Effect of Sterilization and Irrigating Solutions on Nanostructure Alteration of Ni-Ti Rotary Instruments in Endodontics: An Atomic Force Microscopic Study.

Aim: This study aimed to evaluate the effect of 5.25% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA) and sterilization on the nanostructural alteration of nickel titanium (Ni-Ti) rotary file systems in endodontics using the atomic force microscopy (AFM). Materials and Methods: The study was performed on four commercially available rotary Ni-Ti files: group I-Vortex Blue (Dentsply), group II-ProTaper Next (Dentsply), group III-Mtwo (VDW), and group IV-iRaCe (FKG). Each group was divided into four subgroups (n = 4), that is, subgroup A-control (new rotary file), subgroup B-subjected for five cycles of autoclave, subgroup C-immersed in 5.25% NaOCl for 5 minutes, and subgroup D-immersed in 17% EDTA solutions for 5 minutes. All the specimens were evaluated with AFM using roughness average (RA) and root-mean-square (RMS) values for surface roughness. Results: Among control groups, Vortex Blue showed the least RA and RMS values; the highest surface roughness was seen with Mtwo files. All the Ni-Ti rotary files showed a statistically significant (P <0.05) increase in surface hardness when subjected to autoclave and treatment with different irrigating solutions. In particular, 17% EDTA caused the highest surface deterioration in all the groups. Conclusion: AFM analysis revealed increased surface roughness values recorded for all the rotary files when treated with irrigating solutions and autoclave cycles.

Premixed Mineral Trioxide Aggregate Setting Reaction in Primary Molar Pulpotomies.

Purpose: To assess the setting of premixed mineral trioxide aggregate (NuSmile NeoPUTTY) when used as a pulpotomy agent in primary molars, restored in a single visit, and to compare the effect of overlying materials, including zinc oxide eugenol (ZOE), resin-modified glass ionomer cement (RMGIC) and stainless steel crowns (SSC), on the microhardness of the NeoPUTTY.
Methods: Forty-eight extracted primary molars were prepared with the standard pulpotomy technique. Approximately three mm of NeoPUTTY were placed on the pulpal floor of each tooth. The teeth were divided into four groups according to restorative material: (1) control group-none; (2) RMGIC; (3) ZOE; and (4) ZOE and SSC. Groups 2, 3 and 4 specimens were placed in artificially simulated oral cavity conditions. After 24 hours, all teeth were sectioned mesiodistally and polished. Microhardness was then measured in Knoop scales (HK) at one mm, two mm and three mm away from the NeoPUTTY-overlying material interface following the application of a 25-gf load force for 30 seconds at each site. One-way analysis of variance was used to compare the NeoPUTTY microhardness values between groups at each depth as well as between the three different depths within each group (P <0.05).
Results: No statistically significant differences in mean HK values (57.9 to 62.3 range) were found between groups at each depth, or between depths within each group (Group 1,P =0.328; Group 2, P =0.74; Group 3, P =0.293; Group 4, P =0.788).
Conclusion: The setting reaction of NeoPUTTY, as a function of microhardness, was not affected by the presence or type of overlying material used in a single-visit pulpotomy. This in vitro study found no evidence against the immediate restoration of primary molar pulpotomies done with NeoPUTTY.

C5a complement receptor modulates odontogenic dental pulp stem cell differentiation under hypoxia.

AIM: Alterations in the microenvironment change the phenotypes of dental pulp stem cells (DPSCs). The role of complement component C5a in the differentiation of DPSCs is unknown, especially under oxygen-deprived conditions. The aim of this study was to determine the effect of C5a on the odontogenic differentiation of DPSCs under normoxia and hypoxia. MATERIAL AND METHODS: Human DPSCs were subjected to odontogenic differentiation in osteogenic media and treated with the C5a receptor antagonist-W54011 under normal and hypoxic conditions (2% oxygen). Immunochemistry, western blot, and PCR analysis for the various odontogenic differentiation genes/proteins were performed. RESULTS: Our results demonstrated that C5a plays a positive role in the odontogenic differentiation of DPSCs. C5a receptor inhibition resulted in a significant decrease in odontogenic differentiation genes, such as DMP1, ON, RUNX2, DSPP compared with the control. This observation was further supported by the Western blot data for DSPP and DMP1 and immunohistochemical analysis. The hypoxic condition reversed this effect. CONCLUSIONS: Our results demonstrate that C5a regulates the odontogenic DPSC differentiation under normoxia. Under hypoxia, C5a exerts a reversed function for DPSC differentiation. Taken together, we identified that C5a and oxygen levels are key initial signals during pulp inflammation to control the odontogenic differentiation of DPSCs, thereby, providing a mechanism for potential therapeutic interventions for dentin repair and vital tooth preservation.

