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ePaper created 2017-06-21, 10:00:36 | version 1.38.0
| opinion root canal disinfection Cleaning is key Author: Aws Alani, UK Completely disinfecting the canal system is chal- lenging when all factors are considered. If we are looking at the nano level there are approximately 76,000 dentinal tubules per square millimetre of den- tine. Each of which can harbour a colony of bacteria. Then there may be inaccessible anatomy such as lat- eral canals, apical deltas or fins. These are factors that need considering outside of canal curvatures that may or may not be entirely visible in the plane of the radiograph. It is clear that outside of the contact our files make with the walls of the root canal there needs to be chemical disinfec- tion to further reduce bacterial load. Irrig- ants disinfect as well as lubricate instru- ments and they dis- solve the pulp. Sodium hypo chlo rite has been the mainstay irrigant for decades. During the 1980s, Bystrom and colleagues investigated the effect of mechanical instrumentation with and without adjunctive use of hypochlorite. They found, unsurprisingly so, that when compared to pure mechanical instrumentation, the use of hypo chlorite in combination with hand filing signif- icantly reduced bacterial load. As such chemome- chanical instrumentation was shown to be crucial for endodontic success. They compared irrigation with saline, 0.5 % and 5 % hypochlorite over a se- quence of 5 appointments. Interestingly they found no difference in the reduction of bacterial load be- tween 0.5 and 5 % hypochlorite. Despite what was likely to be a comprehensive protocol for these teeth, 7 of the 15 specimens in this study still had bacteria that they could grow at the end of treatment. The presence of cultivable bacteria does not necessarily mean we have failure—it merely means that there may be a cohort of bacteria that have resisted treat- ment. Mechanical instrumentation does reduce bac- terial load by itself—this is by way of physical removal of tissues where bacteria reside, while also facilitat- ing the dispersal of the irrigant into the canal. Siqui- era and colleagues found that enlarging the canal 14 roots 2 2017 from size 30 to 40 resulted in a significant decrease in endodontic pathogens. u o m s t o S h e r tt el/ © Annareich It seems that irrigation and instrumentation are both highly inter-related in canal disinfection. Take washing your car for instance, purely covering it with soapy water and rinsing won’t remove the motorway bugs and bird produced projectiles. A good scrubbing with a sponge is needed, or if you are really serious about cleaning, a pressure washer! This begs a further ques- tion—how would your patients feel if they knew that, more or less, the same or very similar liquid they use to clean bathroom suites is the same that we use to clean the inside of their teeth? On recent evi- dence of a dentist to the “stars” appearance on na- tional TV not much—he ad- vocated using charcoal to whiten teeth, which you may be able to buy from your local petrol . c c k station for barbecues. Hypochlorite is an effective bactericidal but does not remove the smear layer. The smear layer is a mix of organic material (protein, pulp remnants, saliva, micro- organisms) with an inorganic components consisting of minerals from the dentine. The smear layer prevents bacteria residing in the dentinal tubules from being ex- posed to the irrigant as well as reducing the contact between the dentine and sealant during obturation. Hence, utilising EDTA to remove the smear layer prior to obturation but after completion of preparation and instrumentation is sensible. A penultimate rinse with EDTA then a final rinse with hypochlorite prior to drying has been advocated heavily in the literature. Bacteria and the biofilms Unlike what we once thought, bacteria do not tend to just sit alone and remote from each other. If only they were this antisocial and could be picked off one by one! Bacteria join forces and create symbiotic groups, share resources and protect each other from external influence. This is commonly known as a “bio-