Update Your Approach to Local Anesthesia

Editor’s Note: Due to the nature of this ­perspective piece, the following content has not been subject to peer review.

Oftentimes, fear of the dentist stems from anticipation of pain associated with local anesthesia administration. While oral health professionals can ease this type of dental phobia by remaining current on injection techniques and technologies, how many do so?

After a presentation for the Pacific Northwest Dental Conference in Seattle, Jeffrey Parrish, DDS, a columnist for the Washington State Dental Association (WSDA) News contacted us to clarify key points on research related to computer-controlled local anesthesia device (CCLAD) training (see sidebar).¹ This discussion led to Parrish’s subsequent editorial in the WSDA News, “Old Dogs Can Learn New Tricks … But Puppies Get Set in Their Ways Early On.” The column stimulated some questions related to local anesthesia practice. In light of evidence-based decision making and advancing science, what drives clinicians’ local anesthesia choices in daily practice? Are practitioners clinging to dogma learned early on as creatures of habit, and/or are they resisting the potential risks and discomfort of change, including the time it takes to learn new skills?^2,3

An example of resistance, most early learners are taught a modified Halsted inferior alveolar nerve block technique that has a success rate reportedly as low as 19% (in the presence of pulpitis), and as high as 80% to 85%.⁴ Gow-Gates nerve blocks, on the other hand, demonstrated a success rate of ~97%, according to a 1981 study by Malamed⁵ — which begs the question: Why are inferior alveolar nerve blocks so much more popular than Gow-Gates blocks?

According to J. Mel Hawkins, DDS, an internationally regarded dentist anesthesiologist, “Local anesthesia is still a dentist’s, dental hygienist’s and patient’s primary functional relationship.”⁶ Popular press and social media cite fear of the dentist (including fear of pain from needles) as one of the primary reasons people dislike and may avoid seeing the dentist. This assumption should motivate clinicians to be highly skilled in providing pain-free dentistry, with a particular focus on patients’ emotional well-being. Local anesthesia delivery is not solely dependent on devices and other components of the pain management armamentarium, as these cannot replace compassion, empathy and encouragement.

SLOW TO ADOPT NEW IDEAS

A report in the 2014 Annual Review of Public Health estimates that worthwhile medical ideas backed by credible research take nearly 17 years to be integrated into routine practice — that’s nearly half the length of many careers.⁷ While demonstrating a cautious approach, this slow adoption of positive change is not likely to benefit patients. Do old dogs continue on, changing only when evidence is overwhelming and they finally decide to take a class or seminar on a new technique?¹ And if that fails at first, is it back to the old ways?

While clinicians are, for the most part, proactive in integrating credible developments into practice, when it comes to local anesthesia administration, some providers are reluctant to try new approaches and devices — even if they are not particularly new to others.

Following the acquisition of basic local anesthesia skill sets, some view these as the sum total of what they will ever need to know, rather than a foundation for further development. Basic skill sets become dogma, and while they are excellent when establishing authoritative guidelines for safe and generally effective clinical results, they can preclude optimal flexibility and success when anatomy, physiology or dental phobias interfere. As clinicians progress through their careers, they acquire clinical practice experiences and lifelong learning opportunities, they participate in webinars and watch online videos, they read peer-reviewed papers, and they talk with fellow clinicians in order to enrich their early dogma. When new information suggests modification is required, earlier approaches are often retired.

For example, many believe 30-gauge needles cause less injection pain than 27- and 25-gauge needles because they are smaller. This has not been demonstrated to be true. While it is conceivable small-bore needle insertions might be slightly more comfortable than large-bore needle insertions, research indicates there is no difference in pain perception. The perception of pain from needles passing through mucosa may include insertion and penetration, as well as fluid bursting during deposition. This can be further explained by the physics of injection hydraulics.^8,9 A fast stream from a small-bore needle — under the same manual pressure as a large-bore needle — results in greater pressure exerted on tissues. This might help explain the lack of perceived differences in pain. Research by Kudo¹⁰ found that patients could feel the initial bursting of fluid at needle tips with greater injection pressures (similar to what happens when a nozzle is screwed onto a hose).

Using skills and techniques that are learned and mastered first is a comfortable approach. However, anticipation of an improved patient experience and clinical success by embracing alternative techniques and technologies provides excellent motivation for trying new approaches.¹¹ The following discussion presents selected examples of local anesthesia techniques that are worth exploring.

ANATOMY AND TECHNIQUES^3,12,13

Anatomy hasn’t changed significantly since ancient Roman anatomists described human structures in detail. Local anesthesia techniques for anesthetizing the oral cavity, on the other hand, are relatively new. The Halsted technique — which is the basis for the most common approach to providing inferior alveolar anesthesia — is only slightly more than 100 years old.

