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.

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.

Expression of Mineralization Markers during Pulp Response to Biodentine and Mineral Trioxide Aggregate.

INTRODUCTION: The purpose of this study was to compare the cell viability of dental pulp cells treated with Biodentine (Septodont, Saint-Maur, France) and mineral trioxide aggregate (MTA) and the in vitro and in vivo expression of mineralization markers induced by the 2 materials. METHODS: Human dental pulp cells isolated from 6 permanent teeth were stimulated with Biodentine and MTA extracts. Cell viability was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, and quantitative reverse-transcriptase polymerase chain reaction was used to determine the expression of mineralization markers. Specimens of teeth from dogs treated with Biodentine and MTA after pulpotomy were used to determine the presence of osteopontin and alkaline phosphatase by immunohistochemistry and runt-related transcription factor 2 by immunofluorescence. RESULTS: No significant differences in cell viability were found between MTA and Biodentine extracts and controls after 24 and 48 hours (P > .05). After 48 hours, osteopontin (SPP1), alkaline phosphatase (ALP), and runt-related transcription factor 2 (RUNX2) expression was higher in MTA and Biodentine than in controls (P < .05). Osteopontin staining was more intense and spread over a greater number of areas in Biodentine than in MTA samples (P < .0001). Alkaline phosphatase staining of a mineralized tissue bridge was significantly different between materials (P < .0001), but no difference in alkaline phosphatase staining of pulp tissue was found between MTA and Biodentine (P = .2). Also, no significant difference in the number of cells labeled for runt-related transcription factor 2 by immunofluorescence was observed between materials (P > .05). CONCLUSIONS: Biodentine stimulated similar markers as MTA, but staining was more intense and spread over a larger area of the pulp tissue.

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

Abstract 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.

Cyclophosphamide-Induced Morphological Changes in Dental Root Development of ICR Mice.

BACKGROUND: Survivors of childhood cancer are at risk of late dental development. Cyclophosphamide is one of the most commonly used chemotherapeutic agents against cancer in children. The aim of this study was to investigate the effects of cyclophosphamide on root formation in the molars of growing mice and to assess the morphological changes in these roots using three-dimensional structural images. METHODS: We treated 16 12-day-old ICR mice with cyclophosphamide (100 mg/kg, i.p.) and 16 control mice with saline. At 16, 20, 24, and 27 days of age, the mandibular left first molars were scanned using soft micro-computed tomography. After scanning, the structural indices were calculated using a three-dimensional image analysis system, and the images were subjected to three-dimensional reconstruction. The length and apical foramen area of all distal roots were assessed. Histological changes in the apical region were then assessed via hematoxylin and eosin staining. RESULTS: The mandibular molars of all experimental mice showed evidence of cytotoxic injury, which appeared in the form of anomalous root shapes. Although all roots developed further after cyclophosphamide injection, the three-dimensional structural images showed that the roots in the experimental group tended to develop more slowly and were shorter than those in the control group. At 27 days of age, the mean root length was shorter in the experimental group than in the control group. Conversely, the apical foramen of the roots in the experimental group tended to close faster than that of roots in the control group. In addition, hematoxylin and eosin staining of the distal roots in the experimental group showed increased dentin thickness in the apical region. CONCLUSION: Our results suggest that cyclophosphamide can result in short root lengths and early apical foramen closure, eventually leading to V-shaped or thin roots.

Efficacy of Laser Activated Irrigation on Apically Extruded Debris with Different Preparation Systems.

