7/27/2019 endo rotatorios

1/3

0099-2399/91/1711-0570/$03.00/0JOURNAL OF ENDODONTICSCopyright 9 1991 by The American Association of Endodontists

CLINICAL AIDPrinted in U.S.A.VOL. 17, NO. 11, NOVEMBER1991

The Radiographic Platform: A New Method toEvaluate Root Canal Preparation In VitroGilson Blitzkow Sydney, DDS, Antonio Batista, DDS, and Luciano Loureiro de Melo, DDS

An in vitro method for evaluating root canal prepa-ration in curved canals is presented. Based onSchneider's method, this technique makes it possi-ble to obtain the position of the instrument beforeand after instrumentation in the same X-ray film. Theuse of the radiographic platform is a valuable re-search and teaching aid.

Root cana l prepara t ion has been considered the most impor-tant phase in endodo ntic therapy. The objectives of root canalpreparation can be defined as cleaning and shaping. Thisincludes a complete debrid ment of all areas, leaving theforamen in its original position, keeping the foramen at asuitable diameter, and developing a continuously taperingconical form (1-3). When these objectives are properly metan efficient obturation of the root canal system is possible.Preparation is easily accomplished in straight canals, butwhen root canal curvatures are present i t becomes moredifficult . In narrow, curved canals the apical area is difficultto clean and shape, and there is a tendency for ledging andzipping (4). T o reduce these possibili ties various flaring tech-niques ha ve been devised. Eva luation of the efficiency of rootcana l inst rumenta t ion has been ana lyzed by means of thecommon opt ica l microscope , the scanning e lec t ron micro-scope, radiographic examination, photographic studies, rootcanal models, and, recently, the computer (5).

A problem in root canal evaluation is that the anatomicalmorpholog y and curva tures a re of ten subjec t to examina t iononly after instrumentation. Bramante et al . (5) developed amethod that permits an analysis before, during, and after rootcanal preparation using teeth in acrylic resin blocks sectionedtransversally.

Schneider, in 1981 (6), introduced a method using a pro-jector to increase the size of the tooth by 10 times. First , aline was scribed on the radiograph parallel to the tooth's longaxis. A second line was then drawn from the apical foramento intersect with the first at the point where the canal beganto leave the long axis of the tooth. The acute angle formedwas used by many authors to evaluate root canal preparation.With the use of this technique, Southar d et at . (7) analyzed

the deviation from the original position resulting from theRoane technique of inst rumenta tion .

The radiographic platform is an apparatus that enables oneto visualize the position of the inst rumen t before and afterroot canal preparation on the same X-ray film. In this wayany inadequate instrument usage can be evaluated.

T H E R A D I O G R A P H I C P L A T F O R M A P P A R A T U SThe radiographic platform is very easy to make. The nec-

essary materials are (a) a clamp, (b) a plastic ice cube mold(only one piece), (c) two lids of gutta -per cha bo xes (Kerr), (d)a plastic ruler, and (e) an adhesive cement.

First , a rectangular ice cube mold is cut and one piecedetached. One o f the gutta-percha lids is cut 3 mm from oneof its sides according to Fig. 1. Using a carbo run dum disc theruler is cut longer than the clamp diameter which must beadjusted to the X-ray tube. Th e ruler is cemen ted to the clam pas shown in Fig. 2. The second gutta-percha lid is used as abase for the ice mold. The ice cube mold piece must becemented to the ruler, the base, and the gutta-percha lid pieceas seen in Fig. 3. Once the radiographic platfo rm is assembled

570FIG 1. The necessary materials: a, the clamp; b, a plastic ice cubemold; c, gutta-perch a box l ids; and d, plastic ruler.

7/27/2019 endo rotatorios

2/3

Vol. 17, No. 11, Novem ber 1991 The Radiogra phic Platform 571

FIG 2. The ruler is cemented to the clamp and the ice cube m old tothe lid of a gutta-percha box.

FIG 3. The radiograph ic platform assembled.

F~G 4. Painted bla ck with the acrylic resin b lock in place.

it may be painted any color and connected to the X-rayequipment by the clamp which has been previously adjustedto the proper diameter (Figs. 4 and 5).

FIG 5. Connected t o the X -ray tube.

METHODOLOGY

The tooth with a curved root canal selected to be studiedis immersed in clear autocured acrylic resin using anotherplastic ice cube piece of the same size, making a block, sothat the crown will stick out. There are several techniques tohold the tooth in the correct position until it is completelyfixed in the resin. One of the techniques is to attach it to themiddle of a toothpick with wax. The two ends of the toothpickwill rest on the edges of the ice cube mold.

