- Email: [email protected]
Real-time ultrasonographic visualization for guided inferior alveolar nerve injection
Vol. 115 No. 2 February 2013
Real-time ultrasonographic visualization for guided inferior alveolar nerve injection Brian Chanpong, DDS, MSc,a Raymond Tang, MSc, MD, FRCPC,b Andrew Sawka, MD, FRCPC,b Claudia Krebs, MD, PhD,c and Himat Vaghadia, MBBS, FRCPCb University of British Columbia, Vancouver, British Columbia, Canada
Objective. The purpose of this study was to develop a methodological technique for the ultrasonographic visualization of the inferior alveolar nerve (IAN) using a novel hockey stick–shaped 8- to 15-MHz transducer in volunteers, followed by simulated IAN scanning and injection in cadavers. Study Design. In 20 volunteers, bilateral scans of the IAN nerve were performed with a systematic technique. We recorded times to scan each side and sonographic visibility of the IAN. In 3 cadavers, bilateral scans of the IAN were performed, followed by simulated injection with dye. Results. The IAN was visible in all 40 scans. Mean scanning times were 19.6 seconds (range: 4-54 seconds) for the left side and 30.5 seconds (range: 6-116 seconds) for the right side. In 5 cadaver injections, dye was correctly deposited onto the IAN with the ultrasound technique. Conclusions. We hypothesize that ultrasound-guided IAN block may be feasible in humans using our technique. (Oral Surg Oral Med Oral Pathol Oral Radiol 2013;115:272-276)
The inferior alveolar nerve (IAN) block, also known as the mandibular nerve block, is essential for invasive dental procedures in the mandible, yet it often eludes dental practitioners. Studies measuring the success rate of the IAN block indicate variation depending on the local anesthetic agent used, the volume administered, and the scale used to measure success.1 The use of a single dental cartridge (1.8 mL) of 2% lidocaine has resulted in a complete block when measured by the electric pulp tester (EPT) up to 71% of the time.2,3 Infiltration of the mandibular buccal area adjacent to the first molar in addition to the IAN block has elevated the success rate as high as 91%.4 Few studies show success rates close to 100% when an EPT is used as a measure of success, however, partly because this block is done blindly, solely based on intraoral landmarks, with the confounding factor of anatomical variation.5 The use of ultrasonography has greatly improved the success of nerve blocks in medicine. In one study the IAN block using ultrasound was described but only the inferior alveolar artery was visible.6 Since that time, significant improvements to ultrasonography technology have oca
Clinical Assistant Professor, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, Canada. b Consultant Staff, Department of Anesthesiology, University of British Columbia, Vancouver, British Columbia, Canada. c Consultant Staff, Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada. Received for publication June 2, 2012; returned for revision Sept 7, 2012; accepted for publication Oct 24, 2012. © 2013 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.oooo.2012.10.019
272
curred. The purpose of the current study was to develop a technique to visualize the IAN in volunteers using a miniature ultrasound probe, followed by verification with cadaver-simulated IAN injection.
MATERIAL AND METHODS Volunteer phase After receiving ethics approval from the University of British Columbia, we recruited a convenient sample of 20 volunteers. An 8- to 15-MHz hockey stick–shaped transducer (HST15-8/20 linear probe) attached to a SonixTouch ultrasound machine (Ultrasonix, Richmond, British Columbia, Canada) was used to perform the scans, which were all done by 1 investigator (BC). The transducer was placed in a protective barrier that was filled with water, which acted as the conductive medium. Interincisal distance was measured and a bite block was placed to help maintain mouth opening during the scan. The probe was then placed axially along the occlusal mandibular surface against the pterygomandibular raphe and rotated transversely until the ramus was identified. From there, the investigator moved the probe cephalad until the IAN could be visualized by its fascicular appearance (Figure 1). Images of the IAN and inferior alveolar artery were captured and graded on a 3-point scale (0-2) based on their
Statement of Clinical Relevance This ultrasound-guided technique using a novel hockey stick probe may improve success rates for inferior alveolar nerve injection.
