Posterior accessory foramina of the human mandible

A study was performed on 150 dry, adult, human mandibles from cadavers of unspecified sex and unknown ethnic background, which had been imported from India. These mandibles were placed in the “standard basal position” and topographically divided into 11 bilateral areas posterior to the second bicuspid teeth. The accessory foramina in these areas were studied to determine their mean diameter, incidence of occurrence, and the areas in which they occurred.The medial surfaces of the mandibles exhibited foramina more frequently and in greater numbers than did the lateral surfaces. The right and left halves of the mandibles showed remarkable similarity. Much of the data obtained correlated with previous investigations, indicating that neurovascular components enter and leave the body on the mandible in the posterior region.Foramina 0.4 mm. or larger in diameter were evaluated separately. These larger foramina occur most often in the superior and middle thirds on the medial surface of the ramus (areas 6 and 7). They also occur fairly frequently in the retromolar area (area 11). This information can be usefully applied to future dissection studies concerning the soft-tissue components of these foramina.The data obtained reveal that these foramina occur frequently and in approximately the same locations. This suggests that these foramina are functionally important in supplying neural and/or vascular components to the mandible.     

Prevalence and implications of accessory retromolar foramina in clinical dentistry

The occurrence of retromolar foramina (RMF) was examined in a sample of dry skulls (African American n = 249; Causcasian n = 226) to consider the potential clinical impact. A prevalence rate of 7.8% of RMF was found. There were no statistical differences based on race or gender. The prevalence may contribute to the explanation of a portion of inferior alveolar nerve block failures and provide insight into potential implications of surgery in the posterior mandible.     

Number of accessory or nutrient canals in the human mandible

Objectives

The aim of the study was to assess the presence, location and the number of accessory or nutrient canals in the body of the mandible by means of cone beam CT images, obtained with the Planmeca ProMax® 3D Max device.

Material and methods

Seventy-four cone beam images of the mandible from adult patients (37 males and 37 females) who were imaged for dental implantology planning or third molar extraction were used to assess the number and location of accessory or nutrient canals. All images were taken with the same machine (Planmeca® ProMax 3D Max) at 200-, 400- or 600-μm resolution. Distinction was made between canals entering or exiting the mandible superior or inferior of the inferior alveolar canal and between similar canals superior or inferior of the genial tubercula.

Results

The number of accessory canals varied between nil to 11. No statistical significant difference between males and females was found with regard to the number or location of accessory canals in the mandible. Only 5.4 % of patients had no accessory canals. One to five accessory canals were found in 71.6 %, and 23 % of patients had more than five accessory canals. The majority (81 %) of patients had between two and six accessory canals.

Conclusion

It seems that subjects showing no accessory canals whatsoever should be considered exceptional as more subjects with than without accessory canals in the body of the mandible were found.

Clinical relevance

These results are clinically relevant for mandibular surgery and mandibular local anaesthesia.     

Variations of the location of the greater palatine foramina in dry human skulls.

Seventy-one adult skulls (58 dentulous skulls: 56 bilateral and 2 unilateral, 13 edentulous: 11 bilateral and 2 unilateral) of unknown sex were examined for the variations of the location of the greater palatine foramen. The location of greater palatine foramen (GPF) was noted with relation to mid sagittal suture (MSS), posterior palatal border (PPB), and maxillary molars by measuring the distances using a sliding caliper to the nearest millimeter. Difference in the distance of the foramen from MSS and PPG in both the skull types was found to be statistically insignificant. Commonest location of the foramen was found to be opposite to third molar tooth (85.95%), followed by the interval between second and third molar teeth (13.15%), and opposite to the second molar tooth (only one case - 0.88%). Well-formed bony canals were found along the groove for the palatine nerves and vessels unilaterally in the right side in two skulls. These observation may be of help to the dental surgeon during the peripheral block of maxillary nerve for the maxillo-facial surgery.     

The practical significance of mandibular accessory foramina

Abstract — Study of dried specimens, dissections, radiographic and histologic examination of 300 human mandibles demonstrated the presence on beth internal and external aspects of the bone, of a number of accessory foramina containing nerve fibres. Clinical experience with 130 patients confirms the importance of these findings. “There is nothing, Sir, too little for so little a creature as man. It is by studying little things that we attain the great art of having as little misery and as much happiness as possible.”—Boswell .     

Scanning electron microscopic investigation of incidence, location, and size of accessory foramina in primary and permanent molars.

