Adhesion of a glass-ionomer root canal sealer to the root canal wall

Glass-ionomer root canal sealer is commonly used because of its chemical bonding and favorable physical characteristics when bonding to dentin. This study was designed to determine the tensile bond strength of a glass-ionomer sealer (Ketac Endo, Espe, Seefeld, Germany) on root canal walls after pretreatment with different conditioners. Flat inner surfaces of root canal specimens were prepared. The specimens were divided into five groups of 10 teeth, and the groups were conditioned with one of the following smear layer removal solutions: 15% EDTA/NaOCl, 10% polyacrylic acid, 35% phosphoric acid, 6% citric acid, and 5.25% NaOCl as a control. Then the exposed root canal areas were coated with Ketac-Endo. Tensile bonding was measured using a universal testing machine until ultimate failure was obtained. The groups that were treated with phosphoric acid and citric acid showed significantly higher bond strengths than the groups that were treated with 15% EDTA and polyacrylic acid (p < 0.05). Bonding to dentin without smear layer removal (NaOCl group) was too low to be measured in the testing apparatus. Scanning electron microscopy confirmed that phosphoric and citric acids were more effective in removing smear layer than EDTA or polyacrylic acid. The result supported the view that pretreatment with phosphoric acid or citric acid should be used in association with glass-ionomer root canal sealer to achieve the most effective removal of the smear layer and to provide better adhesion.     

Effects of chemical pretreatments on dentin bonding

The aim of this study was to evaluate several chemical pretreatments on the shear bond strength of three dentin bonding agents (DBAs) and to try to correlate dentin morphology with bond strength using scanning electron microscopy (SEM). The DBAs tested were: Gluma Primer in association with Scotchbond DC, Scotchbond DC alone and Clearfil New Bond. Bond strengths of Scotchbond DC and Clearfil New Bond were not significantly modified or reduced by acidic dentin pretreatments. Gluma/Scotchbond adhesion was increased by several treatments but only maleic acid treatment produced shear bond strengths significantly higher than EDTA treatment. SEM evaluation of dentin treatments revealed a wide variety of morphological changes in the dentin surface with partial and complete removal of smear layer by acidic solutions, and only minor modification by amino acid solutions. Only maleic acid was capable of the complete removal of the smear layer and smear plugs coupled with extensive exposure of dentin collagen fibrils.     

Glass ionomer bond strength and treatment of dentin with polyacrylic acid

This investigation compared the effect of smear layer removal using various treatments with polyacrylic acid on the shear bond strength of glass ionomer restorative materials to dentin. Three brands of glass ionomer were applied to prepared dentin surfaces of extracted human molars, after one of four treatments with polyacrylic acid. Samples using dentin surfaces with the smear layer left intact served as controls. Comparison of mean shear bond strength values for all possible combinations of restorative material and polyacrylic acid treatment indicated that samples produced using 25% polyacrylic acid had lower (p less than 0.05) values in some instances. No other significant differences were found when test values were compared with each other or with control values. The authors concluded that removal of the smear layer does not enhance the dentin-glass ionomer restorative bond strength, as has been suggested by other investigators. Scanning electron photomicrographs indicate that treatment with higher concentrations of polyacrylic acid produces higher degrees of dentinal tubular orifice patency.     

Adhesion of dentin bonding agents after smear layer treatments.

The effect on bond strength of smear layer removal (40% polyacrylic acid or 10% phosphoric acid) versus smear layer conditioning for dentin bonding agents requiring conditioning was compared. Results indicated no difference in shear bond strength for groups in which the smear layer was conditioned or removed with phosphoric acid. Smear layer removal with polyacrylic acid resulted in lower bond strengths between DBAs and dentin than either phosphoric acid removal or conditioning (P less than 0.01). Scanning electron photomicrographs of dentin treated with each dentin bonding agent revealed various surface morphologies.     

Effect of removal of surface collagen fibrils on resin-dentin bonding.

