Fracture strength of mesiobuccal roots following canal preparation with hand and rotary instrumentation: an in vitro study

The aim of this in vitro study was to compare the effect of hand and rotary instruments on fracture strength of tooth roots. Thirty two teeth were randomly divided into two experimental groups of 15 each and one negative control group with two samples. In group 1, step-back technique with conventional stainless steel K-files was used, and in group 2, instrumentation was performed using rotary Ni-Ti Hero642. Samples in control group did not receive cleaning or shaping after access cavity preparation. After obturating each canal, tip of the spreader was locked within canal. The required force for root fracture was measured using Instron testing machine. Recorded data was statistically analyzed using t-test. The mean and standard deviation force required for vertical root fracture were 50.33 +/- 19.1 and 63.1 +/- 25.46 N for hand and rotary groups respectively. However, no significant difference was found between experimental groups. The results indicate that the manual technique did not lower fracture strength of obturated roots in comparison with the rotary preparation technique

Comparing coronal discoloration between AH26 and ZOE sealers

Intrinsic tooth discolorations after endodontic treatment are principally attributed to the composition of necrotic pulp tissue, hemorrhage within the pulp cavity, endodontic medicaments and/or filling materials. Residual sealer left in pulp chamber after obturation can cause discoloration. The objective of this in vitro study was to evaluate coronal discoloration created by AH26 and ZOE sealers after four months. Fifty intact human extracted maxillary central incisors were employed. Access cavities were prepared in all samples and root canals were instrumented; coronal orifices were then sealed using self-cure glass ionomer. The teeth were divided into two experimental groups [n=20] according to utilized sealer in pulp chambers including AH26 and Dorifill [ZOE]. The remaining 10 teeth served as negative and positive controls [n=5]. The access cavities were sealed with self-cure glass ionomer. Teeth were kept in incubator for four month. Preliminary digital images of the teeth were taken and then compared with those related to 4-month follow-up. The images were assessed using Photoshop software. Data was analyzed using paired t-test and independent samples t-test. The teeth which were filled with AH26 sealer showed significantly greater discoloration than those filled with ZOE sealer [Dorifill] [P<0.05]. AH26 sealer causes greater discoloration of the crown compared to ZOE sealer. Despite the other disadvantage of AH26 sealer, it seems that Dorifill is more esthetically considerate