torsional properties of nickel titanium and stainless steel files

torsional properties of nickel titanium and stainless steel files

Vol. 19, No. 4, April 1993 AAE Abstracts of Papers 193 (Abstract #30, continued) (Abstract #32, continued) was used to make post-space, leaving a...

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Vol. 19, No. 4, April 1993

AAE Abstracts of Papers

193

(Abstract #30, continued)

(Abstract #32, continued)

was used to make post-space, leaving approximately 5 mm of guttapercha. Five of these teeth and apices completely sealed with nail polish as negative controls. The remaining 5 teeth were prepared, but unobturated as positive controls. Coronal accesses of all teeth were left open and placed in contact with a mixtu re of enriched sterile artificial saliva and mixed bacterial inocula (S. anoinous, A. viscosus, and L_. caset.), which is changed every 3 days. Root apices were submerged in a phosphate-bufferedsolution and are sampled every 3 days for the presence of penetrating bacteria. Results show that all positive

With final files in place, the specimens were reradiographed. Initial and final radiographs were enlarged and traced on Ceph. paper. Pre and post file angles were measured. Deviation from original curvature was compared within each specimen and between the three groups. The results showed no significant differences between the techniques.

controls exhibited leakage at 3 days. At 21 days, experimental teeth have shown no bacterial penetration. Supported by the Research and Education Fou ndation of the AAE.

Abstract #31 - Effect of ultrasonic vs. rotary apical preparation on in vitro leakage of bradykinin. G.R. Crane*, K.M. Hargreaves University of Minnesota, Minneapolis, Minnesota Use of an ultrasonic (US) apical preparation technique has been advocated recently, although little data exists on the efficacy of this method. In the present study, we compared US preparations to standard rotary preparations (RO) for in vitro apical leakage past three different types of restorative materials (amalgam (A), IRM, and super EBA (EBA)). In contrast to synthetic dyes, [125]l-bradykinin (BK) leakage was measured; BK is an endogenous mediator of chronic inflammation. Human anterior teeth (n=88) were instrumented and obturated with gutta percha and Roth's sealer. Apicoectomies and retrofillswereperformed according to standard methods; the ultrasonic CT4 retrotip (Excellence in Endo., Inc) was used according to manufacturer's instructions. BK (ca. 75,000 CPM/5uL) was added to a space coronal to 4mm of remaining gutta percha. A 2X3 experimental design evaluated all 6 combir~ationsof preparation method and material (n=12/group), with additional positive and negative controls. Teeth were placed in 1mJof Locke-Ringers buffer for 1 hr samples over an 8 weekperiod. DatawereanalyzedbyANOVA )nvitroassaysensitMty was demonstrated by a significant difference in BK leakage between the positive controls as compared to the negative controls (p < 0.01 ). By9 hours after administration, levels of BK leakage in the US/A group were 43% greater than levels in the RO/A group; the corresponding amount of BK leakage in the US/EBA group was 79% greater than levels in the RO/EBA group. In contrast, the 9 hours leakage for US/ IRM was 40% less than levels for the RO/IRM group. At later time points, BK leakage rates were similarfor all groups. The results suggest

that long term leakage apical leakage rates of BK, an inflammatory mediator, are similar regardless of method of preparation and material used. This study was supported in part by a grant from the Research and Education Foundation of the AAE.

Abstract #32 - In vitro comparison of three techniques for instrumentation of curved canals.

M. Kersh*, D. Staniloff, R. White, M. Goldman, J. Tenca Tufts University, Boston, Massachusetts Adequate canal preparation becomes more difficult as root cu rvature increases. Clinical techniques and instrument design/flexibility are critical to successful preparation. Traditional curved preparation utilizes a step-back/coronal flare procedure. The Balanced Force technique is representative o| modification in technique and instrument design. Recently, nickel-titanium instruments used in a rotational manner have been advocated as superior to prepare curved root canals. This study compared these techniques, instruments and their ability to maintain original canal curvature during preparation. Ninety curved mesial roots (190 canals) of lower molars were embedded in acrylic. Clinical crowns were removed at the C EJ #15 files were placed in each mesial canal and the samples were radiographed in a manner allowing subsequent identical exposure. Two operators enlarged both canals to an apical size of 30 with 1 of the 3 techniques: a) K-file, "traditional", b) Balanced Force, c) nickel-titanium engine driven files.

