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PubMed1999

The removal of the smear layer using the Quantec system. A study using the scanning electron microscope.

AIM: The aim of this study was to determine the ability of the Quantec Series 2000 rotary nickel-titanium endodontic system to remove dentinal debris and smear layer produced during canal preparation. METHODOLOGY: A first group (control) of 12 curved root canals was prepared using conventional manual instruments and the step-back technique. A second group of 12 curved root canals was instrumented using the complete Quantec sequence according to the manufacturer's instructions. In both groups, irrigation was performed using a 3% NaOCl solution. The canal walls were observed under a scanning electron microscope and the coronal, middle and apical thirds of each canal photographed at a magnification of 500. The views were divided into 10 subareas by overlaying a grid, and the absence or presence of a smear layer was rated and scored on three appearances using the scale described by Ciucchi et al. (1989). RESULTS: The scores were higher (i.e. less debris was present) in the middle third (P < 0.0001) and in the apical third (P < 0.0001) of canals prepared with the Quantec system when compared with those prepared with K-files. Nevertheless, in canals prepared with Quantec instruments, the scores were significantly higher in the coronal third compared with the apical third (P < 0.005). CONCLUSIONS: The Quantec rotary system produced cleaner canal walls than conventional manual instrumentation, particularly in the middle and apical thirds. This finding may imply that stresses applied to the cutting regions of Quantec instruments by accumulation and compression of the smear layer are minimized.

Dental High-Speed Technique↗
PubMed1996

SEM analysis of smear layer removal after manual and automated handpiece root canal preparation.

Scanning electron microscopy was used to analyze the smear layer removal after root canal preparation by a manual technique and by an automated handpiece, the Canal Finder System (CFS). When 1% sodium hypochlorite was used as the irrigating solution, both manual and CFS techniques showed root canal walls with a dense smear layer obscuring the dentinal tubules entrance plus a large amount of debris. Root canal walls of the group of teeth treated with a chelating agent (EDTA) for 5 min and a final flush, after the preparation, with 1% sodium hypochlorite as an irrigating solution showed the cervical, middle and apical thirds extremely smooth and clear.

Dental High-Speed Equipment↗
PubMed1981

The effects of cavity smear layer removal on experimental marginal leakage around amalgam restorations.

Unvarnished freshly-packed dental amalgam restorations leak initially. However, with time, a marginal seal is usually effected. It is not known whether the smear layer which forms during cavity preparation is associated with this leakage pattern. This study was undertaken to evaluate experimental marginal leakage around amalgam restorations (left in situ for one and 12 wk) which had been placed in cavities prepared with and without removal of the smear layer in vital and devitalized teeth. The cavities were obturated with two types of dental amalgams, a conventional and a dispersed-phase amalgam. The excised teeth restorations were subjected to a fluorescent dye marginal leakage experiment. All of the short-term specimens leaked severely, but some of the long-term specimens displayed significant sealing properties. No significant differences were found between the two types of amalgams. However, the non-vital tooth specimens and cavities without smear layers displayed significantly improved sealing properties.

Animals↗
PubMed2006

A scanning electron microscopic study of debris and smear layer remaining following use of AET instruments and K-flexofiles.

AIM: To compare in vitro the cleanliness of root canal walls following automated or manual instrumentation. METHODOLOGY: Thirty extracted human maxillary central incisors, maxillary and mandibular canines and premolars with single root canals were used in this study. The teeth were divided into two groups. In group 1 (20 teeth) automated canal preparation was performed using Anatomic Endodontic Technology (AET). In group 2 (10 teeth) manual instrumentation was performed with K-Flexofiles. Irrigation was performed using alternately 3.00% NaOCl and 18% EDTA, followed by rinsing with saline. The roots were split longitudinally into halves and the canals examined using a scanning electron microscope. The presence of debris and smear layer was recorded at coronal, middle and apical thirds of root canals using a four-step scoring scale. Mean scores for debris and smear layer were calculated and statistically analysed for significance (P<0.05) between and within groups, using the Mann-Whitney-Wilcoxon and Friedman nonparametric tests. RESULTS: At coronal and middle thirds the root canals prepared with manual instrumentation had significantly less surface debris on the canal walls compared with canals prepared with AET (p<0.05). At apical third root canals prepared with manual instrumentation had significantly more debris compared with AET group. The amount of smear layer was greater in the apical than in the coronal and middle thirds of the root and significantly less amount was in the AET group (P<0.05). CONCLUSIONS: Complete cleanliness was not achieved by any of the techniques and instruments investigated. It may be inferred that the choice between AET and hand instrumentation should be based on factors other than the amount of root canal debridement, which does not vary high significantly according to the instruments used.

