ASPECTE ALE TRATAMENTULUI BIOMECANIC DE CANAL – TEHNICA STEP-BACK. STUDIU IN VITRO

Abstract

Evaluation of post-operative root canal shape have been performed using simulated root canals in resin blocks and magnification analysis (stereomicroscope) have been used for the study. The technique selected was stepback with conventional hand stainless steel instruments. The aim of studies on post-operative root canal shape is to evaluate the conicity, taper and flow and maintenance of original canal shape and to record the degree and frequency of straightening, apical transportation, ledging, zipping, teardrops, elbows. Ideal preparation forms for the root canals can be possible without any preparation errors with circular incorporation of the original canal cross section – if the technique starts with adequately precurved negotiating files. Preparation errors (zips, canal transportation, apical perforations, elbows, teardrops, etc) can occur mostly when stainless steel hand instruments (K-file) are used for moderate to severe curved of root canals, especially K-file with cutting tips and not prebent. Ideal preparation shape without any preparation errors could be a final shape and adequate shape even for conventional hand files and step-back technique. For the first area of step back technique, even for the begining, we can usually use various prebent stainless steel hand instruments for pathfinding. In many cases, conventional hand instruments produces adequate shapes for the root canals. For this final shape, is important to use adequately precurved negotiating files. Conventional stainless stell are rigid enough that thay should be precurved to match the curvature of the canal during instrumentation. Conventional hand instruments has two basic design, Kerr-file and Kerr-reamer. Kerr-file could be used to enlarge the canal with a longitudinal filing action. Kerr-reamer may used in a same fashion, but is much more flexible instrument than K-file. Noncutting tip follow the canal better than instruments with active tips – clinically usefull element.