Non-Injectable Local Anaesthesia in Dentistry: A Review and Case Study

by David Isen, BSc, DDS

Dental practitioners depend on the evolution of their field to provide patients with the highest quality, most advanced and comfortable dental care. Halsted first gave an inferior alveolar nerve block using cocaine and boiling water in 1884 and cocaine was earlier demonstrated as a topical anesthetic for eye surgery by ophthalmologist Karl Koller that same year. Once the chemical identity of cocaine was identified as a benzoic acid ester, the synthetic formulation of different anaesthetics both topical and injectable became possible. However since 1943, when Lofgren invented lidocaine, and 1983 when articaine first became available in Canada (articaine became available in the United States in 2000), injectable local anesthetics have not changed. Intraoral anaesthesia has evolved however in the area of non-injectable delivery systems. That is, methods of providing anaesthesia directly into the periodontal pockets without the need for an invasive injection. This article will review non-injectable local anaesthesia in dentistry and will include the presentation of a case demonstrating the use of this anaesthetic approach.

In 1993, a novel and very interesting topical anaesthetic entered the American marketplace called EMLA®. Its name is an acronym for “Eutectic Mixture of Local Anesthetics”. In medicine, EMLA is indicated for dermal procedures such as venipuncture, prior to vaccination, superficial surgical procedures, some laser treatments and as a topical anaesthetic for minor surgeries on genital mucosa. There are no current intra-oral dental uses listed in the product monograph for this cream.1 EMLA is an emulsion made up of equal amounts of lidocaine and prilocaine each at a concentration of 2.5% or 25 mg/ml. Since local anaesthetics are additive in their toxic potential, EMLA is considered a 5% solution.

Although not indicated for dental use, there are studies looking at the anaesthetic potential of EMLA when used intra-orally.2-7 EMLA has been shown to reduce pain during probing,2 hand scaling,3,4 ultrasonic scaling,5 rubber dam clamp application6 and palatal injection.7 In one of these studies, the investigators looked at EMLA’s ability to anaesthetize the periodontal sulcus.2 The challenge, since there was no direct way to introduce EMLA directly into the sulcus, was to deliver the cream in a way that it would remain around the gingival margin long enough to create soft tissue anaesthesia. To achieve this, the subjects had a custom acrylic splint fabricated and the EMLA was placed inside the splint which was then inserted over the patient’s dentition. The splint, similar to a custom whitening tray, was designed to cover and go beyond the gingival margin. The splint was left in place for 5 minutes. There are challenges that one would have trying to incorporate this methodology into a clinical setting. Custom splint fabrication and leaving the topical anaesthetic on for five minutes are onerous. Having a delivery system that enables the easy application of a fast onset, profound, non-injectable anaesthetic would be beneficial. Also, having this product approved for intra-oral use is obviously necessary. However, is there a need for such a product?

In routine dental operations, for example restorative, endodontic and surgical, injectable local anaesthetics allow dentists to provide treatment without the patient feeling pain. What about hygiene procedures like scaling and probing? In a study already mentioned above, two-thirds of patients considered gingival scaling unpleasant and painful.3 Another study suggested that 30% of patients require pain control during scaling and root planing.8 Sometimes when a patient presents for a dental hygiene visit, the procedure is painless except for one or two areas where the inflammation of a localized gingivitis or periodontitis makes complete debridement of that pocket painful. The pain associated with this localized procedure might make it difficult for thorough sanitization of the sulcus and thus the spiral of continued periodontal disease due to left over debris continues. Also, if patients avoid dental hygiene visits because of the pain they associate with it, they will also obviously have worsening periodontal disease. In this author’s dental practice, many patients present for treatment following years of absence from a dental office. For these people, frequently the biggest hurdle is the pain control required for the dental hygiene visit(s) and not restorative treatment.

