Effect of final irrigation protocols on microhardness and erosion of root canal dentin

The aim of this study was to evaluate the effect of final irrigation protocols (17% EDTA, BioPure MTAD, SmearClear, and QMiX) on microhardness and erosion of root canal dentin. Fifty roots were sectioned transversely at the cement–enamel junction and each root was sectioned horizontally into 4‐mm‐thick slices. The samples were divided into five groups (n = 10) according to the final irrigation protocol: G1: distilled water (control group); G2: 17% EDTA; G3: BioPure MTAD; G4: SmearClear; and G5: QMiX. The dentin microhardness was then measured with a load of 25 g for 10 s. Initially, the reference microhardness values were obtained for the samples without any etching. The same samples were then submitted to the final irrigation protocols. A new measure was realized and the difference between before and after the procedures was the dentin microhardness reduction. In sequence, the specimens were submitted to SEM analysis to verify the dentinal erosion. The Kruskal Wallis and Dunn tests (α = 5%) were used to compare the results. The dentin microhardness decreased for all final irrigation protocols. There was no significant difference between groups 2, 3, 4, and 5 (P > 0.05), but this groups presented significant dentin microhardness reduction than G1 (P < 0.05). In G2, occurred the highest incidence of dentinal erosion (P < 0.05). 17% EDTA, BioPure MTAD, SmearClear, and QMiX promoted significant dentin microhardness reduction. Dentinal tubules erosion was promoted by 17% EDTA. Microsc. Res. Tech., 76:1079–1083, 2013. © 2013 Wiley Periodicals, Inc.     

Thermal effects and morphological aspects of human dentin surface irradiated with different frequencies of Er:YAG laser

This study reports the effects on micromorphology and temperature rise in human dentin using different frequencies of Er:YAG laser. Sixty human dentin fragments were randomly assigned into two groups (n = 30): carious or sound dentin. Both groups were divided into three subgroups (n = 10), according to the Er:YAG laser frequency used: 4, 6, or 10 Hz (energy: 200 mJ; irradiation distance: 12 mm; and irradiation time: 20 s). A thermocouple adapted to the tooth fragment recorded the initial temperature value (°C); then, the temperature was measured after the end of the irradiation (20 s). Morphological analysis was performed using images obtained with scanning electron microscope. There was no difference between the temperatures obtained with 4 and 6 Hz; the highest temperatures were achieved with 10 Hz. No difference was observed between carious and sound dentin. Morphological analyses revealed that all frequencies promoted irregular surface in sound dentin, being observed more selectively ablation especially in intertubular dentin with tubule protrusion. The caries dentin presented flat surface for all frequencies used. Both substrates revealed absence of any signs of thermal damage. It may be concluded that the parameters used in this study are capable to remove caries lesion, having acceptable limits of temperature rise and no significant morphological alterations on dentin surface. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Micro‐shear bond strength of adhesives with different degrees of acidity: Effect on sound and artificially hypermineralized dentin

This study evaluates the bond strength of four self‐etching adhesive systems with different acidity levels in normal and artificially hypermineralized dentin substrate. Healthy human molars were divided into groups: normal dentin—N (n = 36) and artificially hypermineralized dentin—H (n = 36). Self‐etching adhesive systems Clearfil S³ Bond (n = 9), Optibond All in One (n = 9), Clearfil SE Bond (n = 9), and Adhese (n = 9) were used for both the N and H groups. Transparent cylindrical matrices were positioned on the treated dentin surfaces, filled with composite resin, and light‐cured for 40 s. After the transparent cylindrical matrices were removed, the specimens were stored for 24 hr in a humid environment at 37°C and were subjected to a micro‐shear bond strength test. For each group, a specimen was prepared and evaluated in scanning electron microscope for adhesive interface observation. Normality was confirmed and the two‐way analysis of variance and Games–Howell post‐tests were conducted (α = .05). The data demonstrated an interaction between the adhesive system and type of dentin substrate (p < .01). For normal dentin, all adhesive systems assessed were adequate; however, in the hypermineralized dentin, the Clearfil SE Bond two‐step self‐etching adhesive system with mild pH presented the highest immediate bond strength. There was a predominance of adhesive failures for all adhesive systems in the different dentin substrates evaluated. It was concluded that the self‐etching adhesive systems evaluated were efficient for both substrates, and for the hypermineralized dentin, the Clearfil SE Bond presented a higher bond strength value.     

