J Oral Maxillofac
Surg
49:904-909,1991
A Comparative Study of the Extra-intraoral Landmark Technique and the Direct Technique for Inferior Alveolar Nerve Block AURASA WAIKAKUL,
BSc, DDS, MS,* AND JIRAPUN PUNWUTIKORN,
BSc, DDS*
Currently, the inferior alveolar nerve block is sometimes ineffective for a number of reasons. The extra-intraoral landmark technique (EIL technique) was modified and compared in effectiveness with the direct technique in patients undergoing inferior alveolar nerve block. The results showed that the success rates of the EIL technique based on both subjective and objective responses were significantly greater than those of the direct technique. The EIL technique also resulted in significantly less pain from the injection than the direct technique.
Local anesthesia for inferior alveolar nerve block has been commonly used for pain control of the mandible. The classic technique was originally developed by FischerIT and later modified by many authors,3-5 but the results have often been ineffective owing to variations in the anatomy of the mandible.6 More recently, Gow-Gates’ described a new technique using extraoral landmarks, and Akinosi’ developed a closed-mouth intraoral technique. Several investigators have tried to compare these new techniques with the standard procedure. Sisk’ reported no significant differences in effectiveness between the Gow-Gates technique and the standard one. Some author@**’ have found the Gow-Gates technique significantly less effective than the conventional one. Except for its advantage in overcoming the limitation of mouth opening, the Akinosi technique also gave no better success rate than the conventional technique.‘,” Basically, the intraoral soft tissues are not suffi-
ciently well-defined landmarks for localizing the injection point and determining the depth of the advancing needle. The soft-tissue landmarks vary in location depending on position of patient’s head and neck, gape of the mouth, individual variation of the patient’s anatomy, and the form of the skeleton. Although bony landmarks are more reliable than soft-tissue landmarks, more predictable indicators for locating the position of the mandibular foramen are needed. This has been confirmed by several reports of the unpredictability of the mandibular nerve block.6.“.‘3-‘7 The classic inferior alveolar nerve block, the Akinosi’s closed-mouth intraoral technique, and the Gow-Gates technique do not use the posterolateral portion of the mandibular ramus as a principal landmarks.18 According to Hetson,” the narrowest anteroposterior width of the mandibular ramus is one of the most reliable landmarks for prediction of the position of the mandibular foramen. The extra-intraoral landmark technique (EIL technique) developed by the authors” is a modified technique for inferior alveolar nerve block that uses the same intraoral landmark as the direct technique but adds the posterolateral portion of the mandible as an additional extraoral landmark for locating the mandibular foramen. By using the middle fingertip placed at the posterolateral surface just anterior to the deepest concavity of the posterior border of the mandibular ramus halfway between the condylar
Received from the Department of Oral Surgery, Faculty of Dentistry. Mahidol University. Bangkok, Thailand. * Assistant Professor. Supported in part by a grant from Mahidol University, 1988. Address correspondence and reprint requests to Dr Waikakul: Department of Oral Surgery, Faculty of Dentistry, Mahidol University, Bangkok 10400. Thailand. 0 1991 American geons
Association
of Oral and Maxillofacial
Sur-
0278-2391/91/4908-0005$3.00/0
804
WAIKAKUL
AND PUNWUTIKORN
head and inferior angle of the mandible as a guide, the advancement of the needle to the mandibular foramen is done. This extraoral landmark helps determine the direction of the needle and location of the mandibular foramen. The purpose of this study was to compare the effectiveness of the classic inferior alveolar nerve block procedure, or the direct technique, and the extra-intraoral landmark technique. Materials and Methods Patients who came to the Oral Surgery Clinic, Faculty of Dentistry, Mahidol University for mandibular tooth extraction were selected for this study. Sampling was done using the following criteria: patients must have had previous experience with an inferior alveolar nerve block; they had to have neither pathology of the mandible nor neurologic defects of the trigeminal nerve; and they had to be in good health and have no systemic diseases that would contraindicate local anesthesia and exodontia. The double-blind study was done on 136 patients, 77 females and 59 males, ranging in age from 11 to 70 years. They were divided equally into two groups: a control group that underwent the direct technique as described by Bennett” and the experimental group, with which the EIL technique was used. In the control group, 30 injections were done on the right side and 38 injections on the left side. With the EIL technique, 24 injections were done on the right side and 44 injections on the left. The direct technique, as described by Bennett, I8 was performed with the patient’s mouth wide open and the body of the mandible parallel to the floor. The operator identified the coronoid notch with the thumb of the left hand and moved lingually onto the internal oblique ridge. Having located the intraoral landmarks with the thumb, the operator placed the index finger extraorally behind the ramus of the mandible, thus holding it between the thumb and index finger. The injection point lay about 1 cm above the occlusal surface of the molars. The needle was inserted at a level bisecting the thumbnail, parallel to the occlusal plane of the mandibular teeth, with the syringe directed from opposite side of the mouth. The needle was inserted until it contacted the medial side of the ramus. It was then withdrawn 1 to 2 mm, carefully aspirated, and 1 mL of the anesthetic solution was injected over a 60- to 90-second interval. The remaining solution was reserved for the lingual nerve (0.5 mL) and the long buccal nerve block (0.3 mL). The EIL technique was performed by using intraoral landmarks for locating the injection point as
