INTRODUCTION:

Pain relief and the prevention of pain has been one of the main objectives in the practice of medicine, specially surgery and dentistry. Anaesthesia is an induced, temporary state with one or more of the following characteristics: Analgesia (relief from or prevention of pain), Paralysis (extreme muscle relaxation), Amnesia (loss of memory) and Unconsciousness¹. Anaesthesia enables the painless performance of medical/dental procedures that would cure severe or intolerable pain to a patient. The broad category of anaesthesia exists such as General anaesthesia, Sedation and Conduction anaesthesia (regional or local anaesthesia).

Local anaesthesia forms the backbone of pain control techniques in dentistry. One of the most useful techniques to reduce pain from various surgical interventions involving the mandible is inferior alveolar nerve block. Inferior alveolar nerve block anesthetizes the inferior alveolar nerve prior to entering the mandibular foramen¹. It is used to produce anaesthesia of the mandibular teeth, the labial gingiva of the anterior teeth, skin and mucous membrane of the lower lip at the ipsilateral side on which the block is administered. However, during the surgical intervention at the lower premolars and molars, additional buccal nerve anaesthesia is needed².

There are various techniques for blocking the inferior alveolar nerve such as the Gow-Gates technique³, the Vazirani-Akinosi technique or closed mouth mandibular block technique and the conventional technique or direct injection approach⁴ including using a computer-conventional injection system⁵. To perform the inferior alveolar nerve block the tip of the needle must be inserted near the nerve at the mandibular foramen. The needle insertion point is at the mucous membrane on the medial side of the mandibular ramus. The average depth of the needle penetration is two-third of anterio-posterior width of mandibular ramus at the site. The conventional injection approach is the most frequently used and possibly the most important injection technique to block the inferior alveolar nerve, with failure of 15-20% or 7-77%⁶.

In conventional technique, the dentist often uses an alternative technique by withdrawing the needle slightly within the tissue, moving the syringe towards the front of the mouth, over the canine or lateral incisor on the contralateral side and redirecting the needle until the appropriate depth of insertion¹. Here, the patient can see the movement of the syringe in this alternative technique which may intimidate them. Also as the inexperienced surgeon can end up injuring the neurovascular bundle or injecting the solution in posterior pharyngeal space as the depth and direction of needle penetration in conventional approach is not fixed. Whereas, the novel injection approach does not require movement of the syringe while inserting the needle as the syringe is inserted from the ipsilateral side and the depth of needle penetration is fixed (20mm) by stopper⁷.

This study was conducted to compare the anaesthetic efficacy of the novel injection approach as compared to the aesthetic efficacy with the conventional injection approach for inferior alveolar nerve block.

AIM:

To assess the clinical efficacy of the anesthesia obtained with the novel injection approach for inferior alveolar nerve block compared with the conventional injection approach.

OBJECTIVES:

To compare the post-injection pain, the time of onset of anesthesia and the duration of anesthesia after injecting the local anesthesia (2% lidocaine with 1: 80,000 adrenaline).

After the approval of ethical committe, a comparative, randomised, single blind study to compare the efficacy of the novel injection approach with the conventional approach for inferior alveolar nerve block was conducted in 110 patients of the Department of Oral and Maxillofacial Surgery, Ahmedabad Dental College, Gandhinagar, India.

Study Sample:

All the patients signed a written informed consent agreement before they took part in this study. Total 110 patients of the Department of Oral and Maxillofacial Surgery were considered for the study during period of 2014-2016 out of which 10 patients were excluded due to failure of recall and follow up. Routine laboratory investigations were carried out.

Inclusion Criteria:

Physically fit (ASA class I) adult patients of either sex who were indicated for bilateral extractions (surgical/ closed method) of teeth requiring inferior alveolar nerve block.

Highly anxious patients and those patients giving history of allergies to local anesthetic agents and known cardiovascular problems were excluded from study. Also cases with acute infection in orofacial area were not considered.

Materials used:

· 26 gauze, 38mm long needle with rubber stopper at 20mm and Unolock disposable syringe were used.

