Kortikalisdicke am Unterkiefer unter besonderer Berücksichtigung der Miniplattenosteosynthese

Thirty-two human mandibles were marked with three typical fracture lines: a low condylar fracture, a fracture of the mandibular angle, and one through the mental foramen on each side. The mandibles were sectioned at the fixation sites of the miniplate screws. The thickness of the cortical layer was measured with a scaled magnifying glass at the points of anthropological interest and at the marked screw holes. The inferior cortical layer turned out to be thickest in the anterior area. In contrast, it was very thin at the mandibular angle, which might explain the higher complication rate in treating fractures in this region. The thickness of the lingual cortex increased up to the symphysis, whereas the buccal cortical layer showed a decline in size from the mandibular angle up to the chin. The cortical bone at the alveolar ridge was porous. The cortical supply for miniplate osteosynthesis at the condylus ranged from 1.11 mm up to 1.74 mm, which seems to be limited, but due to the small diameter of the condylus most common screws obtain additional anchorage in the inner cortex. The thickness of the cortical layer at the mandibular angle increased from 1.47 mm at the ramus up to 1.97 mm at the beginning of the corpus, reaching 2.14–2.38 mm for the lower plate at the mental foramen. The results for the upper plate were slightly lower.     

Macroanatomic and radiologic characteristics of the superior genial spinal foramen and its bony canal

PURPOSE: To determine the incidence, size, location, course, and content of the superior genial spinal foramen and its bony canal. MATERIALS AND METHODS: Three hundred eighty dry human cadaver mandibles were morphometrically analyzed by measuring the distance from the foramen to the mandibular base and the size of the foramen and bony canal. Radiologically, the course of the bony canal and its relation to the mandibular incisive canal were investigated after injecting contrast medium (Omnipaque) in the superior genial spinal foramen and the incisive canal at the level of the mental foramen or by inserting a thin metal wire into the bony canal. Dissection was performed on another 10 intact cadaver mandibles. RESULTS: A distinct foramen was present in 98% of all dry specimens studied. Its general form was round or flattened funnel-shaped. Upon microanatomic dissection, a distinct branch of the lingual artery and the lingual nerve entering the superior genial spinal foramen were found. CONCLUSIONS: The superior genial spinal foramen is present in most human mandibles and appears to be the entrance of a true lingual neurovascular bundle passing into the bone via a well-defined bony canal toward the buccal side. This implies that surgery and more specifically implant placement at the mandibular midline may carry some risk of neurovascular damage.     

Anatomic assessment of the anterior mandible and relative hemorrhage risk in implant dentistry: a cadaveric study

Objectives: To evaluate prevalence, size, location and content of foramina and bony canals located on the lingual side of the mandibular midline.
Material and methods: The prevalence and the size of midline lingual foramina and canals visible above and/or below genial spines and their distances from the mandibular base were measured in 60 dry mandibles from adult human cadavers. In addition, macro-anatomic dissections were performed on another 20 mandibles injected with red latex to investigate the vascular canal contents associated with these midline lingual foramina and canals.
Results: A total of 118 foramina were detected. All mandibles investigated had at least one lingual foramen at the midline above the genial spines, located at a mean height of 12.5±2.1 mm (SD) from the inferior border of the mandible. Macro-anatomic dissections showed a clear vascular branch entering the mandibular midline as a single vessel from a sublingual-sublingual anastomosis in 19 out of 20 mandibles studied (95%).
Conclusion: Blood vessels in the floor of the mouth may be in close proximity to the lingual cortical plate of the mandibular midline in most cases. This implies that bleeding can occur when the mandibular cortical plate is perforated even minimally. As a consequence, the authors suggest a careful planning of implant positioning at mandibular midline, possibly opting for the use of an even number of implants in the interforaminal region, avoiding the risk of surgical trauma to the lingual cortical plate of the mandibular midline.     

Studies of residual ridge resorption. Part I. Use of panoramic radiographs for evaluation and classification of mandibular resorption

This article describes a method of estimating the severity of mandibular bone resorption by using the mental foramen and the inferior border of the mandible, as they appear in panoramic radiographs, as reference points.Measurements of 260 images in panoramic radiographs of normal mandibles reveal that, in a high percentage of films, regardless of the usual magnification or distortion of the images, the lower edge of the mental foramen lies very close to a line dividing the mandible into thirds. By using the approximate ratio of 3:1, the original height of the mandible can be conveniently estimated from the height of the lower edge of the foramen above the inferior border of the mandible. The reduction in height of the bone can then also be estimated.It is suggested that this method of estimating and describing the degree of bone resorption may facilitate the study of this disease by providing an anatomic basis for classifying or grouping patients affected to varying degrees.     