805 described by Bennett.” After the thumb of the left hand was placed on the coronoid notch, the extraoral landmark was established by placing the left middle finger at the deepest concavity of the posterior border of the ramus, which should be midway between the condyle and the inferior border of the mandibular angle. The distance between the thumb and the middle finger should be the narrowest anteroposterior width of the ramus. The left middle finger was then moved anteriorly and laterally along the outer side of the ramus until the fingertip just passed the posterior border of the ramus. The center of the pad of the tip of the middle finger should then be approximately 1 cm anterior to the deepest concavity of the posterior border of the ramus. The mandibular foramen should be located on the medial side of the ramus underneath the center of the pad of the middle fingertip. The needle was then inserted at the level of the thumb, and advanced directly to the center of the pad of the middle tingertip, as if trying to inject it. When the needle contacted the medial side of the ramus, the syringe was withdrawn 1 to 2 mm and the anesthetic solution was deposited as follows: 1 mL of the anesthetic solution was injected over an interval of 60 to 90 seconds for the mandibular nerve block, 0.5 mL for the lingual nerve block during withdrawal of the needle in the same injection, and the remaining 0.3 mL was reserved for the long buccal nerve. The operators were all Sth-year students in a 6year dental program and had had very few experiences in using either technique. The local anesthetic solution used was 1.8 mL of 2% lidocaine HCI with I : 100,000 epinephrine injected with a 27-gauge, 30mm-long disposable needle. The randomized matching of the operators and techniques was done just prior to the injection by the first investigator, who recorded information about the patient, technique employed, pain during injection, and also measured the depth of the needle with a marked probe. A automatic timer was started immediately after the needle was withdrawn. The second investigator, who was not aware of which technique had been used, entered the room after the departure of the first investigator and recorded the patient’s feelings concerning the onset of tingling or thickening sensations on the lower lip, tongue, cheek of the affected side at l-minute intervals till the patient appreciated a complete numbness, a marked difference, or thickening of the affected lower lip in comparison with the other side. If none of these symptoms occurred within 10 minutes after injection, it was classified as a failure. Explorer testing was then performed on the lower lip at 81/2. 9, 9M,
806
EXTRA-INTRAORAL
10, and 10% minutes after injection and on the labial and lingual gingiva of the permanent canine at 10 minutes after the injection. The data were collected and analyzed using the x2 test, with the critical level of significance set at P = .05. Results
20
LANDMARK
TECHNIQUE
No. of patients
16'
6
Blood was not aspirated into the cartridge in any patient in both groups. The number of patients reporting no pain on injection was significantly higher in the EIL technique group (67 of 68,98.5%) than in the control group (49 of 68, 72.1%) (P < .05). ONSET
The subjective results of the onset time are shown in Figure 1. Most of the patients in both groups reported onset of numbness within 3 minutes after injection; 60 of 68 (88.2%) in the EIL group and 47 of 68 (69.1%) in the control group. The rest felt the onset between 3 to 10 minutes postinjection. SUCCESSRATE
Forty-five of 68 patients (66.2%) receiving the EIL technique reported complete numbness within 2 to 5 minutes after injection and only 2 patients (2.9%) reported inadequate numbness of the lower lip after 10 minutes, indicating failure of the inferior alveolar nerve block (Fig 2). In the control group, 47.1% (32 of 68) reported complete numbness within 2 to 5 minutes postinjection and a failure rate of 22.1% (15 of 68), which was significantly greater than in the EIL group (x2 = 9.68, P < .05). The EIL group also had a greater percentage of
0-U
a9 o-1
l-2
2-3
3-4
4-6
6-6
6-7
7-6
6-9
9-10
lO*
Time interval (mid FIGURE 2. Number of patients who reported complete numbness, at l-minute intervals with the extra-intraoral landmark technique (u, EIL) and direct technique (EJ, D) for inferior alveolar nerve block. Patients who did not report numbness by 10 minutes were classified as failures.
patients who subjectively reported numbness of the tongue (97. I%, 66 of 68) and the cheek (63.2%, 43 of 68) than the control group (92.6%, 63 of 68; 52.9%, 36 of 68). Most patients of both groups had numbness to the explorer test on the lower lip at 8ti minutes. Pain induced by the explorer test on the lower lip after 10 minutes postinjection was only found in 13.2% of the EIL group (9 of 68), which was significantly less than the 39.7% (27 of 68) in the control group (x2 = 10.92, P < .05) (Fig 3). Numbness on the labial and lingual gingiva to the explorer test was significantly greater in the EIL group than the control group at 10 minutes postinjection (x2 = 10.55, P < .05; Table I). Table 2 summarizes the subjective and objective results of inferior alveolar nerve block by the EIL and the direct techniques. This table shows the superior effectiveness of the EIL technique to the direct technique in terms of onset within 3 minutes postinjection, or marked numbness of lower lip within 2 to 5 minutes postinjection, or the explorer test on the lower lip and labial gingiva.
