Effect of chelating solutions on the microhardness of root canal lumen dentin

Introduction

The greatest reduction in microhardness of the most superficial layer of dentin of the root canal lumen is desired. The use of chelating agents during biomechanical preparation of root canals removes smear layer, increasing the access of the irrigant into the dentin tubules to allow adequate disinfection, and also reduces dentin microhardness, facilitating the action of endodontic instruments. This study evaluated the effect of different chelating solutions on the microhardness of the most superficial dentin layer from the root canal lumen.

Methods

Thirty-five recently extracted single-rooted maxillary central incisors were instrumented, and the roots were longitudinally sectioned in a mesiodistal direction to expose the entire canal extension. The specimens were distributed in seven groups according to the final irrigation: 15% EDTA, 10% citric acid, 5% malic acid, 5% acetic acid, apple vinegar, 10% sodium citrate, and control (no irrigation). A standardized volume of 50 μL of each chelating solution was used for 5 minutes. Dentin microhardness was measured with a Knoop indenter under a 10-g load and a 15-second dwell time. Data were analyzed statistically by one-way analysis of variance and Tukey-Kramer multiple-comparison test at 5% significance level.

Results

EDTA and citric acid had the greatest overall effect, causing a sharp decrease in dentin microhardness without a significant difference (p > .05) from each other. However, both chelators differed significantly from the other solutions (p < .001). Sodium citrate and deionized water were similar to each other (p > .05) and did not affect dentin microhardness. Apple vinegar, acetic acid, and malic acid were similar to each other (p > .05) and presented intermediate results.

Conclusion

Except for sodium citrate, all tested chelating solutions reduced microhardness of the most superficial root canal dentin layer. EDTA and citric acid were the most efficient.     

Evaluation of the effect of endodontic irrigation solutions on the microhardness and the roughness of root canal dentin

The purpose of this study was to evaluate the effect of 0.2% chlorhexidine gluconate on the microhardness and roughness of root canal dentin compared with widely used irrigation solutions. Ninety, mandibular, anterior teeth extracted for periodontal reasons were used. The crowns of the teeth were removed at the CEJ. The roots were separated longitudinally into two segments, embedded in acrylic resin, and polished. A total of 180 specimens were divided into 6 groups of 30 teeth at random according to the irrigation solution used: group 1: 5.25% NaOCl for 15 min; group 2: 2.5% NaOCl for 15 min; group 3: 3% H2O2 for 15 min; group 4: 17% EDTA for 15 min; group 5: 0.2% chlorhexidine gluconate for 15 min; and group 6: distilled water (control). Each group was then divided into 2 subgroups of 15 specimens: groups 1a, 2a, 3a, 4a, 5a, and 6a were submitted to Vickers microhardness indentation tests; groups 1b, 2b, 3b, 4b, 5b, and 6b were used for determination of the roughness of root dentin. The data were recorded as Vickers numbers and Ra, microm for roughness test. The results were analyzed statistically by using one-way ANOVA and Tukey tests. The results indicated that all the irrigation solutions except chlorhexidine significantly decreased microhardness of root canal dentin (p < 0.05); 3% H2O2 and 0.2% chlorhexidine gluconate had no effect on roughness of the root canal dentin (p > 0.05). Although there are many other factors for irrigation solution preference, according to the results of this study, 0.2% chlorhexidine gluconate seems to be an appropriate endodontic irrigation solutions because of its harmless effect on the microhardness and roughness of root canal dentin.     

Effect of a new conditioning agent on dentin

The effect of varying the duration of application of the conditioner for light-cured Zionomer was studied. The conditioner is a solution of oxalic acid and aluminum nitrate in a weak mineral acid and has a pH of 2.06. Recently extracted non-carious human premolars were sectioned horizontally 300 microns below the amelodentinal junction and then lightly ground with a high-speed diamond bur under copious water-spray to produce a smear layer. Each was then sectioned vertically into three and all the specimens were either treated with the Zionomer Conditioner for 5, 10, 20 or 30 seconds, or with distilled water as a control. All the specimens were examined in a scanning electron microscope at x1000 and photomicrographs taken which were then assessed, independently, by the authors. The results revealed that application of Zionomer Conditioner for as little as 5 seconds was sufficient to remove most of the smear layer. There was complete removal of the surface smear layer in specimens treated for 10 seconds or more. Either a 20 second or a 30 second application removed the smear layer completely and could also widen the exposed tubule orifices.     

