Topographic anatomy of the mandibular nerve branches distributed on the two heads of the lateral pterygoid

Inferior Alveolar Nerve Block Using the Anterior Technique to Anesthetize Buccal Nerve and Improve Anesthesia Success Rates for Third Molar Extraction: A Randomized Controlled Trial and Magnetic Resonance Imaging Evaluation

PURPOSE

The lack of anesthesia to the buccal nerve and an insufficient volume of anesthetic have been reported to be responsible for failed inferior alveolar nerve blocks (IANBs) using the Halsted approach (conventional IANB). We aimed to determine the extent of anesthesia in the buccal nerve innervation area and evaluate the anesthetic efficacy of injecting a larger volume of anesthetic during IANB using the anterior approach (anterior technique) in the clinical setting and with magnetic resonance imaging (MRI) analysis.

PATIENTS AND METHODS

The prospective randomized controlled trial included patients scheduled for removal of a mandibular third molar. The primary predictor variables were the approach for IANB (anterior technique vs conventional IANB) and anesthetic dose (1.8 vs 2.7 mL). The primary outcome variables were the extent of anesthesia and the anesthesia success rate, defined as completion without additional anesthesia. The secondary outcome variable was the anesthetic drug distribution related to the pterygomandibular space measured on T2-weighted MRI scans. Statistical independence of the anesthesia success rate among the primary predictor variables was tested with statistical significance set at P ≤ .05.

RESULTS

A total of 108 patients and 10 volunteers were enrolled in the clinical and MRI studies, respectively. Anesthesia of the buccal nerve was evident in patients receiving the anterior technique with 2.7 mL of anesthetic. The success rate of the anterior technique with 2.7 mL of anesthetic (96%) was greater than that with 1.8 mL of anesthetic (67%; P = .0113), and increasing the dose had no effect on the efficacy of conventional IANB (78% vs 81%; P = 1.000). The MRI study showed that the anesthetic was distributed over the anterior surface of the temporalis tendon and in the pterygomandibular space after the anterior technique.

CONCLUSIONS

Anesthesia of the buccal nerve using the anterior technique with 2.7 mL of anesthetic solution might contribute to increasing the success rate of anesthesia for removal of mandibular third molars.

Sensory disturbances of buccal and lingual nerve by muscle compression: A case report and review of the literature

Introduction

Several studies on cadavers dissection have shown that collateral branches of the trigeminal nerve cross muscle bundles on their way, being a possible etiological factor of some nerve disturbances.

Case Report

A 45-year-old man attended to the Temporomandibular Joint and Orofacial Pain Unit of the Master of Oral Surgery and Implantology in Hospital Odontològic of Barcelona University, referring tingling in the left hemifacial región and ipsilateral lingual side for one year, with discomfort when shaving or skin compression.

Discussion

Several branches of the trigeminal nerve follow a path through the masticatory muscles, being the lingual nerve and buccal nerve the most involved. The hyperactivity of the muscle bundles that are crossed by nerve structures generates a compression that could explain certain orofacial neuropathies (numbness and / or pain) in which a clear etiologic factor can not be identified.

Key words:Buccal nerve, paresthesia, idiopathic trigeminal sensory neuropathy.

The evaluation of lateral pterygoid muscle pathologic changes and insertion patterns in temporomandibular joints with or without disc displacement using magnetic resonance imaging

Temporomandibular joint (TMJ) disc displacement is a common disorder in patients with internal derangement. Certain anatomic features of TMJ may make the patient prone to this condition, namely lateral pterygoid muscle (LPM) insertion variations. The aim of this study was to investigate LPM attachments and their relationships with disc displacement and subsequent pathologic changes. A total of 26 patients with clinical temporomandibular disorders (TMDs) and a control group of 14 unaffected individuals were studied. Magnetic resonance images (MRIs) were taken to evaluate LPM insertion patterns, superior LPM head pathologic changes, and relative disc to condyle position. Data registration and analysis were done using SPSS v. 16.0. The most common variation (type I) was shown to be the superior head with two bundles, one attached to the disc and another to the condyle. No significant relationship between LPM insertion type and disc displacement or pathologic changes of the muscle was found. However, a link between disc displacement and muscle pathologic changes was established (P=0.001).