No. of patients 36 I No. of patknh
ear 26
60
20
40
16
30
10 20 6 10
n
”
o-1
l-2
2-3
3-4
4-6
6-6
O-7
7-0
6-9
9-x)
lO+
Time Interval (mln) FIGURE 1. Number of patients who reported onset of symptoms at l-minute intervals with the extra-intraoral landmark technique (m, EIL) and direct technique (6% D) for inferior alveolar nerve block. Patients who did not report symptoms by 10 minutes were classified as injection failures.
Tbne(mln) FIGURE 3. Number of patients who developed complete numbness (no pain) by explorer test in the extra-intraoral landmark technique (m. EIL) and direct technique (B, D) at halfminute intervals from 8% to 10 minutes postinjection.
WAIKAKUL
807
AND PUNWUTIKORN
Table 1. Numbers and Percentages of Patients Who Had Posftive Test for Numbness on the Labial and Lingual Oingiva of Mandibular Canine by the Explorer Test at 10 Minutes After the Injection With Each Method Positive Numbness (Objective) Method
Lingd
Labial
61/68 (89.7%) 52168 (76.5%)
58/68 (85.3%‘) 40/68 (58.8%:)
EIL Direct
DEPTH
OF THE NEEDLE
The various depths to which the needle was advanced into the mucosa and underlying tissues are presented in Table 3. In both techniques, 80.9% (55 of 68) of the injections penetrated 20 to 25 mm during performance of the inferior alveolar nerve block. Discussion
The number of patients who perceived less painful injections were higher in the EIL group than in the control group. Probably the EIL technique gave the operator more confidence in direction and position of the needle than the other. The needle therefore could be advanced without hesitation or any deviation that might be a cause of pain. Most of the operators (45 of 68) who performed the EIL technique in this study said that they had more confidence in doing the inferior alveolar nerve block than ever before; only 18 of 68 operators felt no difference between the two techniques. Of the remaining operators, 3 felt that EIL technique made the injection more complicated while 2 felt this technique gave them less confidence. Effective injections for inferior alveolar nerve Table 2. Summary of the Success and Failure Rates Between the EIL Technique and the Direct Technique Tests Onset (subjective) Positive response within 3 minutes Negative response after 10 minutes Complete numbness (subjective) Positive response within 2 to 5 minutes Inadequate numbness after IO minutes Explorer test at 10 minutes Failure rate at lower lip Failure rate at labial gingiva
ElL
Direct
60168 (88.2%)
47/68 (69.1%)
0168 (0%)
S/68 ( 11.8%)
45168 (66.2%)
32168 (47.1%)
2168 (2.9%)
15/68 (22.1%)
9168 (13.2%)
27/68 (39.7%)
10168(14.7%)
28168 (41.2%)
Table 3. Various Depths to Which the Needles Were Advanced Depth of needle (mm)* Method
izo
20-2s
EIL Direct
1 7
55 55
i25
12 6
Total Injections 68 68
* A Terumo dental needle, 27-gauge, 30-mm long, was used.
block should produce the onset of symptoms within 3 minutes and give complete numbness within 5 minutes postinjection. A delayed onset time would indicate the possibility of failure. In this study, the failure of inferior alveolar nerve block in the control group, as determined by various indicators, ranged from 11.8% to 41.2%. The EIL technique seemed to help in reducing the failure rate to a range of 0% to 14.7%. This relatively low range compares with Migrom’s14 5.5% to 29.5%, Malamed’s2’ 3% to 20%. and Rood’sz3 report of 20%, which might be taken as standard failure rates. Interestingly, most of the operators (80.9%) in both groups advanced the needle to similar depths, 20 to 25 mm. However, the needle was passed beyond 25 mm in 17.6% with the EIL technique, whereas with the direct technique 10.3% advanced the needle less than 20 mm and 8.8% passed it beyond 25 mm (Table 3). The wider range in depth of needle insertion in the direct technique might reflect the uncertainty in direction and termination site of the needle. Two factors that influence the success rate of inferior alveolar nerve block are the amount of anesthetic agent and accuracy of anesthetic deposition. According to Rood,” an inadequate amount of anesthetic agent would probably fail to induce an absolute nerve block. In another word, an injection that does not accurately deposit the right amount of the anesthetic agent in the right place would result in prolonged onset as well as an incomplete nerve block. The advantage of the EIL technique lies in using additional extraoral bony landmarks, which results in more precise location of the mandibular foramen. The technique is also unaffected by the patient’s head position and soft-tissue variations. References 1. Fischer G: Lokale Anasthesie. Berlin. Germany. Hermann Meuser, 1919 2. Fischer G: Die ortliche Betaubung in der Lahnheilkunde mit besonderer Beriicksichtigung der Schleimhaut und Lutungsanasthesoe. Mtlnchen. Germany. John Ambrosius Barth Verlag, 1955 3. Lindsay AW: The importance of pterygotemporal space in mandibular anesthesia, in Nevin M (ed): Problems in Dental Local Anesthesia. Brooklyn, NY. Dental Items of Interest Publishing Company. 1952, pp 295-299
808
DISCUSSION
4. Sicher H, Du Brul EL: Oral Anatomy (ed 5). St Louis, MO, Mosby, 1970 5. Jorgensen NB, Hayden JS: Premeditation, local and general anesthesia in dentistry. Philadelphia, PA, Lea & Febiger. 1967 6. Agren E, Danielsson K: Conduction block analgesia in the mandible: A comparative investigation of the techniques of Fischer and Gow-Gates. Swed Dent J 581, 1981 7. Gow-Gates GAE: Mandibular conduction anesthesia: A new technique using extraoral landmarks. Oral Surg 36:321, 1973 8. Akinosi JO: A new approach to the mandibular nerve block. Br J Oral Surg 15:83, 1977 9. Sisk AL: Evaluation of the Akinosi mandibular block technique in oral surgery. J Oral Maxillofac Surg 4: 113, 1986 10. Montagnese TA, Reader A, Melfi R: A comparative study of the Gow-Gates technique and a standard technique for mandibular anesthesia. J Endod 10: 158, 1984 11. Berezowski BM. Lownie JF. Cleaton-Jones PE: A comuarison of two methods of inferior alveolar nerve block. J Dent 16:96, 1988 12. Sato K: The closed mouth intraoral technique of achieving mandibular anesthesia. Honolulu. HI, Saint Francis Hospital, July 28, 1982 (abstr) 13. Kaufman E, Weinstein P, Milgrom P: Difficulties in achieving local anesthesia. J Am Dent Assoc 108:205, 1984
