Root Dentin Surface Research Articles

Comparative evaluation of wettability of AH plus, Ceraseal and Guttaflow bioseal root canal sealers on root canal dentin: An in vitro study

Abstract Context: Effective root canal treatment relies on the ability of sealers to wet and penetrate the root canal system, ensuring a tight seal and preventing bacterial leakage. The current study investigates the wetting ability of newer root canal sealers by evaluating their contact angle. Aim: The objective of the present study was to evaluate and compare the wetting behavior of Guttaflow bioseal, Ceraseal, and AH plus root canal sealers. Materials and Methods: Decoronation and apical third resections of thirty extracted singlerooted human mandibular premolars were done. The roots were then split longitudinally into two halves buccolingually. The root dentin surfaces were treated using 10 mL 3% sodium hypochlorite for 5 min, 10 mL of 17% ethylenediaminetetraacetic acid for 5 min, and 2% chlorhexidine for 10 min. Then, these sixty dentin bars were randomly divided into three groups (n = 20): Group 1 – AH Plus, Group 2 – Ceraseal, and Group 3 – Guttaflow bioseal. The controlled volume of 0.1 mL sealer has been dispensed onto the dentin specimen using a micropipette. The contact angle of a drop of sealer was measured after 5 min using Ossila goniometer. Statistical Analysis Used: The data were analyzed using one-way analysis of variance and Tukey post hoc tests. The statistical significance was at P < 0.05. Results: The mean contact angle values for AH Plus sealer were lower when compared to the other two sealer groups which is statistically highly significant. Conclusions: AH Plus showed lesser contact angle thereby better wettability than Ceraseal and Guttaflow bioseal on the root canal dentin surface.

The effect of laser therapy for the treatment of dentin hypersensitivity on surface roughness and bacterial adhesion

The aim of the study was to measure the degree of dentine surface roughness caused by five distinct lasers used to treat dentine hypersensitivity, as well as to evaluate the subsequent bacterial colonization on these irradiated surfaces. Sixty human maxillary premolar teeth without caries or restoration which were extracted for periodontal reasons were used in this study. Five different types of lasers were applied to the root dentin surface. Tested samples were divided into six groups of 10 samples each; control, diode (810 nm), diode (980 nm), Nd: YAG, Er: YAG, and Er, Cr: YSGG laser groups. The arithmetic mean of the surface roughness values (Ra) and the average roughness over a measurement area (Sa) were measured pre- and post-application using any of the laser types. Swab samples were then collected from the dentin surface. Following a 24-hour incubation period at 37 °C, the colony forming units were counted using a stereoscope. The results demonstrated a statistically significant difference in the surface roughness values pre- and post-application (Ra and Sa, respectively) in the Er, Cr: YSGG laser group (p = 0.037,p = 0.007). No significant difference was observed in the other groups (p > 0.05). There was no statistically significant difference in the number of bacterial colonies observed between the test and control groups. Diode and Nd: YAG lasers showed either a decrease or no change in surface roughness; however, the hard tissue lasers (Er: YAG, Er, Cr: YSGG) showed an increase. The Er: YAG and Nd: YAG laser groups exhibited decreased bacterial adhesion compared to the other groups.

In Vitro Inhibitory Effect of Silver Diamine Fluoride Combined with Potassium Iodide against Mixed-Species Biofilm Formation on Human Root Dentin.

Applying a saturated potassium iodide (KI) solution immediately after silver diamine fluoride (SDF) application may affect the inhibitory effects of SDF on biofilm formation. This study compared the efficacy of 38% SDF with and without KI on preventing mixed-species biofilm formation on human root dentin surfaces and assessed ion incorporation into root dentin. The biofilms, composed of Streptococcus mutans, Lactobacillus rhamnosus, and Actinomyces naeslundii, were grown on specimen surfaces treated with either SDF or SDF + KI. After 24 h, the biofilms were evaluated using scanning electron microscopy, live/dead staining, adenosine triphosphate (ATP) assays, colony-forming unit (CFU) counts, and quantitative polymerase chain reaction. A Mann-Whitney U test was used to compare the results between the groups. Ion incorporation was assessed using an electron probe microanalyzer. The relative ATP content in the SDF + KI group was significantly higher than that in the SDF group (p < 0.05). However, biofilm morphology and the logarithmic reduction in CFUs and bacterial DNA were comparable across the groups. The SDF + KI treatment resulted in less silver and fluoride ion incorporation than that yielded by SDF alone. The inhibitory effects of SDF and SDF + KI on mixed-species biofilm formation were almost equivalent, although KI application affected the ion incorporation.