A recently discussed approach to providing inferior alveolar anesthesia makes use of specific periodontal ligament injections.⁴ While currently taught at only a handful of institutions, it has the potential to provide inferior alveolar anesthesia when the Halsted and Gow-Gates blocks both fail to provide it. Intraosseus techniques have been found to be effective as a primary means of achieving local anesthesia, rather than being considered only as rescue approaches. Another technique in more widespread use (but currently taught at few institutions) was first described in 1979 by Menke and Gowgiel¹³ — the short-needle inferior alveolar nerve block. Specific guidelines are recommended to address issues of safety when performing this technique. Many practitioners find it to be an excellent alternative to a traditional inferior alveolar block and relatively easy to adopt.

The technique of buffering anesthetic solutions can reduce pain and decrease onset time. A higher concentration of neutral base molecules is available at nerve membranes in buffered solutions, and this increases the number of anesthetic molecules diffusing into the nerves. It also reduces onset times for profound anesthesia, which benefits both providers and patients.

PHARMACOLOGY¹²

Lidocaine has been available in dental cartridges for more than 70 years and its record of safety and efficacy has established it as the gold standard for all dental local anesthetics introduced in the ensuing years. Compared to lidocaine, articaine — the most recently approved drug — offers several advantages, including a metabolic pathway that prevents most of the drug from reaching the liver. In addition, it provides a much shorter half-life, a longer duration in some instances, a more rapid onset in infiltrations, and a greater effectiveness in mandibular infiltrations.

ADJUNCTIVE ANESTHESIA DEVICES^8,9,12

Available devices can mitigate pain experiences and boost the confidence of both clinicians and patients. Whether the goal is cognitive distraction, gate-control (i.e., physical) distraction, or a true enhancement to injection technique, the net gain is positive.

Numerous adjunctive devices are designed to minimize needle insertion pain, often based on gate-control influences. These devices can be of great value to any clinician who experiences a reduction in patient fear and improved perceptions of pain-free local anesthesia delivery. Considered to be gadgets by many, if they have a positive impact on the patient experience, they can be effective adjuncts. One example is a relatively simple device that facilitates a needleless periodontal ligament injection by means of a specialized insertion guide or “atraumatic tip” that shields the needle. This relatively simple modification offers highly beneficial outcomes. Based on the gate control theory, another device, which attaches to any standard syringe, vibrates the needle during an injection to reduce the perception of pain.

At the more complex end of the spectrum, Hochman and Friedman, pioneers in CCLAD technology, identified the benefits of controlled injection flow rates to improved patient comfort. As noted, Kudo¹⁰ reported patients can experience pain when injections are initiated from the bursting of fluids at needle tips due to rapid injection rates. With manual syringes, flow rates can fluctuate greatly from one clinician to another, with pressures notably higher in larger hands. Thus, proponents cite CCLAD technology’s benefits for both patients and practitioners. In addition to reliably controlling flow rates specific to the nature of tissues at injection sites, there are ergonomic benefits for clinicians. When flow activation and aspiration are regulated by a microprocessor (as compared to manual flexions and extensions), the potential for cumulative trauma injuries to joints over years of administering local anesthesia is reduced.

NEEDLELESS ADMINISTRATION¹²

For patients who exhibit a fear of needles and anticipate pain with all injections, approaches that do not require the insertion of needles are worth considering. A number of topical products can be used effectively. One, a combination of lidocaine and prilocaine, is specifically designed for subgingival use during scaling and root planing. Another is a fast-acting vapocoolant spray applied prior to needle injection. It has no pharmacological load and has been demonstrated to provide a topical effect in five seconds, equivalent to a two-minute application of 20% benzocaine.¹⁴

Clinical options have expanded even further with a nasally administered anesthetic. This is a topical formulation of an ester, 3% tetracaine and 0.05% oxymetazoline, a vasoconstrictor. It provides pulpal anesthesia of maxillary anteriors and premolars without the use of needles.

PEOPLE FACTORS

Regardless of the approach to local anesthesia administration, clinicians’ adoption of new techniques is likely to enhance the patient experience. This can translate to increased confidence among patients and practitioners — a win-win combination.

It can be debated what percentage of the approximately 17 years it takes for advances to be adopted chairside is attributable to resistance to change. In the words of Parrish,¹ “This means we are not delivering the best, most comfortable, and most reliable care as we could if we were willing to try new things and not stay stuck in our dogma.”