J Oral Maxillofac 49:909-909,
14. Milgrom P, Weinstein P, Kuafman E: Student difficulties in achieving local anesthesia. J Dent Educ 48:168, 1984 15. Sisk AL: Evaluation of the Gow-Gates mandibular block for oral surgery. Anesth Prog 32:143, 1985 16. Sexton R, Howkins M: Trouble shooting in local anesthesia: Gow-Gates mandibular block. Ont Dent 62:20, 1985 17. Yamada A, Jasstak JT: Clinical evaluation of the Gow-Gates block in children. Anesth Prog 28: 106, 1981 18. Bennett CR: Monheim’s Local Anesthesia and Pain Control in Dental Practice (ed 7). St Louis, MO, Mosby, 1984, pp 99-113 19. Hetson G, Share J, Frommer J, et al: Statistical evaluation of the position of the mandibular foramen. Oral Surg 65:32, 1988 20. Waikakul A, Punwutikom J: Extra-intraoral landmarks technique for inferior alveolar nerve block. J Oral Maxillofac Surg (in press) 2 1. Rood JP: Some anatomical and physiological causes of failure to achieve mandibular analgesia. Br J Oral Surg 15:75, 1977 22. Malamed SF: The periodontal ligament (PDL) injection: An alternative to inferior alveolar nerve block. Oral Surg 53: 117, 1982 23. Rood JP: The analgesia and innervation of mandibular teeth. Br Dent J 140:237, 1976
Surg
1991
Discussion A Comparative Study of the Extra-intraoral Landmark Technique and the Direct Technique for Inferior Alveolar Nerve Block Stanley F. Malamed,
DDS
University of Southern California School of Dentistry, Los Angeles
Providing clinically adequate pain control in the mandible has proved to be a problem vexing dentists throughout the world for as long as dentistry has existed as a profession. The classic inferior alveolar nerve block, originally described by Fischer in 1919 and modified over the ensuing years by others, has long been considered the conventional technique for obtaining mandibular anesthesia. It was not until 1973, with the publication by GowGates’ of a new approach to mandibular anesthesia, that dentistry began to seriously consider alternatives to the conventional approach. Though not employed by all dentists, what is known as the Gow-Gates mandibular block has gained a significant foothold in the armamentarium of pain control techniques in the mandible. In an as yet unpublished survey of over 3,000 dentists,2 approximately 95% had heard of this technique, with 73% employing it, to some extent, in their practice. Success reported with the Gow-Gates technique has varied from somewhat less than the conventional3 to considerably more.4 The GowGates technique takes into account the fact that the most oft-stated reason for failure to achieve adequate mandibular anesthesia is deposition of the solution inferior to the
mandibular foramen, the site at which the inferior alveolar nerve enters the mandibular canal and becomes insulated from the anesthetic solution. Depositing anesthetic at the neck of the condyloid process in the Gow-Gates technique provides more ready access to V-3 and, with clinical experience, a greater rate of clinically adequate anesthesia than that provided by the conventional technique. Probably the most important result arising from publication of the Gow-Gates mandibular block technique is that it made dentists think about possible alternative approaches to achieving mandibular anesthesia. Several years later another approach to mandibular anesthesia appeared-one that purported to provide successful anesthesia in situations in which the patient was unable (as a result of trismus or mandibular fracture) to open their mouth.’ The Akinosi closed-mouth mandibular block technique is employed by 5% of dentists surveyed’ and usually as a secondary technique to either the conventional or Gow-Gates blocks. A significant benefit of the Akinosi technique is that it provides anesthesia of the motor as well as the sensory components of V-3, thereby providing relief from trismus, permitting the dentist to more easily manage the patient’s dental complaints. Because bone is not contacted in the Akinosi technique, its success rate has been found to be somewhat lower than either the conventional or Gow-Gates blocks. However, neither the Gow-Gates nor conventional inferior alveolar nerve blocks can even be attempted when patients are unable to open their mouth. The incisive (mental) nerve block is another technique that is of importance to dentistry. Profound anesthesia of the premolars, canine, and incisors can be achieved consistently (295%) with this injection technique, which is
Surg
49:904-909,1991
A Comparative Study of the Extra-intraoral Landmark Technique and the Direct Technique for Inferior Alveolar Nerve Block AURASA WAIKAKUL,
BSc, DDS, MS,* AND JIRAPUN PUNWUTIKORN,
BSc, DDS*
Currently, the inferior alveolar nerve block is sometimes ineffective for a number of reasons. The extra-intraoral landmark technique (EIL technique) was modified and compared in effectiveness with the direct technique in patients undergoing inferior alveolar nerve block. The results showed that the success rates of the EIL technique based on both subjective and objective responses were significantly greater than those of the direct technique. The EIL technique also resulted in significantly less pain from the injection than the direct technique.
