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May 24-30, 201022 Clinical United Kingdom Edition internal micro-morphology of the root complex were epi- demiologically similar, then “imprinting” of the canal preparation would be logical. Unfortunately, such is not the case (59) . Figure 16b shows how the use of hand files in the apical third can alter the prelimi- nary shape created by the NiTi files. Hand files have a .02 ta- per (along the shaft of the file, the diameter increases by .02 mm per mm of length - .20 file with 16 mm of flutes would be measure .52 mm at the coro- nal end of the flutes). In the example shown, a #20 file is positioned at the minor apical diameter. Careful positioning of a series of file within the last mm can produce a .2 mm or 20 per cent taper with no undue disruption of the native anatomy. Schilder’s precept for shaping was to keep the api- cal foramen as small as prac- tically possible. Whatever file approximates the minor apical diameter, in conjunction with hand filing, the apical control sone created will enhance the apical seal as the rheologic vectors of compaction and condensation have a greater lateral volume of displacement at the terminus. Fashioning a risk assess- ment algorithm If the biologic parameters that mandate endodontic success are adhered to, in almost all cases, treatment outcomes will be successful. The endodontic implant algorithm processes the array of contributing fac- tors leading to endodontic failure, in order to determine whether to implement a re-en- gineered endodontic approach or to extract and replace the natural tooth with an osseo- integrated implant. It finds the greatest common divisor among the degree of coronal breakdown of the involved or adjacent teeth, the quality and quantity of the bone support and tissue condition, the en- gineering demands to be born by the tooth or teeth in ques- tion and assesses the occlusal scheme and the patient’s aes- thetic and functional expecta- tions of treatment. Thereasonsfortoothextrac- tion may include, but are not limited to, crown to root ratio, remaining root length, peri- odontal attachment lev- els, furcation status, peri- odontal health of teeth adjacent to the proposed fixture site and non-restor- able carious destruction. In addition, the clinician must consider questionable teeth in need of endodontic treatment, teeth requiring root amputa- tions, hemi-sections or ad- vanced periodontal procedures with a questionable prognosis and pulpless teeth fractured at the gingival margin with roots shorter than 13mm. These teeth will require endodontic treatment, crown lengthening, post/cores and crowns; how- ever, their longevity is very much in doubt with these pa- rameters (60) . Practitioners are ethically obligated to inform patients of all reasonable treatment options. It is the patient’s atti- tude, values and expectations that are integral to the risk assessment algorithm. Poor motivation to retain a tooth mandates extraction, not clini- cal intervention whereas high motivation advocates non-sur- gical intervention or surgery. The process of planning, pres- entation and acceptance of dental treatment plans is al- ways dominated by the dual- ity of emotion and pragmatism associated with cost. Where it becomes specious is the side- by-side dollar comparison of restoring a natural tooth or placement of a fixed bridge et al in contrast to ortho- biologic replacement of a debilitated tooth. Far too often the compari- son of purported treatment outcome percentages are based upon corporate affilia- tion and/or fiduciary bias, or are simply too narrow a pa- rameter to suggest comparable alternatives. With the treat- ment options available to an experienced endodontist, only a very few structurally sound teeth need be removed. DT Fig 16b – Modification of taper in last mm of the apical terminus, exaggerates the “constric- tion” or minor apical diameter. Thermo-labile vertical condensation has been shown to enhance successful endodontic outcomes. The matrix effect of the apical control zone enhances the gravi- tometric density of the required hermetic apical seal as well as enabling more material to flow into the region to occlude fins, cul-de-sacs, deltas and lateral arborisations. About the author Kenneth S Se- rota, DDS, MMSc graduated from the University of Toronto, Faculty of Dentistry in 1973 and was awarded the George W Swit- zer Memorial Key for excellence in Prosthodontics. He received his Certificate in Endodontics and Master of Medical Sciences De- gree from the Harvard-Forsyth Dental Center in Boston, MA. The founder of ROOTS – an online educational forum for dentists from around the world who wish to learn cutting edge endo- dontic therapy, he recently launched IMPLANTS (www.rximplants.com) and www.tdsonline.org in order to provide a clear understanding of the endodontic/implant algorithm in foun- dational dentistry. page 20DTß References 1. Farzaneh M, Abitbol S, Lawrence H, Friedman S. Treatment Outcome in Endodontics—The Toronto Study. Phase II: Initial Treatment. J Endod 2004 May;30(5):302-309. 2. Bero L, Rennie D. The Cochrane Collaboration. Preparing, maintaining, and disseminating systematic reviews of the effects of health care. 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Histological evaluation of the effectiveness of five instrumentation techniques for cleaning the apical third of root canals. J Endod 1997;23(8): 499-502. 58. Serota KS et al. Predictable endodontic success: The apical control zone. Dentistry Today May 2003;(22)5:90-7. 59. Peters OA, Peters C, et al. ProTaper rotary root canal preparation: effects of canal anatomy on final shape analysed by micro CT. Int Endo J February 2003;(36)2:86-92. 60. Becker W. Immediate implant placement: Diagnosis, treatment planning and treatment steps for successful outcomes. J Calif Dent Assoc 2002;33:303-310 Fig 16a- The ProTaper Universal System comprises two shaping files that address the planes of geometry of the coronal and middle thirds of the root canal space. There are five finishing files that include tips sizes, 20, 25, 30, 40 and 50. Tapers range from .06 to .09 through the series. A thor- ough understanding of the metrics is essential for the preparation of the myriad variations in inter- nal micro-morphology of the root canal space and the assurance of minimal iatrogenic impact.