Anesto works fast and locally
Individual teeth can now for the first time be specifically anaesthetised locally using the new Anesto anaesthesia system from W&H. Prolonged numbness is now a thing of the past. Dr. med. dent. Mario Kirste MSc, specialist for implantology and oral surgery in Frankfurt (Oder), Germany, explains the advantages of the new form of intraosseous injection:
Over 120 years have passed since the introduction of local anaesthesia. The techniques of nerve-block anaesthesia and infiltration anaesthesia have changed only slightly over the course of many years, but their success is linked to a sound knowledge of anatomy. Topical anaesthesia and intraligamentary anaesthesia have led to the dental profession formulating their demands more clearly, albeit covertly, for dental anaesthesia. It should be fast and applied locally - with the emphasis on "locally" - and take effect just there.
Everything undertaken far away from the site of interest requires good technique, but is often subject to a long waiting time (exposure time), which is explained by the pharmacokinetics of the anaesthetic. If external conditions are compromised (e.g. due to inflammations), the anaesthetic effect may be impaired or under certain circumstances may not occur at all. Much is expected of the intraosseous anaesthesia technique. In choosing the injection region, there is already a desire to get closer to the site of action. The distance to the target object should be as short as possible for a quick effect. The principle is to avoid regions where large nerve and vessel structures run to keep collateral damage to a bare minimum. I have been an Anesto user for three years. This new anaesthesia system was developed by W&H in Bürmoos (Salzburg, Austria).
How is the injector constructed? It consists of a connecting piece which unites the single-use needle and the syringe cartridge. This element is inserted in the drive mechanism and locked. Finally a rotation safety sleeve is attached over the needle head so the drilling process does not injure any part of the gum or soft tissue. This injector is driven by a surgical motor or unit motor at the required speed of 15,000 - 25,000 rpm and must drive the needle through the cortical bone. The anaesthetic is then moderately and carefully injected into the spongious bone.
Intraosseous anaesthesia with Anesto is described in two phases:
Phase 1 is topical and/or infiltration anaesthesia with the non-rotating Anesto handpiece with the aim of placing the anaesthetic close to the periosteum, as the concentration of pain receptor is particularly high in the periosteum. Topical anaesthesia is preferred in regions with lower mucosal thickness and thicker keratinized gingiva. If there is a thin marginally keratinised zone, the ideal injection region for infiltration anaesthesia is in the flexible mucosa at the level of the medial and apical third of the root.
Once the periosteum is anaesthetised, the injector is operated at 15,000 - 25,000 rpm and the rotating
needle penetrates the cortical bone.
In the subsequent Phase 2 (intraosseous phase) the anaesthetic is injected directly into the spongious bone. As described in other resorption models, there is concentric propagation of the anaesthetic with the aim of anaesthetising the desmodontal structures close to the intervention zone.
Once the concentration in the application regions is saturated, not only does the desired local anaesthetic effect set in, but collateral effects are also observed. A concealed Phase 3 effect - indirect nerve-block anaesthesia - may also be achieved close to large nerve-vessel structures.
Most cases of application have been with articaine products with a vasoconstrictor in a 1:100,000 concentration, of course in a syringe cartridge filling. The α-receptors are addressed first at a low adrenalin concentration, which leads to vasoconstriction.
It was noticeable in the treatment that the whole syringe cartridge was rarely necessary to achieve the anaesthetic effect. The effect of this anaesthesia material is known to set in within 1 - 3 minutes and that deep anaesthesia can be achieved. In the case described here, the anaesthesia lasted around 45 minutes, which is certainly attributable to the small amount of anaesthetic used and the good blood circulation of the cancellous bone.
The advantage of this new anaesthesia application lies in the targeted, local and always visible application technique.
Comparing the techniques of different types of nerve-block anaesthesia in the maxilla and mandible provides an insight into the problems that can occur, or, in other words, why the accuracy of nerve-block anaesthesia is only 40 - 80%. The success rates for application of intraosseous anaesthesia are quoted at 90 - 97% in the literature. The rapid onset of action is an advantage particularly emphasised by endodontists worldwide.
The field of applications of Anesto extend from oral surgery to periodontology, endodontics through to prosthetics, but of course in conservative dentistry too.
Anesto has met with great interest among colleagues at congresses in the last six months. For this reason, I would like to address the most important questions that have been put to me in this respect:
- We know from the familiar anaesthetic techniques that there are anaesthesia failures. How high is the hit rate for Anesto?
In the period from February 2010 to January 2011 we asked a total of 532 patients following the first patient information interview whether they would accept anaesthesia with Anesto. After the treatment we wanted to know from them how the desensitisation had worked in their opinion. Patient selection was random and participation in this study was voluntary. No preselection was made with respect to injection regions, gender, age distribution and diagnosis. 478 patients were evaluated and we can report a hit rate of 97%.
- Can intraosseous anaesthesia be applied in every bone region or are there problem zones in your opinion?
The prerequisite is that the bone is sufficiently cancellous. The anaesthetic must be in a position to diffuse to the target site, i.e. there must be tissue which allows diffusion in order to arrive at the target site.
