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The anterior course of the inferior alveolar neurovascular canal was determined in 52 hemimandibles using high-resolution radiographs. Significant variability was found in its course. It was noted that if the osteotomies for sliding genioplasty were performed at least 6 mm below the inferior border of the mental foramen, injury to the mental nerve would be reduced.
The entire course of the mandibular canal is normally not visible on a panoramic radiograph. Locating the course of the mandibular canal at the site of implant placement is important. This study was carried out to determine whether the course of the mandibular canal can be more clearly visualized by tilting the patient's head approximately 5 degrees downward with reference to the Frankfort horizontal reference bar of the Orthopantomogram machine. In 91% of the radiographs taken in this position, the mandibular foramen, mandibular canal, and mental foramen were visible. The angulation of the patient's head reduced the chances of superimposition on the contralateral sides, making these structures clearly visible.
OBJECTIVE: To present normative conduction velocity data for the uninjured human inferior alveolar nerve, and to determine if there are differences in inferior alveolar conduction velocities for either side or for gender. DESIGN: An electrophysiological evaluation of the sensory nerve to the lip and chin was performed. SUBJECTS: Bilateral human inferior alveolar nerve compound action potentials were recorded from each of 46 successive healthy volunteer subjects. INTERVENTIONS: Electrically evoked sensory compound action potentials were recorded from the mandibular foramen by stimulation at the mental foramen. The interelectrode distance was measured from a calibrated radiography. The conduction velocity was calculated at the onset of the waveform and at the maximal amplitude of the waveform. RESULTS: The mean maximal conduction velocity was 65.0 m/s, with no differences shown for right or left sides or for gender. There was a slight decrement in conduction velocity with age. CONCLUSIONS: Conduction velocity testing of the inferior alveolar nerve is feasible and practical. These normative data should serve as a reference for future conduction studies of the inferior alveolar nerve in health, injury, and after repair.
Neural damage leads to a transient or persistent alteration, depending on the severity or type of injury sustained. During the last decade, many investigators reported on paresthesia related to dental implants. In this case report, the patient had presented repeatedly with swelling and suppuration, showing typical signs of peri-implantitis. In addition, the implant was placed in proximity to the mental foramen and possibly had traumatized the mental nerve because the patient had had an altered sensation on his left side for the past 4.5 years. After removal of the implant, a significant diminishing of the paresthesia had occurred, described by the patient as a 40% improvement. Further improvement occurred at 6 and 9 months. In this case report, the findings differ from the current literature in that the return of sensation occurred following a prolonged state of paresthesia. This report documents 2 unique findings. First, an area of persistent paresthesia significantly improved 50 months after the initial injury, upon the removal of the offending implant. Second, the placement of another implant in the same vicinity did not result in recurrent paresthesia.
PURPOSE: To stress the importance of CT depiction of the mandibular incisive canal. This anatomical structure contains a major neurovascular bundle and is thus very important in the planning of mandibular implants in the canine-incisive area. MATERIALS AND METHODS: January through December 1998, sixty patients unselected by age and gender were submitted to mandibular CT. Axial slices were acquired with 1-1.5 mm thickness and 1 mm table feed, and the images were then reformatted with a dedicated dental software. Both the conventional and the Helical techniques were used. RESULTS: The incisive canal appears on Dentascan transverse reconstructions as a round low-density area within mandibular trabecular bone, which is surrounded by a higher-density rim representing the canal walls. This anatomical structure originates from the mental foramen and continues mesially to the mental symphysis. The mandibular canal was visualized in 95% of cases bilaterally (57/60); the incisive canal was depicted on the left side in 41.6% of cases (25/60) and on the right side in 51.6% (31/60). CONCLUSIONS: The importance of careful assessment of the mandibular canal course before implantology is now widely recognized. The same holds true for the canine-incisive region in the jaw, to detect the incisive canal if present and prevent any complications from its accidental damage. CT with a dedicated software showed the incisive canal in a large number of patients, which calls for precise reporting of its presence, course, and relationships with teeth.
