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PubMedDate not supplied

Effect of conditioner on bond strength of glass-ionomer adhesive to dentin/enamel with and without smear layer interposition.

The effect of a polyalkenoic acid conditioner pretreatment on the bond strength of a glass-ionomer adhesive to tooth substrates with or without smear layer was evaluated. Smear-layer covered and smear-layer free dentin and enamel surfaces were prepared from 24 extracted human molars. Resin composite was bonded to the surfaces using FujiBond LC with or without a polyalkenoic acid conditioner and subjected to microtensile bond strength (microTBS) testing. Failure modes were determined using scanning electron microscopy. For dentin, smear-layer coverage and conditioner treatment did not reveal significant differences in microTBS, which ranged from 20 to 29 MPa. For enamel, smear-layer coverage did not significantly affect microTBS, whereas, the use of conditioner significantly improved microTBS, reaching the same microTBS-values as when bonded to dentin. Regarding failure mode, most dentin specimens failed mixed adhesive cohesively. For enamel, adhesive failures mostly occurred when no conditioner was used, though mixed failures were predominant when the specimens were conditioned beforehand. Bonding of the glass ionomer adhesive to dentin can be achieved without the separate use of a polyalkenoic acid conditioner, even with the interposition of a smear layer. However, instrumented and non-instrumented enamel requires separate conditioning to provide sufficient micro-mechanical retention.

Acrylic Resins↗
PubMed2001

Effect of removal of the smear layer on apical microleakage.

It has been shown previously that the smear layer created during instrumentation of the root canal promotes apical microleakage. The purpose of the present study was to investigate the effect of removal of the smear layer on apical microleakage, using the fluid filtration method. Thirty-six single-rooted human premolar teeth were used. Six of the teeth were selected randomly as controls, and the remaining 30 teeth were randomly divided into two groups of 15 teeth each. For the first group (group 1) teeth were irrigated with NaOCl only (smear layer not removed). In the second group (group 2) the teeth were irrigated with 15% EDTA, followed by NaOCl to remove the smear layer. Both groups were filled with thermoplasticized gutta-percha (Obtura II) using glass-ionomer cement as sealer. All teeth were stored at 37 degrees C and 100% humidity for 2 days. Apical microleakage of the filled root canal was measured by the fluid filtration technique. Hydraulic conductance was measured by the movement of an air bubble in a capillary tube after a pressure of 200 mm Hg was applied to the system. The mean microleakage rate of group 1 and group 2 were 13.0 (SD +/- 5.1) and 16.9 (SD +/- 15.3) nl/s, respectively. Removal of the smear layer caused significantly more apical microleakage (p < 0.05, Student's t test) than when the smear layer was left intact.

Bicuspid↗
PubMed2001

Molecular structure of acid-etched dentin smear layers--in situ study.

It is commonly reported that acid etchants remove the smear layer, but to date, there has been no chemical evidence to support these observations. The purpose of this study was to determine the molecular structure of acid-etched carbide- and diamond-bur-created smear layers. This project tested the null hypothesis that such smear layers are totally removed with current etchants. Smear layer/demineralized/mineralized dentin interfaces were analyzed at 1- m intervals by micro-Raman spectroscopy. Features associated with the organic component were substantially broadened with loss of fine structure, and mineral peaks were clearly evident in the spectra of acid-etched smear layers. The organic features in the spectra of the EDTA-treated smear layer showed relative intensity ratios similar to demineralized dentin without contribution from the mineral phase. The disorganized collagen within the smear layer was not removed but was denatured by the acid treatment; the mineral was trapped in this gelatinous matrix and shielded from complete reaction.

Acid Etching, Dental↗
PubMed1996

The effect of smear layer on microbial coronal leakage of gutta-percha root fillings.

