Variations in the size and location of the mental foramen.
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Adult↗
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Mandibular radiomorphometric indices in the diagnosis of reduced skeletal bone mineral density.
Diagnosis of osteoporosis allows the delivery of preventive and therapeutic intervention and is usually achieved using bone densitometric techniques. One referral criterion for densitometry is osteopenia on radiographs. The aim of this study was to measure the validity of mandibular cortical indices measured on panoramic radiographs in the diagnosis of reduced skeletal bone density. Seventy-four women underwent bone densitometry of the femoral neck, lumbar spine and the forearm. Fifty-five patients (74%) were classified as having a reduced bone density (T-score < or = -1). Twenty-seven patients had a T-score of < -2.5 observed at one or more of the three measurement sites. A panoramic radiograph was taken of each patient and two observers made measurements of cortical thickness at the mental foramen (mental index, MI), antegonion (antegonial index, AI) and gonion (gonial index, GI) regions. Logistic regression and receiver operating characteristic (ROC) curve analyses were used to measure the validity of cortical indices in the diagnosis of reduced bone mineral density. Only MI contributed significantly to a diagnosis of low skeletal bone mineral density (T-score < or = -1). The 95% limits of agreement between observers in measurement of MI were 1.32 to +1.32 mm. When data for both observers were combined, the area under the ROC curve was 0.733 (SE = 0.072; 95% confidence interval = 0.618 to 0.83), indicating moderate accuracy. A diagnostic threshold for MI of 3 mm (or less) is suggested as the most appropriate threshold for referral for bone densitometry. However, the study provided only limited support for the use of panoramic radiomorphometric indices in diagnosing low skeletal bone mineral density. They might, questionably, be used as part of a method of osteoporosis risk assessment.
Absorptiometry, Photon↗
Odontogenic cysts: improved imaging with a dental CT software program.
PURPOSE: To evaluate a dental CT software program to determine whether it can provide a better means of assessing odontogenic cysts, lesions of the jaw derived from dental epithelium, than conventional techniques (orthopantomographic, intraoral, and mandibular films), which are of limited usefulness because of the curved configuration of the mandible; and to provide a brief review of these lesions. METHODS: Nine odontogenic cysts were studied with conventional radiographs and with the software program, which displays multiple cross-referenced axial, panoramic, and cross-sectional (unique to this program) views of the mandible. The two modalities were compared for delineation of anatomy (inferior alveolar canal, mandibular foramen, mental foramen), detection of neurovascular bundle displacement, detection of cortical bone involvement, and detection of root involvement. RESULTS: The software program rated higher regarding all four points. It was found to be superior for delineating anatomy and detecting mandibular canal displacement and cortical and root involvement. CONCLUSIONS: This software program should be the study of choice when evaluating odontogenic cysts and other lesions of the mandible.
Adolescent↗
[Anatomic-roentgenologic study of the mandibular canal in atrophic mandible].
This study analyses the changes observed with atrophy of the mandibular foramen and mental foramen, as well as the mandibular canal. All 43 left halves of the examined mandibles were systematized according to the classification of the reduction of residual ridges by Atwood. This classification allows a precise description of the rate of atrophy. An evaluation of the results of computed tomography and X-ray, as well as measurements of the mandibles showed a number of significant atrophic changes. With extreme reduction of residual ridges the mental canal is significantly shortened. Increasing atrophic change causes the mental foramen to approach both the alveolar ridge and the basic tangent line. The distance of the mandibular canal to the lingual and buccal surface remains constant, whereas the distance to the cranial and caudal surface is markedly reduced according to the degree of atrophy. The mass of compact and spongy bone tissue is reduced to a level of 50% or less of the original volume. In general, the cortical lamina around the mandibular canal is more often found on the caudal side than on the cranial side. At extreme rates of reduction of residual ridges the mandibular canal is enclosed by compact bone tissue. The visibility of the mandibular canal and the mental foramen on X-ray is significantly reduced by extreme rates of resorption.
Aged↗
Repositioning the inferior alveolar nerve for placement of endosseous implants: technical note.
Placement of implants in the posterior mandible is limited by the height of bone between the alveolar crest and the inferior alveolar canal. This paper discusses a surgical technique to reposition and protect the neurovascular bundle so that endosseous implants may be placed. A rectangular window is cut in the cortical bone posterior to the mental foramen. The mental foramen is not violated and the mental nerve is not relieved peripherally into the soft tissue. Cancellous bone is removed from the window and the canal is uncovered. A vessel loop placed around the bundle repositions and protects the nerve laterally. After implant placement, the bundle is replaced within the cortical window and the mucoperiosteal flap is sutured. Avoiding manipulation of the terminal branches of the inferior alveolar nerve reduces the risk of permanent nerve damage.