OBJECTIVE: The aim of this study was to evaluate apical extrusion of debris in canals prepared with three nickel-titanium (NiTi) rotary file systems [Twisted File Adaptive (TFA), SybronEndo, Orange, CA], Reciproc [(RP), VDW, Munich, Germany], and Revo-S [(RS), MicroMega, Besançon, France] and two irrigation [conventional needle (CNI) and laser-activated (LAI)] techniques. BACKGROUND DATA: Although previous studies have evaluated the amount of apically extruded debris by various instrumentation and irrigation methods, none of them have investigated the effect of LAI during the root canal preparation on debris extrusion. METHODS: Ninety extracted single-rooted human mandibular premolars with straight canals were randomly assigned to six groups (n=15) according to the file and irrigation protocols used: (1) TFA and LAI group, (2) RP and LAI group, (3) RS and LAI group, (4) TFA and CNI group, (5) RP and CNI group, and (6) RS and CNI group. Debris extruded from the apical foramen during root canal preparation was collected into preweighed Eppendorf tubes. The weight of the dry extruded debris was established by subtracting the preinstrumentation and postinstrumentation weight of the Eppendorf tubes for each group. Data were analyzed using the Kruskal Wallis and Mann Whitney U tests with Bonferroni correction to compare groups. RESULTS: LAI groups extruded more debris than CNI groups (p<0.05). However, no statistically significant differences were observed among the file groups when each irrigation method was evaluated separately (p>0.017). CONCLUSIONS: Within the limitations of this study, it can be concluded that the agitation method, such as LAI, had a significant effect on the amount of extrusion.

Comparison of Quick-Set and mineral trioxide aggregate root-end fillings for the regeneration of apical tissues in dogs.

INTRODUCTION: Quick-Set (Avalon Biomed Inc, Bradenton, FL) is a calcium aluminosilicate cement that is a potential alternative to mineral trioxide aggregate (MTA) with greater acid resistance and faster setting. The purpose of this study was to compare the regeneration of apical tissues after root-end surgery when the apical tissues were exposed to Quick-Set or White ProRoot MTA (Dentsply Tulsa Dental Specialties, Tulsa, OK) by root-end resection. METHODS: The root canals of 42 mandibular premolars in 7 beagle dogs were accessed, cleaned and shaped, and obturated with Quick-Set or white MTA. Osteotomies and root-end resections were performed immediately. The dogs were sacrificed at 90 days, and the teeth and surrounding tissues were removed and prepared for histologic analysis. The sections of the apical areas were scored for inflammation, new cementum formation, periodontal ligament formation, and bone quality. RESULTS: At 90 days, both materials supported some degree of cementum formation on the surface of the material, periodontal ligament regeneration, and excellent bone quality. The only significant difference was greater inflammation found in the Quick-Set group. CONCLUSIONS: Quick-Set and White ProRoot MTA had a similar effect on bone quality, cementum formation, and periodontal ligament formation after root-end surgery in dogs. Quick-Set was associated with greater inflammation.

Enriched trimethylation of lysine 4 of histone H3 of WDR63 enhanced osteogenic differentiation potentials of stem cells from apical papilla.

INTRODUCTION: Dental tissue-derived mesenchymal stem cells (MSCs) are a reliable cell source for dental tissue regeneration. However, the molecular mechanisms underlying their directed differentiation remain unclear, thus limiting their use. Trimethylation of lysine 4 of histone H3 (H3K4Me3) correlates with gene activation and osteogenic differentiation. We used stem cells from apical papilla (SCAPs) to investigate the effects of genomic changes in H3K4Me3 modification at gene promoter regions on MSC osteogenic differentiation. METHODS: ChIP-on-chip assays were applied to compare the H3K4Me3 profiles at gene promoter regions of undifferentiated and differentiated SCAPs. Alkaline phosphatase activity assay, alizarin red staining, quantitative analysis of calcium, the expressions of osteogenesis-related genes, and transplantation in nude mice were used to investigate the osteogenic differentiation potentials of SCAPs. RESULTS: In differentiated SCAPs, 119 gene promoters exhibited >2-fold increases of H3K4Me3; in contrast, the promoter regions of 21 genes exhibited >2-fold decreases of H3K4Me3. On the basis of enriched H3K4Me3 and up-regulated gene expression on the osteogenic differentiation of SCAPs, WDR63 may be a potential regulator for mediating SCAP osteogenic differentiation. Through gain-of-function and loss-of-function studies, we discovered that WDR63 enhances alkaline phosphatase activity, mineralization, and the expression of BSP, OSX, and RUNX2 in vitro. In addition, transplant experiments in nude mice confirmed that SCAP osteogenesis is triggered by activated WDR63. CONCLUSIONS: These results indicate that WDR63 is a positive enhancer for SCAP osteogenic differentiation and suggest that activation of WDR63 signaling might improve tissue regeneration mediated by MSCs of dental origin.