The Authors report a technique of a conservative transmandibular approach for the surgical treatment of tonsillar region malignancies. The procedure is based upon the preparation of a vascular mandibular flap through two osteotomies, which are performed, the first above the mandibular foramen and the second below the mental foramen. The main advantages of present technique are: lip-chin-splitting is avoided and, due to the preservation of mandibular vascular and nervous supply, it is possible to accomplish, without risk, postoperative radiotherapy. Moreover, if dictated by oncologic reasons, this conservative procedure may easily be transformed into a radical surgery (commando or neck-jaw operation).
PURPOSE: This article evaluates a new intraoperative recording technique for measuring the sensory nerve conduction velocity (SNCV) of the human inferior alveolar nerve (IAN) during orthognathic surgery of the mandible to assess the effects of intraoperative strain on function of the IAN. MATERIALS AND METHODS: The new test was successfully applied in 10 patients during bilateral sagittal split osteotomy of the mandible (20 IANs). The recordings were made with active wire electrodes at foramen ovale and stimulation was done at the mental foramen with two monopolar needle electrodes. The sensory nerve action potentials (SNAP) were recorded intraoperatively at three stages: 1) before the split, 2) after splitting of the mandible and possible mobilization of the IAN from the proximal bone fragment, and 3) at the end of the operation after fixation of the proximal and distal fragments with screws. RESULTS: The SNCV values (mean 64.1 m/sec) were obtained in all 20 nerves at stage 1, with no significant differences between the sides in latency or amplitude of the SNAPs. The sNAPs remained stable in the IANs not exposed during the operation. In the remaining nerves, the most obvious and statistically significant changes indicating nerve injury occurred between stages and 1 and 2. Partial transsection and mobilization of the IAN were equally potent in bringing about abnormal results in objective neurophysiologic tests as well as subjective sensory disturbances. The results of the intraoperative SNCV recordings correlated well with the findings of the mental nerve blink reflex tests conducted 2 weeks after the operation, whereas comparison of the results of clinical neurosensory testing with the intraoperative events and SNCVs were more inconsistent. CONCLUSIONS: Recording of the SNCV offers a useful objective tool for the examination of the IAN both intraoperatively and in clinical diagnosis.
Correct identification of the causes of dental anesthetic failure is essential in order to adopt the required measures for successful anesthesia. A review is made of the factors implicated in locoregional anesthesia failure, such as a bifid inferior alveolar nerve, retromolar foramen associated to accessory innervation, double or accessory mental foramen, the relation between the infiltration technique and bone density, accessory innervation in the case of the mylohyoid nerve and first cervical branches, cross innervation of the incisors, inactivity in the presence of tissue inflammation, inactive anesthetic solutions, an incorrect technique, and subjective perception on the part of particularly anxious patients. The therapeutic options available in the event such problems are encountered in routine clinical practice are commented.
OBJECTIVE: To evaluate the influence of mandibular distraction osteogenesis on inferior alveolar nerve function. METHODS: 16 young Macaca rhesus monkeys were used as experiment animals. 5 days after mandibular osteotomy under general anesthesia, 10 male monkeys were distracted at right side and 6 females were bilaterally distracted at a rate of 0.5 mm x 2/day, for 15 days. The mandible was lengthened to an average of 13.5 mm. The Sensory Nerve Action Potential (SNAP) test was successfully applied in 16 monkeys before operation and at 0, 2, 4, 6, 9 and 12 weeks after distraction finished. Eight-channel EMG equipment was used for SNAP wave recording. The recordings were made with needle electrodes at foramen ovale and the stimulation was done at the mental foramen with two surface electrodes. The metal ground electrode was fixed on the right forearm. The stimulation intensities were five times of thresholds of each animal. The latency was measured at the first wave peak and the amplitude was measured between two wave peaks. RESULTS: Just after distraction finished, the latency period was 22.18% longer than before operation and gradually shortened as time lapsed. When distraction finished, the amplitude of SNAP wave was only 28.54% of that before operation, and after 12 weeks, it increased to the level of 99.84% of that before operation. CONCLUSIONS: The mandibular distraction osteogenesis has temporary influence on the function of inferior alveolar nerve, but it is little and reversible, along with the regeneration of nerve sheath and axon, the nerve function can gradually return to normal level.
