To determine the incidence of ProFile fracture and the potential for bypassing in molar teeth. N= 419 MX (173) and MD (246) first and second molars in 408 patients (1457 canals). WL > 15 mm, canal curvature of approx. 30 ⁰, and fully formed apices
- 3 pre-op radiographs exposed; All teeth treated by two endodontists
- 10/02 K-file explored patencyà GG orifice enlargementà WL determined by 0.5 mm shorter than EAL and confirmed radiographicallyà RC-prep on a 15/02 K-file to establish a glide pathà 40/04 down to 20/04 ProFiles in crown-down techniqueà all canals opened to at least 30/04 at WL
- Each set of ProFiles used for shaping 5 molars before being discarded
- When instrument fractured, attempt to bypass with 8/02 and 10/02 K-file with NaOCl and EDTA (ultrasonic activation at lowest setting)
- If the fracture could not be bypassed, size and number of time the file was used were recorded.
- Lateral condensation obturation. 3 post-op radiographs exposed
- Chi-square test statistical analysis
- 19 (out of 449= 4.2 %) instruments showed plastic deformation and were discarded and replaced
- 21 (4.6 %) instruments fractured in the canal during treatment
- 14 fractured in apical third (6 were 20/04, 3 were 25/04, 2 were 35/04); 3/14 were bypassed
- 7 fractured in the middle third (2 were 40/04, 3 were 35/04, 2 were 30/04); 5/7 were bypassed
- Most common fractured was the 20/04 especially after the second use (p< 0.05)
Increasing the number of times ProFile instruments were used increased their fracture rate. One third of fractured instruments were bypassed, and bypassing was more likely in the middle third.