognosis after radical surgery. In rare cases, however, recurrences may be seen because of spread of the tumour along the mental nerve into the mandible. The earliest symptom of this is pain in the mandible and radiological evidence of widening of the mental foramen. Large resections and reconstructive procedures will be necessary. Three cases are presented.
Vascularized bone grafts taken from the iliac crest to augment the extremely atrophied mandible are valued for their ability to maintain their contour. Reliable data on long-term performance, however, is not yet available. The purpose of this study was to investigate the long-term results of this method, evaluating the radiological documentation (lateral cephalograms, orthopantomograms) of six patients. The mean follow-up period was 7.3 years. Dental implants were not inserted into the bone grafts. The average increase in ridge height immediately after surgery was 17.8 mm in the symphyseal area, 17.1 mm above the mental foramen and 13.9 mm in the molar region. In the first postoperative year, the average vertical loss was 3.0 mm in the symphyseal, 2.0 mm in the premolar and 2.9 mm in the molar regions. After that the mean yearly rate of vertical resorption dropped to 0.24 mm in the symphyseal, 0.27 mm in the premolar and 0.34 mm in the molar regions, which corresponded to the physiological loss in ridge height due to aging. The fact that graft resorption was so slight portends a good long-term prognosis with this procedure. However, indication is restricted by the high operative burden for the patient and by the availability of alternative rehabilitation methods.
OBJECTIVES: The purpose of this study was to evaluate the ability of two different panoramic imaging systems to produce cross-sectional images with accurate vertical dimensions of the posterior mandible. STUDY DESIGN: Three partially edentulous human cadaver mandibles were used for this study. On each mandible, three potential implant sites were arbitrarily identified in an area between the mental foramen and the ascending ramus. Each site was imaged using two different panoramic machines. Using each image, the mandible's outline, cortical thickness, and position of the mandibular canal were traced on clear acetate film. The mandibles were then sectioned at each site to serve as a gold standard. The cadaver sections and tracings (corrected for magnification) were measured, recording the overall mandibular height, distance from the crest of the ridge to the superior aspect of the mandibular canal, and the thickness of the cortical bone at the most inferior aspect of the mandible. RESULTS: There were no significant differences between either of the system's image measures and the gold standard when considering the distance between the crest and the mandibular canal. Differences were noted between the systems measures and the gold standard in the assessment of the cortical bone thickness and the overall mandibular height. CONCLUSIONS: Both imaging systems can be useful for vertical measurements of a potential implant site in the posterior mandible.
For certain surgical procedures (e.g. placement of implants), an accurate localisation of the mandibular canal is of utmost importance to avoid injuries to the neurovascular bundle. The aim of the present study was to evaluate, on human fresh cadavers (n = 6), the accuracy of conventional spiral tomography for the localisation of the mandibular canal. By means of the Cranex TOME multifunctional unit (Orion Corporation Soredex, Helsinki, Finland), tomographic slices were taken at 3 different locations in the left posterior mandible (distal to the mental foramen). The mandibles were then sectioned at these 3 sites with a microtome. With a digital sliding caliper, the following 3 measurements were performed both on the tomograms and the bone sections at the three sites: 1) distance from the crest to mandibular canal, 2) overall bone height and 3) bone width. Overestimations of the distance to the mandibular canal (8/18) ranged from 1.05 to 0.10 mm and underestimations from 0.30 to 1.36 mm. The same number of over- and underestimations occurred for the bone height (1.14 to 0.14 mm and 0.15 to 1.40 mm, respectively). The bone width scored more overestimations (10/18), ranging from 1.40 to 0.12 mm, while underestimations ranged from 0.25 to 1.35 mm. From the present results, it is concluded that spiral tomography using the Cranex TOME multifunctional X-ray unit provides accurate information and sufficient detail for preoperative planning of implant placement in the posterior mandible.
Treatment planning for dental implant patients is often complicated by the unknown extent of the anterior loop of the mental neurovascular bundle. The aim of this study was to determine the correlation between the visual interpretation of the panoramic radiographs and the anatomical dissection findings in a cadaveric sample. Panoramic radiographs of the 22 randomly selected coronally sectioned human head specimens were taken using the Scanora (Soridex, Orinon Corporation Ltd, Helsinki, Finland) radiographic unit jaw panorama (Programme 001, magnification 1.3) and dental panorama (Programme 003, magnification 1.7) and interpreted by two calibrated observers. Bilateral anatomical dissection was then performed on all specimens. The anterior loop of the mental canal was only identified in six panoramic radiographs (27%) (range 0.5-3 mm). There was a significant positive correlation between both observers of the radiographs and between the two radiographic programmes used. Anatomical measurements of the anterior loop of the mental neurovascular bundle revealed its presence in eight dissected specimens (range 0.11-3.31 mm; mean 1.20, +/-0.90). Fifty percent of the radiographically observed anterior loops of the mental canal were misinterpreted by observers with both radiographic programmes and 62% of the anatomically identified loops were not observed radiographically. Clinicians should not rely on panoramic radiographs for identifying the anterior loop of the mental nerve during implant treatment planning. However, a safe guideline of 4 mm, from the most anterior point of the mental foramen, is recommended for implant treatment planning, on the basis of our anatomical findings.
