Qualitative analysis of smear layer treated with different etidronate concentrations: A scanning electron microscopy study.

The aim of this study was to examine the smear layer removal capacity of various etidronate treatments. Seventy-eight roots were instrumented up to apical size X4 and randomly divided into five treatment groups and a positive control group (n = 13). Groups were as follows: irrigation with 5 ml of sterile saline (control) for 3 min, 5 ml of 17% ethylenediaminetetraacetic acid (EDTA) for 3 min, 5 ml of 9% A1-hydroxyethylidene-1,1-bisphosphonate (HEBP) for 3 min, 5 ml of 18% HEBP for 3 min, irrigation with 5 ml of 1% sodium hypochlorite (NaOCl) + 9% HEBP for 3 min, and 5 ml of 2% NaOCl + 18% HEBP for 3 min. The roots were examined using a scanning electron microscope. The smear layer scores in the 2% NaOCl + 18% HEBP group were lower than those in the other treatment groups and the control group (p < .05). There were no significant differences among the treatment groups in the smear layer scores of the coronal and middle thirds. However, the smear layer scores in the 2% NaOCl + 18% HEBP treatment group were lower those in the 9% HEBP and 18% HEBP treatment groups in the apical third (p < .05). In the clinical setting, the recommended concentration of HEBP is 18%, and it should be used with an oxidizing agent to ensure optimum smear layer removal.

Effect of EDTA, sodium, and calcium hypochlorite on the inorganic component of root canal dentin: A SEM analysis.

This study evaluated the influence of canal irrigation protocols with 5.25% calcium hypochlorite [Ca(OCl)2 ], 5.25% sodium hypochlorite (NaOCl) and 17% EDTA solution on the inorganic component of root canal dentin. Sixty roots were randomly divided into six groups (n = 10): Saline solution (SS) (control); Saline solution (SSE) +17% EDTA; CH - 5.25% Ca(OCl)2 ; CHE - 5.25% Ca(OCl)2 + 17% EDTA; SH - 5.25% NaOCl; SHE - 5.25% NaOCl +17% EDTA. After canal irrigation, the specimens were longitudinally split and analyzed by scanning electron microscopy (SEM). Dentinal tubules were observed in transverse (middle and apical thirds) direction. The images were classified in scores, according to smear layer removal and peritubular dentin alteration, and data were analyzed by Kruskal-Wallis's test, followed by Dunn's test (α = 0.05). In the middle third, all groups with EDTA presented better removal of the smear layer with higher peritubular dentin alteration (p < .05). In the apical third, this happened only in SHE (p < .05). Ca(OCl)2 and NaOCl exhibit similar performance to remove smear layer and alteration of the inorganic component in the middle third. In the apical third, NaOCl associated with EDTA showed better performance in smear layer removal.

Smear Layer Removal Efficacy Using EndoActivator and EndoUltra Activation Systems: An Ex Vivo SEM Analysis.

OBJECTIVE: This study evaluated intracanal smear layer removal using syringe and needle irrigation (ie, conventional irrigation [CI]) with and without adjunctive activation using EndoActivator® or EndoUltra®. MATERIALS AND METHODS: Thirty-five premolars were divided into three experimental groups (n = 10) and a control (n = 5): (1) CI, (2) CI plus sonic activation (EndoActivator), (3) CI plus ultrasonic activation (EndoUltra), or (4) CI using saline. All teeth were prepared to a size #40 K file. Following irrigation, the teeth were split and imaged using scanning electron microscopy (SEM). SEM images were evaluated by: (1) blinded researchers who provided a smear layer score (1-5), and (2) a custom software algorithm that automatically and independently quantified the number of open tubules. RESULTS: Use of both the EndoActivator and EndoUltra resulted in significantly cleaner smear layer scores at all canal thirds compared to CI (P < .001). The EndoUltra yielded significantly cleaner scores than the EndoActivator at the apical third (P < .001); however, no significant difference was evident in the middle and coronal thirds. The software analysis yielded the same conclusions as the smear layer scores except statistical significance was seen between the EndoUltra and EndoActivator at all canal thirds (P < .02). Of the adjunctive irrigant activators, the EndoUltra opened 94%, 117%, and 26% more tubules in the apex, middle, and coronal thirds, respectively, than the EndoActivator. CONCLUSIONS: The EndoUltra cleaned canals more effectively than the EndoActivator and CI.

