The Evolving World of Non-Injectable Anesthesia

Needle-free anesthesia continues to be the first choice of patients for multiple dental procedures.¹ Over the years this method of anesthesia has evolved in the dental world. At one point practitioners simply grabbed a jar of flavored benzocaine gel and smeared it across the gingival tissue. Now, however, options to provide anesthesia without a needle have expanded with different delivery techniques and modalities. With these advances, the term "topical anesthesia" no longer encompasses all of the modalities that hygienists are working with that are needle-free, non-injectable anesthesia.

Some modes of delivery are to administer on the surface of the mucosa as a gel or spray, while others are to place using a canula sub-gingivally into the gingival sulcus. Electrical methods of intraoral anesthesia are also now gaining traction. Dentistry is truly working with non-injectable anesthesia. With these changes it is vital to understand the different pharmacological and non-pharmacological options available and how to select the correct product and modality for your patient.

Benzocaine Topical

Generally found as a gel, benzocaine is the most commonly used pharmacological non-injectable in dentistry.^2,3 Used on its own, benzocaine comes in a 20% formulation. However, it can often be mixed with other pharmacological non-injectables at a lower percentage.^2,4,5,6  The onset of anesthesia begins 30 seconds after application, and it achieves its full effects approximately 2 minutes later, and it can last about 15 minutes.^4,5

Currently there is not a maximum recommended dosage (MRD) for benzocaine.^3,4 Caution is encouraged when using large amounts at one time due to tissue sloughing and the possibility of sores forming around the application site.^4,6This is often a sign of a mild allergic reaction. Because benzocaine is part of the ester family it does have a higher rate of allergic reaction, as it metabolizes into para-amino-benzoic acid (PABA).^1,6 According to its FDA classification, it should be used sparingly with pregnant patients.^4,5 Another item of note is that benzocaine has been associated with methemoglobinemia, a condition in which the oxygen carrying capacity of the bloodstream is reduced due to a high volume of methemoglobin.^4,5

There are several different types of delivery applications for benzocaine. The most common is a 20% benzocaine gel packaged in a small container or as a single unit dose. It is usually placed with a swab on the oral tissues as a pre-anesthesia numbing agent. Many manufacturers have packaged the 20% gel within a small tube with a delivery canula that screws onto one end to aid in sub-gingival application. This modality is often used for procedures like periodontal assessment and sub-gingival instrumentation. Benzocaine can also come in a spray that is indicated for procedures involving the oropharyngeal space.^1,2,4,5

Lidocaine

Lidocaine is an amide-based anesthetic that is used as both an injectable and non-injectable anesthetic.^4,5 The use of lidocaine as a non-injectable anesthetic is found in many different fields, including dentistry and dermatology. It is even used for procedures such as micro needling and tattooing. When used on its own, lidocaine is found at a concentration of 5% to 10%.^2,4,5 Within dentistry, 5% lidocaine has been used as a gel or liquid to be applied to soft tissues.^3,4

When applied to the mucosa, lidocaine can provide deep and profound anesthesia. The first signs of onset can take 1 to 2 minutes, with profound anesthesia after 5 to 10 minutes.^4,5 Duration is dependent on which structures have been anesthetized but can last a minimum of 15 minutes with some reports of up to an hour.^2,4,5

Because this is an amide anesthetic, it is a desired option for most dental patients due to its low allergy rate. Also, if profound surface anesthesia is required on keratinized tissue, 5% lidocaine is a great option.⁴ The most common mode of delivery is via gel or spray.⁴ It is important to remember that the MRD of lidocaine as a topical anesthetic is 200 mg, which is different from the injectable version.^4,5It is advised to evaluate the package insert for the dosage recommendation.