Analysis of 79 adult African mandibles indicated that 64.6% of the mandibular foramina were located below the level of the posterior extension of the occlusal plane while 30.7% were located along this plane. 56.1% of the mental foramina were located below the second premolar while 31.1% were between the second premolar and first molar. The remainder were located between the premolars. The mental foramen opened posterosuperiorly in 72.5% of the surfaces. Multiple mental foramina were found on 4.5% of the mandibles. While emphasising the importance of palpation prior to administration of mental nerve block, these observations suggest that in case of uneffective mandibular nerve block, for a significant proportion of Kenyan Bantus, attempts to place the anaesthetic solution slightly below the occlusal plane be considered.
Craniofacial microsomia (CFM) involves asymmetric hypoplasia and dysmorphogenesis of the facial skeleton. Certain aspects of CFM may be treated by surgical osteotomy and distraction osteogenesis (DO). Mandibular osteotomy places the inferior alveolar nerve at risk. The aim of this study was to investigate radiological landmark relationships to the anatomy of the inferior alveolar nerve in CFM. Application of this understanding will aid intraoperative protection of the inferior alveolar nerve. Six subjects with similar presentations of hemifacial microsomia were selected. Three-dimensional reconstruction CT images was used to locate bony structures that held important relationships with the inferior alveolar nerve. Measurements (of the normal and microsomic sides) were made between fixed landmarks: mandibular notch, mandibular foramen, condyle, back of second and third molar tooth, and mental foramen. The unaffected sides acted as controls. The distance between the normal and the microsomic sides from condyle to mandibular foramen was significantly different. The sizes of condyles differed significantly between the normal and microsomic sides. Most of the remainder of the vertical distance of the ramus and most of the horizontal distance of the body were similar. In conclusion, the inferior alveolar nerve should be found in very similar locations on both normal and microsomic sides in low-grade hemifacial microsomic patients.
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.
A new electrophysiological technique for recording the sensory conduction velocity (SNCV) of the inferior alveolar nerve (IAN) is described. Bilateral orthodromic recordings were done in 21 healthy adults. The sensory responses of the IAN were obtained in all 42 nerves examined with silver wire or monopolar needle electrodes inserted beneath the zygomatic arc in front of the temporomandibular joint to a depth of 4-4.5 cm, near the oval foramen. A small bipolar surface electrode was used for stimulation at the mental foramen. In 3 subjects, the stimuli were additionally delivered via two monopolar needle electrodes to reduce the stimulus artifact. Single responses were usually sufficient for analysis, but, in some cases, averaging was adopted to improve the signal-to-noise ratio. Response latencies and amplitudes, SNCVs, and interside differences were measured, and the 97.5% upper and 2.5% lower prediction limits calculated for reference limits in clinical practice. This new technique provides a sensitive and objective diagnostic tool for the examination of IAN injuries, and may also be used for intraoperative monitoring of the IAN during mandibular surgery.
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.