Evaluation of 17% EDTA and 10% citric acid in smear layer removal and tubular dentin sealer penetration.

The purpose of this study was to compare the efficacy of different chelating solutions (17% EDTA and 10% citric acid) on the smear layer removal, and their effect on tubular dentin sealer penetration. Sixty root canals were prepared and distributed into four groups (n = 15) according to the final irrigation protocol: G1, final irrigation with 2.5 mL of distilled water; G2, final irrigation with 2.5 mL of 2.5% sodium hypochlorite solution; G3, final irrigation with 2.5 mL of 17% EDTA; and G4, final irrigation with 2.5 mL of 10% citric acid. Five specimens from each group were not filled to assess smear layer removal by scanning electron microscopy. Ten specimens from each group were filled for analysis of sealer penetration into dentinal tubules by confocal laser scanning microscopy. Smear layer removal (Kruskal-Wallis and Dunn's tests) and sealer penetration (F and Tukey's tests) were statistically analyzed with 95% of significance level. G3 and G4 had greater smear layer removal rates in the cervical and middle thirds, in comparison with G1 and G2 (p < .05). G3 and G4 had the highest percentages of sealer penetration in all thirds, in comparison with G1 and G2 (p < .05). Smear layer removal was effective only at the cervical and middle thirds when the chelating solutions were used. Sealer penetration into the dentinal tubules significantly increased in all root thirds when the specimens were treated with both chelating solutions.

Evaluation of the effect of four final irrigation protocols on root canal dentin components by polarized light microscopy and scanning electron microscopy.

The present study aimed to evaluate the effects of four endodontic chelating agents, followed by 2.5% sodium hypochlorite (NaOCl), as final irrigation regimens on organic and inorganic components of human root dentin. Sixty mandibular incisors were prepared and randomly divided into six groups (n = 10): QMiX, 1% peracetic acid (PA), 17% EDTA, 10% citric acid (CA), 2.5% NaOCl (solution control) and distilled water (DW-negative control). After irrigation with the chelating agents, a final flush was performed with 2.5% NaOCl. The specimens were split longitudinally in halves; one was designated for organic component analysis by polarized light microscopy (PLM) and the other for inorganic structure analysis by scanning electron microscopy (SEM). Scores data obtained in the PLM analysis were submitted to Kruskal-Wallis' test, followed by Dunn's test (p < .05). SEM findings were presented descriptively. NaOCl and DW groups showed uniformity in the fibrillar network and smear layer obliterating the dentinal tubules, while CA group presented alteration in organic and inorganic components of dentin. EDTA group did not show differences from others in the organic component, but altered the inorganic structure. QMiX and PA groups did not cause a significant morphological alteration in collagen and removed the smear layer without inorganic structure modification. As final irrigation, QMiX and PA solutions, followed by 2.5% NaOCl, showed better behavior than the other chelating agents tested, preserving organic and inorganic components of human root dentin.

Efficacy of Photon-induced Photoacoustic Streaming in the Reduction of Enterococcus faecalis within the Root Canal: Different Settings and Different Sodium Hypochlorite Concentrations.

INTRODUCTION: The purpose of this study was to determine the effectiveness of laser-activated irrigation by photon-induced photoacoustic streaming (PIPS) in the reduction of Enterococcus faecalis in root canal disinfection, varying laser energy output, and sodium hypochlorite (NaOCl) concentration. For effective removal of the smear layer, the sequence and resting time of the final irrigation steps were modified compared with the standard PIPS protocol. METHODS: Eighty-six extracted single-rooted teeth were mechanically prepared, sterilized, and inoculated with E. faecalis for 4 weeks. Teeth were divided into 9 groups and treated with an Er:YAG laser using a PIPS 600/9 tip at the following parameters: 10 mJ or 20 mJ, 15 Hz, and a 50-microsecond pulse duration at 0.15 W or 0.3 W average power, respectively. Root canals were irrigated with different concentrations of NaOCl (ie, 1%, 3%, and 5% and activated using the adjusted PIPS protocol). The bacterial count was performed immediately after and 48 hours after decontamination and new incubation on an agar plate. RESULTS: A statistically significant difference in bacterial counts (P < .05) was detected in all groups before and directly after the treatment and in groups treated with 5% NaOCl 48 hours after treatment. Scanning electron microscopic imaging showed an absence of bacteria and biofilm in the scanned areas after treatment with 5% NaOCl. CONCLUSIONS: Laser-activated irrigation using 5% NaOCl and a modified PIPS protocol resulted in effective eradication of the bacterial biofilm and removal of the smear layer.