Prior to the availability of the product to be discussed below, the choices for pain control during a dental hygiene visit were either injectable or topical anaesthetics. Injections of course are not favoured by most individuals with one study showing 25% of adults surveyed having a fear of dental injections9 and a second study showing that 55% of individuals reported severe pain from their last dental injection.10 Also, using injectable local anaesthetics has the disadvantage of making the patient feel extremely uncomfortable if used in all four quadrants in one appointment, not to mention the duration of anaesthesia outlasting that of the hygiene session. Also, if practicing in an area where a dental hygienist cannot administer injections, the dentist must go to the hygiene room to administer the anaesthesia. This is time-consuming and disruptive. Topical anaesthetics at least have the advantage of avoiding the need for an injection however if used for whole quadrants at a time, isolating them to that area for long enough to create anaesthesia is difficult. This may be why in the study already mentioned, a custom splint was required.2 Also, successful anaesthesia when topical anaesthetics are used, especially for deeper periodontal pockets, is marginal at best.

From this discussion and literature presentation, one could easily argue that there is the need for a non-injectable local anaesthetic that is specifically designed to be utilized within the periodontal sulcus to alleviate the pain associated with scaling and probing. A survey done by Matthews et al. asked people to state their preference for either a local anaesthetic injection, the administration of a non-injectable anaesthetic gel or no anaesthetic at all for their regular dental hygiene visits. The overwhelming majority chose the dental gel as their first preference11. This same study showed that patients had a “willingness to pay” for this service at a rate of $10.00 to $20.00 per appointment.

An example of one such product, although not a gel but a liquid, is Cetacaine®. It is a mixture of three local anaesthetics; 14% Benzocaine, 2% Butamben and 2% Tetracaine. The liquid comes in a bottle with a Luer-lock receptacle in the cap that allows for attachment of a Luer-lock syringe. Once connected, the anaesthetic can be drawn from the bottle into the syringe and then a needle is attached to the syringe. In an evaluation by Clinical Research Foundation in 2009, Cetacaine was reported to provide soft tissue anaesthesia but not adequately in all patients and if not placed one drop at a time, it was challenging to keep the anaesthetic in the sulcus and as a result, other soft tissue areas were anaesthetized. The maximum recommended dose of Cetacaine per appointment is 0.4 ml.12

Another product similar to Cetacaine, more recently available, is called HurriPak™. It is also a liquid this time containing 20% Benzocaine. HurriPak comes in a jar and is packaged with disposable syringes and plastic tips that allow the introduction of the liquid into the periodontal sulcus. The maximum recommended dose of HurriPak is 3 ml.13 As Cetacaine and Hurripak contain Benzocaine, they are classified as ester based anaesthetics. Therefore, they are contraindicated for those with an allergy to PABA, a metabolite of ester local anaesthetics. Since all ester anaesthetics have PABA as one of their metabolites, allergy to one constitutes allergy to all ester anaesthetics. As well, Benzocaine has been shown to cause methemoglobinemia when used in high doses and
in those susceptible to this syndrome. It should also be noted that bleeding or abraded tissue (for example the periodontal sulcus for those with periodontal disease) might allow the systemic absorption of benzocaine more easily. This could contribute to a higher realized systemic dose and therefore increase the risk for methemoglobinemia, especially in the very small patient (young children) and in those susceptible to this syndrome.

With respect to benzocaine in both Cetacaine and HurriPak and pregnacy, it should be noted that benzocaine is considered by the FDA in the United States as a Class C drug. This means that animal reproduction studies show an adverse effect on the fetus and there are no studies in humans but possible benefits might warrant use of the drug in women who are pregnant despite potential risk.

In 2004 in the United States, and in 2010, in Canada, a new anaesthetic gel became available for intra-oral use. This product is called Oraqix®. It is a periodontal gel that achieves soft tissue anaesthesia of the periodontal pocket when directly applied in that area. It is indicated for scaling and/or root planing in adults. Oraqix is similar to EMLA in that it contains 2.5% lidocaine and 2.5% prilocaine in a eutectic mixture. In addition, unlike EMLA, Citacaine or HurriPak, Oraqix contains thermosetting agents (poloxamer 188 purified and poloxamer 407 purified).14 These compounds allow Oraqix to change from a liquid at room temperature to a thicker gel once it is introduced into the periodontal sulcus and it reaches body temperature. Figure 1 shows a congealed drop of Oraqix on the gingival tissue. It can be seen that the gel will not flow away from this area of placement due to its viscosity (Figure 1). Since the gel remains within the periodontal pocket, it will not encroach upon other intra-oral areas and stay in place long enough to achieve soft tissue anaesthesia only of the periodontal sulcus.