Evaluation of surface tensions and root-dentin surface contact angles of different endodontic irrigation solutions

BackgroundSurface tension and contact angle properties, which play a crucial role in determining the effectiveness of irrigation solutions in penetrating dentin surfaces and dentin tubules, are highly important for the development of new irrigation solutions and their preferences. The aim of the current study was to compare the surface tension and contact angle properties of different irrigation solutions used in endodontics, both on the dentin surface and within dentin tubules.MethodsIn this study, the contact angles and surface tensions of 5.25% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA), 2% chlorhexidine (CHX), 5% boric acid (BA), 0.02% hypochlorous acid (HOCl), 0.2% chlorine dioxide (ClO2), Biopure MTAD, QMix solutions, and distilled water (control group) were measured. Measurements were conducted using a goniometer device (Attension Theta Lite Tensiometer, Biolin Scientific, USA), employing the sessile drop method for contact angle measurements on pre-prepared dentin surfaces, and the pendant drop method for surface tension.ResultsContact angle measurements revealed no statistically significant differences between the contact angle values of MTAD, ClO2, and CHX or between NaOCl, QMix, BA, and HOCl (p > 0.05). However, EDTA exhibited a significantly greater contact angle than did MTAD, ClO2, CHX, NaOCl, QMix, BA, and HOCl (p < 0.05). Furthermore, the contact angle of dentin with distilled water was greater than that with all other solutions tested (p < 0.05). Surface tension measurements revealed that the surface tension values of QMix and MTAD were statistically similar (p > 0.05). CHX exhibited lower surface tension than distilled water and HOCl (p < 0.05), and it also had lower surface tension than ClO2, NaOCl, and BA (p < 0.05). Additionally, the surface tension of the samples treated with EDTA was greater than that of all other solutions tested (p < 0.05).ConclusionThe direct linear relationship between the surface tension of liquids and contact angles on different surfaces may not always hold true, and these values should be considered independently for each solution on various surfaces. Considering the contact angles and surface tension properties of irrigation solutions with root canal dentin, it can be suggested for clinical use that ClO2 could be recommended over NaOCl, and similarly, BA could be recommended over EDTA.

Impact of air‐polishing with erythritol on exposed root dentin: A randomized clinical trial

AbstractIntroductionThe effects of air‐polishing on exposed root dentin surfaces are largely unknown, as there are only few studies which show heterogeneous results. Thus, this study was to investigate roughness changes of exposed dentin surfaces after air‐polishing and the influence of subsequent polishing with cup and paste.MethodsTotally 54 teeth with exposed root dentin surfaces were treated using a split‐mouth design by either air‐polishing with erythritol and a rubber cup with polishing paste on the test side, or rubber cup and paste alone. Teeth were finally cleaned using a sonic tooth brush. Impressions were taken at relevant time points and replicated using epoxy resin. The resulting casts were profilometrically analysed to obtain the average surface roughness (sRa) and maximum peak‐to‐valley height (sRz), which are given as the mean ± standard deviation in μm.ResultsAfter air‐polishing, in comparison to the baseline, there was a slight but significant increase in sRa (0.168 ± 0.143, p &lt; 0.001), but sRz did not change (−0.471 ± 4.857, p = 0.936). Subsequent polishing with cup and paste and cleaning with a sonic toothbrush did not reduce the surface roughness (sonic toothbrush‐air‐polishing, sRa −0.044 ± 0.081, p = 0.218; sRz −0.551 ± 3.563, p = 0.903).ConclusionThe use of erythritol led to a slight increase in the roughness of the dentin surface, which was not reduced by polishing with a cup and paste. Polishing paste did not seem to conceal surface irregularities.

