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On the subject of Ultracaine….. Nov. 17/05 Over the last 11 years I have been studying the role the rate of injection plays in the injection process, in regards to trauma, safety and efficacy of various drugs. Perfecting this injection process lead to the development of computerized syringe technology in 1994.This patented product is marketed by Dentsply International as the Comfort Controlled Syringe(CCS) ,for the delivery of local anesthetics. The very first drug we started with 11 years ago was the ultracaine local anesthetic. I believe the negative attention this local anesthetic has attracted is totally undeserved. The assumption that this drug is any more neurotoxic than other local anesthetics based on Drs, Haas's and Lennon's study is very questionable. Even if Dr. Haas's and Lennon's data collected was consistent ( which I don't think it was ) the more obvious conclusion would lead to a neurotrauma from the injection process than a neurotoxicity. When the CCS device was being developed in the early 90's it was the ultracaine carpule that gave the engineers the most trouble. It had a high grade silicone rubber plunger. This rubber plunger took the least amount of thumb pressure to advance. When you are trying to standardize everything, this was not a good thing. It did result in smooth effortless injections. It was this ease of delivery with a manual syringe that attracted many dentists including myself to ultracaine. It also made me very aware that the contents of this carpule could be expelled very quickly. In 1985 Dr. Malamed's study showed the average time taken by dentists to expel a full carpule of anesthetic was 15 secs. Dr Malamed describes a traumatic injection as the injection of a full carpule in less than 30 seconds. Could this fast rate of delivery be causing problems? Dr Haas recorded the number of paresthesias as reported to the college in the early and mid 90's. He then went back and compared this number to the number of cases reported over a similar time frame prior to the introduction of ultracaine in 1985. His assumption was that all things being equal you could statistically show ultracaine was producing more paresthesias and this was due to neurotoxicity. Not all things were equal over these time frames, nor was the reporting. Being an Ontario dentist and developing this syringe at the same time Dr.Haas was collecting his data, I can say this was a time experimentation for many dentists. Dentists were experimenting with the thinner needles, and the different techniques. Some lecturers were recommending two full carpules for an I.A.N. block- one long, one short ( you can imagine the speed the second injection would have been given). Giving two injections multiplies the chance of a paresthesia by a factor of two. In many instances volume replaced technique. Swinging the needle around the ramus of the mandible in order to access the IAN was popular. Dentists started bending their needles to accomplish this. The needles themselves changed in quality, with sharper multi beveled tips. In the late 80's and early 90's ultracaine was becoming very popular and with it rumors of potential paresthesia problems surfaced, well before the release of Dr. Haas's study. In the early 90,s our dental college changed insurance carriers. There was a directive from the college on how to deal with paresthesias. Besides giving the technical advice on how to treat a paresthesia we were told to call the college pre-emptivly, in case the patient files a complaint. This in itself brings into question the data collected by the college and used in Dr. Haas's study. When I asked one experienced dentists why he happened to report a paresthesia to the college in the period of Dr. Haas's study his reply was he was told to. Would he have called had he been using lidocaine? His answer was no. I don't remember any other directives from the college regarding paresthesias. The lingual nerve has roughly twice the incidence of paresthesia as the I.A.N. If the bulk of the anesthetic is deposited in close proximity to the I.A.N. surely this nerve would be the more affected nerve? What about the mental nerve or some of the smaller maxillary nerves? I don't think ultracaine could be selective in what nerve it is going to affect in a negative neurotoxic way. The lingual nerve lies in the path of our access to the I.A.N.. It is a poor injection and delivery technique that is more likely to cause a lingual paresthesia. Without better controls on the injection process it is very difficult to make the assumptions Dr. Haas has made regarding the neurotoxic effects of 4% articaine and the incidence of paresthesia. The ultracaine carpule itself leads to quick injections and should be given with a controlled slow delivery. Mauricio, unfortunately the paresthesia issue is being driven by the lawyers in the U.S.. As dentists we have been able to work under the veil that the chance of paresthesia is such a rare occurrence that we don't need patient consent prior to proceeding. In order to maintain this status our college seems willing to sacrifice the 4% solutions. This is a prejudiced view that does not have a scientific basis. Making the 4% solutions the scapegoat covers up a more serious problem-paresthesias are preventable. They result from poor technique, that is poorly taught. There are ways to prevent paresthesias whether using a manual syringe or a device like the CCS. When I teach dentists how to prevent paresthesias I explain it's not what is injected but how it is injected. Even saline will cause a paresthesia if injected with a traumatic injection technique. I have not had a complication in ten years of use with the CCS device and ultracaine. I believe this is do to superior needle control, an atraumatic rate of injection, and a safe effective local anesthetic. Mauricio if there is anything I can do to help regarding this subject I would be happy to help. Thanks Sincerely, Mark T. Smith D.D.S. "Ultracaine is a quality local anesthetic." "In cases where I feel that a Mandibular Block is not indicated in performing extractions, Ultracaine infiltration in the mandibular area is exceptional and provides superior anesthesia for pain free tooth removal." "In 40 years of practice, I have never seen any other local anesthetic perform in this fashion." Dr. Lawrence Gaum “The use of Ultracaine can and should change anyone's practice. The rapidity of onset, the reliability of duration and the total absence of sequelae make this the benchmark anaesthetic for any dental procedure.” Dr. Ken Serota “I do a lot of surgery in my practice. Rapid and profound anesthesia with low volume is important to me and my patients. I have been using Ultracaine for a long time.” Dr. Emil Svoboda PhD, DDS, General & Implant Dentistry On the subject of take-home whitening….. “Finally, a new generation tooth whitener with two sources of whitening.fusion2 is fast and virtually sensitive free!” Dr. Ed Philips, Toronto , Ontario On the subject of impression material…. “I decided to use Definition for a colleague’s full mouth reconstruction and was thrilled with the results! The handling of the material was exceptional and it produced such detailed results that I believe remakes will be a thing of the past. Combine this with its ultra fast intra oral set time and exceptional hydrophilic properties and this material is hard to beat!” Dr. Allan Fox On the subject of WamKey Crown Remover… "Best crown removal instrument, from patient comfort perspective. (Don't feel they're getting their heads hammered). Beautiful instrument to break cement attachment from the tooth. I love it." 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