Evaluación de la penetración de cementos obturadores de canales mediante microscopía electrónica de barrido / Evaluation of the penetration of root canal filling cements through scanning electron microscopy

Antecedentes: la literatura odontológica demuestra que los tratamientos endodónticos fallidos, comúnmente son debidos a la persistencia de los microorganismos. Una característica importante de los cementos obturadores de canales es su habilidad para penetrar en los túbulos dentinarios, logrando así un sellado impermeable entre las paredes dentinarias y el material de obturación central, reduciendo las filtraciones potenciales y aumentando la resistencia a la fractura. Objetivo: Evaluar mediante microscopía electrónica de barrido (MEB) la penetración de MTA Fillapex, cemento de Grossman (CG) y top seal a lo largo del conducto radicular. Materiales y métodos: Estudio experimental in vitro, en 36 dientes premolares humanos divididos aleatoriamente en 3 grupos, (n= 12), los cuales fueron preparados con técnica endodóntica Step Back. Cada grupo se dividió en 2 subgrupos utilizando como irrigante NaOCl al 2,5%, al igual que NaOCl al 2,5% + EDTA al 17%. Los canales fueron obturados con técnica de condensación lateral, seccionados longitudinalmente para observar mediante microscopia electrónica de barrido a nivel de los tercios cervical, medio y apical, la penetración del cemento al interior de los túbulos dentinarios. Se realizó análisis estadístico con SPSS v 22 IBM con p< 0,05 y las pruebas Kruskal-Wallis y Mann-Whitney. Resultados: Mediante la prueba Kruskal-Wallis, los cementos de Grossman y top seal al utilizar NaOCl + EDTA presentaron valores de p= 0,025 y p= 0,002 en los tercios medio y apical respectivamente. La prueba de Mann Whitney mostró un valor p= 0,031 en el tercio apical para el cemento MTA Fillapex al utilizar NaOCl. Los valores de la mediana fueron MTA Fillapex tercio medio= 2,0000, tercio apical= 1,0000; top seal tercios medio y apical= 4,0000; cemento de Grossman tercios medio y apical= 4,0000. Al ser igual el valor de la mediana entre los cementos top seal y Grossman se utilizaron los valores de la varianza con un resultado estadísticamente significativo para el cemento de Grossman= 0,276 en el tercio medio y top seal= 0,176 en el tercio apical. La prueba de Mann Whitney arrojó un valor p= 0,031 en el tercio apical para el cemento MTA Fillapex. Con un valor de mediana de NaOCl= 3,0000, NaOCl + EDTA= 1,0000. Conclusiones: Al comparar los cementos obturadores MTA Fillapex, top seal y cemento de Grossman utilizando como irrigante NaOCl + EDTA se observó mayor penetración del cemento de Grossman. A nivel del tercio apical se observó mayor penetración con el cemento top seal. El cemento obturador MTA Fillapex presentó mayor penetración a nivel del tercio apical al utilizar como irrigante NaOC (AU)