OBJECTIVES: The aim of this study was to evaluate the effects of NaOCl at removing the demineralized layer by examining the morphology of the hybrid layer and measuring shear bond strengths after different dentin treatments. METHODS: Dentin disks were treated with: (1) 35% phosphoric acid (PA) 20 s; (2) PA treatment followed by 1.5% NaOCl, 2 min; (3) PA treatment, followed by a 10% NaOCl immersion for 120 h. SEM was used to analyze the morphology of dentin and its interface with dentin bonding agents (DBAs), while shear bond strength tests were used to measure adhesion. All specimens were then fractured into two halves: One half was inspected under SEM; the other half was sequentially placed in 10% PA followed by 12.5% NaOCl for 70 h, to remove all dentin from the resin replica of the original bonded interface. RESULTS: SEM observations showed that collagen fibrils were completely removed from the acid-etched surface by NaOCl treatment. The diameter and the size of dentinal tubules and the number of lateral branches of the tubules were increased following NaOCl treatment. NaOCl applied on dentin smear layers did not significantly modify their SEM morphology. Resin tags were larger in diameter after phosphoric acid/NaOCl treatment than after only phosphoric acid treatment. Resin-infiltrated dentin-layers were only observed after the single phosphoric acid (i.e. conventional etching) procedure, and were not observed after combined phosphoric acid/NaOCl treatment. Etched/NaOCl samples showed a lower bond strength using Scotchbond MP and 3M Single Bond, but were higher in Optibond FL and unmodified in Prime & Bond 2.0 groups when compared with acid-etched controls. Treatment of etched dentin with NaOCl for 120 h produced an unusual type of resin infiltration of mineralized dentin that could be called a "reverse hybrid layer" which may explain the mechanism of resin bonding to NaOCl treated dentin. SIGNIFICANCE: The use of acidic conditioners for exposure of the collagen matrix exposes a soft delicate mesh that can collapse, thereby interfering with resin infiltration. If acid-etching is followed by NaOCl treatment, high bond strengths can be achieved via "reverse hybrid layer" formation, a proposed new mechanism of micromechanical resin retention. This mechanism is not yet recommended for clinical use but demonstrates a new type of resin retention.     

Dentin permeability and bond strengths after various surface treatments

Numerous reports suggest that removal of the smear layer increases the bond strengths of some dentin adhesives while lowering the bond strengths of others. Smear layer removal also increases dentin permeability and wetness. The purpose of this study was to compare the permeability and shear bond strengths of occlusal vs. buccal dentin before and after removal of the smear layer with 6% citric acid and before and after substitution of the smear layer by topical oxalate treatment. Shear bond strengths of Scotchbond/Silux to smear layers were higher than those to acid-etched dentin. Oxalate treatment of acid-etched dentin increased bond strengths to levels that were higher than smear layer controls. Removal of the smear layer increased dentin permeability. This result was completely reversed by oxalate treatment.     

Shear bond strength of three resin based sealers to dentin with and without the smear layer

Bond strength of root canal sealers to dentin is an important property for the integrity of the sealings of root-canals. The purpose of this study was to test shear bond strength of three endodontic sealers (Diaket, AH Plus and Endo-REZ). The coronal two thirds of ninety extracted human third molars were removed. The smear layer of the exposed dentin surfaces were removed using 17% EDTA followed by 5.25% NaOCl and the teeth were randomly divided into two groups (n = 45). Group 1 was kept as control and in group 2, uniform smear layer was created using waterproof polishing papers. Three-mm long sections of polyethylene tubing were filled with freshly mixed sealer and placed on the dentin surfaces for conducting a shear bond strength test. The data was calculated as MPa and was statistically analyzed using a two way ANOVA, Kruskal-Wallis and Mann-Whitney U tests. A significant difference was found among the bond strength of the sealers, smear layer, and control groups. AH Plus sealer showed the highest bond strength in smear layer removed surfaces (p < 0.05). Pretreatment with EDTA/NaOCl affected bond strength of AH Plus. AH Plus had the highest bond to dentin with or without smear layer.     