Prevalence of Radiographically Identifiable Dental Anomalies in Children and Association with Health Status.

Purpose: The purpose of this study was to describe the prevalence of radiographically identifiable developmental dental anomalies (DDA) in a university-based pediatric dental clinic and to assess for associations between DDA and health status. Methods: Retrospective data, obtained from the electronic dental records of a three-year pediatric patient cohort, were evaluated by two trained and calibrated examiners. Strict inclusion/ exclusion criteria were applied. A validated image quality grading system was used for radiograph assessment, and the physical status classification of the American Academy of Anesthesiology was utilized. A chi-square test and bivariate logistic regression were used for statistical analysis. The inter- and intraexaminer reliability was assessed using Cohen's Kappa. Results: A total of 1,478 subjects (69 percent medically healthy) were enrolled. DDA were identified in 25 percent of the subjects, with hyperdontia, hypodontia, and microdontia being more common. A statistically significant association was found between the presence of DDA and health status (P<0.001) and between DDA and asthma (P=0.035). Patients with systemic disturbances showed 2.12 times greater odds of having DDA (P<0.001, 95 percent confidence interval equals 1.7-2.7). Conclusions: The prevalence of developmental dental anomalies was high, with one in four patients affected. DDA in number were the most common. Patients with systemic disturbances had greater odds of having DDA.

Factors associated with moderate sedation attendance at a university-based pediatric dental clinic.

PURPOSE/OBJECTIVES: To evaluate patient attendance for moderate sedation (MS) at a university-based pediatric dental clinic; to identify factors with negative impact on MS being completed and to assess for associations between no-show appointments and patient variables METHODS: The electronic health records of patients scheduled for MS appointments in a 22-month period were assessed by a single investigator. Demographic and clinical data related to appointment attendance and MS procedure performance were collected and statistically analyzed using chi-square, Spearman's rho correlation tests, and logistic regression (p < 0.05) RESULTS: A total of 618 scheduled MS appointments were included. The MS appointment no-show-rate was 17.1 percent. Appointment confirmation (p = 0.001) and dmft score ≥ 9 (p = 0.039) had positive correlation with attendance, while "no-shows" history (p = 0.024) and longer waiting time (p = 0.040) had negative impact on attendance. About 20% of attended MS were not completed, with main reasons of airway risk (32.3%), ongoing illness (28.4%), and violation of NPO guidelines (21.5%). Race, ethnicity, language spoken, child's behavior, and distance traveled had no significant impact on attendance CONCLUSION: Interventions to decrease non-attendance rates should target patients who are unconfirmed, have a history of no-show appointments, and are scheduled well before the sedation appointment.

A Randomized Controlled Trial Comparing the Success of Mineral Trioxide Aggregate and Ferric Sulfate as Pulpotomy Medicaments for Primary Molars.

Purpose: To evaluate and compare the clinical and radiographic performance of a new type of mineral trioxide aggregate (MTA, NuSmile® NeoMTA®) and ferric sulfate (FS) as pulpotomy medicaments for primary molars over 12 months.
Methods: Fifty participants (25 per group) were enrolled, according to specific inclusion criteria. Each participant received a single primary molar pulpotomy either with MTA or FS, depending on random digit table method allocation. Fifteen pediatric dental residents completed all pulpotomies, supervised by specialist faculty. Two calibrated examiners performed outcome assessments according to standardized criteria. Every six months, the study teeth were evaluated clinically and every 12 months radiographically. The inter- and intraexaminer reliability was assessed using Cohen's kappa, and the chi-square test was used for statistical analysis.
Results: At six months, 42 participants (21 in each group) returned for evaluation. The FS group showed 95.2 percent clinical success compared to 100 percent for the MTA group. At the 12-month clinical and radiographic evaluation, the return sample consisted of 29 participants (14 in the MTA group, 15 in the FS group). FS had 86.6 percent clinical success and 60 percent radiographic success, while MTA showed 100 percent clinical and radiographic success. At 12 months, MTA showed a statistically significantly higher success rate compared to FS (P = 0.008). Examiner reliability was excellent with a kappa score greater than 0.88.
Conclusion: At 12 months, MTA showed superior success as a pulpotomy medicament in primary molars compared to FS.

