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PubMed1995

Adhesion of composite to polished dentin retaining its smear layer.

OBJECTIVES: This study was designed to measure the adhesion of a composite to the smear layer. METHODS: An experimental aqueous bonding agent was supplied in the form of two liquids. One contained methacryloyl tyrosine amide (MTYA), glyceryl methacrylate (GM), dimethylaminoethylmethacrylate and benzene sulfinic acid sodium salt, and the other contained glutaraldehyde, succinic acid and 2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy)-N,N, N-trimethy-1-propanaminium chloride (QTX). QTX is a unique water-soluble photo polymerization initiator. The application times and irradiation times of the experimental aqueous bonding agent were varied. RESULTS: The highest mean bond tensile strength was obtained by irradiating the bonding agent for 1 min. A 3 min irradiation decreased the mean bond strength when the bonding agent was applied to the polished dentin surface for 1, 3 or 5 min. The mean values resulting from the application of experimental aqueous bonding agent were higher than those from a commercially available bonding agent which preserved or modified the smear layer. There was a significant decrease in the bond strength after 500 or 2000 thermocycles in specimens with a 5 min application of the bonding agent, but there was no significant decrease in the bond strength when the application time was for 1 or 3 min. SEM observation showed the formation of a hybrid layer with a thickness of approximately 1-1.5 micrometers. SIGNIFICANCE: The aqueous bonding agent tested in this investigation was capable of penetrating the smear layer and the bond strength exceeded the values obtained by bonding agents that remove the smear layer.

Analysis of Variance↗
PubMed2005

Tetracycline at subcytotoxic levels inhibits matrix metalloproteinase-2 and -9 but does not remove the smear layer.

BACKGROUND: The antibacterial and anticollagenolytic properties of tetracycline (TCN) are valuable in periodontal therapy, and TCN treatment can remove the smear layer following root instrumentation. However, recent reports pointing to cytotoxic effects of several acids prompted this study to define TCN concentrations that are anticollagenolytic and remove the smear layer, but have low cytotoxicity. METHODS: Human gingival (hGF) and periodontal ligament (hPDL) cells were treated short- (3 minutes) or long-term (24 hours) with TCN to determine concentrations yielding 50% (TD(50)) and 90% (TD(10)) cell survival. Activity assays measured TCN concentrations with half-maximal inhibition (IC(50)) of matrix metalloproteinase- 2 and -9 (MMP-2 and -9). Finally, we analyzed the effects of TCN with high (75 mg/ml) or low (1 mg/ml) cytotoxicity on the smear layer by scanning electron microscopy (SEM). RESULTS: The TD(50) for TCN after short-term treatment was 4 mg/ml for both hGF and hPDL. Ninety percent of the cells survived 0.2 mg/ml. With long-term treatment, the TD(50) for hGF and hPDL was 70 and 30 microg/ml, respectively, and the TD(10) was 20 and 5 microg/ml. HGF and hPDL recovered from the 3-minute treatment with 1 mg/ml, but not from concentrations exceeding 3 and 9 mg/ml, respectively. The IC(50) was 25 microg/ml for both MMP-2 and MMP-9. Whereas 75 mg/ml TCN removed the smear layer, 1 mg/ml TCN had no effects. CONCLUSIONS: Tetracycline has significant cytotoxicity on periodontal cells. Since non-cytotoxic concentrations of TCN inhibited MMP-2 and -9 but had no effects on the smear layer, TCN is not recommended for root surface treatment.

Anti-Bacterial Agents↗
PubMed1994

Mechanical removal of the smear layer.

The purpose of this study was to selectively remove the smear layer from dentine without altering the underlying tissue. Two groups of test samples were established. The first group consisted of flat dentine surfaces exposed transversely in the mid-coronal plane using a diamond blade. The second group was comprised of Class II cavity preparations made in recently extracted molar teeth using a diamond bur. The cut surfaces in both groups were subjected to the air polishing action of the Prophy Jet devise. Exposure times were 2, 5, 10, 20 and 40 s. An untreated control was established for each group. The specimens were examined by scanning electron microscopy. Findings showed the selective removal of the smear layer can occur in 5 s for surfaces perpendicular to the jet stream while axial walls of cavity preparations required 20 s. The method confirms previous findings and can be recommended to study the influence of the smear layer in dentine bonding.

