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At least 307 records · Page 17Linked to original sources
PubMed2004

Surface debris of canal walls after post space preparation in endodontically treated teeth: a scanning electron microscopic study.

PURPOSE: To evaluate surface cleanliness of root canal walls along post space after endodontic treatment using 2 different irrigant regimens, obturation techniques, and post space preparation for adhesive bonding. STUDY DESIGN: Forty teeth, divided into 4 groups, were instrumented, using Ni-Ti rotary files, irrigated with NaOCl or NaOCl+EDTA and obturated with cold lateral condensation (CLC) or warm vertical condensation (WVC) of gutta-percha. After post space preparation, etching, and washing procedure, canal walls were observed using a scanning electron microscope (SEM). Amount of debris, smear layer, sealer/gutta-percha remnants, and visibility of open tubules were rated. RESULTS: Higher amounts of rough debris, large sealer/gutta-percha remnants, thick smear layer, and no visibility of tubule orifices were recorded in all the groups at apical level of post space. At middle and coronal levels areas of clean dentin, alternating with areas covered by thin smear layer, smaller debris, gutta-percha remnants, and orifices of tubules partially or totally occluded by plugs were frequently observed. CONCLUSIONS: After endodontic treatment, obturation, and post space preparation SEM analysis of canal walls along post space shows large areas (covered by smear layer, debris, and sealer/gutta-percha remnants) not available for adhesive bonding and resin cementation of fiber posts.

Acid Etching, Dental↗
PubMed1998

Moisture-dependent renaturation of collagen in phosphoric acid etched human dentin.

We used atomic force microscopy (AFM) to investigate the effects of acidic and aqueous treatments on human dentin. Two basic points were determined: the first is the ability of AFM to discriminate the effect of phosphoric acid (pH approximately equal to 1) on polished dentin, and the second is the demonstrable effect of moisture on fibrous collagen structure. AFM images confirmed that the polishing process led to the removal of both smear layer and smear plugs. Our AFM study of undried dentin, which was then acid treated and kept moist, revealed substantial morphological changes at the dentin surface. Collagen fibers, having a characteristic periodicity of 67 nm, were imaged in situ for the first time; these structures were absent in dentin treated by phosphoric acid and subsequently vacuum dried, even after prolonged reimmersion in water. The AFM technique permitted us to demonstrate the important roles that moisture and etching play in the determination of the structure of collagen fibrils. Such structure may also play an important role in the diffusibility of subsequently applied dental adhesion systems.

Collagen↗
PubMed1993

Effects of dentin age and bonding on microgap formation.

This study compared the effectiveness of dentin adhesives in extracted molars from younger (16-26) and older (58-87) human subjects. Extracted molars were selected to be restored with one of two dentin bonding agents (n = 22 per group). Opposite sides of each molar were ground flat and a 3 mm x 3 mm cylindrical preparation was milled into each surface. The opposing surfaces of each molar were then randomly restored with either a dentin bonding system that adhered to the dentin smear layer or one which bonded to the dentin after the smear layer was removed. All samples were examined at x150 to determine both the maximum gap in micrometers and extent of the gap in degrees. There were significantly shorter (P < 0.05) microgaps in older dentin with a bonding system that removed smear layer. This bonding system also produced shorter gaps in older dentin than in younger dentin. However, there was no statistically significant difference in the percentage of gap-free margins between age groups.

Adolescent↗
PubMed1998

Interfacial ultrastructure of the resin-enamel region of three adhesive systems.

PURPOSE: To observe the resin/enamel interface produced by different adhesive systems. MATERIALS AND METHODS: A conventional three-step smear layer removing adhesive system (Scotchbond Multi-Purpose), a two-step smear layer removing adhesive system (Prime & Bond), and a two-step smear layer dissolving adhesive system containing a self-etching primer (Panavia 21) were evaluated. Flat enamel surfaces were obtained from approximal surfaces of 18 extracted human molars. A total of 36 surfaces were collected and divided into three groups of 12 samples. One-half of each specimen in each group was etched with 35% phosphoric acid prior to the application of each adhesive system, with the second half being kept unetched. Subsequently, resin composite was placed and polymerized for 40 seconds. The samples were fractured and immersed into HCl and NaOCl solutions, followed by critical point drying and sputter coating for examination with a field emission scanning electron microscope. RESULTS: In the etched samples, Panavia 21 and Scotchbond Multi-Purpose showed more consistent resin tag penetration than did Prime & Bond. Unetched Prime & Bond and Scotchbond Multi-Purpose samples showed minimal or no adhesive penetration in enamel surfaces.