Oraqix does not contain a vasoconstrictor or preservative and has a pH in the basic range of 7.5–8.0.14 This non-acidic property may make Oraqix more effective when applied in areas of gingival infection or inflammation. Infected tissue is acidic and this environment is not conducive to allow local anaesthetic molecules to achieve anaesthesia. The use of an acidic solution to try to obtain anaesthesia, for example any injectable local anaesthetic with a vasoconstrictor, can make this acidic environment even more acidic and thereby make the chances of obtaining anaesthesia less likely. This is why a more basic solution, like a non-vasoconstrictor containing injectable local anaesthetic or Oraqix, may have more success in areas of infection.

Oraqix is supplied in a dental cartridge that contains 1.7g of gel (Figure 2). The cartridge is fitted with a plastic safety collar so that it will not fit in a dental syringe. Oraqix is not for injection due to its higher concentration and thicker viscosity. The Oraqix cartridge is packaged in individual blister packs along with one Luer-lock 23 gauge, blunt tip cannula (Figure 3). To administer Oraqix, a reusable, autoclavable, proprietary dispenser is required. It accepts the cartridge of Oraqix and the single use, Luer-lock cannula (Figs. 4a&b and 5). On the dispenser, there is a lever that when depressed, expresses drops of the anaesthetic gel through the cannula. The cannula can be bent to 45° to allow easier access to the gingival sulcus around posterior or anterior teeth (Figure 6).

From the perspective of maximum dose and toxicity, there are a number of considerations. This is a 5% solution of anaesthetic that is absorbed systemically. One study measuring plasma levels of lidocaine, o-toluidine (a metabolite of prilocaine responsible for methemoglobinemia) and prilocaine showed that five cartridges of Oraqix administered to 11 subjects over a 2.6–3.4 hour period did not produce unsafe levels with respect to toxicity.15 The product monograph for Oraqix suggests five cartridges as the maximum recommend dose. However since this was given over a 2.6–3.4 hour period and since only one cartridge is usually required for each quadrant of the mouth, a maximum dose of four cartridges should be sufficient. It should not be necessary to administer more than that even if it is used in the whole mouth. Contraindications for the use of Oraqix include children, allergy to prilocaine and/or lidocaine and congenital (glucose-6-phosphate dehydrogenase deficiency) or a history of idiopathic methemoglobinemia. Similar to the use of any drug, caution should be exercised in the geriatric population and those with liver disease due to possible reduced metabolic breakdown and possible increased toxicity of lidocaine and prilocaine. It should also be kept in mind that the toxic effect of local anaesthetics are additive and so if Oraqix is used in conjunction with injectable local anaesthetics, regardless of which injectable anaesthetic is used, the practitioner should be judicious with respect to the amount of each utilized. In pregnancy, the FDA has classified Oraqix in Category B. This means that animal reproduction studies have failed to demonstrate risk to the fetus and there are no adequate and well-controlled studies in pregnant women or animal studies have shown an adverse effect, but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus in any trimester. The final precaution is for nursing mothers since lidocaine and possibly prilocaine are secreted in breast milk.

Does Oraqix work and what are the side effects? Before Oraqix was released, three multicenter, placebo controlled, double blind studies were carried out to study its efficacy.16-18 In each of these studies, Oraqix was associated with significantly less pain during scaling than a placebo. In a study measuring onset and duration of soft tissue anaesthesia, it was shown that Oraqix had an onset of action of 30 seconds. That is, the gingival crest, when probed with a blunt tip, felt numb in 30 seconds. There were no signs of tongue, lip or cheek anaesthesia. The mean duration of anaesthesia was 17 to 20 minutes.19

It has also been shown that Oraqix has few side effects. Those limited number reported were minor in nature, of short duration and less substantial than compared to side effects following local anaesthetic injections.19–21 Examples of side effects include one subject experiencing an unpleasant taste when the periodontal pocket was inadvertently over-filled and two subjects reporting minor discomfort during application.22

