RECENT ADVANCES IN LOCAL ANESTHESIA -OVERVIEW

D•. Deepti v.Oral & MaxiUefaeial Surgeon

ABSTRACTThe local anesthetic drugs presently available andused in dentistry represent the safest and most effec-tive drugs in all of medicine for the prevention andmanagement of pain. One drawback associated withintraoral local anesthesia is patients' fear of injections

.and the perception that these are painful. Recent ad-vances have resulted in the use of computer-con-trolled local anesthetic delivery vehicles to regulatethe delivery and rate of flow of local anesthetics atthe injection site, lessening potential discomfort as-sociated with injections. New injection techniquesthat provide reliable anesthesia, depending on thetechnique and area of anesthesia necessary havebeen discussed.KEYWORDS: Local Anesthesia, Fear Of Injections,Recent Advances, Computer-Controlled Technique.

William Halstead (1852-1922), administered an injec-tion of cocaine (with epinephrine) via inferior alveolarnerve block for the removal of a neuroma.

DESIRABLEANESTHETICPROPERTIES:A number of properties are desirable for local anes-thetic agents and techniques. Efficacy,safety and bio-compatibility are requirements .Other properties thatare desired for an ideal agent and technique includea rapid onset, adequate duration and profundity ofanesthesia, anesthesia of the targeted tissues andarea only, rapid reversal, a lack of side effects andcontra indications, a painless anesthetic delivery thatis also unobtrusive, and a technique that is easy andhas no, or a minimal, learning curve.

RECENTADVANCEDLOCALANESTHETICS:Topically Applied Local AnestheticsTopically applied anesthetics provide a degree of an-esthesia to nonkeratinized tissue (e.g., oral mucousmembrane) to a depth of2 to 3 mms. This permits theinitial penetration of mucous membrane to be ac-complished painlessly. Application of a small amountof topical anesthetic to the injection site prior toneedle penetration is an integral step in the deliveryof atraumatic injections2.Topical anesthetics are used in concentrations thatare higher than those used when the drug is injected.For example, lidocaine injectable is a 2% solution,while when used topically as a gel or ointment it iscommonly 5%. Benzocaine, the most commonlyused topical anesthetic, is used in a 20% concentra-tion (gel, ointment, spray).Oraqix, a recently introduced locally applied anes-thetic gel, is a eutectic mixture of prilocaine and lido-caine, each in a 2.5% concentration.Tricaine Blue, Tridocaine, TrioCaine and Profound

topical are compounded topical anesthetics contain-ing benzocaine, lidocaine and tetracaine.

INTRODUCTION:Dental treatment has long been associated, in themind of the patient, with pain. Indeed, fear of pain isone of the most significant factors deterring adultsfrom receiving non-emergency dental care, evenmore so than the monetary cost of treatment.The dental profession can take pride in its role inleading the development of the art and science ofanesthesia.Dr. Horace Wells, a Connecticut dentist, became the

first person to use anesthesia for therapeutic reasonswhen he received 100% nitrous oxide (N20) inDecember 1844, prior to the extraction of a molar."

LOCALANESTHETICS:Carl Koller (1857-1944), an Austrian ophthalmolo-gist, demonstrated the effect of cocaine asa local an-esthetic for eye surgery in 1884 instilling drops of co-caine onto the surface of the eye, providing topicalanesthesia. For the first time, a patient was able toundergo a surgical procedure awake and withoutpain.