Topography of root-end surface after freehand and three-dimensional-guided apicoectomy procedure: A scanning electron microscope study.

Dentinal microcracks formed during apical resection may lead to increased susceptibility to root fracture and improper sealing of apical preparation that may negatively influence the outcome of endodontic microsurgery. This study was performed to analyze the root-end surface for dentinal microcracks using a scanning electron microscope (SEM) after resection with high-speed bur and trephine drill. Thirty extracted single-rooted maxillary premolar teeth were selected and randomly distributed into two groups (n = 15). Working length was established using a #15 K-type file. Canals were prepared with a rotary Ni-Ti system to size 30/0.06 using endomotor, irrigated with 3% sodium hypochlorite, dried with paper points, and obturated with gutta-percha cones using a single-cone technique. All samples were mounted on preformed molds and poured using a mixture of sawdust and gypsum. In Group A; tungsten carbide bur was used to perform a freehand apicoectomy. In Group B; a trephine drill was used with a three-dimensional guide to perform 3 mm of root resection. Apicoectomy was performed in both groups under a dental operating microscope. Resected root ends were inspected for microcracks using SEM. The Shapiro-Wilk and Mann-Whitney U-test were used for statistical analysis. Microcracks were observed in all samples in both study groups. Trephine drill produced more microcracks on the resected root surface compared to the use of high-speed tungsten carbide bur with a statistically significant difference (P < 0.05). The trephine drill used during targeted endodontic microsurgery produced more microcracks on the resected root dentine surface compared to the high-speed tungsten carbide bur used during freehand apicoectomy.

Accumulation and removal of Streptococcus mutans biofilm on enamel and root surfaces in vitro.

This study aimed to quantitatively investigate the accumulation of Streptococcus mutans biofilm on enamel and root surfaces and assess the amount of biofilm removal using (1) experimental toothpaste and (2) water, in a closed system of flow chamber. Eight sound premolars were embedded in epoxy resin and polished with silicon carbide grinding papers to display enamel and root surfaces. To mimic biofilm, cultures of Streptococcus mutans were prepared and grown on the tooth surfaces over night before they were exposed to either 2 liters of Milli Q water or 2 liters of 40% experimental toothpaste in the flow chamber. The amount of biofilm was measured and quantified in Fluorescence microscopy. Mean fluorescence values were recorded and analysed using Microsoft® Excel® (MS Excel 2016). The ability to grow biofilm was equally present at both the enamel and root surfaces. The use of water and 40% experimental toothpaste showed a significant reduction of areas covered with biofilm on both enamel and root dentin in comparison to untreated surfaces (p < 0.01). Significantly more biofilm was removed from enamel compared to root surfaces when treated with either water and toothpaste (p < 0.01). Slightly less biofilm was removed by the use of water compared to toothpaste on both enamel and root dentin surfaces, although the differences were not statistically significant. The results indicate that less biofilm is removed from the root surfaces than enamel by the use of water and 40% experimental toothpaste in flow chamber. Assessing oral biofilm accumulation and monitoring biofilm formation on enamel and root dentin surfaces give oral health professionals important directions that could strenghten the significance of dental caries prevention. Improving older individuals' oral hygiene practices should therefore be considered an important measure to prevent root caries.

Effect of Periodontal Instrumentation on Tooth Structure Exposure to Ionizing Radiation: In Vitro Study.