Air↗
PubMed2002

A scanning electron microscopic study of debris and smear layer remaining following use of GT rotary instruments.

AIM: The aim of the present study was to assess debris and smear layer remaining following canal preparation with GT rotary instruments. METHODOLOGY: Sixteen freshly extracted single-rooted premolar teeth were instrumented with GT rotary instruments using a crown-down preparation technique. All specimens were flushed with 2 mL of 5% NaOCl between each rotary instrument. At the end of instrumentation the following final irrigation sequence was repeated two times: 2 mL of EDTA + Cetrimide for 1 min (Largal Ultra, Septodont, France) and 2 mL of 5% NaOCl for 5 min. A final flush with saline solution was made to halt any chemical activity. Two other uninstrumented teeth that were not irrigated served as controls. All teeth were split longitudinally and prepared for SEM evaluation. The presence of debris and smear layer was evaluated from photomicrographs at x200 and x1000 magnification taken in the apical, middle and coronal thirds of the canals. Blind evaluation was performed by two trained observers and scores were compiled separately. A five category scoring system for debris and smear layer was used. Values obtained were tabulated and statistical analysis was carried out using a parametric chi-squared test. RESULTS: Statistical analysis showed that there was no significant difference between the three regions of the root canals (P > 0.05) for debris. Comparison of the removal of the smear layer between the three regions showed that there was a statistically significant difference between all parts, especially between the coronal and apical thirds (P < 0.001). Overall, the coronal sections were cleaner than the middle and apical sections. The uninstrumented canals showed walls completely covered with tissue, confirming that specimen preparation alone did not remove tissue. CONCLUSIONS: Under the conditions of the present study GT rotary instruments removed debris effectively, but left root canal walls covered with smear layer, particularly in the apical third.

Bicuspid↗
PubMed2005

Smear layer production of K3 and ProFile Ni-Ti rotary instruments in curved root canals: a comparative SEM study.

OBJECTIVE: The aim of this scanning electron microscopic study was to compare the quality and amounts of smear layer generated by 2 brands of nickel-titanium rotary instruments during canal preparation in the apical thirds of curved root canals. STUDY DESIGN: Forty mandibular mesial root canals with intact apex and mean curvature between 30 and 35 degrees were selected for this study. The root canals were randomly divided into 2 instrumentation groups of 15 each. Automated preparation was performed with ProFile (Dentsply Maillefer, Ballaigues, Switzerland; n = 15) and K3 (SybronEndo, Orange, Calif; n = 15) instrumentss using a crown-down technique. As a control group, barbed broaches (Mani; Matsutani Seisakusho, Takanezawa-Machi Tochibi-Ken, Japan; n = 10) were used to extirpate the necrotic pulp tissue from the root canals. All root canals were prepared to size #35. Glyde (File Prep, Dentsply Maillefer) was used as lubricant and 1% sodium hypochlorite solution as irrigant. At the conclusion of the experiments, all roots were split longitudinally and the root canal walls were examined at the apical third from 2 different perspectives using a scanning electron microscope. A 4-category scoring system for assessing the smear layer accumulation was used, and the resulting scores were statistically analyzed. RESULTS: Less smear layer was obtained in the K3 group at the selected apical third of curved root canals (P < .05). However, all instruments left a smear layer. The surface texture of the smear layer, in addition to the depth and the frequency of packed materials into the dentinal tubules, varied with instrument type. CONCLUSIONS: This finding may imply that, compared to ProFile, compression of the remaining smear layer is minimized when using the K3 rotary nickel-titanium system.

Dental Alloys↗
PubMed1998

Comparative study about the removal of smear layer by three types of laser devices.