Background: the literature has shown that failed endodontic treatments are commonly due to the persistence of microorganisms. One important characteristic of root canal filling cements is their ability to penetrate the dentinal tubules, achieving an impermeable sealing between the dentinal walls and the central filling material, reducing potential filtrations and increasing the resistance to fracture. Objective: To evaluate through scanning electron microscopy (SEM) the penetration of MTA Fillapex, Grossman sealer and top seal all along the root canal. Methods: In vitro experimental study, in 36 human teeth randomly divided into 3 groups, (n= 12), which were prepared with the Step Back endodontic technique. Each group was divided into 2 subgroups using NaOCl 2.5%, and NaOCl 2.5% + EDTA 17% as irrigating solutions. The root canals were sealed using the lateral condensation technique, longitudinally sectioned to observe through scanning electron microscopy the cervical, medium and apical thirds, the penetration of the cement inside the dentinal tubules. The statistical analysis was performed with SPSS v22 IBM with p < 0.05 and the Kruskal-Wallis and Mann-Whitney tests. Results: through the Kruskal- Wallis test the Grossman sealer and top seal when using NaOCl + EDTA showed values of p= 0.025 and p= 0.002 in the medium and apical thirds respectively. The Mann-Whitney test showed a value of p= 0.031 in the apical third for the MTA Fillapex when using NaOCl. The median values were MTA Fillapex medium third= 2.000, apical third= 1.000; top seal medium and apical thirds= 4.000. Since the median values between the top seal and Grossman sealer were the same, the values from the variance were used, with a statistically significant result for the Grossman sealer= 0.276 in the medium third and top seal = 0.176 in the apical third. The Mann-Whitney test showed a value p= 0.031 in the apical third for the MTA Fillapex. With a median value of NaOCl= 3.000, NaOCl + EDTA= 1.000. Conclusions: When comparing the filling cements MTA Fillapex, top seal and Grossman sealer using NaOCl + EDTA as an irrigating solution, more penetration from the Grossman sealer was observed in medium third. At the apical third, more penetration from the top seal sealer was observed. The MTA Fillapex cement showed the greatest penetration at the apical third when using NaOCl as an irrigating solution (AU)

Evaluation of smear layer removal and marginal adaptation of root canal sealer after final irrigation using ethylenediaminetetraacetic, peracetic, and etidronic acids with different concentrations.

The purpose of this study was to investigate the effects of different irrigation solutions on the smear layer removal and marginal adaptation of a resin-based sealer to root canal dentine. A total of 152 instrumented roots were irrigated with the following irrigants: 9,18% etidronic acid (HEBP), 0.5, 1,2% peracetic acid (PAA), 17% ethylenediaminetetraacetic acid (EDTA), saline. The amount of smear layer was evaluated using scanning electron microscope (SEM) in seventy root samples. Eighty-two roots were filled with AH Plus and gutta-percha. Slices obtained from apical third of each specimen were viewed with SEM to assess marginal adaptation. Use of 9% and 18% HEBP resulted in more efficient smear layer removal in the apical third than the other chelators (p < 0.05). Higher smear layer scores in the coronal and middle thirds were obtained from 0.5%, 1% PAA groups. Regarding marginal adaptation, 18% HEBP group showed the lowest gap size values (p < 0.05), and better marginal adaptation. Etidronic acid is a promising candidate for final irrigation of root canals.

Effectiveness of Rotary Endodontic Instruments on Smear Layer Removal in Root Canals of Primary Teeth: A Scanning Electron Microscopy Study.

AIM: The present SEM study was undertaken to evaluate the effect of root canal instrumentation using both manual and rotary files in the root canals of primary anterior teeth. STUDY DESIGN: Thirty freshly extracted primary maxillary incisors were divided into 3 groups of 10 teeth each. In Group I, root canals were instrumented with rotary NiTi files; in Group II, the root canals were instrumented using manual NiTi K files and; in Group III, manual instrumentation was done with stainless steel K files. Longitudinal sections were prepared and processed for observation under SEM at the coronal, middle and apical thirds. Scoring of smear layer was done according to Hulsmann and the data obtained was subjected to statistical analysis. RESULTS: Rotary files cleaned the coronal and middle thirds of root canals more effectively. Statistically there was no significant difference between the groups. Lowest score of 2.6 in the apical third of root canals was seen with hand NiTi files. CONCLUSION: Rotary instrumentation was as effective as manual instrumentation in removal of smear layer in the root canals of primary anterior teeth.

Comparison of curved root canals preparation using reciprocating, continuous and an association of motions.