RECENT ADVANCES IN LOCAL ANESTHESIA -OVERVIEW

TRANSCUTANEOUSELEURICAL NERVESTIMULATION(TENS)(THE1980S):In the 1980s, the medical technique transcutaneouselectrical nerve stimulation (TENS)was modified foruse in dentistry as a means of obviating the need foran injection of LAfor pain control- in other words, of-fering pain control without using needles. With elec-trodes applied intraorally and the current deliveredat a higher frequency, pain control was achieved.Routine dental procedures,restorations, root planingand curettage were accomplished painlessly in a sig-nificant percentage of patients who used TENS.Thedental application of TENSwas renamed electronicdental anesthesia (EDA)3-S. When EDA worked, itworked well. Unfortunately, it turned out that EDAdid not produce a consistently reliable level of paincontrol.VIBRAJEU: The Vibraject utilizes vibration to reducethe sensation of pain during injections. This deviceutilizes a battery-powered attachment that is placedover a regular dental syringe and provides a series offine vibrations to the needle tip during introductionof the local anesthetic. The Vibraject has been foundto reduce pain during local anesthesia proceduresand is not restricted to one injection technique.COMPUTER-CONTROLLEDLOCALANESTHETICDELIVERYSYSTEMS(THE1990S-PRESENT):In the mid-1990s, work began on the development oflocal anesthetic delivery systems that incorporatedcomputer technology to control the rate of flow ofthe anesthetic solution through the needle. This con-cept is now called computer-controlled local anes-thetic delivery (CCLAD)6.The first of these CCLADde-vices, the Wand™ (Milestone Scientific, Inc., Livings-ton, N.J.),was introduced in 1997. The system en-abled a dentist or hygienistto accurately manipulate needle placement with fin-gertip accuracy and deliver the LAwith a foot-activat-ed control. The lightweight handpiece is held in apen-like grasp that provides the user with greatertactile sensation and control compared to a tradition-al syringe. The available flow rates of LA delivery arecontrolled by a computer and thus remain consistentfrom one injection to the next.Several CCLAD systems are available, including theWand/CompuDent ™ system, Comfort Control Sy-ringe™,QuickSleeper™and ����������� Both the Com-fort Control Syringe and the Anaeject regulate thespeed of injection, starting slowly arid acceleratingthe speed of injection to minimize pain.

COMFORTCONTROL SYRINGE

P-ASAThe palatal approach-anterior superior alveo-lar nerve block provides pulpal anesthesia to the sixanterior teeth - canine to canine bilaterally aswell asthe palatal and labial gingiva and mucoperiosteumand bone overlying these teeth. As noted with theAMSA,there is no collateral anesthesia extraorally.New Injection TechniquesTwo new injection techniques, the AMSA7,8 and P-ASA9-13, have been described since the develop-ment of CCLAD.AMSA The anterior middle superior alveolar nerveblock provides pulpal anesthesia to the maxillary in-cisors,canines and premolars on the side of injection.Soft tissue anesthesia is achieved for the entire hardpalate on both that side and the intraoral mucosa ofthe five anesthetized teeth. Significantly, no extraoralanesthesia develops with the AMSA,a benefit to boththe patient (functionally and esthetically) and thedoctor during cosmetic procedures (no drooping ofthe upper lip).INTRAOSSEOUSANESTHESIA:lntraosseousanesthe-sia involves the placement of local anesthetic directlyinto the cancellous bone spaces adjacent to thetooth or teeth that require anesthesia. This techniqueoffers rapid onset of pulpal anesthesia.Methods used have included the use of two-step andone-step techniques. Using a two-step technique, abur is first used to penetrate the bone using a slowspeed handpiece, after which the local anesthetic is�������A one-step technique (lntraFlow™ Anesthesia Deliv-

ery System) uses a slow-speed hand piece with aneedle (perforator) and transfuser, resulting in pen-etration of the bone and immediate flow of anesthet-ic without a separate step. This technique usesa footpedal to regulate flow.SINGLE-TOOTHANESTHESIA:ln2006, the manufac-turers of the original CCLAD,the Wand,introduced anew device, Single Tooth Anesthesia (STA'M).sTAin-corporates dynamic pressure-sensing (DPS)

RECENT ADVANCES IN LOCAL ANESTHESIA-OVERVIEW

technology that provides a constant monitoring ofthe exit pressure of the local anesthetic solution inreal time during all phases of the drug's administra-tion.STA utilizes an adaptation of DPS to dentistry as ameans of overcoming the problems associated withPDL injection, and simplifies AMSA and P-ASAinjec-tions. The system can be utilized for all traditional in-traoral injection techniques. STAincludes a trainingmode that verbally explains how to use the device,and multi-cartidge and auto-cartridge retraction fea-tures.OTHERSNeosaxitoxin, a new local anesthetic derived fromalgae, had significantly less postoperative pain andrecovered about two days sooner than those giventhe commonly used local anesthetic bupivacaine15.Neosaxitoxin (neoSTX) provides local anesthesia formore than 24 hours. It is a site 1 sodium-channelblocker, part of a larger classof emerging anestheticsbased on molecules derived from aquatic organisms.