Histologic evaluation of the effects of Emdogain gel on injured root apex in rats.

INTRODUCTION: This study investigated the effects of Emdogain gel (EMD) on the injured open apex within periapical lesions. METHODS: Periapical lesions were induced in rats by opening the pulp chambers of the mandibular first molars and filing the apical foramen through the distal root canal with #25 K-files to make an open apex. The teeth were exposed to the oral environment for 7 days. Then we irrigated the distal root canals and divided them into EMD-treated and propylene glycol alginate-treated groups. The rats were killed 7, 14, and 28 days after treatment and examined histochemically. RESULTS: In the EMD-treated rats, more cells expressed transforming growth factor-ß1 or bone morphogenetic protein-2 at 7 days after treatment, and the regeneration of cementum and bone was observed around the root apex at 14 days after treatment. Conversely, in the propylene glycol alginate-treated group, few cells expressed transforming growth factor-ß1 or bone morphogenetic protein-2, and apical periodontal tissue recovery was rarely seen within the periapical lesions throughout the experiment. CONCLUSIONS: These results suggest that EMD does not irritate injured periapical tissue and may create a favorable environment that promotes the healing of destroyed periapical tissues.

Autotransplantation of a Mandibular Third Molar: A Case Report with 5 Years of Follow-up

This paper describes the autologous transplantation of a mandibular right third molar to replace the residual roots of the second molar in the same quadrant, preserving function and aesthetics. A 5-year clinical and radiographic follow-up was undertaken. After transplantation, the donor tooth received endodontic treatment and placement of calcium hydroxide, which was periodically replaced every 3 months until the filling of the root canals, totalizing a period of 1-year, when apical closure was confirmed. The tooth was in perfect functional and aesthetic conditions 5 years after beginning of treatment. Autotransplantation is a feasible option for replacing missing teeth when a donor tooth is available. The autotransplantation of a right mandibular third molar with compromised function and aesthetics to replace the residual roots resulting from coronal destruction due to extensive carious lesion of the second molar in the same quadrant was a viable treatment alternative.

O objetivo deste trabalho foi descrever o transplante autógeno de um terceiro molar inferior direito para substituir as raízes residuais do segundo molar no mesmo quadrante, preservando a função e a estética. Foi realizado acompanhamento clínico e radiográfico por 5 anos. Após o transplante, o dente doador recebeu tratamento endodôntico e colocação de hidróxido de cálcio, o qual foi substituído periodicamente a cada 3 meses, até a obturação dos canais radiculares, totalizando período de 1 ano quando então, o fechamento apical foi confirmado. O dente encontra-se em perfeitas condições funcionais e estéticas após 5 anos do início do tratamento. O autotransplante é uma opção viável para a substituição de dentes perdidos quando um dente doador está disponível. O autotransplante de um terceiro molar inferior direito com comprometimento estético e funcional afim de substituir raízes residuais (resultado de um processo cariogênio extenso) de um segundo molar do mesmo quadrante foi um tratamento alternativo viável.

