Adjunctive use of different lasers Er, Cr: YSGG, femtosecond, potassium titanyl phosphate and photodynamic therapy on radicular disinfection bonded to glass fiber post.

OBJECTIVE: The aim of this study was to evaluate and compare the effect of different laser prototypes [Er, Cr: YSGG laser (ECYL), potassium titanyl phosphate laser (KTP), and Femtosecond laser (FSL)]and curcumin photosensitizer (CP) activated by Photodynamic therapy (PDT) on the bond strength of Pre-fabricated fiber reinforced composite (PFRC) post-bonded to radicular dentin. MATERIALS AND METHODS: A total of fifty mandibular single-rooted closed apex teeth were extracted carefully, assembled, and decoronated up to the cementoenamel junction. The working length of all specimens was determined by using a 10 K patency file and later, were cleaned and shaped with Protaper NiTi system using the crown down approach, dried, and obturated with gutta-percha using an AH Plus sealer. Post space was prepared by guiding peeso-reamer. Based on the method of disinfection, the samples were allocated to five groups (n=10) at random: samples in group 1: curcumin photosensitizer (CP) activated by PDT, samples in group 2 disinfected using 5.25% NaOCl+17% EDTA, samples in group 3 disinfected using 5.25% NaOCl+17% EDTA+FSL, specimens in group 4 sterilized using 5.25% NaOCl+17% EDTA+KTP and samples in group 5 cleaned with 5.25% NaOCl+17% EDTA+ECYL. The fiber post was cemented via self-etch resin cement into the post space. All specimens with posts were dissected perpendicularly into apical, middle, and coronal dentin and subjected to the universal testing machine for push-out bond strength (PBS) testing. Statistical analysis was performed using a One-Way analysis of variance and Post Hoc Tukey multiple comparison tests. RESULTS: The highest PBS was corroborated when the radicular canal was disinfected with 5.25% NaOCl +17% EDTA+ ECYL at all three root levels (coronal, middle, and apical) and the lowest was adjudicated by decontamination with CP activated by PDT at all inspected root levels. Intergroup comparison presented that specimens in group 2: 5.25% NaOCl+17% EDTA (control) and group 4: 5.25% NaOCl+17% EDTA+KTP revealed comparable PBS outcome to group 5 (p>0.05) while samples in group 3 revealed the equivalent PBS values to group 1 (p<0.05) at all three root levels. CONCLUSIONS: Er, Cr: YSGG laser and potassium titanyl phosphate laser when used in combination with the conventional canal disinfection 5.25% NaOCl and 17% EDTA demonstrated the highest push-out bond strength values at coronal, middle, and apical levels of the root.

Spectrophotometric analysis evaluating apical microleakage in retrograde filling using GIC, MTA and biodentine: an in-vitro study.

BACKGROUND: The present study compares the apical microleakage of three different root-end filling materials in which the retrograde cavity is prepared by two different burs. METHODS: Eighty extracted single rooted maxillary and mandibular premolars were taken. Root canal treatment was completed. Apical 3 mm of all the teeth were resected with diamond disk. The tooth were divided into four groups with two subgroups for each group containing 10 tooth (N = 10) as: Group IA (Negative Control and IB (Positive Control); Group IIA and IIB: Prepared with round carbide bur and round diamond bur respectively, filled with GIC; Group IIIA and IIIB: Prepared with round carbide bur and round diamond bur respectively, filled with MTA; Group IVA and IVB: Prepared with round carbide bur and round diamond bur, filled with Biodentine. After applying two coats of nail varnish leaving apical 3 mm (except for negative control group) all teeth were immersed in 2% methylene blue for 3 days and again in 65% nitric acid for next 3 days for extraction of dye. The obtained solution was then transferred to eppendorf tube and centrifuged in microcentrifuges at 14,000 revolution per minutes (RPM) for 5 min. Optical density or absorbance of the supernatant solution was measured with UV spectrophotometer at 550 nm. RESULTS: The absorbance of the supernatant solution after dye extraction is decreasing in the order of positive control> GIC > MTA > Biodentine> negative control group. The significant difference was observed between GIC and MTA (p = 0.0001) and GIC and Biodentine (p = 0.0001) with two different burs but statistically non-significant difference was observed between MTA and Biodentine with Carbide bur (p = 0.127) and Diamond bur (p = 0.496) respectively. CONCLUSIONS: Within the limitations of the present study, it can be concluded that Biodentine and MTA showed less microleakage as compared to GIC. There is no significant difference between mean microleakage of MTA and Biodentine. However, the mean OD of the Biodentine was least of all evaluated materials. Preparation of the root-end using round carbide bur as well as round diamond burs showed comparable microleakage for all three filling materials.

