Comparing Cyclic Fatigue Resistance and Free Recovery Transformation Temperature of NiTi Endodontic Single-File Systems Using a Novel Testing Setup.

The aim of this study was to assess the effect of body temperature (37 °C) on the cyclic fatigue resistance of three endodontic single-file systems using a new testing setup. One Shape® new generation (OS), WaveOne™ (WO) and WaveOne® GOLD (WOG), which are made from different NiTi alloys and operated in different motions (rotation/reciprocation), were evaluated. The study design included four groups. Each group comprised 30 files, 10 files of each of the three file systems, tested at 20 ± 2 °C (group 1 and 3) and at 37 ± 1 °C (group 2 and 4). All files were tested in a custom-made metal block with artificial canals of 60° angle, and a 5 mm and 3 mm radius of curvature, respectively. A heating element was attached to replicate a temperature of 37 °C. Files were introduced 18 mm into the canals and operated until failure. Transformation temperatures of five samples of each of the tested file systems were determined via the bend and free recovery (BFR) method. With the exception of WOG in canals with a 3 mm radius of curvature (p = 0.075), all the tested file systems showed statistically significantly less time needed to fracture when operated at 37 ± 1 °C compared to at 20 ± 2 °C in canals with a 5 mm and 3 mm radius of curvature using Mann-Whitney U test (p < 0.05). All file systems showed transformation temperatures below the body temperature. We concluded that body temperature directly affects the cyclic fatigue resistance of all tested file systems. Bend and free recovery can be suitable for the determination of austenite finish temperatures (Af) of endodontic instruments as it allows testing a longer portion of the instrument.

Effects of histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors on proliferative, differentiative, and regenerative functions of Toll-like receptor 2 (TLR-2)-stimulated human dental pulp cells (hDPCs).

OBJECTIVES: This in vitro study aimed to modify TLR-2-mediated effects on the paracrine, proliferative, and differentiation potentials of human dental pulp-derived cells using histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors. MATERIALS AND METHODS: Cell viability was assessed using the XTT assay. Cells were either treated with 10 µg/ml Pam3CSK4 only, or pre-treated with valproic acid (VPA) (3 mM), trichostatin A (TSA) (3 µM), and MG-149 (3 µM) for a total of 4 h and 24 h. Control groups included unstimulated cells and cells incubated with inhibitors solvents only. Transcript levels for NANOG, OCT3-4, FGF-1 and 2, NGF, VEGF, COL-1A1, TLR-2, hßD-2 and 3, BMP-2, DSPP, and ALP were assessed through qPCR. RESULTS: After 24 h, TSA pre-treatment significantly upregulated the defensins and maintained the elevated pro-inflammatory cytokines, but significantly reduced healing and differentiation genes. VPA significantly upregulated the pro-inflammatory cytokine levels, while MG-149 significantly downregulated them. Pluripotency genes were not significantly affected by any regimen. CONCLUSIONS: At the attempted concentrations, TSA upregulated the defensins gene expression levels, and MG-149 exerted a remarkable anti-inflammatory effect; therefore, they could favorably impact the immunological profile of hDPCs. CLINICAL RELEVANCE: Targeting hDPC nuclear function could be a promising option in the scope of the biological management of inflammatory pulp diseases.

Immunohistochemical Analysis of S100 Proteins in Normal and Irreversibly Inflamed Human Dental Pulps.

INTRODUCTION: S100 proteins convey important roles in innate immune responses to infection and regenerative processes. However, their role in inflammatory or regenerative processes of the human dental pulp is poorly elucidated. The aim of the present study was to detect, localize, and compare the occurrence of 8 S100 proteins in normal, symptomatic, and asymptomatic irreversibly inflamed dental pulp specimens. METHODS: Human dental pulp specimens from 45 individuals were clinically assigned to 3 groups of pulpal diagnosis: normal pulp (NP, n = 17), asymptomatic irreversible pulpitis (AIP, n = 13), and symptomatic irreversible pulpitis (SIP, n = 15). The specimens were prepared and immunohistochemically stained for proteins S100A1, -A2, -A3, -A4, -A6, -A7, -A8, and -A9. Staining was classified using semiquantitative analysis and a 4-degree staining score (ie, no, decent, medium, and intense staining) at 4 different anatomic or functional regions (ie, the odontoblast layer [OL], pulpal stroma [PS], border area of calcifications [BAC], and vessel walls). The distribution of staining degrees between the 3 diagnostic groups was calculated using the Fisher exact text (P ≤ .05) at the 4 regions. RESULTS: Significant differences in staining were observed mainly in the OL and PS and at the BAC. The most significant differences were detected in the PS and when comparing NP with 1 of the 2 irreversibly inflamed pulpal tissues (AIP or SIP). The inflamed tissues were then invariably stained more intensely than their normal counterparts at this location (S100A1, -A2, -A3, -A4, -A8, and -A9). In the OL, NP tissue was significantly stronger stained for S100A1, -A6, -A8, and -A9 compared with SIP and for S100A9 when compared with AIP. Differences between AIP and SIP in direct comparison were rare and were found only for 1 protein (S100A2) at the BAC. Also, at the vessel walls, only 1 statistical difference in staining was observed (SIP was stronger stained than NP for protein S100A3). CONCLUSIONS: The occurrence of proteins S100A1, -A2, -A3, -A4, -A6, -A8, and -A9 is significantly altered in irreversibly inflamed compared with normal dental pulp tissue at different anatomic localizations. Some members of S100 proteins obviously participate in focal calcification processes and pulp stone formation of the dental pulp.