Sealability of MTA and calcium hydroxidecontaining sealers

OBJECTIVES: The aim of this study was to evaluate the apical sealability of Fillapex®, endo-CPM-Sealer® and Sealapex®. Material and Methods: Ninety-four freshly extracted single-rooted teeth were selected and decoronated. All teeth were radiographed to confirm the existence of a single and straight root canal, which was prepared using Protaper Universal and 2.5% sodium hypochlorite. The teeth were randomly divided in groups of 10 specimens each according to the sealer, and the canals were filled using the single cone technique and one of the sealers. Four additional teeth were used as controls. The teeth were submitted to dye leakage with Rhodamine B for 24 h but using vacuum on the initial 15 min. Thereafter, they were cut longitudinally and the leakage was measured in a linear fashion from apex to crown. Data were analyzed by ANOVA and Tukey's tests at 5% significance level. Results: Fillapex® and Sealapex® showed significantly less dye leakage than endo-CPM-Sealer® (p<0.05). Conclusions: It was concluded that Fillapex® and Sealapex® were able to prevent apical dye leakage differently from endo-CPM-Sealer®.

Basic fibroblast growth factor enhances stemness of human stem cells from the apical papilla.

INTRODUCTION: Stem cells from the apical papilla (SCAP) are a type of mesenchymal stem cells found in the developing tissue, apical papilla, of immature permanent teeth. Studies have shown that SCAP are likely to be a source of primary odontoblasts that are responsible for the formation of root dentin. Basic fibroblast growth factor (bFGF) is a signaling molecule and pleiotropic growth factor involved in tooth root development, and it promotes proliferation of a variety of cell types. The effects of bFGF on SCAP, however, have not been examined. METHODS: We investigated the regulatory effects of bFGF on the proliferation and differentiation potential of human SCAP in vitro. Changes in the cell cycle and proliferation, colony-forming unit-fibroblastic formation, alkaline phosphatase (ALP) activity, osteogenic/dentinogenic differentiation, and stem cell gene makers of SCAP, cultured in the presence or absence of bFGF, were evaluated. RESULTS: Treatment with 5 ng/mL bFGF significantly increased SCAP proliferation and their colony-forming unit-fibroblastic formation efficiency. The growth factor also increased the expression of STRO-1 and the stem cell gene makers Nanog, Oct4, Sox2, and Rex1 in SCAP. In contrast, bFGF reduced the ALP activity, mineral nodule formation, and the expression of ALP, osteocalcin, bone sialoprotein, and dentin sialophosphoprotein. When SCAP cultures were expanded in the presence of bFGF for 1 week, subsequent stimulation of the osteogenic/dentinogenic condition resulted in enhanced differentiation. CONCLUSIONS: Under certain conditions, bFGF enhances SCAP stemness by up-regulating stem cell gene expression, increasing proliferation ability, and potentiating differentiation potency.

The effect of frequency of calcium hydroxide dressing change and various pre- and inter-operative factors on the endodontic treatment of traumatized immature permanent incisors.

AIM: The objectives of this clinical study were as follows: (i) to determine the effect of frequency of calcium hydroxide [Ca(OH)(2)] dressing change on the apical barrier formation in immature permanent incisors with necrotic pulps and (ii) to investigate the effect of various clinical factors before and during treatment that may be associated with the frequency of Ca(OH)(2) dressing changes. METHODS: The study involved 21 healthy subjects, 8-12 years old. Twenty-three immature traumatized permanent maxillary central incisors were treated using Ca(OH)(2) powder mixed with barium sulfate and distilled water. The progress of barrier formation was reviewed after 6 months of first placement of Ca(OH)(2) and then every 3 months until the detection of an apical barrier. Clinical and radiographic evaluations were performed before and after treatment. Data were evaluated using a chi-square test. RESULTS: Apical barrier formation was successful for all 23 teeth. Seventeen teeth (74%) needed only a single application of Ca(OH)(2), while six teeth (26%) required more than one application. The average time of apical barrier formation was 30 weeks, and the mean number of Ca(OH)(2) dressing changes was 1.3. A significant positive association was found between teeth that presented with displacement and the number of Ca(OH)(2) dressing changes (P = 0.004). CONCLUSION: An initial 6-month application of Ca(OH)(2) dressing followed by 3-month replacements (usually in teeth presenting with displacement and/or sinus tracts) may be successfully used in apexification treatment. This would assist in reducing the number of Ca(OH)(2) dressing changes, number of appointments, cost of treatment and radiation exposure.