Acid Etching, Dental↗
PubMed1990

Evaporative water loss from human dentine in vitro.

The rate of spontaneous evaporation of water from dentine was measured in extracted human teeth in vitro. Spontaneous water loss was the same with or without a smear layer. When air was blown on the dentine, the rate of evaporation increased significantly. After removal of the smear layer, the air blast-induced evaporative loss was twice as great as before its removal. Thus, with a smear layer present, evaporation is the major route by which fluid is lost from dentine rather than by filtration of dentinal fluid. After smear layer removal, fluid filtration sometimes may exceed the spontaneous rate of fluid evaporation.

Body Water↗
PubMed1990

A clinical scanning electron microscope study of tooth surface preparation and bonding.

This clinical study utilized cut dentine surfaces on which the Creation Bond System and Scotchbond were applied after various surface treatments. It was observed under the scanning electron microscope that preparation with a tungsten carbide bur left a smear layer on the dentine. When this surface was pumiced, the smear layer remained and the tubules were plugged with smear debris. Polyacrylic acid and citric acid removed the smear layer from the dentine surface. When the Creation Bond System was applied to the surface treated with polyacrylic acid, hollow depressions were produced. Application of the Creation Bond System to the surface treated with citric acid resulted in some resin tag formation into the dentinal tubules as well as hollow depressions on the resin surface. The presence of these irregularities in the resin indicated fluid from the dentinal tubules prevented contact of the bonding resin with the dentine surface. This degree of contamination was not observed when Scotchbond was applied to a pumiced dentine surface.

Acid Etching, Dental↗
PubMedDate not supplied

Protective effects of cavity liners on dentin.

Smear layers are very soluble in acidic solutions. Removal of smear layers increases dentin permeability and the potential for pulpal irritation. In this study, smear layers were treated with either saline, Barrier, Copalite, LC-Scotchbond, Hydroxyline, or DDS 1 & 2 to determine how well they protected the dentin from subsequent acid attack with 37% phosphoric acid for two minutes. Using both SEM and permeability measurements, the materials were ranked from least to most effective as: Saline less than Barrier = Copalite less than Hydroxyline = Scotchbond = DDS 1 & 2.

Acid Etching, Dental↗
PubMed1996

A pilot study of lactic acid as an enamel and dentin conditioner for dentin-bonding agent development.

The purpose of this pilot study was to determine how lactic acid solution at various concentrations and etching times affected prepared human enamel and dentin surfaces and to assess whether it could be used in place of phosphoric or maleic acid as an etchant. The occlusal surfaces of extracted molar teeth were ground wet with 600-grit silicon carbide paper and treated with various aqueous solutions of lactic acid. Random samples were prepared for observation by scanning electron microscopy. The rest were used to determine shear bond strength of bonded dental composite cylinders. The micrographs revealed that lactic acid dissolved the smear layer with various degrees of etching and demineralization. The degree of smear layer and matrix removal was proportional to the concentration of the acid and the length of application time. A 20% lactic acid concentration applied for 10 seconds produced a clearly etched surface with minimal demineralization. A 30% concentration not only removed the smear layer and enlarged the dentin tubule orifices but also appeared to affect the collagen matrix. The shear bond strength to enamel treated with 50% lactic acid (17.5 +/- 1.5 MPa) and All-Bond 2 etchant (18.9 +/- 1.3 MPa) were not significantly different (p > 0.05). However, mean dentin bond strengths for all groups of lactic acid etchant and All-Etch etchant (10% phosphoric acid) were statistically similar.

Acid Etching, Dental↗
PubMed2005

The effect of high-frequency electrical pulses on organic tissue in root canals.

