Assessment of the anterior loop of the inferior alveolar nerve using reformatted computed tomography: a retrospective study

The anterior loop of the inferior alveolar nerve (IAN) is an important landmark in the anterior mandible that must be considered during the placement of dental implants. We measured the length and prevalence of loops of the IAN in 188 consecutive, dentate patients using reformatted computed tomography (CT). A total of 158/188 (84%) had at least one anterior loop; 111/188 (59%) had bilateral loops. The mean (SD) length of the loops in the third quadrant was 1.4 (0.7) mm; 95% CI 1.3 to 1.6; (range 0.3 – 4.0 mm). The mean (SD) length of the loops in the fourth quadrant was 1.5 (0.9) mm; 95% CI 1.4 to 1.6; range 0.3 – 5.5 mm. In total 42/188 (22%) had loops that were longer than 2 mm in quadrants three and four. CT images that have been reformatted with specialised software may be useful to identify loops in the IAN, particularly when recent cone-beam CT images are not freely available. The prevalence of these loops is high while their length varies, which makes meticulous assessment necessary before the placement of implants.     

Anterior loop of the mental nerve in Saudi sample in Riyadh,KSA. A cone beam computerized tomography study

BackgroundThe portion of inferior alveolar nerve (IAN) existent anterior to the mental foramen, before parting the canal, is referred to as the anterior loop (AL) of the IAN. The presence of AL is important when placing the implant interforaminal area of the mandible. These anatomical discrepancies can be assessed by cone-beam CT (CBCT), for evaluating its position and exact location. The AL is classified into Types I, II and III. In Type I, Y-shaped anatomy; in Type II, anatomy is T-shaped; and in Type III, Y-shaped anatomy is seen, and the incisive branch is thicker as compared to the main branch.AimIn this study, we aim to analyse the prevalence of different types of AL of the IAN in Saudi sample population.Materials and MethodsThe present study is a retrospective analysis of 149 (86 female & 63 male) CBCT images of patients records from 2018 June to 2018 September in the department of implant dentistry, KSMC, Riyadh. The age range of the patients who participated in the study was 30–60 years. The mean age of female participants is 42.5 ± 5.8, for the male participants is 48.6 ± 11.4 years respectively.ResultsThe most frequent type of AL of mental nerve noticed on the right side was of type I (59.1%), followed by type II (27.5%) and type III (13.4%). The most frequent type of AL of mental nerve noticed on the left side was type I (61.7%), followed by type II (26.8%) and type III (11.4%).ConclusionThe results of the study encourage the usage of CBCT for planning implant treatment. We also suggest that it is obligatory for professionals to categorise the presence of AL and to measure them appropriately when planning for the procedures in the interforaminal region.     

Anterior maxillary supernumerary teeth: A clinical and radiographic study

Clinical records and radiographs of 90 patients with 113 anterior maxillary supernumerary teeth (mesiodens) have been evaluated. Although uncommon, mesiodentes are the most frequent supernumerary teeth and may disturb the eruption and/or position of the adjacent permanent incisors. Clinical and radiographic examination may disclose the number, direction and location of mesiodentes and their effects on neighbouring teeth. In the present study the majority of the supernumerary teeth lay palatal to the central incisors. Complete or partial eruption of a mesiodens was rare, hence the importance of radiographs to locate supernumerary teeth in the premaxilla. Pathological findings included the formation of dentigerous cysts in three patients and complete ossification of the pericoronal space with resorption of the crown of the mesiodentes in eight cases. Retention and malposition of the adjacent permanent incisors occurred in 39 and 24 cases, respectively.     

Detection and characterization of the accessory mental foramen using cone-beam computed tomography

Objective: This study aimed to investigate the frequency and characteristics of accessory mental foramina (AMFs) and their bony canals in a selected Chinese population using cone-beam computed tomography (CBCT).

Materials and methods: Reconstructed CBCT images of the mandible in 784 Chinese patients (305 males and 479 females) were retrospectively analysed to identify the AMF. The presence, dimension and location of the AMF as well as the origin and course of the associated bony canal were evaluated and classified. Variations in these characteristics were analysed according to gender, side and age.