Expression Profiling of S100 Proteins in Healthy and Irreversibly Inflamed Human Dental Pulps.

INTRODUCTION: Several S100 proteins have been shown to play an important role in the innate immune response to infection and in regenerative processes. However, they have scarcely been investigated during inflammation of the dental pulp. Therefore, in this study, we performed gene expression profiling of S100 proteins in healthy and inflamed human dental pulps. METHODS: Tissue samples of human dental pulps were used, including 15 clinically diagnosed as symptomatic irreversible pulpitis (SIP), 7 as asymptomatic irreversible pulpitis (AIP), and 19 as healthy pulp (HP). S100 gene expression levels were quantitatively evaluated for S100A1, -A2, -A3, -A4, -A6, -A7, -A8, -A9, -A10, -A11, -A13, -A14, and -A16 by the quantitative polymerase chain reaction technique. In order to monitor the status of inflammation and degradation of pulp tissues, IL-8, COX-2, and HMGB-1 gene expression was also analyzed with GAPDH serving as the reference gene. Differential expression rates for each target gene between SIP, AIP, and HP were evaluated by analysis of variance followed by the Bonferroni post hoc test. RESULTS: Significantly reduced gene expression levels could be detected in SIP compared with HP for S100A1, -A2, -A3, -A4, -A6, -A10, and -A13 and for HMGB-1, whereas the gene expression of S100A8 and -A14 and IL-8 were significantly increased. In AIP, significantly increased expression levels compared with HP were only detected for S100A14 and -A16 and IL-8, with other genes of interest not being altered. CONCLUSIONS: The present study revealed significant differences in gene expression profiles of S100 proteins comparing samples from healthy and inflamed dental pulp. More pronounced differences were observed for symptomatic than for asymptomatic pulpitis.

Narrowing of the radicular pulp space in coronally restored teeth.

OBJECTIVES: Narrowed radicular pulp spaces are frequently observed in teeth wearing extended restorations. The present study investigates whether the narrowing of particularly the radicular pulp space can be attributed to coronal restorations. MATERIALS AND METHODS: The study is based on an anonymized copy of the cone-beam computed tomography (CBCT) database from the Center of Dental Medicine of the University of Zurich. One hundred CBCT scans were selected out of 7317 data sets to match either a crowned (group A; n = 50) or a filled tooth (group B; n = 50) with a contralateral healthy, unrestored, and caries-free control tooth at the same position, respectively. Cross-sectional images were adjusted in the coronal, middle, and apical root third of each subjected tooth. Screenshots were taken in that position and analyzed. The area occupied by the pulp space was determined as percentage area of the whole root diameter on each cross section. The resulting values were compared between restored and control teeth. RESULTS: In both groups (crowned and filled teeth) and in all the three root thirds, the radicular pulp space was significantly narrower in the restored teeth compared to the control teeth. The strongest narrowing effect was observed in the coronal root third and it decreased towards the apical root third (both groups). CONCLUSIONS: Teeth with coronal restorations show within the limitations of the present study a significant narrowing of their radicular pulp space. CLINICAL RELEVANCE: The asserted narrowing could have a complicating effect if root canal treatment becomes necessary in those teeth.

Development and validation of an in vitro model for measurements of cervical root dentine permeability.