Success of Biodentine and Ferric Sulfate as Pulpotomy Materials in Primary Molars: A Retrospective Study.

OBJECTIVE: To determine the clinical and radiographic success of Biodentine® (BD) and Ferric Sulfate (FS) as primary molar pulpotomy materials and to compare their outcomes. STUDY DESIGN: Retrospective data was obtained from the electronic health records (EHR) of a university-based pediatric dental clinic. Participants were enrolled according to specified inclusion and exclusion criteria. Two trained and calibrated examiners evaluated the EHR using validated criteria for clinical and radiographic outcomes. Study data was numerically coded and analyzed. Cohen's Kappa and Chi-square tests were used (p<0.05). RESULTS: Eighty-three participants (62.7% females, age range two to eight years, average age of 4.5 years) with 102 pulpotomies were enrolled. FS was used in 78% (n=79) and BD in 22% (n=23) of the cases. Follow-up periods ranged from six to 36 months (mean of 17 months). BD showed 100% clinical and radiographic success, while FS demonstrated 84% clinical and 70% radiographic success. The two groups were compared at one year with no statistically significant differences. At 18 months, BD outperformed FS clinically (p=.012) and radiographically (p=.001). Intra-rater and inter-rater agreement were κ>0.88. CONCLUSIONS: Both materials can be recommended for clinical practice, however BD may be the preferred choice for its better outcomes at 18 months.

Effect of Overlying Material on Final Setting of Biodentine ® in Primary Molar Pulpotomies.

Purpose: The purpose of this study was to evaluate and compare in vitro the effect of overlying materials, including zinc oxide eugenol (ZOE), resin-modified glass ionomer cement (RMGIC), and stainless steel crowns (SSC) cemented with glass ionomer cement (GIC), on the setting of Biodentine ® (BD) used as a pulpotomy agent in primary molars that were restored definitively in a single visit. Methods: Forty extracted primary molars were prepared to replicate pulpotomy procedures. The teeth were randomly allocated to four restorative groups: (1) BD, ZOE, SSC; (2) BD, RMGIC, SSC; (3) BD, SSC; (4) BD only (control). All samples were incubated for 24 hours, sectioned mesial-distally, and polished. BD setting was measured as a function of Knoop hardness value (HK) using a Leco Microhardness Tester. Each sample was tested in three zones with 50 gf load force and 30 seconds dwell time and at one, two, and three mm distance from the BD-material interface. A one-way analysis of variance was used to determine statistical significance between groups (P<.05). Results: There was no statistically significant difference between the mean HK value among the four groups and three zones. Conclusions: Overlying materials, including zinc oxide eugenol, resin-modified glass ionomer, and stainless steel crowns cemented with glass ionomer cement, showed no effect on the BD final set. This in vitro study found no evidence against immediate definitive restoration of Biodentine ® pulpotomies.

Poly(Adenosine Phosphate Ribose) Polymerase 1 Inhibition Enhances Brain-derived Neurotrophic Factor Secretion in Dental Pulp Stem Cell-derived Odontoblastlike Cells.

INTRODUCTION: The nuclear enzyme poly(adenosine phosphate ribose) polymerase 1 (PARP-1) has been implicated in the maintenance and differentiation of several stem cells. The role of PARP-1 in dental pulp stem cell (DPSC) differentiation, especially in the context of its ability to modulate nerve regeneration factors, has not been investigated. Regeneration of neuronal components in pulp tissue is important for the assessment of tooth vitality. Brain-derived neurotrophic factor (BDNF) is known to play an integral signaling factor during nerve regeneration. In this study, we identified the role of PARP-1 in the modulation of BDNF in DPSC differentiation into odontoblastlike cells. METHODS: Human DPSCs were prepared from healthy molars and cultured in regular and osteogenic media treated with PARP-1 antagonist and PARP-1 exogeneous protein. Polymerase chain reaction and immunohistochemistry analysis for BDNF and various differentiation markers were performed. RESULTS: Our polymerase chain reaction results showed that differentiated cells show odontoblastlike properties because they express odontogenic markers such as dentin sialophosphoprotein and dentin matrix protein 1. Both PARP-1 inhibitor and protein did not affect odontogenic differentiation and proliferation because the number of the differentiated cells was unaffected, and the expression of dentin sialophosphoprotein and dentin matrix protein 1 was not significantly changed. There is the possibility that PARP-1 treatment induces DPSCs into the unique cell lineage. Some differentiated cells show a very unique morphology with large irregular cytoplasm and an oval nucleus. Moreover, PARP-1 inhibition significantly increased BDNF secretion in DPSC-derived odontoblastlike cells. This observation was also confirmed by immunohistochemistry. CONCLUSIONS: Taken together, our results indicate PARP-1 as a negative regulator in BDNF secretion during odontogenic DPSC differentiation, showing its potential application for translational nerve regeneration strategies to improve dental pulp tissue vitality assessments.

