Dental Tribune United Kindom Edition

July 30 - August 5, 201214 Endo Tribune United Kingdom Edition inadequate canal enlarge- ment, missed canals, ledging, canal transportation, over- instrumentation, as well as obstruction of the canal by debris or separation of instru- ments. Failure to use or us- ing too small a volume of an appropriate irrigant solution, such as sodium hypochlorite, is an iatrogenic error. Full-strength six per cent sodium hypochlorite been shown to be highly antimicro- bial and able to dissolve tissue and disrupt bacterial biofilm.20, 21 These qualities in an irrigant are ideal for the debridement of residual bacteria and tissue debris. The use of a rubber dam to isolate the treatment field is the standard of care for endodontic treatment. Fail- ure to use a rubber dam may be a fundamental contribu- tor to post-treatment disease. The following case illustrates the ability to overcome pri- or incomplete treatment to achieve successful healing (Figs 3a–c). Clinical example Restorative failure is a com- mon cause of post-treatment disease. Failure to place an ef- fective permanent access res- toration in a timely manner can allow for bacterial entry into the root-canal system by coronal leakage. Submarginal leakage on a crowned tooth can also allow bacterial entry to occur. Decay in a previous- ly treated tooth is another source of bacterial contami- nation. Structural damage to a tooth by trauma, cracking or fracture may provide an entry point for bacterial contamina- tion of the canals. Our patients are responsible for their own oral health and must com- mit to effective oral hygiene techniques. Failure of the pa- tient to perform effective oral hygiene can result in the fail- ure of even the most well ex- ecuted root-canal and restora- tive treatments. With the bacterial chal- lenges clinicians have to face, retreatment techniques must be capable of effective elimi- nation of bacteria and their substrates. The use of a den- tal operating microscope and ultrasonic instruments allows clinicians to uncover all ex- isting canal anatomy prop- erly to ensure that they are able to cleanse the root-canal system completely. The fol- lowing clinical case (Figs. 4a & b) illustrates the extent of the canal space left untreated in the initial root-canal ther- apy by not opening the me- siobuccal canal adequately and not locating and cleansing the hidden second mesiobuc- cal canal. Endodontic ultrasonic tips are highly efficient at remov- ing core build-up material, paste fills, posts and silver- point fillings, as demonstrated in Figure 5. These instruments allow clinicians to conserve root dentine by providing excellent visibility under a dental operating microscope, thereby greatly improving the ability to retreat canals (Figs. 6a–c). A heat source such as a System B tip (Axis, SybronEn- do) is efficient for the removal of gutta-percha and resin ma- terials from the coronal third. Hand and rotary files can re- move root fillings and shape canals to appropriate working lengths. Current NiTi rotary files are highly flexible and resistant to separation and allow us to mechanically en- large the apical third of root canals safely and efficiently without alteration of the natu- ral canal morphology, which allows ef- fective irrigation to reach the complex a p i - cal root- c a n a l anatomy where bac- t e - ria are able t o h i d e and resist debride- ment. Once the canals have been located and instrumented, the ability to irrigate becomes essential to successful treat- ment. The irrigant solutions target the bacteria we are trying to eliminate. While sodium hypochlorite is a po- tent and proven antimicrobial and tissue dissolver,22 two per cent chlorhexidine has been shown to prevent the adhe- sion of E. faecalis to dentine.23 EDTA 17 per cent is often used as an effective smear- layer removal agent.24 There- fore, mechanical debridement and canal instrumentation provide a pathway for copious chemical irrigation deep into the canal. Passive ultrasonic irriga- tion allows clinicians to place an irrigant solution into the pulp chamber and activate it as it is carried down to the api- cal end of the root canal. The IrriSafe tip from Satelec (Ac- teon; Fig. 7) is a non-cutting ultrasonic file that is placed into each canal and is moved up and down in the canal for three cycles of 20 seconds. Passive ultrasonic irrigation has been shown to irrigate lateral canals better at 4.5 and 2mm from the working length of canals as compared with needle irrigation alone.25 It has been demonstrated that passive ultrasonic irrigation can remove dentine debris in a canal up to 3mm in front of where the tip extends api- cally in straight or curved canals.26 This evidence shows that an effec- tive flow of irri- g a - tion can assist in the c l e a n s - ing of t e e t h in which ca- nal altera- tion occurred during the initial root-canal treatment. The following silver- point case (Figs. 8a–c), with a large distal post and apical transportation in the mesial root, demonstrates the successful healing of post-treatment disease when proper disin- fection has been ac- complished. This case illustrates the reason that retreatment is the primary treatment op- tion for post- t r e a t m e n t disease. Once debridement and disinfection have been completed, appropriate Fig. 6a: Tooth #3 with silver-point fillings in the mesial root and a large post in the distal root. A large radiolucent periapical lesion is evident on the distal root Fig. 6b: Post-op radiograph Fig. 6c: Thirteen-month follow-up radiograph. (Courtesy of Dr Brett E. Gilbert) ‘Failure to use or using too small a volume of an appropriate irrigant solution, such as sodium hypochlorite, is an iatro- genic error’ Fig 8a: Tooth #30 with silver-point fillings in the mesial root and a post in the distal root. The mesial root-canal preparations are transported towards the mesial. There is a radiolucent periapical lesion. Fig. 7: IrriSafe tip from Satelec page 13DTß