Local anesthesia delivered through an inhalablenasal spray quickly travels down one ofthe face's pri-mary nerves to the mouth, which could be more ef-fective than injecting it into the gums with aneedle16.SUMMARY:Local anesthesia forms the backbone ofpain control techniques in dentistry, and local anes-thetics are the safest and most effective drugs in all ofmedicine for the prevention and management ofpain. However, the administration of these drugs isthe most frightening and uncomfortable part of thedental appointment for most patients. The needle isthe most fear inducing part of the armamentariumfor the delivery of LAs.Over the years, many futile attempts have been madeto provide clinically adequate pain control withoutthe need for injection of drugs. Recent developmentsin CCLADsystems have made the delivery of local an-esthesia to patients significantly more comfortableand, with the PDL,AMSA and P-ASAinjections, con-siderably more successful.The ability to deliver pain-less injections and a desirable level and duration ofanesthesia results in reduced patient fear, reducedpatient stress (and therefore reduced stress for theclinician) and can aid patient compliance with cur-rent and future dental treatment.Refrences:1. Stanley F. Malamed, DDS Anesthetic Agents andComputer-Controlled Local Anesthetic Delivery(CCLAD)in Dentistry A Peer-Reviewed

Publication: www.ineedce.com2. Malamed SF. Basic Injection Technique, in Mal-amed SF.Handbook of Local Anesthesia. 6th edition,CVMosby, St. Louis 2004.3. 14. Meechan JG,Gowans AL, Wellbury RR.The useofa patient-controlled transcutaneous electricalnerve stimulation (TENS)to decrease the discomfortof regional anaesthesia in dentistry. A randomizedcontrolled clinical trial. J Dent. 1998;26(5):417-20.4. Hochman R. Neurotransmitter modulator (TENS)for control of dental operative pain. J Am Dent Assoc.1988;116:208-12.5. 16. Malamed SF,Quinn CL,Torgersen RT,Thomp-son W. Electronic dental anesthesia for restorativedentistry. Anesth Prog. 1989;36:195-7.6.Proceedingsof the 1st Annual Computer-Controlled Local Anes-thesia Delivery (C-CLAD) Systemmeetinq.lntroductory.rernarks. New Orleans, La.,Feb2008.7. Friedman MJ, Hochman MN.The AMSA injection: anew concept for local anesthesia of maxillary teethusing a computer-controlled injection system.Quintess Int. 1998;29(5):297-303.8. 27. Malamed SF.Techniques of Maxillary Anesthe-sia, in Malamed SF. Handbook of Local Anesthesia.6th edition, CVMosby, St. Louis 2004, p. 213-217.9. 28. Malamed SF.Techniques of Maxillary Anesthe-sia, in Malamed SF. Handbook of Local Anesthesia.6th edition,CV Mosby, St. Louis 2004, p. 217-220.10. 29. Friedman MJ, Hochman MN. P-ASAblock in-jection: a new palatal technique to anesthetize maxil-lary anterior teeth. J Esthet Dent. 1999;11(2):63-71.11. 30. Friedman MJ,Hochman MN. Using AMSA andP-ASAnerve blocks for esthetic restorative dentistry.Gen Dent. 2001;49(5):506-11.12. Ram D, Kassirer J. Assessment of a palatal ap-proachanterior superior alveolar (P-ASA)nerve blockwith the Wand in paediatric dental patients.lnt J Pae-diatr Dent. 2006;16(5):348-51.13. Friedman MJ, Hochman MN. P-ASAblock injec-tion: a new palatal technique to anesthetize maxillaryanterior teeth. J Esthet Dent. 1999;11(2):63-71.14. Malamed SF.The periodontal ligament (PDL) in-jection: an alternative to inferior alveolar nerve blockOral Surg. 1982;53:117-2115. Clay Dillow Posted Inhalable Local ����������Could Replace Painful Needles at the Dentist16. Inhalable Local Anesthesia Could Render ThaNeedle Obsolete17. Ropivacaine - a new local anesthetic.