Chelating Agents↗
PubMed2004

Effect of the hydration status of the smear layer on the wettability and bond strength of a self-etching primer to dentin.

PURPOSE: To evaluate the microtensile bond strength (MTBS) of a resin-based composite to smear layer-covered dentin using a self-etching primer, Clearfil SE Bond (CSEB), under two different hydration states. Surface roughness and wettability (contact angle measurements) of water and the CSEB primer were also evaluated on this substrate. METHODS: Contact angle (CA) measurements were performed on four caries-free extracted human third molars. The specimens were sectioned parallel to the occlusal surface to expose the moderately deep dentin and ground flat (180-grit SiC) under water to provide uniform flat surfaces. In two samples, the smear layer was completely air-dried; in the other two specimens, the smear layer was briefly air-dried. Contact angle measurements were performed to assess wettability of water and CSEB primer using the Axisymmetric Drop Shape Analysis technique. Surface roughness (SR) was determined with a contact profilometer. In another four molars, CSEB was applied to the smear layer-covered dentin with both hydration states. Resin build-ups were performed incrementally with Tetric Ceram. After storage for 24 hours in water at 37 degrees C, the teeth were sectioned to obtain bonded beams with an average cross-sectional area of 1.0 mm2. Each beam was tested in tension in an Instron machine at 0.5 mm/minute. Kolmogorov-Smirnov and Student t-tests were performed at a 95% significance level. RESULTS: Observed water contact angles were lower on the hydrated smear layer but no differences were found between contact angles on completely and briefly air-dried smear layer when the primer was used for CA measurements. SR was similar for both substrates and MTBS was greater when the adhesive was applied on the completely air-dried smear layer.

Acid Etching, Dental↗
PubMed2006

Effect of smear layer and chlorhexidine treatment on the adhesion of Enterococcus faecalis to bovine dentin.

The aim of this in vitro study was to determine the effects of a smear layer and chlorhexidine (CHX) treatment on the adhesion of Enterococcus faecalis to bovine dentin. Forty dentin blocks from bovine incisors were prepared and randomly divided into four groups of 10 each. The blocks in group 1 were placed in sterile saline for 5 minutes, while those in group 2 were treated with 17% EDTA for 5 minutes. The blocks in group 3 were placed in 2% CHX for 7 days. The blocks in group 4 were treated with 17% EDTA for 5 minutes, and then placed in 2% CHX for 7 days. All the blocks were immersed in a suspension of E. faecalis for 3 hours. The bacteria adhering to the dentin surface were counted by examination using a scanning electron microscope. The most significant amount of bacteria was retained on the samples from group 1 (p < 0.05) and the smallest amount of bacteria adhered to the samples from group 4. These results suggest that a smear layer enhances the adherence of E. faecalis to the dentin, and CHX is effective in reducing the adherence of microorganisms.

Analysis of Variance↗
PubMed1995

The adaptation of mechanically softened gutta-percha to the canal walls in the presence or absence of smear layer: a scanning electron microscopic study.

The objective of this study was to compare the adaptation of mechanically softened gutta-percha to the root canal wall in the presence and absence of smear layer. The root canals of 20 freshly extracted human maxillary incisors were cleaned and shaped. Prior to obturation, 10 root canals were irrigated with 20 ml of 50% citric acid followed by 20 ml of 5.25% sodium hypochlorite. All canals were obturated with mechanical compaction of gutta-percha and AH-26 sealer. After 72 h, each tooth was fractured in half. Scanning electron microscopy demonstrated that the sealer had formed a continuous layer in contact with the canal walls, becoming progressively thinner towards the apex. The sealer penetrated into the dentinal tubules along with projections of gutta-percha only in those teeth without smear layer.

Bismuth↗
PubMed2003

Evaluation of canal cleanliness and smear layer removal after the use of the Quantec-E irrigation system and syringe: a comparative scanning electron microscope study.