Local anesthesia for inferior alveolar nerve block has been commonly used for pain control of the mandible. The classic technique was originally developed by FischerIT and later modified by many authors,3-5 but the results have often been ineffective owing to variations in the anatomy of the mandible.6 More recently, Gow-Gates’ described a new technique using extraoral landmarks, and Akinosi’ developed a closed-mouth intraoral technique. Several investigators have tried to compare these new techniques with the standard procedure. Sisk’ reported no significant differences in effectiveness between the Gow-Gates technique and the standard one. Some author@**’ have found the Gow-Gates technique significantly less effective than the conventional one. Except for its advantage in overcoming the limitation of mouth opening, the Akinosi technique also gave no better success rate than the conventional technique.‘,” Basically, the intraoral soft tissues are not suffi-
ciently well-defined landmarks for localizing the injection point and determining the depth of the advancing needle. The soft-tissue landmarks vary in location depending on position of patient’s head and neck, gape of the mouth, individual variation of the patient’s anatomy, and the form of the skeleton. Although bony landmarks are more reliable than soft-tissue landmarks, more predictable indicators for locating the position of the mandibular foramen are needed. This has been confirmed by several reports of the unpredictability of the mandibular nerve block.6.“.‘3-‘7 The classic inferior alveolar nerve block, the Akinosi’s closed-mouth intraoral technique, and the Gow-Gates technique do not use the posterolateral portion of the mandibular ramus as a principal landmarks.18 According to Hetson,” the narrowest anteroposterior width of the mandibular ramus is one of the most reliable landmarks for prediction of the position of the mandibular foramen. The extra-intraoral landmark technique (EIL technique) developed by the authors” is a modified technique for inferior alveolar nerve block that uses the same intraoral landmark as the direct technique but adds the posterolateral portion of the mandible as an additional extraoral landmark for locating the mandibular foramen. By using the middle fingertip placed at the posterolateral surface just anterior to the deepest concavity of the posterior border of the mandibular ramus halfway between the condylar
Received from the Department of Oral Surgery, Faculty of Dentistry. Mahidol University. Bangkok, Thailand. * Assistant Professor. Supported in part by a grant from Mahidol University, 1988. Address correspondence and reprint requests to Dr Waikakul: Department of Oral Surgery, Faculty of Dentistry, Mahidol University, Bangkok 10400. Thailand. 0 1991 American geons
Association
of Oral and Maxillofacial
Sur-
0278-2391/91/4908-0005$3.00/0
804
WAIKAKUL
AND PUNWUTIKORN
head and inferior angle of the mandible as a guide, the advancement of the needle to the mandibular foramen is done. This extraoral landmark helps determine the direction of the needle and location of the mandibular foramen. The purpose of this study was to compare the effectiveness of the classic inferior alveolar nerve block procedure, or the direct technique, and the extra-intraoral landmark technique. Materials and Methods Patients who came to the Oral Surgery Clinic, Faculty of Dentistry, Mahidol University for mandibular tooth extraction were selected for this study. Sampling was done using the following criteria: patients must have had previous experience with an inferior alveolar nerve block; they had to have neither pathology of the mandible nor neurologic defects of the trigeminal nerve; and they had to be in good health and have no systemic diseases that would contraindicate local anesthesia and exodontia. The double-blind study was done on 136 patients, 77 females and 59 males, ranging in age from 11 to 70 years. They were divided equally into two groups: a control group that underwent the direct technique as described by Bennett” and the experimental group, with which the EIL technique was used. In the control group, 30 injections were done on the right side and 38 injections on the left side. With the EIL technique, 24 injections were done on the right side and 44 injections on the left. The direct technique, as described by Bennett, I8 was performed with the patient’s mouth wide open and the body of the mandible parallel to the floor. The operator identified the coronoid notch with the thumb of the left hand and moved lingually onto the internal oblique ridge. Having located the intraoral landmarks with the thumb, the operator placed the index finger extraorally behind the ramus of the mandible, thus holding it between the thumb and index finger. The injection point lay about 1 cm above the occlusal surface of the molars. The needle was inserted at a level bisecting the thumbnail, parallel to the occlusal plane of the mandibular teeth, with the syringe directed from opposite side of the mouth. The needle was inserted until it contacted the medial side of the ramus. It was then withdrawn 1 to 2 mm, carefully aspirated, and 1 mL of the anesthetic solution was injected over a 60- to 90-second interval. The remaining solution was reserved for the lingual nerve (0.5 mL) and the long buccal nerve block (0.3 mL). The EIL technique was performed by using intraoral landmarks for locating the injection point as