Definitive surgical correction of the deformity resulting from hemimandibular hyperplasia.

INTRODUCTION: The asymmetric deformity of the mandible resulting from the rare condition of hemimandibular hyperplasia has posed a challenge for aesthetic surgical correction. The literature relating to this condition is reviewed and the results of treatment in a series of patients described. MATERIAL AND METHODS: A series of treated patients is reviewed and the results of surgery illustrated and discussed. A maxillary Le Fort I osteotomy is first performed where levelling of the occlusal plane is required. The mandibular surgical technique commences with an extended sagittal ramus osteotomy with dissection of the inferior dental neurovascular bundle completely free of the mandible up to and including the mental foramen. The proximal fragment is then rotated cranially leaving undisturbed the soft tissue attachments at the inferior border, with corresponding bone reduction at the upper border. The inferior border of the distal fragment is then reduced to match the new position of the lower border of the proximal fragment, the neurovascular bundle repositioned, and rigid fixation applied. Finally, a straightening genioplasty is performed. RESULTS: It was possible to overcome the technical and anatomical difficulties associated with correction of this hemimandibular deformity and to achieve a good aesthetic result with acceptable facial symmetry when applying this surgical technique in 3 patients. CONCLUSION: Hemimandibular hyperplasia can be surgically corrected with good aesthetic and functional results and minimal morbidity.     

Anatomical study of the complications of intraoral vertico-sagittal ramus osteotomy.

PURPOSE: The present study was performed to determine the variations in anatomical features of the ramus and the course of the maxillary artery to reduce the risk of injury during intraoral vertico-sagittal ramus osteotomy (IVSRO). MATERIALS AND METHODS: The locations and sizes of anatomical features of the medial aspect of mandibular rami were measured in 94 bilateral sides of 47 dry mandibles as a control group, and the results were compared with 3-dimensional computed tomography images of 44 sides of 22 patients with prognathism. We also dissected 12 sides of 6 mandibles from cadavers in a simulated IVSRO procedure to determine the course of the maxillary artery near the medial aspect of the ramus. RESULTS: In the dry mandibles and patients with prognathism, the mandibular foramen was located slightly posterior to the center of the width of the mandibular ramus, and the lingula tip was located about one third the distance from the sigmoid notch to the inferior border of the ramus. The distance from the lateral margin of the mandibular foramen to the lateral surface of the mandibular ramus ranged from 3.1 to 4.4 mm. However, these distances showed various ranges. In the mandibles from Asian cadavers, the maxillary artery approached close to the ramus and passed lateral to the lower head of the lateral pterygoid muscle. CONCLUSIONS: The position of the mandibular foramen in rami varies among individuals and, therefore, should be confirmed preoperatively on axial CT images. In addition, the maxillary artery approaches close to the medial aspect of the sigmoid notch in many cases. Therefore, the medial aspect from the sigmoid notch should be exposed carefully in the IVSRO procedure to avoid damaging the maxillary artery.     

下颌正中管的锥形束CT成像研究

目的 通过锥形束CT（CBCT）对下颌正中管（MIC）的三维位置、走向及毗邻关系进行测量,为确保颏孔前区域牙种植手术的安全提供依据。方法 回顾80例患者的双侧下颌骨CBCT影像,对MIC的直径和毗邻关系进行测量分析,包括MIC至下颌下缘、下颌牙根尖、下颌骨颊侧壁和舌侧壁,以及双侧颏孔连线平面的垂直距离。结果 80例患者中,63例（占78.75%）的CBCT影像上可以观测到MIC影像,其管径大小为（1.21±0.29）mm。在垂直方向上,MIC距下颌下缘和下颌牙根尖的距离分别为（7.82±1.86）、（7.24±2.82）mm;在颊舌方向上,MIC距下颌骨颊侧壁和舌侧壁的距离分别为（3.80±1.37）、（4.45±1.34）mm;MIC距双侧颏孔连线平面的垂直距离为（5.62±2.21）mm。结论 CBCT通过多平面重建后,可以清晰显示MIC在下颌骨中的三维空间位置、走向及毗邻关系;利用CBCT 对MIC的位置和走行进行研究是可行的。     

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.     