OOOO Volume 115, Number 2
ORIGINAL ARTICLE Chanpong et al. 273
Fig. 1. Ultrasound probe along the left ramus.
Mean (SD)
Fig. 2. Ultrasound of the inferior alveolar nerve. “A” indicates the ramus and the arrow indicates the inferior alveolar nerve.
31.9 years (⫾7.8) 71.7 kg (⫾13.8) 171.3 cm (⫾8.1) 45.6 mm (⫾6.8)
dissection was quite diffuse around the nerve. To more accurately localize the point of injection, 0.5 mL of blue viscous gel was injected on the third cadaver.
Table I. Summary of volunteer demographics Volunteer demographics (n ⫽ 20) Age Weight Height Interincisal distance
sonographic visibility (0, not visible; 1, equivocal; 2, clear visualization). Each volunteer was scanned bilaterally, producing a total of 40 scans, and scanning times were recorded per side. If volunteers were unable to complete the study, this was noted and these data were included in the analysis. All volunteers were then asked to fill out a simple questionnaire that rated the comfort of the probe compared with the bite block on a 10-point Likert scale anchored at 1 and 10 (1 being not comfortable at all to 10 being very comfortable). Cadaver phase Three unembalmed human cadavers were used for this phase of the study in the anatomy laboratory (University of British Columbia). For each cadaver, spandex lip retractors were used to maintain mouth opening and the same 8- to 15-MHz transducer was placed against the medial aspect of the mandibular ramus. Following the identification of the IAN, a 25-g, 40-mm needle on a 5-mL syringe was inserted toward the nerve under ultrasound guidance. With the needle tip adjacent to the nerve, 1 mL of dye was injected and the spread around the nerve was visualized by ultrasound. This procedure was repeated on the contralateral side on each cadaver. To confirm the correct placement of the dye, a blinded anatomist performed a layer-by-layer dissection to the IAN through the skin and the external facial muscles and across the mandibular ramus. Photographs were taken of the dissection and IAN. The injection was deemed successful if the IAN was stained. On the first 2 cadavers, green dye was injected but the spread upon
RESULTS Volunteer phase The demographics of the 20 volunteers (9 female, 11 male) are summarized in Table I. The IAN was easily visualized adjacent to the ramus, as seen in Figure 2. All volunteers completed the study and the IAN was visible in all 40 scans, whereas the inferior alveolar artery was visible in only 6 of 40 scans (Figure 3). The mean scanning time (⫾SD) was 19.6 ⫾ 14.2 seconds for the left side and 30.5 ⫾ 25.2 seconds for the right side (Table II). The subjective rating of the comfort of the intraoral ultrasound transducer did not differ from that of the bite block (P ⫽ 0.426). The mean subjective comfort score (⫾SD) was 7.5 ⫾ 2.1 for the transducer and 7.3 ⫾ 1.7 for the bite block (Table II). Cadaver phase The first cadaver was male with a weight of 86 kg and height of 178 cm; the second was female with a weight of 40 kg and height of 175 cm; and the third was female with a weight of 36 kg and height of 155 cm. In all cadavers, with the exception of the left side on the third cadaver, the IAN was identified bilaterally by ultrasonography and had the typical fascicular appearance of nerve tissue (Figure 4). The head on the third cadaver was in a position at death that did not allow for intraoral transducer placement on the left side. After dissection, all 4 IANs were stained with green dye (Figure 5). On the third cadaver, the blue viscous gel was adjacent to the IAN and in the same plane (Figure 6), confirming accurate ultrasonographic identification of the nerve and successful injection.
ORAL AND MAXILLOFACIAL RADIOLOGY 274 Chanpong et al.
OOOO February 2013
Fig. 3. Visibility of the inferior alveolar nerve and inferior alveolar artery: 0, not visible; 1, equivocal; 2, clearly visible.
