Variant Inferior Alveolar Nerves and Implications for Local Anesthesia.

A sound knowledge of anatomical variations that could be encountered during surgical procedures is helpful in avoiding surgical complications. The current article details anomalous morphology of inferior alveolar nerves encountered during routine dissection of the craniofacial region in the Gross Anatomy laboratory. We also report variations of the lingual nerves, associated with the inferior alveolar nerves. The variations were documented and a thorough review of literature was carried out. We focus on the variations themselves, and the clinical implications that these variations present. Thorough understanding of variant anatomy of the lingual and inferior alveolar nerves may determine the success of procedural anesthesia, the etiology of pathologic processes, and the avoidance of surgical misadventure.

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.

Evaluation of mandibular anatomy related to sagittal split ramus osteotomy using 3-dimensional computed tomography scan images.

Sagittal split ramus osteotomy (SSRO) of the mandible is one of the most common surgical techniques to correct mandibular deformities. Measurement of nerve position using conventional methods has been reported in the literature, but surgeons have found that further investigation of the anatomical relationship is needed. The aim of this study was to attempt to increase the accuracy of treatment by using 3-dimensional computed tomography scan measurements. From the normal population, 20 females and 20 males were enrolled during planning of denture implants in Taiwan. The mean age was 28+/-6, ranging from 20 to 39 years old. Using 3D tomography data, nerve position at osteotomy sites was measured and the geometric relationship examined between the antilingula and mandibular foramen. The results gave the mean distance from buccal plate to mandibular canal at the second molar, from mandibular canal to inferior border of the mandibular body, from the mandibular foramen to the highest tip of the lingula, and from the mandibular foramen to the anterior margin of the oblique ridge. When applied to SSRO operations, the anatomic data provided by this study may help surgeons gain more understanding of nerve position during surgery.

Multivariate assessment of site of lingual nerve.

Injury to the lingual nerve can cause debilitating symptoms. The nerve lies in the retromolar region and its anatomical site can vary within patients and according to sex, age, and dentate status. To our knowledge, no previous studies have recorded its course from multiple bony landmarks and examined the association between age, dentate status, and sex, in the same sample. We dissected 30 white cadavers and took primary and secondary reference points from the internal oblique ridge. We measured the distance to the lingual nerve in sagittal, vertical, and horizontal planes, and recorded the position where the nerve was closest to the lingual plate. We dissected 46 hemimandibles (23 male, mean age 79 years, range 52-100) of which 26 were from the left side. Mean (SD) sagittal, vertical, and horizontal distances from the primary reference point were 9.29 (3.41)mm, 9.15 (3.87)mm, and 0.57 (0.56)mm, respectively. Mean (SD) vertical and horizontal distances from the secondary point were 7.79 (5.45) mm and 0.59 (0.64)mm, respectively. The proximity of the nerve to the lingual plate varied widely (range -13.00 to 15.17mm from the primary reference point). Dentate status was significant for the sagittal measurement from the primary point, and the vertical measurement from the secondary point. Differences in age, sex, or site of the contralateral nerve were not significant (n=16 pairs). Our findings suggest that the site of the nerve is consistent between and within subjects for sex and age, but not for dentate status. The association between the nerve and the lingual plate varied, which suggests that care must be taken when operating in the area.

Implant-related nerve injuries.

Injuries to branches of the trigeminal nerves are a known complication during dental implant placement. These injuries tend to be more severe than those experienced during other dentoalveolar procedures. This article reviews the types of nerve injuries and areas and situations of which clinicians should be cognizant when placing dental implants. Strategies to avoid injuries, and a management algorithm for suspected nerve injuries, are also discussed.

Insights into maxillary and mandibular growth for a better practice.

By understanding the growth mechanisms of the maxilla and mandible and using four key concepts of Neuro-Occlusal Rehabilitation, better treatment can be rendered to the patients with malocclusions and chewing disturbances. This paper relates these concepts with experimental data.

Morphometrical and morphological study of mental foramen in dry dentulous mandibles of South Andhra population of India.

BACKGROUND: Mental foramen (MF) is an anatomical structure of particular importance in local anesthesia and surgical procedures in terms of achieving effective mandibular nerve blocks and avoiding injuries to the neurovascular bundles. AIM: To determine the morphometry and morphology of MF in south Andhra population of India, hitherto unreported. MATERIALS AND METHODS: Ninety dry dentulous mandibles of both sexes were examined for position, size, shape and number of MF. RESULTS: Various parameters investigated are, the horizontal distance between (1) symphysis menti and MF was 27.2 mm on right and 27.7 mm on the left, (2) MF and posterior border of ramus was 70.7 mm on both sides, vertical distance between (3) MF and inferior border of mandible was 16.5 mm on right and 14.3 mm on left, (4) alveolar crest and MF was 13.7 mm on right and 16.4 on left, (5) distance between the MF and below the apex of premolar socket was +2.8 mm on right and +3.5 mm on left and above the socket was -2.8 mm on right and -2.7 mm on left. Occurrence of MF below the second premolar tooth was found to be highest (73.2%). Average size of MF was larger on left and its way of exit was in postero-superior direction. Shape of MF was round in 79% and oval in 21% and double MF was found in 8.9% of mandibles. CONCLUSIONS: In the present study, most common position of MF was found below the apex of second premolar in 73.2% and between the second premolar and first molar in 19% of mandibles. The other morphometrical findings of this study may be implicated by dental practitioners and maxillofacial surgeons.