OBJECTIVE: The aim of this study was to analyze the effectiveness of three types of laser, argon, Nd:YAG, and Er:YAG, to remove the smear layer from the prepared root canal walls in vitro. METHODS: After cleaning and shaping by step-back preparation, 32 human extracted maxillary molar teeth were divided randomly into four groups. Root canals in group 1 (G1) were unlased and were irrigated by 17% EDTA. In group (G2), root canals were irradiated by argon laser at the parameters of 1 W, 50 mJ, and 5 Hz. In group 3 (G3) root canals received Nd:YAG laser irradiation at 2 W, 200 mJ and 20 Hz. Teeth in group 4 (G4) were irradiated by Er:YAG laser at the following parameters: 1 W, 100 mJ and 10 Hz. Then these teeth were bisected longitudinally, observed using SEM, and evaluated. RESULTS: The middle third of the teeth from G1 showed clean wall surfaces with open dentinal tubules. In G2, at the middle third, the smear layer was free and vaporized pulpal tissue remnants were observed. In G3, most of the specimens showed very clean walls with the smear layer evaporated, melted, fused, and recrystallized in both the middle and apical thirds. The walls of G4 revealed the evaporated smear layer and open dentinal tubules in the middle and apical thirds. Statistical analysis showed significant differences between G1 and G2, G1 and G3, and G1 and G4. CONCLUSIONS: These results show that the argon laser and Nd:YAG laser are useful to remove the smear layer and that the Er:YAG laser irradiation is the most effective to remove the smear layer on root canal walls.

Argon↗
PubMed1998

Influence of smear layer on depth of penetration of three endodontic sealers: an SEM study.

The purpose of this study was to examine the effect of the smear layer on the penetration depth of Sealapex, Roth 811, and CRCS root canal sealers into the dentinal tubules. Forty recently extracted, human single-rooted teeth were used. The crowns were cut and removed at the cemento-enamel junction level and the root canals were prepared to a #60 K-file. The teeth were then randomly divided into two groups of 20, group A and group B. The smear layer was removed from all teeth in group A with EDTA and NaOCl. The smear layer remained in all teeth in group B. Two roots in each group were used as controls. Six roots from each group were obturated with Roth 811 sealer and gutta-percha through lateral condensation. The same process was repeated using sealers CRCS and Sealapex. Each root was then divided in two and prepared for scanning electron microscope observation. The removal of the smear layer allowed penetration of all three sealers into the dentinal tubules to a depth of between 35 microns and 80 microns. Although the CRCS sealer penetrated only up to the 35 mm point, it offered better or complete obturation of the dentinal tubules. The presence of smear layer at the root canal walls obstructed the penetration of all sealers into the dentinal tubules.

Adult↗
PubMed1997

Effect of Nd:YAG laser irradiation for removal of intracanal debris and smear layer in extracted human teeth.

OBJECTIVE: The objective of this study was to evaluate the efficacy of Nd:YAG laser to remove debris and smear layer on the instrumented root canal walls in vitro. SUMMARY BACKGROUND DATA: There have been some contradictory reports about the efficacy of Nd:YAG laser to remove debris and smear layer. MATERIALS AND METHODS: Thirty-six extracted single mandibular incisor human teeth were used in this study. The teeth were sectioned at an enamel-cementum junction and the roots were instrumented up to # 50-K files size, then divided into three groups of 12 teeth. The first group (Group 1) was unlased as a control, and in the other two groups, root canals were irradiated by Nd:YAG laser at two different parameters; 1 W, 20 pps (Group 2) and 2 W, 20 pps (Group 3). After laser irradiation, the roots were bisected longitudinally, observed by scanning electron microscopy, and evaluated the condition of cleanliness on the root canal walls according to our criteria. RESULTS: In most of the specimens in Groups 1 and 2, debris and smear layer remained on the root canal wall surfaces covering the orifices of dentinal tubules. However, specimen in Group 3 showed very clean root canal walls with debris and smear layer evaporated, melted, fused, and recrystallized in most cases. Statistical analysis demonstrated a significant difference between Groups 1 and 3. CONCLUSIONS: These results suggest that Nd:YAG laser is useful to remove debris and smear layer and causes melting of internal structures on the instrumented root canal walls at the parameters of 2 W and 20 pps.