The aim of this study was to compare the rotary ProTaper Universal system, the single-file reciprocating WaveOne system and an association of motions assessing shaping ability, cleanliness, preparation time and instrument failures after preparation of curved root canals. Sixty root canals of extracted human molar teeth, with curvatures ranging between 20° and 40°, were divided into three groups, according with preparation system. Canals were prepared until apical size 25 using the ProTaper Universal system (G1), WaveOne (G2), or a hybrid technique (G3) associating reciprocating preparation with rotary glide path and cervical pre-enlargement. Teeth were scanned pre and post-operatively using computed tomography. Direction of transportation and centering ability of canals were measured using a computer image analysis program, and the results were analyzed statistically using one-way ANOVA. Preparation time was analyzed by one-way ANOVA and the Tukey post hoc test. Instrument failures were recorded. The amounts of debris and smear layer were quantified based on a numerical evaluation scale by scanning electron microscopy and were analyzed statistically using the Kruskal-Wallis test. No difference in transportation and centering ratio was found between the systems. Instrumentation with WaveOne was significantly faster than with other instruments (p < 0.05). During preparation, no instruments fractured and three suffered deformations. For debris removal and remaining smear layer, the results for the three groups were similar. The single-file reciprocating instrument was capable of providing faster root canal preparation with similar transporting, centralization and cleaning ability when compared with continuous and an association of motions in curved canals. SCANNING 38:462-468, 2016. © 2016 Wiley Periodicals, Inc.

Comparisons of the Retreatment Efficacy of Calcium Silicate and Epoxy Resin-based Sealers and Residual Sealer in Dentinal Tubules.

INTRODUCTION: The aim of this study was to evaluate the retreatment efficacy and amount of residual sealer in a single canal filled with either EndoSequence BC (Brasseler, Savannah, GA) or AH Plus (Dentsply DeTrey, Konstanz, Germany). METHODS: Canal obturation with gutta-percha and sealer was performed in 28 human teeth using the continuous wave technique. Group 1 (n = 13) used AH Plus sealer, and group 2 (n = 15) used EndoSequence BC sealer. After 7 days, the root fillings were removed using Gates Glidden drills and a nickel-titanium rotary system. Retreatment time was measured in seconds. Canal cleanliness was examined by scanning electron microscopy. The remaining debris in the canal space and penetration into dentinal tubules were evaluated by confocal microscopy. Retreatment time was compared using the Student t test, and differences in sealer penetration and remaining debris between the groups were analyzed using the Mann-Whitney U test (P < .05). RESULTS: There was no significant difference between the 2 groups in the amount of dentin penetration, amount of debris, or retreatment time. With respect to penetration depth, the AH Plus group showed a slightly higher percentage than the BC group, with a significant difference only in the portion 6 mm from the apex (P < .05). Scanning electron microscopic images showed significant debris remaining on canal walls in both groups, whereas canal patency in retreatment was achieved in every specimen. CONCLUSIONS: The present study shows that EndoSequence BC sealer and AH Plus sealer have similar efficacy in dentin penetration and retreatment efficacy.

Chemical and morphological changes in human dentin after Er:YAGlaser irradiation: EDS and SEM analysis.

Sixty samples of human dentin were divided into six groups (n = 10) and were irradiated with Er:YAG laser at 100 mJ-19.9 J/cm(2), 150 mJ-29.8 J/cm(2), 100 mJ-35.3 J/cm(2), 150 mJ-53.0 J/cm(2), 200 mJ-70.7 J/cm(2), and 250 mJ-88.5 J/cm(2), respectively, at 7 Hz under a water spray. The atomic percentages of carbon, oxygen, magnesium, calcium, and phosphorus and the Ca-to-P molar ratio on the dentin were determined by energy dispersive X-ray spectroscopy. The morphological changes were observed using scanning electron microscopy. A paired t-test was used in statistical analysis before and after irradiation, and a one-way ANOVA was performed (P ≤ 0.05). The atomic percent of C tended to decrease in all of the groups after irradiation with statistically significant differences, O and Mg increased with significant differences in all of the groups, and the Ca-to-P molar ratio increased in groups IV, V, and VI, with statistically significant differences between groups II and VI. All the irradiated samples showed morphological changes. Major changes in the chemical composition of dentin were observed in trace elements. A significant increase in the Ca-to-P ratio was observed in the higher energy density groups. Morphological changes included loss of smear layer with exposed dentinal tubules. The changes produced by the different energy densities employed could have clinical implications, additional studies are required to clarify them.

Effect of Smear Layers Created by Different Burs on Durability of Self-Etching Adhesive Bond to Dentin of Primary Teeth.