This study aimed to evaluate the effects of different scaling protocols on the morphology and roughness of the root dentin substrate exposure to ionizing radiation. One hundred and thirty extracted bovine incisors were randomly divided into two groups (n=65): non-irradiated (NIR) and irradiated (IR). Each group was initially subdivided into three subgroups according to the type of non-surgical periodontal protocol: NIT: no instrumentation; HS: hand scaling with 15 apical-coronal instrument movements; US: ultrasonic scaling with 15 apical-coronal cycles. Subsequently, all samples were subjected to the prophylaxis protocol, being subdivided into the following groups: NIT/PP: prophylaxis with a fine prophylactic paste using a rubber cup for 15 seconds; HS/PP: Hand scaling followed by the prophylaxis protocol; US/PP: Ultrasonic scaling followed by the prophylaxis protocol. The roughness of the root dentin surface was measured with a profilometer (Ra/Rz - μm), and the morphology of the dentin surfaces was analyzed using scanning electron microscopy (SEM). The analyses were conducted before and after the prophylaxis protocol. In the absence of prophylaxis, the roughest surfaces were observed after ultrasonic instrumentation followed by hand instrumentation for both IR and NIR groups. No difference in Ra and RZ values between HS/PP and US/PP was observed for both substrates. For the IR group, the prophylaxis resulted in similar Ra and RZ values for both instrumentation groups in comparison to no instrumentation. Ordinal logistic regression showed that both HS and US resulted in higher scores than NIT, irrespective of IR presence. In conclusion, the IR showed a rougher root surface for both HS and US in comparison to NIR. However, the prophylaxis procedure significantly reduced the roughness of root surfaces after both instrumentation procedures.

Comparative Evaluation of Microhardness, Smear Layer Removal Efficacy and Depth of Penetration Using Punica granatum, Emblica officinalis and Sodium Hypochlorite As Endodontic Irrigants: An In Vitro Study.

Introduction Root canal morphology tends to be complicated by natureand dealing with this intricacy can be challenging because it makes it difficult to completely disinfect the root canal space.The success of root canal therapy is also determined by the biomechanical preparation of the canal with the application of instruments and irrigating solutions.Due to the fact that the root dentin surface continues to interact with the irrigating solution during preparation, it's critical to evaluate the mechanical characteristics and smear layer removal. Though sodium hypochlorite (NaOCl) is the most commonly used irrigant due to its tissue-dissolving abilities, it has certain drawbacks which include the inability to remove the smear layer and also affects the mechanical properties of root dentin. To overcome these limitations, a variety of herbal substitutes likePunica granatumand Emblica officinaliswhich possess anti-bacterial and anti-fungal properties can be used as endodontic irrigants.Several studies on the anti-bacterial properties of natural irrigants of pomegranateand amla were reported. However, the mechanical properties and smear layer removal of Punica granatum and Emblica officinalis have not been explored in the field of endodontics. Aim The main aim of this in vitro study is to compare and evaluate microhardness, smear layer removal efficacy and depth of penetration of herbal and conventional irrigants. Materials and methods Thirty-six palatal roots of maxillary molars were decoronated and instrumented up to F3. These roots were sectioned longitudinally and divided into three test groups: Group 1: 12.5% Punica granatum;Group 2: 6.25% Emblica officinalis; control: Group 3: 2.5% NaOCl. All specimens were irrigated with 5ml of each irrigant for 5 minutes. Microhardness of root dentin was measured using a Vickers diamond intender, smear layer removal using a scanning electron microscope (SEM) and depth of penetration using a stereomicroscope. The data was analyzed using one-way ANOVAand the inter-group comparison using Tukey's post hoc test. Results Statistical analysis was done using one-way analysis of variance (ANOVA) and Tukey's post hoc test using SPSSsoftware version 17.0 (SPSS Inc., Chicago ). The highest microhardness was seen in Group 1(cervical: 53.8375±1.35956, middle: 53.9875±1.01761, apical: 53.6875± 1.63133)while Group 2(cervical: 43.2750±1.73596, middle: 43.3125±1.17648, apical: 43.8000± ​​​​​​​1.32665) and Group 3 (cervical: 42.7250±​​​​​​​2.93391, middle: 41.9625±​​​​​​​1.66985, apical: 42.0250±​​​​​​​2.21085) showed significant reduction in root dentin hardness. Regardingsmear layer removalGroup 1 (1.3750±​​​​​​​0.51755), and Group 2 (1.2500±​​​​​​​0.46291) reveals greater smear removal in the middle third of the root dentin compared with Group 3 (2.3750±​​​​​​​0.51755), which showed the least smear layer removal. A greater depth of penetration was seen in Group 1 (0.5488± 0.05222) and Group 2 (0.5263±​​​​​​​0.05181)than in Group 3 (0.3087±​​​​​​​0.05743). Conclusion The present study reveals that the least reduction of microhardness was seen in Punica granatum followed by Emblica officinalis and NaOCl. The smear layer removal efficacy and depth of penetration were greater in Punica granatum and Emblica officinalis than in NaOCl. It was concluded that as these herbal irrigants are biocompatible agents, they can be considered for future use in root canal treatment.

