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PubMed1997

Smear layer formed by different root planing modalities and its removal by an ethylenediaminetetraacetic acid gel preparation.

The purpose of the present study was (1) to examine smear layer formation following different root planing modalities, and (2) to evaluate its removal and the exposure of collagen using an ethylenediaminetetraacetic acid gel preparation. Twenty-four periodontitis-affected human teeth were mechanically root planed. Twelve teeth were etched with an ethylenediaminetetraacetic acid gel preparation. The surfaces were examined by a scanning electron microscope. The results showed that root planing resulted in a smear layer covering the root surfaces, irrespective of treatment modality. The smear layer could be efficiently removed with the ethylenediaminetetraacetic acid gel preparation. During this process, collagen fibers were exposed to varying degrees.

Acid Etching, Dental↗
PubMedDate not supplied

Dentin bonding agents and the smear layer.

The morphology and treatment of the smear layer are discussed. Also included are a review of dentin bonding agent classification and chemistry, and a summary of recent bond strength research results. Finally, the current status of dentin bonding agents is discussed.

Dental Bonding↗
PubMed2003

Bonding of mild self-etching primers/adhesives to dentin with thick smear layers.

PURPOSE: To compare the microtensile bond strength (microTBS) and the ultrastructure of resin-dentin interfaces of four self-etching systems that were applied to dentin with thick smear layers. METHODS: Human third molars were ground with 180-grit silicon carbide papers to expose deep coronal dentin. A 3-mm vertical slit was made along the diameter of each tooth to fit a glass cover slip, dividing each tooth into two bonding surfaces. Two 2-step, self-etching primers (ABF experimental system and Imperva Fluoro Bond) and two single-step, self-etching adhesives (One-Up Bond F and AQ Bond) were examined. Adhesives were applied to one side of the teeth passively, and to the other side with continuous agitation for the same self-etching period. Incremental composite buildups were performed and beams with cross-sectional areas of 0.81 mm2 were prepared for microTBS evaluation. Demineralized, bonded specimens were processed for TEM examination. RESULTS: Two-way ANOVA showed that both the adhesive type and the application mode significantly affected microTBS results. However, the interaction of these two factors was not statistically significant (P > 0.05). For each adhesive, agitation produced significantly higher microTBS than passive application. With passive application, all systems diffused through thick smear layers and formed thin hybrid layers in intact dentin. With continuous agitation, smear layers were completely dispersed or dissolved, and thicker hybrid layers with upstanding collagen fibrils were observed.

Analysis of Variance↗
PubMed1993

Smear layer removal with different concentrations of EDTA-ethylenediamine mixtures.

The purpose of this study was to observe the effectiveness of EDTA and ethylenediamine mixtures in removing the smear layer from prepared root canal walls following instrumentation. Thirty-five freshly extracted, single-rooted maxillary anterior teeth were used. After the preparation of access cavities and establishing the working length, the apical foramen of each canal was sealed with casting wax. All canals were then sequentially enlarged with K-type files to size 50. The sample was divided into seven groups of five teeth. The teeth in the control group were irrigated with saline solution. The specimens in the other groups were irrigated with 10 and 20 ml of three different EDTA-ethylenediamine mixtures. A scanning electron microscopic evaluation of the canal walls following irrigation showed that the superficial layer was totally removed and the openings of the dentinal tubules were patent. Only at the coronal third of the teeth in group 4 and the apical thirds in groups 2 and 4 was a moderate smear layer observed. The most favorable results were obtained with groups 5, 6, and 7. The results show that the smear layer can be totally removed by using 10 ml of a four-to-three by volume mixture of EDTA and ethylenediamine for irrigation of instrumented root canals.

Dentin↗
PubMed1998

[Influence of smear layer and adhesive resin on the retentive force of amalgam restoration in vitro study].

UNLABELLED: The purposes of this in vitro study were to determine whether removing of smear layer and using of self-cured adhesive can increase retentive strength of amalgam restoration and to understand the adhesive mechanism between amalgam and adhesive. Class I cavities without mechanical retention were prepared in the occlusal surfaces of 45 extracted molars which were randomly divided into 3 groups. Group 1: 10%EDTA(pH 7.4) was applied to cavity walls for 1 minute prior to amalgam condensation. Group 2: 10%EDTA was applied in the same manner as in group 1, then the walls were water-sprayed and dried. Miradapt adhesive was applied, and amalgam must be packed into cavity before the adhesive cures. CONTROL GROUP: no special treatment before amalgam condensation. The tensile strength of the restorations were measured. The adhesive interface of two samples from group 2 were evaluated by SEM and EDS. As a result, removing smear layer had little effect on retentive force of amalgam (P > 0.05), while removing smear layer and applying adhesive improved the retentive strength of amalgam fillings significantly (P < 0.05), and there were micromechanical interlock between amalgam and adhesive according to SEM and EDS observation.