After access, a file is introduced into the root canal in orderto determine the correct working length. The resin block withthe tooth is placed in the radiographic platform and an X-rayfilm is exposed and developed. Once the proper workinglength is determined, another X-ray film is exposed but leftin the radiographic platform. It is not developed now and itwill be used later to overlap images.

The resin block must be taken out of the apparatus andthe canal prepared according to the technique to be tested.When it is fully instrumented, the resin block is placed in theradiographic platform again. The last file used is kept insideof the canal and a new exposure is made on the second X-rayfilm.

The most impor tant point to be carefully observed to assureaccuracy when superimposing the last image over the first onthe second X-ray film is that after the first exposure the filmhas to be kept steady in the platform. There is no problemwith the X-ray beam because it is guided by the clamp.

The exposure time used for both incidences is 5/1o s. Thedeveloping time must be shortened in order to prevent dark-ening of the film. These factors have to be adjusted accordingto the characteristics of the X-ray film and the X-ray machineused.

After developing the X-ray film it can be framed for a slideprojector so that it will be easier to detect ledging or zippingand to check i f the instrumentation damaged the thickness ofthe mesio-distal walls of the root canal.

The original position of the instrument as well as thepostinstrumentation portion will be seen in the same film(Figs. 6 and 7).

7/27/2019 endo rotatorios

3/3

572 Sydney et al.

FIG 6. The over lapp ing image o f the two f i les ind icates desi rab lei ns t r umen t usage .

Journal ofEndodonfic s

detect the presence of ledging and zipping and to analyze theac t ion of the inst rument on the th ickness of the mesio-distalwalls of the ro ot canal.

Similar devices were used before by Southard et al . (7) in1987, by Bastos Filho (8) in 1989, and rec ently by Mora es etal. (9). The idea was to obtain the same angularity in order touse Schneider's method. Schneider (6) used two X-ray filmsto de te rmine the degree of cana l curva ture before and a f terroot cana l prepara t ion . The proposed method makes i t pos-sible to have the position of the file at the beginni ng and atthe end of inst rumenta t ion in the same f i lm. Devia t ions andimperfections as ledging and zipping are directly observed. Ifthe canal is correctly prepared, the two files must be over-lapped in the apical third (Fig. 6). If not, since deviation isclearly seen, an angle will be detected.

I t i s advisable to e l imina te o ther roots when working onupper molars in order to avoid image overlapping (Fig. 7).

The use of the radiographic p la t form can prove to be auseful teaching aid and it may be valuable for endodonticresearch.

Dr. Sydney is adjunct professor, Department of Endodontics, Dr. Batista isa volunteer clinical instructor, Departme nt of Endodontics, and Dr. de Melo ischairman, Department of Endodontics, School of Dentistry, Federal Universityof Parana, Parana, Brazil. Addr ess requ ests or reprints to Dr. GUson B. Sydney,Lua Benjamin Constant 145, 1 Andar, S-2 CEP-80060, Curitiba, Parana, Brazil.

F~G 7. The f i les do not su per imp ose a t the ap ex due to incor rect useof the instrument.

D I S C U S S I O NMany methods have been descr ibed to eva lua te the root

cana l prepara t ion . The use of the radiographic p la t form is apractical and informative one because it makes it easy to

References

1. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am1974; 18: 269- 96.2. Abou-Rass M. Endodontic preparation and filling proc edures. Los An-geles: West C oast Arts, The California Dental Institute for Continuing Education,1986.3. Calhoun G, Montgomery S. The effects of four instrumentation tech-niques on root canal shape. J Endodon 1988;14:273-7.4. Abou-Rass M, Frank A, Glick DH. The anticurvature filing method toprepare the curved root canal. Am Dent Assoc 1980;10 1:792-4.5. Bramante CM, Berbet A, Borges RP. A methodology for evaluation ofroot canal instrumentation. J Endodon 1987 ;13:243-5.6. Schneider SW. Comparison of root canal preparation in straight andcurved canals. J Oral Surg 1971 ;32:271-5.7. Southard DW, Oswald RJ, Natkin E. Instrumentation of curved molarroot canal with the Roane technique. J Endodon 1987;13:479-89.8. Basto s Filho E. Analise "in vitro" d a vada~:~o angula r e da configura~:~loapical quando do preparo de canals curvos corn instrumentos de tipo eproced~ncia variados [Tese Mestrado]. S&o Paulo, Brazil: Faculdade de Odon-tologia da Univ ersidade de S&o Paulo-Brasil, 1989, 57 p.9. Moraes SH, Batista A, Arag&o EM, Heck AR. Deformacion apical condiferentes tipos de limas, di&metros y numeros de usos en canales curvos.Rev Esp Endod (in press).