次氯酸钠配合SmearClear清除根管玷污层的研究

目的:比较4种根管冲洗方法清除根管玷污层的效果,研究出有效去除根管玷污层的方法。方法:20个无龋单根前牙随机分为4组,A组:60℃30 g/L次氯酸钠液加170 g/L EDTA,#15K锉提拉冲洗;B组:60℃30 g/L次氯酸钠液加SmearClear,#15K锉提拉冲洗;C组:60℃30 g/L次氯酸钠液加170 g/LEDTA液超声荡洗;D组:60℃30 g/L次氯酸钠液加SmearClear超声荡洗。扫描电镜下放大2 500倍和4 000倍观察根尖1/3、根中1/3和根上1/3玷污层清除情况。按照根管壁玷污层清除情况和根管壁腐蚀程度的分级标准进行统计学分析。结果:①根管壁玷污层清除情况:4组在根上2/3区玷污层均有效去除,各组间差异无统计学意义(P>0.05),B组根尖1/3基本无玷污层,A、C、D组仅见少部分玷污层被去除,B组与A、C、D组差异有统计学意义(P<0.05);②根管壁腐蚀性比较:C、D组根上2/3区腐蚀度较大,而A、B组未见明显腐蚀。C、D组与A、B组相比差异有统计学意义(P<0.05),各组根尖1/3根管壁腐蚀度差异无统计学意义(P>0.05)。结论:SmearClear与60℃30 g/L次氯酸钠液联合应用能更有效的去除根管玷污层,且对根管壁表面结构无明显破坏。     

Comparison of the Efficacy of Maleic Acid and Ethylenediaminetetraacetic Acid in Smear Layer Removal from Instrumented Human Root Canal: A Scanning Electron Microscopic Study

IntroductionThe aim of this study was to assess, by scanning electron microscopic (SEM) analysis, the ability of 17% EDTA and 7% maleic acid in the removal of the smear layer from the human root canal system.MethodsEighty single-rooted human anterior teeth were subjected to standardized root canal instrumentation (step-back technique) and were irrigated with 2.5% NaOCl after each instrument. Based on the final irrigating solution used, samples were divided randomly into three groups: (1) the EDTA group: 17% EDTA+ 2.5% NaOCl (n = 30), (2) the maleic acid group: 7% maleic acid + 2.5% NaOCl (n = 30), and (3) the control group: 0.9% saline (n = 20). After final irrigation, teeth were prepared for SEM analysis to evaluate the cleaning of the coronal, middle, and apical thirds of radicular dentin by determining the presence or absence of smear layer. The data was statistically analyzed using the Kruskall-Wallis test.ResultsAt the coronal and middle thirds, there was no significant difference between EDTA and maleic acid. Both were equally efficient in the removal of smear layer. In the apical third, maleic acid showed significantly better smear layer removing ability than EDTA.ConclusionFinal irrigation with 7% maleic acid is more efficient than 17%EDTA in the removal of smear layer from the apical third of the root canal system, which is a crucial area for disinfection.     

Evaluation of the interaction between endodontic sealers and dentin treated with different irrigant solutions

Introduction

Dentin surface treatment with different substances might cause alterations in chemical and structural compositions of the human dentin. The aim of this study was to investigate the wettability of endodontic sealers in contact with dentin treated with 5.25% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX) in the presence or absence of smear layer.

Methods

Thirty-six dentin slices were used. They were irrigated with NaOCl and washed with distilled water (DW) to simulate irrigation during chemomechanical preparation. After this procedure, the samples were divided into 6 groups: group 1, DW (control); group 2, NaOCl + DW; group 3, CHX + DW; group 4, ethylenediaminetetraacetic acid (EDTA) + DW; group 5, EDTA + DW + NaOCl + DW; group 6, EDTA + DW + CHX + DW. The Ramé-Hart goniometer was used to measure the contact angle between the dentin surfaces and the AH Plus and Real Seal SE sealers. Data were statistically analyzed.