Table II. Summary of scanning times and comfort of ultrasound probe and bite block Mean (SD) Scan time right Scan time left Bite block comfort Ultrasound probe comfort
30.5 s (⫾25.2) 19.6 s (⫾14.2) 7.3 (⫾1.7) 7.5 (⫾2.1)
DISCUSSION Ultrasonography has become routine when administering peripheral nerve blocks and has been shown to reduce the performance time, needle passes, and onset of block.7 Ultrasound has been utilized for IAN block by Hannan et al.6 with no significant improvement in success compared with a traditional landmarking technique. However, the IAN was not actually visualized and instead the inferior alveolar artery was used as a surrogate marker of nerve location. Since the Hannan et al. study,6 there have been significant improvements in ultrasonographic technology and image processing such that the nerve tissue is more readily visualized.
The image resolution has increased in the transducers and the processors can better distinguish small differences in tissue density. We were successful in visualizing the IAN in all volunteers without any difficulty and subsequently successful in placing injectate on the same nerve in human cadavers using ultrasonography. In addition, the probe proved to be as comfortable as the bite block, which is commonly used in dentistry. The mean distance (⫾SD) from buccal mucosa to the IAN, measured on ultrasound, was found to be 19.7 ⫾ 2.4 mm on the right and 20.2 ⫾ 2.1 mm on the left. This correlates with previous findings by Kronman et al., which showed that the average distance to the IAN was 21.96 ⫾ 1.81 mm.8 Similar to other nerve tissue, the IAN has a fascicular appearance on ultrasound and can be followed along its course until it enters the mandibular foramen. In contrast to the study by Hannan et al.,6 we were unable to identify the inferior alveolar artery in almost all of our scans, which may be caused by compression of the vessel from the transducer pressure.
OOOO Volume 115, Number 2
ORIGINAL ARTICLE Chanpong et al. 275
Fig. 4. Cadaver ultrasound (A) preinjection and (B) postinjection.
Fig. 5. Cadaver with green dye staining the inferior alveolar nerve (external view of the right side of the mandible). “A” indicates superior and “B” indicates inferior aspects of the cadaver.
Fig. 6. Cadaver with blue gel in the same plane as the inferior alveolar nerve (external view of the right side of the mandible). “A” indicates superior and “B” indicates inferior aspects of the cadaver. Arrow indicates the inferior alveolar nerve.
With ultrasonography, the needle may be followed such that the tip can be placed adjacent to the nerve. In the cadavers, the injectate was visualized by ultrasound and in all 5 injections there was a hypoechoic expansion of the surrounding tissue around the nerve. Potentially, if a poor distribution of injectate was seen, the needle could be redirected under ultrasound guidance so that the local anesthetic is adjacent to the nerve. Similar to peripheral nerve blocks, real-time ultra-
sound-guided insertion of the needle may help avoid inadvertent intraneural injection and entry into surrounding structures, including vessels, and reduce the number of injections. The injection of 1 mL of green dye under ultrasound guidance stained the IAN, which would mimic the spread seen with the local anesthetic with an actual IAN block because of similar volumes. However, because of the spread in the tissues around the nerve, the exact
ORAL AND MAXILLOFACIAL RADIOLOGY 276 Chanpong et al.
point of injection could not be determined definitively. Therefore, injection of 0.5 mL of blue viscous gel followed by immediate dissection was performed and the gel was localized in the same plane as the IAN, immediately adjacent to the nerve, which confirms the sonographic identification of the IAN.
CONCLUSIONS The IAN block has reported failure rates as high as 62%.3 Anatomical variation and blind needle placement all contribute to the high failure rate of the mandibular block.9,10 Therefore, the introduction of a realtime ultrasound-guided approach to the IAN may reduce the block failures caused by anatomic variability and maldistribution of local anesthetic. This study indicates that an ultrasound-guided IAN block may be feasible in patients, but more clinical studies must be performed to determine whether there is a reduction in block failures and inadvertent vascular punctures. Moreover, it would be of greater interest to determine whether there is a faster onset of sensory block and a dose reduction, as has been seen with ultrasound-guided peripheral nerve blocks compared with traditional techniques used elsewhere in the body. REFERENCES 1. Brandt RG, Anderson PF, McDonald NJ, Sohn W, Peters MC. The pulpal anesthetic efficacy of articaine versus lidocaine in dentistry: a meta-analysis. J Am Dent Assoc 2011;142:493-504.