The feasibility of precise mapping was investigated noninvasively on the face component in predominantly unilateral primary somatosensory cortices (SI) in six healthy subjects. We recorded somatosensory evoked magnetic fields (SEFs) from the SI and secondary somatosensory cortices (SII) following the electrical stimulation of six skin sites: the infraorbital foramen, the angle of mouth, the upper lip, the lower lip, the mental foramen, and the mandibular angle. The median nerve at the wrist was stimulated as a standard of the map. The location of the equivalent current dipoles (ECDs) estimated from the distribution of magnetic fields was identified on MR images of the brain on each subject. The ECDs of the early components of SEF with peaks of 20-30 ms aligned along the SI in the hemisphere contralateral to the stimulation site. Late components with peaks of 80-150 ms were recorded from the bilateral hemispheres, and their ECDs were identified in the SII of the bilateral hemispheres. There was a distinct separation between the ECD locations representing discrete sites on the face and thumb in the SI of the contralateral hemisphere. Five sites of the face area in SI at the contralateral hemisphere were compatible with the conventional arrangement of homunculus in one subject. However, the remaining subjects had variations in the arrangement. The face area reorganization in the SI is possible to be related to the use-dependent cortical plasticity of the individual or to the perceptual experience by vision and proprioception.
BACKGROUND: Human bones decrease in density and increase in porosity beginning at about the third decade of life. The objective of this study was to determine whether mandibular bone mineral density (BMD) and some linear radiomorphometric measurements on dental panoramic radiograph (DPR) are correlated with different categories of body mass index (BMI) in elderly individuals. METHODS: Cortical width at gonion (GI), at antegonion (AI), and below mental foramen (MI) and the appearance of the cortex of the lower border of the mandible distal to the mental foramina due to resorptive changes (mandibular cortical index [MCI]) were measured bilaterally on the mandible on 136 DPRs of elderly individuals. Using DPRs and copper stepwedge, mandibular BMD was investigated densitometrically. All BMD values were expressed in equivalents of the actual stepwedge thickness. The patients with BMIs from 20 to 25 kg/m(2) were classified as category 1 (the generally accepted range of normal BMI), and the patients with BMIs higher than 25 were classified as category 2 (heavy individuals with a heavy skeleton and a large amount of fat in the body). RESULTS: The results revealed statistically significant differences in all measured indices between different BMI categories (p <.05 for MI; p <.001 for GI and AI). Statistically significant differences were also found in BMD values between different BMI categories (p <.05); the differences were more pronounced in women. The patients with MCI category 3 had significantly lower BMD values in comparison to MCI category 2 (p <.01). Intraobserver agreement in GI, AI, MI measurement, and MCI assessments was excellent. CONCLUSIONS: Heavy people have higher BMD and higher values in linear radiomorphometric measurements than lighter people.
The relationship between mandibular bone mass and tooth loss was studied in 269 patients who had neither metabolic disease nor local lesions affecting the mandibular cortex. In all of the subjects, the outline of the mental foramen was distinctly disclosed on unilateral or bilateral panoramic radiographs. Mandibular bone mass was evaluated by determining the mandibular cortical width in the mental region with the use of panoramic radiographs. The relationships of mandibular cortical width to patient age and sex and the number of teeth present were also investigated. In male subjects, there was no significant correlation between the number of teeth present and the mandibular cortical width. Among women in their seventh decade, those with 15 or more teeth showed significantly greater mandibular cortical width than those with fewer teeth. Decrease of mandibular bone mass was positively correlated with tooth loss in female subjects.
This article describes three cases of acute lymphocytic leukemia that presented with mental neuropathy, or so-called "numb chin syndrome," as the initial symptom of the disease. This symptom heralded the initial progression of the disease in the first and second cases and the recurrence of the disease in the third case. In these cases tenderness in the mental foramen, percussion pain of the teeth, loosening and extrusion of the teeth, and radiographic abnormalities were also, if not always, observed in association with mental neuropathy. The radiographic abnormalities included a disappearance of the mandibular canals, an enlarged periodontal ligament space, a loss or thinning of the lamina dura, and a destruction of the alveolar crestal bone. This report indicates that oral manifestations can therefore occasionally play an extremely important role in the early recognition of acute lymphocytic leukemia. The unexplained oral abnormalities such as numbness of the chin and lower lip must thus be considered, potentially ominous indication of acute lymphocytic leukemia.