805 described by Bennett.” After the thumb of the left hand was placed on the coronoid notch, the extraoral landmark was established by placing the left middle finger at the deepest concavity of the posterior border of the ramus, which should be midway between the condyle and the inferior border of the mandibular angle. The distance between the thumb and the middle finger should be the narrowest anteroposterior width of the ramus. The left middle finger was then moved anteriorly and laterally along the outer side of the ramus until the fingertip just passed the posterior border of the ramus. The center of the pad of the tip of the middle finger should then be approximately 1 cm anterior to the deepest concavity of the posterior border of the ramus. The mandibular foramen should be located on the medial side of the ramus underneath the center of the pad of the middle fingertip. The needle was then inserted at the level of the thumb, and advanced directly to the center of the pad of the middle tingertip, as if trying to inject it. When the needle contacted the medial side of the ramus, the syringe was withdrawn 1 to 2 mm and the anesthetic solution was deposited as follows: 1 mL of the anesthetic solution was injected over an interval of 60 to 90 seconds for the mandibular nerve block, 0.5 mL for the lingual nerve block during withdrawal of the needle in the same injection, and the remaining 0.3 mL was reserved for the long buccal nerve. The operators were all Sth-year students in a 6year dental program and had had very few experiences in using either technique. The local anesthetic solution used was 1.8 mL of 2% lidocaine HCI with I : 100,000 epinephrine injected with a 27-gauge, 30mm-long disposable needle. The randomized matching of the operators and techniques was done just prior to the injection by the first investigator, who recorded information about the patient, technique employed, pain during injection, and also measured the depth of the needle with a marked probe. A automatic timer was started immediately after the needle was withdrawn. The second investigator, who was not aware of which technique had been used, entered the room after the departure of the first investigator and recorded the patient’s feelings concerning the onset of tingling or thickening sensations on the lower lip, tongue, cheek of the affected side at l-minute intervals till the patient appreciated a complete numbness, a marked difference, or thickening of the affected lower lip in comparison with the other side. If none of these symptoms occurred within 10 minutes after injection, it was classified as a failure. Explorer testing was then performed on the lower lip at 81/2. 9, 9M,
806
EXTRA-INTRAORAL
10, and 10% minutes after injection and on the labial and lingual gingiva of the permanent canine at 10 minutes after the injection. The data were collected and analyzed using the x2 test, with the critical level of significance set at P = .05. Results
20
LANDMARK
TECHNIQUE
No. of patients
16'
6
Blood was not aspirated into the cartridge in any patient in both groups. The number of patients reporting no pain on injection was significantly higher in the EIL technique group (67 of 68,98.5%) than in the control group (49 of 68, 72.1%) (P < .05). ONSET
The subjective results of the onset time are shown in Figure 1. Most of the patients in both groups reported onset of numbness within 3 minutes after injection; 60 of 68 (88.2%) in the EIL group and 47 of 68 (69.1%) in the control group. The rest felt the onset between 3 to 10 minutes postinjection. SUCCESSRATE
Forty-five of 68 patients (66.2%) receiving the EIL technique reported complete numbness within 2 to 5 minutes after injection and only 2 patients (2.9%) reported inadequate numbness of the lower lip after 10 minutes, indicating failure of the inferior alveolar nerve block (Fig 2). In the control group, 47.1% (32 of 68) reported complete numbness within 2 to 5 minutes postinjection and a failure rate of 22.1% (15 of 68), which was significantly greater than in the EIL group (x2 = 9.68, P < .05). The EIL group also had a greater percentage of
0-U
a9 o-1
l-2
2-3
3-4
4-6
6-6
6-7
7-6
6-9
9-10
lO*
Time interval (mid FIGURE 2. Number of patients who reported complete numbness, at l-minute intervals with the extra-intraoral landmark technique (u, EIL) and direct technique (EJ, D) for inferior alveolar nerve block. Patients who did not report numbness by 10 minutes were classified as failures.
patients who subjectively reported numbness of the tongue (97. I%, 66 of 68) and the cheek (63.2%, 43 of 68) than the control group (92.6%, 63 of 68; 52.9%, 36 of 68). Most patients of both groups had numbness to the explorer test on the lower lip at 8ti minutes. Pain induced by the explorer test on the lower lip after 10 minutes postinjection was only found in 13.2% of the EIL group (9 of 68), which was significantly less than the 39.7% (27 of 68) in the control group (x2 = 10.92, P < .05) (Fig 3). Numbness on the labial and lingual gingiva to the explorer test was significantly greater in the EIL group than the control group at 10 minutes postinjection (x2 = 10.55, P < .05; Table I). Table 2 summarizes the subjective and objective results of inferior alveolar nerve block by the EIL and the direct techniques. This table shows the superior effectiveness of the EIL technique to the direct technique in terms of onset within 3 minutes postinjection, or marked numbness of lower lip within 2 to 5 minutes postinjection, or the explorer test on the lower lip and labial gingiva.