Results: A total of 66 AMFs were found in 57 (7.3%) of the 784 patients. The frequency of AMFs was significantly influenced by gender and side of the mandible (p?Conclusions: This study presents a considerable frequency of AMFs in a Chinese population. The high-position AMF and the associated bony canal coursing in the oblique upward direction appear frequently. Thus, clinicians should be alert to the presence of the AMF to avoid neurovascular complications especially when dental procedures require periosteum detachment and implant insertion in the mental region.     

Anterior loop of the mental canal: an anatomical-radiologic study

This study sought to characterize the anatomical dimensions of the anterior mental loop and to determine the accuracy of conventional radiographs in identifying its presence and dimensions. The study group consisted of 46 hemimandibles fixed in formalin. Radiographs of the area between the mental foramen and the midline were obtained and evaluated for each hemimandible, followed by dissection and physical examination of the same area. Anatomically, an anterior loop of the mental nerve was observed in only 13 hemimandibles (28%). The anterior extension of the loop ranged from 0.4 to 2.19 mm. No correlation was found between the radiographic image and the anatomical shape of the loop. Of the radiographically diagnosed loops, 40% were not seen in anatomical examination. In cases with a false radiologic loop, a correlation was found between the diameter of the origin of the incisive canal and the radiologic interpretation of the loop. The radiologic appearance or diagnosis of the anterior mental loop in cadaver mandibles does not disclose the true ramification of the inferior alveolar nerve to the mental and incisive nerve.     

Tomographic evaluation of the mandibular nerve in the mental region and its surgical implications: a cross-sectional study

The aim of this study was to evaluate the prevalence and length of the anterior loop (AL) of the inferior alveolar nerve, nerve emergence from the mental foramen, and prevalence of sensory disorders after implant placement in the interforaminal region. Four hundred and fifty hemimandibles (225 patients) were evaluated using cone beam computed tomography and panoramic radiographs. Information on the presence of sensory disorders was obtained from the medical records. AL prevalence was 13.6% and mean AL length was 1.25 mm. The false-negative rate for the identification of the AL using panoramic radiography was 58.6%. Straight nerve emergence from the mental foramen was the most prevalent (62.7%), followed by anterior (21.8%) and posterior (15.6%) emergence. The incidence of sensory disorders was 4.4%, and 1.1% were related to the presence of the AL. When implants were placed within the planned distance of the mental foramen or further, 1.2% had sensory problems associated with the presence of the mandibular incisive canal. In cases of distances smaller than planned, 12.9% had sensory alterations. Only five (1.1%) had the AL, with a length between 0 and 4.5 mm. However, in four cases, the planned distance was respected and, even so, there was a sensory disorder. Posterior nerve emergence from the mental foramen was associated with a higher prevalence of AL.     

Demonstration of the accessory mental foramen using rotational panoramic radiography compared with cone-beam computed tomography

Objective: Rotational panoramic radiography is routinely used in dental practice. It has not been clarified, however, whether an accessory mental foramen can be demonstrated using this technique. The visibility of accessory mental foramina on rotational panoramic radiographs was compared with those on para‐panoramic images reconstructed from cone‐beam computed tomographic (CBCT) images. Materials and methods: A total of 365 patients (130 males and 235 females) were retrospectively analyzed. Para‐panoramic images were reconstructed from CBCT images with the accessory mental foramen/foramina using three‐dimensional visualization and measurement software, and then the accessory mental foramen on rotational panoramic images was compared with that on para‐panoramic images. Results: A total of 37 accessory mental foramina were observed in 28 patients on CBCT images. The rate of being able to visualize the accessory mental foramen or bony canal between the point of bifurcation from the mandibular canal and the accessory mental foramen on rotational panoramic radiographs was 48.6% (18 of 37 accessory mental foramina). Conclusion: Approximately half of the accessory mental foramina‐positive CBCT images demonstrated the accessory mental foramen, or bony canal between the point of bifurcation from the mandibular canal and accessory mental foramen on rotational panoramic radiographs. To cite this article:
Naitoh M, Yoshida K, Nakahara K, Gotoh K, Ariji E. Demonstration of accessory mental foramen using rotational panoramic radiography compared with cone‐beam computed tomography.
Clin. Oral Impl. Res. xx , 2011; 000–000.     