In order for clinicians to effectively manage their practices, they need to know how much time they spent in carrying out procedures. The provision of two-implant overdentures for edentulous patients is becoming more prevalent as increasing evidence demonstrates their great benefit to patients. The aim of this study was to measure the number of visits and the time required during the surgical phase (from pre-op examination to preliminary impressions) of mandibular two-implant overdenture treatment. Thirty edentulous patients were assigned to receive two root-form implants in the mandible between the mental foramen, as part of a randomized controlled clinical trial. All visits and time spent by the oral surgeon, the surgical assistant and the prosthodontist were measured individually. The mean number of scheduled visits with the oral surgeon was four, and the mean time taken was 104 min. The mean time taken by the surgical assistant was 122 min. On average, the prosthodontist was required for two visits, with a total mean time of 36 min. In addition to the scheduled visits, 14 patients solicited additional appointments (unscheduled visits) for various problems (e.g. loose healing cap). The average time taken for unscheduled visits was 32 min. Combining scheduled and unscheduled visits, the mean total time taken by the oral surgeon was 109 min. The surgical assistant was needed for a mean total of 125 min, and the prosthodontist spent, on average, 46 min in this phase of treatment. Results from this study will assist clinicians in establishing the total time and number of visits needed for the surgical phase of two-implant mandibular overdenture treatment.
OBJECTIVES: Basic research concerning craniofacial development presently runs along two pathways, namely the molecular and the morphometric. This gap needs to be bridged. DESIGN: Using histological serial sections of human fetuses computer-aided three-dimensional reconstructions were made (Software Analysis, SIS) with special focus given to all anatomical structures of the orofacial region of the growing head. RESULTS: All reconstructions can be viewed from any rotation and they are available for virtual dissection according to anatomical rules. As an example, the prenatal development of the human mandible with the formation of the mental foramen therein is described. Furthermore, the spatial arrangement of bone, cartilage and nerves is presented in three dimensions in different developmental stages. The interaction of tissues with possible morphogenetic interaction is discussed. CONCLUSIONS: This work serves as a reference system for prenatal development in comparison with pathological development.
OBJECTIVES: To investigate the mechanical effects of mastication on the mandible, we developed computational controlled mastication robot system with human dry skull and analyzed the strain distribution on the mandibular bone surface. DESIGN: In the mastication robot, the mandible was suspended by eight wires, which simulated masticatory muscles. A non-linear spring damper generated viscoelastic properties, and tension sensors for simulation of jaw reflection to avoid unusual biting force were applied as a biological feedback mechanism. By using this robot system, various patterns of muscle loading (change of wire direction and magnitude) were performed. RESULTS: From the results, significant differences in the amount of principal strain and its distribution were demonstrated in each condition (ANOVA, post hoc test, and p < 0.05). The value of maximum principal strain ranged from 79.66 x 10(-6) [at anterior border of ramus (Buccal side), 128 N] to -1.42 x 10(-6) [at foramen mentale (Buccal side), 32 N]. CONCLUSION: These results suggested that the muscle loading generated the mechanical strain on the mandibular bone surface and it was affected by the changes in loading direction and magnitude.
OBJECTIVES: To examine the radiomorphometric indices of the mandible on panoramic radiographs in a population of British female patients, to identify their normal ranges and to investigate their relationships with age, detentition and social class. METHODS: Five indices, cortical width at the gonion (GI) and below the mental foramen (MI), the panoramic mandibular index (PMI), the mandibular cortical index (MCI) and one new index (measurement of cortical width at the antegonion; AI), were measured bilaterally on 500 panoramic radiographs of females by one trained observer. The measurements were analysed for ease of application, repeatability, relationships with age, dentition and social class and interrelationships between the variables. RESULTS: All quantitative indices (GI, MI, PMI, AI), showed a significant, negative correlation with age. MCI showed an age-related distribution. Mandibular dentition exerted a significant influence on some indices, but social class had no influence. Intra-observer repeatability of MI, PMI and AI was fair (precision < 20%) but that for GI was poor. Intra-observer agreement in MCI assessments was excellent. CONCLUSIONS: The age-related changes in mandibular radiomorphometric indices and their variation within each age band lend support to their potential use in identification of skeletal osteopenia. However, problems with repeatability and measurement precision identified in the pilot study, notably with GI, may be a considerable obstacle to their use in general practice.