Results

With regard to the contact angle between AH Plus and treated surfaces, the values of contact angle were lower when CHX was used, regardless of the presence or absence of smear layer. When Real Seal SE was evaluated, in the absence of smear layer, CHX presented lower values of contact angle. In the presence of smear layer, the use of NaOCl and CHX did not favor the spread of the sealer.

Conclusions

The present study has revealed that smear layer removal and final flush with CHX favor the wettability of AH Plus and Real Seal SE sealers.     

Dentin treatment effects on the bonding performance of self-adhesive resin cements

Mazzitelli C, Monticelli F, Toledano M, Ferrari M, Osorio R. Dentin treatment effects on the bonding performance of self-adhesive resin cements. Eur J Oral Sci 2010; 118: 80–86. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
The effects of dentin surface treatments on the microtensile bond strengths and on the interfacial characteristics of self-adhesive resin cements were investigated. Flat dentin surfaces were obtained from human molars and were treated as follows: (i) no treatment of dentin; (ii) 0.1 M EDTA scrubbed for 60 s; or (iii) 10% polyacrylic acid applied for 30 s. Three self-adhesive cements were used to lute composite overlays on deep-coronal dentin surfaces in the presence of simulated pulpal pressure (15 cm of H₂O). Bonded specimens were cut into beams 1 mm thick and stressed in tension until failure. Fractured sticks were examined under a scanning electron microscope. Additional specimens were stained with Masson's trichrome and observed under light microscopy for interfacial evaluations. The bond strength to dentin of the hydrophobic and solvent-free cement (RelyX Unicem) was unaffected by the tested dentin treatments. The bond strength of the 2-hydroxyethyl methacrylate (HEMA)-based cement (Bis-Cem) decreased after treatment of dentin with EDTA and/or polyacrylic acid. The hydrophilic and water-containing cement (G-Cem) attained a higher bond strength when luted on polyacrylic acid-conditioned dentin. In conclusion, smear layer removal, opening of dentinal tubules, and the water content of dentin differently influence the bond strengths and the interfacial characteristics of self-adhesive cement–dentin interfaces.     

Dentin smear layer: an asset or a liability for bonding?

Despite concerns and claims that the smear layer on dentin is undesirable for bonding, supportive evidence is lacking. The clinical efficacy of various agents for smear layer removal and the effect of smear layer removal on the bond strengths of a glass-ionomer cement and three representative dentin bonding agents were examined. For all but one dentin bonding agent (Gluma), a 15-second treatment with 17% EDTA caused a reduction in bond strength. For Gluma, no significant bond was obtained without EDTA treatment. While Gluma probably bonds via dentinal collagen, the other materials interact primarily with dentinal calcium. Removal of the smear layer for adhesives reliant on the presence of calcium is therefore undesirable. The clinical effects of some agents proposed for smear layer removal were examined by SEM of replicas.     

Fibrin clot adhesion to dentin conditioned with protein constructs: an in vitro proof-of-principle study