AIMS: To evaluate debris and smear layer scores after application of high-frequency electrical pulses produced by the Endox Endodontic System (Lysis Srl, Nova Milanese, Italy) on intact pulp tissue and organic and inorganic residues after endodontic instrumentation. METHODOLOGY: The study comprised 75 teeth planned for extraction. The teeth were randomly divided into two groups (60 teeth) and a control group (15 teeth): group 1 (30 teeth) was not subjected to instrumentation; group 2 (30 teeth) was instrumented by Hero Shaper instruments and apical stops were prepared to size 40. Each group was subdivided into subgroups A and B (15 teeth); two electrical pulses were applied to subgroups 1A and 2A (one in the apical third and one in the middle third, respectively, at 3 and 6 mm from the root apices); four electrical pulses were applied to subgroups 1B and 2B (two in the apical third, two in the middle third). The control group (15 teeth) was prepared with Hero Shapers and irrigated with 5 mL of EDTA (10%) and 5 mL of 5% NaOCl at 50 degrees C but not subjected to the electrical pulse treatment. Roots were split longitudinally and canal walls were examined at 80x, 200x, 750x, 1500x and 15,000x magnifications, using a scanning electron microscope. Smear layer and debris scores were recorded at the 3 and 6 mm levels using a five-step scoring scale and a 200-microm grid. Means were tested for significance using the one-way anova model and the Bonferroni post-hoc test. The differences between groups were considered to be statistically significant when P < 0.05. RESULTS: The mean value for debris scores for the three groups varied from 1.80 (+/-0.77) to 4.50 (+/-0.68). The smear layer scores for group 2 and the control specimens varied from 2.00 (+/-0.91) to 2.33 (+/-0.99). A significant difference was found in mean debris scores at the 3 and 6 mm levels between the three groups (P < 0.001). The Bonferroni post-hoc test confirmed that the difference was due to group 1. In the two subgroups treated with four high-frequency pulses (1B and 2B) a substantial reduction in mean debris scores was found at the 3 and 6 mm level; subgroup 2B was practically free of organic residue. No significant differences for mean smear layer and debris scores were recorded between group 2 and the control group at the two levels; a significant difference was found only for mean smear layer scores at the 3 mm level between subgroup 2B and the control group (P < 0.05). CONCLUSIONS: The Endox device used with four electrical pulses had optimal efficacy when used after mechanical instrumentation. Traditional canal shaping and cleaning was essential to ensure an effective use of high-frequency electrical pulses in eliminating residues of pulp tissue and inorganic debris.

Adult↗
PubMed2003

[Intratubular penetration of root canal sealers].

The purpose of this study was to evaluate the capacity of penetration of four endodontic sealers (Endo Fill, Sealapex, AH Plus and Pulp Canal Sealer) into dentinal tubules. Seventy-two extracted human maxillary anterior teeth were utilized in this study. The teeth were cleaned and shaped by means of the balanced-forces technique. The work length was established at 1 mm beyond the apex. Copious irrigation with 10 ml of 5.25% sodium hypochlorite was carried out. The teeth were divided in 8 groups - 4 had the smear layer maintained, and 4 had it removed. The smear layer was removed with a commercial solution of 17% EDTA, and the root canal system was flushed for 3 min. Finally, the roots were irrigated with 3 ml of 5.25% sodium hypochlorite. All teeth were sealed by means of the technique of the condensation wave with a medium nonstandardized cone. After filling, the roots were grooved, longitudinally split and examined under a scanning electron microscope (SEM). The focus of observation was the interface between the dentin and the sealing material. The Rickert sealer (Pulp Canal) presented the maximum penetration depths into the dentinal tubules, and Sealapex, the minimum. The Spearman test was used to determine whether there were significant differences between the groups. The removal of smear layer allowed significant penetration of the sealers (p <= 0.01).

Dental Cements↗
PubMed1998

The effect of 4% titanium tetrafluoride solution on root canal walls--a preliminary investigation.

The aim of the present study was to evaluate the effect of 4% titanium tetrafluoride (TiF4) solution on root canal walls by scanning electron microscopy. Twenty four root canals with or without a smear layer were treated with 4% TiF4 solution. Scanning electron microscopic observation of the smeared canal walls showed that TiF4 solution modified the smear layer and produced a massive structure. In smear-free group, a granular coating was formed on intertubular and intratubular dentin. The stability of this layer was tested further with EDTA and/or NaOCl irrigations on 20 additional specimens. It was observed that none of the solutions was able to remove this modified smear layer. These results may indicate that this extremely stable structure may be advantageous in endodontics, because it can prevent further infection of root canal dentin by sealing off the tubules permanently, and can reduce microleakage by preventing further dissolution and disintegration of the smear layer.