AIM: The aim of this study was to evaluate the effects of a smear layer generated by a high-speed diamond or carbide bur on the durability of microtensile bond strength (µTBS) of a self-etching adhesive to primary dentin. STUDY DESIGN: Flat occlusal dentin surfaces of 105 human primary molars were exposed using 600 grit silicon carbide paper before being divided into 2 groups for further grinding with either a highspeed diamond or carbide bur. Ten prepared dentin surfaces treated by each bur were evaluated for the characteristics of the smear layer using a scanning electron microscope (SEM). Seventy-five specimens from each bur-prepared group were applied with a 2-step self-etching adhesive (Clearfil SE Bond(®)) then built up with a resin composite. Each bonded specimen was sectioned into a 1-mm thick slab and trimmed to a dumbbell shape with a cross-sectional area of approximately 1 mm(2). All slabs were divided into 3 groups (n=25) according to 3 storage times of 24 hrs, 3 months, and 6 months, in distilled water at 37°C. After storage, the µTBS was determined using a universal testing machine. All fracture specimens were prepared for observation of failure modes. Ten bonded specimens of each bur group were prepared for observation of the resin-dentin interface using an SEM. Smear-layer thickness, µTBS, and failure mode distributions were statistically analyzed. RESULTS: The high speed carbide bur created a significantly thinner smear layer than the diamond bur (p < 0.05). Dentin surfaces treated with a high-speed carbide bur generally obtained significantly higher µTBS than the diamond bur group (p < 0.05). The µTBS gradually decreased over time such that specimens stored for 6 months had significantly lower bond strength than those stored for 24 hrs (p < 0.05). Self-etching adhesive created a hybrid layer of the same thickness when prepared with either a carbide bur or diamond bur, but the carbide bur group had longer and more resin tags. CONCLUSION: Highspeed carbide bur groups had a higher µTBS than diamond bur groups for all storage times, and bond strengths decreased over time in both substrate groups. The use of a carbide bur produced a thinner smear layer and therefore is recommended when using this 2-step self-etching adhesive to bond the resin composite to primary dentin.

Comparative evaluation of smear layer removal by various chemomechanical caries removal agents: an in vitro SEM study.

OBJECTIVES: To comparatively evaluate the efficiency of various chemomechanical caries removal agents in smear layer removal. MATERIALS AND METHODS: Class V cavities were prepared on the buccal surface of 45 extracted, noncarious molars and were divided into three groups according to the chemical treatment received. The samples were then gold palladium coated and viewed under scanning electron microscope. The presence of smear layer was evaluated based on the microscopic observations. Result and Observation: The results indicated that smear layer removal was significantly higher in the sodium hypochlorite-based chemomechanical caries removal agents than in the papain-based chemomechanical caries removal agent and was least in the control group treated with saline. CONCLUSION: The smear layer removal was maximum with Carisolv followed by the cariecare and was minimum in the saline-treated group.

Evaluation of different irrigating solutions on smear layer removal of primary root dentin.

AIM: To evaluate the efficacy of ethanolic extract of Salvadora persica (S. persica) and BioPure MTAD (a mixture of a tetracycline isomer, an acid, and a detergent) in removing the intracanal smear layer of primary teeth. MATERIALS AND METHODS: The root canal of 40 extracted human primary anterior teeth were cleaned, shaped and grouped into experimental (n = 30) and control (n = 10). The root canals of the positive (n = 5) and the negative control (n = 5) were irrigated for 3 minutes with 5 ml of 17% ethylenediaminetetraacetic acid (EDTA) or saline respectively. The canals in the experimental groups were irrigated for 3 minutes with 5 ml of 1 mg/ml ethanolic extract of S. persica (n = 15) or BioPure MTAD (n = 15) and then flushed with 2 ml of saline. The presence or absence of smear layer at the coronal and middle portion of each canal were examined under a scanning electron microscope (SEM). RESULTS: A significant difference (p = 0.004) in smear layer removal between S. persica and MTAD at the middle third of the canal was observed. MTAD solution was as effective as 17% EDTA in removing the smear layer. CONCLUSION: MTAD was significantly more effective in smear layer removal than S. persica solution at the middle third of the canal wall. CLINICAL SIGNIFICANCE: Both tested irrigant solutions have the ability to remove the intracanal smear from primary root dentin following cleaning and shaping of the root canal and could be an alternative to EDTA.