The effect of Morinda Citrifolia juice as an endodontic irrigant on smear layer and microhardness of root canal dentin

PurposeThe purpose of this study was to evaluate the effect of Morinda Citrifolia Juice (MCJ) on smear layer removal and microhardness value of root canal dentin in compared with various endodontic irrigants.Material and methodsEighty-four single-rooted human teeth were prepared to apical size of #35. Since decoronation, samples were divided into seven groups of 12 in each (n = 12). Specimens were finally irrigated by either 1: 2.5% NaOCl, 2: 6% MCJ, followed by a final flush of 17% ethylene diaminetetraacetic acid (EDTA), 3: 6% MCJ, 4: 2.5% NaOCl then17% EDTA, 5: MTAD, 6: 2% chlorhexidine (CHX), and 7: saline. After irrigation, all samples were subjected to Vickers microhardness test at 100 and 500-μm depths and then were examined under scanning electron microscopy (SEM) and ImageJ program was used to calculate open dentinal tubules. One way ANOVA and post hoc Tukey tests were used to reveal any significant differences among and between groups respectively.ResultsThe microhardness values at 100 μm and 500 μm for MTAD were significantly lower than for NaOCl + EDTA and MCJ + EDTA groups (p < 0.05). MCJ + EDTA, NaOCl + EDTA, and MTAD protocol significantly removed smear layer in compared with control group (p < 0.05), with no significant differences among these three groups.ConclusionsIt was concluded that 6% MCJ followed by a final flush of 17% EDTA can be regarded as an effective solution on smear layer removal without any adverse influence on microhardness property of root canal dentin.     

Effects of chelating agents and sodium hypochlorite on mineral content of root dentin

Effects of combined and single use of EDTA, RC-Prep, and NaOCl on mineral content of root dentin were evaluated in vitro using energy dispersion spectrometric microanalysis. Thirty-six standardized midroot dentin specimens obtained from human anterior teeth were used. Specimens were polished and divided into six experimental groups. The first two groups were treated with EDTA or RC-Prep followed by NaOCl irrigation. Groups 3 to 5 were treated with EDTA, RC-Prep, and NaOCl, respectively. The last group was irrigated with saline solution as a control. Levels of calcium, phosphorus, and magnesium were measured in the root dentin after treatments. The results showed that (i) EDTA combined with NaOCl irrigation as final flush and NaOCl alone changed the calcium/phosphorus ratio of root dentin significantly (p < 0.05); and (ii) there was a significant increase in the magnesium level after the use of chelating agent combined with NaOCl (p < 0.05). It was concluded that using NaOCl irrigation as final flush altered the effectiveness of chelating agents on root dentin.     

螯合剂作为根管冲洗剂的研究进展

目前,国内临床上多使用体积分数为3％的过氧化氢和生理盐水交替冲洗根管,但是这2种溶液存在许多缺陷。次氯酸钠具有较强的杀菌性和组织溶解性,所以在国外被普遍应用于根管冲洗中。目前,国内也正逐步将次氯酸钠应用于临床,但是却很少使用螯合剂作为根管常规的冲洗液。螯合剂的优势日益受到关注,螯合剂具有去除根管预备中形成的玷污层的优势,但不能有效溶解残留的牙髓,次氯酸钠具有有效溶解有机残髓的作用,两者联合应用能达到相互补偿、相互增效的作用,是目前用于玷污层去除的有效组合。本文对螯合剂的研究进展作一综述,以期推广其在国内临床上的应用。     

The effect of a re-wetting agent on dentin bonding.