Cariostatic Agents↗
PubMed2001

The burnishing effect of sodium (saline) chloride on root dentin: an in vitro study.

The purpose of this in vitro study was to evaluate the burnishing effect of saline application on dentin specimens (NaCl 0.9%). Seventy-two dentin specimens (60 experimental and 12 controls) were equally divided into two groups. In Group A; sub-groups I, II, III, IV and V were respectively soaked with saline for 5 s, 10 s, 30 s, 1 min and 2 min. Group VI was soaked in citric acid for 3 min and served as control. Identical treatment was done in-group B with one exception, burnishing instead of soaking was applied to the root surface. Five, ten and thirty seconds burnishing with saline and all the different timings with the soaking technique did not remove the smear layer. This was in contrast to burnishing dentin surface for 1 and 2 min, which effectively removed the smear layer. It cannot be excluded that the smear layer removal is time dependent when the dentin is burnished with saline.

Administration, Topical↗
PubMed2000

Cleaning efficacy of a new root canal irrigation solution: a preliminary evaluation.

AIM: A new product, electro-chemically activated water, was compared to NaOCl for its cleaning effect on root canal walls. METHODOLOGY: Root canal treatment was carried out on two groups of extracted teeth with one of the irrigants being used in each group. The control group received no treatment. All teeth were split and the canal walls viewed in a scanning electron microscope. RESULTS: The canal walls of the control group were covered by debris and bacteria. Sodium hypochlorite produced clean surfaces with the dentinal tubules open in some areas and occluded by the smear layer in other areas; in some areas bacteria were visible inside or under the smear layer. Electro-chemically activated water produced markedly cleaner surfaces, removing the smear layer in large areas. CONCLUSIONS: The cleaning efficacy of electro-chemically activated water in root canals was considered to be superior to NaOCl.

Bacteria↗
PubMed2005

Effectiveness in cleaning oval-shaped root canals using Anatomic Endodontic Technology, ProFile and manual instrumentation: a scanning electron microscopic study.

AIM: To compare in vitro the cleanliness of root canal walls in oval-shaped root canals following automated or manual instrumentation. METHODOLOGY: Forty-five oval-shaped single-rooted maxillary and mandibular premolars with straight canals were divided into three groups of 15. Automated canal preparation was performed using Anatomic Endodontic Technology (AET, group 1) and the ProFile system (group 2). Manual instrumentation (group 3) was performed with K-Flexofiles. Irrigation was performed using alternately 5.25% NaOCl and 17% EDTA, followed by rinsing with saline. The roots were split longitudinally into halves and the canals examined at x200 and x400 in a scanning electron microscope. The presence of debris and smear layer was recorded at distances of 1, 5 and 10 mm from the working length using a three-step scoring scale and a 300 mum square grid. Mean scores for debris and smear layer were calculated and statistically analysed for significance (P < 0.05) between and within groups, using the Kruskal-Wallis nonparametric anova and Dunn's tests. RESULTS: At 1, 5 and 10-mm levels the root canals prepared with AET had significantly less surface debris and smear layer on the canal walls compared with canals prepared with ProFile or manual instrumentation. For all three groups significantly lower mean smear layer scores (P < 0.05) were recorded at 5 and 10-mm levels compared with the 1 mm level. Significantly lower mean debris scores (P < 0.05) were also recorded at 5 and 10-mm levels for the AET group whereas no significant differences were found between the three levels for the ProFile and manual instrumentation groups. CONCLUSIONS: Although better instrumentation scores were obtained in canals prepared with AET, complete cleanliness was not achieved by any of the techniques and instruments investigated.

Analysis of Variance↗
PubMed1992

Morphological aspects of the resin-dentin interdiffusion zone with different dentin adhesive systems.

