Prevalence and topography of bifid and trifid mandibular canal in Turkish Western Anatolia Population: evaluation of the inferior alveolar canal with CBCT.

PURPOSE: Various anatomical variations of the inferior alveolar canal increase the incidence of surgical complications; Therefore, this study aimed to evaluate the frequency and configuration of bifid and trifid mandibular canals using cone beam computed tomography (CBCT) in the Turkish subpopulation. METHODS: The inferior alveolar canal was evaluated on 1014 hemi-mandibles in the CBCT (I-CAT 3D Imaging System) images of 513 patients. The frequency and configuration of the bifid and trifid mandibular canal (MC) were examined. The relationship between bifid MC configuration and dental status and age groups was analyzed. The distance of the accessory canal to the buccal and lingual walls and the alveolar crest was measured. The diameter of the main canal and accessory canal was measured and its relationship with dental status and age groups was evaluated. RESULTS: Bifid MC was found in 266 hemi-mandibles (24.7%) and 212 (41.3%) of 513 patients. The most common type of bifid MC was the retromolar canal (87 sides), followed by the forward canal without confluence (41; 4%) and the dental canal (34; 3.4%). 10 of the dental canals were opening to the 1st molar, 14 of the 2nd molars, and 10 of the 3rd molars. The number of retromolar foramina was 1 on 56 sides, 2 on 15 sides, and 3 on 4 sides. Forward canal without confluence was more common in edentulous patients than in dentulous patients, while the dental canal was more common in dentulous patients. The main canal diameter was 3.53 ± 0.97 mm and the bifid MC diameter was 1.82 ± 0.70 mm. Distance of the bifid MC to the lingual wall was higher in the > 64 years group than in the 18-39 years group (p = 0.022). Distance of the bifid MC to the alveolar crest was lower in the > 64 years group compared to the 18-39 years group and 40-64 years group (p = 0.015). The main canal diameter was higher in the 40-64 years group than in the 18-39 years group (p = 0.012). CONCLUSION: Bifid MC has a high prevalence, occurring in almost one in two patients. Dental and retromolar types, which are close to the teeth, are more common, and this increases the possibility of complications. CBCT is the most accurate imaging technique used to detect and define these variations.

Unusual array of neural communications in the infratemporal fossa: Useful for skull base surgery.

Variations in the branching pattern of the mandibular nerve frequently accounts for failure to obtain adequate local anesthesia in routine oral and dental procedures, and also for unexpected injury to the nerves during surgery. The knowledge of the neurovascular relationships of the infratemporal region is relevant in odontostomatology practice. In this article we present a rare case of atypical communication between the inferior alveolar nerve and lingual nerve and the mylohyoid and lingual nerves. Further, the clinical implications of these communications on the development of the supplementary innervation and their possible role in anesthesia is discussed in detail. The communication between mylohyoid and lingual nerve was found in this case near the submandibular ganglion after the lingual nerve passes in close relation to third molar tooth, which makes it more susceptible to injury during third molar extractions. The communicating branch between the mylohyoid nerve and lingual nerve may also innervate the tongue, and surgeons should be aware of this variation to avoid post- operative complcations after oral surgeries. Thus the precise anatomy of structures of infratemporal region and its variations may prove beneficial to clinicians, especially to oral and maxillofacial surgeons.

Accessory Mental/Buccal Foramina: Case Report and Review of Literature.

The presence of the additional mental foramen of the mandible is considered to be a rare anatomical occurrence. Only a few cases have been reported. In these cases, only 1 foramen is called the mental foramen and the others are termed either accessory mental foramen or accessory buccal foramen. The purpose of this article was to present a case with computed tomography images and suggest that preoperative cone beam computed tomography should be performed to detect any anatomical variation. In addition, we present all reasonable terminology to ease the communication through unique terminology among surgeons.

Anterior loop of the inferior alveolar nerve: Averages and prevalence based on CT scans.