Stress and strain distribution in demineralized enamel: A micro‐CT based finite element study

Physiological oral mechanical forces may play a role on the progression of enamel carious lesions to cavitation. Thus, the aim of this study was to describe, by 3D finite element analysis, stress, and strain patterns in sound and carious enamel after a simulated occlusal load. Micro‐CT based models were created and meshed with tetrahedral elements (based on an extracted third molar), namely: a sound (ST) and a carious tooth (CT). For the CT, enamel material properties were assigned according to the micro‐CT gray values. Below the threshold corresponding to the enamel lesion (2.5 g/cm³) lower and isotropic elastic modulus was assigned (E = 18 GPa against E₁ = 80 GPa, E₂ = E₃ = 20 GPa for sound enamel). Both models were imported into a FE solver where boundary conditions were assigned and a pressure load (500 MPa) was applied at the occlusal surface. A linear static analysis was performed, considering anisotropy in sound enamel. ST showed a more efficient transfer of maximum principal stress from enamel to the dentin layer, while for the CT, enamel layer was subjected to higher and concentrated loads. Maximum principal strain distributions were seen at the carious enamel surface, especially at the central fossa, correlating to the enamel cavity seen at the original micro‐CT model. It is possible to conclude that demineralized enamel compromises appropriate stress transfer from enamel to dentin, contributing to the odds of fracture and cavitation. Enamel fracture over a dentin lesion may happen as one of the normal pathways to caries progression and may act as a confounding factor during clinical diagnostic decisions. Microsc. Res. Tech. 78:865–872, 2015. © 2015 Wiley Periodicals, Inc.     

Shear bond strength and ultrastructural interface analysis of different adhesive systems to bleached dentin

Background: It remains unclear as to whether or not dental bleaching affects the bond strength of dentin/resin restoration. Purpose: To evaluated the bond strength of adhesive systems to dentin submitted to bleaching with 38% hydrogen peroxide (HP) activated by LED‐laser and to assess the adhesive/dentin interfaces by means of SEM. Study design: Sixty fragments of dentin (25 mm²) were included and divided into two groups: bleached and unbleached. HP was applied for 20 s and photoactivated for 45 s. Groups were subdivided according to the adhesive systems (n = 10): (1) two‐steps conventional system (Adper Single Bond), (2) two‐steps self‐etching system (Clearfil standard error (SE) Bond), and (3) one‐step self‐etching system (Prompt L‐Pop). The specimens received the Z250 resin and, after 24 h, were submitted to the bond strength test. Additional 30 dentin fragments (n = 5) received the same surface treatments and were prepared for SEM. Data were analyzed by ANOVA and Tukey's test (α = 0.05). Results: There was significant strength reduction in bleached group when compared to unbleached group (P < 0.05). Higher bond strength was observed for Prompt. Single Bond and Clearfil presented the smallest values when used in bleached dentin. SEM analysis of the unbleached specimens revealed long tags and uniform hybrid layer for all adhesives. In bleached dentin, Single Bond provided open tubules and with few tags, Clearfil determined the absence of tags and hybrid layer, and Prompt promoted a regular hybrid layer with some tags. Conclusions: Prompt promoted higher shear bond strength, regardless of the bleaching treatment and allowed the formation of a regular and fine hybrid layer with less deep tags, when compared to Single Bond and Clearfil. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.     

Efficacy of different irrigant protocols and application systems on sealer penetration using a stepwise CLSM analysis

This study compared several irrigation protocols and application systems for sealer penetration into dentinal tubules. Single‐rooted‐human teeth were divided into 5 experimental groups (n = 15) and a control group (n = 5), according to final irrigation protocols: standard needle irrigation (SNI); Vibringe; Vibringe + NaviTip FX (Vibringe NFX); Endo Spray (ES); and passive‐ultrasonic‐irrigation (PUI). Following obturation of the root canals, the percentage of the sealer penetration was measured at different depths using stepwise CLSM analysis. The sealer penetration in the experimental groups was significantly higher than the control group at all levels (p < .05). No significant differences were observed between Vibringe and SNI or Vibringe NFX, ES, and PUI at all depths (p > .05). The Vibringe NFX, ES, and PUI groups allowed deeper sealer penetration than SNI at 100, 250, and 500 μm levels (p < .05). The irrigant activation, the needle design, and the application form (syringe or spray) may impact the quality of the seal that is achieved with root canal filling.     

