Lateral Condensation in Straight Canal Prepared by Engine-driven Rotary Instruments and Its Evaluation Method

Abstract

Root canal obturation was performed by the lateral condensation method on straight root canal models with taper of 6/100 under the pre-condition that preparation had been conducted by using an engine-driven rotary instrument. The spreaders used included: a type of stainless steel spreader (DentalEZ: Star Dental D11T (S-D11T)), and 6 types of Ni-Ti spreader (Roeko: NiTi #15 (R-15), NiTi #25 (R-25), NiTi #35 (R-35), NiTi D11T (R-D11T)); and Brasseler: Naviflex NT D11T (B-D11T) and Naviflex NT 4SP (B-4SP). Hermetic seal was evaluated according to 3 evaluation methods, i.e. the percentage of canal wall area coated with sealers of <5μm in thickness (GP pressure welding ratio), the percentage of gutta-percha-obturated canal area determined on micro focus X-ray CT images (GP/CT condensing ratio), and the mean percentage of gutta-percha-obturated canal area in all canal cross-sections and each position from the apex (GP total condensing ratio and GP local condensing ratio, respectively). The following conclusions were obtained: 1.GP pressure welding ratio by the remaining sealer was the highest in B-D11T, being 92.1%, followed by R-D11T, S-D11T, R-15, R-25 and R-35 in this order. B-4SP showed the lowest value of 57.9%. 2. In GP/CT condensing ratio by the micro focus X-ray CT device, S-D11T showed the highest value of 96.6%, followed by B-D11T, R-D11T, R-25, R-35 and R-15 in this order. B-4SP showed the lowest value of 88.9%. 3. In GP total condensing ratio on the cutting surface of the model, S-D11T showed the highest value of 97.9%, followed by B-D11T, R-D11T, R-25, B-4SP and R-15 in this order. R-35 showed the lowest value of 90.4%. 4. In GP local condensing ratio at the cutting position on the cutting surface of the models, S-D11T exhibited a value as high as 96.9% or more at each cutting position. On the other hand, B-D11T showed a lower condition in pressure welding compared with S-D11T. A tendency was noticed that the condensing ratio decreased at the root canal tip. Also, the condensing ratio tended to decrease at the middle of the root canal in R-D11T, R-25, R-15, B-4SR and R-35 in this order. 5. Statistical analysis was performed on the difference of the evaluation methods on GP/CT condensing ratio and GP total condensing ratio on the cutting surface by using the micro focus X-ray CT device. As a result, no statistically significant difference was noted between the two. These results reveal that the evaluation method by using the micro focus X-ray CT device has high reliability and usefulness.