Effects of three different irrigating solutions and KTP laser irradiation on apical leakage: an electrochemical study.

OBJECTIVE: The purpose of this study was to evaluate the effect of three different irrigating solutions (17% EDTA, 10% citric acid and 2.5% NaOCl) and KTP laser irradiation on apical leakage using an electrochemical method. MATERIALS AND METHODS: Sixty extracted single-rooted human teeth with mature apices were instrumented up to a size 35 K-file. After using each file and before proceeding to the next, canals were irrigated with 2 ml of 2.5% NaOCl. All teeth were then randomly divided into four groups. In group 1, the root canals were irrigated with a final flush of 17% EDTA. In group 2, the root canals were irrigated with a final flush of 10% citric acid. In group 3, the root canals were irradiated with KTP laser at 1 W, 4.45 J/cm(2). In group 4, the root canals were irrigated with a final flush of 2.5% NaOCl. The root canals were then filled using the cold lateral condensation method. Apical leakage was evaluated using an electrochemical method over a period of 10 days. Data were analysed using Tukey HSD and Friedmann tests with p = 0.05 as the level for statistical significance. RESULTS: The 17% EDTA and 10% citric acid groups had statistically less apical leakage than the 2.5% NaOCl group at days 7, 8, 9 and 10 (p < 0.05); however, no significant differences were found between the tested groups at the other time intervals (p > 0.05). No significant difference was found between the KTP laser group and other groups tested at all time intervals (p > 0.05). CONCLUSION: All groups were unable to eliminate apical leakage. However, final irrigation with 17% EDTA and 10% citric acid following root canal preparation reduced postobturation apical leakage compared with 2.5% NaOCl irrigation. When KTP laser and the other three irrigants were compared, no significant difference was found.

Hepatocyte growth factor stimulates root growth during the development of mouse molar teeth.

BACKGROUND AND OBJECTIVE: It is well known that tooth root formation is initiated by the development of Hertwig's epithelial root sheath (HERS). However, relatively little is known about the regulatory mechanisms involved in root development. As hepatocyte growth factor (HGF) is one of the mediators of epithelial-mesenchymal interactions in rodent tooth, the objective of this study was to examine the effects of HGF on the root development of mouse molars. MATERIAL AND METHODS: The HERS of mouse molars and HERS01a, a cell line originated from HERS, were used in this study. For detection of HGF receptors in vivo and in vitro, we used immunochemical procedures. Root development was assessed by implanting molar tooth germs along with HGF-soaked beads into kidney capsules, by counting cell numbers in HERS01a cell cultures and by performing a 5'-bromo-2'-deoxyuridine (BrdU) assay in an organ-culture system. RESULTS: HGF receptors were expressed in the enamel epithelium of molar germs as well as in HERS cells. HGF stimulated root development in the transplanted tooth germs, the proliferation of HERS01a cells in culture and HERS elongation in the organ-culture system. Examination using BrdU revealed that cell proliferation in HERS was increased by treatment with HGF, especially that in the outer layer of HERS. This effect was down-regulated when antibody against HGF receptor was present in the culture medium. CONCLUSION: Our results raise the possibility that HGF signaling controls root formation via the development of HERS. This study is the first to show that HGF is one of the stimulators of root development.

Efficacy of sodium hypochlorite, ethylenediaminetetraacetic acid, citric acid and phosphoric acid in calcium hydroxide removal from the root canal: a microscopic cleanliness evaluation.

Rooted molars were subjected to standardized canal instrumentation to a master apical file (MAF). The samples were dressed with Ca(OH)(2), and after 7 days, teeth were reopened and Ca(OH)(2) medication was removed by 1 of 4 different experimental procedures: 2.5% sodium hypochlorite (NaOCl) (n = 10); 17% EDTA-T (n = 10); 10% citric acid (n = 10); or 37% phosphoric acid (n = 10). This was followed by reinstrumentation with MAF plus 15 mL saline solution. The roots were prepared for scanning electron microscopic analysis of the cervical, middle, and apical thirds. Statistical analysis was performed with the Kruskal-Wallis test. EDTA-T and phosphoric acid gave the best results in the apical third, with significant statistical differences compared with other groups. NaOCl gave the worst results. Irrigation with 17% EDTA-T and 37% phosphoric acid is more effective than sodium hypochlorite and citric acid in the removal of calcium hydroxide from the apical third.