STATEMENT OF PROBLEM: The treatment of edentulous patients by using a complete implant-supported fixed prosthetic with distal extension has been widely studied; success is mainly dependent upon the placement of the distal implants. The location of the inferior alveolar nerve determines implant placement, but the length, prevalence, and symmetry between the left and right side of the anterior loop of the alveolar nerve are unknown. PURPOSE: The purpose of this clinical study was to measure the anterior loop of the inferior alveolar nerve, which determines the placement of distal implants, in a group of 55 Mexican participants. The study expected to ascertain the average length, prevalence, and symmetry between left and right side and any sex differences. To differentiate the inferior alveolar nerve path, a new technique was applied using Hounsfield unit (HU) thresholds. The null hypothesis was that no significant differences would be found between the left and right sides or between men and women for the anterior loop of the inferior alveolar nerve. MATERIAL AND METHODS: Fifty-five computed tomography (CT) scans were made (Somatom Sensation 16; Siemens Healthcare) and were visualized with InVesalius software. Anterior loop measurements were made on 3-dimensional surfaces. To determine statistical differences between the left and right side and between the sexes, the t test was used. The interclass correlation coefficient test was also applied to verify the reliability of the measurements. RESULTS: Ninety percent of participants showed the anterior loop of the inferior alveolar nerve. The length of the anterior loop ranged between 0 and 6.68 mm, with a mean of 2.19 mm. No significant differences were found between the left and right sides or between men and women. CONCLUSIONS: The mean length for the anterior loop in the sample was 2.19 mm. As the anterior loop length shows a high degree of variability, these findings suggest that a CT scan for each patient is recommended in order to visualize a safety zone before placing implants close to the mental foramen.

Accessory mandibular foramen during dental implant placement: case report and review of literature.

Accurate knowledge of vital anatomical structures, such as the inferior alveolar nerve, mental nerve, and mental foramen, is critical to achieve favorable results during oral surgical procedures and dental implant placement. Although uncommon, variations in mandibular foramina have been reported and if unnoticed and, as a result, injured, may lead to patient morbidity, neurosensory disturbances, and other undesired complications. We present a case report of identification of an accessory mandibular foramen (AMF) encountered during placement of 2 dental implants for a mandibular implant-retained overdenture and demonstrate appropriate management. In addition, we propose a more reasonable terminology for such accessory foramina so as to facilitate communication through common terminology among health care providers. As conventional radiography (periapical and panoramic films) may not allow for proper identification of such anatomical variations, cone-beam computed tomography may be useful in the diagnosis of AMF during treatment planning of dental implants in the mandible.

Variations in the branching pattern of posterior division of mandibular nerve: a case report.

PURPOSE: Abnormal communications among the branches of mandibular nerve especially the posterior division are significant due to various procedures undertaken in this region. These variations are worth reporting as they pose serious implications in several interventions in this region, and may even lead to false diagnosis. METHODS: During routine dissection, the mandibular nerve and its branches were dissected in the infratemporal fossa. The branches from the posterior division of the mandibular nerve namely the inferior alveolar and auriculotemporal nerves were carefully dissected, and their abnormal branching pattern was noted. RESULTS: There was a communicating branch between left inferior alveolar and auriculotemporal nerve. There was also a variant recurrent branch from the left inferior alveolar nerve that supplied the lateral pterygoid muscle. CONCLUSIONS: Such variant branches and communications between the branches of mandibular nerve as seen in this case have an embryological basis and are clinically important in this region especially for dental surgeries and anesthesia.

Bilateral anomalous high position of the mandibular foramen: a case report.

The inferior alveolar nerve block is one of the most common techniques for delivering dental anesthesia. Its success depends on placing the needle tip in close proximity to the mandibular foramen (MF). In certain cases, however, this nerve block fails, even when performed by the most experienced clinician. Anatomical variability may be one source of local anesthetic failure and includes bone and nerve variations. A case is presented of a bilateral anomalous high position of the MF, identified from the panoramic radiograph. An adjusted anesthetic technique (the Vazirani-Akinosi technique) was used to achieve local anesthesia before extraction of a lower second molar following an unsuccessful conventional indirect technique with a higher entry point. A description of the embryological basis for the anomalous high positioned MF and its impact from a practical and clinical perspective, with particular reference to local anatomy, is included.

Accessory lingual mental foramen: A case report of a rare anatomic variation.

INTRODUCTION: The mandibular nerve and the mental foramen have occasionally shown variations in its anatomy. This report aims to present a case of lingual mental foramen recognised on three-dimensional cone beam computed tomographic imaging (CBCT). CASE REPORT: Routine Orthopantomogram (OPG) and CBCT images were evaluated to assess the status of impact third molars in a 31-year-old female who had visited the dental clinics in our institution. The OPG image failed to reveal any anatomic variation in the position of the mental foramen. On tracing the course of the mandibular canal in CBCT images, two foramina were traced at the region of premolar. One opened towards the buccal cortical plate at the normal position of the mental foramen and an accessory lingual mental foramen had an opening on the lingual cortical bone at the same level as the mental foramen. CONCLUSION: Understanding variations of the mental foramen is extremely essential in dentistry to carry out successful anaesthetic or surgical interventions and to avoid complications such as nerve damage or excessive bleeding.

