Fuerzas Balanceadas

0099-2399/85/1105-0203/$02.00/0
JOURNAL OF ENDODONTICS Copyright 9 1985 by The American Association of Endodontists

Printed in U,S,A.
VOL. 11, NO. 5, MAY 1985

The "Balanced Force" Concept for Instrumentation of Curved Canals El Concepto de "Fuerza Balanceada" para la Instrumentacion de Conductos Curvos
James B. Roane, BS, DDS, MS, Clyde L. Sabala, BS, DDS, and Manville G. Duncanson, Jr.,DDS, PhD

Canal curvature has always introduced complexity into canal preparation. The "balanced force concept," developed by trial and error experimentation over the past 12 yr, is proposed as a means of overcoming the curvature influence. Its concepts use force magnitudes in order to create control over undesirable cutting associated with canal curvature. Rotation is promoted as the means formaintaining magnitude as a control and counterclockwise direction of rotation provides finite operator control. Diagrammatic evaluations, mathematical calculations, bending moments, test canals, sectioned teeth, and clinical radiographs are presented to document each step of the concept. The concept comes to fruition with the introduction of a new K-type file design. La curvatura del conductosiempre representb una complejidad en la preparacion del mismo. El concepto de "fuerza balanceada" desarrollado a traves de experimentacibn pot ensayo y error durante los ultimos 12 a~os, se propone como un medio de superar la influencia de la curvatura. Sus conceptos usan magnitudes de fuerza a fin de Iograr el control del corte indeseable asociado con la curvatura del conducto. Se promueve larotacibn como medio de mantener la magnitud como control, y la direccion de rotaci6n en sentido contrario a las agujas del reloj permite un definido control al operador. Se presentan evaluaciones diagram&ticas, calculos matematicos, momentos de torsi6n, pruebas de conductos, dientes seccionados y radiografias clinicas para documentar cada paso del concepto, que se ve completado con la introducci6n deun nuevo dise~o de limas tipo K.

Root curvature is a frequent occurrence in the human dentition and when a curvature is present, endodontic
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preparation of the associated pulp canal system becomes difficult. In fact, curvature introduces such complexity that total instrumenting concepts have been developed to deal with the curved canal (1-5). Even with these, it is commonplace for a canallocated within a curved root to be enlarged to a smaller final diameter than it would be if it were located within a straight root. Justification for such alteration is simply the fact that a curvature introduces factors into preparation which, if not controlled during enlargement, will cause transportation, ledge formation, and even perforation (1-4, 6, 7). The more severe the curvature of theroot, the more one tends to reduce the intended preparation diameter in an effort to prevent irreversible damage of the canal wall. Reducing the preparation size under such circumstances appears to be logical for two reasons: (a) smaller diameter preparation means less cutting of the canal walls and consequently a lesser likelihood for expression of undesirable cutting effects and (b) smalldiameter files are more flexible and therefore less likely to cause transportation during enlargement. The curvature problem appears to be solved by small preparation diameters until one examines what that solution sacrifices in canal debridement and reliability of the final seal. Smaller preparation diameters reduce the amount of mechanical and chemical cleansing of the canal space. Several studiesappear to indicate less complete removal of debris when small nonflared preparations are used (8-10) while others relate to the flushing effect of irrigants and indicate that irrigants are not effective in washing debris from a small diameter canal (11-13). Finally, Allison et al. (14)indicate that preparation size/design has an influence upon the final seal. They found that the best seal was...