OOOO February 2013 2. Agren E, Danielsson K. Conduction block analgesia in the mandible. A comparative investigation of the techniques of Fischer and Gow-Gates. Swed Dent J 1981;5:81-9. 3. Montagnese TA, Reader A, Melfi R. A comparative study of the Gow-Gates technique and a standard technique for mandibular anesthesia. J Endod 1984;10:158-63. 4. Kanaa MD, Whitworth JM, Corbett IP, Meechan JG. Articaine buccal infiltration enhances the effectiveness of lidocaine inferior alveolar nerve block. Int Endod J 2009;42:238-46. 5. Blanton PL, Jeske AH. Misconceptions involving dental local anesthesia. Part 1: anatomy. Tex Dent J 2002;119:296-300, 302-4, 306-7. 6. Hannan L, Reader A, Nist R, Beck M, Meyers WJ. The use of ultrasound for guiding needle placement for inferior alveolar nerve blocks. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:658-65. 7. Liu SS, Ngeow JE, YaDeau JT. Ultrasound-guided regional anesthesia and analgesia: a qualitative systematic review. Reg Anesth Pain Med 2009;34:47-59. 8. Kronman JH, El-Bermani AW, Wongwatana S, Kumar A. Preferred needle lengths for inferior alveolar anesthesia. Gen Dent 1994;42:74-6. 9. Nicholson ML. A study of the position of the mandibular foramen in the adult human mandible. Anat Rec 1985;212:110-2. 10. Todorovic´ L, Stajcic´ Z, Petrovic´ V. Mandibular versus inferior dental anaesthesia: clinical assessment of 3 different techniques. Int J Oral Maxillofac Surg 1986;15:733-8. Reprint requests: Dr. Brian Chanpong Suite 806-750 West Broadway Vancouver, V5Z 1H8 British Columbia, Canada. [email protected]
Real-time ultrasonographic visualization for guided inferior alveolar nerve injection Brian Chanpong, DDS, MSc,a Raymond Tang, MSc, MD, FRCPC,b Andrew Sawka, MD, FRCPC,b Claudia Krebs, MD, PhD,c and Himat Vaghadia, MBBS, FRCPCb University of British Columbia, Vancouver, British Columbia, Canada
Objective. The purpose of this study was to develop a methodological technique for the ultrasonographic visualization of the inferior alveolar nerve (IAN) using a novel hockey stick–shaped 8- to 15-MHz transducer in volunteers, followed by simulated IAN scanning and injection in cadavers. Study Design. In 20 volunteers, bilateral scans of the IAN nerve were performed with a systematic technique. We recorded times to scan each side and sonographic visibility of the IAN. In 3 cadavers, bilateral scans of the IAN were performed, followed by simulated injection with dye. Results. The IAN was visible in all 40 scans. Mean scanning times were 19.6 seconds (range: 4-54 seconds) for the left side and 30.5 seconds (range: 6-116 seconds) for the right side. In 5 cadaver injections, dye was correctly deposited onto the IAN with the ultrasound technique. Conclusions. We hypothesize that ultrasound-guided IAN block may be feasible in humans using our technique. (Oral Surg Oral Med Oral Pathol Oral Radiol 2013;115:272-276)
The inferior alveolar nerve (IAN) block, also known as the mandibular nerve block, is essential for invasive dental procedures in the mandible, yet it often eludes dental practitioners. Studies measuring the success rate of the IAN block indicate variation depending on the local anesthetic agent used, the volume administered, and the scale used to measure success.1 The use of a single dental cartridge (1.8 mL) of 2% lidocaine has resulted in a complete block when measured by the electric pulp tester (EPT) up to 71% of the time.2,3 Infiltration of the mandibular buccal area adjacent to the first molar in addition to the IAN block has elevated the success rate as high as 91%.4 Few studies show success rates close to 100% when an EPT is used as a measure of success, however, partly because this block is done blindly, solely based on intraoral landmarks, with the confounding factor of anatomical variation.5 The use of ultrasonography has greatly improved the success of nerve blocks in medicine. In one study the IAN block using ultrasound was described but only the inferior alveolar artery was visible.6 Since that time, significant improvements to ultrasonography technology have oca
Clinical Assistant Professor, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, Canada. b Consultant Staff, Department of Anesthesiology, University of British Columbia, Vancouver, British Columbia, Canada. c Consultant Staff, Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada. Received for publication June 2, 2012; returned for revision Sept 7, 2012; accepted for publication Oct 24, 2012. © 2013 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.oooo.2012.10.019
272
curred. The purpose of the current study was to develop a technique to visualize the IAN in volunteers using a miniature ultrasound probe, followed by verification with cadaver-simulated IAN injection.