Adhesives↗
PubMedDate not supplied

SEM study of different treatments of the smear layer on different cavity walls.

The present study evaluated the effects of slightly demineralizing treatments on dentinal cavity walls, since some recently developed adhesive procedures are applied over the smear layer. Ten experimental treatments--mechanical, chemical or mechanical/chemical--were applied on MOD cavity walls prepared in vitro with diamond burs. The dentinal surface of a lateral and of a pulpal wall of each cavity was evaluated through scanning electron microscopy, and the effects of the treatments were compared. All treatments except air/water spray removed some of the smear layer, and slight differences were observed regarding the studied cavity walls: on dentin from pulpal walls the enamel hatchet associated with tannic acid produced a better effect than the other treatments, and on dentin from lateral walls the biological detergent rubbed with cotton pellets was a little more effective than the other treatments. The effect of the smear layer treatment on dentin is different according to the wall and to the applied treatment.

Acid Etching, Dental↗
PubMed1993

A pilot study of exposure of the smear layer to tannic acid solutions.

This study examined the effects of tannic acid on smear layer removal. Class V cavities were prepared on the buccal surfaces of extracted human molars with a No. 1557 high-speed carbide bur under water cooling for cutting and a No. 701 low-speed steel bur for finishing. They were then washed with water followed by an application of 2%, 5%, 10%, 15%, 20%, or 25% tannic acid solution in water for 15, 30, or 60 seconds. The axial wall dentin surfaces were examined with scanning electron microscopy. This examination showed that an application of 2% tannic acid for 60 seconds or 5% tannic acid for 15, 30, or 60 seconds effectively removed the smear layer, leaving the dentinal tubules occluded. The dentinal surfaces treated with 40% phosphoric acid for 15 seconds showed many exposed dentinal tubules with flared orifices.

Acid Etching, Dental↗
PubMed2006

Leakage along apical root fillings with and without smear layer using two different leakage models: a two-month longitudinal ex vivo study.

AIM: To compare two different experimental models when measuring leakage along root fillings with or without smear layer. METHODOLOGY: One hundred and twenty single-rooted teeth were prepared to size 50 and allocated to two groups: fluid transport model (n = 60) and glucose penetration model (n = 60). The roots in each group were divided into three subgroups of 20 teeth each. Smear layer was left in place in group 1 but removed in groups 2 and 3. In groups 1 and 2 canals were filled with laterally compacted gutta-percha cones and AH 26. Group 3 was laterally compacted with Resilon cones and Epiphany sealer. The coronal portion of the filling was removed to assure only 4 mm of filling remained in the canal. Leakage of glucose was evaluated by measuring its concentration once a week for a total period of 56 days using a glucose penetration model. Fluid transport was evaluated by measuring the movement of an air-bubble using a fluid transport model, 1 and 8 weeks after canal filling. Differences between the groups in glucose concentrations and fluid transport were statistically analysed with the Kruskal-Wallis and the Mann-Whitney tests. The level of significance was set at alpha = 0.05. RESULTS: Glucose penetration was significantly different between the three groups after the first 8 days (P < 0.05). Resilon leaked the most throughout the experiment period. No significant difference (P > 0.05) existed between the two gutta-percha groups at all time intervals (Mann-Whitney test). In the fluid transportation model, no statistically significant differences were observed between all three experimental groups (P > 0.05) at either 1 or 8 weeks after filling (Kruskal-Wallis test). CONCLUSIONS: Under the conditions of this study, the glucose penetration model was more sensitive in detecting leakage along root fillings. Removing the smear layer before filling did not improve the sealing of the apical 4 mm of filling. Resilon allowed more glucose penetration but the same amount of fluid transport as the gutta-percha root fillings.

Dental Leakage↗
PubMed1994

An ultrastructural study of the smear layer: comparative aspects using secondary electron image and backscattered electron image.

The aim of this investigation was to study the influence of three irrigation procedures on the composition, structure, and aspect of the smear layer within root canals. Three homogeneous groups were prepared without irrigation, with physiological serum, or with Dakin (dilute, neutral solution of sodium hypochlorite). Root canals were instrumented with Rispi Reamers mounted on a counterangle Giromatic. The irrigating solution was delivered with an endodontic irrigation needle. Modifications were observed by scanning electron microscope using secondary electron imaging and backscattered electron imaging. Instrumentation without irrigation produced a very thick smear layer that appeared in backscattered electron imaging as a compact assembly or organic and inorganic components. Instrumentation using Dakin produced canal walls that were less smeared, and the pockets of debris remaining were smaller in size than when using physiological serum. When the root canals were irrigated, the smear layer appeared as a double layer, one superficial and the other deep. The layers were predominantly inorganic with Dakin.