Effect of different laser-assisted irrigation activation techniques on apical debris extrusion.

Objective: The aim of this study was to compare apical debris extrusion when neodymium-doped yttrium aluminium garnet (Nd:YAG) lasers, erbium-doped yttrium aluminium garnet (Er:YAG) or photon-induced photoacoustic streaming (PIPS) are used for irrigation activation.Materials and methods: A total of 60 extracted human mandibular premolar teeth have similar dimensions were included and the samples were split into four groups according to the irrigation technique (n = 15): conventional needle irrigation, PIPS, Er:YAG and Nd:YAG. ProTaper Universal system up to F4 was used for root canal instrumentation. Bidistilled water was used as an irrigation solution during instrumentation and irrigation activation. Apically extruded debris was collected into preweighed Eppendorf tubes during instrumentation and irrigation activation procedures. The tubes were then kept in an incubator at 70 °C for 5 days. The initial weight of the tube was subtracted from the final weight and the result was recorded as the weight of dry extruded debris. The data were evaluated statistically using a one-way ANOVA test followed by least significant difference post hoc test (p < .05).Results: Conventional needle irrigation caused significantly less debris extrusion than laser-assisted irrigation activation groups (p < .05). Laser-assisted irrigation activation groups caused statistically similar debris extrusion (p > .05).Conclusion: Laser-assisted irrigation activation techniques caused more debris extrusion when compared to conventional needle irrigation.

Evaluation of the apical extrusion of sodium hypochlorite gel in immature permanent teeth: An in vitro study.

BACKGROUND: Sodium hypochlorite (NaOCl) gel has been suggested as a safer substitute in open apices as compared to solution, with the same antimicrobial effect. OBJECTIVES: This study aimed to compare the amount of the apical extrusion of NaOCl gel and solution in immature permanent teeth. MATERIAL AND METHODS: A crossover in vitro study was conducted at the Department of Pediatric Dentistry, Faculty of Dentistry of Damascus University, Syria. Thirty freshly extracted immature single-rooted human premolars were decoronated and the cavity was then accessed. The teeth were radiographed to determine the mesiodistal dimension of the apex. In addition, the surface area of the apical foramen was calculated with Adobe Photoshop® to evaluate the amount of extrusion from the whole surface of the apex. The teeth were divided into 2 groups according to the size of the apex: ≤2.5 mm (group A) and >2.5 mm (group B); each group was irrigated with 5 mL of NaOCl solution and 2 different commercial types of NaOCl gel for 60 s, and then the extruded irrigant was measured in a plastic vial. RESULTS: The data was analyzed using the Kruskal-Wallis analysis. Based on the observed results, a statistically significant difference was noted (p = 0) between NaOCl solution and gel when the apical diameter was ≤2.5 mm, while there was no significant difference between the 2 types of NaOCl gel. No statistically significant difference was observed (p = 0.2) between NaOCl solution and gel when the apical diameter was >2.5 mm. CONCLUSIONS: Sodium hypochlorite gel is safer than solution when irrigating immature teeth with the apical diameter ≤2.5 mm.

Cytotoxicity of intracanal dressings on apical papilla cells differ upon activation with E. faecalis LTA.