OBJECTIVE: The purpose of this study was to evaluate canal cleanliness and smear layer removal after use of the Quantec-E irrigation system and to compare the system with traditional irrigation. STUDY DESIGN: Forty anterior teeth were randomly assigned to 4 groups. Group A consisted of 15 teeth that were instrumented with .12, .10, .08, .06 and .04 tapered rotaries while simultaneously irrigated via the Quantec-E irrigation pump with 12 mL of 5.25% NaOCl, followed by 6 mL EDTA 17% in crown-down fashion, with a final flush with 4 mL 5.25% NaOCl. Group B consisted of 15 teeth that were instrumented with the same instrument sequence, and irrigated with the same volumes via traditional needle and syringe. Group C consisted of 5 teeth that were sectioned and examined under a scanning electron microscope (SEM) without any instrumentation and served as a negative control. Group D consisted of 5 teeth that were instrumented dry, without any irrigation, and served as a positive control. All teeth were sectioned buccolingually and examined with SEM at 700x magnification in the apical, middle, and coronal portions of the canals. Analysis of SEM images was performed by 5 independent examiners using a 4-point scoring system. RESULTS: Irrigation with the Quantec-E irrigation pump resulted in cleaner canal walls, less debris, and more complete removal of the smear layer within the coronal one third, when compared with syringe irrigation. However, no difference was observed in the middle and apical one thirds of the root canal. CONCLUSION: There was no significant difference between the 2 irrigation systems.

Dental Pulp Cavity↗
PubMed1995

Sealability of the Trifecta technique in the presence or absence of a smear layer.

The aim of this in vitro study was to assess the sealability of a recently introduced thermoplasticized gutta-percha technique (Trifecta, Hygenic Corp., OH, USA) in the presence or absence of a smear layer. A total of 100 teeth with single straight root canals were included in the study. The teeth were decoronated and the canals prepared with a modified double-flared technique under constant irrigation with 2.5% sodium hypochlorite solution. The apical matrix was prepared to size 40 and apical patency subsequently confirmed with a size 10 file. Four teeth were discarded for technical reasons and the remaining 96 allocated randomly into two groups of 44 teeth and a group of eight teeth which acted as controls. Canals in group 1 were obturated randomly with either cold lateral condensation of gutta-percha or with the Trifecta technique. Canals in Group 2 were rinsed with 17% REDTA to remove the smear layer and then obturated with lateral condensation or the Trifecta technique. All teeth were suspended in India ink for 9 days, demineralized, and rendered transparent prior to the assessment of apical linear dye penetration. Apical extrusion of sealer and gutta-percha occurred commonly but there was no significant difference between the four obturation groups. However, overall, there was significantly more extrusion of sealer with the Trifecta technique compared with lateral condensation (P < 0.05). The majority of canals (79 out of 88) had no evidence of apical leakage and there was no significant difference between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Hydroxide↗
PubMed1992

Smear layer--materials surface.

SEM and TEM photomicrographs were presented of the smear layer and several dentin-adhesive interfaces. It was shown that as the wetting and penetration of the dentin adhesive increased, the shear bond strength also increased. Three categories of dentin adhesives were presented. Category one included Scotchbond, Dentin Adhesit and Gluma, with shear bond strength values between 5 and 7 MPa; the second category, dentin adhesives based on Dr. Bowen's research, included Tenure and Mirage Bond, with shear bond strengths between 8 and 14 MPa; the third category included Superbond and Scotchbond 2, with shear bond strength values up to 20 MPa. Failures occurred at the interface or in the resin adhesive for materials in categories one and two; failures occurred through the dentin or composite for materials in category three.

Adhesives↗
PubMedDate not supplied

The effect of airborne particle abrasion on the dentin smear layer and dentin: an in vitro investigation.

This study investigated the effect of airborne particle abrasion on the exposed dentin surfaces of 40 extracted teeth. A Siroflow abrasion unit was used to treat four groups of ten specimens that were subjected to 5, 10, 20, and 40 seconds of abrasion respectively. Statistical analysis (Spearman Rank Order) showed a significant difference between all groups (P < .05) but not within groups (P > .05). Scanning electron micrographs showed smear layer removal as an immediate effect of air polishing. Application times of longer than 5 seconds showed obstruction of dentinal tubule openings, possibly a result of abrasive powder residue. It was concluded that airborne particle abrasion removes the smear layer, and the amount of dentin removed corresponded to the time of application.

Air Pressure↗
PubMed1994

Effect of smear layer removal on the diffusion permeability of human roots.

Ten human maxillary incisors, extracted because of periodontal disease or nonrestorable caries, were obtained and instrumented to a size #70 K-Flex file at the working length using a standard stepback technique. Tritiated water (3H2O) was placed in the root canals and allowed to diffuse to the external surface of the roots until it reached a constant rate. The smear layer in each of the experimental roots was then removed using 0.5 M EDTA followed by 5.25% sodium hypochlorite (NaOCI). The constant rate diffusion of 3H2O was remeasured. The roots were then stored in deionized H2O for 2 months and the constant rate diffusion of 3H2O was remeasured. A statistically significant difference was noted between all three groups. A decrease in the diffusion permeability of the root to 3H2O was noted immediately after smear layer removal and the highest permeability was recorded after storage in the deionized water for 2 months.