We must not forget that the suppression of sensitisation only occurs at nerve structures or in receptor regions. This is only in the region of the periosteum with the greatest receptor density, along the desmodontal structures and along the course of nerves. The cortical bone, for instance, is not innervated, no pain can be registered here, so no pain has to be suppressed. The injection should be placed in the transition zones between the middle and lower third of the root. This is where the root structures start to taper and there is sufficient clearance from the anatomically critical structures, such as the inferior alveolar nerve and the maxillary sinus.
I would describe the region between the lower premolars as contraindicated, as here the vessels could be punctured, which can cause painful haematomas.
- Which also answers the next question: Is penetration through the cortical bone painful and is the application of anaesthetic painful?
No, penetration, i.e. drilling through the cortical bone, is not painful. If the pumping process for applying anaesthetic is performed cautiously, this work step is also painless. Excessive administration of anaesthetic can cause reflux of anaesthetic, as the tissue is simply not able to resorb it.
- We know that in dental extraction various nerve structures should be anaesthetised by injection. Let us take the example of mandibular anaesthesia, here the mandibular nerve is anaesthetised if the nerve-block anaesthesia is correctly positioned; how does Anesto work in this situation?
The intraosseous anaesthesia primarily only affects the target region of the inferior alveolar nerve. To influence the innervated region of the lingual nerve, I recommend applying a topical anaesthetic. Although this is a separate treatment process, nerve damage as potentially occurs with direct nerve punction or application close to the mandibular or lingual nerve will be avoided in the future by implementing this concept.
- Are there allergies to anaesthetics?
There is no accumulation of allergies only because we now approach closer to the target region! The allergic effect of the metabolites with ester anaesthetics is known; this is also a reason for avoiding this class of materials. Amide anaesthetics show the best properties (these include articaine and lidocaine). If a patient exhibits a reaction to sodium sulphite, which is required for stabilisation of adrenalin, the dermatologist should be consulted and in justified cases should lead to the use of anaesthesia material which contains no vasoconstrictor. We only achieve a period of effectiveness of 20 minutes with these preparations, but nevertheless a sufficient depth of action is ensured. Other preservatives, as available in large bottle packages for example, do not need to be considered in syringe cartridge systems.
- The risk of contamination is a subject of on-going discussion. What is the situation with Anesto in this respect?
We apply a resilient concept prior to surgical procedures. Preoperative prophylaxis, rinsing with Chlorhexamed 0.1% and a single shot antibiotic has stood the test of time. No incidents have occurred in the past 3-year application period. But we work in a region easily accessible by the immune system. What is less well known is the fact that the anaesthetic articaine itself shows bacteriostatic and bactericidal properties.
- Is DVT (Digital Volume Tomography) necessary for safely performing intraosseous anaesthesia?
The radiation dosage as well as the costs for DVT are far too high to justified this. Of course, the local thickness of the cortical bone can only be represented with a three dimensional imaging technique. Since the introduction of computer tomography, many studies have been published that illustrate that we find a cortical thickness of 3 mm in regions 6 and 7 of the mandible. Only in 2 - 6% of all cases do we have values above 3 mm to 5 mm. The most important thing is a comparison between a two-dimensional X-ray image and the palpatory impression in order to find the recommendation injection region.
- With what speed may the anaesthetic be applied?
The tissue - i.e. the spongious bone - can only resorb a few drops per minute. An excessive injection quantity does not correspond to a higher resorption speed. Excessive injection pressure, as well as excessive injection volume, can only contribute to tissue damage.
- Do you have to use a new needle for a new injection site?
I would recommend it. This is even though the needle tip, with its length, diameter and the grinding profile, has been developed such that deformations of up to 360 degrees can be detected. This also constricts the lumen of the needle. The risk of needle fracture and needle blockage rise enormously. The selection of the exact rotation speeds (maxilla 15,000 rpm, mandible 25,000 rpm) and immediate implementation of the recommended maximum speed avoid blockage. With slow rotation, large bone chips and blood stick together and block the reduced needle lumen!!
- Are there contraindications for the use of Anesto?
On this question, I would rather ask you to refer to the first four questions in relation to the Anesto application concept and the others more in relation to the anaesthetic: endocarditis patients, patients with coagulation disorders, patients with bisphosphonate therapy, immuno-suppressive therapy, non-treated glaucoma patients, cocaine consumption patients are contra-indicated.
- Are there any billing tips?
The new German scale of fees for dentists (GOZ), as well as the valuation scale for practitioners (BEMA), have no special billing item. In the German medical fee schedule (GOÄ) something else is surely meant with bone punction and intraosseous infusion. The new GOZ offers sufficient room for manoeuvre with Paragraph 2 and subparagraphs such that agreement of the order of 25 to 40 euros can be made.
Implantological patient case
Preparation: Sterile assembly of the Anesto handpiece
Person 1 = unsterile, blue gloves (e.g. assistant)
Person 2 = sterile, skin-coloured gloves (e.g. doctor)