The aim of this in vitro study was to determine the effect of removal of the smear layer on canal obturation as measured by penetration of bacteria from a coronal direction. One hundred and twenty extracted human teeth with straight, single root canals were decoronated. The canals were prepared using the modified double-flared technique with balanced force under copious irrigation. The apical matrix was prepared to size 40 and apical patency subsequently confirmed with a size 15 file. The teeth were divided randomly into experimental groups (80 teeth) and control groups (40 teeth). The root canals of 40 experimental and 20 control teeth were rinsed with 40% citric acid and 2% NaOCl to remove the smear layer before obturation. In experimental groups, 20 teeth with smear layer intact and 20 teeth with smear layer removed were obturated with lateral condensation of cold gutta-percha and Apexit sealer. A further 20 teeth with smear layer intact and 20 teeth with smear layer removed were obturated with the Trifecta technique with the same sealer. In control groups, 10 teeth with smear layer intact and 10 teeth with smear layer removed were obturated with lateral condensation of cold gutta-percha and Apexit sealer. These teeth were completely sealed both coronally and apically to serve as negative controls. The remaining 20 teeth with either smear layer intact or smear layer removed were not obturated and served as the positive controls. The root surface of each tooth was sealed with nail varnish. The cut end of a polypropylene tube was sealed around the coronal part of each root canal so that bacteria placed therein could move only through the obturated canal space. Each root was placed in a glass bottle containing sterile Todd-Hewitt Broth (THB) and aliquots of 0.5 ml of THB were injected into the polypropylene tube. The model system was centrifuged at 168 g. An innoculum of Streptococcus sanguis in THB was placed in each coronal chamber at 5-day intervals and daily observations were made for bacterial growth in the apical reservoir for 90 days. All positive control teeth showed bacterial penetration within 24 h, while the negative control teeth remained uncontaminated throughout the test period. Leakage through the experimental teeth was variable ranging from 7 to 86 days. There was no statistical significant difference (P > 0.05) in leakage between the obturated canal when the smear layer was either removed or intact.

Calcium Hydroxide↗
PubMed1994

The effect of smear layer removal on marginal contraction gaps.

The presence of the smear layer prevents direct contact between dentine and a dentine adhesive. The use of agents to remove the smear layer theoretically should improve the bonding of composite resins to dentine. This study examined the effect of smear layer removal on the effectiveness of a dentine bonding agent in reducing marginal contraction gaps. The agent used for smear layer removal in this study was ethylenediamine tetra-acetic acid (EDTA). Eighty cavities measuring 2 mm in diameter and 1.5 mm in depth were prepared in dentine and randomly assigned to two equal groups. The control group was restored with Prisma Universal Bond 2 Adhesive and Prisma Fil Resin. The experimental group was similarly restored after pretreatment of dentine with 0.5% EDTA for 60 s. All specimens were thermocycled and the marginal contraction gaps were assessed using a Nikon Measurescope. The mean contraction gap was expressed as a percentage of the cavity diameter. Results showed that the experimental group registered smaller contraction gaps (mean: 0.021%) than the control group (mean: 0.027%). No penetration of material into dentine was observed. Pretreatment with EDTA did not significantly improve the effectiveness of the dentine bonding agent used in terms of reduction of marginal contraction gaps.

Acid Etching, Dental↗
PubMed1997

Coronal leakage: effects of smear layer, obturation technique, and sealer.

Coronal microleakage may be a major factor in the etiology of treatment failure. This study examined the effect of obturation technique, sealer, and the presence of smear layer on coronal microleakage. Two hundred extracted human teeth were assigned to 20 treatment groups. Groups were examined with the smear layer present or smear layer removed (17% REDTA). Access cavities were exposed to artificial saliva then Pelikan Ink. Teeth were cleared and linear dye penetration measured. When all groups with the smear layer removed were compared with all groups with the smear layer present, significantly less leakage was seen when the smear layer was removed. Ultrafil displayed significantly more leakage than all other groups. Vertical compaction of lateral condensation and Thermafil obturations significantly reduced leakage. AH-26 displayed significantly less leakage than Roth's 811 sealer. These results indicate that removal of the smear layer, the use of AH-26, and vertical compactin have cumulative effects in reducing coronal leakage.

Analysis of Variance↗
PubMed1990

Dye penetration of the smear layer and fluoride application to the dentin surface.