OBJECTIVE: The aim of this study was to investigate the cytotoxic effects of modified triple antibiotic paste and an experimental composition using calcium hydroxide on lipoteichoic acid (LTA)-primed apical papilla cells (APC). MATERIAL AND METHODS: Human APC were tested for in vitro cytotoxicity of modified Triple Antibiotic Paste (mTAP - Ciprofloxacin, Metronidazole and Cefaclor at 1:1:1) and of a paste of Ciprofloxacin, Metronidazole and Calcium hydroxide (CMC - 1:1:2) and modified CMC (mCMC - 2:2:1) by using MTT assay. The substances were reconstituted in DMEM at 1,000 µg/mL and » serially diluted before being kept in contact with cells for 1, 3, 5 and 7 days. Further, cells were primed with 1 µg/mL of Enterococcus faecalis LTA for 7 days prior to the viability test with 1,000 µg/mL of each substance. Statistical analysis was performed using one-way analysis of variance (ANOVA) and two-way ANOVA respectively followed by Tukey's post-test. Significance levels were set at p<0.05. RESULTS: In the first assay, the higher cytotoxic rates were reached by mTAP for all experimental periods. CMC was found toxic for APC at 5 and 7 days, whereas mCMC did not affect the cell viability. Only CMC and mCMC were able to induce some cellular proliferation. In the second assay, when considering the condition with medium only, LTA-primed cells significantly proliferated in comparison to LTA-untreated ones. At this context, mTAP and CMC showed similar cytotoxicity than the observed for LTA-untreated cells, while mCMC was shown cytotoxic at 7 days only for LTA-primed APC. Comparing the medications, mTAP was more cytotoxic than CMC and mCMC. CONCLUSION: mTAP showed higher cytotoxicity than CMC and mCMC and the effect of topic antimicrobials might differ when tested against apical papilla cells under physiological or activated conditions.

Bacterial leakage and marginal adaptation of various bioceramics as apical plug in open apex model.

AIM: The aim of the present study was to investigate bacterial leakage and marginal adaptation of bioceramic apical plugs. METHODS: Extracted human mandibular premolars were prepared to simulate open apex using No. 4 Peeso reamer in retrograde direction. In total, 150 specimens were divided into 10 groups by obturation with five bioceramics in two thicknesses. Groups 1, 3, 5, 7, and 9 were obturated with ProRootMTA, Biodentine, TotalFill BC RRM paste, TotalFill BC RRM putty, and RetroMTA at 3 mm, and groups 2, 4, 6, 8, and 10 were obturated with the same materials at 4 mm. Ten specimens in each group were evaluated for bacterial leakage of Enterococcus faecalis for 75 days. Five specimens from each group were sectioned to investigate the gap area under scanning electron microscope. RESULTS: The 3- and 4-mm Biodentine and TotalFill BC RRM putty groups and the 4-mm ProRootMTA group exhibited less bacterial leakage and lower mean percentage of gap area than those of the other groups. TotalFill BC RRM paste showed the highest leakage for both the 3- and 4-mm groups. CONCLUSION: The 3- and 4-mm Biodentine and TotalFill BC RRM putty groups and the 4-mm ProRootMTA group exhibited the best sealing ability and marginal adaptation of apical plugs.

Cytotoxicity of intracanal dressings on apical papilla cells differ upon activation with E. faecalis LTA

Abstract Objective The aim of this study was to investigate the cytotoxic effects of modified triple antibiotic paste and an experimental composition using calcium hydroxide on lipoteichoic acid (LTA)-primed apical papilla cells (APC). Material and Methods Human APC were tested for in vitro cytotoxicity of modified Triple Antibiotic Paste (mTAP - Ciprofloxacin, Metronidazole and Cefaclor at 1:1:1) and of a paste of Ciprofloxacin, Metronidazole and Calcium hydroxide (CMC - 1:1:2) and modified CMC (mCMC - 2:2:1) by using MTT assay. The substances were reconstituted in DMEM at 1,000 µg/mL and » serially diluted before being kept in contact with cells for 1, 3, 5 and 7 days. Further, cells were primed with 1 µg/mL of Enterococcus faecalis LTA for 7 days prior to the viability test with 1,000 µg/mL of each substance. Statistical analysis was performed using one-way analysis of variance (ANOVA) and two-way ANOVA respectively followed by Tukey's post-test. Significance levels were set at p<0.05. Results In the first assay, the higher cytotoxic rates were reached by mTAP for all experimental periods. CMC was found toxic for APC at 5 and 7 days, whereas mCMC did not affect the cell viability. Only CMC and mCMC were able to induce some cellular proliferation. In the second assay, when considering the condition with medium only, LTA-primed cells significantly proliferated in comparison to LTA-untreated ones. At this context, mTAP and CMC showed similar cytotoxicity than the observed for LTA-untreated cells, while mCMC was shown cytotoxic at 7 days only for LTA-primed APC. Comparing the medications, mTAP was more cytotoxic than CMC and mCMC. Conclusion mTAP showed higher cytotoxicity than CMC and mCMC and the effect of topic antimicrobials might differ when tested against apical papilla cells under physiological or activated conditions.