The lateral pterygoid muscle, a heterogeneous unit implicated in temporomandibular disorder: a literature review

Based on its anatomical relationships, the lateral pterygoid muscle is strongly linked with the temporomandibular joint (TMJ). It plays a major role in mastication. Embryological, histological, and anatomical knowledge define the lateral pterygoid muscle as a single muscle with a penniform structure. The various results of electromyographic (EMG) studies describe a complex physiology with a chronological contraction of the layers during the masticatory cycle. The sequential contraction of the layers of the lateral pterygoid muscle is the result of a selective neuronal activation induced by the masticatory Central Pattern Generator (mCPG). This neurophysiological theory highlights the essential role of the reticular formation in oral motor control. The sensitivity of those neurological structures to chronic emotional stress is one of the possible explanations for the appearance of oral parafunctions accompanied by a modification of pain perception and a disorganized muscular activation, determining factors in temporomandibular disorders.

A new method for lateral pterygoid electromyographic electrode placement

STATEMENT OF PROBLEM

Making electromyographic recordings of the lateral pterygoid muscle (LP) is difficult because of potential electrode damage to, for example, the maxillary artery and long buccal nerve, and because of pain and reduced jaw mobility characteristic of many orofacial pain patients.

PURPOSE

The purpose of this study was to develop a reliable intraoral placement technique for the inferior head of the lateral pterygoid (IHLP) that minimizes jaw displacement.

MATERIAL AND METHODS

In 2 dried skulls and 7 human cadavers, it was estimated that, with the mandible in an ipsilateral closed position, a straight needle could be used to position fine-wire electrodes into the midportion of IHLP by inserting the needle through the mucosa adjacent to the distal root of the maxillary second molar, towards the external auditory meatus and parallel to the buccal alveolar bone of the maxilla. The needle avoided the maxillary artery and long buccal nerve. Using this approach in 5 adults, 2 fine-wire electrodes were placed into the IHLP. Placement was verified by computer tomography (CT) and electromyography.

RESULTS

In all subjects, the ideal insertion depth to place the electrodes in the middle of IHLP was 29 mm.

CONCLUSIONS

This technique is a reliable method for IHLP electrode placement for patients with impaired jaw function, minimizing risk of damage to major structures.

A possible etiology of the internal derangement of the temporomandibular joint based on the MRI observations of the lateral pterygoid muscle

The purpose of this study was to evaluate the relationship of the temporomandibular joint (TMJ) internal derangement and lateral pterygoid muscle (LPM) by magnetic resonance imaging (MRI). In this study, 115 subjects with TMJ internal derangement (total 230 TMJs) and 21 subjects without clinical symptoms (total 42 TMJs) were included. TMJ disc position and LPM were evaluated using MRI. LPM attachments were categorized into two different types: type 1, where fibers of the superior head of the LPM (SLPM) were attached to the disc and fibers of the inferior head of the LPM (ILPM) were attached to condyle, and type 2, where fibers of the SLPM were attached to the disc and condyle, and fibers of the ILPM were attached to condyle. The presence of muscle atrophy and degeneration were also evaluated. LPM attachments were observed in two different parts. Disc displacements were common in the muscle attachments of both types. Type 1 muscle attachments were seen in 85.9% of all the anterior disc displacement without reduction (ADD) TMJs (total 64 TMJs). Atrophy was seen in a higher proportion (43.7%) in TMJs with ADD (28/64) than in TMJs with normal and anterior disc displacement with reduction (ADDR). Out of 74 TMJs with atrophy, 68 had type 1 muscle attachment. Four TMJs had atrophy in both superior and inferior heads of the lateral pterygoid. However, atrophy was not present only in the ILPM. It has been concluded that since the SLPM only attached to the disc in type 1, the disc may displace anteriorly very easily. Therefore, this situation will reduce the function of the SLPM. Reduced muscle function may cause muscle atrophy. The activity of the SLPM may be more reduced since the disc permanently dislocated in TMJs with ADD. Finally, spasm of the LPM causes disc displacement and atrophy and then the degeneration of the LPM may follow disc displacement.