Effects of substrate stiffness on dental pulp stromal cells in culture.

Dental pulp stromal cells (DPSCs) can be differentiated down lineages known to either express bone or dentin specific protein markers. Since the differentiation of cells can be heavily influenced by their environment, it may be possible to influence the osteogenic/odontogenic potential of DPSCs by modulating the mechanical properties of substrate on which they are grown. In this study, human DPSCs were grown with and without hydroxyapatite (HA) microparticles on a range of substrates including fibronectin-coated hydrogels and glass substrates, which represented an elastic moduli range of approximately 3 kPa-50 GPa, over a 21-day period. Alkaline phosphatase activity, osteopontin production, and mineralization were monitored. The presence of HA microparticles increased the relative degree of mineralized matrix produced by the cells relative to those in the same substrate and media condition without the HA microparticles. In addition, cultures with cells grown on stiffer substrates had higher ALP activity and higher degree of mineralization than those grown on softer substrates. This study shows that DPSCs are affected by the mechanical properties of their underlying growth substrate and by the presence of HA microparticles. In addition, relatively stiff substrates (>75 kPa) may be required for significant mineralization of these cultures. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1789-1797, 2018.

Wear characteristics and inhibition of enamel demineralization by resin-based coating materials.

In this study, wear and inhibition of enamel demineralization by resin-based coating materials were investigated. Seven commercially available coating materials, with and without fillers, were used. A mechanical wear test was performed, and the specimens were then examined with a scanning electron microscope. Hardness and elastic modulus measurements for each material were obtained by nanoindentation testing. Thin layers of each material were applied on human enamel surfaces, which were subjected to alternating immersion in demineralizing and remineralizing solutions. The inhibition ability of enamel demineralization adjacent to the coating was estimated with depth-dependent mechanical properties using the nanoindentation test. The non-filled coating material showed significantly lower hardness, lower elastic modulus, and higher weight loss. There were no significant differences in weight loss among the six filled coating materials. After the alternating immersion protocol, the enamel specimens having application of coating materials with ion-releasing ability were harder than those in the other groups in some locations 1-11 µm from the enamel surface and within 300 µm from the edge of the coating materials. In conclusion, clinical use of the resin-based coating materials with ion-releasing ability may prevent demineralization of exposed enamel adjacent to the coating during treatment.

Micro-Computed Tomography of Tooth Volume Changes Following Post Removal.

PURPOSE: To measure tooth volume change before and after post removal using micro-CT and to compare the difference among various combinations of prefabricated post and cement systems. MATERIALS AND METHODS: Forty-eight extracted maxillary anterior teeth and mandibular canines were sectioned 13 mm from the apex. Root canals were properly instrumented. Preparations were filled with gutta percha using lateral condensation. Post space was prepared with a touch and heat device, leaving 5 mm of gutta percha from the apex. Specimens were scanned with micro-CT to establish objective baseline volume and divided into two groups of post systems: stainless steel (SS) ParaPost and glass-fiber reinforced composite (FRC) post. Half the posts for each group were cemented with Ketac Cem radiopaque glass-ionomer cement, and the other half with SpeedCEM dual-curing resin cement. The posts and residual cement were removed by the same operator, using the ultrasonic vibration technique under an endodontic operating microscope. The remaining tooth root structure was scanned again using micro-CT with volume reported (mm3 ). The statistical difference between the combination of posts and cements was measured using the Kruskal-Wallis ANOVA test (α = 0.001). The independent variables were evaluated separately using post hoc Tukey examination to determine which groups resulted in a statistically significant difference. RESULTS: There was a statistical difference of tooth root volume change among the groups. Post hoc exam revealed a statistically significant difference in tooth root volume change between group 1 (SS + GI) and the other groups (α = 0.0002). CONCLUSION: Compared to other post and cement combinations, serrated parallel-sided SS posts cemented with GI cement had the most tooth root structure loss upon post removal using the ultrasonic vibration technique.

