Clinical Evaluation of Inferior Alveolar Nerve Block: DISCUSSION

In: Main

12 Feb 2010

Pterygomandibular space

Local anesthesia should produce a desirable anesthetic effect without unnecessary injury. The inferior alveolar nerve, vein, and artery are found near the mandibular foramen, and the pterygoid plexus is located posteriorly and superiorly. Therefore, the conventional technique, which aims the needle toward the mandibular foramen, is accompanied by risks for complications such as vascular or neural injury, intravascular injection, and muscular injury. An incidence of blood aspiration of 2.9 to 22% has been reported for the conventional technique. Although the reported incidence of permanent neuroparalysis in patients receiving the conventional technique is not frequent, 3:2573 administrations by Saitoh et al or between 1:26,762 and 1: 160,571 by Pogrel et al, the electric shock sensation that often accompanies nerve involvement has been reported as 3, 7, and 8%. Furthermore, muscle trismus has been reported as a significantly frequent side effect of the conventional technique because of penetration of the needle into the medial pterygoid and temporal muscle.

Our anatomical study of the pterygomandibular space using the CT images confirmed a space between the medial pterygoid muscle and the deep tendon of the temporal muscle near the anterior border of the mandibular ramus. We hypothesized that a local anesthetic solution injected into the pterygomandibular space should diffuse and reach the inferior alveolar nerve, even if the injection site is distant from the mandibular foramen. In the anterior technique, the needle tip should be placed into the gap between the medial pterygoid muscle and the deep tendon of the temporal muscle in the pterygomandibular space anterior to the mandibular foramen to prevent injury to the inferior alveolar nerve or vessels. The measured predicted insertion angle in the anterior technique was approximately 60° with the direction from over the contralateral mandibular first molar, and an insertion depth of 1 cm is desirable to penetrate the submucosal layer that contains the buccal fat pad, which is of variable thickness. These insertion angles and depths are presumed to diminish the risk of injury to the lingual nerve or the medial pterygoid muscle. canada viagra online

The reported success rates of the conventional technique vary from approximately 55 to 95% and the success rate of the anterior technique in our study was evaluated to be more than 75% in both postural groups. In the conventional technique, Sisk reported that the mean onset time was 5.08 minutes and Petersen reported that the mean time lapse between the injection and the start of surgery was 23 minutes. In our study, the median onset time of complete numbness of lower lip and the median time lapse between the injection and the start of surgery in the anterior technique were 4 minutes and 9 minutes, respectively. Our results suggest that the effectiveness of the anterior technique is not lower than that of the conventional technique and that the postural difference did not influence the anesthetic effect in the anterior technique.

In conclusion, the anterior technique is able to achieve anesthesia of the inferior alveolar nerve with low risk of inferior alveolar neural and vascular complications. It should be considered as an alternative to the conventional technique. kamagra tablets

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