When using gross radiographic criteria, the Activ GP was more effectively removed from root canals than AH Plus with hand instrumentation. Hybrid Root SEAL, EndoSequence BC Sealer and AH Plus were removed to a similar extent. ProTaper Universal retreatment instruments were as safe and effective as hand instruments in reaching the working length.

Evaluation of deformation and fracture rates for nickel-titanium rotary instruments according to the frequency of clinical use Purpose To evaluate the deformation and fracture rates for ProTaper Universal (PTU) nickeltitanium rotary instruments according to the frequency of clinical use. Materials and MethodsA total of 619 PTU instruments (S1, S2, F1, F2, and F3) that have been used in the clinic by a single endodontist were collected over a period of 4 years. These instruments were grouped on the basis of one to three (Group A), four to six (Group B) and seven to nine (Group C) clinical uses (one canal = one use). All instruments were evaluated by a blinded investigator under a stereomicroscope at 15×-45× magnification for the presence of deformation and fracture. ResultsThe overall rates of deformation and fracture were 10% and 1.2%, respectively. The deformation and fracture rates for the S2, F1, and F2 instruments showed no significant differences among groups. However, fracture rate for S1 instruments in Group A was significantly higher than for those in Group B (p=0.025) and Group C (p=0.004). In Group C, the S1 instruments showed a significantly higher deformation rate compared with the S2 (p=0.04), F1 (p=0.008) and F2 (p=0.049) instruments; there were no other significant differences within groups. ConclusionUnder the conditions of the current study, frequency of use seemed to influence the deformation rates of PTU rotary instruments. Except S1, these instruments could be used without any fracture or deformation in up to 9 clinical cases by an experienced endodontist.

Evaluation of deformation and fracture rates for nickel-titanium rotary instruments according to the frequency of clinical use Purpose To evaluate the deformation and fracture rates for ProTaper Universal (PTU) nickeltitanium rotary instruments according to the frequency of clinical use. Materials and MethodsA total of 619 PTU instruments (S1, S2, F1, F2, and F3) that have been used in the clinic by a single endodontist were collected over a period of 4 years. These instruments were grouped on the basis of one to three (Group A), four to six (Group B) and seven to nine (Group C) clinical uses (one canal = one use). All instruments were evaluated by a blinded investigator under a stereomicroscope at 15×-45× magnification for the presence of deformation and fracture. ResultsThe overall rates of deformation and fracture were 10% and 1.2%, respectively. The deformation and fracture rates for the S2, F1, and F2 instruments showed no significant differences among groups. However, fracture rate for S1 instruments in Group A was significantly higher than for those in Group B (p=0.025) and Group C (p=0.004). In Group C, the S1 instruments showed a significantly higher deformation rate compared with the S2 (p=0.04), F1 (p=0.008) and F2 (p=0.049) instruments; there were no other significant differences within groups. ConclusionUnder the conditions of the current study, frequency of use seemed to influence the deformation rates of PTU rotary instruments. Except S1, these instruments could be used without any fracture or deformation in up to 9 clinical cases by an experienced endodontist.