Abstract #33 - Flexibility/torsional properties of nickel titanium and stainless steel files.

G.W. Brankin*, C.S. Wenckus, S.H. Ashrafi University of Illinois, Chicago, Illinois This study was conducted to compare the flexibility and torsional propertiesof the following files: Brassellar nickel titanium K-files, Flex= R, Flex-O, K-Flex and Centra Flex-file, Sizes 10-40 were tested. Flexibility and torsional properties were determined utilizing the Maillefer Torsiometer by following procedures outlined in ANSI/ADA Specification No. 28. Flexibility of files was determined by deflecting the file 45 ° and recording amount of force in gm.cm. Torsional tests were completed in clockwise and counterclockwise rotation to the point of breakage. Number of degrees rotated and force just prior to breakage was recorded. Data was then analyzed by Analysis of Variance (ANOVA) and two multiple group comparison tests. Flexibility and torsional results varied per size evaluated. General order of flexibilityfrom most to least is NIT/, Flex-O, Flex-R, Centra Flex and K-Flex. Torsional results also varied with sizes tested, but generally, K-Flex and Centra Flex-file performed better than NIT/, Flex R and Flex-O. This study was completed as partial fulfillment of requirements for a Certificate in Endodontics, College of Dentistry, University of Illinois at Chicago.

Abstract #34- Comparison of hand and hand/sonictechniques with an alternative instrumentation system. K.A. Zakariasen', K.L. Zakariasen, M. McMinn Dalhousie University, Halifax, Nova Scotia and Marquette University, Milwaukee, Wisconsin Research has shown that hand and hand/sonic enlargement techniques can result in properly shaped canals. This research is designed to compare curved canals shaped by step-back and hand/sonic filing (A,B) with those shaped by a hand/mechanical technique (C, D, E, F) using 4 different file combinations in an Endo-Lift contra-angle. The six groups studied were A) Step-Back Hed., B) Hed./Sonics, C) Hed./ Endo-Lift (15,35 K-flex), D) Hed./Endo-Lift (15,35 Hed.), E) Hed./Endo Lift (15 K-flex, 35 Hed.), F) Hed./Endo-Lift (15, 25, 35 Hed.). Sixty#101 Endo-vu blocks were accessed randomized into 6 groups and preflared to 20 mm with hand files, hand/sonics or hand/Endo-Lift. Apical preparations were completed to #25 at 23 mm. Canal flaring was continued with step-back, sonic or Endo-Lift filing until a D11T spreader would freely penetrate to 22 mm. One operator prepared all canals and instrumentation times were recorded. Canal preparations were randomly evaluated blind for apical transportation, ledge formation, and hourglass shaping of the canal. The mean preparationtimes range from 7.1 to8.2 min. with no significant differences (p = .05) being observed. No ledging occurred in any groups. Some occurrences of apical transportation and hou r-glass shaping were observed, but these were infrequent and no significant differences (p = .05) were observed betweengroups. Undertheconditionsofthisstudy, theresultsindicate

that step-back, hand/sonic and hand/Endo-Lift techniques can all provide satisfactory canal preparations with no or minimal/edging, apical transportation and hour-glass shaping of the canal space. Abstract #35 - Computerized analysis technique vs two conventional manual analyses of canal curvature.

L.E. Peacocke*, K.M. Hargreaves University of Minnesota, Minneapolis, Minnesota It is difficult to determine the effects of instrumentation on root canal angulation due, in part, to the inherent variability of manual protractor measurements. This study compared a newly developed computer