Dental Pulp Cavity↗
PubMed1998

Efficacy of Er:YAG laser irradiation in removing debris and smear layer on root canal walls.

The purpose of this study was to evaluate the efficacy of Er:YAG laser irradiation in removing debris and smear layer from prepared root canal walls. Thirty-six human extracted mandibular incisors teeth were divided into three groups. Group 1 (G1) was control specimens that were not lased. The teeth of group 2 (G2) and group 3 (G3) were irradiated by Er:YAG laser at different watt powers of 1 W and 2 W. The teeth were bisected and prepared for study in stereoscopic light microscope and SEM. Control specimens showed an amount of debris and heavy smear layer obscuring the dentinal tubules at all levels in the canals. The root canal walls irradiated by Er:YAG laser were free of debris, with an evaporated smear layer and open dentinal tubules. Statistical analyses showed significant differences (p < 0.01) in cleanliness smear layer between G1 and G2, and G1 and G3. However, there was no statistically significant difference between G2 and G3 in the cleanliness of the middle and apical one-third of the root canals. These results show Er:YAG laser is effective in removing debris and smear layer from root canal walls.

Dental Pulp Cavity↗
PubMed2000

Smear layer influence on the apical seal of four different obturation techniques.

The purpose of this study was the in vitro evaluation of four techniques for the obturation of the root canal system in the presence or absence of a smear layer. Ninety-six human upper central incisors were instrumented using the pressureless crown-down technique and irrigated with 5.25% NaOCl. The teeth that had the smear layer removed were irrigated with this solution in combination with 17% EDTA. The teeth were obturated with lateral condensation with an accessory or standardized cone as the main cone, with vertical condensation of warm gutta-percha or with thermoplasticized injectable gutta-percha. Apical leakage was assessed by measuring the linear penetration of methylene blue dye with a stereomicroscope. The results showed no significant differences in the degree of leakage with and without the smear layer when the samples were considered as a whole. However, when the groups were assessed separately, teeth in the lateral condensation with an accessory main cone group and teeth in the thermoplasticized group leaked less with a smear layer present. In contrast teeth with lateral condensation and a standardized main cone leaked more with a smear layer present. In the vertical condensation groups there was no difference attributable to the smear layer.

Chelating Agents↗
PubMed2004

In vitro analysis of 'smear layer' on human dentine using ac-impedance spectroscopy.

OBJECTIVE: To analyse smear layers on human dentine using ac-impedance spectroscopy. METHODS: Dentine samples were prepared from extracted, sound, third molars. Impedance measurements were carried out on dentine samples before and after etching. After measuring, samples were examined under scanning electron microscope (SEM) to correlate electrical measurements with structure. RESULTS: Marked differences in impedance before and after etching were demonstrated. SEM investigation showed that a smear layer overlies dentine surfaces before etching, but completely disappeared after etching, leaving open dentinal tubules. CONCLUSIONS: The clinical removal of smear layers is still subjective. This objective method, based on combined ac-impedance and admittance measurement in vitro, has the potential to allow development of standardised techniques and if developed further may be of use in vivo.

Acid Etching, Dental↗
PubMed2000

Effects of pulsed Nd:YAG laser irradiation on smear layer at the apical stop and apical leakage after obturation.

AIM: This study evaluated the removal of smear layer at the apical stop by pulsed Nd:YAG laser irradiation with or without black ink, and the degree of apical leakage after obturation in vitro. METHODOLOGY: Sixty extracted human single-rooted teeth were used in this study. The teeth were instrumented up to a size 40 K-file, and then divided into three groups of 20 teeth each: group 1 was unlased as a control group; group 2 was treated with a laser; group 3 was treated with a laser and black ink. The laser was operated at 2 W and 20 pp for 2 s, and irradiation was performed twice with a 30-s interval. In each group, 10 teeth for the leakage study were obturated and immersed in rhodamine B solution for 48 h at 37 degrees C, and the others were used for evaluation of remaining smear layer. All teeth were bisected longitudinally and observed by stereoscopy or scanning electron microscopy. RESULTS: The smear layer in the laser-treated groups almost melted or evaporated, and was removed significantly compared with the control group (P < 0.05). Leakage was observed in 60% of samples in group 1 and in 20% of samples in group 2. No leakage was observed in group 3, which was significantly different from the control (P < 0.05). CONCLUSIONS: These results suggest that pulsed Nd:YAG laser irradiation with black ink increases the removal of smear layer compared with that without black ink, and reduces apical leakage after obturation significantly.