Effect of laser preparation on adhesion of a self‐adhesive flowable composite resin to primary teeth

The aim of the study was to evaluate the adhesion of a self‐adhering flowable composite resin to primary tooth enamel and dentin after silicon carbide paper (SiC) and laser pretreatment. Adhesive properties were evaluated as shear bond strength (SBS) and scanning electron microscopic (SEM) characteristics. A total 120 primary canine teeth were randomly divided into two groups to study enamel and dentin. Each group was divided into 6 subgroups (n = 10) according to type of surface preparation (SiC or Er:YAG laser) of enamel or dentin. Three methods were used to build cylinders of restoration on tooth surface: OptiBond All‐In‐One + Premise Flowable composite, OptiBond All‐In‐One + Vertise Flow and Vertise flow. After restoration, samples were tested for SBS and failure mode. Twenty eight samples were examined by SEM. The results of the study showed SBS of Vertise Flow was lower than others in enamel and dentin samples pretreated with SiC and in dentin samples pretreated with laser (P < 0.001). Compared to SiC pretreatment, laser pretreatment led to a significantly higher SBS with Vertise Flow on enamel (P < 0.001). Vertise Flow associated with the adhesive led to a higher SBS in enamel and dentin compared to Vertise Flow alone. Adhesive and mixed failure modes were observed more frequently in Vertise Flow groups. SEM images showed that Vertise Flow led to more irregularities on enamel and more open dentinal tubules after laser ablation compared SiC pretreatment. Microsc. Res. Tech. 79:334–341, 2016. © 2016 Wiley Periodicals, Inc.     

Penetrability of AH plus and MTA fillapex after endodontic treatment and retreatment: A confocal laser scanning microscopy study

The aim of the study was to assess the penetrability of two endodontic sealers (AH Plus and MTA Fillapex) into dentinal tubules, submitted to endodontic treatment and subsequently to endodontic retreatment. Thirty ex vivo incisors were prepared using ProTaper rotary system up to F3 instrument and divided in three groups according to the endodontic sealer used for root canal filling: AH Plus (AHP), MTA Fillapex (MTAF), and control group (CG) without using EDTA previously to the root canal filling. Rhodamine B dye (red) was incorporated to the sealers in order to provide the fluorescence which will enable confocal laser scanning microscopy (CLSM) assessment. All specimens were filled with gutta‐percha cones using the lateral compaction technique. The specimens were submitted to endodontic retreatment using ProTaper Retreatment system, re‐prepared up to F5 instruments and filled with gutta‐percha cones and the same sealer used during endodontic retreatment. Fluorescein dye (green) was incorporated to the sealer in order to distinguish from the first filling. The roots were sectioned 2 mm from the apex and assessed by CLSM. No difference was found between the two experimental groups (P > 0.05). On the other hand, in the control group the sealers were not capable to penetrate into dentinal tubules after endodontic treatment (P > 0.05). In retreatment cases, none of the sealers were able to penetrate into dentin tubules. It can be concluded that sealer penetrability is high during endodontic treatment. However, MTA Fillapex and AH Plus do not penetrate into dentinal tubules after endodontic retreatment. Microsc. Res. Tech. 77:467–471, 2014. © 2014 Wiley Periodicals, Inc.     

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.     