A smear layer is formed after cavity or root canal preparation. The aim of the present study was to reinforce the dental surface in order to prevent the invasion of foreign irritants, by treating the smear layer with fluoride. Dentinal samples whose surfaces had been washed with water after the formation of a smear layer, and corresponding samples without washing, were examined by the dye penetration test, and the results were compared. Although there was no significant difference between the two groups of samples, dye penetration was suppressed by about 30% in washed samples, whereas the suppression was 20% in unwashed samples. When washed samples were treated with 1.0% SnF2, 10.0% SnF2, 7.5% Na2PO2F, 15% Na2PO2F, APF, 10 mM In(NO3)3, 100 mM TiF3, 50 mM TiF3, or 10 mM TiF3, samples washed after treatment with 1.0% SnF2 showed a dye penetration suppression of about 60% as a whole, in comparison with samples having no smear layer. Hardly any suppression of dye penetration was observed after treatment with other fluorides.

Acid Etching, Dental↗
PubMed2003

The effect of various concentrations of sodium hypochlorite on the ability of MTAD to remove the smear layer.

Various organic acids, ultrasonic instruments, and lasers have been used to remove the smear layer from the surface of instrumented root canals. The purpose of this study was to investigate the effect of various concentrations of sodium hypochlorite (NaOCl) as an intracanal irrigant before the use of MTAD (a mixture of a tetracycline isomer, an acid, and a detergent) as a final rise to remove the smear layer. Ten operators, using a combination of passive step-back and rotary 0.04 taper, nickel-titanium files, prepared 80 single- and multirooted human teeth. Distilled water, four different concentrations of NaOCl, or MTAD was used as intracanal irrigant. The canals were then treated for 2 min with 5 ml of one of the following solutions as a final rinse: 5.25% NaOCl, sterile distilled water, 17% EDTA, or MTAD. The presence or absence of smear layer and the amount of erosion on the surface of the root canal walls at the coronal, middle, and apical portion of each canal were examined under a scanning electron microscope. The results show that although MTAD removes most of the smear layer when used as an intracanal irrigant, some remnants of the organic component of the smear layer remain scattered on the surface of the root canal walls. The effectiveness of MTAD to completely remove the smear layer is enhanced when low concentrations of NaOCl are used as an intracanal irrigant before the use of MTAD as a final rinse. This regimen does not seem to significantly change the structure of the dentinal tubules.

Anti-Bacterial Agents↗
PubMed1989

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.

Composite Resins↗
PubMed1998

A scanning electron microscopic study of the effect of Gluma CPS bonding system on dentinal smear layers produced by different bur types and rotational speeds and on the resin-dentin interface.

OBJECTIVE: The purpose of this study was to investigate the effect of conditioners on smear layers produced by different bur types and rotational speeds and to study the interaction of subsequently applied primer and sealer with these conditioned surfaces. METHOD AND MATERIALS: Smear layers were produced on human teeth immediately after extraction by burs rotating at approximately 6,000 rpm without water spray and 400,000 rpm with water spray. Gluma CPS etchant was applied for 15, 30, and 60 seconds, and a 20% phosphoric acid liquid (control) was applied for 30 seconds to smear layers. The specimens were prepared by critical point drying for scanning electron microscopic imaging within 24 hours. Additional specimens were prepared and treated with Gluma CPS primer and sealer, according to the manufacturer's instructions. RESULTS: There were only small variations in the smear layer thicknesses with different bur types or speeds of rotation. Gluma CPS conditioner, applied for the recommended times, did not completely remove the smear layer. An altered smear layer, composed of a reaction product, remained on the dentinal surface. A zone of demineralization did occur, however, beneath the partially removed smear layer in both the 15- and 30-second specimens but was only partly filled by primer and sealer. Smear layers were completely removed by the 20% phosphoric acid liquid to expose a delicate collagen network. CONCLUSION: An understanding of the appropriate treatment for smear layers is crucial to the development of improved dentin bonding systems.

Acid Etching, Dental↗
PubMed2001

Comparison of the cytotoxic effects and smear layer removing capacity of oxidative potential water, NaOCl and EDTA.