MATERIAL AND METHODS Volunteer phase After receiving ethics approval from the University of British Columbia, we recruited a convenient sample of 20 volunteers. An 8- to 15-MHz hockey stick–shaped transducer (HST15-8/20 linear probe) attached to a SonixTouch ultrasound machine (Ultrasonix, Richmond, British Columbia, Canada) was used to perform the scans, which were all done by 1 investigator (BC). The transducer was placed in a protective barrier that was filled with water, which acted as the conductive medium. Interincisal distance was measured and a bite block was placed to help maintain mouth opening during the scan. The probe was then placed axially along the occlusal mandibular surface against the pterygomandibular raphe and rotated transversely until the ramus was identified. From there, the investigator moved the probe cephalad until the IAN could be visualized by its fascicular appearance (Figure 1). Images of the IAN and inferior alveolar artery were captured and graded on a 3-point scale (0-2) based on their
Statement of Clinical Relevance This ultrasound-guided technique using a novel hockey stick probe may improve success rates for inferior alveolar nerve injection.
OOOO Volume 115, Number 2
ORIGINAL ARTICLE Chanpong et al. 273
Fig. 1. Ultrasound probe along the left ramus.
Mean (SD)
Fig. 2. Ultrasound of the inferior alveolar nerve. “A” indicates the ramus and the arrow indicates the inferior alveolar nerve.
31.9 years (⫾7.8) 71.7 kg (⫾13.8) 171.3 cm (⫾8.1) 45.6 mm (⫾6.8)
dissection was quite diffuse around the nerve. To more accurately localize the point of injection, 0.5 mL of blue viscous gel was injected on the third cadaver.
Table I. Summary of volunteer demographics Volunteer demographics (n ⫽ 20) Age Weight Height Interincisal distance
sonographic visibility (0, not visible; 1, equivocal; 2, clear visualization). Each volunteer was scanned bilaterally, producing a total of 40 scans, and scanning times were recorded per side. If volunteers were unable to complete the study, this was noted and these data were included in the analysis. All volunteers were then asked to fill out a simple questionnaire that rated the comfort of the probe compared with the bite block on a 10-point Likert scale anchored at 1 and 10 (1 being not comfortable at all to 10 being very comfortable). Cadaver phase Three unembalmed human cadavers were used for this phase of the study in the anatomy laboratory (University of British Columbia). For each cadaver, spandex lip retractors were used to maintain mouth opening and the same 8- to 15-MHz transducer was placed against the medial aspect of the mandibular ramus. Following the identification of the IAN, a 25-g, 40-mm needle on a 5-mL syringe was inserted toward the nerve under ultrasound guidance. With the needle tip adjacent to the nerve, 1 mL of dye was injected and the spread around the nerve was visualized by ultrasound. This procedure was repeated on the contralateral side on each cadaver. To confirm the correct placement of the dye, a blinded anatomist performed a layer-by-layer dissection to the IAN through the skin and the external facial muscles and across the mandibular ramus. Photographs were taken of the dissection and IAN. The injection was deemed successful if the IAN was stained. On the first 2 cadavers, green dye was injected but the spread upon