Aged↗
Preliminary quantitative microradiography study into the distribution of bone mineralization within the basal bone of the human edentulous mandible.
Six edentulous human hemimandibles (three male, three female) of similar ages were sectioned transversely at the midline, mental foramen, midway between mental foramen and angle (body), and angle of the mandible. Planoparallel sections were prepared of the cortical plate on buccal and lingual surfaces and microradiographed alongside an aluminium step-wedge for computerized quantitative microradiography. Mean mineralization values and mineralization frequency distribution curves were calculated. Gender had no effect on the mean mineralization values, but did show a significant difference in the mineralization frequency distribution. There was no difference in mean mineralization between lingual and buccal cortical plates, but the distribution curves differed, with the lingual cortex distributions being more uniform. Each sample site was significantly different from all others, with the mental foramen and body sites showing the greatest variation in distribution of mineralization level.
Aged↗
Frequency variations of discrete cranial traits in major human populations. IV. Vessel and nerve related variations.
This concludes a series of descriptive statistical reports on discrete cranial traits in 81 human populations from around the world. Four variants classified as vessel and nerve related characters were investigated: patent condylar canal, supraorbital foramen; accessory infraorbital foramen; and accessory mental foramen. A significant asymmetric occurrence without any side preference was detected for the accessory mental foramen. Significant intertrait associations were found between the accessory infraorbital and supraorbital foramina in the panPacific region and Subsaharan African samples. The intertrait associations between the accessory infraorbital foramen and some traits classified as hypostotic were found mainly in the samples from the western part of the Old World, and those as hyperostotic traits in the samples from eastern Asian and the related population samples. With a few exceptions. the occurrence of a patent condylar canal and a supraorbital foramen was predominant in females, but the accessory infraorbital and accessory mental foramina were predominant in males. The frequency distributions of the traits showed interregional clinality and intraregional discontinuity. A temporal trend was found in the Northeast Asian region in the frequencies of the accessory infraorbital and accessory mental foramina. The diversity of modern human discrete cranial traits may at least in part be attributable to differential retention or intensification from an ancestral pattern.
Blood Vessels↗
The mandibular incisive foramen.
An anatomical variant in the region of the mental foramen is discussed. In these cases the inferior alveolar nerve divides into its two terminal branches only after it has exited through the mental foramen. The incisive nerve thus commences outside the mandible, and has a short extra-osseous course before it enters the mandible through a separate foramen on the same horizontal plane. For the distance between these two foramina there is no nerve supply within the mandible. The groove between the two foramina may be the remnants of the mandibular canal. The foramen through which the nerve enters the bone is a separate anatomical entity from the mental foramen and should be recognised as such. It is proposed that this foramen be named the mandibular incisive foramen.
Humans↗
Vulnerability of the inferior alveolar nerve and mental nerve during genioplasty: an anatomic study.
Microgenia or "small chin" is corrected by various techniques, such as insertion of an alloplastic implant, cartilage or bone grafting, or horizontal advancement osteotomy. Horizontal recession osteotomy is used in macrogenia. Particularly in a microgenic mandible, the mental foramen is unexpectedly nearer to the inferior border of the body. During sliding horizontal osteotomy of the mentum, the inferior alveolar nerve (IAN) and mental nerve are vulnerable to an injury. Thirty fresh hemimandibles were used for a study of the IAN. The IAN course was traced by serial sections at intervals of 5 mm. In 50 dry specimens the direction of the mandibular canal was evaluated by the photographs with a stick put into the mental foramen. The IAN in mandibular canal runs above the lower one-third of the mandibular body. The terminal mandibular canal locates at an average of 4.5 mm under the mental foramen, advances 5.0 mm anteriorly, loops, and ends at the foramen. The direction of the mandibular canal at the mental foramen was 39.4 degrees lateral, 67.2 degrees superior, and 80.2 degrees posterior. It is advisable for surgeons to keep the level of sliding osteotomy of the mentum at least 4.5 mm below the mental foramen to spare the IAN.
Cadaver↗
[Peripheral branches of the facial nerve in the cheek and chin area. Anatomy and clinical consequences].
The available descriptions of the innervation of the depressor anguli oris muscle and the peripheral distribution of the terminal branches of the marginal mandibular branch and buccal branches of the facial nerve are conflicting. Based upon dissections of 25 head halves we investigated the courses of the terminal branches of the marginal mandibular and buccal nerves. The marginal mandibular and buccal branches were found to form in the area of the mental foramen the mental and buccal plexus innervating the mimetic muscles by terminal nerve branches in the cheek area. The buccal plexus supplied the muscles of upper lip, cheek and nose. Furthermore, the depressor anguli oris muscle was also supplied by the buccal plexus. We also observed connections between marginal mandibular branch and mental nerve and between buccal branches of the facial nerve and buccal nerve of the trigeminal nerve. In case of injury to the marginal mandibular branch the depressor anguli oris muscle is not affected. Injury to the nerve branches of the depressor anguli oris muscle can be caused by operations or lesions in the area of the posterior border of this muscle.