OBJECTIVE: The purpose of this study was to determine and compare the incidence, location, and size of accessory foramina in the furcation region of permanent and primary molars. METHOD AND MATERIALS: A random sample of 100 extracted human permanent maxillary and mandibular first and second molars (25 teeth of each type) and a random sample of 100 extracted human primary maxillary and mandibular molars (50 teeth of each type) were used. The crowns and roots of each tooth were removed at a point 1.5 mm apical to the external furcation region, and a second cut was made at a point 1 mm apical to the cementoenamel junction. The specimens were examined using scanning electron microscopy at magnifications ranging from x 10 to x 1,250. The incidence, location, and size of accessory foramina were documented and statistically analyzed. RESULTS: Of the 100 permanent molars examined, 79% had accessory foramina with diameters ranging from 10 microm to 200 microm. Accessory foramina were present in 94% of the primary molars, with diameters varying from 10 microm to 360 microm. The incidence of accessory foramina was significantly higher in primary than in permanent molars. CONCLUSION: The presence of accessory foramina with large diameters may imply that an inflammatory process can spread from pulpal to periodontal tissues and vice versa.     

Prevalence, location, and patency of accessory canals in the furcation region of permanent molars.

One hundred and two extracted permanent molars were debrided in 3% H2O2, sealed at the apex, and placed in a vacuum chamber. Safranin dye was introduced into the teeth that were placed in a vacuum of 525 mm of Hg. Observations were made of the external root surface to determine any staining due to patent accessory canals. Accessory canals were demonstrated in the "furcation region" in 28.4% of the total sample; 29.4% in mandibular molars, and 27.4% in maxillary molars. Of the total sample 25.5% exhibited canals in the "furcation" only, while 10.2% exhibited canals on the lateral root surface. Communication between the pulp chamber and the external surface was noted via dentinal tubules, especially when the cementum was denuded. The salient biologic and pathologic ramification of these aberrant canals were discussed along with the need to establish a differential diagnosis in order to determine the proper sequence of treatment should pulpal-periodontal disease exist.     

A SEM investigation of accessory foramina in the furcation areas of primary molars

The purpose of this study was to determine the prevalence and anatomic characteristics of accessory foramina in the external and internal furcation areas of primary molars. Sixty human primary molars were divided into two equal groups. The teeth of the experimental group showed in previous radiographic examination the presence of a radiolucency area confined to the inter-radicular region, while the teeth of the control group had no sign of pulpal inflammation in the clinical and/or radiographic examination. The specimens were observed by scanning electron microscope (SEM). The external furcation area (EFA) showed a higher prevalence of accessory foramina than the internal furcation area (IFA) (P<0.05). However, the comparison between the two groups did not show statistically significant difference (P>0.05). The presence of accessory canals should not be considered the only reason for inter-radicular pathological bone resorption following pulpal necrosis in deciduous molars.     

Double mental foramina of the mandible on computed tomography images: a case report

Double mental foramina found with preoperative computed tomography (CT) prior to implant therapy are reported and discussed in reference to literature reports. A 52-year-old man visited us for implant therapy. Preoperative panoramic radiography and CT were conducted. A multisection reconstructed sagittal image showed two mental foramina leading to the mandibular canal on the right side of the mandible, which were diagnosed as double mental foramina. The incidence of double mental foramina reported in the literature is approximately 6.9% in dry Japanese skulls. Many reports have indicated that non-Caucasians have a higher incidence than Caucasians. The general incidence ranges from 2% to 10%. However, only one clinical case report is available.     

A scanning electron microscopic investigation of accessory foramina in the furcation and pulp chamber floor of molar teeth

Observations of the pulp chamber floor and furcation surface of human maxillary and mandibular first and second molars were made with the scanning electron microscopic to determine the incidence, size, and location of patent accessory foramina. Accessory foramina on both the pulp chamber floor and the furcation surface were found in 36% of maxillary first molars, 12% of maxillary second molars, 32% of mandibular first molars, and 24% of mandibular second molars. Mandibular teeth had a higher incidence (56%) of foramina involving both the pulp chamber floor and furcation surface than did the maxillary teeth (48%).     

江西成年人群下颌骨体副孔解剖位置的锥形束CT研究

目的 应用锥形束CT（CBCT）观测江西成年人群下颌骨体副孔的分布位置,为临床安全操作提供依据。方法 选取200份江西成年人的CBCT资料,按年龄分为4组,每组男女比例相等。描述下颌骨前牙、前磨牙和磨牙各区域的副孔数目和分布位置,分析年龄、性别和左右侧因素与副孔发生率的关系。结果 发现下颌骨体副孔共1 123个,人均（5.62±2.10）个。副孔发生率自近中区域向远中降低,舌侧副孔发生率高于颊侧,男女性副孔数目无差异（P=0.195）,年龄与副孔数目呈负相关（r_s=-0.301）。下颌骨体三处副孔高频区域为:正中联合部（98.0%）,中、侧切牙牙槽突舌侧（88.0%）,前磨牙区的低位（55.0%）。结论 下颌骨副孔每人均会出现,临床需留意避免损伤副孔内容物而引起并发症。     