Lidocaine/Prilocaine

This popular mixture of anesthetics combines 2.5% lidocaine and 2.5% prilocaine (Oraqix^®, Dentsply Sirona). ^3-7 The mode of application for this anesthetic mixture is for sub-gingival use. Utilizing a delivery device with a canula at the end, the solution flows as a liquid into the sulcus and then turns into a gel-like state as it mixes with crevicular fluid.⁷

Because lidocaine and prilocaine are amide anesthetics, there is a low risk of an allergic reaction.^2,4-6
Also, the FDA has lidocaine and prilocaine  listed as considerably safer for pregnant patients when compared with benzocaine.^2,4,5,7

Because this anesthetic enters the sulcus as a liquid form, it will flow around the tooth nicely. Once in the sulcus the lidocaine/prilocaine mixture  turns into a gel-like substance, allowing the solution to stay in place for a longer period. After 1 minute, profound soft tissue anesthesia is established and can last from 15 to 30 minutes.⁷ There have been anecdotal reports of short-term pulpal anesthesia as well. Due to the delivery method, the combination of lidocaine and prilocaine works well for full-mouth debridement and quadrant scaling.^1,7

Since these are both amide anesthetics, there is a lower risk of an allergic reaction. However, prilocaine has been associated with methemoglobinemia.^4,5,7 The MRD for this anesthetic combination is approximately 200 mg for each anesthetic which is nearly 5 cartridges of solution.⁷

Benzocaine/Tetracaine/Butamben

This ester-based combination has multiple modalities and is often used in other medical fields as well.^8,9 The formulation includes 14% benzocaine, which has a quick onset but a short duration⁴; 2% tetracaine, which has a slow onset but a long duration⁴; and 2% butamben, which has a medium length of both onset and duration.⁴ The benzocaine/tetracaine/butamben mixture utilizes the three different anesthetics' capacity for short-term, medium-term, and long-term anesthesia and thus has a broad range of applicable uses.^4,8,9

The anesthetic using this ester combination that is seen most often in dentistry (Cetacaine^®, Cetylite) takes effect quickly (in 30 seconds) and will last for nearly 45 minutes.^8,9 This mixture is ideal for soft tissue anesthesia with anecdotal evidence of minimal pulpal anesthesia as well. There are multiple different delivery methods, such as cream, gel, spray, or liquid to express into the sulcus.^8,9 This non-injectable is ideal for full-mouth debridement or scaling with hand and ultrasonic instrumentation. The spray version of benzocaine, tetracaine, and butamben  can be used to alleviate pain with procedures involving the soft palate, such as laser therapy for sleep apnea, discomfort with intraoral radiographs, and reduction of the gag reflex.

Although this non-injectable is highly effective, it must be used with caution, and the associated MRD is 0.4mL of anesthetic solution.^8,9 Dental professionals should refer to the packaging details to identify how this is measured with the selected delivery modality. In addition, this is an ester-based solution, so there is also a concern for allergic reaction and methemoglobinemia.^4,5,8,9

Dyclonine Hydrochloride

Dyclonine hydrochloride (HCl) is a ketone-based anesthetic that is often used as the numbing agent in sore throat sprays and lozenges.⁶ It also comes in a mouthrinse formulation that is used in dentistry (DycloPro, Septodont) as a 0.5% dyclonine hydrochloride solution.¹⁰ This solution can anesthetize the entire oral cavity and the oropharyngeal region. For patients with an amide and ester sensitivity, dyclonine hydrochloride  can be used as an alternative solution.^4-6

Dyclonine HCl is often used to reduce gagging but can also aid in pain management with dental hygiene assessment and debridement as well as for laser therapies on the soft tissue.¹⁰

The time for onset is approximately 2 to 10 minutes, depending on the patient, and it lasts for approximately 30 minutes. It is advised to not exceed 300 mg of dyclonine HCl. Not only is this solution used in dentistry, but it also has applications in other areas of medicine involving the oropharyngeal and anal regions.¹⁰

Transcutaneous Electrical Nerve Stimulation (TENS)

This non-pharmacological pain management system is used for a variety of reasons, most notably with neuromuscular disorders.¹¹ At one point the main dental applications were to address temporal mandibular joint (TMJ) issues.^11,12 However, it is gaining more traction in the dental world for intraoral pain management because a smaller, more portable mode of delivery is now available.