Aged↗
Canalis sinuosus mimicking a periapical inflammatory lesion.
A case is presented in which an anatomical feature, canalis sinuosus, manifested as a periapical radiolucency on an upper canine. This may have been interpreted as an inflammatory lesion and led to the patient receiving inappropriate treatment had a further radiograph not been taken. The incisive foramen and mental foramen are well known anatomical features which may mimic periapical inflammatory lesions but it is less common for a neurovascular canal to manifest as a periapical radiolucency on an upper canine.
Adult↗
The position and course of the mandibular canal.
Twenty-nine human cadaver mandibles were dissected longitudinally and cross-sectionally for determination of the precise location of the inferior alveolar nerve, artery, and vein. The neurovascular bundle was located in contact with, or very close to, the lingual cortical plate until it reached the mental foramen. Anterior to the mental foramen, the neurovascular bundle was not a distinct entity and was located close to the labial cortical plate. In the body of the mandible, the neurovascular bundle was located about one centimeter above the mandibular inferior border. The distance from the lateral border of the neurovascular bundle to the external surface of the buccal plate was usually half a centimeter in the molar and premolar regions. The mandibular canal was usually formed by a thin bony plate that, grossly, had more of an appearance of trabecular bone; in only a few mandibles was there a thin layer of cortical bone.
Humans↗
[Topographical and morphological study of the mandibular foramen in black Africans from the Ivory Coast].
Sixty one dry mandibles. have been studied to provide some anatomical informations on the position, shape and size of the mental foramen among adults Black Africans of Ivory Coast. According the results, in the male mandibles, the mental foramen lay 27,31 mm behind the symphyses , 74,75 mm forward the post border of the ramus, 14,89 mm above the lower border and 16,16 mm under the alveolar margin. In the female mandibles, the mental foramen lay 27,16mm behind the symphysis, 69,10 mm forward the post border of the ramus, 14,21 mm above the lower border and 15,66 mm under the alveolar margin. This study confirmed that on the horizontal plane, the mental foramen lay approximatively one quarter of the distance from mandibular symphyses to the post border of the ramus. The margin of mental foramina was elliptic in 66,67 % and 64,52 % of the cases respectively in male and female mandibles. The mean sizes of the long and short axes of forarnina were 5,03 mm and 3,97 mm in the male mandibles. These dimensions were 4,99 mm and 3,87 mm in the female mandibles.
Adult↗
Computer-aided system for measuring the mandibular cortical width on dental panoramic radiographs in identifying postmenopausal women with low bone mineral density.
INTRODUCTION: Mandibular inferior cortical width manually measured on dental panoramic radiographs may be useful for identifying postmenopausal women with low skeletal bone mineral density (BMD). Automatic measurement of cortical width may enable us to identify a large number of postmenopausal women with suspected low skeletal BMD. The purposes of this study were to develop a computer-aided system for measuring mandibular cortical width on dental panoramic radiographs and clarify the diagnostic efficacy of this system. METHODS: Panoramic radiographs of 100 postmenopausal women who had had BMD assessments of the lumbar spine and the femoral neck were used in this study. Experienced oral radiologist determined the position of the mental foramen on 100 digitized dental panoramic radiographs. After determination of the mental foramen, mandibular cortical width below the mental foramen was measured automatically with a computer-aided system by identifying the area of interest, enhancing the original image, determining inner and outer margins of the cortex, and selecting an appropriate point. Cortical width measured by this system was compared with BMD of the lumbar spine and the femoral neck. RESULTS: There were statistically significant correlation between cortical width measured by the computer-aided system and spinal BMD (r=0.50) and femoral neck BMD (r=0.54). These correlations were similar with those between cortical width by manual measurement and skeletal BMD. Sensitivity and specificity for identifying postmenopausal women with low spinal BMD by the computer-aided system were about 88.0% and about 58.7%, respectively. Those for identifying postmenopausal women with low femoral neck BMD by this system were about 87.5% and about 56.3%, respectively. CONCLUSION: Our results suggest that our computer-aided system may be useful for identifying postmenopausal women with low skeletal BMD.
Aged↗
Variation in the apparent density of human mandibular bone with age and dental status.