Characterization of the apical bridge barrier formed following amelogenin apexification.

BACKGROUND: Recombinant amelogenin protein (RAP) is reported to induce complete root apex formation in dog model when used as apexification therapy. It also induces pulp regeneration in 85% of the treated group. Thus, the aim of this study was to investigate the nature of the remaining regenerated calcified tissues of the RAP group that showed no pulp regeneration compared to the calcium hydroxide treated group (CH). METHODS: A total of 240 dogs' open apex root canals were used, after establishment of canals contamination. Canals were cleaned, irrigated, and filled with RAP as an apexification material and compared with CH. Treated teeth were assessed by H&E, trichrome staining, and/or immunohistochemistry technique, at 1, 3, and 6 months. RESULTS: A time-dependent increase in the calcified tissue barrier was observed in the apex of the RAP-treated group compared to the CH-treated group. The newly formed dentin in this RAP group was mainly tubular dentin and was functionally attached to the bone by periodontal ligament, while the CH group showed dentin-associated mineralized tissue (DAMT) associated with the newly formed apical barrier. CONCLUSIONS: Out results suggest that RAP can be used as novel apexification material, resulting in a thickening and strengthening of the canal walls, and achieving apical closure.

Light curing resin cements containing iodonium salts promote suitable apical bonding of posts to radicular dentin.

The aim of this study was to analyze the efficiency of experimental light-curing resin cements (ERCs) with a ternary photo-initiator system containing diphenyliodonium hexafluorphosphate (DPI) and different amines on retention of glass-fiber posts to dentin (GFP). ERCs formulations: a 1:1 mass ratio of 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenylpropane and triethyleneglycol dimethacrylate. Camphorquinone was used as initiator. Six experimental groups were established according to the amine used: [ethyl-4-(dimethylamino)benzoate-EDMAB or 2-(dimethylamino)ethyl methacrylate-DMAEMA] and the concentration of DPI (0, 0.5 mol%, 1 mol%). The resin cements Variolink II (dual- and light-cured versions) were used as commercial reference. Eighty recently extracted bovine incisors (n = 10) were selected for this study. The roots were prepared and the fiber posts were cemented with the resin cement specified for each experimental group. Specimens from coronal, middle, and apical thirds of the root were subjected to push-out bond strength test 24 hours after bonding. Data were subjected to split-plot ANOVA and the Tukey test (p = 0.05). ERCs containing DPI showed statistically significant higher bond strengths compared with ERCs without DPI. ERCs containing DPI were statistically similar to VARIOLINK II - dual-cured and superior to VARIOLINK II - light-cured (except for EDMAB - 1DPI in the medium third and DMAEMA - 1DPI in the coronal third). Different amines did not influence post retention. The apical root region showed the lowest bond strength for the groups EDAB-0DPI, DMAEMA-0DPI and VARIOLINK II light-cured. Light-cured ERCs containing DPI were efficient for GFP retention to radicular dentin, with similar behaviour to that of dual-curing commercial resin cement.

Effect of Bioceramic Materials on Proliferation and Odontoblast Differentiation of Human Stem Cells from the Apical Papilla.