Carbon↗
PubMed2005

Effect of smear layer thickness and pH of self-etching adhesive systems on the bond strength and gap formation to dentin.

PURPOSE: To measure the buffering capacity of self-etching adhesive systems and to evaluate the effect of smear layer thickness on the mean gap width (GW) and microtensile bond strength (microBS) to dentin of these self-etching adhesives. MATERIALS AND METHODS: Clearfil SE Bond (SE), Optibond Solo Plus Self-Etch Primer + Optibond Solo Plus (SO), Tyrian Self Priming Etchant + One Step Plus (TY) and as controls, Single Bond (SB) and ScotchBond Multi-Purpose Plus (SC) were used with Filtek Z250 Universal Restorative. The self-etching primers and 35% phosphoric acid (0.5 ml) were titrated by adding successive 0.05 ml drops of NaOH (1N). Thirty molars (n = 5) were sectioned in halves upon which thick (60-grit SiC) and thin (600-grit SiC) smear layer surfaces were produced. The adhesive application was randomized (n = 6) and a resin buildup was made. After 24 h, the resin-dentin sticks (0.8 mm2) were prepared. The GW on the sticks was measured at 400X magnification before the microtensile test (0.5 mm/min). The microtensile bond strength index was calculated including the relative failure type contribution. Data were analyzed by a two-way ANOVA and Tukey's multiple comparison. Simple linear regression was performed to determine whether correlation existed between microBS and pH, GW and pH, and microBS and GW. RESULTS: Only the factor "adhesive" significantly effected microBS (p = 0.001). TY had the lowest microBS values. Regarding GW, both main factors adhesive (p = 0.0001) and smear layer thickness (p = 0.03) were significant. The highest mean gap width was observed for SE and under a thick smear layer. A linear relationship was observed between the pH and GW and pH and microBS; however, a significant positive correlation was detected only between pH and GW (R = 0.99, p = 0.02). No relationship between microBS and GW was found (R = 0.04, p = 0.77). CONCLUSION: Although the smear layer thickness had no effect on resin-dentin bond strength, thick smear layers adversely affected the mean gap width. The microBS values were not affected by the acidity of self-etching primers; however, more aggressive self-etching primers showed the lowest mean gap width. The etch-and-rinse adhesive systems showed higher microBS and lower mean gap widths.

Acid Etching, Dental↗
PubMed2001

Philosophies and practices regarding the management of the endodontic smear layer: results from two surveys.

The purpose of this investigation was to ascertain the prevailing attitudes within the endodontic community regarding smear layer removal. The first survey asked the philosophies and techniques currently being taught to predoctoral dental students and postdoctoral endodontic residents in the United States, whereas the second surveyed some of the members of the American Association of Endodontists currently practicing in the United States. Findings from these surveys revealed that more than three-fourths of the dental students and nearly two-thirds of the endodontic residents are not being taught routine smear layer removal. Slightly more than one-half of endodontists responded they practice smear layer removal. These surveys indicate that there is no clear consensus in the endodontic community, either academically or clinically, as to whether the smear layer should be removed or be allowed to remain before obturation of the root canal space.

Data Collection↗
PubMed2005

The effect of application time of EDTA and NaOCl on intracanal smear layer removal: an SEM analysis.