Blood↗
PubMed2002

Effect of smear layer thickness on bond strength mediated by three all-in-one self-etching priming adhesives.

PURPOSE: The aim of this study was to investigate the effect of dentin smear-layer thickness on the bond strength of three all-in-one adhesives of different acidity. MATERIALS AND METHODS: Peripheral dentin was prepared by wet grinding on SiC papers (80-, 180-, 240-, 320-, 400-, 600-, 4000-grit), and by turbine cutting with supercoarse, coarse, medium, fine, or extrafine diamond burs. The smear layer thickness (SLT) was measured microscopically. The relationship between SLT and average grain size of the abrasives used to prepare the dentin surface was described by regression analysis. Shear bond strength (SBS) was determined for the following adhesives: AC Bond, pH 2.1 (experimental, Heraeus); AQ Bond, pH 2.5 (Sun Medical); and Prompt L-Pop, pH 1.1 (3M-Espe). Six specimens were tested for each adhesive on dentin ground with each of the seven SiC grit sizes. The mode of failure was inspected by SEM. SBS data were analyzed by one-way ANOVA and Fisher's PLSD test at p < 0.05. RESULTS: A logarithmic relationship between SLT and grain size of the abrasives was established. The coefficient of determination R2 for the regression line was 0.803. Shear bond strengths for the individual adhesives did not differ significantly by SiC grit size. SBS of AC Bond (18.3 MPa) was greater than the SBS of AQ Bond and Prompt L-Pop (16.9 MPa). Cohesive failures were consistently found in resin composite or adhesive. CONCLUSION: Smear layer thickness increased with decreasing SiC grit numbers and increasing diamond bur roughness. In spite of the widely differing acidity, all three adhesives tested were equally effective over the range of SLT from 2.6 microm through 0.9 microm.

Adhesives↗
PubMed1997

[In vitro evaluation of the cytotoxicity of composite resin in the presence or absence of smear layer].

BACKGROUND: The aim of the present research was to investigate the cytotoxicity of the composite resins applied on dentine samples with different smear layer removal, by using cell cultures and LDH determination. MATERIALS AND METHODS: Ninety-eight caries-free third molars recently extracted were used. Transversal sections, 500 mu thick, were obtained. A simulated pulpar chamber was constructed allowing to give lodging in the inferior side to the cell culture and in the superior side to the dentine section with the composite resin. LDH activity was then determined by using a spectrophotometer. BACKGROUND: The results show that the composite resins are surely cytotoxic if directly applied on the dentine. The smear layer is able to reduce the transdentinal diffusion of composite resin toxicity. On the basis of the data obtained it is suggested that in vivo, being necessary to eliminate the smear layer due to its bacterial contents, it is possible in the deep cavities, to partially remove with EDTA maintaining the smear plugs after their disinfection. Nevertheless EDTA application should not exceed 30 seconds.

Cell Culture Techniques↗
PubMed1994

Disturbance of the dentinal smear layer by acidic hemostatic agents.

The pH of nine commonly used hemostatic agents was measured. Three measurements were recorded for each solution, and values ranged from 0.7 to 2.0. The effect of exposure to one hemostatic material, ferric sulfate solution (Fe2(SO4)3), on the dentinal smear layer was investigated. Prepared extracted teeth were exposed for periods ranging from 30 seconds to 5 minutes to an acidic ferric sulfate-based hemostatic agent. A smear layer was clearly demonstrated on a control specimen; however, the dentinal smear layer was rapidly removed by exposure to the hemostatic agent, and peritubular dentin was lost after prolonged exposure.

Acid Etching, Dental↗
PubMed2000

A comparative study of smear layer removal using different salts of EDTA.

Three solutions of EDTA--a 15% concentration of the alkaline salt, a 15% concentration of the acid salt, and a 25% concentration of the alkaline salt--were evaluated for smear layer removal in root canal systems. All solutions were adjusted to pH 7.1 using either NaOH or HCl. When the EDTA solutions were alternately used for root canal irrigation with 5.25% NaOCl, they completely removed the smear layer in the middle and coronal thirds of canal preparations, but were less effective in the apical third. None of the EDTA solutions by themselves were effective at completely removing the smear layer at any level. The alkaline tetrasodium salt, pH adjusted with HCl, is more cost effective and performed equally as well as the more commonly used disodium salt.

Acids↗
PubMed1994

Influence of smear layer on the coronal leakage of Thermafil and laterally condensed gutta-percha root fillings with a glass ionomer sealer.