UNLABELLED: This study compared the smear layer removing capability and cytotoxicity of NaOCl, EDTA and Oxidative Potential Water (OPW). Fifteen extracted single-rooted human upper incisors were examined in three groups. The root canals were enlarged to the apical foramen with K files to size #60 and irrigated with: (a) NaOCl followed by OPW, (b) OPW during and after instrumentation and (c) NaOCl followed by EDTA and NaOCl. The effect of these irrigants on the smear layer was evaluated using a scanning electron microscope. In vitro cytotoxicity of these irrigants was examined by MTT colorimetric assay. We found that the combination of NaOCl and OPW as well as the application of OPW alone, failed to remove the smear layer from the apical third, whereas the EDTA and NaOCl combination achieved complete removal. OPW, when used during and after instrumentation, removed the smear layer in the middle third more effectively than NaOCl followed by OPW. EDTA exerted more cytotoxic effects at all concentrations tested when compared with OPW and NaOCl. IN CONCLUSION: (a) OPW was less cytotoxic than other irrigants but did not effectively remove the smear layer, (b) treatment with EDTA followed by NaOCl efficiently removed of the smear layer, but their cytotoxicity should be considered during endodontic therapy.

Animals↗
PubMed1999

Long-term evaluation of the influence of smear layer removal on the sealing ability of different sealers.

The purpose of this study was to examine the effect of the smear layer on apical microleakage over 16 wk. One hundred and four extracted human teeth were assigned to four groups treated as follows: group A1--smear layer was left intact and canals were obturated with gutta-percha and Roth 811; group A2--smear layer was left intact and canals were obturated with gutta-percha and AH26; group B1--smear layer was removed and canals were obturated with gutta-percha and Roth 811; and group B2--smear layer was removed and canals were obturated with gutta-percha and AH26. Microleakage was measured by the electrochemical method. In parallel, 12 teeth were examined under a scanning electron microscope. The results indicated that the smear layer removal resulted in a statistically significant reduction of microleakage values in groups obturated with AH26. The presence or absence of smear layer had no significant effect on the sealing ability of Roth 811.

Bismuth↗
PubMed1990

[Effect of smear layer removal on bevelled and retrofilled teeth in vitro].

The "smear layer" is composed of debris that cover and insert into dentinal tubules. It is not really known if this form of debris may harbon viable bacterias or does form a barrier that enhances endodontic fillings by lining or plugging the tubules. The purpose of this study is to determine the role of the smear layer in leakage by using two groups of teeth in which the smear layer was removed of the root canals, in the first group and left into the roots in the second group. Some samples were beveled and all teeth were retrofilled after Root Canal Preparation, and then filled with India Ink. After examination of leakage under various conditions, it has been found a correlation between leakage and removal of smear layer.

Dental Cavity Preparation↗
PubMed1989

[Formation, composition, clinical implications and methods for removing the smeared layer from root canal walls].

A layer, which is readily detectable at higher magnifications with scanning electron microscope (sem) is consistently seen on canal walls that have been endodontically instrumented. This layer in the international bibliography reported as smeared layer. The surface of this layer is amorphous, irregular and granular. Although the composition of this layer has not been completely determined, it probably contains fine inorganic particles of dentin produced by mechanical preparation of root canal walls. As well as some organic material from necrotic or vital pulp tissue, bacteria and blood cells. The clinical importance of the smeared layer is still not fully understood. It may be beneficial since it is known to plug the orifices of the dentinal tubules and to reduce the permeability of dentin. In addition, the Smeared layer covering prepared areas of root canal prevents medicaments and filling materials from penetrating the dentinal tubules on even contacting the canal wall. The formation of this layer, the composition, the clinical importance and various methods for removing the smeared layer from the system of root canals, is the object of this paper.

Dental Cavity Preparation↗
PubMed2002

Effects of rotary instruments and ultrasonic irrigation on debris and smear layer scores: a scanning electron microscopic study.

AIM: This study evaluated debris and smear layer scores after two types of instruments manufactured from different alloys were used to ultrasonically activate irrigants during canal preparation. The influence of two rotary preparation techniques on cleanliness of the shaped canals was also studied. METHODOLOGY: Apical stops were prepared to size 45 in 42 single-canalled extracted premolars and canines, which were divided into six equal groups. Groups 1, 2 and 3 were prepared by ProFile.04 (PF) while groups 4, 5 and 6 were prepared by Lightspeed (LS). All groups were irrigated using 5.25% NaOCl and 17% EDTA. Irrigants in groups 2 and 5 were ultrasonically activated using a size 15 steel K-file and by a blunt flexible nickel-titanium wire in groups 3 and 6. Groups 1 and 4 served as negative controls. Roots were split and canal walls examined at 15x, 200x and 400x magnification in an SEM. Smear layer and debris scores were recorded at 3, 6 and 9 mm levels using a 5-step scoring scale and a 200- micro m grid. Means were tested for significance using nonparametric Mann-Whitney U and Kruskal-Wallis tests. RESULTS: Debris and smear layer scores for the six groups varied from 1.98 +/- 1.04 to 3.47 +/- 0.97 and from 1.37 +/- 0.4 to 2.36 +/- 0.99, respectively. Although all groups had significantly higher smear layer and debris scores at the 3 mm levels compared to the 9 mm levels (P < 0.05), no significant differences were recorded due to the ultrasonic energy transmitted by the two alloys. CONCLUSION: Ultrasonically activated irrigants did not reduce debris or smear layer scores. This finding was not influenced by the material nor by the design of the instrument used to transmit ultrasonic activation.

