Please activate JavaScript!
Please install Adobe Flash Player, click here for download
ePaper created 2016-05-18, 11:28:18 | version 1.38.0
| opinion endodontic instrumentation 22 roots 2 2016 As a practicing endodontist and manufacturer of endodontic instrumentation systems, it is fascinat- ing to me to observe the initial evaluation of greater tapered rotary NiTi instrumentation as a paradigm improvement over traditional manual techniques morphintoafarmorecautiousviewwheremoreand more evidence documenting its deleterious effects on the dentin is becoming increasingly evident. To support that observation, research has found a correlationbetweentheuseofgreatertaperedrotating NiTi and the production of dentinal micro-cracks.1–4 Researchhasalsofoundadecreaseinresistancetover- ticalfracture;asthetaperofthepreparationsincrease, acleargapbetweentheactualpulpalanatomythatex- ists and the tools used to cleanse and shape them for obturation.ItwasnotedbythelastpresidentoftheAAE thathehasseenagreaternumberofverticalfractures overthepast20years,atimeconsistentwiththeintro- ductionofgreatertaperedrotaryNiTiinstrumentation. His observations were supported by a large number of endodontistspresentatthismeeting. It is difficult to dismiss the reality that rotation of instruments within curved canals leads to torsional stress and cyclic fatigue, the two factors responsible forinstrumentseparation.Toreduceinstrumentsep- aration, dentists have learned to do the following: 1. Establish straight-line access in the mesio-distal plane. 2. Use a crown-down technique that minimizes in- strument engagement along length. 3. Employheat-treatedNiTithataremoreresistantto cyclic fatigue. 4. Employ the instruments only once. 5. Create a more instrumented glide path prior to the use of rotary NiTi. 6. Remain centred when negotiating to length. 7. Use the instruments in interrupted rotation rather than continuous rotation. 8. Reduce the dimensions of the final canal prepara- tion. The above techniques and strategies are employed to reduce the stresses that occur in the instruments as they rotate within the confines of the canal. The emphasisisplacedonmaintainingtheintegrityofthe instrumentwithminimalthoughtgiventotheimpact theyhaveontheintegrityoftheremainingrootstruc- ture. Straight-line access is purchased at the expense of removing additional amounts of coronal tooth structure.Crown-downpreparationssignificantlyin- crease the amount of coronal dentin removed so the instruments will contact a reduced amount of canal lengthatanyonetime.Heattreatmentisatechnique thatincreasesthelifespanoftheinstrumentwithout a comparable increase in the life span of the dentin, a tissuethatisnotamenabletotechnologicalimprove- ments at present. The instruments may be used once, but the impact ofstressondentiniscumulativewhethernewinstru- ments are employed or not. A single instrument will simply work longer in a canal to achieve its goals of cleansingandshapingthananyoneinstrumentused with a multiple sequence technique. Fig.1: 02 tapered stainless steel relieved reamers.(Photos/Provided by Dr Barry L.Musikant,DMD) Relieved reamers and the 30-degree reciprocating handpiece Author: Dr Barry L. Musikant, USA Fig.1 22016