The International Association for the Study of Pain defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage” [1]. In dental clinical practice, local anesthesia is a routine procedure to alleviate patient pain. However, the injection of local infiltration anesthesia and block anesthesia into soft tissues is the first painful experience patients endure. Therefore, the application of topical anesthesia before injection is a common clinical practice.

Topical Anesthesia: Real-World Testing and Effectiveness

Topical anesthesia involves applying anesthetics to the mucosal surface to provide a more comfortable treatment experience for patients. Its indications include: pre-local anesthesia, orthodontic band placement, simple tooth extractions, rubber dam placement, mucosal surface surgical treatments (e.g., incision of superficial submucosal abscesses), reducing palatal sensitivity during impressions, and applying to the surface of oral ulcers. Although topical anesthetics have high concentrations, they require a longer time (1–5 minutes) to take full effect. In clinical practice, they can be applied using a cotton roll pressed onto the dried mucosal surface to prevent the anesthetic from being lost.

A widely used topical anesthetic in clinical practice is 20% benzocaine gel, which is a composite local anesthetic that is more effective than benzocaine alone. However, because benzocaine is a significant cause of methemoglobinemia, it is not suitable for patients who have had methemoglobinemia or for children aged 2 years and under [2].

Studies have shown that combining local anesthetics with nanostructured carriers (such as liposomes and nanoparticles) can effectively enhance their adhesion in the oral cavity and improve anesthetic efficacy. Pre-treating the mucosa with ice before local anesthesia can also help alleviate injection pain [3]. We evaluated different topical anesthetics and methods for their effectiveness in alleviating pain from injection anesthesia. We tested six different types.

TYPE 1

TYPE 2

TYPE 3

TYPE 4

TYPE 5

TYPE 6

Topical Anesthesia Evaluation: Gels, Creams, and Cold Sprays

Test subjects were blindfolded during the experiment and rated their pain immediately after injection (T0) using the Numerical Rating Scale (NRS) ranging from 1 to 10. Six types of topical anesthetics were tested. Gels and creams (types 1-4) and cold sprays (types 5-6) were applied to provide physical cooling, with indications as pulp vitality testing agents according to the instructions.

Each volunteer received the treatments on the mucosal surfaces of their upper and lower lips at six randomized locations. Following the application of the topical anesthetics, an injection needle was used to puncture the mucosa to simulate anesthesia without the actual administration of anesthetics. The topical anesthetics were applied as follows:

• The buccal mucosal surface was dried.
• Types 1-4 were applied by repeatedly rubbing a small area with a cotton swab dipped in the gel or cream for one minute.
• Types 5-6 were applied by spraying a small cotton ball (approximately 5mm in diameter) and then rubbing it on the mucosa.

Immediately after the above treatments, a 30G needle was used to puncture the mucosa 2mm deep (no anesthetic was injected except by the author). Future evaluations of anesthetic injection methods will follow. The NRS pain scoring standard is as follows: 0 represents no pain, and 10 represents severe pain. The pain intensity grading is: 0 for no pain, 1-3 for mild pain, 4-6 for moderate pain, and 7-10 for severe pain [4].

Results:

1. Due to the small sample size, this evaluation does not allow for statistical analysis, and the following results do not constitute clinical recommendations. A future randomized controlled trial with statistically significant results is desirable.
2. Types 1 and 4 had nearly identical compositions and effects. Type 3 was a transparent gel, which posed an operational disadvantage due to its colorlessness, making it difficult to see the application area. Types 5 and 6 were cold sprays recommended by manufacturers to be sprayed on a small cotton ball and applied to the mucosa for 1-5 minutes before injection. However, for consistency, injections were made immediately after application. Volunteers felt a loss of sensation lasting several minutes after cold spray application, but this was accompanied by immediate, sharp pain from the cold spray, which lasted a few minutes. This initial pain overshadowed any subsequent pain from the injection.

Note: Cold sprays should not be applied directly to the block area as they can cause frostbite. Therefore, cold sprays should strictly be used for their indicated purpose as pulp vitality testing agents.

00001. [1]Raja, Srinivasa N. , et al. “The revised International Association for the Study of Pain definition of pain: concepts, challenges, and compromises.” Pain Publish Ahead of Print.9(2020).
00002. [2]Orrett, et al. “Local Anesthesia: Agents, Techniques, and Complications.” Dental Clinics of North America (2012).
00003. [3]Franz-Montan, et al. “Recent advances and perspectives in topical oral anesthesia.” Expert opinion on drug delivery 14.1a6(2017).
00004. [4]Thong I S K , Jensen M P ,Jordi.Miró,et al.The validity of pain intensity measures: what do the NRS, VAS, VRS, and FPS-R measure?[J].Scandinavian journal of pain, 2018, 18(1):99-107.DOI:10.1515/sjpain-2018-0012.