Use of an 'osteocompressor' to avoid damage to the inferior alveolar nerve in the mandibular setback procedure: can the positive effects of osteodistraction be used in reverse? An experimental study in dogs

We have designed an osteocompressor to try and avoid damage to the inferior alveolar nerve during sagittal split setback osteotomy of the mandibular ramus, and tested it on the mandibles of 10 dogs. The osteocompressor bears a superficial resemblance to an osteodistractor, but has a different internal structure that allows it to compress rather than distract. We were able to compress the neurovascular canal, the neurovascular bundle, the cancellous bone, and the mandible in dogs at a rate of 1 mm/day by rotating the screw of the compressor 1.5 times. We conclude that in dogs the neurovascular canal and neurovascular bundle can be compressed with this device without loss of sensation. We believe that this is the first publication on nerve canal compression and osteocompression.     

Clinical and anatomical study of retromolar foramen and canal.

PURPOSE: The retromolar canal is a rare anatomic variation of the mandible. The neurovascular content of the mandibular retromolar canal is very important for surgical procedures involving the retromolar area and there has been a lack of information on this subject. This study consists of anatomic research of the retromolar foramen and canal, planned after an impacted third molar tooth extraction operation in which we encountered a retromolar neurovascular bundle. MATERIALS AND METHODS: Eighty sides of 40 mandibles were evaluated and the presence of the retromolar foramen and its relation to the last teeth, the transverse and sagittal distances of the retromolar trigone, and the distance of the retromolar foramen to the last socket of the arch were measured. RESULTS: The neurovascular bundle includes striated muscle fibers, thin myelinated nerve fibers, numerous venules and a muscular artery. Of the 40 mandibles included in this study, retromolar foramens were found in 10 (25%). The presence of the retromolar foramen is not dependent on the last teeth of the arch. The dimensions of the retromolar trigone were measured and the presence of the retromolar foramen was found to be nonrelevant to the dimensions of the retromolar trigone. Retromolar foramen distance from the distal edge of the last socket of the arch was found to be 11.91 +/- 6.71 mm and 4.23 +/- 2.30 mm, respectively, from the second and third molars. CONCLUSIONS: This study therefore clearly establishes the incidence and importance of the retromolar canal. This study shows that the retromolar foramen and canal can be seen occasionally in routine dental surgery. Due to the neurovascular bundle passing through it, the retromolar canal and foramen must be kept in mind in all anesthetic and surgical approaches regarding the retromolar area and mandible.     

螺旋型牙种植体下颌磨牙区种植的尝试

磨牙区种植对种植义齿修复，特别是下颌总义齿的稳固和Ｈｅ力均匀分布非常重要。但是，由于下颌管走行于下颌骨体中间，盲目种植会损伤下齿槽神经和血管。作者采取Ｘ线测量，根据所测下颌管上壁至牙槽嵴顶的距离，选用一定长度的固位钉作种植；和对骨吸收严重者由下颌管上方去除舌侧骨板，解剖游离该神经血管束将其避开，选长钉植入，可抵达下颌下缘皮质骨，解决了此类病人磨牙种植的难题。作者对磨牙区种植的适应证、手术方法及可能     

Dual-photon absorptiometry of mandibles: in vitro test of a new method

A new method for non-invasive in vivo measurement of changes in bone mineral content (BMC) of mandibles, comprising two-dimensional dual-photon absorptiometry (GT45), has been developed and tested in vitro on mandibular specimens. The analysis showed that: 1) in vitro precision and accuracy of the methods are high, 2) effect of fat and soft tissue on photon attenuation is slight when scanning jaws and forearm bones, 3) BMC in units (U/cm2) in standard area, comprising mandibular base and body in left molar region, is representative for BMC in total mandibular base and body, 4) cortical bone constitutes the main part of measured BMC in mandibles, and 5) BMC of molar region is highly correlated to cortical bone mass in mm3/mm2 subperiosteal surface of standard locality anterior to and below mental foramen, measured by histomorphometry. GT45 seems suitable for in vivo estimation of BMC changes in edentulous jaws and in mandibular base and body of dentate mandibles in longitudinal and cross-sectional studies. The radiation dose is negligible.     