RESULTS Volunteer phase The demographics of the 20 volunteers (9 female, 11 male) are summarized in Table I. The IAN was easily visualized adjacent to the ramus, as seen in Figure 2. All volunteers completed the study and the IAN was visible in all 40 scans, whereas the inferior alveolar artery was visible in only 6 of 40 scans (Figure 3). The mean scanning time (⫾SD) was 19.6 ⫾ 14.2 seconds for the left side and 30.5 ⫾ 25.2 seconds for the right side (Table II). The subjective rating of the comfort of the intraoral ultrasound transducer did not differ from that of the bite block (P ⫽ 0.426). The mean subjective comfort score (⫾SD) was 7.5 ⫾ 2.1 for the transducer and 7.3 ⫾ 1.7 for the bite block (Table II). Cadaver phase The first cadaver was male with a weight of 86 kg and height of 178 cm; the second was female with a weight of 40 kg and height of 175 cm; and the third was female with a weight of 36 kg and height of 155 cm. In all cadavers, with the exception of the left side on the third cadaver, the IAN was identified bilaterally by ultrasonography and had the typical fascicular appearance of nerve tissue (Figure 4). The head on the third cadaver was in a position at death that did not allow for intraoral transducer placement on the left side. After dissection, all 4 IANs were stained with green dye (Figure 5). On the third cadaver, the blue viscous gel was adjacent to the IAN and in the same plane (Figure 6), confirming accurate ultrasonographic identification of the nerve and successful injection.
ORAL AND MAXILLOFACIAL RADIOLOGY 274 Chanpong et al.
OOOO February 2013
Fig. 3. Visibility of the inferior alveolar nerve and inferior alveolar artery: 0, not visible; 1, equivocal; 2, clearly visible.
Table II. Summary of scanning times and comfort of ultrasound probe and bite block Mean (SD) Scan time right Scan time left Bite block comfort Ultrasound probe comfort
30.5 s (⫾25.2) 19.6 s (⫾14.2) 7.3 (⫾1.7) 7.5 (⫾2.1)
DISCUSSION Ultrasonography has become routine when administering peripheral nerve blocks and has been shown to reduce the performance time, needle passes, and onset of block.7 Ultrasound has been utilized for IAN block by Hannan et al.6 with no significant improvement in success compared with a traditional landmarking technique. However, the IAN was not actually visualized and instead the inferior alveolar artery was used as a surrogate marker of nerve location. Since the Hannan et al. study,6 there have been significant improvements in ultrasonographic technology and image processing such that the nerve tissue is more readily visualized.
The image resolution has increased in the transducers and the processors can better distinguish small differences in tissue density. We were successful in visualizing the IAN in all volunteers without any difficulty and subsequently successful in placing injectate on the same nerve in human cadavers using ultrasonography. In addition, the probe proved to be as comfortable as the bite block, which is commonly used in dentistry. The mean distance (⫾SD) from buccal mucosa to the IAN, measured on ultrasound, was found to be 19.7 ⫾ 2.4 mm on the right and 20.2 ⫾ 2.1 mm on the left. This correlates with previous findings by Kronman et al., which showed that the average distance to the IAN was 21.96 ⫾ 1.81 mm.8 Similar to other nerve tissue, the IAN has a fascicular appearance on ultrasound and can be followed along its course until it enters the mandibular foramen. In contrast to the study by Hannan et al.,6 we were unable to identify the inferior alveolar artery in almost all of our scans, which may be caused by compression of the vessel from the transducer pressure.
OOOO Volume 115, Number 2
ORIGINAL ARTICLE Chanpong et al. 275
Fig. 4. Cadaver ultrasound (A) preinjection and (B) postinjection.
Fig. 5. Cadaver with green dye staining the inferior alveolar nerve (external view of the right side of the mandible). “A” indicates superior and “B” indicates inferior aspects of the cadaver.
Fig. 6. Cadaver with blue gel in the same plane as the inferior alveolar nerve (external view of the right side of the mandible). “A” indicates superior and “B” indicates inferior aspects of the cadaver. Arrow indicates the inferior alveolar nerve.