Exosomes as biomimetic tools for stem cell differentiation: Applications in dental pulp tissue regeneration.

Achieving and maintaining safe and reliable lineage specific differentiation of stem cells is important for clinical translation of tissue engineering strategies. In an effort to circumvent the multitude of problems arising from the usage of growth factors and growth factor delivery systems, we have explored the use of exosomes as biomimetic tools to induce stem cell differentiation. Working on the hypothesis that cell-type specific exosomes can trigger lineage-specific differentiation of stem cells, we have evaluated the potential of exosomes derived from dental pulp cells cultured on under growth and odontogenic differentiation conditions to induce odontogenic differentiation of naïve human dental pulp stem cells (DPSCs) and human bone marrow derived stromal cells (HMSCs) in vitro and in vivo. Results indicate that the exosomes can bind to matrix proteins such as type I collagen and fibronectin enabling them to be tethered to biomaterials. The exosomes are endocytosed by both DPSCs and HMSCs in a dose-dependent and saturable manner via the caveolar endocytic mechanism and trigger the P38 mitogen activated protein kinase (MAPK) pathway. In addition, the exosomes also trigger the increased expression of genes required for odontogenic differentiation. When tested in vivo in a tooth root slice model with DPSCs, the exosomes triggered regeneration of dental pulp-like tissue. However, our results indicate that exosomes isolated under odontogenic conditions are better inducers of stem cell differentiation and tissue regeneration. Overall, our results highlight the potential exosomes as biomimetic tools to induce lineage specific differentiation of stem cells. Our results also show the importance of considering the source and state of exosome donor cells before a choice is made for therapeutic applications.

Idiosyncratic Presentation of Cemento-Osseous Dysplasia - An in Depth Analysis Using Cone Beam Computed Tomography.

Bone dysplasias comprise of a condition where the normal bone is replaced with fibrous tissue. Periapical Cemento-Osseous Dysplasia (PCOD) is a benign fibro-osseous condition where bone tissue is supplanted with fibrous tissue and cementum-like material. This condition affects mostly mandibular anterior region and rarely occurs in the maxilla. PCOD is seen above 30 years of age and has slight female predilection. Generally the teeth related to such lesions appear to be vital and are usually asymptomatic. These lesions are mostly seen during routine radiographic examination whose presentation may vary from complete radiolucency to dense radiopacity. The advent of Cone Beam Computed Tomography (CBCT) has brought a massive change in the field of dentistry which has become an important tool for diagnosis. Hence we hereby present an unusual case of cemento-osseous dysplasia in an unfamiliar location with an atypical presentation. The shape of the pathology was completely idiosyncratic and different from an orthodox lesion of COD, as the lesion was observed to grow out of the palatal surface with a prominent palatal expansion. This case highlights the importance of CBCT in radiographic diagnosis and in evaluating the characteristics of such lesion, which present with high diagnostic dilemma.

Various forms of tobacco usage and its associated oral mucosal lesions.

BACKGROUND: To study the various forms of tobacco usage and its associated oral mucosal lesions among the patients attending Vishnu Dental College Bhimavaram. MATERIAL AND METHODS: An observational cross-sectional study was conducted in a total of 450 patients who were divided into three groups based upon type of tobacco use, as Group-1 Reverse smoking, Group-2 Conventional smoking, Group-3 Smokeless tobacco group and each group consists of 150 subjects. RESULTS: Reverse smoking was observed to be more prevalent among old females with smoker's palate and carcinomatous lesions being the most common. Conventional smoking was observed more in male patients with maximum occurrence of leukoplakia and tobacco associated melanosis. Smokeless tobacco habit was predominantly seen in younger males. Habit specific lesions like tobacco pouch keratosis, Oral Submucous Fibrosis (OSMF), Quid induced lichenoid reaction were noticed in smokeless tobacco habit group except for erythroplakia which was noticed only in conventional smoking group and it was not significant statistically. CONCLUSIONS: In the present study it was found that the usage of reverse smoking habit was most commonly seen in females and this habit is practiced in and surrounding areas of Bhimavaram with more occurrence of carcinoma compared to conventional smoking and smokeless tobacco. KEY WORDS: Tobacco, reverse smoking, conventional smoking, smokeless tobacco, carcinoma.