OBJECTIVES: Periodontal regeneration is contingent on the adsorption, uninterrupted adhesion, and maturation of a fibrin clot to a periodontally compromised root surface. Clot adhesion appears vitally dependent on the formation of a resilient union between the clot and the root surface. Root surface demineralization will remove a root surface smear layer exposing dentin tubules and collagen matrix for enhanced clot adhesion. Recently, protein constructs have been introduced to condition the root during periodontal surgery. The effect of such root conditioning on clot adhesion has not been clarified. The objective of this study was to evaluate clot adhesion to protein conditioned dentin surfaces. METHODS: Human dentin blocks (4 x 6 x 1 mm) were exposed to a saturated citric acid solution (CA) or a commercial ethylenediaminetetraacetic acid (EDTA) preparation using standardized protocols. Some dentin blocks were additionally conditioned with proteins, either bovine serum albumin (BSA) or an enamel matrix protein preparation (EMP). Fresh human whole blood was applied to the blocks. The blood was allowed to clot for 20 min. in a humidified chamber. The dentin blocks were rinsed 3 x 5 min. in phosphate-buffered saline under standardized conditions to test clot adhesion. They were then processed for scanning electron microscopy (SEM). Two masked examiners independently evaluated the SEM images. RESULTS: CA removed the dentin smear layer, exposing dentin tubules and collagen. EDTA appeared less efficacious leaving smear layer residues. The BSA or EMP application resulted in a surface morphology similar to that of a smear layer. Fibrin clot adhesion was best supported by the CA-treated dentin surface. Forces produced by the rinse protocol partially removed the fibrin clot from EDTA-treated surfaces. BSA- or EMP-treated surfaces poorly retained the fibrin clot. CONCLUSIONS: CA surface demineralization removes a dentin surface smear layer to promote adhesion of a fibrin clot. The EDTA gel appears less effective. Further conditioning of the dentin surface with protein constructs produces a surface morphology similar to that of the smear layer with poor fibrin clot retention.     

The effect of different irrigation protocols on smear layer removal in root canals of primary teeth: a SEM study

Objective: The purpose of this study was to compare the efficacy of different irrigation protocols on smear layer removal in root canals of primary teeth by scanning electron microscopy (SEM).

Material and methods: The study was conducted with 40 extracted maxillary primary incisor teeth divided into four groups (n?=?10) as 1% sodium hypochlorite (NaOCl), 10% ethylenediaminetetraacetic acid (EDTA)+1% NaOCl, 6% citric acid (CA)+1% NaOCl, and 0.9% physiological saline (PS). After the irrigation procedures, root canal walls were examined by SEM and the efficacies of irrigation solutions in smear layer removal were scored and compared. Data were analyzed using Kruskal–Wallis, Friedman and Siegel Castellan tests.

Results: The smear layer removal was found to be statistically more effective in groups of 10% EDTA + 1% NaOCl and 6% CA + 1% NaOCl when compared with the other groups (p?<?.05). Smear removal efficacy was statistically significantly higher in coronal and medium thirds when compared with the apical regions in the experimental groups.

Conclusions: It was concluded that 10% EDTA + 1% NaOCl and 6% CA + 1% NaOCl could be alternative irrigation protocols regarding smear layer removal. However, due to the absence of erosive dentinal changes, it might be suggested that using 6% CA + 1% NaOCl can be recommended compared to 10% EDTA + 1% NaOCl in primary root canals.     

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目的评价不同表面处理方法对激光预备牙本质形态学变化和黏结强度的影响。方法2013年5月至7月在中国医科大学附属口腔医院收集20～40岁新鲜拔除的活髓第三磨牙20颗及根尖发育完全的前磨牙8颗,铒、铬：钇钪镓石榴石（Er,Cr：YSGG）激光处理暴露的牙争面牙本质,然后按照不处理、37％磷酸酸蚀、自酸蚀及0．5mol／LEDTA调节各自分为4组,使用扫描电子显微镜（SEM）观察前磨牙牙本质处理面形态;第三磨牙使用Adper easy bond或Single bond 2黏结,Z350树脂逐层堆积树脂冠后,制作哑铃型试件进行微拉伸黏结强度测试,采用单因素方差分析进行组间差异比较。结果SEM观察发现：前磨牙激光预备后不处理组（对照组）牙面不规则,无玷污层,牙本质小管开放;磷酸酸蚀组牙本质表面最规则,自酸蚀组和EDTA处理组处理后表面变化不如磷酸酸蚀组明显。微拉仲黏结强度测试结果显示,第三磨牙分组后的3种处理方式牙本质黏结强度均显著高于对照组（P〈0．05）,磷酸酸蚀组黏结强度最强（P〈0．05）,而自酸蚀组及EDTA处理组差异无统计学意义（P〉0．05）。结论37％磷酸酸蚀、自酸蚀及0．5mol／LEDTA调节3种处理均可提高激光预备的牙本质黏结强度,37％磷酸酸蚀组获得最佳短期黏结效果。     