INTRODUCTION: In regenerative endodontic treatment (RET), practitioners favor the placement of bioceramics as sealing materials over blood clots. It is important to understand the interaction between sealing material and cells in the root canal. The purpose of this study was to compare the effectiveness of various bioceramic materials (ProRoot MTA [Dentsply, Tulsa, OK], Biodentine [Septodont, Saint-Maur-des-Fossés, France], and RetroMTA [BioMTA, Seoul, Korea]) as sealing materials in RET for the proliferation and differentiation of stem cells from the apical papilla (SCAPs). METHODS: SCAPs were seeded at 20,000 cells/well and cultured with soluble agents of testing materials through a transwell culture plate. The proliferation of SCAPs was investigated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay on days 1, 3, 7, and 14 of testing. Alizarin red staining and quantitative real-time polymerase chain reaction were used for SCAP differentiation at different time points (1, 7, 14, and 21 days). The odontoblast genes expressed are dentin matrix acidic phosphoprotein 1, dentin sialophosphoprotein, osteocalcin, and matrix extracellular phosphoglycoprotein, which were used in this study. The SCAPs were cultured in odonto/osteogenic induction medium and also contacted soluble agents from the testing materials. RESULTS: All 3 tested biomaterials induced SCAP proliferation. The Biodentine, ProRootMTA, and RetroMTA groups showed significant SCAP proliferation on days 7 and 14 compared with the control. In regard to odontoblastic differentiation, only Biodentine showed positive alizarin red staining. The highest expressions of dentin matrix acidic phosphoprotein 1, dentin sialophosphoprotein, and matrix extracellular phosphoglycoprotein were found on day 21 in the Biodentine group. The expression of osteocalcin was found to be significant on day 7. CONCLUSIONS: Biodentine, ProRootMTA, and RetroMTA can induce SCAP proliferation. Biodentine induced significant SCAP differentiation among the 3 materials.

A Comparative Evaluation of Concentrated Growth Factor and Platelet-rich Fibrin on the Proliferation, Migration, and Differentiation of Human Stem Cells of the Apical Papilla.

INTRODUCTION: Concentrated growth factor (CGF) is considered to be a natural biomaterial that is better than platelet-rich fibrin (PRF) in bone regeneration, but there is little information acquired in regenerative endodontics. Therefore, the purpose of this study was to evaluate their effects on the proliferation, migration, and differentiation of human stem cells of the apical papilla (SCAPs). METHODS: CGF- and PRF-conditioned medium were prepared using the freeze-dried method. SCAPs were isolated and identified. The proliferative potential of SCAPs was investigated using the Cell Counting Kit-8 (KeyGen Biotech, Nanjing, China). The migration capacity was analyzed using transwell assays, and the mineralization ability was determined by alizarin red S staining. The expression levels of alkaline phosphatase, bone sialoprotein, dentin matrix protein 1, and dentin sialophosphoprotein were determined by quantitative polymerase chain reaction. RESULTS: The cultured cells exhibited mesenchymal stem cell characteristics. The growth rate and migratory cell numbers of the CGF and PRF groups were significantly greater than those of the control group. The mineralized areas in the CGF and PRF groups were significantly larger than those in the control group after incubation for 7 days and 14 days. The expression levels of osteogenic/odontoblast-related genes were reduced on day 7, but they were dramatically enhanced on day 14, and the related gene expression levels in the PRF group were higher than those in the CGF group. CONCLUSIONS: Both CGF and PRF can promote the proliferation, migration, and differentiation of SCAPs. CGF may be a promising alternative in regenerative endodontics.

The Effects of Irrigants on the Survival of Human Stem Cells of the Apical Papilla, Including Endocyn.

INTRODUCTION: Endocyn, a pH-neutral solution of hypochlorous acid and hypochlorite has been developed for use as an endodontic irrigant. The purpose of this study was to evaluate the effect of Endocyn on human periodontal ligament (PDL) fibroblasts, rat osteosarcoma cells (UMR-106), and stem cells of the apical papilla (SCAP) compared with other commonly used endodontic irrigants. METHODS: To determine cytotoxicity, cells were exposed to various concentrations of Endocyn, 6% sodium hypochlorite (NaOCl), 17% EDTA, and 2% chlorhexidine for 10 minutes, 1 hour, or 24 hours. Cell survival was measured fluorescently using calcein AM. Endocyn also was tested for its ability to inhibit SCAP proliferation and alkaline phosphatase activity. Finally, SCAP transcript expression was examined via reverse-transcriptase polymerase chain reaction. RESULTS: Endocyn was no more toxic to PDL and UMR cells than water for up to 24 hours. Endocyn concentrations of 50% were toxic to SCAP after 1 hour of exposure. Endocyn concentrations of >20% inhibited SCAP proliferation, whereas concentrations of ≥10% inhibited alkaline phosphatase activity. Exposure of SCAP to 10% Endocyn for 3 days did not alter most transcript expression, but did significantly reduce the expression of alkaline phosphatase, fibromodulin, and osteomodulin. CONCLUSION: Endocyn was significantly less cytotoxic to PDL, UMR-106, and SCAP cells compared with other commonly used endodontic irrigants. High concentrations of Endocyn did inhibit some transcript expression and alkaline phosphatase activity, indicating a potential reduction in the osteogenic potential of stems cells exposed to Endocyn.