Extramandibular position of the inferior alveolar nerve. Analysis and review of the literature.

We report a highly unusual case of unilateral absence of the mental foramen, with the inferior alveolar nerve exiting the mandible via an orifice situated on the lateral surface of the angle of the mandible. However, the teeth on this side of the dental arch had normal sensitivity, and the mandible had grown correctly. Despite the absence of intraosseous course, the inferior alveolar nerve seems to keep its neural and guide roles.

A case report of developmentally missing mental foramen.

The inferior alveolar nerve is the mandibular division of the trigeminal nerve. Studies have documented variations in the course and branching pattern of the nerve. Here the author reports a case of developmentally missing mental foramen in an individual with normal sensory function. Identification of variations in the nerve pathway is essential for treatment planning in the area.

Dual innervations of mylohyoid muscle: a case report.

Mylohyoid and anterior belly of the digastric muscles are supplied by a branch from the inferior alveolar nerve called the mylohyoid branch. Here we present an unusual finding in a 60-year-old male cadaver in which the mylohyoid muscle is supplied by a branch from hypoglossal nerve in addition to its usual nerve supply. Hypoglossal nerve after giving superior root of the ansa cervicalis and muscular branches to thyrohyoid and geniohyoid muscles gave another branch to supply the mylohyoid muscle. Any variation in the formation and/or branching pattern of ansa cervicalis or hypoglossal nerve can cause confusion and may complicate the procedures involving this nerve such as skull base surgery, neck dissection, and anterior cervical spinal approach. Developmentally mylohyoid muscle is from the mesoderm of the first arch, therefore, must be innervated by the mandibular nerve. Hence, we report this uncommon variation based on embryology and the clinical implications.

Bifurcation of the inferior dental nerve canal: an anatomical study.

The aims of this study were to find the incidence of bifurcation of the inferior dental nerve (IDN) canal, to describe the characteristics of this variant, and to examine the sensitivity and specificity of dental panoramic tomography to identify it. We classified bifurcations by size and position relative to the main canal and the lower third molar using cone-beam computed tomography (CT) and dental panoramic tomography. In our study of 281 patients, 106 (38%) had bifurcations, and in one quarter, these were classified as large accessory canals. Bifurcations were most commonly found posterior to the lower third molar (n=64, 57%) or within 2mm of the roots of the third molar (n=40, 38%). The sensitivity and specificity of dental panoramic tomography to identify all bifurcations was 11% (95% CI: 5.67 to 17.97) and 91% (95% CI: 85.58 to 94.68), respectively; this was 33% (95% CI: 15.63 to 55.32) and 94% (95% CI: 90.34 to 96.50), respectively, for large bifurcations. Our use of cone-beam CT suggested an incidence of bifid canals of 38%, with a variation in size and distribution in relation to the lower third molar. It also showed that the sensitivity of panoramic radiography to identify them was poor.

Anastomosis between the transverse cervical nerve and marginal mandibular nerve: how often does it occur?

Anastomoses in the neck between the sensory transverse cervical nerve (C2,3) and the cervical branch of the facial nerve are common, but communications with more superior branches of the facial nerve are rare. After we had identified a case where the transverse cervical nerve joined the marginal mandibular branch of the facial nerve in the submandibular triangle during a selective neck dissection, we searched for this variant in 86 neck dissections to see if it occurs more often than expected. We found it in one further patient. As this anastomosis of the nerve could easily be confused with the marginal mandibular branch itself, particularly during a more limited exposure (such as excision of a submandibular gland), our findings remind surgeons to be vigilant when dissecting in this area to minimise the risk of weakness of the lower lip postoperatively.

Intraparotid Location of the Great Auricular Nerve: A New Anatomical Basis for Gustatory Sweating Syndrome.