Clinically, the following procedure for the application of Oraqix by a dentist or dental hygienist is recommended to enhance effectiveness. First, load the dispenser with a cartridge of Oraqix. Then, introduce the dispenser into the patient’s mouth and trace a few drops of Oraqix onto the gingival margin and wait 30 seconds. This allows the gingiva to become anaesthetized and now the cannula can be introduced into the sulcus with more comfort. The next step is to insert the blunt tip applicator into the periodontal pocket and slowly depress the paddle on the dispenser to fill up the periodontal pocket with Oraqix. (Evidence of a full periodontal pocket will be seen with the surfacing or overflowing of the product at the gingival margin). Wait 30 seconds before starting to scale and if desired the Oraqix can be rinsed away before debridement begins. When multiple sites or quadrants require Oraqix-induced anaesthesia, keep in mind that the duration of anaesthesia is around 20 minutes and the practitioner will need to consider how long it will take to debride each area. Therefore, the operator might place Oraqix in one or two sites or quadrants at a time, complete scaling and then place Oraqix in the next quadrant.

Case Study

To show the effectiveness of Oraqix and how it can be used clinically, a case study is presented. A patient (Mrs. W.) is a 59-year-old woman who recently came to the author’s dental clinic after not having seen a dentist for more than 10 years.
Following an initial meeting, it was revealed that she harbors extreme dental phobia, including a fear of having injections in her mouth and this is why she has stayed away from dental offices. Mrs. W. requested intravenous sedation for all treatment. After discussion, it was revealed that Mrs. W. did not have an escort to accompany her (as is required for sedation appointments) and so we decided to try her initial dental hygiene visit without sedation. Oraqix was specifically chosen for this patient in order to achieve soft tissue anesthesia of her gingiva for her hygiene visits thereby avoiding the need for an injection of a local anaesthetic. We did not think that a topical anaesthetic would have provided profound enough soft tissue anaesthesia to make Mrs. W. comfortable. As well, since there was the need to apply the anaesthetic throughout Mrs. W.’s whole dentition, we chose Oraqix due to its thermosetting agent. This allowed for easy control of the anaesthetic such that we were able to apply it into the sulcus areas and did not have the problem of run-off or flow into other areas of her mouth.

Initial radiographs (Figures 7–9) and exam revealed that Mrs. W. has advanced periodontal disease with the need for some extractions in the anterior mandible and first quadrant. It was decided that due to the amount of scaling required, and because Mrs. W. did not feel comfortable with dental procedures, scaling and probing would be completed in two visits. During the first session, complete debridement of maxillary and mandibular left quadrants followed by probing was carried out and during the second appointment; the same procedure was done for maxillary and mandibular right quadrants.

Oraqix was placed by the dental hygienist, in the periodontal pocket around all teeth in the quadrants being treated. To make the introduction of the cannula into the pocket more comfortable, Oraqix was first placed around the gingival margin, outside the pocket and allowed to remain for 30 seconds (Figures 10 and 11). The cannula was then introduced into the pocket and Oraqix was applied (Figure 12) until the pocket was full as determined by the surfacing of the anaesthetic coronal to the gingival margin (Figure 13 and 14). After a further 30 seconds, the dental hygienist began the scaling procedure.

After debridement, probing revealed depths of 5 to 10 mm. Oraqix was successful at allowing the dental hygienist to scale Mrs. W.’s teeth and probe the sulcus without Mrs. W. feeling discomfort. Mrs. W. did report a few areas of root sensitivity which is not surprising since Oraqix is not reported to provide anaesthesia of the dentition.

In summary, Oraqix effectively provides safe and reliable soft tissue anaesthesia of the periodontal pocket. It has a fast onset, long duration and is easy to use for a dentist or dental hygienist. For patients who present with sensitivity to scaling, Oraqix allows for more comfortable dental hygiene appointments whether it is for a specific painful site during scaling or for the gingival sulcus around all teeth in patients with early, moderate or advanced periodontitis. Because Oraqix is applied by dentists and dental hygienists alike, it can be a convenient, time-saving product.OH

David Isen’s dental clinic in Toronto is a sedation-based practice focusing patients with special needs or dental phobia. He lectures for the University of Western Ontario’s continuing education program and as well has given presentations throughout North America and around the world. He is a Fellow of the Academy of Dentistry International, The International College of Dentists and The Pierre Fauchard Academy. Dr. Isen has acted as a consultant for a variety of dental and pharmaceutical companies.

Oral Health welcomes this original article.


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