The effect that two methods of root canal obturation, combined with removal of the smear layer, had on coronal leakage was studied in vitro. Single-rooted teeth with mature apices were prepared chemomechanically and divided into two groups of 72 teeth each. One of the groups was treated with 40% citric acid and 2% sodium hypochlorite to remove the smear layer. The teeth were then subdivided and obturated using the glass ionomer sealer, Ketac Endo and either lateral condensation or Thermafil. After storage for 7 days or 4 months, the specimens were evaluated for coronal leakage using Indian ink. After 90 h, each root was split longitudinally and the maximum extent of leakage was measured using a stereomicroscope at x6 magnification. After 7 days, there was significantly less leakage in those teeth obturated with Thermafil without smear layer compared with the other groups (p < 0.05). After 4 months, there was no significant difference in leakage between the groups (p > 0.05).

Dental Leakage↗
PubMed1990

A scanning electron microscope (SEM) study of the smear layer in root canals.

A Scanning Electron Microscope was used to study the so-called "smear layer" produced in biomechanically prepared root canals. Fine, freshly-extracted incisors were used and the canals instrumented with K-type files and irrigated with 5% NaOCI and 3% H2O2. The structure of the "smear layer" produced was investigated.

Dentin↗
PubMed2006

Evaluation of the smear layer removal effectiveness of EDTA using two techniques: an SEM study.

Obtaining the cleanest canal possible before obturation is one of the goals of endodontic treatment. The purpose of this study was to compare the smear layer removal capability of ethylenediamine tetra-acetic acid (EDTA) application with passive ultrasonic and cotton wrapped on reamer activation. Twelve extracted human teeth with single root canals were used for the study. They were conventionally hand instrumented using reamers and K files. The apical aspect of the canals was enlarged to a #40 file. The teeth were divided into 4 four groups, instrumented and irrigated as follows: Group-A EDTA agitated at the end of preparation with cotton wrapped on a reamer for 1 min; Group-B EDTA applied with ultrasonic agitation for 1 min; Group-C irrigated with EDTA+sodium hypochlorite (NaOCl) (negative control group); and Group-D irrigated with distilled water (positive control group). After scanning electron microscopic study at three different levels, smear layer and dentinal tubules were scored. Means were tested for significance using the Z test. When the techniques were compared, the cotton wrapped on reamer agitation method was as successful as the ultrasonic activation of the files. Although all groups had significantly higher smear layer scores at apical compared to coronal sections, no significant differences were recorded.

Chelating Agents↗
PubMed1992

An evaluation of smear layer with various desensitizing agents after tooth preparation.

According to hydrodynamics, any agent blocking the dentinal tubules reduces the flow of fluids and diminishes hypersensitivity. The properties of the desensitizing agents that sponsor tubular occlusion and the barrier efficiency resulting from the interaction of the smear layer with test materials were examined with the scanning electron microscope and energy-dispersive x-ray microanalysis. Selected dentinal desensitizing was accomplished with burnishing procedures, cavity varnish, calcium hydroxide, and topical fluoride. Subjective evaluations were also recorded clinically after tooth preparation. This investigation indicated that the smear layer did not protect against zinc phosphate cement, and that cavity varnish prevented the formation of the smear plugs. The smear layer and plugs were basically composed of calcium and phosphorus, the major ingredients of dentin.

Adult↗
PubMed1991

Dentine hypersensitivity--effects of some proprietary mouthwashes on the dentine smear layer: a SEM study.

Exposed dentine may be sensitive to stimuli depending on the patency of the dentinal tubules. Most abrasive elements tend to produce a smear layer which obturates the dentinal tubules. This layer is easily removed by a number of erosive agents, particularly dietary acids. Mouthwashes are increasingly used and largely investigated for possible benefits to dental health. Rarely do studies assess potential detrimental activity. The aim of the present study was to examine effects of mouthwashes on dentine. Smear layers artificially produced on dentine sections were exposed, for time periods ranging from 3 to 300 min, to mouthrinses alone, or with subsequent brushing for 2 min using water or a fluoride toothpaste. Assessments were made by scanning electron microscopy. Of the nine rinses tested, six produced no consistently observable changes compared to water treated controls at any time period with or without brushing. A hexetidine rinse and a fluoride/antiseptic rinse both exposed tubules after exposure times of 2 h and longer, an effect enhanced by post-treatment brushing. A phenolic antiseptic rinse consistently removed the smear layer from specimens, an effect enhanced by brushing such that after 10 min exposure and 2 min brushing many tubules were open at the surface. The results indicate that the use of some mouthrinses could predispose to excessive tooth substance loss and dentine hypersensitivity, particularly if used prior to toothbrushing. There is a need to determine whether the intermittent use of some mouthrinses produces cumulative effects on dentine.

Benzoates↗