Effect of pretreatment of root dentin surface with cold atmospheric plasma on improving the bond strength of fiber post and resin cement: In vitro study.

Achieving stable adhesion between fiber post and interradicular dentin is a challenging process in the restoration of endodontically treated teeth. This study was conducted to investigate the effect of surface pretreatment with cold atmospheric plasma (CAP) on improving the bond strength between them. Forty-eightsingle-canal mandibular premolars were cut 1 mm above the cementoenamel junctionto keep the root length of 14 mm or more. After endodontic treatment and preparation of the post space, the teeth were divided into four groups regarding the pretreatment of dentin surfaces, including normal saline, ethylenediaminetetraacetic acid (EDTA), CAP, and CAP + EDTA groups. The data were analyzed using paired and independent t-test and one-way analysis of varianceand the significance level was set at p < .05. The bond strength was significantly higher in the coronal third than in the apical third in all the groups. Moreover, the bond strength was significantly higher in the CAP + EDTA-treated group. The bond strength increased significantly in the CAP group compared to the normal saline group. In addition, the bond strength increased significantly in the CAP or EDTA groups compared to the control group. The lowest bond strength belonged to the control group (normal saline). The surface pretreatment with CAP (alone or in combination with EDTA) played a significant role in improving the bond strength of fiber post and root canal dentin.

The Roughening Effects of Er:YAG, Nd:YAG and KTP Laser Systems on Root Dentin Surface

Objectives: Present study aimed to evaluate the roughening ability of different laser systems on the middle and apical third of roots. Materials and Methods: Sixty extracted human single-rooted single canal mandibular premolar teeth were randomly assigned to 3 groups (n=20). Standardized preparation and sterilization procedures were performed. The samples were irradiated with Er:YAG, Nd:YAG, and KTP laser systems. The laser irradiations (1.5 Watt) were applied with a spiral motion, starting 1 mm short of the apex and then moving coronally for 10 sec, interleaved with 15-sec recovery intervals for each irradiation. This process was repeated twelve times. The roots that were standardized in the same length and thicknesses were divided parallel to the longitudinal axis. Then, the middle and apical 1/3 surface roughness values of each root section were measured using a profilometer and SEM analysis was performed. The data obtained were analyzed using the two-way analysis of variance (ANOVA) and Tukey post-hoc tests. Results: According to measurements obtained from middle and apical 1/3 surfaces; Although, the statistically highest roughness value was determined after Nd:YAG laser (P &amp;lt; 0.05), the statistically lowest value was detected following the Er:YAG laser irradiation (P &amp;lt; 0.05). Conclusions: In light of the present study, all laser systems caused significant roughness surface. Therefore, laser systems should be carefully applied in human root canals.

Fluoride Retention in Root Dentin following Surface Coating Material Application.

This study aimed to use an in-air micro-particle-induced X-ray/gamma emission (in-air µPIXE/PIGE) system to evaluate tooth-bound fluoride (T-F) in dentin following the application of fluoride-containing tooth-coating materials. Three fluoride-containing coating materials (PRG Barrier Coat, Clinpro XT varnish, and Fuji IX EXTRA) and a control were applied to the root dentin surface of human molars (n = 6, total 48 samples). Samples were stored in a remineralizing solution (pH 7.0) for 7 or 28 days and then sectioned into two adjacent slices. One slice of each sample was immersed in 1M potassium hydroxide (KOH) solution for 24 h and rinsed with water for 5 min for the T-F analysis. The other slice did not undergo KOH treatment and was used to analyze the total fluoride content (W-F). The fluoride and calcium distributions were measured in all the slices using an in-air µPIXE/PIGE. Additionally, the amount of fluoride released from each material was measured. Clinpro XT varnish demonstrated the highest fluoride release among all the materials and tended to show high W-F and T-F and lower T-F/W-F ratios. Our study demonstrates that a high fluoride-releasing material shows high fluoride distribution into the tooth structure and low conversion from fluoride uptake by tooth-bound fluoride.