BACKGROUND: Gustatory sweating syndrome (also known as Frey syndrome or auriculotemporal nerve syndrome) is thought to result from a lesion of the auriculotemporal nerve. A lesion of this nerve can lead to aberrant regeneration of nerve fibers to the sweat glands and blood vessels. The occurrence of signs outside the region of the auriculotemporal nerve prompted the author to search for another anatomical basis for this syndrome. METHODS: The author dissected 46 great auricular nerves from their origin to the parotid gland and in the infratemporal fossa. The author investigated the different connections of the great auricular nerve with the facial nerve and the auriculotemporal nerve. RESULTS: The great auricular nerve was found to essentially be a parotid nerve. There was a set of intraparotid nerve connections on 14 of the 46 half-heads that were dissected. The author was able to discern three types of parotid great auricular nerve connections, which he designates as either type 1, connection with the trunk of the facial nerve and its branches; type 2, connection with the auriculotemporal nerve; or type 3, connection with the auriculotemporal nerve and the facial nerve with the formation of an intraparotid nerve circle. CONCLUSIONS: Having clearly established the nerve connections of the great auricular nerve, the author believes that it is primarily this nerve that is responsible for gustatory sweating syndrome. This allows for a better understanding of the sympathetic nervous system features and the manifestation of the syndrome outside the region of the auriculotemporal nerve.

Frequency and anatomy of the retromolar canal - implications for the dental practice.

The retromolar canal (RMC) is an anatomical variant of the mandibular canal. Apart from blood vessels it also contains accessory nerve fibers and is clinically important, because its presence can account for failures of mandibular block anesthesias and in rare cases, injuries of its neurovascular bundle can lead to complications such as hemorrhages and dysesthesias. The aim of this retrospective case study was to analyze the frequency and anatomy of the RMC using cone beam computed tomography (CBCT) in order to draw conclusions for the dental practice. A total of 680 CBCT scans comprising 1,340 mandibular sides were evaluated. A total of 216 RMCs (16.12%) were found. The most common appearance of the canal (39.82%) corresponded to type Al (vertical course), whereas type C (horizontal course) occurred least often (6.02%). Mean measured values were 1.03 mm (SD=0.27mm) regarding the RMC diameter, 10.19 mm (SD=2.64mm) regarding the RMC height and 15.10 mm (SD=2.83 mm) regarding the distance of the RMC to the second molar. Neither demographic factors nor the spatial resolution of the CBCT had a statistically significant impact on the frequency of the RMC. Since the present study revealed a frequency of RMCs amounting to 16.12% (corresponding approximately to every sixth retromolar area), we recommend to spare it during surgery or to consider an additional locoregional anesthesia in the retromolar region. For preoperative diagnosis the CBCT has proved suitable, offering the possibility to select the spatial resolution depending on the indication, so that radiation exposure is reduced without a decrease in validity.

Anatomical study of the course of the inferior alveolar nerve in craniofacial microsomia using three-dimensional computed tomography: correlation with the Pruzansky classification.

Dysmorphogenesis of the mandible complicates assessment of the course of the inferior alveolar nerve in patients with craniofacial microsomia. Our aim in the present study was to correlate the anatomical description of the course with the Pruzansky classification (which indicates the severity of hemifacial microsomia), in the mandibles of 22 affected patients using 3-dimensional computed tomography (CT). We measured the distance between fixed landmarks on the normal and the microsomic sides. The normal sides served as controls. In the group of five patients with type I disease, we found no significant differences between the unaffected and the microsomic side. In the nine patients with Pruzansky type II disease morphological views of the course showed a between-side difference in the length of the bony canal and the height of the mandibular ramus. In the five patients with Pruzansky type III disease, there was no bony canal. Three-dimensional CT analysis may be of value in plotting the course of the inferior alveolar nerve and assisting the surgeon in mandibular osteotomy or distraction osteogenesis.

Accessory branch of the mental nerve.

This case report presents a surgical case in which an accessory branch of the mental nerve exited the mandible distal and slightly superior to the mental foramen. Careful manipulation of the surgical site allowed proper identification of the mental nerve, and the accessory branch and permanent nerve damage was avoided.

Four common mandibular nerve anomalies that lead to local anesthesia failures.

Local anesthesia is essential in treating many dental and oral disorders. However, many types of anatomical anomalies are seen in the nervous system of the mandible that interfere with achieving local anesthesia. The authors describe four such anomalies and offer ways to overcome them when trying to properly anesthetize affected patients.

Accessory innervation of the mandible: identification and anesthesia options.

The nerves commonly associated with accessory innervation of the mandible are identified and alternative techniques to gain their anesthesia are recommended, based on sound anesthetic principles and the current understanding of nerve anatomy.