This study examined the tissue level mineralisation density distribution in mandibles from 88 adult humans. Mandibles (19-96 y) were sectioned vertically in midline (MID), mental foramen (MF), and third molar (M3) regions. Surgical fragments from M3 were obtained from individuals aged 16-38 y. All specimens were cleaned, embedded in PMMA, micromilled and examined by digital 20 kV backscattered electron (BSE) stereology. Quantitation was based on rescaling image histograms to the signal range between a monobrominated (0) and a monoiodinated (255) dimethacrylate resin standard. Mineralisation density increased with age (r=0.70; P < 0.0001): the mean for 39 individuals aged between 16 and 50 y was significantly lower (P < 0.0001) than for 35 individuals over 51 y (mean (+/-S.E.M.): 158.20 (1.63) and 174.71 (1.27) normalised grey level units respectively). There was good correlation in mean mineralisation density between different sites in the same mandible, but MID was significantly less highly mineralised than the other sites: MID 173.90, MF 177.34, M3 177.11 (P < 0.002 and 0.01 for MF and M3 respectively; paired t test), as was the alveolar bone density when compared with the bone of the inferior cortex (e.g. MID: 171.13 (1.53) and 174.46 (1.14) P < 0.0001). No sex difference was found. Partially dentate mandibles generally had regions of higher mineralisation than fully dentate and edentulous mandibles. The lowest density bone occurred at the alveolar crest anteriorly and superolingually at M3, matching sites of net resorption following tooth loss. Highest densities were found inferolingually at MID, inferiorly at MF and buccally at M3, matching the sites thought to experience the highest functional strains. This stresses the importance that local factors may have in the remodelling of the edentulous mandible. Morphology showed that there is a preponderance of highly mineralised cement lines, and of packets containing dead, mineralised, osteocytes.
It is widely accepted that Meckel's cartilage in mammals is uncalcified hyaline cartilage that is resorbed and is not involved in bone formation of the mandible. We examined the spatial and temporal characteristics of matrix calcification in Meckel's cartilage, using histochemical and immunocytochemical methods, electron microscopy and an electron probe microanalyser. The intramandibular portion of Meckel's cartilage could be divided schematically into anterior and posterior portions with respect to the site of initiation of ossification beneath the mental foramen. Calcification of the matrix occurred in areas in which alkaline phosphatase activity could be detected by light and electron microscopy and by immunohistochemical staining. The expression of type X collagen was restricted to the hypertrophic cells of intramandibular Meckel's cartilage, and staining with alizarin red and von Kossa stain revealed that calcification progressed in both posterior and anterior directions from the primary centre of ossification. After the active cellular resorption of calcified cartilage matrix, new osseous islands were formed by trabecular bone that intruded from the perichondrial bone collar. Evidence of such formation of bone was supported by results of double immunofluorescence staining specific for type I and type II collagens, in addition to results of immunostaining for osteopontin. Calcification of the posterior portion resembled that in the anterior portion of intramandibular Meckel's cartilage, and our findings indicate that the posterior portion also contributes to the bone formation of the mandible by an endochondral-type mechanism of calcification.
PURPOSE: The goal of this study was to quantify the amount of bone graft material present in the mandibular symphysis as well as to determine the maximal size of the corticocancellous bone block that can be harvested while avoiding mental nerve injury, tooth injury, and simultaneously preserving the preoperative facial contour. MATERIALS AND METHODS: Sixteen fixed dentate cadaver mandibles were studied. Osteotomies were performed in a monocortical fashion, 5 mm anterior to the mental foramen, cephalad to the inferior border of the mandible, caudal to the expected position of the apices of the anterior teeth, and at the midline. The size of the corticocancellous block was then measured. Bone volume, using 2 techniques, was measured by displacement volumetry. RESULTS: The average volumes obtained were 4.84 mL and 4.71 mL (range, 3.25 to 6.50 mL), respectively, for the 2 techniques of volumetry. The average block size was 20.9 x 9.9 x 6.9 mm; the smallest block was 21.0 x 6.5 x 6.0 mm, and the largest was 25.0 x 13.0 x 9.0 mm. CONCLUSION: Based on the results of this study, it is apparent that the mandibular symphysis can be reliably selected as the harvest site in a variety of oral and maxillofacial reconstructive procedures.
Because of the limited space available in the mandible, especially in the mental foramen and apical region, miniature osteosynthesis material is desirable. Recently, metal deposition in the direct neighbourhood of osteosynthesis plates made of titanium or even in peripheral organs have been reported in the literature with increasing frequency. The size and amount of osteosynthesis material used should therefore be kept to a minimum. In an experimental study on 60 models, we examined load-carrying stability and in a second series, torsional strength of two-piece plastic models connected by either a single miniplate, two miniplates, or a titanium microplate plus a miniplate. In our test arrangement, the average loading capacity of the combination miniplate/miniplate was 470 N: that of the combination microplate/miniplate was only 267 N. The test group with the single miniplate had an average loading capacity of only 225 N. Masticatory loads on the plates exceeding 200 N occur only 3 months after osteosynthesis. At that time the fracture has largely consolidated. The torsional strength of the microplate/miniplate combination was similar to that of the miniplate/miniplate combination (1,000 Nmm resulting in a width of the gap measuring 0.8 mm and 0.5 mm, respectively). The single miniplate was considerably less stable (0.8 mm gap width as early as with 300 Nmm). According to Champy, rotational forces in the anterior region of the mandible amount to approximately 1,000 Nmm and need to be withstood by the osteosynthesis material. Our results suggest that treatment of fractures in the interforaminal region with a combination of microplate and miniplate will be stable enough for early mobilization.