Efficacy of Solution Form of Ethylenediaminetetraacetic Acid on Removing Smear Layer of Root Canal at Different Exposure Time In Vitro

Summary： This study was aimed to evaluate the effectiveness of solution form of 17% ethylenediaminetetraacetic acid （EDTA） on removing smear layer of root canals at different exposure time periods and to provide scientific basis for EDTA as a choice of root canal irrigation in clinical practice. Twenty-five single-rooted teeth were randomly divided into 5 groups： control group （group A） was given 2.5% NaOC1, and 4 experimental groups were given 2.5% NaOC1 and 17% EDTA, including groups B, C, D and E with exposure time of 1, 3, 5 and 7 min, respectively. After preparation of the root canals, the teeth were split along their longitudinal axis, and the root sections were examined under scanning elec- tron microscope for evaluation of smear layer removal and erosion on the surface of the root canal walls. The specimens in group B showed presence of smear layer on the walls of the root canal with no statistical difference from that in group A （P〉0.05）. In groups C and D, partial removal of smear layer was obtained, and there was no significant difference between the two groups （P〉0.05）, but there was significant difference in removal of smear layer between group C and group B （P〈0.05）. Root canal walls in group E specimens showed almost complete removal of smear layer, and the removal of smear layer was significantly different from that in group D （P〈0.01）. There was no significant change in the structure of the surface of root canal for each sample. It was concluded that combined irrigation with 17% EDTA and 2.5% NaOC1 could remove the smear layer with no significant alteration in dentinal structure when the chelating agent was applied for 7 min. At 3 and 5 min of application, partial removal of smear layer was observed and at 1 min negligible removal of smear layer was achieved.

The cleaning efficiency of the root canal after different instrumentation technique and irrigation protocol:A SEM analysis

Aim: The objective of this study was to evaluate the effectiveness of manual and ultrasonic instrumentation with varying irrigation protocols on removal of the smear layer from root canal walls. Methods: Forty extracted single rooted human teeth stored in 0.5% saline were used. Periodontal soft tissues were removed followed by crown separation at the CEJ. All the teeth were randomly divided into two groups. Manually Instrumented Group 1 was irrigated with 5.25% NaOCl and 17% EDTA alternately, same as Ultrasonically Instrumented Group 2. The controls for both groups were irrigated with saline solution. Results: Ultrasonic instrumentation and the combined use of two different solutions (5.25% NaOCl and 17% EDTA) yielded better results on smear removal. Conclusions: Irrigation with 17% EDTA followed by 5.25% NaOCl was successful in complete removal of smear layer on cervical and middle thirds of the root canals. Ultrasonic instrumentation was slightly more successful on the apical one third of the root canals.

Effect of Different Pretreatments to Post-space on Bonding Strength of Fiber Posts Luted with a Self-adhesive Resin Cement

The effects of different post-space pretreatments on the retentive force of fiber posts cemented with a self-adhesive resin cement were investigated. Twenty-eight single-canal premolars were obturated by Resilon using warm vertical compaction and treated with distilled water, 2.5% NaOCl, 17% EDTA and 2.5% NaOCI; or 17% EDTA, 2.5% NaOCI, and ultrasonic agitation （U/E/N treatment）. Subsequently, radicular dentin surfaces were observed under scanning electron microscopy （SEM）. RelyX Fiber Posts were cemented in the treated canals by using RelyX U100, and thin-slice push-out test and SEM observation of coronal and apical regions of the specimens were performed. Data were analyzed using two-way ANOVA and Tukey＇s HSD post- hoc tests, and the percentage of failure type was calculated. Ultrasonic/EDTA/NaOC1 irrigation showed the maximum effectiveness in removing the smear layer and debris on the dentin surface. The apical bond strength of the experimental groups was significantly higher than that of the control group （P〈 0.05）. Adhesive failure between cement and dentin was the most common mode of failure. No obvious RDIZ or resin tag was detected. Chemical irrigants facilitated the bonding of these fiber posts, and ultrasonic activation improved retention. Future studies should evaluate the effectiveness of irrigation on fiber post push-out strength in fatigue cycling condition.

Sealing ability of AH26 and soft core gutta-percha using different instrumentations techniques and irrigations protocol: A SEM evaluation

Aim: The aim of this ex vivo study, with SEM, was to determine the effects of the smear layer on the root canal systems after different instrumentation technique and irrigation protocol, obturated with carrier based gutta-percha (Soft Core) and AH26 sealer. Materials & Methods: Forty freshly extracted human teeth were used for this study. The teeth were divided into two major groups according to instrumentation technique (Manual and ProFile) and then each major group into four subgroups according to irrigation protocol (Saline solution, 17% EDTA, 5.25% NaOCl). All of the samples were obturated with AH26 and Soft Core Heating Gutta-percha. The evaluation of the objectives was performed using a Scanning Electron Microscope. Result: ProFile instrumentation followed with irrigation of 17% EDTA and 5.25% NaOCl, selaed with AH26 Soft Core Heating Guttapercha provided maximal contact at the S/D interface. The S/D interface had a serrated appearance due to effective penetration of the sealer into the patent dentin tubules. Conclusions: The adhezion of the respective sealer is more successful in cases when smear layer was removed completely.

Influence of casein phosphopeptide-amorphous calcium phosphate application,smear layer removal, and storage time on resin-dentin bonding

The aim of this study is to evaluate the influence of Tooth Mousse （TM） application, smear layer removal, and storage time on resin-dentin microtensile bond strength （pTBS）. Dentin specimens were divided into two groups： （1） smear layer covered; （2） smear layer removed using 15% EDTA for 90 s. In each group, half the specimens were treated once with TM for 60 min. After bonding procedures using a two-step self-etching adhesive （Clearfil SE Bond （CSE）; Kuraray Medical, Tokyo, Japan）, an all-in-one adhesive （G-Bond （GB）; GC Corp, Tokyo, Japan）, and a total-etch adhesive （Adper Single Bond 2 （SB）; 3M ESPE, St. Paul, MN, USA）, the specimens were stored for 3 d or 6 months in deionized water at 37 ℃, and pTBS was tested and analyzed. With the exception of SB （no TM application） and GB, the pTBS was significantly increased for CSE and SB using EDTA pre-conditioning and 3 d of storage （P≤0.001）. Bond strength of GB decreased significantly when using EDTA （3 d storage, P〈0.05）. TM application only increased the pTBS of GB （no EDTA） and SB （with EDTA） after 3 d （P≤0.02）. Comparing the adhesives after 3 d of storage, CSE exhibited the greatest pTBS values followed by GB and SB （P≤0.02）. The factors of adhesive, EDTA, and TM did not show any significant impact on pTBS when specimens were stored for 6 months （P〉0.05）. The additional application of TM and EDTA for cavity preparation seems only to have a short-term effect, and no influence on pTBS of dentin bonds after a period of 6 months.