Light curing resin cements containing iodonium salts promote suitable apical bonding of posts to radicular dentin

Abstract The aim of this study was to analyze the efficiency of experimental light-curing resin cements (ERCs) with a ternary photo-initiator system containing diphenyliodonium hexafluorphosphate (DPI) and different amines on retention of glass-fiber posts to dentin (GFP). ERCs formulations: a 1:1 mass ratio of 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenylpropane and triethyleneglycol dimethacrylate. Camphorquinone was used as initiator. Six experimental groups were established according to the amine used: [ethyl-4-(dimethylamino)benzoate-EDMAB or 2-(dimethylamino)ethyl methacrylate-DMAEMA] and the concentration of DPI (0, 0.5 mol%, 1 mol%). The resin cements Variolink II (dual- and light-cured versions) were used as commercial reference. Eighty recently extracted bovine incisors (n = 10) were selected for this study. The roots were prepared and the fiber posts were cemented with the resin cement specified for each experimental group. Specimens from coronal, middle, and apical thirds of the root were subjected to push-out bond strength test 24 hours after bonding. Data were subjected to split-plot ANOVA and the Tukey test (p = 0.05). ERCs containing DPI showed statistically significant higher bond strengths compared with ERCs without DPI. ERCs containing DPI were statistically similar to VARIOLINK II - dual-cured and superior to VARIOLINK II - light-cured (except for EDMAB - 1DPI in the medium third and DMAEMA - 1DPI in the coronal third). Different amines did not influence post retention. The apical root region showed the lowest bond strength for the groups EDAB-0DPI, DMAEMA-0DPI and VARIOLINK II light-cured. Light-cured ERCs containing DPI were efficient for GFP retention to radicular dentin, with similar behaviour to that of dual-curing commercial resin cement.

Effects of Lipopolysaccharide on the Proliferation and Osteogenic Differentiation of Stem Cells from the Apical Papilla.

INTRODUCTION: Stem cells from the apical papilla (SCAPs) were suggested as the stem cell source in regenerative endodontic procedures. However, bone and/or cementum-like structure were observed in root canals. Lipopolysaccharide (LPS) in infected root canals might alter SCAPs' osteogenic differentiation pattern. The objectives of this study were to investigate the effects of LPS on SCAPs' proliferation and osteogenic differentiation. METHODS: The mesenchymal stem cell characteristics of SCAPs were confirmed. Cell viability was tested with Porphyromonas gingivalis LPS at concentration between 0.001 and 5 µg/mL. SCAPs were pretreated with those concentrations for 168 hours. Then SCAPs were further investigated for cell proliferation by resazurin-based assay. Mineralization capacity was determined by alizarin red S staining. Odontoblast marker was determined by DSPP gene expression. General bone and cementum markers, BSP and OPN, were also determined. Determination of the expression levels of these genes was performed by polymerase chain reaction. RESULTS: SCAPs demonstrated the mesenchymal stem cell characteristics. All LPS concentrations did not affect cell viability. Pretreatment with LPS also did not affect cell proliferation and mineralization in every concentration. There was no significant difference between DSPP and OPN gene expression levels at all concentrations. However, LPS at 5 µg/mL significantly increased BSP gene expression. CONCLUSIONS: Under the limitations of this in vitro study, LPS did not affect SCAP proliferation and mineralization. However, LPS at high concentration, 5 µg/mL, increased BSP gene expression.

Effect of application time of maleic acid on smear layer removal and mechanical properties of root canal dentin.