面神经下颌缘支的应用解剖学研究

研究面神经下颌缘支的重要毗邻关系。方法　逐层解剖 6 0侧完整的头颈部标本。观察下颌缘支的支数及分型、与颌外动脉的位置关系、神经走向、与颊支和颏神经吻合情况进行了描述和分析。结果　面神经下颌缘支以 1～ 2支居多。全程分型 ,单干型占 48% ;二干型占 15 % ;合干型占 37%。面神经下颌缘支位于颌外动脉浅面占 86 % ;位于在深面者占 6 % ;下颌缘支环抱或夹持者占 8%。面神经下颌缘支位下颌骨下缘占 44 % ,平下颌骨下缘占 5 1% ;远离下颌骨下缘点 5 %。。结论　面神经下颌缘支的毗邻和行程关系较为复杂 ,了解其与周围的这些重要结构关系 ,可以减少因神经损伤造成下唇及口角功能障碍的发生。     

Evaluation of the course of the marginal mandibular branch of the facial nerve: a fresh cadaveric study

The aim of this study was to determine the course of marginal mandibular nerve (MMN) in relation to the inferior border of the mandible from the gonion until its terminal insertion to the depressor anguli oris, relating the position to a palpable anatomical landmark with emphasis on the depth of the nerve in relation to platysma and the deep cervical fascia. Twelve fresh adult cadavers were dissected and the mandibular base was contoured using needles with 5 mm gaps, starting from the mandibular angle to the muscular termination point of the nerve bilaterally. The distance between the MMN and the mandibular base and total length of the nerve was measured bilaterally. The highest levels of MMN were measured 6.9 mm and 6.5 mm above, and the lowest levels were measured 4 mm and 3 mm below the mandibular base on right and left sides, respectively. The mean (SD) total length of the nerve until the muscular termination point was calculated 33.57 (3.41) mm on the right and 33.51 (4.88) mm on the left side. Previous publications that we had read all fell short of defining the schematic pathway of the nerve, as the described landmarks were of a combination of bone and soft tissue, which are not always clinically reliable. We have overcome this difficulty by standardising the inferior border of the mandible as a point in order to trace the marginal mandibular branch pathway. It originates along the gonion and ends at the second premolar tooth area.     

Inferior alveolar canal course: a radiographic study

Objectives: To describe the morphology and course of the inferior alveolar canal (IAC) as it appears in digital panoramic radiographs.
Materials and methods: Three hundred and eighty-six digital rotational panoramic radiographs (OPG) were studied using the Clinview Software (6.1.3.7 version, Instrumentarium). Among the 386 radiographs, 86 radiographs with 5-mm steel balls were used to calculate the magnification.
Results: The average magnification of radiographs in this study was 7.24±7.55%. The course of IAC as seen in the panoramic radiograph may be classified into four types: (1) linear curve, 12.75%, (2) spoon-shaped curve, 29.25%, (3) elliptic-arc curve, 48.5%, and (4) turning curve, 9.5%. On panoramic radiographs, the IAC appeared closest to the inferior border of the mandible in the region of the first molar. In relation to the teeth, on panoramic radiographs, the IAC appeared closest to the distal root tip of the third molar and furthest from the mesial root tip of the first molar.
Conclusion: In the OPG, there are four types of IAC: linear, spoon shape, elliptic-arc, and turning curve. The data found in the study may be useful for dental implant, mandibule surgery, and dental anesthesia. The limitations of the panoramic radiograph in depicting the true three-dimensional (3D) morphology of the IAC are recognized, computed tomography (CT) and cone beam (CB)3D imaging being more precise.     

Communication between the transverse cervical nerve (C2,3) and marginal mandibular branch of the facial nerve: a cadaveric and clinical study

Several branches of the facial nerve are known to anastomose with branches of the cervical plexus, other cranial nerves, and the trigeminal nerve. Communication between the sensory transverse cervical nerve (C2, 3) and marginal mandibular nerve is, however, less well known, and in a previous study of 86 neck dissections we reported a 2.3% incidence of anastomoses between them. In this prospective study, we meticulously searched for more examples using both formalin-fixed cadavers and neck dissections. A total of 102 necks were included (both sides of 36 cadavers (n = 72 necks), and 30 patients who had neck dissection for the management of squamous cell carcinoma). We found communications between these nerves on one side of a cadaver and in one neck dissection. When combined with the numbers from our previous study, the overall incidence was 2.1% in 188 necks. The marginal mandibular nerve was inseparable from the anastomosis with the transverse cervical nerve, and the variant should not be forgotten if we are to reduce the chance of postoperative weakness of the lower lip, particularly when operative exposure is more limited (such as during removal of the submandibular gland).     

