Comfort and effectiveness of the AMSA nerve block.

Introduction

Dental practitioners have the challenge of providing dental care with a minimum amount of discomfort and anxiety for their patients. The science of pain control has continued to evolve since the introduction of local anesthesia into dentistry. The dental profession is continually exploring new methods to help meet the challenges faced by dental care providers. The anterior middle superior alveolar (AMSA) nerve block is a relatively new technique that allows for widespread maxillary anesthesia with a single injection. Traditional methods of anesthetizing maxillary teeth include supraperiosteal infiltration over a specific targeted tooth or nerve block injections including the Posterior Superior Alveolar (PSA), the Middle Superior Alveolar (MSA) or the Infraorbital (IO). Lingual soft tissue can be anesthetized using the Greater Palatine (GP) or the Nasal Palatine (NP) nerve block injections. (1) Each of these techniques requires multiple punctures and adequate anesthetic volume to anesthetize more than a single tooth. These injections are typically administered using a manual aspirating syringe.

The AMSA technique uses a computer-controlled local anesthetic delivery system (CCLADS). This site-specific injection targets the neurovascular bundles located on the hard palate and provides pulpal anesthesia from the buccal root of the first molar through the central incisor by blocking impulses to the ASA and MSA nerves. Buccal gingival and palatal gingival tissues adjacent to the anesthetized teeth are also anesthetized (Figures 1 and 2). (2)

Several advantages of the AMSA have been identified. The palatal approach avoids sensory fibers of the face and lip, which allows for pulpal anesthesia without the loss of sensation typically associated with the ASA, MSA and IO techniques. Smaller anesthetic volumes are used to achieve profound pulpal anesthesia with a single injection. (2) Discomfort associated with a traditional palatal injection is minimized or eliminated due to the use of the CCLADS. (3)

Currently, there are two brands of CCLADS on the market: the Wand[TM] by Milestone Scientific and Comfort Control[TM] Syringe by Dentsply Professional. The Wand uses a foot-control to operate, and the Comfort Control Syringe uses a handpiece. The computer allows for a combination of an anesthetic pathway and a controlled flow rate of anesthesia. An anesthetic pathway is defined as an anesthetic drip that precedes the needle. The flow rate is the pressure and volume of the anesthetic solution. The use of a CCLADS often reduces or eliminates the discomfort associated with an oral injection. (4) A study conducted by Loomer and Perry compared traditional syringe-delivered injections to computer-controlled injections. Their findings showed a significant decrease in perceived pain when the AMSA technique was used, compared to the traditional GP and NP injections. (3)

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Study

Senior dental hygiene students enrolled in the University of South Dakota Dental Hygiene program participated in a research project that evaluated the students' perception of the comfort and effectiveness of the AMSA nerve block. Student participants administered local anesthesia to adult males in need of extensive scaling and/or root planing in the premolar and incisor areas. Random selection determined which of two injection techniques would be used. Students administered either the AMSA injection or the traditional ASA, MSA and NP nerve blocks. Dental hygiene treatment was then completed in the anesthetized area. At a subsequent appointment, the contra-lateral side would be anesthetized using the alternative technique.

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A Dentsply Comfort-Control[TM] Syringe with a 30-gauge extra-short needle was used for the AMSA injection. A traditional aspirating syringe with a 27-gauge short needle was used for the ASA, MSA and NP injections.

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Student participants completed a two-part survey following the dental hygiene appointment. The first part assessed ease of administration, perception of patient comfort during the injection and ease of preparation of armamentarium (Figure 3). Part two assessed the operator's perception of patient comfort for each tooth scaled (Figure 4). A scale of one to three was used. A rating of one indicates that preparation and administration was easy and patient comfort was comfortable. A rating of three indicates that preparation and administration was difficult and patient comfort was uncomfortable.

The surveys showed that the operators felt the AMSA technique was more comfortable for the patient receiving the injection and anesthesia obtained was as effective as the traditional injections. Ease of administration with the CCLADS compared favorably with the traditional technique. However, students felt that preparation of the traditional syringe was easier than the CCLADS.

AMSA Technique

The technique used for this study is similar to that described by Malamed (1) and Friedman and Hochman. (2)

1. Armamentarium is set up according to manufacturer's recommendation using a 30-gauge extra-short needle.

2. The injection site is located midpoint on an imaginary line starting at the mid-palatal suture and terminating at the free gingival margin between the first and second premolars. (This midpoint is located where the palate meets the alveolar ridge) (Figure 5).

3. Topical anesthesia is applied initially to the injection site. Pressure anesthesia may be applied with a cotton tip applicator for 30 seconds. The CCLADS is activated as the needle is placed at a 45-degree angle to the palate and slowly advanced until bone is contacted (Figure 6). The anesthetic pathway, along with pressure anesthesia, allows for greater patient comfort.

4. Following negative aspiration, 0.6 - 0.9 ml of anesthetic solution is deposited in 60 to 90 seconds.

5. Pressure is released and the needle is carefully withdrawn.

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This injection should be administered at the slowest setting on the computer-controlled device. Too rapid an injection rate could result in patient discomfort and/or excessive tissue blanching. If either of these signs is observed, the CCLADS can be temporarily suspended until excess anesthetic solution dissipates into surrounding tissues. The use of anesthetics with less than 4% concentration is recommended. (5)

Conclusion

Students found that they were more comfortable administering AMSA than the traditional GP and NP injections. This technique also eliminated the need for the additional ASA and MSA injections. Student participants felt that the patient was more comfortable with the AMSA as compared to the traditional palatal injection. Student perception of anesthesia attained was comparable to that associated with the traditional method. With AMSA, the patient receives significantly less local anesthetic and experiences a more comfortable palatal injection.

References

(1.) Malamed S: Handbook of local anesthesia. 5th ed. St. Louis: Mosby; 2004: 15.

(2.) Friedman MJ, Hochman MN: The AMSA injection: a new concept for local anesthesia of the maxillary teeth using a computer-controlled injection system. Quintessence Int 1998; 29: 297-303.

(3.) Loomer PM, Perry DA. Computer-controlled delivery versus syringe delivery of local anesthetic injections for therapeutic scaling and root planing. J Am Dent Assoc 2004; 135: 358-65.

(4.) The Wand computer controlled anesthesia delivery system (February 1998 revision) Livingston, N.J.: Milestone Scientific.

(5.) Nicholson JW, Berry TG, Summitt JB, et al.: Pain perception and utility: a comparison of the syringe and computerized local injection techniques. Gen Dent 2001; 49:167-73.

By Marti Pollard, RDH, MS; JoNell Bly, RDH, BS; and Robert F. Nelson, RDH, MPA 

Marti Pollard, RDH, MS, is associate professor at The University of South Dakota, School of Health Science, Department of Dental Hygiene.

JoNell Bly, RDH, BS, is instructor at The University of South Dakota, School of Health Science.

Robert Nelson RDH, MPA, is professor at The University of South Dakota, School of Health Science.