|Year : 2012 | Volume
| Issue : 1 | Page : 53-57
Inferior alveolar nerve block: Alternative technique
K Thangavelu, R Kannan, N Senthil Kumar
Department of Oral and Maxillofacial Surgery, Vinayaka Mission's Sankarachariyar Dental College, Ariyanoor, Salem, Tamil Nadu, India
|Date of Web Publication||14-Nov-2012|
Vairam Hospital, EB Colony, Namakkal, Tamilnadu
| Abstract|| |
Background: Inferior alveolar nerve block (IANB) is a technique of dental anesthesia, used to produce anesthesia of the mandibular teeth, gingivae of the mandible and lower lip. The conventional IANB is the most commonly used the nerve block technique for achieving local anesthesia for mandibular surgical procedures. In certain cases, however, this nerve block fails, even when performed by the most experienced clinician. Therefore, it would be advantageous to find an alternative simple technique.
Aim and Objective: The objective of this study is to find an alternative inferior alveolar nerve block that has a higher success rate than other routine techniques. To this purpose, a simple painless inferior alveolar nerve block was designed to anesthetize the inferior alveolar nerve.
Materials and Methods: This study was conducted in Oral surgery department of Vinayaka Mission's dental college Salem from May 2009 to May 2011. Five hundred patients between the age of 20 years and 65 years who required extraction of teeth in mandible were included in the study. Out of 500 patients 270 were males and 230 were females. The effectiveness of the IANB was evaluated by using a sharp dental explorer in the regions innervated by the inferior alveolar, lingual, and buccal nerves after 3, 5, and 7 min, respectively.
Conclusion: This study concludes that inferior alveolar nerve block is an appropriate alternative nerve block to anesthetize inferior alveolar nerve due to its several advantages.
Keywords: Aanesthesia, inferior alveolar nerve block, mandible
|How to cite this article:|
Thangavelu K, Kannan R, Kumar N S. Inferior alveolar nerve block: Alternative technique. Anesth Essays Res 2012;6:53-7
| Introduction|| |
Inferior alveolar nerve block (IANB) is a technique used to produce anesthesia of the mandibular teeth, gingiva of the mandible, and the lower lip. These procedures anaesthetize the inferior alveolar nerve (IAN) prior to entering the mandibular foramen. Although IANB is a routine block injection administered regularly in dental practice, failure to achieve satisfactory levels of analgesia is noticed in few cases. , Predictable anesthesia is an essential requirement for both the patient and the dentist in Dentistry. The patient's opinion about his dental treatment is closely related to the local anesthesia experiences he has had. The proper use of local anesthesia techniques and pain management are indispensable for successful dental treatment.  IANB is the most commonly used nerve block technique in extraction of lower teeth and other minor surgeries done in mandible. Various techniques are in current use to anesthetize the IAN. Each technique has its advantages and disadvantages. So the aim of this study is to find an alternative IANB that has the minimal failure rate and with less technical difficulty.
| Aim and Objective|| |
The aim of this study is to present an alternative to the current techniques available to anesthetize the IAN. To this purpose, a simple painless IANB was designed to anesthetize the IAN. The objective of this study is to find an IANB that has higher success rate than other routine techniques.
| Materials and Methods|| |
This study was conducted in Vinayaka Mission's Dental College who came for extraction of Lower molars, premolars and anterior teeth over a period of 2 years from May 2009 to May 2011 based on the experience gained from 500 patients. Out of 500 patients, 270 male and 230 female, age 20 to 60 years, scheduled for lower third molars, premolars, canines, and incisors extractions and who have given their informed consent to participate. The patients those who were normally healthy patients, ASA I, who were not taking any medication and have never had allergic or toxic reactions to any local anesthetic agent and they were randomly selected. All the injections were given by authors of this article. Disposable 3 mL syringe with 32 mm length and 25 gauge needles were used for this technique. Lignocaine hydro chloride with adrenalin 1 in 80 000 was the anesthetic solution used in all 500 nerve blocks. For each technique 2.5 mL anesthetic solution was taken. The time required to develop anesthesia was 3 to 7 min.
- Patient is advised to sit in semi supine position and few inches below the operator's elbow level in the dental chair.
- The patient is advised to open the mouth fully so that the occlusal table of mandible is parallel to the floor.
- The operator's thumb finger is placed over the anterior border of ramus that helps in retraction of tissues mildly as shown in [Figure 1].