Tissue reaction to Endométhasone sealer in root canal fillings short of or beyond the apical foramen

OBJECTIVE: This study evaluated the response of periapical tissues to the endodontic sealer Endométhasone in root canal fillings short of or beyond the apical foramen. MATERIAL AND METHODS: Twenty root canals of premolars and incisors of 2 mongrel dogs were used. After coronal access and pulp extirpation, the canals were instrumented up to a size 55 K-file and the apical cemental barrier was penetrated with a size 15 K-file to obtain a main apical foramen, which was widened to a size 25 K-file. The canals were irrigated with saline at each change of file. The root canals were obturated either short of or beyond the apical foramen by the lateral condensation of gutta-percha and Endométhasone, originating 2 experimental groups: G1: Endométhasone/short of the apical foramen; G2: Endométhasone/beyond the apical foramen. The animals were killed by anesthetic overdose 90 days after endodontic treatment. The individual roots were obtained and serial histological sections were prepared for histomorphological analysis (H&E and Brown & Brenn techniques) under light microscopy. The following parameters were examined: closure of the apical foramen of the main root canal and apical opening of accessory canals, apical cementum resorption, intensity of the inflammatory infiltrate, presence of giant cells and thickness and organization of the apical periodontal ligament. Each parameter was scored 1 to 4, 1 being the best result and 4 the worst. Data were analyzed statistically by the Wilcoxon nonparametric tests (p=0.05). RESULTS: Comparing the 2 groups, the best result (p<0.05) was obtained with root canal filling with Endométhasone short of the apical foramen but a chronic inflammatory infiltrate was present in all specimens. CONCLUSIONS: Limiting the filling material to the root canal space apically is important to determine the best treatment outcome when Endométhasone is used as sealer.

Effectiveness of ethylenediaminetetraacetic acid (EDTA) and MTAD on debris and smear layer removal using a self-adjusting file.

OBJECTIVE: The aim of this study was to investigate the cleaning ability of a self-adjusting file (SAF) system regarding debris and smear layer removal using ethylenediaminetetraacetic acid (EDTA) or MTAD. STUDY DESIGN: In total, 45 maxillary incisor teeth were randomly divided into 2 different irrigation groups of 20 canals each and a negative control group of 5 canals. The canals in each of the irrigation groups were irrigated using sodium hypochlorite (1.3%) as an initial irrigant during the first 2 minutes of operation, followed by 2 minutes continuous irrigation with either 17% EDTA or MTAD in a closed system. The negative control group was irrigated using 1.3% sodium hypochlorite. The roots were split longitudinally and subjected to scanning electron microscopy (SEM). The presence of debris and smear layer in the coronal, middle, and apical thirds of the canal was evaluated using a 5-grade scoring system with ×200 and ×2,000 magnification, respectively. RESULTS: The SAF operation with 2-minute continuous irrigation using MTAD resulted in root canal walls that were free of smear layer in 85%, 70%, and 60% and of debris in 95%, 90%, and 95% of the coronal, middle, and apical thirds of the root canals, respectively. The SAF operation with continuous irrigation using EDTA resulted in root canal walls that were free of smear layer in 85%, 60%, and 50% and of debris in 95%, 90%, and 85% of the coronal, middle, and apical thirds of the root canals, respectively. Teeth in the negative control group were totally covered with debris. Evaluation by SEM showed no significant difference between the tested irrigants in removing the smear layer and debris among the different regions of the root canal. Both groups were significantly different from the negative control group. CONCLUSIONS: When using the SAF, the protocols used in this study were effective for debridement for all regions of the root canal even for the apical thirds.