A scanning electron microscopic evaluation of root canal wall cleanliness after calcium hydroxide removal using three irrigation regimens

AIMS: The aims of this in vitro study were to evaluate debris and smear layer elimination capability effectiveness of 5.25% sodium hypochlorite (NaOCl) after calcium hydroxide removal from the root canal and to determine if ethylenediaminetetraacetic acid (EDTA) and citric acid have any additional effects on debris and smear layer removal. METHODS AND MATERIALS: All irrigation regimens are associated with ultrasonics. Thirty-six pulpless single-rooted teeth were divided into three groups on the basis of the irrigation regimen, namely 5.25% NaOCl alone, 5.25% NaOCl with 17% EDTA pH 7 (NaOCl-EDTA), and 5.25% NaOCl with 50% citric acid (NaOCl-CA). All root canals were instrumented with the Protaper rotary system (Dentsply-Maillefer, Ballaigues, Switzerland) using a crown-down approach. The apical foramen of each tooth was enlarged to a size 30 with a 0.09 taper. After longitudinal sectioning, the dentin walls were microphotographed using scanning electron microscopy (SEM) at a 1500x magnification. Using a grid and a 5-step scale these microphotographs were scored by three investigators in order to evaluate debris and smear layer residuals. Data were statistically evaluated using Kruskal-Wallis and Mann-Whitney tests. RESULTS: In the coronal third the lowest score obtained with NaOCl-CA was similar to NaOCl-EDTA. When using NaOCl-EDTA, mean debris scores were similar to the control group (NaOCl) and lower than NaOCl-CA in the middle and apical thirds. Regarding the mean smear layer score, NaOCl-CA was the lowest in the coronal, middle, and apical thirds with a statistically significant difference (p < 0.001). CONCLUSION: When the total surface of the root was evaluated, NaOCl-EDTA was superior in removing debris, but the association of NaOCl-CA enabled the most effective removal of the smear layer.     

Effect of endodontic irrigation on bonding of resin cement to radicular dentin

The influence of endodontic irrigation on shear bond strengths of resin cement to radicular dentin was investigated. Human radicular dentin blocks were divided into four groups and subjected to one of four endodontic irrigations: ethylenediaminetetraacetic acid (EDTA) group, 17% EDTA for 60 s; EDTA/sodium hypochlorite (NaOCl) group, 17% EDTA for 60 s followed by 10 ml of 5% NaOCl for 15 s; NaOCl group, 10 ml of 5% NaOCl for 15 s; and control group, no treatment. Morphological changes of dentin surface after endodontic irrigation were observed by scanning electron microscopy (SEM). A resin block was bonded to the radicular dentin after irrigation using resin cement with either wet-bonding (Uni-Etch/One-Step; Bisco) or self-etching (Tyrian SPE/One-Step Plus; Bisco) adhesives. Shear bond strengths were measured and the penetration of resin tags into dentinal tubules at resin-dentin interface was observed by SEM. With the wet-bonding system, the shear bond strengths for the EDTA/NaOCl group, in which dentinal tubules openings and uniform resin tag penetration into dentinal tubules were observed, were significantly higher than the EDTA and control groups. With the self-etching system, the shear bond strengths were significantly lower in the EDTA group compared with the NaOCl and control groups. The effects of endodontic irrigation on the bonding of resin cement to radicular dentin depended on the dentin bonding system used.     