This study examines the variability in the anatomy of mandibles of differing ages and different stages of tooth loss. Mandibles from individuals between 19 and 96 y were sectioned into 2 mm thick vertical plane-parallel slices and cleaned of marrow and periosteum. The apparent density (mass per unit volume in g/ml) from midline (MID) and mental foramen region (MF) sites was determined by weighing the slices and dividing by a volume calculated as the product of section thickness and the mean area of the 2 sides of the section. The cortical thickness of the inferior border and the basal and alveolar bone heights were measured in radiographs of the slices. Mandibular apparent density was negatively correlated with the cross sectional area (midline r=-0.48, mental foramen r=-0.45), and at the midline was significantly greater in edentulous than in dentate individuals (means (+/-S.E.M.) edentulous n=13: 1.43 (+/-0.07) g/ml; dentate n=17: 1.27 (+/-0.04) g/ml, P < 0.05). Where a large enough age range was available, mandibular apparent bone density showed a significant increase with age (midline males: r=0.53, n=18) especially for dentate individuals (r=0.91, n=8). There was a correlation between the apparent densities at the two sites in the same mandible (r=0.64), with the values obtained for the midline being significantly greater than for the mental foramen region (midline 1.34 (+/-0.04) g/ml; mental foramen 1.19 (+/-0.04) g/ml, P < 0.001, paired t test). The mandible shows great interindividual variability, but there may be a considerable reduction in cross sectional girth of the mandible following tooth loss, and, unlike postcranial sites, an increase in apparent density with age.
Adult↗
An anatomical study of mental neurovascular bundle-implant relationships.
When five to six implants are used in a fixed reconstruction, it is desirable to place the most distal implant as close to the mental nerve as possible. This allows the cantilever of the fixed prosthesis to be extended posteriorly as much as is biomechanically feasible. Forty-seven mental nerve regions were dissected on cadavers to determine the exact relationship between the mental foramen, the inferior alveolar nerve, and its two terminal branches--the incisive and mental nerves. The most anterior position in which the mental nerve was encountered was 1 mm forward or mesial to the most anterior aspect of the mental foramen. Based upon this finding, it is likely that damage to the mental nerve can be avoided if the distal surface of the most posterior implant is 1 mm anterior to the anterior border of the mental foramen.
Bone Density↗
Validation of spiral computed tomography for dental implants.
OBJECTIVES: To investigate the accuracy of 2DCT orthoradial reformatted images from spiral computed tomography (CT) for pre-surgical planning of dental implants in proximity to the mental foramen. METHODS: Eight cadaver heads were imaged by spiral CT (S/Xpress, Toshiba-America, Tustin, CA) with 1 mm thick axial slices by 1 mm/sec of table feed. The image data set was transferred to a networked computer workstation. Using computer graphics the data was analysed with 2D orthoradial reformatting using the ToothPix (Cemax, Fremont, CA, USA) protocol. Linear measurements were made by two oral radiologists independently from the superior border of the mental foramen to the crest of the alveolar process and from the inferior border of the mental foramen to the mandibular inferior border. The soft tissues were removed and physical measurements made using a 3 Space (Polhemus, Colchester, VT) electromagnetic digitizer with a personal computer running Windows 95. RESULTS: The differences between the measurements on orthoradial 2DCT images and the physical measurements were not statistically significant (P > 0.05). CONCLUSIONS: Two-dimensional spiral CT imaging allows highly accurate measurements for dental implant placement in proximity to the mental foramen. Computer graphics software, using reformatted reconstruction, is suitable for implant planning.
Aged↗
Locational relationship of the supraorbital notch or foramen and infraorbital and mental foramina in Koreans.
The morphology and locational relationship of the supraorbital notch/foramen, infraorbital foramen, and mental foramen were studied from photographs of 124 Korean skulls (male 35, female 18, unknown sex 71). The infraorbital foramen was on the sagittal plane passing through the supraorbital notch/foramen (36.4%), or lateral to the plane (63.6%). The mental foramen was either on the plane (69.3%), lateral to the plane (21.8%), or medial to the plane (9.0%). The supraorbital notch/foramen, infraorbital foramen, and mental foramen were on the same sagittal plane in 38.1% of the cases. The supraorbital notch (69.9%) was found more frequently than the supraorbital foramen (28.9%). The average distance from the median plane to the center of the supraorbital notch/foramen, infraorbital foramen, and mental foramen was 22.7, 27.2 and 24.4 mm, respectively. The average length of the line from the center of the supraorbital notch/foramen to the center of the infraorbital foramen was 45.6 mm, and the angle of this line to the sagittal plane was 5.8 degrees. The average distance from the infraorbital margin to the center of the infraorbital foramen was 8.6 mm, and that from the inferior margin of mandible to the center of the mental foramen was 15.5 mm in males and 14.0 mm in females. The average horizontal width of the supraorbital notch/foramen, infraorbital foramen, and mental foramen was 4.7, 4.8 and 2.4 mm, respectively. Most commonly, the infraorbital foramen was lateral to the sagittal plane of the supraorbital notch/foramen, and the mental foramen was on that plane. This locational relationship would be helpful clinically to determine the location of the infraorbital and mental foramina, by palpation of the supraorbital notch.
Adolescent↗