OBJECTIVES: The aim of this series of studies was the development and validation of a new model for evaluation of dentinal hypersensitivity (DH) therapies. MATERIALS AND METHODS: Roots from extracted human teeth were sealed with a flowable composite. In the cervical area, a 3-mm-wide circular window was ground through the seal 1 mm deep into dentine. The pulp lumen was connected to a reservoir of artificial dentinal fluid (ADF) containing protein, mineral salts and methylene blue. At increased pulpal pressure, the ADF released through the said window was collected in containers each with 20 ml of physiologic saline for a consecutive series of 30-min intervals and ADF concentration (absorption) was determined photometrically. The model was verified by three experiments. In experiment 1, the lower limit of quantification (LLoQ, coefficient of variation = 20 % and difference of 5 standard deviations (SD) from blank) of ADF in physiologic saline was determined by measuring the absorption of 15 dilutions of ADF in physiologic saline (containing 0.625 ng to 12.5 µg methylene blue/ml) photometrically for ten times. In experiment 2, long-term linearity of ADF perfusion/outflow was investigated using 11 specimens. The ADF released through the window was collected in the said containers separately for each consecutive interval of 30 min for up to 240 min. Absorption was determined and analysed by linear regression over time. In experiment 3, perfusion before (2×) and after single treatment according to the following three groups was measured: BisGMA-based sealant (Seal&Protect®), an acidic fluoride solution (elmex fluid®) and control (no treatment). RESULTS: In experiment 1, the LLoQ was 0.005 µg methylene blue/ml. In experiment 2, permeability was different within the specimens and decreased highly linearly with time, allowing the prediction of future values. In experiment 3, Seal&Protect® completely occluded dentinal tubules. elmex fluid® increased tubular permeability by about 30 % compared to control. CONCLUSIONS: A model comprising the use of artificial dentinal fluid was developed and validated allowing screening of therapeutic agents for the treatment of DH through reliable measurement of permeability of cervical root dentine. CLINICAL RELEVANCE: The described in vitro model allows evaluation of potential agents for the treatment of DH at the clinically relevant cervical region of human teeth.

Physicochemical and pulp tissue dissolution properties of some household bleach brands compared with a dental sodium hypochlorite solution.

INTRODUCTION: Many clinicians use household bleach to irrigate root canals. Sodium hypochlorite solutions are also available from dental suppliers. We compared physicochemical features of these products and investigated their impact on pulp tissue dissolution. METHODS: Six different brands of household bleach were bought from drugstores. These were compared with Chlor-XTRA and technical NaOCl solutions of controlled concentration and alkalinity regarding their chlorine content (wt% NaOCl), pH, alkaline capacity, osmolarity, surface tension (Wilhelmy plate method), and price. Bovine pulp tissue (n = 10 specimens per group) dissolution at 37°C by test and control solutions adjusted to 1.0% NaOCl was assessed. Reduction in tissue weight was compared between groups by one-way analysis of variance, followed by Bonferroni correction (P < .05). RESULTS: The pH of undiluted solutions ranged between 11.1 and 12.7. Batches of the same product differed in NaOCl content. No product contained more than an equivalent of 0.1 mol/L NaOH. One household bleach brand (Safeway Bleach Summit Fresh) was slightly alkalized; the other solutions under investigation were not. Osmolarity was similar between products. The surface tension of Chlor-XTRA and Safeway Bleach Summit Fresh was about half that of the other solutions. Tissue dissolution was statistically similar (P > .05) among all solutions. Price was about 100-fold higher per liter of Chlor-XTRA compared with household bleach. CONCLUSIONS: Other than its price, the Chlor-XTRA solution had no unique features. In contrast to an earlier report, reduced surface tension did not result in greater soft tissue dissolution by NaOCl.

Stabilizing sodium hypochlorite at high pH: effects on soft tissue and dentin.

INTRODUCTION: When sodium hypochlorite solutions react with tissue, their pH drops and tissue sorption decreases. We studied whether stabilizing a NaOCl solution at a high pH would increase its soft-tissue dissolution capacity and effects on the dentin matrix compared with a standard NaOCl solution of the same concentration and similar initial pH. METHODS: NaOCl solutions were prepared by mixing (1:1) a 10% stock solution with water (standard) or 2 mol/L NaOH (stabilized). Physiological saline and 1 mol/L NaOH served as the controls. Chlorine content and alkaline capacity of NaOCl solutions were determined. Standardized porcine palatal soft-tissue specimens and human root dentin bars were exposed to test and control solutions. Weight loss percentage was assessed in the soft-tissue dissolution assay. Three-point bending tests were performed on the root dentin bars to determine the modulus of elasticity and flexural strength. Values between groups were compared using one-way analysis of variance with the Bonferroni correction for multiple testing (α < .05). RESULTS: Both solutions contained 5% NaOCl. One milliliter of the standard and the stabilized solution consumed 4.0 mL and 13.7 mL of a 0.1-mol/L HCl solution before they reached a pH level of 7.5, respectively. The stabilized NaOCl dissolved significantly more soft tissue than the standard solution, and the pH remained high. It also caused a higher loss in elastic modulus and flexure strength (P < .05) than the control solutions, whereas the standard solution did not. CONCLUSIONS: NaOH-stabilized NaOCl solutions have a higher alkaline capacity and are thus more proteolytic than standard counterparts.