Identifying risk groups for osteoporosis by digital panoramic radiography.

BACKGROUND: Osteoporosis is a disease characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to bone fragility, and enhanced susceptibility to fractures. Dental radiographs, especially panoramic images, have been used to predict bone mineral density. A number of indices, (mandibular cortical index [MCI], mandibular cortical width [MCW], and panoramic mandibular index [PMI]) have been developed to assess and quantify the quality of mandibular bone mass and to observe the signs of resorption. OBJECTIVES: The objectives of the study were to assess mental index (MI), MCW index, and PMI with bone density in identifying risk group for osteoporosis and also to investigate influence of age and gender on MI, MCI, and PMI. MATERIALS AND METHODS: After obtaining consent, details regarding age, gender, systemic health status, and oral parafunctional habits were recorded in each patient. Then a digital panoramic radiograph was taken. The image thus obtained was subjected to calibrations and morphometric analysis using Digora version 2.7. The obtained values of indices were compared with the mean values of indices, to evaluate subjects whether they are prone to osteoporosis or not. The obtained information was subjected to statistical analysis for the significance of the parameters. RESULTS: Data analysis showed that calibration indices were highly significant in the assessment of risk group for osteoporosis than noncalibration index. The subjects at a higher risk for development of osteoporosis were old-aged adults with higher prevalence being reported in women compared to male subjects. CONCLUSION: In conclusion, our results suggest that higher percentage of subjects with undetected decreased bone mineral density may be identified based on trained general dental practitioners analyses of their panoramic radiographs using simple screening analytical calibration MI and MCI.

Interferon Gamma-treated Dental Pulp Stem Cells Promote Human Mesenchymal Stem Cell Migration In Vitro.

INTRODUCTION: Chronic inflammation disrupts dental pulp regeneration by disintegrating the recruitment process of progenitors for repair. Bone marrow-derived mesenchymal stem cells (BM-MSCs) share the common features with dental pulp stem cells (DPSCs). The aim of the study was to investigate the migration of BM-MSCs toward DPSCs in response to inflammatory chemoattractants. Additionally, our studies also delineated the signaling mechanisms from BM-MSCs in mediating the proliferation and differentiation of DPSCs in vitro. METHODS: Human DPSCs and BM-MSCs between passages 2 and 4 were used and were grown in odontogenic differentiation medium. Mineralization was determined by alizarin red staining analysis. Migration was assessed using crystal violet staining in cells grown in Boyden chamber Transwell inserts (Corning Inc Foundation, Tewksbury, MA). The mineralization potential of DPSCs was evaluated using alkaline phosphatase activity assay. Real-time polymerase chain reaction analysis was performed to assess the gene expression profile of chemokine (C-X-C motif) ligand (Cxcl) 3, 5, 6, 10, 11, 12, 14, and 16; stromal cell-derived factor (SDF) α; vascular endothelial growth factor; and fibroblast growth factor. RESULTS: Interferon gamma (FN-γ) treatment significantly abrogated the differentiation potential of DPSCs as shown by using alizarin red and alkaline phosphatase activity analysis. An increase in the migration of BM-MSCs was documented when cocultured with IFN-γ-treated DPSCs. RNA expression studies showed an increase in the levels of Cxcl6 and Cxcl12 in BM-MSCs when cocultured with IFN-γ-treated DPSCs. Additionally, an up-regulation of proangiogenic factors vascular endothelial growth factor and fibroblast growth factor were observed in DPSCs exposed to IFN-γ. CONCLUSIONS: Our findings indicate that inflamed IFN-γ-treated DPSCs release factors (presumably Cxcl6 and 12) that contribute to the homing of MSCs. This model might provide a potential research tool for studying MSC-DPSC cross talk and for future studies involving the recruitment and sustainability of progenitor stem cells sustaining the inflammatory cascade to treat pulp inflammation.

Mechanical changes in human dental pulp stem cells during early odontogenic differentiation.