OBJECTIVES: To evaluate the effect of maleic acid (MA) on the cleaning efficacy and mechanical properties of root canal dentine with respect to different time exposure. MATERIALS AND METHODS: One hundred and eighty single-canal premolars were instrumented with rotary-files and then randomly assigned to test groups receiving 7% MA for 30 s, 45 s, 1 min, or 3 min or to control groups treated with 0.9% saline or 17% ethylenediaminetetraacetic acid for 45 s. The micro-hardness, nano-hardness and elastic modules were measured before and after treatment, while the amount of smear and erosion in the coronal, middle and apical thirds in root canal were evaluated by scanning electron microscopy, finally, the fracture strength was assessed by vertical root fracture testing. RESULTS: The efficacy of smear layer removal increased with increasing MA application time. The largest effect was observed at 45 s, even in the apical third, whereas the treatment for 1 min resulted in irreversible erosion of the dentine surface. The micro-hardness and nano-indentation testing confirmed that the micro- and nano-scale mechanical properties were significantly decreased after MA application for 1 min. Furthermore, the specimens treated with MA for 3 min presented the lowest fracture resistance among all groups. In contrast, the 45 s treatment appeared to increase the fracture resistance of the tooth. CONCLUSIONS: The cleaning efficacy and mechanical properties of root canal dentine varied with MA exposure time. The application of MA for 45 s was found to be the most promising for clinical use.

Release of Growth Factors into Root Canal by Irrigations in Regenerative Endodontics.

INTRODUCTION: The aim of this study was to investigate the release of growth factors into root canal space after the irrigation procedure of regenerative endodontic procedure. METHODS: Sixty standardized root segments were prepared from extracted single-root teeth. Nail varnish was applied to all surfaces except the root canal surface. Root segments were irrigated with 1.5% NaOCl + 17% EDTA, 2.5% NaOCl + 17% EDTA, 17% EDTA, or deionized water. The profile of growth factors that were released after irrigation was studied by growth factor array. Enzyme-linked immunosorbent assay was used to validate the release of transforming growth factor (TGF)-ß1 and basic fibroblast growth factor (bFGF) at 4 hours, 1 day, and 3 days after irrigation. The final concentrations were calculated on the basis of the root canal volume measured by cone-beam computed tomography. Dental pulp stem cell migration on growth factors released from root segments was measured by using Transwell assay. RESULTS: Total of 11 of 41 growth factors were detected by growth factors array. Enzyme-linked immunosorbent assay showed that TGF-ß1 was released in all irrigation groups. Compared with the group with 17% EDTA (6.92 ± 4.49 ng/mL), the groups with 1.5% NaOCl + 17% EDTA and 2.5% NaOCl + 17% EDTA had significantly higher release of TGF-ß1 (69.04 ± 30.41 ng/mL and 59.26 ± 3.37 ng/mL, respectively), with a peak release at day 1. The release of bFGF was detected at a low level in all groups (0 ng/mL to 0.43 ± 0.22 ng/mL). Migration assay showed the growth factors released from root segments induced dental pulp stem cell migration. CONCLUSIONS: The root segment model in present study simulated clinical scenario and indicated that the current irrigation protocol released a significant amount of TGF-ß1 but not bFGF. The growth factors released into root canal space induced dental pulp stem cell migration.

Preexisting Periapical Inflammatory Condition Exacerbates Tooth Extraction-induced Bisphosphonate-related Osteonecrosis of the Jaw Lesions in Mice.

INTRODUCTION: Surgical interventions such as tooth extraction increase the chances of developing osteonecrosis of the jaw in patients receiving bisphosphonates (BPs) for the treatment of bone-related diseases. Tooth extraction is often performed to eliminate preexisting pathological inflammatory conditions that make the tooth unsalvageable; however, the role of such conditions on bisphosphonate-related osteonecrosis of the jaw (BRONJ) development after tooth extraction is not clearly defined. Here, we examined the effects of periapical periodontitis on tooth extraction-induced BRONJ development in mice. METHODS: Periapical periodontitis was induced by exposing the pulp of the maxillary first molar for 3 weeks in C57/BL6 mice that were intravenously administered with BPs. The same tooth was extracted, and after an 3 additional weeks, the mice were harvested for histologic, histomorphometric, and histochemical staining analyses. RESULTS: Pulp exposure induced periapical radiolucency as shown by increased inflammatory cells, tartrate-resistant acid phosphatase-positive osteoclasts, and bone resorption. When BPs were administered, pulp exposure did not induce apical bone resorption despite the presence of inflammatory cells and tartrate-resistant acid phosphatase-positive osteoclasts. Although tooth extraction alone induced BRONJ lesions, pulp exposure further increased tooth extraction-induced BRONJ development as shown by the presence of more bone necrosis. CONCLUSIONS: Our study demonstrates that a preexisting pathological inflammatory condition such as periapical periodontitis is a predisposing factor that may exacerbate BRONJ development after tooth extraction. Our study further provides a clinical implication wherein periapical periodontitis should be controlled before performing tooth extraction in BP users in order to reduce the risk of developing BRONJ.