· A Sharp dental probe was used for evaluation of anesthesia.

Solutions:

· 2% Lidocaine as anaesthetic solution, with 1:100,000 Adrenaline

· Local anesthesia was administered by the standard Inferior Alveolar Nerve block.

Figure 1. Material used.

Procedure:

The patients were not aware of the approach used for inferior alveolar nerve block. Each patient received an inferior alveolar nerve block with the conventional injection approach one side and novel injection approach on contralateral side on next appointment and lower molars were extracted by the same surgeon.

Conventional Injection Approach:

Figure 2. Conventional Injection approach from contralateral side.

The conventional inferior alveola nerve block is described by Malamed. The barrel of the syringe was placed parallel to the mandibular occlusal plane and was directed from premolars on the contralateral side. The injection site was the soft tissue overlying the medial surface of the ramus, lateral to the pterygomandibular raphe, at a height determined by the coronoid notch on the anterior border of the ramus. The point of the injection site was the middle of the palpated finger. The needle was inserted through the mucosa and advanced slowly until gentle contact with the bone. The needle was withdrawn 1mm, the anesthetic solution was slowly deposited after aspiration in the amount of 1.7 ml

Novel Injection Approach:

· A long dental needle (30mm) was used with the rubber stop located 20mm from the tip of the needle. The needle insertion point was same as for the conventional approach (height of injection, anteroposterior sit of injection) but the barrel of the syringe was placed on the occlusal surface of the posterior teeth on the same side of the operation site.

· The major difference in these two approaches was the position and direction of the barrel of the syringe.

Figure 3. Novel injection approach from the same side.

The obvious extent of anesthesia extent of anesthesia of the novel injection approach involves only the inferior alveolar and lingual nerve block like the conventional inferior alveolar nerve block, so buccal nerve anesthesia was still needed for surgical intervention.

Post Injection Pain:

Immediately post-injection, the record data about injection pain was recorded by another dentist using the numeric rating scale

0– 10 Numeric Rating Scale:

Onset of anaesthesia:

· Numbness, was recorded as a subjective sensation of lip paraesthesia, and reported on questioning. Presence of pain was determined by using a sharp dental probe at the gingival sulcus of the lower molar at the operation site 5 minutes after the injection. The patients were asked to indicate when the sharp probe changed the sensation to pain by raising their left hand.

· It was the time required from end of injection to the time point when pain to the application of the sharp probe was abolished and numbness was positive.

Duration of surgery was also recorded to assess if the duration of anesthesia was sufficient for minor oral procedures.

Duration of anaesthesia:

Duration of anaesthesia was measured from the time subjective symptom (numbness) was positive till the pain in the surgical area was felt. Which was confirmed by phone call or next day follow up.

OBSERVATION AND RESULTS:

100 patients, who required bilateral extraction of lower premolar amd molar teeth were included in this study. All cases were done in Department of Oral and Maxillofacial Surgery, Ahmedabad Dental College and Hospital.

All the patient received inferior alveolar nerve block via both novel injection approach (Group I) and conventional injection approach (Group II). In both groups 1.5 to 1.8 ml of anesthetic solution was injected for inferior alveolar nerve block and 0.3 to 0.5 ml anesthetic solution for long buccal nerve block. Following anesthetic injection, post injection, onset, depth and duration of anesthesia for both the injection technique were noted. Post injection pain was recorded using the Visual Analog Scale and pain score for both the techniques were noted. All the patients were provided with analgesic medication and instructed to take medication only when they felt pain in the surgical area. Time for requirement of analgesic was confirmed by phone call or noted by patient and reported on the next appointment.

All the observation were noted and tabulated in the master chart.