Effects of sodium hypochlorite as dentin deproteinizing agent and aging media on bond strength of two conventional adhesives

This study evaluated the effect of 10% sodium hypochlorite (NaOCl) as deproteinizing agent and storage media on bond strength (BS) of two etch‐and‐rinse adhesive systems to dentin. Twenty‐eight sound extracted human third molars were divided in four groups (n = 7), according to dentin treatment (conventional etching or etching followed by 10% NaOCl application) and adhesive systems (GB—Gluma 2Bond and OS—One‐Step). After dentin treatments and adhesive application, a composite block was built‐up on dentin surface and teeth were serially sectioned to obtain bonded sticks specimens. The sticks were submitted to three aging conditions: (24H) 24 hr in water (immediate), (SH) 3 hr of NaOCl accelerated‐aging or (1Y) 1 year of water storage. Afterward, submitted to microtensile bond strength test (μTBS), failure modes and adhesive interfaces analyzes. Data were analyzed by two‐way analysis of variance (ANOVA) and Tukey's test (α = .05). Dentin deproteinization before bonding significantly reduced μTBS for GB‐treated group (p < .05), regardless the aging conditions. Water storage for 1 year (1Y) and NaOCl accelerated‐aging (SH) decreased μTBS for both adhesives. Yet, the groups stored in NaOCl (SH) exhibited the lowest BS results (p < .05). Bond strength of deproteinized dentin was dependent on the adhesive system composition and NaOCl accelerated‐aging promoted decreased bond strength and further degradation than water storage for 1 year.     

Effects of chemical agents on physical properties and structure of primary pulp chamber dentin

This study evaluated the effects of chemical agents on the physical properties and structure of primary pulp chamber dentin using surface roughness, microhardness tests, and scanning electron microscopy (SEM). Twenty‐five primary teeth were sectioned exposing the pulp chamber and were divided into five groups (n = 5): NT, no treatment; SH1, 1% sodium hypochlorite (NaOCl); SH1U, 1% NaOCl + Endo‐PTC^®; SH1E, 1% NaOCl + 17% EDTA; and E, 17% EDTA. After dentin treatment, the specimens were submitted to roughness, microhardness testing, and SEM analysis. Roughness and microhardness data were submitted to one‐way ANOVA and Tukey's test (P < 0.05). The SH1E group showed the highest roughness, followed by the E group (P < 0.05) when compared with the NT, SH1, and SH1U groups. Microhardness values of SH1 and SH1U showed no significant difference as compared to the NT (control) group (P > 0.05). Microhardness values could not be obtained in the EDTA groups (SH1E and E). The presence of intertubular dentin with opened dentin tubules was observed in the NT, SH1, and SH1U groups. SH1E showed eroded and disorganized dentin with few opened tubules and the intertubular/peritubular dentin was partially removed. Considering the physical and structural approaches and the chemical agents studied, it can be concluded that NaOCl and NaOCl associated with Endo‐PTC^® were the agents that promoted the smallest changes in surface roughness, microhardness, and structure of the pulp chamber dentin of primary teeth. Microsc. Res. Tech. 77:52–56, 2014. © 2013 Wiley Periodicals, Inc.     

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/cm², 150 mJ–29.8 J/cm², 100 mJ–35.3 J/cm², 150 mJ–53.0 J/cm², 200 mJ–70.7 J/cm², and 250 mJ–88.5 J/cm², 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. Microsc. Res. Tech. 78:1019–1025, 2015. © 2015 Wiley Periodicals, Inc.     

The use of an Er:YAG laser to remove demineralized dentin and its influence on dentin permeability

The purpose of this study was to analyze, correlate, and compare the demineralization and permeability of dentin remaining after caries removal with either an Er:YAG laser, a bur, or a curette. Thirty human dentin fragments were immersed in a demineralizing solution for 20 days and were randomly divided into three groups (n = 10) for the removal of the demineralized lesion. The groups were G1—Er:YAG laser (200 mJ/6 Hz; noncontact at 12 mm; spot: 0.63 mm), G2—Bur, and G3—Curette. The specimens were then immersed in a 10% copper sulfate solution, then in a 1% dithiooxamide alcoholic solution for 30 min and kept in ammonia vapor for 7 days. Next, the specimens were examined with optical microscopy. The amount of demineralized dentin and the level of copper ion infiltration in the dentin were quantified in μm using Axion Vision software. Data were analyzed with the Kruskal‐Wallis test (p < 0.05) and Pearson's Correlation test. The analysis revealed no significant differences between the three caries removal methods in terms of their capacity to remove demineralized tissue (G1: 10.6 μm; G2: 8.4 μm; G3: 11 μm), although the laser removal generated more tissue permeability than the others methods (G1: 17.6 μm; G2: 6.6 μm; G3: 5.5 μm). The correlation between the remaining demineralized dentin and the dentin permeability was moderate for the conventional methods and higher for the Er:YAG laser. It can therefore be concluded that the laser produced an increase in permeability that was directly proportional to the amount of demineralized tissue removal. Microsc. Res. Tech. 76:225–230, 2013. © 2012 Wiley Periodicals, Inc.     