Effect of super short pulse Er:YAG laser on human dentin--Scanning electron microscopy analysis.

This study evaluated the effect of different pulse widths in the morphological characteristics of human dentin irradiated with Er:YAG in cavity preparation protocols and dentin pretreatment. Dentin discs with 2 mm thickness were obtained from 18 human molars. The experimental groups were composed from two variables: (1) clinical protocol-cavity preparation (E = 200 mJ/20 Hz)-and pretreatment (E = 80 mJ/2 Hz); and (2) pulse duration-50, 300, and 600 µs. This formed six experimental groups (n = 3): G1 (E = 200 mJ/20 Hz/50 µs); G2 (E = 200 mJ/20 Hz/300 µs); G3 (E = 200 mJ/20 Hz/600 µs); G4 (E = 80 mJ/2 Hz/50 µs); G5 (E = 80 mJ/2 Hz/300 µs); G6 (E = 80 mJ/2 Hz/600 µs). The samples were irradiated with the Er:YAG laser by noncontact mode at a focal distance of 7 mm from the target point under continuous water spray (60% water and 40% air). After the irradiation, they were processed for scanning electron microscopy (SEM). Morphological analysis showed an irregular dentin surface, absence of smear layer with opening of the exposure of dentinal tubules and protruding peritubular dentin-without indications of changes for all protocols used. Regardless of the analyzed experimental group, the dentin surface showed a microretentive morphology characteristic of ablation. The G1 and G4 showed a rougher surface when compared to other groups. Finally, we concluded that the pulse width can influence the morphological characteristics of the irradiated dentin tested in different clinical indications. The larger surface irregularity caused by regulation with less pulse width (50 µs) seems more appropriate to get a microretentive pattern necessary for successful adhesives restoration procedures.

The smear layer created by scaling and root planing is physiologically eliminated in a biphasic process.

Mechanical instrumentation of the root surface causes the formation of a smear layer, which is a physical barrier that can affect periodontal regeneration. Although different procedures have been proposed to remove the smear layer, there is no information concerning how long the smear layer persists on root surfaces after instrumentation in vivo. This study assessed the presence of the smear layer on root surfaces over a 28-day period after subgingival instrumentation with hand instruments. Fifty human teeth that were referred for extraction because of advanced periodontal disease were scaled and root planed (SRP) by a single experienced operator. Ten teeth were randomly assigned to be extracted 7, 14, 21, and 28 days after SRP. Another 10 teeth were extracted immediately after instrumentation (Day 0, control group). The subgingival area of the instrumented roots was evaluated with scanning electron microscopy. Representative photomicrographs were assessed by a blinded and calibrated examiner according to a scoring system. A rapid and significant (p < 0.05, Z test) initial reduction in the amount of smear layer was observed at 7 days, and a further significant (p < 0.05) decrease was observed 28 days after SRP. Interestingly, even 28 days after SRP, the smear layer was still present on root surfaces. This study showed that the physiological elimination of the smear layer occurred in a biphasic manner: a rapid initial reduction was observed 7 days after instrumentation, which was followed by a slow process leading to a significant decrease 28 days after instrumentation.

Shear Bond Strength of Self-etching Adhesives to Cavities Prepared by Diamond Bur or Er,Cr:YSGG Laser and Effect of Prior Acid Etching.