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.     

The Anatomic Inter Relationship of the Neurovascular Structures Within the Inferior Alveolar Canal: A Cadaveric and Histological Study

Objective

The location and inter relationship of the structures of the inferior alveolar neurovascular bundle within the mandibular canal has not been clearly defined. The knowledge of the same is important while planning surgeries in the posterior mandible.

Methods

Eight cadaveric mandibles were dissected and sections were made at the distal aspect of every tooth. The inferior alveolar neurovascular bundle was identified and examined for the location of the inferior alveolar artery, vein and nerve. Hematoxylin and Eosin sections were made for each specimen to confirm the position of these structures.

Results

All the sections in all the specimens confirmed that a blood vessel lies superior to the nerve. This position appeared consistent in all the positions relative to all the posterior teeth. There was a variation in the bucco-lingual positioning of these structures relative to each other for the various mandibles.

Conclusion

A blood vessel is found to always lie superior to the inferior alveolar nerve within the mandibular canal. Variations in the inter relationship of the structures is present.

Significance

This cadaveric study proves that all along the course of the neurovascular bundle, at various cross-sections studied, the inferior nerve is always inferior to a blood vessel. There can be great variations to the positioning of the structures within the neurovascular bundle in the bucco-lingual dimension and also in the exit of the nerve in various mandibles. Knowledge of the location of the structures is of importance during surgical procedures carried out in the vicinity of these structures.     

Accuracy of using the antilingula as a sole determinant of vertical ramus osteotomy position.

PURPOSE: The antilingula is an important landmark in mandibular ramus surgery. Its relationship to the lingula provides useful clinical information as to the position of the mandibular foramen and inferior alveolar nerve. The purpose of this study was to determine the reliability of using the antilingula as a guide to osteotomy placement for intraoral vertical ramus osteotomies. MATERIALS AND METHODS: Eighteen cadaver mandibles were harvested and the antilingula was identified on each hemimandible by palpating the most prominent bulge on the lateral aspect of the mandible. In addition, the lingula (the entrance of the mandibular neurovascular bundle into the medial aspect of the ascending ramus of the mandible) was identified. A 1 mm fissure bur was used to drill a hole perpendicular to bone, from the deepest aspect of the concavity at the center of the lingula. The drill perforated both the medial and lateral cortices of the mandible. The distance from the antilingula to lingula was measured and recorded in both the anterior-posterior and the superior-inferior planes. RESULTS: There was complete concordance of the position of the lingula and antilingula in the anterior-posterior dimension in 11.1% of the specimens. In 33% of the specimens, the lingula was found anterior to the antilingula and in 45.6% the lingula was found posterior to the antilingula. There was complete concordance of the lingula and antilingula in the superior-inferior dimension in 2.8% of specimens. The lingula was found superior to the antilingula in 47.2% of the specimens and inferior to the antilingula in 50% of samples. CONCLUSION: In most instances, the position of the lingula was posterior-inferior relative to the position of the antilingula. At a measurement of 5 mm posterior to the antilingula (at the level of the antilingula), there was no risk of damaging the neurovascular bundle in this cadaveric study.     

Intraosseous course of the inferior alveolar (dental) nerve and its relative position in the mandible.

The present study was planned to evaluate the position of the mandibular foramen (MF) and the course of the inferior alveolar nerve in 12 right and 14 left cadaveric hemimandibles. The soft tissue including the muscle attachments of the mandible was cleaned and the inferior neurovascular bundle was dissected up to the MF. The distances from the MF to the angle, symphysis menti, 3rd molar, and the lower point of the mandibular notch were measured. The bone was chiseled from its lingual surface to expose the mandibular canal. The distances from the nerve to the alveolar and inferior borders were measured. The distance from the MF to different landmarks did not show any side differences except the one to the symphysis menti (P<0.05; Mann-Whitney 'U' test). Similarly the distances from the nerve to the borders also did not show any significant side differences. These data indicate that, on average, MF is located at a symmetrical point on the ramus on either side, although, not exactly at a fixed distance from any landmarks tested. Further, the canals were located either at near to the middle or below near to the base of the mandible. This study concludes that, the location of the MF varies from bone to bone despite its bilateral symmetry. Further, the canal and consequently the nerve do not maintain a constant position in the mandible.     