INTRODUCTION: Cell adhesion and migration in bioactive scaffolds require actin cytoskeleton remodeling and focal adhesion formation. Additionally, human dental pulp stem cells (hDPSCs) undergo several changes in their mechanical properties during odontogenic differentiation. The effect of factors essential for odontogenesis on actin stress fiber elasticity and focal adhesion formation is not known. METHODS: Live hDPSCs cultured in odontogenic media were imaged for cytoskeleton changes using an atomic force microscope. The Young's modulus (kPa) of the cytoskeleton was recorded as a function of culture medium for 10 days. Focal adhesion formation was assessed using immunofluorescence. Cultured hDPSCs were incubated with a monoclonal vinculin antibody, and filamentous actins were visualized using 0.5 µmol/L phalloidin. RESULTS: Cytoskeletal elasticity significantly increased in response to odontogenic media. Both the number and physical size of focal adhesions in hDPSCs also increased. Up-regulation of vinculin expression was evident. The increase in the formation of focal adhesions was consistent with actin remodeling to stress fibers. CONCLUSIONS: Our findings suggest that hDPSCs firmly attach to the glass substrate in response to odontogenic media. Successful regeneration of pulp-dentin tissue using biomimetic scaffolds will likely require cell-extracellular matrix interactions influenced by biochemical induction factors.

Chronic inflammation and angiogenic signaling axis impairs differentiation of dental-pulp stem cells.

Dental-pulp tissue is often exposed to inflammatory injury. Sequested growth factors or angiogenic signaling proteins that are released following inflammatory injury play a pivotal role in the formation of reparative dentin. While limited or moderate angiogenesis may be helpful for dental pulp maintenance, the induction of significant level of angiogenesis is probably highly detrimental. Hitherto, several studies have addressed the effects of proinflammatory stimuli on the survival and differentiation of dental-pulp stem cells (DPSC), in vitro. However, the mechanisms communal to the inflammatory and angiogenic signaling involved in DPSC survival and differentiation remain unknown. Our studies observed that short-term exposure to TNF-α (6 and 12 hours [hrs]) induced apoptosis with an upregulation of VEGF expression and NF-κB signaling. However, long-term (chronic) exposure (14 days) to TNF-α resulted in an increased proliferation with a concomitant shortening of the telomere length. Interestingly, DPSC pretreated with Nemo binding domain (NBD) peptide (a cell permeable NF-κB inhibitor) significantly ameliorated TNF-α- and/or VEGF-induced proliferation and the shortening of telomere length. NBD peptide pretreatment significantly improved TNF-α-induced downregulation of proteins essential for differentiation, such as bone morphogenic proteins (BMP)-1 & 2, BMP receptor isoforms-1&2, trasnforming growth factor (TGF), osteoactivin and osteocalcin. Additionally, inhibition of NF-κB signaling markedly increased the mineralization potential, a process abrogated by chronic exposure to TNF-α. Thus, our studies demonstrated that chronic inflammation mediates telomere shortening via NF-κB signaling in human DPSC. Resultant chromosomal instability leads to an emergence of increased proliferation of DPSC, while negatively regulating the differentiation of DPSC, in vitro.

Effect of coating on properties of esthetic orthodontic nickel-titanium wires.

OBJECTIVE: To determine the effect of coating on the properties of two esthetic orthodontic nickel-titanium wires. MATERIALS AND METHODS: Woowa (polymer coating; Dany Harvest) and BioForce High Aesthetic Archwire (metal coating; Dentsply GAC) with cross-section dimensions of 0.016 × 0.022 inches were selected. Noncoated posterior regions of the anterior-coated Woowa and uncoated Sentalloy were used for comparison. Nominal coating compositions were determined by x-ray fluorescence (JSX-3200, JOEL). Cross-sectioned and external surfaces were observed with a scanning electron microscope (SEM; SSX-550, Shimadzu) and an atomic force microscope (SPM-9500J2, Shimadzu). A three-point bending test (12-mm span) was carried out using a universal testing machine (EZ Test, Shimadzu). Hardness and elastic modulus of external and cross-sectioned surfaces were obtained by nanoindentation (ENT-1100a, Elionix; n  =  10). RESULTS: Coatings on Woowa and BioForce High Aesthetic Archwire contained 41% silver and 14% gold, respectively. The coating thickness on Woowa was approximately 10 µm, and the coating thickness on BioForce High Aesthetic Archwire was much smaller. The surfaces of both coated wires were rougher than the noncoated wires. Woowa showed a higher mean unloading force than the noncoated Woowa, although BioForce High Aesthetic Archwire showed a lower mean unloading force than Sentalloy. While cross-sectional surfaces of all wires had similar hardness and elastic modulus, values for the external surface of Woowa were smaller than for the other wires. CONCLUSIONS: The coating processes for Woowa and BioForce High Aesthetic Archwire influence bending behavior and surface morphology.