To analyze the mechanics of the balanced force concept for instrumentation of curved canals. Disagreement of Roane’s proposed mechanism; here, they suggested compressive force allows success with balanced force technique
- The value for the average canal curvature, as reflected by a Mean Maximum Height of Curvature (MMHC), was derived by examining 50 mand molars MB canal radiographically
- Flex-R files, sizes #10-70, 21mm long were tested. The plastic handle was secured in a clamping device contacting a perpendicular, glass platform scale, and gradually increased force until it reached MMHC and the compressive force recorded
- 6 endodontists and endo residents using #35 in extracted human teeth with balanced force technique recorded the apical force applied during instrumentation
1.The MMHC was 1.86 mm. There was a significant difference between the compressive force required to bend the files to MMHC 1.86 mm, except between 10, 15, and 20. The #35 file required a mean force of 1.14 N to produce this curve
2.The forces applied by the six clinicians using a #35 file and the balanced force technique ranged from 3.72 N- 9.97 N, with a pooled average of 5.70 N. This average is well above the forces necessary to produce this curve up to a #60 file
An explanation of balanced force technique success may be that it places flexible files in compression, causing them to preferentially bend in the direction of least possible resistance, i.e. that dictated by the natural canal curvature.