PURPOSE: To compare and evaluate shear bond strength of self-etching adhesives bonded to cavities prepared by diamond bur or Er,Cr:YSGG laser and the effect of prior acid etching on shear bond strength. MATERIALS AND METHODS: Ninety-six caries-free human premolars were selected and divided into 2 groups depending on mode of cavity preparation (48 teeth each). Cavities were prepared with Er,Cr:YSGG laser in group 1 and diamond burs in an air-turbine handpiece in group 2. Groups 1 and 2 were further subdivided into three subgroups of 8 teeth each, which were bonded with sixth- or seventh-generation adhesives with or without prior acid etching, followed by restoration of all samples with APX Flow. These samples were subjected to shear bond strength testing. In addition, the surface morphology of 24 samples each from groups 1 and 2 was evaluated using SEM. Data were analyzed using the Shapiro-Wilk test, one- and two-way ANOVA, the t-test, and the least significant difference test, which showed that the data were normally distributed (p > 0.05). RESULTS: The shear bond strength of adhesives in cavities prepared by Er,Cr:YSGG laser was significantly higher than in diamond bur-prepared cavities (p < 0.05). SEM analysis showed a smear-layer-free anfractuous surface on laser-ablated teeth, in contrast to conventional bur-prepared teeth. CONCLUSIONS: The Er,Cr:YSGG laser-ablated surface proved to be more receptive for adhesion than those prepared by diamond bur irrespective of the bonding agent used. Seventh-generation adhesives yielded higher shear bond strength than did sixth-generation adhesives. Prior acid etching decreased the shear bond strength of self-etching adhesives.

Adhesive sealing of dentin surfaces in vitro: A review.

PURPOSE: This review describes the evolution of the use of dental adhesives to form a tight seal of freshly prepared dentin to protect the pulp from bacterial products, during the time between crown preparation and final cementation of full crowns. The evolution of these "immediate dentin sealants" follows the evolution of dental adhesives, in general. That is, they began with multiple-step, etch-and-rinse adhesives, and then switched to the use of simplified adhesives. METHODS: Literature was reviewed for evidence that bacteria or bacterial products diffusing across dentin can irritate pulpal tissues before and after smear layer removal. Smear layers can be solubilized by plaque organisms within 7-10 days if they are directly exposed to oral fluids. It is likely that smear layers covered by temporary restorations may last more than 1 month. As long as smear layers remain in place, they can partially seal dentin. Thus, many in vitro studies evaluating the sealing ability of adhesive resins use smear layer-covered dentin as a reference condition. Surprisingly, many adhesives do not seal dentin as well as do smear layers. RESULTS: Both in vitro and in vivo studies show that resin- covered dentin allows dentin fluid to cross polymerized resins. The use of simplified single bottle adhesives to seal dentin was a step backwards. Currently, most authorities use either 3-step adhesives such as Scotchbond Multi-Purpose or OptiBond FL or two-step self-etching primer adhesives, such as Clearfil SE, Unifil Bond or AdheSE.

Scanning electron microscopic evaluation of root canal surfaces prepared with three rotary endodontic systems: Lightspeed, ProTaper and EndoWave.

BACKGROUND AND OBJECTIVES: The purpose of this in vitro study was to evaluate and compare the cleaning efficiency, preparation time, instrument deformation and fracture with LightSpeed (LS), ProTaper (PT) and EndoWave (Ew) rotary instruments. MATERIALS AND METHODS: A total of 45 freshly extracted human mandibular premolars were subjected for the study. They were divided into three groups, each group consisting of 15 teeth. Group 1: The canals were prepared with LS system; Group 2: PT rotary system, Group 3: Ew rotary system. All the groups were prepared according to manufacturer's recommendation, using 5.25% sodium hypochlorite and 17% ethylenediaminetetraacetic acid (dent wash, prime dent) alternately as an irrigants. Crowns of each tooth were removed with diamond disks at the level of cemento enamel junction. Canal length was determined by placing a size 10 K-file. The working length was 0.5 mm short of canal length. Two longitudinal grooves were prepared on the lingual and buccal surfaces of each root to facilitate vertical splitting with a chisel after canal instrumentation. The sections were then observed under scanning electron microscope for presence or absence of debris and smear layer and the photographs were taken at coronal, middle and apical 1/3 with a magnification of × 200 and × 1000 respectively. The time taken to enlarge each canal was recorded in minutes and seconds. The instruments were examined after every use for deformation. The scores recorded were statistically analyzed using one-way analysis of variance and Mann-Whitney test. RESULTS: There was statistically significant difference with regard to removal of debris and smear layer at coronal, middle and apical third for LS versus PT and LS versus Ew (P < 0.01). There was no significant difference between PT and Ew. The mean preparation time for LS, PT and Ew was 1.76, 2.50 and 2.75 respectively. INTERPRETATION AND CONCLUSION: The study demonstrated that, LS instrumentation removed debris and smear layer effectively with shorter preparation time and Ew instrument showed deformation.