TENS units disrupt the communication of painful stimulus via neuromodulation.¹² The impacts of pain reduction are noticeable after 30 seconds to 2 minutes of use, depending on the structures.¹³ The original design was to eliminate pain from orthodontic movement, but current applications range from TMJ discomfort, dentinal sensitivity, and pre-anesthesia to minor restorative procedures in some cases.^12,14

The instructions for use indicate avoiding using this device for patients with neurological disorders and pacemakers.^12,14 The author, however, was unable to find literature reviewing a MRD or maximum use for this style of TENS unit, but recommendations are to apply for 10 to 20 seconds per tooth.¹⁴

Conclusion

Selecting the correct formulation and modality of non-injectable anesthesia is crucial for a successful dental appointment. When implementing non-injectable anesthesia, it is important to consider the procedure being conducted, the patient's health history, and the amount of time for which pain management is needed. Keeping these factors in mind will benefit your patients' comfort and wellbeing during their next dental visits.

References

1. Isen D. Non-injectable local anaesthesia in dentistry: a review and case study. Oral Health website. https://www.oralhealthgroup.com/features/non-injectable-local-anaesthesia-in-dentistry-a-review-and-case-study/. Published February 1, 2013. Accessed July 13, 2023.

2. Patel TJ. Update on dental topical anesthetics. Decisions in Dentistry. 2019;5(5):36-39.

3. Viola T. Tropical storm? The dental hygienist's guide to topical anesthetics. Registered Dental Hygienist. 2022;42(10):12-14.

4. Bassett K, DiMarco A, Naughton D. Local Anesthesia for the Dental Professionals. 2nd ed. Pearson; 2014.

5. Malamed SF. Handbook of Local Anesthesia. 6th ed. Elsevier Mosby; 2013.

6. Bell K. Topical anesthesia for dental hygiene procedures. Dimensions of Dental Hygiene. 2017;15(7):32, 34-35.

7. Oraqix instructions for use. Dentsply Sirona website. https://www.dentsplysirona.com/en-us/shop/P-BP-1000170219/oraqix.html. Revised March 2022. Accessed July 13, 2023.

8. Cetacaine topical anesthetic spray and liquid. Cetylite website. https://cetylite.com/sites/default/files/resources/Cetacaine-Spray-and-Liquid-Prescribing-Information.pdf. Revised February 2023. Accessed July 13, 2023.

9. Cetacaine^® topical anesthetic gel. Cetylite website. https://cetylite.com/sites/default/files/resources/Cetecaine%20Gel%20Literature.pdf. Published May 2017. Accessed July 13, 2023.

10. DycloPro instructions for use. Septodont website. https://www.septodontusa.com/product/pain-management-dyclopro/. Revised October 2019. Accessed July 13, 2023.

11. Finch P, Drummond P. Chapter 8: High-frequency peripheral nerve stimulation for craniofacial pain. In: Slavin KV, ed. Neuromodulation for Facial Pain. Karger; 2020:85-95.

12. Haralambidis C. Pain-free orthodontic treatment with the dental pain eraser. J Clin Orthod.2019;53(4):234-242.

13. How neuromodulation powers the Synapse Dental Pain Eraser. Synapse Dental website. https://dentalpaineraser.com/how-it-works-neuromodulation/. Accessed July 13, 2023.

14. Synapse Dental Pain Eraser: clinical scenario-based instructions. Synapse Dental website. https://dentalpaineraser.com/wp-content/uploads/Synapse_Dental_Pain_Eraser_Clinical_Scenario-Based_Instructions_Booklet.pdf. Published 2020. Accessed July 13, 2023.