The in vitro morphological effects of some current pre-treatments on dentin surface: a SEM evaluation

This in vitro study morphologically evaluated the effect of some current surface pre-treatments on dentin, using scanning electron microscopy, and related these morphological alterations to clinical implications. The labial surfaces of 30 bovine lower incisors were ground to obtain a flat dentin surface and were finished with 600-grit SiC paper to produce standardized smear layers. The teeth were randomly divided into six groups of five each. Group 1 was the control group, smear layer covered dentin; Group 2 was etched with 37% phosphoric acid (PA) for 15 seconds; Group 3, 37% PA for 15 seconds, followed by 10% NaOCl for 60 seconds; Group 4, 10% NaOCl for 60 seconds; Group 5, a self-etching primer (Clearfil SE Bond, CSEB-primer) was applied for 20 seconds; Group 6, CSEB-primer for 20 seconds, followed by NaOCl for 60 seconds. The specimens were fixed, dehydrated, dried and analyzed by SEM. Treatment with 37% PA removed the smear layer, funneled the tubules and resulted in a collagen-rich surface which appeared to have collapsed in its outermost part, producing a dense surface layer covered with silica particles. When 37% PA treatment was followed by 10% NaOCl, the collagen network was removed to reveal an eroded, rough mineral surface with numerous lateral branches and larger than normal tubular orifices. The action of 10% NaOCl on the smear layer-covered dentin showed no significant alteration in surface morphology. The treatment with CSEB-primer dissolved the smear layer but only partially dissolved the smear plugs. The tubules did not present the typical funnel shape seen following PA treatment. These morphological aspects on dentin surface must influence bonding results. The dentin surface alterations produced by PA appeared to be a very severe demineralization pattern, quite irregular and less permeable to monomer infiltration, while the surface provided by the self-etching primer appeared to be a more uniform, less porous surface, and the association with simultaneous monomer infiltration may reduce the occurrence of mistakes in clinical bonding procedures.     

NaOCl and EDTA irrigating solutions for endodontics: SEM findings.

Premolars roots of humans were manually instrumented with K-type files and irrigated with different solutions to evaluate the rate of cleaning of endodontic surface. Root canals irrigated with 0.9% saline solution or H2O2 (10 volumes) showed the presence of predentin and amorphous smear layer. Thick smear layer was always present on endodontic walls rinsed with 5% solution of NaOCl. Specimens treated with 0.2% solution of EDTA showed partially clean dentinal tubules orifices and remnants of a thin smear layer. Occasional uninstrumented areas of the same roots presented smear layer remnants and predentin with calcified bacteria. The root canals irrigated with NaOCl and EDTA solutions alternated after each instrument showed at the dentin surface thick smear layer: only few dentinal tubules orifices were visible. Endodontic surface of root canals irrigated with NaOCl during instrumentation and finally rinsed with EDTA solutions showed the most homogeneous ultrastructural pictures: partially clean dentinal orifices were detectable in the whole canals.     

Closing of dentinal tubules by glutardialdehyde treatment, a scanning electron microscopy study

The properties of dentin are strongly influenced by the so-called smear layer. This layer is always present on the dentin surface after cutting, drilling, sawing, etc. The smear layer can be removed by various chemical treatments, such as those of acid etching or ethylenediaminetetraacetic acid (EDTA). These treatments remove the smear layer and open the tubules. In this paper, the effect on the smear layer of human dentin of treatment with a 2% glutardialdehyde (GDA) solution at pH 3.5 for 2 min and a 0.5-M EDTA solution at pH 7.4 for 4 min was investigated by scanning electron microscope (SEM). The dentin samples were dried by air or critical-point drying before SEM photography was employed. The number of open dentin tubules was quantified on micrographs of EDTA- and GDA+EDTA -treated dentin. The results show that the GDA treatment fixed part of the smear layer and the superficial dentin surface in such a way that at least 50% of the tubules remained closed after EDTA treatment. By closing the dentinal tubules, the GDA-fixed layer might have a positive effect on dentin hypersensitivity, root caries, and bonding of composite to dentin.