Sterilise this

The ability to properly shape and debride root canals has been made a good deal easier with the advent of rotary driven Ni-Ti files. The problem remains that due to the inherently complex internal architecture of the root canal system it has been problematic to ensure adequate removal of pulpal remnants and any associated biofilm. Research shows it takes 30 minutes immersion in dilute hypochlorite to disinfect the interior of a root canal to the depth of 0.5mm. Bacteria can colonise the interior of the root canal to the depth of 1mm or more and by communication through periodontal pockets and lateral canals a biotica can be present in areas not amenable to conventional instrumentation and disinfection. Root canals have complex systems of side tributaries radiating from the principal root canal and when we try and irrigate the apical area there may be air and fluid entrapment. Irrigants are not likely to properly wash out the apex and forceful irrigation can be associated with fluids being expressed through the apex with potentially serious adverse consequences. It is also a problem that some of the pathogenic bacteria are pretty tough to destroy: Enterococcus faecalis for instance is multi antibiotic resistant and can form a viable spore in the presence of hypochlorite or calcium hydroxide. Infected root canals often have had bacterial colonies that have been subject to several courses of antibiotics and this can result in resistance to further antibiotic chemotherapy. In view of these many problems it is not surprising apical radiolucency is a frequent asymptomatic finding on periapical radiographs.

Faced with the many technical challenges to successful endodontic therapy the ability to predictably provide long term stable results is open to question. Short term success can be an illusion and few clinicians have the luxury to follow up their patients long term. There is a substantial body of literature concerning the application of lasers as a tool to sterilise the interior of root canals. The technique essentially involved generating sufficient heat within the root canal system to effectively kill off any viable bacteria. The issue remained of the inability to properly debride root canals to the apex and to clear out any accessory or lateral canals. Recently there is a whole new line of thinking in the application of lasers in endodontics which use a set of specially shaped tips for their erbium laser, the Waterlase MD. The new radial firing tips are cut at the end in the form of a cone and when the laser is fired it generates a corresponding radial wave of laser light at 2780nm. This is rapidly pulsed at 50 cycles per second; a shockwave is generated inside the fluid introduced into the canal. Each pulse causes the water at the tip of the laser to expand 1600x in a 50th of a second and the resultant shockwave ricochets off the wall of the root canal. As the laser is rapidly pulsed there are many different wave fronts which interfere with each other resulting in amplification. This storm of activated water rapidly penetrates the entire root canal system such that you can clear out debris from otherwise inaccessible areas up to and including the apical delta, and it is only necessary to place the tips to a depth of 4mm or 5mm from the coronal end of the canal to achieve this effect. Research shows this effect of hydrophotonic activation can kill 99.7 per cent of bacteria to a depth of 1mm within the root canal walls right up to the apex. Following use of the new technique it is a frequent observation on post operative radiographs that the lateral canals have been opened up and cleaned, thus permitting the flow of root canal sealants. 

Biolase recommend a two phase treatment: phase one is to debride the canals and the second is a heat phase to sterilise the canal. The endodontic radial firing tips are manufactured in zirconium in diameters corresponding to a size 20 and a size 30 file. The zirconium at this diameter is flexible enough to follow to a limited degree the curvature of a canal. Research shows that there is little if any risk of pumping material through the apex in a mature tooth and the technique is simple to learn and to apply. I use the laser in this application as an additional step along with my routine procedures in preparing the canals. The canals end up beautifully clean and I have found infected canals respond very quickly to treatment. I enjoy a very high degree of resolution of infections with few if any post treatment problems. The laser is also of great benefit as a tool in endodontic surgery. I usually do the entire procedure from making the incisions for the flap, any bone removal and the apicectomy including removal of any infected apical tissue solely with the laser. There is remarkably little bleeding at the time of surgery and the healing profile is remarkable as there is very much reduced post treatment pain and swelling; to date I have enjoyed 100 per cent success with my apical surgeries.  In my view the Waterlase MD with its endodontic applications offers a new gold standard in endodontic treatment. Biolase have an online educational resource available at www.biolase.com/events where you can see a detailed description of laser assisted endodontics.

For more information visit www.henryschein.co.uk or www.biolase.com

Mark Cronshaw regularly lectures for Henry Schein Minerva, covering a wide range of topics on laser dentistry.  Courses will be taking place across the UK in 2010 on the following dates:

 A practical introduction to lasers in dentistry: Two day intensive course

For more information visit www.henryschein.co.uk and click on ‘education’.