Comparison of facial nerve injury and recovery rates after antegrade and retrograde nerve dissection in parotid surgery for benign disease: prospective study over 4 years

The facial nerve can be dissected using an antegrade or retrograde approach. Antegrade dissection is the established technique and retrograde dissection is used less often. Recent publications have drawn attention to the potential value of the retrograde technique particularly if direct identification of the nerve trunk is difficult, and in revision procedures. We prospectively studied 43 consecutive procedures in 40 patients who had parotidectomy over a 4-year period, and evaluated and compared rates of temporary and permanent nerve injury, and nerve recovery after antegrade and retrograde dissection in operations for benign parotid disease. Each patient was allocated randomly to the antegrade (n = 20) or retrograde (n = 20) groups. Three patients were excluded. All patients had peroperative nerve monitoring and were followed up at 1 week, 1 month, 3 months, or to full recovery of the nerve. The House-Brackmann (HB) grading system was used to assess the degree of injury to the nerve. A high rate of serious nerve injury (HBIII or above) was associated with retrograde dissection at 1 week. Serious nerve injuries (HBIII or above) were slow to recover after the antegrade technique at 3 months. There was no difference between groups in the rates of full nerve recovery at 6 months.     

Degeneration and regeneration of motor and sensory nerves: a stereological study of crush lesions in rat facial and mental nerves

The aim of this study was to evaluate the degeneration and regeneration of a sensory nerve and a motor nerve at the histological level after a crush injury. Twenty-five female Wistar rats had their mental nerve and the buccal branch of their facial nerve compressed unilaterally against a glass rod for 30 s. Specimens of the compressed nerves and the corresponding control nerves were dissected at 3, 7, and 19 days after surgery. Nerve cross-sections were stained with osmium tetroxide and toluidine blue and analysed using two-dimensional stereology. We found differences between the two nerves both in the normal anatomy and in the regenerative pattern. The mental nerve had a larger cross-sectional area including all tissue components. The mental nerve had a larger volume fraction of myelinated axons and a correspondingly smaller volume fraction of endoneurium. No differences were observed in the degenerative pattern; however, at day 19 the buccal branch had regenerated to the normal number of axons, whereas the mental nerve had only regained 50% of the normal number of axons. We conclude that the regenerative process is faster and/or more complete in the facial nerve (motor function) than it is in the mental nerve (somatosensory function).     

Effect of articaine on mental nerve anterior portion: Histological analysis in rats

Abstract

Objectives. The aim of this study was to evaluate the possible toxic effects of articaine and lidocaine on mental nerve, due to the increasing number of paresthesia cases after nerve blocks. Materials and methods. The drugs were injected in the anterior portion of mental nerve of 24 rats, divided into three groups: G1—4% articaine with 1:100,000 epinephrine; G2—2% lidocaine with 1:100,000 epinephrine and G3—plain 1:100,000 epinephrine solution. These solutions were injected in the right side of the rat's mandible and the left side was used as control (0.9% saline solution). Previously to the injections, the animals were anesthetized with thiopental and, 24 h after the injections, their jaws were removed and submitted to routine histological techniques. A histopathological analysis was performed by optical microscopy. Results. An inflammatory infiltration was found around mental nerve, classified as intense for G3, moderate for G1 and light for both G2 and control groups. No injuries were found in nervous structure, despite the inflammatory reaction observed around it. Conclusion. The results suggest that articaine is not toxic to the nervous structure and further studies are necessary to explain the possible relation between articaine injection and paresthesia.     

Piezosurgical management of sealer extrusion‐associated mental nerve anaesthesia: A case report

The present report describes a case where sealer extrusion (Sealapex) occurred during root canal obturation of a left lower second premolar tooth, and the patient experienced sudden pain and followed by complete anaesthesia of the lower lip. After 3 weeks of conservative therapy and an unaltered anaesthesia period, piezosurgical removal of the extruded sealer and root‐end resection was performed despite the direct contact with the mental neurovascular bundle. At suture removal, 1 week after surgery, there was no improvement in sensation. Two weeks after the operation, the patient reported some changes, including a short paraesthesia period alternating with anaesthesia. At the fourth post‐operative week, neurosensory function recovered completely. This case represents successful use of the piezoelectric technique for mental nerve decompression and periapical surgery of a lower second premolar with close contact of the mental nerve.