Trisha E. O`Hehir, RDH
Although many dental hygienists now are licensed to provide local anesthesia, others still are denied this opportunity. Now, there is a product of interest to hygienists in both groups - the lidocaine patch. Controlled delivery of lidocaine will provide a more reliable topical anesthetic to be used prior to dental injections. These patches also will provide an anesthesia option for dental hygienists in states that have not yet changed the laws to include administration of block and infiltration anesthesia.
Conventional topical anesthetics sometimes can be effective in reducing the pain of injections, probing and subgingival instrumentation; however, some studies have shown no difference between topical anesthetics and a placebo. Of eight research studies evaluating topical anesthetics, only three demonstrated effectiveness for needlesticks. Transepithelial delivery of lidocaine provides anesthesia adequate for injections, probing and other procedures.
The bioadhesive-transdermal technology developed for controlled release of hormones and nicotine provided the model for intraoral adaptation. A transoral patch is now available which dispenses lidocaine through a bioadhesive matrix while the patch is in place. These patches are small, 1 inch by 1/4 inch, can be kept in place for up to 15 minutes, and may provide anesthesia for as long as 60 minutes, depending on the location. Onset of anesthesia occurs at 5 minutes and has been reported as early as 2.5 minutes.
These mucoadhesive patches have received FDA approval and are available in 10% and 20% concentrations. The 10% patches contain 23 mg of lidocaine; the 20% patches contain 46 mg. One cartridge (1.8 ml) of 2% lidocaine contains 36 mg. Lidocaine blood levels following injection of a full carpule of 2% lidocaine with 1:100,000 epinephrine peak at an average level 9 to 15 times greater than that measured during patch use.
Needlesticks with and without the lidocaine patches provide the mechanism for testing effectiveness. Study subjects agree to have several needlesticks in each area being tested. Pain associated with needle insertion to the bone is recorded on both a verbal scale and visual scale. To find patients, who are not subject to the placebo effect, needlesticks are done first using placebo patches. Those people who reported at least two or moderate pain on a scale from zero to four will continue on in the studies.
Published results from several studies confirm the effectiveness of lidocaine patches in reducing pain associated with needlesticks. In one study, a group of 100 patients had one patch placed in the premolar region of the maxilla and a second patch on the opposite side of the mandibular premolar area. The patches were randomly assigned so patients and examiners did not know which patch they were using: 10%, 20% or placebo patches. A 25 gauge needle, the largest diameter used for routine dental injections, was used in each area prior to patch placement and again at 2.5, 5, 10, and 15 minutes. Baseline needlestick pain ranged from 49 to 59 on the visual scale of 1 to 100 and 2.2 to 2.5 on the verbal scale of 0 to 4.
Onset of anesthesia was faster in the mandibular arch, noted at 2.5 minutes for the 20% patch. Onset was 5 minutes for the 10% patch and 5 minutes for both 10% and 20% patches in the maxillary arch. Both 10% and 20% patches provided an analgesic effect lasting 40 minutes or more in the mandibular arch. In the maxillary arch, the analgesic effect lasted only 10 minutes for the 10% patches and 40 minutes for the 20% patches.
An option to needlesticks in some procedures
Another needlestick study was carried out involving 5 research centers and a total of 116 patients. In this study, patches were tested only in the maxillary premolar area. Similar results were reported. Both of these needlestick studies reported side effects. Some redness was associated with the patches, but most of the side effects were due to repeated needlesticks and not to the patches.
For patients who find periodontal probing painful, the lidocaine patch may be just what they need. Researchers at the University of Florida tested the lidocaine patches on 9 volunteers using a variable force computerized periodontal probe. Although maximum effects were measured at 10 and 15 minutes, significant results were observed at intervals from 5 to 60 minutes.
In addition to being safe and effective for reducing pain associated with injections, the new lidocaine patches may be a substitute for local anesthetic injections for a number of dental hygiene procedures. The long duration analgesic effects may prove sufficient for pain control during subgingival instrumentation, polishing of sensitive teeth, periodontal probing, or therapeutic fiber placement. The lidocaine patch will enhance the efforts of dental hygienists licensed to provide local anesthesia by injection and provide an interim solution for those still working on law changes.
- Heins, P., Maruniak, J., Martin, R., Gibbs, C., Hassell, T.: Lidocaine Patch for Periodontal Anesthesia. J of Dental Research 72: #1578, 713, 1992.
- Maruniak, J., Heins, P., Hassell, T.: Periodontal Anesthesia with a Transmucosal Adhesive Patch. University of Florida.
- Houpt, M., Heins, P., Lamster, I., Stone, C., Wolff, M.: An Evaluation of Intraoral Lidocaine Patches in Reducing Needle-Insertion Pain. Compendium of Continuing Education in Dentistry 28: 309, 1997.
- Hersh, E., Houpt, M., Cooper, S., Feldman, R., Wolff, M., Levin, L.: Analgesic Efficacy and Safety of an Intraoral Lidocaine Patch. Journal of the American Dental Association 127: 1626, 1996.
Trisha E. O`Hehir, RDH, is a senior consulting editor of RDH. She also is editor of Perio Reports, a newsletter for dental professionals that addresses periodontics. Her e-mail address is [email protected].