Dentin↗
PubMed1993

Effect of smear layer removal on the diffusion of calcium hydroxide through radicular dentin.

Forty single-rooted teeth were sectioned transversely through the cementoenamel junction and instrumented to a size #50 K-Flex file at the working length by saline irrigation. Each root was placed in a dilution vial containing 10 ml of normal saline, and the pH and Ca2+ levels were recorded after 24 h. The roots in group 1 then received a final irrigation with 20 ml of normal saline. Group 2 received a final irrigation with 10 ml of 17% ethylenediaminetetraacetic acid followed by 10 ml of 5.25% NaOCl to remove the smear layer. Group 3 was irrigated in the same manner as group 2, but calcium hydroxide (CH) was placed into the root canal. Group 4 was irrigated with 20 ml of NaOCl, and CH was placed into the root canal. The pH and Ca2+ levels were recorded at 1, 3, 5, and 7 days. After 7 days a 3- x 3- x 1-mm external defect was created in the coronal one third of the root surface. The pH and Ca2+ levels were subsequently recorded at 1, 3, and 7 days. Groups 3 and 4 demonstrated significantly higher H+ and Ca2+ levels than did groups 1 and 2 three days after CH placement and at all subsequent intervals. Group 3 demonstrated significantly higher H+ and Ca2+ readings at some but not all intervals. The results demonstrated that CH diffuses from the root canal to the exterior surface of the root and that the removal of the smear layer may facilitate this diffusion.

Analysis of Variance↗
PubMed1989

Tannic acid for smear layer removal: pilot study with scanning electron microscope.

The effects of a 25% tannic acid solution applied to the surface of prepared dentin was compared with untreated prepared dentin surfaces. The following results were demonstrated by electron microscope observation: (1) cavity preparations created an amorphous dentinal smear layer, (2) placement of a 25% tannic acid solution for 15 seconds removed the smear layer, (3) the contents of the dentinal tubules were not removed and no enlargement of dentinal tubules was found, and (3) a clean dentinal surface was observed.

Dental Cavity Preparation↗
PubMed1991

[The dentinal smear layer. Characteristics and interactions. 2].

The Authors, after the presentation (in the first part of the Dossier) of a large literature review about the physical, chemical and clinical characteristics of formation, interaction, remotion of "smear layer" during cavity preparation in hard tooth tissue, describe the results of a scanning microelectronic research about the action as cleanser (for the dentinal cavity wall) of the CK101 (Caridex) versus wather, Tubulicid and phosphoric acid. The experimental results obtained "in vitro" show that the substance has relative action, without removing the tubular portion of "smear layer".

Acid Etching, Dental↗
PubMed2005

Effects of diode laser irradiation on smear layer removal from root canal walls and apical leakage after obturation.

OBJECTIVE: The objective of this study was to investigate the rise in temperature in root surfaces during and immediately after diode laser irradiation, to observe morphological changes of root canal wall after irradiation, and to evaluate the apical leakage after irradiation and obturation in vitro. BACKGROUND DATA: There have been very few reports on root canal treatment by 980-nm wavelength diode laser. METHODS: Sixty-six extracted human single-rooted teeth were instrumented up to size 60 K-file, and then randomly divided into three groups of 22 teeth each. Groups 1 and 2 were irradiated with a diode laser at 5 W for 7 sec using fibers of diameters 550 and 365 microm, respectively. Group 3 was not irradiated, and served as a control. The rise in temperature on root surfaces of the teeth in groups 1 and 2 were measured by thermography. Six teeth in each group were bisected longitudinally and observed morphologically. Other teeth were obturated and immersed in rhodamine B solution, and the degree of apical leakage was evaluated longitudinally and transversally. RESULTS: A maximum temperature rise of 8.1( degrees )C was recorded in group 1. The smear layer in the laser-treated groups was evaporated and removed, resulting in clean root canal walls, which was significantly superior to the control group (p < 0.05). After obturation, the laser-treated groups showed significantly less apical leakage than the control group (p < 0.05). CONCLUSIONS: These results indicate that the diode laser is useful for removing smear layer and debris from root canal walls, and reducing apical leakage after obturation in vitro, and suggest that it would be useful for root canal treatment in clinic.

Dental Leakage↗