No. of patients 36 I No. of patknh
ear 26
60
20
40
16
30
10 20 6 10
n
”
o-1
l-2
2-3
3-4
4-6
6-6
O-7
7-0
6-9
9-x)
lO+
Time Interval (mln) FIGURE 1. Number of patients who reported onset of symptoms at l-minute intervals with the extra-intraoral landmark technique (m, EIL) and direct technique (6% D) for inferior alveolar nerve block. Patients who did not report symptoms by 10 minutes were classified as injection failures.
Tbne(mln) FIGURE 3. Number of patients who developed complete numbness (no pain) by explorer test in the extra-intraoral landmark technique (m. EIL) and direct technique (B, D) at halfminute intervals from 8% to 10 minutes postinjection.
WAIKAKUL
807
AND PUNWUTIKORN
Table 1. Numbers and Percentages of Patients Who Had Posftive Test for Numbness on the Labial and Lingual Oingiva of Mandibular Canine by the Explorer Test at 10 Minutes After the Injection With Each Method Positive Numbness (Objective) Method
Lingd
Labial
61/68 (89.7%) 52168 (76.5%)
58/68 (85.3%‘) 40/68 (58.8%:)
EIL Direct
DEPTH
OF THE NEEDLE
The various depths to which the needle was advanced into the mucosa and underlying tissues are presented in Table 3. In both techniques, 80.9% (55 of 68) of the injections penetrated 20 to 25 mm during performance of the inferior alveolar nerve block. Discussion
The number of patients who perceived less painful injections were higher in the EIL group than in the control group. Probably the EIL technique gave the operator more confidence in direction and position of the needle than the other. The needle therefore could be advanced without hesitation or any deviation that might be a cause of pain. Most of the operators (45 of 68) who performed the EIL technique in this study said that they had more confidence in doing the inferior alveolar nerve block than ever before; only 18 of 68 operators felt no difference between the two techniques. Of the remaining operators, 3 felt that EIL technique made the injection more complicated while 2 felt this technique gave them less confidence. Effective injections for inferior alveolar nerve Table 2. Summary of the Success and Failure Rates Between the EIL Technique and the Direct Technique Tests Onset (subjective) Positive response within 3 minutes Negative response after 10 minutes Complete numbness (subjective) Positive response within 2 to 5 minutes Inadequate numbness after IO minutes Explorer test at 10 minutes Failure rate at lower lip Failure rate at labial gingiva
ElL
Direct
60168 (88.2%)
47/68 (69.1%)
0168 (0%)
S/68 ( 11.8%)
45168 (66.2%)
32168 (47.1%)
2168 (2.9%)
15/68 (22.1%)
9168 (13.2%)
27/68 (39.7%)
10168(14.7%)
28168 (41.2%)
Table 3. Various Depths to Which the Needles Were Advanced Depth of needle (mm)* Method
izo
20-2s
EIL Direct
1 7
55 55
i25
12 6
Total Injections 68 68
* A Terumo dental needle, 27-gauge, 30-mm long, was used.
block should produce the onset of symptoms within 3 minutes and give complete numbness within 5 minutes postinjection. A delayed onset time would indicate the possibility of failure. In this study, the failure of inferior alveolar nerve block in the control group, as determined by various indicators, ranged from 11.8% to 41.2%. The EIL technique seemed to help in reducing the failure rate to a range of 0% to 14.7%. This relatively low range compares with Migrom’s14 5.5% to 29.5%, Malamed’s2’ 3% to 20%. and Rood’sz3 report of 20%, which might be taken as standard failure rates. Interestingly, most of the operators (80.9%) in both groups advanced the needle to similar depths, 20 to 25 mm. However, the needle was passed beyond 25 mm in 17.6% with the EIL technique, whereas with the direct technique 10.3% advanced the needle less than 20 mm and 8.8% passed it beyond 25 mm (Table 3). The wider range in depth of needle insertion in the direct technique might reflect the uncertainty in direction and termination site of the needle. Two factors that influence the success rate of inferior alveolar nerve block are the amount of anesthetic agent and accuracy of anesthetic deposition. According to Rood,” an inadequate amount of anesthetic agent would probably fail to induce an absolute nerve block. In another word, an injection that does not accurately deposit the right amount of the anesthetic agent in the right place would result in prolonged onset as well as an incomplete nerve block. The advantage of the EIL technique lies in using additional extraoral bony landmarks, which results in more precise location of the mandibular foramen. The technique is also unaffected by the patient’s head position and soft-tissue variations. References 1. Fischer G: Lokale Anasthesie. Berlin. Germany. Hermann Meuser, 1919 2. Fischer G: Die ortliche Betaubung in der Lahnheilkunde mit besonderer Beriicksichtigung der Schleimhaut und Lutungsanasthesoe. Mtlnchen. Germany. John Ambrosius Barth Verlag, 1955 3. Lindsay AW: The importance of pterygotemporal space in mandibular anesthesia, in Nevin M (ed): Problems in Dental Local Anesthesia. Brooklyn, NY. Dental Items of Interest Publishing Company. 1952, pp 295-299
808
DISCUSSION