Dental Instruments↗
PubMed1992

The effect of smear layer upon the coronal leakage of gutta-percha fillings and a glass ionomer sealer.

The effect of the removal of the smear layer on coronal leakage of root fillings was studied using two sealer cements. Sixty single-rooted teeth with mature apices were prepared chemomechanically using a modified double-flared technique with non-cutting tipped files and copious irrigation with 2% sodium hypochlorite. The teeth were randomly allocated to four groups of 15 teeth each. Two groups were treated with 40% citric acid to remove the smear layer. Two groups of teeth, one with and one without smear layer, were filled by lateral condensation of gutta-percha with either Tubliseal or a resin-based glass ionomer, Vitrebond. The teeth were stored for 1 week, thermocycled, and the extent of coronal leakage determined for each group after immersion in Indian ink for 90 h. The teeth were demineralized, dehydrated and immersed in methyl salicylate which rendered them transparent. Linear measurement of dye penetration was recorded. The mean depth (+/- SD) of leakage for the groups in which the smear layer was left intact was 4.26 +/- 1.53 mm and 6.83 +/- 1.65 mm for the Vitrebond and Tubliseal, respectively. When the smear layer had been removed, the mean depth of leakage for the Vitrebond group was 1.13 +/- 0.29 mm, and 3.72 +/- 1.23 mm for the Tubliseal group. There was a statistically significant difference in leakage between the groups (P < 0.001). With both sealers, those teeth in which the smear layer had been removed showed less leakage than the specimens in which the smear layer was left intact (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Citrates↗
PubMed2004

The influence of the smear layer on dentinal tubule penetration depth by three different root canal sealers: an in vitro study.

The effect of the smear layer on the penetration depth of three different root canal sealers into the dentinal tubules was examined in 64 recently extracted single-rooted teeth. After chemomechanical preparation, the samples were randomly divided in two equal groups. The smear layer remained intact in group A, whereas complete removal of the smear layer was performed in group B. Two roots from each group were used as controls. Ten roots from each group were obturated with laterally condensed gutta-percha points and sealers AH Plus, Apexit, and Roth 811, respectively. Examination in scanning electron microscope revealed that the smear layer obstructed all the sealers from penetrating dentinal tubules. In contrast, smear layer removal allowed the penetration of all sealers to occur to a varying depth. These findings suggest that smear layer plays an important role in sealer penetration into the dentinal tubules, as well as in the potential clinical implications.

Analysis of Variance↗
PubMed1994

An apical leakage study in the presence and absence of the smear layer.

The apical seal produced by low-temperature injection of gutta-percha, with or without root canal sealer, in the presence or absence of the smear layer was evaluated quantitatively using an electrochemical technique. The root canals of 44 teeth were prepared with the smear layer intact following a final flush of NaOCl (group 1), while the root canals of a further 44 teeth were prepared and the smear layer removed with a final flush with EDTA followed by NaOCl (group 2). Subgroups were obturated using Ultrafil System alone or accompanied by Calciobiotic Root Canal Sealer. Microleakage data was expressed as a percentage of apical leakage evident in each group. Statistical analysis of the results revealed that the groups obturated with Ultrafil alone showed no significant differences in leakage compared with the groups where sealer was used, either when the smear layer had been left intact or removed. (P > 0.05). However, comparison of the combined two groups with smear layer present versus the combined two groups with smear layer removed showed a highly significant difference (P < 0.01), with the incidence of leakage reduced in the absence of the smear layer.

Chi-Square Distribution↗