Conservative and Endodontics MCQ Answer 2

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The correct answer is e. 1, 3, 5 as can be determined from reading of the below phases I-III of the balanced force technique.

The balanced force technique uses instruments in a step-back manner to initiate preenlargement of the canal and gain access to the apical third rapidly. This involves three distinct phases as follows:

Phase I-file insertion. As advocated by Roane, the balanced force utilizes the newer K-file design called the Flex-R-File (Rhomboid). Recently, NiTi files have been recommended for use as well. The file is inserted and reciprocated by the handle in a back and forth motion until it feels snug. The handle of the file is then turned 45-90 degrees, CW rotation is used to draw the instrument down, which moves the cutting blades deeper into the canal, and engage dentin.

Phase II-file cutting. Two forces are applied simultaneously on the file handle. The file is rotated CCW while pushing apically. When rotated CCW, the tendency of the file backing out of the canal is “balanced” by the force of the file being pushed into the canal. One will often hear a clicking sound as the dentin is cut or sheared off of the canal walls. After the first cutting cycle, the file is extended slightly deeper into the canal as in Phase I. Phases I and II can be repeated up to 2-4 times.

Phase III-flute loading. The dentin cut in the Phase II lies in the interblade spaces of the file and also in the canal spaces apical to the file. The debris is removed by rotating the file CW and pulling coronally. Flute loading never causes the file tip to advance apically because of the balanced force of the file being lifted out of the canal. Two or three rotations are all that are required to fill the apical flutes with dentin mud. Hence, the file should be withdrawn.

Three advantages of balanced force using NiTi are as follows:

1. File cutting occurs at the apical extent of the file and not along it’s length. This increases the control of the file.

2. The safe-ended file tip stays centered in the root when activated in the Phase II file cutting.

3. It is not necessary to pre-curve the files to simulate canal anatomy, but, rather used straight as they were manufactured. The metallurgy and method of use cause the file to stay centered in the canal and guides the files into most curvatures.

Cohen S, Burns RC. Pathways of the Pulp. 8^th Ed. (2002). CV Mosby, St. Louis, MO.

p. 268.