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roots - international magazine of endodontology No. 2, 2016

| technique canal preparation and filling 26 roots 2 2016 Introduction With the widespread use of rotary nickel-titanium (NiTi) instruments, matched-taper gutta-percha (GP) cones of greater tapers were developed to make root canal obturation techniques easier and more predict- able,andpossiblytotheimprovequalityof3-Dfillings. Nowadays, many manufacturers produce matched- taperGPconesintendedforusewithaspecificinstru- mentation technique. Consequently, the single-cone technique has regained popularity, since a single matched-taper cone can produce a satisfactory 3-D fill,andwarmverticaltechniquesbenefitfromtheuse of a matched-taper master cone by a reduced risk of voids inside the filled endodontic space. However,thelargernumberofandvariabilityinde- sign and dimensions of commercially available NiTi instrumentsandGPconesofgreatertaperscaneasily createconfusionamongpractitioners,especiallyifus- ing instruments and cones of different brands. If the GPconesselecteddonotpreciselymatchwiththeNiTi instrumentsused,thewholeconceptfailsandinmany cases the GP cones do not reach the desired working length or do not precisely fill the apical preparation. In order to understand how matched-taper GP cones should work, it is important that clinicians be aware of the differences in size, taper, design and manu facturing process of these products. Even if these factors are usually taken in account when a manufacturerproducesmatched-taperGPconesto be used with a specific instrumentation technique, the goal of the present paper is to discuss all of these variablesandgivecliniciansabetterunderstandingof the possible clinical problems they may encounter in cone fitting and practical solutions to these. Size, tolerance and manufacture of GP cones Conventionally, GP cones are hand rolled, a manu- facturing process that is neither very precise nor consistent. Therefore, according to ISO standards, the tolerance allowed for GP cones is 0.05 mm, much larger than the tolerance allowed for endodontic in- strumentsproducedbygrindingortwisting(0.02 mm). This has always been a problem in endodontics and it explains why correct fitting of the master cones in all techniques (single-cone, lateral condensation, warm vertical condensation, continuous wave of obtura- tion) has always been described as a fundamental step in the procedure. WiththeconventionalISO0.02-taperedcones,the problem was mainly related to the lack of precision of the tip of the GP cones. Therefore, GP tips needed to be manually adjusted to fit the apical preparation with good retention (tug-back) in order to avoid underfilling or overextension of cones through the apicalforamen.Thesameprocedurewasneededfor non-standardized GP cones with feathered tips. For this reason, specific calipers and instruments to cut GP cones precisely were developed. With the introduction of GP cones of greater ta- pers, a problem related also to the taper arose. These new GP cones can be grouped into two categories: uniform and nonuniform taper. The former cones are usually marketed as 0.04- or 0.06-tapered cones, while the latter are usually marketed in association with a brand name related to a specific instrumenta- tion technique (e.g., ProTaper cones, DENTSPLY; and TF Adaptive [TFA] cones, Kerr). Development of these cones was necessary, since nowadays more NiTi ro- Matching gutta-percha cones to NiTi rotary instrument preparations Authors: Prof. Gianluca Gambarini, Dr Gianluca Plotino, Dr Nicola Maria Grande, Dr Simone Staffoli, Dr Federico Valenti Obino, Dr Lucila Piasecki, Dr Dario di Nardo, Dr Gabriele Miccoli & Prof. Luca Testarelli, Italy 22016

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