The accuracy of identifying the greater palatine neurovascular bundle: a cadaver study.

BACKGROUND: The palate is a common site for harvesting subepithelial connective tissue grafts (SCTG). The size of SCTG that can be harvested is dictated by the position of the greater palatine neurovascular bundle (GPB). The aims of this cadaver study are to assess the accuracy of predicting the location of the GPB on study models and to evaluate anatomic factors that might influence the predictability. METHODS: Eleven fully dentate or partially edentulous maxillary cadavers were used. Study models were fabricated after the greater palatine foramen was identified. The GPB was recognized after dissection, from which the distance to the cemento-enamel junction of the first molar and premolar was measured. Eight periodontists and twelve periodontal residents were asked to estimate the location of the GPB on the study models and the same measurements were taken. Comparisons of the estimated and true GPB position were performed. The correlation between the palatal vault height and the variability of detecting the GPB was investigated. RESULTS: The most frequent greater palatine foramen location was between the second and third molars (66.6%). For most cases, there was an underestimation of the location of the GPB up to 4 mm. The interexaminer variability was positively correlated with the vault height. CONCLUSIONS: The estimated location of the GPB was commonly closer to the cemento-enamel junction of posterior teeth. Agreement on the location of the GPB was lowered with the presence of high palatal vaults. The results of this study could assist clinicians in planning the location for harvesting SCTG on the hard palate.

Correlation of mandibular bone quality with neurosensory disturbance after sagittal split ramus osteotomy.

Our aim was to find out whether the quality of bone around the inferior alveolar nerve is correlated with neurosensory disturbance to the nerve after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. Computed tomograms (CT) were taken of 35 patients with mandibular prognathism and 35 without. To assess the density of bone around the inferior alveolar nerve, the width of the buccal cortical bone in the mandibular second molar regions was measured on CT. The Hounsfield units (HU) in the same regions were also measured. The number of HU in the mandible around the second molar regions was significantly higher (p<0.01) in those with neurosensory disturbance (p<0.01). The quality of bone measured by HU is associated with an increased risk of neurosensory disturbance, but the width of buccal bone is not.

Area extent anaesthesia from buccal nerve block.

This study investigated the extent of complete anaesthesia from buccal nerve block. 40 healthy Thai patients (20 males; 20 females) requiring buccal nerve block for surgery were studied. After the buccal nerve was blocked, the buccal mucosa was explored using a sharp probe to map out the extent of anaesthesia. The operation was carried out after inferior alveolar and lingual nerve block. The extent of the anaesthesia was mainly from the retromolar area to the second molar, followed by the first molar to the second premolar, whilst the first premolar to the central incisor was the area least affected. An important finding of this study was that the anaesthetized extent of some patients extended to the anterior region on the same quadrant. This study showed the affected areas of buccal nerve anaesthesia extended through the buccal mucosa from the first premolar to the central incisor in some patients. It can serve as another informative indication for lower anterior surgery.

Anterior middle superior alveolar injection is effective in providing anesthesia extending to the last standing molar in maxillary periodontal surgery.

BACKGROUND: Multiple injections are required to anesthetize the maxilla for periodontal surgery that involves a quadrant or multiple teeth across the midline. The anterior middle superior alveolar (AMSA) field block was reported to effectively anesthetize the central incisors to the mesial aspect of the first molar of the maxilla with one or two injections. To our knowledge, the extent of anesthesia has not been reported beyond first molars in the literature. METHODS: Fifty subjects who were indicated for periodontal surgery were provided maxillary anesthesia with an AMSA injection through a conventional syringe with a 27-gauge needle. All subjects were given an AMSA injection, and after surgery, they were assigned to group 1 (requiring only the AMSA injection), group 2 (requiring one supplemental buccal infiltration), or group 3 (requiring two supplemental buccal infiltrations). Subjective and objective signs and symptoms were used to confirm the extent and profoundness of the anesthesia at 90, 120, and 180 minutes. RESULTS: Statistical significance for groups 1 and 2 was observed for anesthesia at different time intervals during the course of periodontal surgery. Pairwise comparisons of groups showed no statistical significance. The profoundness of the anesthesia extended to the last standing molar. CONCLUSIONS: The AMSA injection provided excellent, wide-spread anesthesia in all groups for the required time of surgery, and there was no significant implication among groups. The AMSA injection can be used as an effective technique to anesthetize teeth distal to the first molar up to the last standing molar in maxillary periodontal surgery.