4. Sicher H, Du Brul EL: Oral Anatomy (ed 5). St Louis, MO, Mosby, 1970 5. Jorgensen NB, Hayden JS: Premeditation, local and general anesthesia in dentistry. Philadelphia, PA, Lea & Febiger. 1967 6. Agren E, Danielsson K: Conduction block analgesia in the mandible: A comparative investigation of the techniques of Fischer and Gow-Gates. Swed Dent J 581, 1981 7. Gow-Gates GAE: Mandibular conduction anesthesia: A new technique using extraoral landmarks. Oral Surg 36:321, 1973 8. Akinosi JO: A new approach to the mandibular nerve block. Br J Oral Surg 15:83, 1977 9. Sisk AL: Evaluation of the Akinosi mandibular block technique in oral surgery. J Oral Maxillofac Surg 4: 113, 1986 10. Montagnese TA, Reader A, Melfi R: A comparative study of the Gow-Gates technique and a standard technique for mandibular anesthesia. J Endod 10: 158, 1984 11. Berezowski BM. Lownie JF. Cleaton-Jones PE: A comuarison of two methods of inferior alveolar nerve block. J Dent 16:96, 1988 12. Sato K: The closed mouth intraoral technique of achieving mandibular anesthesia. Honolulu. HI, Saint Francis Hospital, July 28, 1982 (abstr) 13. Kaufman E, Weinstein P, Milgrom P: Difficulties in achieving local anesthesia. J Am Dent Assoc 108:205, 1984
J Oral Maxillofac 49:909-909,
14. Milgrom P, Weinstein P, Kuafman E: Student difficulties in achieving local anesthesia. J Dent Educ 48:168, 1984 15. Sisk AL: Evaluation of the Gow-Gates mandibular block for oral surgery. Anesth Prog 32:143, 1985 16. Sexton R, Howkins M: Trouble shooting in local anesthesia: Gow-Gates mandibular block. Ont Dent 62:20, 1985 17. Yamada A, Jasstak JT: Clinical evaluation of the Gow-Gates block in children. Anesth Prog 28: 106, 1981 18. Bennett CR: Monheim’s Local Anesthesia and Pain Control in Dental Practice (ed 7). St Louis, MO, Mosby, 1984, pp 99-113 19. Hetson G, Share J, Frommer J, et al: Statistical evaluation of the position of the mandibular foramen. Oral Surg 65:32, 1988 20. Waikakul A, Punwutikom J: Extra-intraoral landmarks technique for inferior alveolar nerve block. J Oral Maxillofac Surg (in press) 2 1. Rood JP: Some anatomical and physiological causes of failure to achieve mandibular analgesia. Br J Oral Surg 15:75, 1977 22. Malamed SF: The periodontal ligament (PDL) injection: An alternative to inferior alveolar nerve block. Oral Surg 53: 117, 1982 23. Rood JP: The analgesia and innervation of mandibular teeth. Br Dent J 140:237, 1976
Surg
1991
Discussion A Comparative Study of the Extra-intraoral Landmark Technique and the Direct Technique for Inferior Alveolar Nerve Block Stanley F. Malamed,
DDS
University of Southern California School of Dentistry, Los Angeles
Providing clinically adequate pain control in the mandible has proved to be a problem vexing dentists throughout the world for as long as dentistry has existed as a profession. The classic inferior alveolar nerve block, originally described by Fischer in 1919 and modified over the ensuing years by others, has long been considered the conventional technique for obtaining mandibular anesthesia. It was not until 1973, with the publication by GowGates’ of a new approach to mandibular anesthesia, that dentistry began to seriously consider alternatives to the conventional approach. Though not employed by all dentists, what is known as the Gow-Gates mandibular block has gained a significant foothold in the armamentarium of pain control techniques in the mandible. In an as yet unpublished survey of over 3,000 dentists,2 approximately 95% had heard of this technique, with 73% employing it, to some extent, in their practice. Success reported with the Gow-Gates technique has varied from somewhat less than the conventional3 to considerably more.4 The GowGates technique takes into account the fact that the most oft-stated reason for failure to achieve adequate mandibular anesthesia is deposition of the solution inferior to the
mandibular foramen, the site at which the inferior alveolar nerve enters the mandibular canal and becomes insulated from the anesthetic solution. Depositing anesthetic at the neck of the condyloid process in the Gow-Gates technique provides more ready access to V-3 and, with clinical experience, a greater rate of clinically adequate anesthesia than that provided by the conventional technique. Probably the most important result arising from publication of the Gow-Gates mandibular block technique is that it made dentists think about possible alternative approaches to achieving mandibular anesthesia. Several years later another approach to mandibular anesthesia appeared-one that purported to provide successful anesthesia in situations in which the patient was unable (as a result of trismus or mandibular fracture) to open their mouth.’ The Akinosi closed-mouth mandibular block technique is employed by 5% of dentists surveyed’ and usually as a secondary technique to either the conventional or Gow-Gates blocks. A significant benefit of the Akinosi technique is that it provides anesthesia of the motor as well as the sensory components of V-3, thereby providing relief from trismus, permitting the dentist to more easily manage the patient’s dental complaints. Because bone is not contacted in the Akinosi technique, its success rate has been found to be somewhat lower than either the conventional or Gow-Gates blocks. However, neither the Gow-Gates nor conventional inferior alveolar nerve blocks can even be attempted when patients are unable to open their mouth. The incisive (mental) nerve block is another technique that is of importance to dentistry. Profound anesthesia of the premolars, canine, and incisors can be achieved consistently (295%) with this injection technique, which is