细长型髁突增生病下颌骨及下颌神经管位置CT形态学研究

目的应用CT进行细长型髁突增生病（HE）下颌骨解剖学及下颌神经管形态学研究,为临床治疗提供参考。方法对19例HE患者进行多层CT扫描,采用Mimics 10.0软件进行三维重建,在不同断面重建图像,进行下颌神经管、下颌孔和骨皮质测量,并与无下颌骨病变的对照组进行比较。结果在第一磨牙中心长轴断面的舌侧、第二磨牙中心长轴的颊侧及上缘、磨牙后区中心至下颌角连线断面的颊侧、上缘及下缘、下颌孔下缘下5 mm处水平位断面的舌侧、前缘及后缘,2组下颌神经管外缘距下颌骨表面距离的差异具有统计学意义（P<0.05）;在第一磨牙颊侧和下缘,2组下颌骨骨皮质厚度的差异具有统计学意义（P<0.05）;2组下颌孔至下颌升支前缘及下颌骨下缘距离的差异具有统计学意义（P<0.05）。结论细长型髁突增生病骨皮质厚度从下颌第一磨牙到下颌升支在各个方向均逐渐减小。与正常颌骨相比,下颌神经管在下颌第二磨牙及磨牙后区偏颊侧并靠上方,下颌孔在升支内侧较靠前并偏低。     

The Study of Antilingula and Its Relation to the Lingula and Mandibular Foramen,the Presence of Mylohyoid Bridging in Dry Mandibles of South Indian Population

Background and Objectives

The mandibular foramen and the lingula, because of their relation to the inferior alveolar nerve are of clinical significance for the orodental surgeons. Identification of the antilingula is important in mandibular ramus surgery in which the medial surface of the ramus is not visualized.

Methods

The present study includes adult dry 50 mandibles of unknown age and sex. The measurements were taken using vernier calipers. The points taken for measurements were most prominent point on antilingula, tip of lingula, most anterior, posterior and inferior points of mandibular foramen. The measurements were denoted as A, B, C and D which represent the anterior, posterior, superior and inferior distances.

Results

Antilingula was present on right side in 25 and on left side in 28 mandibles. There was a significant difference in distances in mean between the antilingula and mandibular foramen of both the sides (p < 0.001). Retromolar foramen was observed in 6 mandibles. Mylohyoid bridging was seen in 3 mandibles.

Conclusion

The mandibular foramen was located posterosuperior to the antilingula on both the sides. There was no statistical significance in the distances between the lingula and the antilingula. Therefore antilingula can be used as an important surgical landmark for locating the mandibular foramen in mandibular ramus osteotomies.     

A review of the intraosseous course of the nerves of the mandible.

A review of the literature revealed that a common feature of all human mandibles is a large nerve (inferior alveolar nerve, IAN) between the mandibular and mental foramina. This nerve sends branches directly to the teeth or contributes a variable number of branches to a plexus of nerves which does the same. The plexus originates from a separate nerve that enters the mandibular foramen. The nerve plexus has been demonstrated by dissections and not by radiology. The buccal-lingual and superior-inferior positions of the IAN were not consistent among mandibles. The intramandibular IAN frequently ran a concave curve with a posterior segment descending as it progressed anteriorly and an anterior segment that ascended to the mental foramen. A bony canal was not always observed between the mandibular and mental foramina. The canal frequently lacked definite walls, especially near the mental foramen. Bilateral symmetry (location of the canal in each half of the mandible) was common, whereas duplications of the canal were rare. Nutrient canals and other branches of the mandibular nerve have been observed within the mandible. These may have been confused for the IAN or may contribute to the plexus of nerves.     

The mental foramen: 1. Size, orientation, and positional relationship to the mandibular second premolar

Seventy-five adult human mandibles were examined to determine the size, orientation, and position of the mental foramen. The average size of the foramen was found to be larger on the left side of the mandible and its usual direction of exit was in a posterior-superior direction. The most common location of the mental foramen was inferior to the crown of the second premolar and approximately 60% of the distance from the buccal cusp tip of that tooth to the inferior border of the mandible.