Cross-sections of resin-dentin interfaces were etched with an argon-ion beam to make their substructure detectable by scanning electron microscopy. The dentin adhesive systems were categorized morphologically into three groups, and an attempt was made to clarify their adhesive mechanism. The first group of products removed the smear layer. The argon-ion bombardment clearly disclosed a hybrid or resin-impregnated dentin layer. It is hypothesized that conditioning with acidic or chelating agents demineralized the dentin surface-layer to a certain depth, leaving behind a collagen-rich mesh-work. Hydrophilic monomers are then believed to alter this collagen-fiber arrangement in a way that facilitates penetration of the adhesive resin, resulting in a mechanical, intermingled link between collagen and the adhesive resin. The second group preserved the smear layer. In this case, the dentinal tubules were obliterated with globular particles at their orifices and remained patent underneath these smear plugs. This type of adhesive system aims at the incorporation of the smear layer into the hydrophilic monomers, which have an affinity for the organic and/or inorganic components of the underlying dentin. Finally, a third, small group only partly dissolved the smear layer, creating a thin resin-impregnated dentin layer and a resin-impregnated smear plug. This study clearly showed that the application of recent adhesive systems induced structural changes in the dentin surface morphology, creating a retentive interface, called the inter-diffusion zone, between the deep, untouched dentin layers and the composite filling material. This resin-dentin interdiffusion zone offers bonding sites for copolymerization with the resin composite and, concurrently, might have protective potential for the pulp tissues.

Acid Etching, Dental↗
PubMedDate not supplied

Permeability of root dentin to epinephrine released from gingival retraction cord.

The permeation of racemic epinephrine across roots of human molar crown segments was studied in vitro. Permeation was measured in the presence of cementum, with cementum removed (dentin exposed), and with and without dentin smear layers. Epinephrine was initially detected at 10 minutes and reached a steady state in 70 minutes. Epinephrine flux (the product of concentration and the flow rate per unit of dentin surface area) significantly increased when both the cementum and dentin smear layers were removed. The T1/2 (half-time in minutes necessary to reach steady-state diffusion) was zero with intact cementum and increased to approximately 40 minutes in dentin with and without smear layers. This study suggests that the permeation of epinephrine across root surfaces is prevented by the presence of cementum and retarded by the presence of dentin smear layers. Also, the data suggest that root dentin is another source of absorption when epinephrine-impregnated retraction cord is applied to the gingival sulcus.

Absorption↗
PubMed1997

Dentinal adhesion and histomorphology of two dentinal bonding agents under the influence of eugenol.

This study examined the influence of eugenol on the dentinal adhesion of an enamel-dentin bonding agent that removes the smear layer (total-etch technique) and a system that partially dissolves the smear layer (self-conditioning adhesive system). The tensile bond strength was measured on flat, dentinal surfaces after application and removal of pure eugenol for 15 minutes and a eugenol-containing temporary luting agent for 24 hours. In addition, the resin-dentin interface was evaluated with confocal laser scanning microscopy. Dentinal adhesion was found to be significantly reduced after the application of eugenol when a dentin bonding agent that dissolves the smear layer was used. Under confocal laser scanning microscopy, the resin-dentin interdiffusion zone of both adhesive was found to be changed, not only after application of eugenol but also after application of a eugenol-containing temporary luting agent.

Adhesiveness↗
PubMed1991

Pulpal response to chemically cured and experimental light-cured glass ionomer cavity liners.

This investigation evaluated the effects of an experimental light-cured glass ionomer (LCGI) cavity liner and chemically cured Ketac-Bond glass ionomer restorative material on the pulpal tissues of monkeys. Class V cavities were prepared in 71 teeth of three adult Macaca mulatta monkeys at 7- and 35-day intervals. Ketac-Bond or LCGI cavity liners were placed in cavities with the smear layer intact (groups I and II) or with the smear layer removed (groups III and IV) and were restored with composite resin. Tissues were acquired, sectioned at 7 microns, stained for microscopic evaluation, or prepared for SEM evaluation. No statistically significant differences between materials existed at either time interval, regardless of smear layer presence. Histopathologic results demonstrated minimal pulpal reactions for groups I through IV. SEM analysis showed tenacious bonding of the LCGI material to prepared cavity walls, with absence of contraction gap formation. The results indicated excellent pulpal responses to both materials.

Acid Etching, Dental↗