OBJECTIVES: Recently, a new generation of simplified one-bottle dentin bonding systems, sensitive to variations in the degree of substrate moisture, was introduced. This in vitro project compared the dentin bond strengths and interfacial ultra-morphology formed by three one-bottle bonding systems [OptiBond SOLO (ethanol-based), Prime&Bond 2.1 (acetone-based), and Single Bond (ethanol- and water-based)]. The null hypothesis tested was that re-wetting a dried dentin surface with a HEMA aqueous solution would not result in bond strengths, and resin impregnation into demineralized dentin, comparable to those obtained for moist dentin. METHODS: Dentin specimens were assigned to the following three etched surface conditions: moist dentin-control group; dentin dried for 5 s; and dentin dried for 5 s and re-moistened with a commercial 35% HEMA aqueous solution. Mean shear bond strengths were calculated and analyzed with one- and two-way ANOVA. Dentin discs treated with the same combination of surface condition/adhesive were processed and observed under both transmission and scanning electron microscopes. RESULTS: For moist dentin, the morphology of the resin-dentin interfaces showed penetration of the dentin adhesives to the depth of the transition between demineralized and unaffected dentin. Drying dentin for 5 s resulted in a significant decrease in mean bond strengths and an incompletely infiltrated collagen structure with areas of unveiled collagen fibers, regardless of the solvent. Re-wetting dentin with the aqueous HEMA solution re-established the level of bond strengths obtained to moist dentin and resulted in a raise of the fiber network with simultaneous increase in interfibrillar space dimensions. SIGNIFICANCE: The results suggest that the use of an aqueous HEMA solution might compensate for the dryness induced on dentin surfaces by using air blasts from an air syringe, after rinsing off the etchant. As the behavior of the material that contained water was also affected by surface dryness, the percentage of water included in the composition of current ethanol- and water-based adhesives, such as Single Bond, may not be enough to compensate for the collapse of the collagen filigree upon drying.     

Effect of sodium hypochlorite on dentin microhardness

This study was designed to evaluate the effect on root dentin microhardness of 2.5% and 6% sodium hypochlorite solutions for various irrigation periods. Forty-two bovine roots were divided into seven groups. The control group was irrigated with saline. The experimental samples were continuously irrigated with 2.5% or 6% NaOCl for 5, 10, or 20 min. Microhardness was measured at depths of 500 mum, 1000 mum, and 1500 mum from the lumen. A decrease in microhardness was found at 500 mum between the control and samples irrigated with 6% NaOCl and 2.5% NaOCl (p = 0.352, p = 0.084 respectively) at all irrigation periods. There also was a significant difference in groups irrigated for 10 or 20 min (p = 0.001, p < 0.001 respectively). At all distances, the decrease in microhardness was more marked after irrigation with 6% NaOCl than 2.5% NaOCl.     

The effect of instrumentation with two different file types,each with 2.5% NaOCl irrigation on the microhardness of root dentin

The aim of this study was to measure root-dentin microhardness after instrumentation with two types of files and using irrigation with 2.5% sodium hypochlorite. Thirty roots were instrumented with irrigation: 10 roots had the pulp extirpated only; 10 roots were instrumented with stainless steel files, and 10 roots were instrumented with rotary nickel-titanium (NiTi) files. Additionally, five roots were extirpated only without irrigation and served as a control. The roots were sliced and root-dentin microhardness was determined at depths of 500 microm and 1000 microm from the pulp-dentin interface. Significant differences were found between the microhardness at 500 microm and 1000 microm (p < 0.001) in all groups. Instrumentation with NiTi rotary files affected dentin microhardness significantly to a lesser extent.     