CONCLUSION

In light of dental phobias over local anesthetic injections and the desire to improve the patient experience, many oral health professionals have wrestled with one or more of the following obstacles to change. Is the clinical change worth implementing, especially if the present approach is working fairly well? What value is placed on peer opinion? What sources should be trusted? What is the investment in terms of equipment and costs over time? Too many choices may, at first, create confusion over which choice is best. Yet, by implementing a variety of well-established approaches and expanding local anesthesia skill sets, dental providers position themselves to meet the needs of diverse patient communities.

STUDENT EXPERIMENT IN COMPUTER-CONTROLLED LOCAL ANESTHESIA

Unpublished data on the use of a computer-controlled local anesthesia device (CCLAD) reflects the experience of a group of 20 dental hygiene students, 10 of whom were first introduced to local anesthesia injection techniques using a CCLAD prior to learning traditional manual syringe techniques. (The control group first learned with a conventional syringe.) After six months, each group was introduced to the opposite delivery device.

During this time, all students received injections using CCLAD technology and traditional manual syringes. Overwhelmingly, students preferred receiving CCLAD injections. In addition, students in both groups preferred giving injections with the device with which they were first taught.

The results were the same when repeated with five classes over five years. Regardless of which device was taught first, both groups resisted changing to the other method. And these were early learners who had barely mastered either device.

A reasonable question arises: Is this resistance any less after graduates administer thousands of injections with a particular method?

KEY TAKEAWAYS

• Some patients’ fear of the dentist stems from anticipation of pain associated with local anesthesia administration, yet clinicians can help improve the patient experience by remaining current on injection techniques and technologies.
• According to J. Mel Hawkins, DDS, an internationally regarded dentist anesthesiologist, “Local anesthesia is still a dentist’s, dental hygienist’s and patient’s primary functional relationship.”⁶
• When it comes to local anesthesia administration, some providers are reluctant to try new approaches and devices — even if they are not particularly new to others.
• In fact, it has been estimated that worthwhile medical ideas backed by credible research take nearly 17 years to be integrated into routine practice.⁷
• Available devices can mitigate pain experiences and boost the confidence of both clinicians and patients. Whether the goal is cognitive distraction, gate-control (i.e., physical) distraction, or a true enhancement to injection technique, the net gain is positive.
• Anticipation of an improved patient experience and clinical success by embracing alternative techniques and technologies provides excellent motivation for trying new approaches to local anesthesia administration.¹¹

REFERENCES

1. Parish J. Personal communication: June 2016, June 2018.
2. Laltoo A. Personal communication: July 2018.
3. Royer R. Personal communication: July 2018.
4. DiMarco AC, Bassett KB. Rescuing failed inferior alveolar nerve blocks. Decisions in Dentistry. 2018;4(6):18–20.
5. Malamed SF. The Gow-Gates nerve block. Evaluation after 4,275 cases. Oral Surg Oral Med Oral Pathol. 1981;51:463–467.
6. Hawkins JM. personal communication: July 2018.
7. Ammerman A, Smith TW, Calancie L. Practice-based evidence in public health: improving reach, relevance and results. Annu Rev Public Health. 2014;35:47–63.
8. Hochman MN, Friedman MJ, Williams W, Hochman CB. Interstitial tissue pressure associated with dental injections: a clinical study. Quintessence Int. 2006;37:469–476.
9. Bassett KB, DiMarco AC. Maximize the benefits of computer-controlled local anesthesia delivery. Dimensions of Dental Hygiene. 2016;14(7):37–38.
10. Kudo M. Initial injection pressure for dental local anesthesia: effects on pain and anxiety. Anesth Prog. 2005;52:95–101.
11. Overly S. Humans once opposed coffee and refrigeration. Here’s why we often hate new stuff. Available at: washingtonpost.com/news/innovations/wp/2016/07/21/humans-once-opposed-coffee-and-refrigeration-heres-why-we-often-hate-new-stuff/?utm_term=.b1b86b7db1bb. Accessed February 13, 2019.
12. Bassett KB, DiMarco AC, Naughton DK. Local Anesthesia for Dental Professionals. 2nd ed. Upper Saddle River, New Jersey: Pearson Prentice Hall: 2014.
13. Menke RA, Gowgiel JM. Short-needle block anesthesia at the mandibular foramen. J Am Dent Assoc. 1979;99:27–30.
14. DiMarco AC, Wetmore AO. Clinical comparison: Fast-acting and traditional topical dental anesthetic. Anesth Prog. 2016;63:55–61.

The authors have no commercial conflicts of interest to disclose.

Featured image by  CODE6D/E+/GETTY IMAGES PLUS

From Decisions in Dentistry. March 2019;5(3):17–18,20–21.