- Imaginary midpoint between the upper occlusal plane and lower occlusal plane, in anterior border of ramus is selected [Figure 2] or coronoid notch in the anterior border of mandible is identified.
- 6 to 8 mm above this midpoint or coronoid notch and 8 to 10 mm posterior to the anterior border of ramus is the first site of insertion of needle as shown in [Figure 2].
- The barrel of the syringe is placed between canine and premolars of contra lateral side of extraction and the needle is inserted at the selected site of insertion [Figure 3].
- Now the needle is advanced till it hits the bone that is the medial side of ramus behind anterior border of ramus. Few drops of the Local anesthetic solution are deposited at this place. This may anesthetize the long buccal nerve.
- The thumb finger over anterior border of ramus is withdrawn and allows the free movement of tissues over anterior and medial side of ramus. The barrel of syringe is adjusted towards midline of mandible to insert the needle freely further along the medial side of ramus.
- 'During the course of injection few drops of Lignocaine solution is being deposited to anesthetize the path of insertion and lingual nerve. Here closeness of needle to the medial side surface of ramus is important than position of barrel of syringe. The closeness of needle to ramus is confirmed by frequent touch of tip of the needle on the bone of ramus during the course of injection.
- The needle is advanced further into the tissues supra periosteally towards the target area above the mandibular foramen by following the medial side of ramus as guide.
- When 21 to 24 mm length of the needle is inserted from anterior border of ramus, needle distance with anterior border of ramus was verified as shown in [Figure 4]. According to Malamed study the distance between mandibular foramen and anterior border of ramus is 20 to 24 mm. 
|Figure 4: Verification of length of needle entry from the anterior border of the ramus|
Click here to view
- Now the tip of needle would be superior to IAN entry into its mandibular foramen.
- To bring the tip of needle closer to bone and IAN the barrel of the syringe is taken back to the contra lateral side. The closeness of tip of needle to bone is confirmed by resistance of bone for further entry of needle as shown in [Figure 5].
|Figure 5: Barrel of syringe brought to contralateral side and the needle closeness to the bone is verified and solution deposited|
Click here to view
- One to 1.5 mL of local anesthetic solution should be deposited at this place (pterygomandibular space) to anesthetize inferior alveolar nerve.
- To prevent failure of anesthesia spread the deposition of solution equally from 21 mm distance to 24 mm distance of needle. This helps in deposition of solution over wide area.
- To achieve buccal nerve anesthesia, few drops of local anesthetic solution should be injected into the tissues adjacent to the tooth to be extracted.
The effectiveness of the technique was evaluated by subjective and objective symptoms in the patients.
To test the symptoms of anesthesia the following test was done.
- A sharp dental explorer applied in gingival tissues in front of lower premolar on the extraction side. This was to assess the IAN anesthesia.
- One half of the tongue on the side of extraction was tested with probe to assess lingual nerve anesthesia.
- The tissues adjacent to the tooth to be extracted were tested to check buccal nerve anesthesia. The patient's response was recorded for each test. When patient shows no sign of pain on probing denotes that corresponding nerve is anesthetized. Probe test started after 3 min and repeated after each 2 min. When there were no symptoms of anesthesia of a particular nerve after 7 min denotes failure of the technique that requires repeat of the technique.
Another test used to determine anesthesia was based on the answer from the patient to the following question. Does this area feel numb compared to the other area? This both test are still the most available practical clinical test to ensure an objective anesthesia sign before any dental extraction.  Immediately after achieving a positive response for anesthesia in all three terminal nerve test areas, the extraction began. Out of 500 patients, 476 patients experienced no pain. In the remaining 24 patients second nerve block was given to obtain no pain status.
| Results|| |
The technique proved to be effective in 95% of the cases. The symptoms of IAN anesthesia developed after first nerve block in 476 patients' (95% success rate). The symptoms of IANB developed after the second nerve block of same technique in 24 numbers of patients.
Therefore, more than 95% was the success rate of this technique. Complications such as positive aspirations, trismus, needle breakage, hematoma and nerve injuries were not encountered.
| Discussion|| |
In 1884, William S. Halsted and Richard J. Hall first achieved neuroregional anesthesia in the mandible by injecting a solution of cocaine in the vicinity of the mandibular foramen.  Since then many techniques have been introduced. As a result of the difficulties and failures observed in achieving IANB, various methods of anesthesia have been suggested.  The following anesthetic techniques are available to anesthetize mandibular or IAN, lingual and buccal nerves. Namely
- Conventional IANB;
- Gow-Gates mandibular nerve block;
- Closed mouth block (Vazirani/Akinosi block);
- Fischer 1.2.3 IANB;
- IANB described by Malamed SF.