Concentration-dependent effect of bleaching agents on microhardness and roughness of enamel and dentin

PURPOSE: To evaluate the microhardness and surface roughness of enamel and root dentin bleached with 10%, 15% and 22% carbamide peroxide agents. METHODS: 52 slabs of enamel and root dentin (6 x 3 x 2 mm) were cut from bovine incisors, ground flat and polished. According to a randomized complete block design, enamel and root dentin slabs (n = 13) were independently allocated to be bleached with one of the following carbamide peroxide-containing agents (CP): 10% (Rembrandt Bleaching Gel Plus), 15% (Rembrandt Xtra Comfort), or 22% (Rembrandt Xtra Comfort Ultra Strength). The control groups were mock-treated with artificial saliva. The bleaching procedures consisted of daily application of the agents on dental substrate surfaces for 2 hours, followed by immersion in artificial saliva for 22 hours over 21 days. Knoop microhardness and surface roughness were measured initially, on sound dental tissues, and at the postbleaching phase. RESULTS: In enamel, microhardness attained after bleaching with 10% CP and 15% CP were similar and significantly lower than that observed for the control group. Specimens bleached with CP 22% did not differ from any of the other groups tested. In root dentin, microhardness changes were indistinguishable. ANOVA showed no significant difference among treatments with respect to surface roughness.     

Adhesive strength of self-adhesive resins to lithium disilicate ceramic and dentin: effect of dentin chelating agents

The aim of this study was to test the effect of different chelating agents on microtensile bond strength (MTBS) of self-adhesive resin cements to dentin. The occlusal surfaces of extracted human mandibular molars (N = 80) were cut horizontally to expose sound dentin. The teeth were randomly divided into four groups (n = 20 per group) and dentin surfaces were conditioned according to one of the following methods: group C: no treatment (control group); group CH: 0.2 % chitosan; group E: 17 % ethylene diamine tetra acetic acid (EDTA) and group P: 25 % polyacrylic acid (PAA). Lithium disilicate glass ceramic (e.max CAD) blocks were cemented to conditioned dentin surfaces with self-adhesive cements (RelyX Unicem or Clearfil SA) and photo-polymerized. Specimens were stored in distilled water at 37 °C for 24 h and thermocycled for 6,000 times. The beams were obtained from bonded ceramic–cement–tooth assemblies and were subjected to the MTBS test (1 mm/min). Failure types were analyzed and selected beams were examined under scanning electron microscope. Data (MPa) were analyzed using two-way ANOVA and Tukey’s test (P < 0.05). While cement type significantly affected the MTBS results (P < 0.05), no significant difference was observed between the dentin chelating agents (P = 0.785). Interaction terms were not significant (P = 0.114). Control group with no dentin conditioning presented significantly lower results with both cements (RelyX Unicem: 8.1 ± 1.9^a, Clearfil SA: 8 ± 1.6^a) than those of conditioned groups (19.3 ± 4.2^b–24.5 ± 5.2^b) (P < 0.05). Failure types were predominantly adhesive in all groups. Chitosan (2 %), EDTA (17 %) or PAA (25 %) could all be used as dentin chelating agents in conjunction with self-adhesive resin cements tested.     

Effect of EDTA and citric acid solutions on the microhardness and the roughness of human root canal dentin

The purpose of this study was to evaluate the effect of citric acid and EDTA solutions on the microhardness and the roughness of human root canal dentin. Forty-five human teeth sectioned longitudinally were used. Specimens were randomly divided into three groups of 30 teeth each and were treated as follows: (a) one molar (19%) citric acid (C6H8O7) for 150 s followed by 5.25% NaOCl; (b) 17% EDTA for 150 s and rinsed with 5.25% NaOCl; (c) rinsed with distilled water and served as control. Three groups were then divided into two subgroups of 15 specimens each. The specimens, in first subgroup were subjected to Vicker's testing whereas the second subgroup underwent surface roughness testing. The results were analyzed using one-way ANOVA and Tukey tests. Significant differences were observed in microhardness among the test groups, citric acid group being the least hard (p 0.05). Also, citric acid significantly increased surface roughness.     

The effect of fluorine and other biogeochemical factors on enamel and dentin microhardness

Dental enamel and dentin microhardness were studied in subjects aged 35-44 living in various climatic and geographic zones of Azerbaijan. A total of 172 intact teeth were examined. Dental hard tissue microhardness was found to be related to caries intensity, fluorine content in potable water, and to other biogeochemical factors. Enamel and dentin microhardness were found much higher in the areas with high fluorine levels of potable water than in those with fluorine-deficient water.