Computed tomographic evaluation of canal shape instrumented by different kinematics rotary nickel-titanium systems.

INTRODUCTION: This study evaluated the effects of 2 different kinematics rotary nickel-titanium (NiTi) systems, Twisted File (TF), a continuous rotation full-sequence system, and WaveOne (WO), a reciprocating single-file system, on transportation, curvature, and volumetric changes of curved root canals by using cone-beam computed tomography. METHODS: Forty mesiobuccal canals of mandibular molars with angle of curvature ranging from 25°-35° were divided according to the NiTi rotary system used in canal preparation into 2 groups of 20 samples each, TF group and WO group. Canals were scanned by using an i-CAT cone-beam computed tomography scanner before and after instrumentation to evaluate canal transportation at coronal, middle, and apical thirds, canal curvature, and volumetric changes. The significance level was set at P ≤ .05. RESULTS: TF system recorded significantly lower mean of canal transportation than WO group at all canal thirds (apical P = .034, middle P = .003, and coronal P = .012). In both groups the apical third recorded the significantly least amount of transportation (P < .05). There was no significant difference between the 2 groups in canal curvature and volumetric changes after instrumentation (P > .05). CONCLUSIONS: Both TF and WO NiTi systems can be safely used to the full working length, resulting in satisfactory preservation of the original canal shape.

Resistance to fracture of roots obturated with novel canal-filling systems.

INTRODUCTION: This study was conducted to evaluate and compare the fracture resistance of roots obturated with various contemporary canal-filling systems. METHODS: Fifty single-rooted extracted mandibular premolars were decoronated to obtain 13-mm root segments. Ten roots were left unprepared and unfilled (negative control). Forty canals were instrumented using 0.06 taper EndoSequence files (Brassler, Savannah, GA). Roots were divided according to the obturating system into 4 groups (n = 10): group 1: iRoot SP sealer (Innovative Bioceramix, Vancouver, Canada) + ActiV GP cone (Brasseler USA, Savanah, GA), group 2: iRoot SP sealer + gutta-percha (GP), group 3: ActiV GP sealer + ActiV GP cone, and group 4: ActiV GP sealer + GP. All groups were obturated using single-cone technique. The roots within each group were embedded in acrylic molds and subjected to the fracture resistance test in which a compressive loading (0.5 mm/min) was applied until fracture. Data were statistically analyzed (analysis of variance and Tukey post hoc test). RESULTS: The significantly highest fracture resistance was recorded for both the negative control group (381.4 ± 53.2 N) and group 1 (iRoot SP sealer/ActiV GP cone [372 ± 62.9 N]) with no significant difference between them, whereas the significantly lowest value was reported in group 4 (ActiV GP sealer/GP cone [288.3 ± 30.5 N]). CONCLUSION: Bioceramic-based sealer (ie, iRoot SP) is a promising sealer in terms of increasing in vitro resistance to the fracture of endodontically treated roots particularly when accompanied with ActiV GP cones.

Bonding strategies to pulp chamber dentin treated with different endodontic irrigants: microshear bond strength testing and SEM analysis.

PURPOSE: To evaluate the effect of 6 irrigant regimens on the microshear bond strength of different adhesives to pulp chamber dentin and to determine their interfacial morphology by SEM. MATERIALS AND METHODS: Forty-three human molars were split into halves and ground to provide flat pulp chamber dentin. Eighty-five halves were used. The specimens were assigned to 6 groups according to the irrigant regimen used. Group I (n=10) was irrigated with distilled water (control). The remaining 5 groups (n=15 each) were irrigated with 5.25% NaOCl followed by either 5.25% NaOCl, 17% EDTA, benzalkonium chloride (Tubilcid Plus) or MTAD (Biopure), either rinsed or not. Irrigated specimens were bonded using Clearfil S3 Bond or Adper Single Bond 2, which was employed with or without etching. Resin composite cylinders were bonded using tygon tubes for microshear bond strength testing. Data were analyzed using two-way ANOVA followed by Tukey's post-hoc test. Representative specimens of each group were prepared from 17 further molars for interfacial SEM examination. RESULTS: The different irrigant regimens used did not significantly alter the microshear bond strength values using either of the bonding systems, except NaOCl, which significantly reduced the microshear bond strength values with Adper Single Bond 2. Bonding irrigated specimens directly using the Adper Single Bond 2 without prior etching provided significantly reduced values. CONCLUSION: The irrigant regimens examined could be used safely prior to bonding except for the NaOCl, which should be negated if it is to be followed by Adper Single Bond 2, and the etching step cannot be omitted if an etch-and-rinse adhesive system is the adhesive of choice.

The effect of different irrigating solutions on bond strength of two root canal-filling systems.

The bond strength of ActiV GP root canal filling system and gutta-percha/AH plus sealer when used after final rinse with different irrigation protocols was evaluated in this study. Forty roots were randomly divided into four groups (n = 10) according to the final irrigation regimen: group 1, 5 mL 17% EDTA; group 2, 5 mL 17% EDTA followed by 5 mL 2% chlorhexidine gluconate (CHX); group 3, 5 mL MTAD; and group 4, 5 mL MTAD followed by 5 mL 2% CHX. Each group was further subdivided into two subgroups (n = 5): in subgroup a, the root canals were filled using warm gutta-percha and AH plus sealer, and in subgroup b, the root canals were filled using the ActiV GP obturation system. Two-millimeter thick horizontal sections from the coronal and midthirds of each root were sliced for the push-out bond strength measurement. EDTA/CHX/ActiV GP (2.46 +/- 1.02 MPa) yielded significantly the highest mean bond strength value. The significantly lowest bond strength was recorded for EDTA/ActiV GP (1.12 +/- 0.72 MPa). It was concluded that the bond strength of ActiV GP was improved by using 2% CHX in the final irrigation after 17% EDTA, whereas CHX did not enhance the effect of MTAD on the bond strength of the material. The bond strength of gutta-percha/AH plus was adversely affected by MTAD and MTAD/CHX.