Critical analysis of the balanced force technique in endodontics.

The "balanced force" technique was introduced in 1985 and it was reported that the resistance of the dentin, as it circumferentially contacted the flutes of a file in a curved root canal, would be sufficient to override and mask any tendency of the file to straighten during rotational instrumentation. An alternative mechanism based on compressive force and file flexure is presented in this article. In a laboratory study, the apical force necessary to cause files of sizes #10 to #70 to bend and conform to an average canal curvature was determined. These measurements were then related to the apical forces applied to teeth when utilizing the Balanced Force technique in a simulated clinical setting. It was then proposed that the apically directed force necessary to prevent coronal movement of the file and to effect dentinal shearing during counterclockwise rotation placed the file in compression, flexing it to conform to the curvature of the canal. This explanation was consistent with the experimental data for the files used in this study up to size #60 for an average canal curvature and for average instrumentation forces.