Effects of direct therapeutic radiation on pulpal surface of root dentin: an in vitro study.

The aims of the study were to analyze the effects of therapeutic radiation on human root dentin samples from the aspect of possible alterations in crystallinity, micro-morphology, and composition. Fifty-six root dentin specimens were divided into seven groups (0, 10, 20, 30, 40, 50, and 60Gy). Scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analyses were performed on pulpal surfaces of root dentin after being irradiated by 6MV photon energy. Mineral compositions, Ca/P, P/N, Ca/N ratios, and hydroxyapatite pikes were calculated. Some deuteriations on the dentin surface were observed in SEM images after 30Gy and subsequent doses. One-way ANOVA revealed that there was no significant alteration in weight percentages of C, O, Mg, Ca, P, and N between groups. Radiation did not influence stoichiometric Ca/P, Ca/N, and P/N molar ratios. XRD analysis did not show a remarkable decline in hydroxyapatite pikes by the increasing doses. Radiotherapy changes the micromorphology of circumpulpal dentin but does not affect elemental composition and crystallinity.

To evaluate and compare the effect of 17% EDTA, 10% citric acid, 7% maleic acid on the dentinal tubule penetration depth of bio ceramic root canal sealer using confocal laser scanning microscopy: an in vitro study.

Background: The main factors that affect the success of an endodontic infection are effective cleaning and shaping of the root canal system including complete disinfection by using chemical irrigating solutions and obturation with an endodontic sealer to provide a fluid-tight seal. Using rotary and hand instruments for shaping and cleaning the root canal along with irrigants produces a smear layer on the surface of root dentin affecting the penetration of the endodontic sealer into the dentinal tubules. This smear is difficult to remove with the use of only endodontic irrigants, hence, chelating agents were introduced in adjunct with irrigating solutions for irrigation protocol for effective removal of smear layer which effect the penetration of endodontic sealers into the dentinal tubules. Methods: 32 mandibular premolar teeth were used. The biomechanical preparation was done till Protaper F3 size. Irrigation was done with 2.5 mL sodium hypochlorite (NaOCl) solution after each instrumentation change for 1 min. Samples were then divided into 4 groups according to the irrigating solution used as the final rinse used with passive ultrasonic agitation. The groups were: Group I: 5 ml of saline, Group II: 5ml of 17% ethylenediaminetetraacetic acid, Group III: 5 ml of 10% citric acid, Group IV: 5 ml of 7% maleic acid each for one minute. All the canals were obturated with BioRoot tmRCS with gutta-percha using the ultrasonic condensation technique. For staining the samples for Confocal LASER microscopy, BioRoot tmRCS was mixed with Rhodamine B dye. Results: The maximum penetration of bio-ceramic sealer was observed in the coronal region. At the apical third, the maximum sealer penetration was seen with 7% maleic acid. Conclusions: Maximum sealer penetration was seen in the coronal section followed by the middle and apical section. Maximum sealer penetration was seen with 7 % maleic acid at the apical third.

Effect of Chloroform Application on Roughness and Wettability of the Root Canal Walls in Endodontic Retreatment.

The success of root canal therapy depends on root canal irrigation, disinfection, and sealing of root canal. Wettability and roughness of root dentine surface are important factors in root canal disinfection and sealing. This study aimed to assess the effect of chloroform application on roughness and wettability of the root canal walls in endodontic retreatment. This in vitro experimental study evaluated 70 sound extracted human anterior teeth. The specimens were then randomly assigned to 7 groups as follows: Chloroform (group 1), 1g gutta percha+chloroform (group 2), 2g gutta percha+ chloroform (group 3), 1g gutta percha+ 1g sealer+ chloroform (group 4), 2g gutta perch+ 2g sealer+chloroform (group 5), 1g sealer + chloroform (group 6) and 2g sealer + chloroform (group 7). One drop of distilled water was placed on each tooth to measure the contact angle and wettability. Photographs were obtained of an area measuring 50×50 µm2 in three directions under an atomic force microscope to measure the roughness. The tooth blocks were exposed to the abovementioned mixtures for 10 min, and then rinsed with saline. The roughness and wettability of each sample were measured before and after treatment. Data was analyzed using one-way ANOVA and Tukey's test. The roughness of all groups significantly decreased following treatment, except for groups 1 and 4. The contact angle increased in all groups after treatment (except for the chloroform group), which indicated decreased wettability. The roughness and the contact angle have shown no correlation. Application of chloroform for removal of gutta-percha and sealer in endodontic retreatment decreases the roughness and wettability of dentine.