With ultrasonography, the needle may be followed such that the tip can be placed adjacent to the nerve. In the cadavers, the injectate was visualized by ultrasound and in all 5 injections there was a hypoechoic expansion of the surrounding tissue around the nerve. Potentially, if a poor distribution of injectate was seen, the needle could be redirected under ultrasound guidance so that the local anesthetic is adjacent to the nerve. Similar to peripheral nerve blocks, real-time ultra-
sound-guided insertion of the needle may help avoid inadvertent intraneural injection and entry into surrounding structures, including vessels, and reduce the number of injections. The injection of 1 mL of green dye under ultrasound guidance stained the IAN, which would mimic the spread seen with the local anesthetic with an actual IAN block because of similar volumes. However, because of the spread in the tissues around the nerve, the exact
ORAL AND MAXILLOFACIAL RADIOLOGY 276 Chanpong et al.
point of injection could not be determined definitively. Therefore, injection of 0.5 mL of blue viscous gel followed by immediate dissection was performed and the gel was localized in the same plane as the IAN, immediately adjacent to the nerve, which confirms the sonographic identification of the IAN.
CONCLUSIONS The IAN block has reported failure rates as high as 62%.3 Anatomical variation and blind needle placement all contribute to the high failure rate of the mandibular block.9,10 Therefore, the introduction of a realtime ultrasound-guided approach to the IAN may reduce the block failures caused by anatomic variability and maldistribution of local anesthetic. This study indicates that an ultrasound-guided IAN block may be feasible in patients, but more clinical studies must be performed to determine whether there is a reduction in block failures and inadvertent vascular punctures. Moreover, it would be of greater interest to determine whether there is a faster onset of sensory block and a dose reduction, as has been seen with ultrasound-guided peripheral nerve blocks compared with traditional techniques used elsewhere in the body. REFERENCES 1. Brandt RG, Anderson PF, McDonald NJ, Sohn W, Peters MC. The pulpal anesthetic efficacy of articaine versus lidocaine in dentistry: a meta-analysis. J Am Dent Assoc 2011;142:493-504.
OOOO February 2013 2. Agren E, Danielsson K. Conduction block analgesia in the mandible. A comparative investigation of the techniques of Fischer and Gow-Gates. Swed Dent J 1981;5:81-9. 3. Montagnese TA, Reader A, Melfi R. A comparative study of the Gow-Gates technique and a standard technique for mandibular anesthesia. J Endod 1984;10:158-63. 4. Kanaa MD, Whitworth JM, Corbett IP, Meechan JG. Articaine buccal infiltration enhances the effectiveness of lidocaine inferior alveolar nerve block. Int Endod J 2009;42:238-46. 5. Blanton PL, Jeske AH. Misconceptions involving dental local anesthesia. Part 1: anatomy. Tex Dent J 2002;119:296-300, 302-4, 306-7. 6. Hannan L, Reader A, Nist R, Beck M, Meyers WJ. The use of ultrasound for guiding needle placement for inferior alveolar nerve blocks. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:658-65. 7. Liu SS, Ngeow JE, YaDeau JT. Ultrasound-guided regional anesthesia and analgesia: a qualitative systematic review. Reg Anesth Pain Med 2009;34:47-59. 8. Kronman JH, El-Bermani AW, Wongwatana S, Kumar A. Preferred needle lengths for inferior alveolar anesthesia. Gen Dent 1994;42:74-6. 9. Nicholson ML. A study of the position of the mandibular foramen in the adult human mandible. Anat Rec 1985;212:110-2. 10. Todorovic´ L, Stajcic´ Z, Petrovic´ V. Mandibular versus inferior dental anaesthesia: clinical assessment of 3 different techniques. Int J Oral Maxillofac Surg 1986;15:733-8. Reprint requests: Dr. Brian Chanpong Suite 806-750 West Broadway Vancouver, V5Z 1H8 British Columbia, Canada. [email protected]