AIM: To verify, under the scanning electron microscope (SEM), the influence of irrigation time with ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) on intracanal smear layer removal. METHODOLOGY: Twenty-one extracted human permanent teeth with single straight root canals were included. The root canals of the teeth were instrumented and, at the end of preparation, were irrigated with 3 mL of 15% EDTA, followed by 3 mL of 1% NaOCl for 1 min (group 1), for 3 min (group 2), and for 5 min (group 3). The canals of teeth in group 4 (control) did not receive the final irrigation. The teeth were sectioned longitudinally and prepared for an SEM. The dentinal wall of cervical, middle and apical thirds was graded according to the amount of debris and smear layer remaining on the walls. The results were analysed using the Kruskal-Wallis and Conover-Inman tests. RESULTS: In all the canals of experimental groups irrigation with EDTA and NaOCl completely removed the smear layer from the cervical and middle thirds. In the apical third, the dentine surface were partially covered, particularly in the teeth of group 1, where there was significantly more smear layer when compared with the other thirds in the same group (P<0.007). However, the Kruskal-Wallis test showed overall that there were no significant differences between groups 1, 2 and 3 (P>0.05). CONCLUSION: In this limited laboratory study, canal irrigation with EDTA and NaOCl for 1, 3 and 5 min were equally effective in removing the smear layer from the canal walls of straight roots.

Chelating Agents↗
PubMed2001

Bonding to dentin with a self-etching primer: the effect of smear layers.

OBJECTIVE: The purpose of this study was to investigate the effect of smear layers on the tensile bond strength to human dentin. Bond strength was determined on dumbbell-shaped specimens to determine the feasibility for clinical use of a self-etching primer. METHODS: The dentin of extracted human teeth was exposed by grinding with either #180 or #600 abrasive paper. A self-etching primer was then applied to the prepared dentinal surfaces and left undisturbed for 30s. It was then air-dried and a photocured bonding agent applied and irradiated for 20s. A composite resin was then added to the primed dentin and light-cured for 60s to complete the bonded assemblies. Mini-dumbbell specimens (3.0 x 2.0 mm2) were prepared from the bonded samples. These specimens were stored in 37 degrees C water for 24h before tensile loading to failure at a crosshead speed of 1.0 mm/min. Surfaces of fractured specimens, both resin and dentin, were examined under a scanning electron microscope (SEM). RESULTS: Significantly different tensile bond strengths (TBS) of 10.0+/-7.2 and 28.5+/-5.2MPa were found for #180- and #600-prepared dentin, respectively (p<0.01). The former specimens fractured within the hybridized, relatively coarse smear layer, while the latter demonstrated adhesive failure between the composite resin and an attached PMMA rod, not between the dentin and applied adhesive agent. SIGNIFICANCE: The presence and quality of a smear layer yields significantly different bond strengths to prepared human dentin, in vitro. However, a TBS of 10+/-7MPa is evidently adequate, since self-etching primers have been well accepted in dental clinics.

Acid Etching, Dental↗
PubMed1989

[Smear layer on prepared dentin].

Whenever dental tissues cut with a rotary instrument, a layer of grinding debris and organic film left of their surfaces, which is described by the term "smear layer". In this paper, we present the morphology and views for the formation of the smear layer. Additionally, we examine the influence of smear layer, on dentin permeability, infection by bacteria beneath dental restorations and on bonding capacity of adhesive dental materials. Following, detailed description of cleaning and chemical agents, used for smear layer removal from prepared dentin surfaces.

Dental Bonding↗
PubMed1996

[Effects of smeared layer on luting strength of dental cements].

Effects of smeared layer on the bond strength between dentin and dental cements were evaluated. Four surface conditions (No treatment, K-etchant, Dentin conditioner and EDTA) were prepared on the ground dentin of bovine frontal teeth. A copper tube was fixed and filled with a dental cement (zinc-phosphate cement or glass-polyalkenoate cement). A hook was embedded in the tube, with or without 1 MPa load during cementation. The bond strength was measured by a tensile test using a universal testing machine. No treatment had the largest bond strength of zinc-phosphate cement with or without load. No treatment, Dentin conditioner and EDTA had large bond strengths of glass-polyalkenoate cement with or without load; the bond strength of K-etchant was small without load and comparable to those of other surface conditions when load was applied. These results suggested that the bond strength of three surface conditions was not stronger than that of no treatment. Therefore, the elimination of smeared layer was concluded to have no advantage for increasing the bond strength between dentin and dental cements.

Animals↗