Tooth support in the human mandible

Prepared surfaces of anterior portions of dentate human mandibles were serially ground in steps of 0.2 mm and the anatomical features traced. The information was stored in a computer and then reassembled and plotted in colour. The percentage porosity of the bone, together with the width of the periodontal space was calculated. The cortical plates of the mandible appear to provide the major boney support for the anterior teeth, trabecular bone only being present in scant amounts in the periapical areas. The apparently random arrangement of trabeculae does not support the commonly accepted picture of trabeculae aligned to resist the functional loads transmitted by the periodontal ligament.     

Assessment of the appearance,location and morphology of mandibular lingual foramina using cone beam computed tomography

Objectives: To investigate the appearance, location and morphology of mandibular lingual foramina (MLF) in the Chinese Han population using cone beam computed tomography (CBCT). Methods: CBCT images of the mandibular body in 200 patients (103 female patients and 97 male patients, age range 10–70 years) were retrospectively analysed to identify MLF. The canal number, location and direction were assessed. Additionally, the diameter of the lingual foramen, the distance between the alveolar crest and the lingual foramen, the distance between the tooth apex and the lingual foramen and the distance from the mandibular border to the lingual foramen were examined to describe the MLF characteristics. Gender and age differences with respect to foramina were also studied. Results: CBCT can be utilized to visualise lingual foramina. In this study, 683 lingual foramina were detected in 200 CBCT scans, with 538 (78.77%) being ≤1 mm in diameter and 145 (21.23%) being >1 mm. In total, 85.07% of MLF are median lingual canals (MLC) and 14.93% are lateral lingual canals (LLC). Two typical types of lingual foramina were identified according to their relationship with the tooth apex. Most lingual foramina (74.08%) were found below the tooth apex, and those above the tooth apex were much smaller in diameter. Male patients had statistically larger lingual foramina. The distance between the lingual foramen and the tooth apex changed with increasing age. Conclusions: Determination of the presence, position and size of lingual foramina is important before performing a surgical procedure. Careful implant-prosthetic treatment planning is particularly important in male and/or elderly patients because of the structural characteristics of their lingual foramina.Key words: Lingual foramen, lingual vascular canal, mandible, cone-beam CT     

Metastases to the human mandible

Two clinical cases are reported of mandibular swelling caused by metastatic jaw neoplasms. They analyse. The clinical characteristics of the swelling are analysed and all laboratory and radiographic tests performed are examined. It is concluded that metastatic localisations in the maxillofacial bone are very rare, but that the mandible is certainly the most frequent site. The authors also highlight the fact that the presence of metastatic lesions in the jaw may be the first symptom of the neoplastic disease.     

Postural control of the human mandible

This article reviews recent experimental evidence explaining the mechanisms that support the mandible in its rest or postural position when the head is stationary and during locomotion. At rest, and during slow jaw movements, there is alternating activation of the jaw-opening and jaw-closing muscles which arises from a central pattern generator. However, this cannot account for the rest position of the mandible even when the head is stationary. Jaw movements and masticatory muscle activity were measured in subjects who stood, walked and ran on a treadmill. Even during walking, there are no bursts of masseter EMG time-locked to heel-landing. However, when subjects ran, the downward movement of the mandible in each step evokes a burst of EMG in the masseters. This is a stretch reflex in the jaw-closing muscles, which acts to limit the downward movement of the mandible relative to the maxilla during locomotion, and to restore the mandibular position towards its rest position. Thus, when the head is stationary, the low-level activity in the jaw-opening and jaw-closing muscles does not contribute to the rest position. Instead, the mandible is supported by passive viscoelastic forces in perioral soft tissues which limit vertical jaw movements even when the head moves gently up and down during walking. When the head moves more vigorously up and down, stretch reflexes in the jaw-closing muscles limit the movement of the mandible. That is, both passive forces and active reflex responses maintain jaw posture within narrow limits during brisk head movements.     

人体下颌骨强度研究

目的：研究取件角度对人体下颌骨皮质骨拉压强度的影响。方法：将人体下颌骨看作是各向异性生物复合材料，采用复合材料力学方法测试其不同方向、不同角度的抗压强度。结果：确定了人体下颌骨皮质骨在应力应为空间的正轴、偏轴强度参数。结论：骨的强度分析不能简单地套用复合材料力学强度理论，而要根据试验结果修理加以应用。