Effect of dentin and fiber post surface treatments with fumaric acid on the bonding ability of fiber posts

This study investigated the effects of fumaric acid on push‐out bond strength when applied to dentin surfaces and fiber posts. The root canals of 60 mandibular premolar teeth were instrumented and obturated. After removing two thirds of filling material, teeth were prepared according to six randomized groups (n = 10/group) defined by two fiber post surface treatments (0.7% fumaric acid or 9% hydrofluoric acid) and three dentin conditioning treatments [control (no conditioning); 17% ethylenediamine tetraacetic acid (EDTA); or 0.7% fumaric acid]. After fiber post‐cementation, three 1‐mm thick discs were obtained from each tooth by transverse sectioning, and each disc underwent push‐out bond strength testing. Data were analyzed with a one‐way analyses of variance (anova ) and t tests; p < .05 was considered statistically significant. Failure modes were determined by stereomicroscopy, and the surface characteristics of dentin and fiber posts were observed by scanning electron microscopy. Push‐out bond strength was greater for the group in which the post surface treated with hydrofluoric acid and the dentin surface treated with fumaric acid than the nontreated dentin and hydrofluoric acid‐treated post group (p < .05). There were no significant differences between other comparison pairs (p > .05). A combination of fumaric acid dentin conditioning and hydrofluoric acid fiber post treatment strengthened the bonding ability of fiber posts.     

Peracetic acid as a single endodontic irrigant: effects on microhardness,roughness and erosion of root canal dentin

The aim was to assess the effects of 1% peracetic acid (PAA) as a single endodontic irrigant on microhardness, roughness, and erosion of root canal dentin, compared with 2.5% sodium hypochlorite (NaOCl) and with 2.5% NaOCl combined with 17% EDTA. Forty human, single‐rooted tooth hemisections were submitted to Knoop microhardness test, before and after the following irrigation protocols: PAA = 1% PAA; NaOCl = 2.5% NaOCl; NaOCl‐EDTA‐NaOCl = 2.5% NaOCl +17% EDTA +2.5% NaOCl; and SS = saline. Another 40 roots were instrumented, irrigated with the same protocols, and sectioned longitudinally. The roughness analysis was performed on the mesial section using a confocal laser scanning microscope, whereas erosion was analyzed on each third of the distal section, using a scanning electron microscope. The data were analyzed using ANOVA and Tukey post‐tests, and Kruskal‐Wallis and Dunn post‐tests (α = .05). The PAA and NaOCl‐EDTA‐NaOCl groups showed no significant differences (p > .05); both promoted reduction in microhardness and increase in roughness, compared with the NaOCl and SS groups (p < .05). NaOCl‐EDTA‐NaOCl promoted higher erosion in the cervical and middle thirds than the other groups (p < .05); there was no difference among PAA, NaOCl, and SS (p > .05). There was also no difference among the groups regarding the apical third (p > .05). PAA used as a single endodontic irrigant caused reduction in root canal dentin microhardness and increase in roughness in a similar way to NaOCl‐EDTA‐NaOCl; however, PAA caused less erosion than NaOCl‐EDTA‐NaOCl.     

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. Microsc. Res. Tech. 78:472–478, 2015. © 2015 Wiley Periodicals, Inc.     

Dentinal tubule penetration of endodontic sealers after nonthermal plasma treatment: A confocal laser scanning microscopy study

