Purpose: to evaluate the separation incidence of reused ProTaper Universal rotary instruments and identify the relevant factors.
N= 6,154 canals /2,654 teeth
•First, glide path created with #10, then SX , WL:#15, THEN all files starting from S1 to F3 were used.
•Instruments used maximum # were collected and analyzed, fractured instruments examined under stereomicroscope.
•Canals, tooth , curvature were determined according to Schneider et al.
Most highlighted Results:
- Incidence of instrument separation (table1), separation in relation to tooth type (table 2).
- Instrument separation in Mand teeth : MB(47.5%), ML(35%) D (17.5%).
- Instrument separation in MAX teeth : MB (61.5%), DB (30.8%), P (7.7%).
- Curvature and fracture : sever (54%), moderate (28.6%), mild (17%).
- 91% of separation happened in the apical 3rd. The rest in the middle. Mean length of 3 mm.