1. The post injection pain:

The mean post injection pain for Group I is 1.72 (SD 1.48) and 4.68 (SD 1.88) for Group II. The difference is highly statically significant (p<0.001). (Table I, Graph I)

2. Time of onset of anaesthesia:

The mean anaesthetic latency for Group I was 2.76 (SD 0.55) minutes versus 2.04 (SD 0.24) for Group II. Statically highly significant differences being observed between the two injection techniques. (p<0.001) (Table II, Graph II)

3. Duration of procedure:

The mean value for Group I was 11.47 (SD 11.25) minutes and 11.22 (SD 9.81) for Group II. The difference in this case is statically in significant. (p<0.86) (Table III, Graph III)

4. Duration of anaesthesia:

In turn, the mean duration of anaesthetic effect was 4.57 (SD 0.56) hours for Group I and 5.03 (SD 0.65) hours for Group II the difference in this case being highly statically significant. (p<0.001) (Table IV, Graph IV)

TABLES

Table I: Post injection pain(Numeric Rating Scale):

Pain Score (Numeric Rating Scale)		p value
Group I	Group II	p value
1.72	4.68	<0.001 Highly significant statistically

Table II: Onset of anesthesia (minutes):

Onset of anesthesia (minutes)

p value

Group I

Group II

2.76

2.04

<0.001

Highly significant statistically

Table III: Duration of procedure (minutes):

Duration of procedure (minutes)

p value

Group I

Group II

11.47

11.25

<0.869

Statistically not significant

Table IV: Duration of anaesthasia (hours):

Duration of anesthesia (hours)

p val.ue

Group I

Group II

4.57

5.03

<0.001

Highly significant statistically

GRAPHS:

Graph I: Post Injection Pain (Numeric Rating Scale):

Graph II: Onset of anesthesia (minutes):

Graph III: Duration of procedure (minutes):

Graph VI: Duration of anesthesia (hours):

CONCLUSION:

In conclusion, the novel injection approach has a number of advantages over the conventional injection approach, such as: avoiding pain from the tip of the needle traumatizing the periosteum and bone in the conventional approach; avoiding or decreasing complications such as soft tissue and neurovascular bundle trauma; and positive aspiration followed by intravascular injection by decreasing the reinsertion of the needle from the wrong direction, which results in decreasing the opportunity of trauma to the neurovascular bundle. This novel injection approach is also a simple and safe technique for inferior alveolar nerve block with a duration suitable for surgical intervention of the lower third molar.

REFERENCES:

1. Malamed SF. Handbook of local anaesthesia. 5th ed. St. Louis: Mosby; 2004. pp. 294–6.

2. Yang H M, Won S Y, Lee J G, Han S H, Kim H J, Hu K S. Sihler-stain study of buccal nerve distribution and its clinical implications. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, March 2012;113:334-9.

3. Montagnese T A, Reader Al, Melfi R. A comparative study of the Gow-Gates technique and a Standard technique for mandibular anaesthesia. April 1984;10(4):158-63.

4. Aggarwal V, Singla M, Kabi D. Comparative evaluation of anesthetic efficacy of Gow- Gates mandibular conduction anesthesia, Vazirani-Akinosi technique, buccal-plus-lingual infiltrations, and conventional inferior alveolar nerve anesthesia in patients with irreversible pulpitis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010, 109:303–8.

5. Ozer S, Yaltirik M, Kirli I, Yargic I. A comparative evaluation of pain and anxiety levels in 2 different anaesthesia techniques: locoregional anaesthesia using conventional syringe versus intraosseous anaesthesia using a computer- controlled system. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, November 2012;114(5S):S132-9.

6. Takasugi Y, Furuya H, Moriya K, Okamoto Y. Clinical Evaluation of Inferior Alveolar Nerve Block by Injection Into the Pterygomandibular Space Anterior to the Mandibular Foramen, Anesth Prog; December 2000;47:125-9.

7. Boonsiriseth K, Sirintawat N, Arunakul K, Wongsirichat N. Comparative study of the novel and conventional injection approach for inferior alveolar nerve block. Int. J. Oral Maxillofac. Surg. 2013; 42: 852–6.

Received on 28.02.2019 Modified on 15.03.2019

Res. J. Pharmacology and Pharmacodynamics.2019; 11(3):101-105.

DOI: 10.5958/2321-5836.2019.00018.1