Hydrogel Swelling-Mediated Strain Induces Cell Alignment at Dentin Interfaces.

Cell and tissue alignment is a defining feature of periodontal tissues. Therefore, the development of scaffolds that can guide alignment of periodontal ligament cells (PDLCs) relative to tooth root (dentin) surfaces is highly relevant for periodontal tissue engineering. To control PDLC alignment adjacent to the dentin surface, poly(ethylene glycol) (PEG)-based hydrogels were explored as a highly tunable matrix for encapsulating cells and directing their activity. Specifically, a composite system consisting of dentin blocks, PEG hydrogels, and PDLCs was created to control PDLC alignment through hydrogel swelling. PDLCs in composites with minimal hydrogel swelling showed random alignment adjacent to dentin blocks. In direct contrast, the presence of hydrogel swelling resulted in PDLC alignment perpendicular to the dentin surface, with the degree and extension of alignment increasing as a function of swelling. Replicating this phenomenon with different molds, block materials, and cells, together with predictive modeling, indicated that PDLC alignment was primarily a biomechanical response to swelling-mediated strain. Altogether, this study describes a novel method for inducing cell alignment adjacent to stiff surfaces through applied strain and provides a model for the study and engineering of periodontal and other aligned tissues.

Vertical root fracture resistance and crack formation of root canal-treated teeth restored with different post-luting systems

The aim was to investigate the vertical root fracture (VRF) resistance and crack formation of root canal-treated teeth restored with different post-luting systems. Human maxillary lateral incisors of similar size were decoronated, assigned to five groups (n = 18, power = 0.9) and embedded in acrylic blocks with artificial periodontal ligament. After root canal filling, post spaces were prepared to place coated fiber-reinforced composite (FRC) or sandblasted titanium (Ti) posts of the same shape and size. Half of the posts were zinc phosphate cemented (C), while the other half was adhesively luted (A). Untreated teeth served as control. After thermal cycling and staircase loading in a chewing simulator, the crack formation on the root dentin surface was microscopically examined and classified as no defect, craze line, vertical crack, and horizontal crack. Subsequently, the samples were loaded until root fracture. Data were analyzed by one-way ANOVA, Tukey’s test, and Fisher’s exact test. All samples survived the chewing simulation without VRF, but crack formation was significantly different between the groups (P = 0.009). The control showed significantly fewer defects than FRC/C, Ti/C, and Ti/A (P = 0.001, P = 0.008, P = 0.008, respectively). FRC/C showed the highest incidence of vertical cracks. FRC/A had the lowest incidence of defects. There was no significant difference in VRF resistance between the groups (P = 0.265). Adhesively luted FRC posts did not increase VRF resistance but reduced the risk of defects. Most defects were craze lines and vertical root cracks.

Root Dentin Surface Roughness and Microhardness Influenced by Different Irrigation Regimens

Еndodontic irrigants could alter the mechanical properties of root canal dentin. The aim of the current study was tо compare the effect of three irrigation protocols on root canal dentin microhardness and roughness with respect to their concentration and additional ultrasonic activation for the same treatment period. Forty single-rooted, intact upper incisors were decoronated and sectioned longitudinally in buccolingual direction. The surfaces of all eighty samples were polished and randomly allocated into four equal groups (n=20): Group 1: Control group (distilled water); Group 2: 2% NaOCl/2 min followed by 17% EDTA/2 min; Group 3: 2% NaOCl/2 min followed by 17% EDTA/2 min, both ultrasonically activated Group 4: 5.25% NaOCl/2 min followed by 17% EDTA/2 min. Root dentin microhardness was significantly lowered by all of the irrigants regardless of their concentration and/or additional agitation (p&lt;0.05). The surface of root canal dentin was roughned to the greatest extent by the ultrasonically activated irrigation solutions (p&lt;0.001). The ultrasonic activation of the disinfection solutions significantly altered the biomechanical properties of dentin.