One of the factors affecting the success of endodontic treatment is to fill the root canal system hermetically. The aim of this in vitro study was to evaluate the effect of nonthermal plasma (NP) on dentinal tubule penetration of root canal sealers using confocal laser scanning microscopy. Forty mandibular premolar teeth were selected and the root canals were prepared with large‐Waveone‐Gold rotary‐files. Specimens were divided into four experimental groups according to sealer and NP treatment (n = 10). G1: AH‐Plus (AH) G2: nonthermal plasma application + AH‐Plus(AH‐P) G3: Endosequence‐BC(BC) G4: nonthermal plasma application + Endosequence‐BC(BC‐P). Cold lateral‐condensation technique was used for the obturation of root canals. The roots were sectioned horizontally and the sections were examined under confocal laser scanning microscopy. The maximum tubule penetration and percentage of penetration values were obtained from the microscopy images and were statistically analyzed with repeated measurements‐ANOVA and the Tukey (HSD) test (p < 0.05). The percentages of dentinal tubule penetration of the groups were not statistically different. The maximum tubule penetration of the AH‐P was statistically lower than that of the BC‐P (p < 0.05). Plasma application had no affect on the percentage of dentinal tubule penetration. Under the conditions of this in vitro Endosequence‐BC sealer showed higher maximum tubule penetration values than AH‐Plus after NP treatment. Percentage of dentinal tubule penetration values of experimental groups was similar.     

Long‐term chlorhexidine effect on bond strength to Er:YAG laser irradiated‐dentin

This study evaluates the bond strength of dentin prepared with Er:YAG laser or bur, after rewetting with chlorhexidine on long‐term artificial saliva storage and thermocycling. One hundred and twenty human third molars were sectioned in order to expose the dentin surface (n = 10). The specimens were randomly divided in 12 groups according to treatment and aging: Er:YAG laser rewetting with deionized water (LW) and 24 h storage in artificial saliva (WC); LW and 6 months of artificial saliva storage + 12.000 thermocycling (6M), LW and 12 months of artificial saliva storage + 24.000 thermocycling (12M), Er:YAG laser rewetting with 2% chlorhexidine (LC) and WC, LC and 6M, LC and 12M, bur on high‐speed turbine rewetting with deionized water (TW) and WC, TW6M, TW12M, bur on high‐speed turbine + 2% chlorhexidine (TC) and WC, TC and 6M, TC and12M. The specimens were etched with 35% phosphoric acid, washed, and dried with air. Single Bond 2 adhesive was applied and the samples were restored with a composite. Each tooth was sectioned in order to obtain 4 sticks, which were submitted to microtensile bond strength test (µTBS). The two‐way ANOVA, showed no significant differences for the interaction between the factors and for the aging factor. Tukey 5% showed that the LC group had the lowest µTBS. The rewetting with chlorhexidine negatively influenced the bond strength of the preparation with the Er:YAG laser. The artificial saliva aging and thermocycling did not interfere with dentin bond strength. Microsc. Res. Tech. 77:37–43, 2014. © 2013 Wiley Periodicals, Inc.     

Dentin bond strength and nanoleakage of the adhesive interface after intracoronal bleaching

This study evaluated dentin bond strength (BS) and nanoleakage of non‐ and pre‐etched dentin immediately (T₀,), 7 days (T₇), and 14 days (T₁₄) after bleaching. Bovine incisors (150) were selected and half of them submitted to intrapulpal dentin etching (e). Non‐ and pre‐etched dentin were subjected to the following (n = 15): no bleaching/control (C); 35% carbamide peroxide (CP); 35% hydrogen peroxide (35% HP); 25% hydrogen peroxide (25% HP); and sodium perborate (SP). Bleaching agents were applied to the pulp chamber four times within a 72‐h interval. Afterwards, pulp chamber dentin was prepared for the BS test at different evaluation times (n = 5): T₀, T₇, and T₁₄. Composite blocks were built on pulp chamber and sectioned in slices. Slices were reduced to an hour‐glass shape with a cross‐sectional area of 0.8 mm² and submitted to microtensile BS test. Two additional specimens for each group were prepared for nanoleakage evaluation by transmission electron microscopy (TEM). Results were analyzed by ANOVA (two‐way) and Dunnett's test (p < .05). BS decreased immediately after intracoronal bleaching for both sound and pre‐etched dentin (p < .05). At T₁₄, the BS of non‐etched bleached dentin increased for all groups, whereas the pre‐etched SPe group presented BS similar to the Ce. Nanoleakage within the hybrid layer was perceptible immediately after bleaching, although a decrease in nanoleakage was observed for all groups at T₁₄. Adhesive restorations should be performed 7–14 days after bleaching, according to the bleaching agent used. Intracoronal bleaching should be performed preferably with sodium perborate if previous dentin etching is applied.