Tissue characterization following revascularization of immature dog teeth using different disinfection pastes.

Revascularization of immature teeth with necrotic pulps traditionally involves the use of triple antibiotic paste, which may sometimes lead to undesirable complications. The objective of this study was to assess tissue repair in immature dog teeth with apical periodontitis subjected to revascularization, comparing two different pastes used for root canal disinfection. Apical periodontitis was induced in 30 dog premolars. Teeth were randomly divided into three experimental groups: root canals filled with triple antibiotic paste (n = 10); root canals filled with 1% propolis paste (n = 10); and no medication (n = 10). An additional group (n = 10, no intervention) was used as control. After 7 months, the jaws were histologically evaluated for the following variables: newly formed mineralized tissue (present/absent); vital tissue in the canal space (absent/periodontal ligament-like/pulp-like); apical extension of root (present/absent); and severity of inflammatory process (absent/mild/moderate/severe). There were no statistically significant differences among the experimental groups in new mineralized tissue formation and apical root development. The formation of vital tissue in the canal space, in turn, was statistically different between the triple paste and propolis groups: vital tissues were present in all revascularized teeth disinfected with propolis paste (100%), compared to 71% of those disinfected with the triple paste. Severity of inflammatory process was different between the triple paste and no medication groups. The new tissues formed onto canal walls and in the root canal space showed characteristics of cementum and periodontal ligament, respectively. Propolis may have some advantages over the triple paste for the revascularization of immature teeth.

Effects of a Bioactive Scaffold Containing a Sustained Transforming Growth Factor-ß1-releasing Nanoparticle System on the Migration and Differentiation of Stem Cells from the Apical Papilla.

INTRODUCTION: This 2-part study hypothesized that a bioactive scaffold containing a sustained transforming growth factor (TGF)-ß1-releasing nanoparticle system will promote migration and enhance differentiation of stem cells from the apical papilla (SCAP). The study aimed to develop and characterize a novel modified chitosan-based scaffold containing TGF-ß1-releasing chitosan nanoparticles (TGF-ß1-CSnp) to enhance migration and differentiation of SCAP. METHODS: Part I concerns the synthesis and characterization of a carboxymethyl chitosan-based scaffold and TGF-ß1-CSnp. Part II examines the effect of sustained TGF-ß1 release from scaffold containing TGF-ß1-CSnp on odontogenic differentiation of SCAP. RESULTS: The scaffold demonstrated properties conducive to cellular activities. The incorporation of TGF-ß1 in CSnp allowed sustained release of TGF-ß1, facilitating delivery of a critical concentration of TGF-ß1 at the opportune time. TGF-ß1 bioactivity was maintained for up to 4 weeks. SCAP showed greater viability, migration, and biomineralization in the presence of TGF-ß1-CSnp than in the presence of free TGF-ß1. SCAP cultured in TGF-ß1-CSnp + scaffold showed significantly higher dentin matrix protein-1 and dentin sialophosphoprotein signals compared with free TGF-ß1 + scaffold or CSnp + scaffold. CONCLUSIONS: These experiments highlighted the potential of a carboxymethyl chitosan-based scaffold with growth factor releasing nanoparticles to promote migration and differentiation of SCAP. The results of this study may have direct application to improve current endodontic regenerative protocols.

Influence of Root Canal Tapering on Smear Layer Removal.

The purpose of the study presented here was to compare the influence of root canal taper on the efficacy of irrigants and chelating agents in smear layer removal. Eighty mesial roots of molar teeth were selected and prepared with rotary instruments. In group A, file 30/0.02 and in group B, file 30/0.4 were placed at working length and the smear layer was removed. In groups C and D, root canal preparation was the same as in groups A and B, respectively, except that the smear layer was not removed. The amount of the smear layer was quantified using a scanning electron microscope. Greater smear layer was detected in the apical portion of each group, whereas no significant difference was detected between groups in other portions. No statistical difference was found between canals with different tapers.