The conventional IANB is the most commonly used nerve block technique for achieving local anesthesia for mandibular surgical procedures. In certain cases, however, this nerve block fails, even when performed by the most experienced clinician. Unfortunately, this block has a comparatively high failure rate  (15% to 20%). Some authors have estimated the failure rate of this conventional IANB to be approximately 20% to 25%. 
In this technique, the vertical line description two-thirds to three-fourths the distance between the coronoid notch and the posterior border is not very specific and allows for a considerable margin of error.  The selection of site of initial needle entry and anatomical landmarks described by Malamed were difficult to identify and apply by beginners clinically that can lead to failure.
A recognized disadvantage of the Gow-Gates technique is slower onset of anesthesia. Malamed  stated that the Gow-Gates technique has 5 to 7 min latency. Levy  stated that the latency for a central incisor was achieved in 10 to 12 min. Agren and Danielson  stated that the latency can be from 10 to 20, even to 30 min, and in rare cases to 45 min. Joffre and Munzenmayer  achieved a range of 8 to 25 min of induction time in his results. Tiol  stated that 10 to 15 min post injection is a prudent time to wait if anesthesia symptoms have not appeared yet. Malamed further reported when the Gow-Gates technique is administered by inexperienced dental surgeons, it can produce more number of failures and complications than conventional techniques.  It is technically more difficult than the conventional and closed mouth technique.  The success rate depends upon experience of a dental surgeon.
Closed-mouth block (Vazirani/Akinosi block) technique is most useful when the patient cannot open the mouth completely; as is the case with trismus no bony landmark is available when performing this technique. Hence, a small chance exists of over inserting the needle and injuring the vessels in the pterygoid plexus.  Failures were observed in the conventional inferior nerve block and in the Akinosi block technique.  According to the Malamed Closed-mouth block technique has a more failure rate than conventional IANB.  This technique cannot be used due to its higher rate of failures. Thus, most dental professionals do not utilize the Gow-Gates and Akinosi techniques.  Despite the reported advantages of the Gow-Gates and Akinosi techniques, the findings from this study indicated that only a small percentage of clinicians trained in these injection techniques choose to use them as their primary means of establishing mandibular anesthesia and a large percentage completely abandoned these techniques. 
Fischer 1, 2, 3, technique relies on the presence and identification of anatomical landmarks such as the external oblique ridge, coronoid notch, apex of buccal pad of fat, pterygomandibular raphe, and the retro molar pad. Failure to identify those landmarks may result in improper technique and failure of anesthesia. During the course of injection in the first stage 3-6 mm distance, second stage 12 mm distance, and in the third stage 24 mm distance of needle insertion to be made from 42 mm length needle. Since there are no markings in the needle it is difficult to apply by operators. The possibility of over penetration may result in this technique that may result in facial palsy.
The technical difficulties and failure of anesthesia in all the available IANBs were written in literature and reviews. It is essential to find an alternative technique that has a minimal failure rate. The technique described in this study would be an ideal alternative option for the current techniques due to its non reliability of several anatomical landmarks and its higher success rate. The anatomical landmarks described in this IANB technique were
(a) Anterior border of ramus and (b) Mandibular occlusal plane.
Since the highest distance of mandibular foramen from the level of the occlusal plane is 11 mm,  the selection of site of initial needle puncture is 12 to 16 mm above the occlusal plane and also it is essential to insert the needle to a distance of 20 to 25 mm from anterior border to reach the space above mandibular foramen,  then the needle tip would be nearer and above the nerve entry. This favors the placement of the tip of needle superior to mandibular foramen, on complete insertion of 22 to 24 mm needle distance from the anterior border. The deposition solution above foramen and nearer to nerve baths the IAN results in effective anesthesia. The maintenance of needle nearer to bone helps to avoid deposition of solution into the muscle that prevents post injection trismus.
In our study only 24 patients (5%) of the sample required second injection to produce the satisfactory level of anaesthesia. This may be due to anatomical variation of the mandibular foramen in the patients itself but exact cause is not known.
Thus, with abovementioned all advantages our study concludes IANB is an ideal option in anesthesia of IAN, lingual, and buccal nerve.
| Conclusion|| |
This study concludes that IANB is an appropriate alternative nerve block to anesthetize IAN due to its several advantages.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]