Atomic force microscopy study on the effect of different irrigation regimens on the surface roughness of human root canal dentin.

Endodontic irrigants could alter the mechanical properties of root canal dentin, such as its roughness. To compare the effect of various irrigation protocols on root canal dentin roughness with respect to their application time, concentration, and additional ultrasonic activation. Forty single-rooted, non-endodontically treated upper incisors were decoronated and further sectioned longitudinally in a buccolingual direction. The surfaces of all eighty samples were polished and randomly segregated to eight equal groups (n = 10): Group A: 2% NaOCl/2 min followed by 17% EDTA/2 min; Group B: 2% NaOCl/5 min followed by 17% EDTA/5 min; Group C: 5.25% NaOCl/2 min followed by 17% EDTA/2 min; Group D: 5.25% NaOCl/5 min followed by 17% EDTA/5 min; Group E: 2% NaOCl solution, ultrasonically activated for 2 min; Group F: 5.25% NaOCl, ultrasonically activated for 2 min; Group G: 2% NaOCl/2 min followed by 17% EDTA/2 min, both ultrasonically activated; Group H: Control group (distilled water). All irrigation regimens increased root dentin surface roughness in comparison with the control group. The analysis of the values revealed significant differences between the arithmetical average roughness values (Ra) in the groups (p < 0.001). A statistically significant increase in the Ra parameter was observed in groups E, F, G, and D. The irrigation protocol in Group A showed a significantly smoother dentin surface than those with the ultrasonic activation. All tested irrigants increased root canal dentin roughness and the effect was time and concentration-dependent. The ultrasonic activation of the disinfection solutions roughened the root dentin surface significantly.

Effect of mechanical cleaning protocols in the fiber post space on the adhesive interface between universal adhesive and root dentin.

The aim of this study was to evaluate the effects of cleaning protocols on the presence of residues, open dentinal tubules, and bond strength of a self-etch adhesive plus a dual-cure resin cement to dentin in the fiber-post space. The methods for cleaning utilized were conventional irrigation (CI), rotary brush with continuous rotary movement (RB), and continuous ultrasonic irrigation (CUI). Sixty bovine incisors were used for fiber-post space preparation. Thirty roots were divided into three groups (n=10) according to the cleaning protocols and submitted to scanning electron microscope to evaluate presence of residues and relative quantity of open dentinal tubules on dentin surface. Similar protocols were performed in the other thirty roots (n=10) using a self-etching adhesive system (Scotchbond Universal) and a dual-cure resin cement (Relyx Unicem 2). After 6months cervical, middle, and apical thirds sections of fiber-post space were submitted to push-out testing. To data ANOVA and Tukey's test were employed (α=5%). RB and CUI showed the lowest presence of residues on dentin surface (p=.015) and the highest bond strength values (p < .001), regardless of the dentin third. CUI presented the highest quantity of open dentinal tubules in middle and apical thirds (p < .001). CI presented the lowest bond strength value of resin cement, regardless of dentin third (p < .001). Mechanical cleaning protocols, such as RB and CUI, presented better surface cleaning capabilities and higher bond strength than CI with dual-cure resin cement employed. The use of a mechanical cleaning protocol seems to cause appropriate condition on the root dentin surface. Mechanical cleaning of root dentin provided greater bond strength of the self-etching system with dual resin cement. Conventional irrigation did not provide adequate root dentin cleaning. RESEARCH HIGHLIGHTS: • The use of a mechanical cleaning protocol seems to cause appropriate condition on the root dentin surface. • Mechanical cleaning of root dentin provided greater bond strength of the self-etching system with dual resin cement. • Conventional irrigation did not provide adequate root dentin cleaning.