MicroRNA Expression Profiles in External Cervical Resorption.

INTRODUCTION: External cervical resorption (ECR) has been challenging for its diagnosis, prevention, and treatment. Its etiology and pathogenesis are largely unknown. This study characterized microRNA (miRNA) expression patterns of human tissues from ECR lesions and identified potential messenger RNA targets and pathways. METHODS: Granulomatous tissues from ECR (n = 5) and their adjacent nonaffected asymptomatic gingival connective tissues (n = 5) were collected. Similarly, chronic periodontitis (CP) and control samples were collected (n = 3). Quantitative reverse transcription polymerase chain reaction array analysis compared the expression profiles of 88 miRNAs between diseases. Differentially expressed miRNAs were identified using the Student t test. Bioinformatics for messenger RNA (miRWalk) and KEGG pathway analyses were performed to identify predicted target genes and biological/cellular functions and signaling pathways. RESULTS: Three miRNAs (miR-20a-5p, miR-210-3p, and miR-99a-4p) were significantly down-regulated and 1 miRNA (miR-122-5p) was significantly up-regulated in ECR (P < .05). One up-regulated and 1 down-regulated miRNA reached the significance threshold in CP. A comparison of miRNA expression in ECR and CP identified 3 differentially expressed miRNAs, indicating differences in disease pathobiology. Inflammation-associated Wnt, PI3K-Akt, mitogen-activated protein kinases signaling, and bone formation-associated transforming growth factor beta pathways were identified and predicted to be modulated by differentially expressed miRNAs in both ECR and CP. Biological processes unique to each disease entity were identified, such as T- and B-cell receptor signaling pathways, osteoclast differentiation, and extracellular matrix-receptor interaction for CP. Glycosaminoglycan biosynthesis, mineral absorption, and insulin signaling pathways for ECR were identified. CONCLUSIONS: This proof-of-principle in vivo study indicated that ECR has both common and unique miRNA expression profiles in comparison with CP, which are predicted to target genes regulating inflammation, immunity, and metabolism of mineralized tissues.

Nominal Size and Taper Analysis of Novel Metallurgy NiTi Files.

OBJECTIVE: The aim of this investigation was to assess the nominal tip diameter, taper and true pilot tip length of three nickel-titanium (NiTi) rotary files before and after use. METHODS: Three brands of NiTi files of size 25.08 were evaluated: ProTaper Uni-versal (Dentsply Tulsa Specialties, Tulsa, USA), Channels PT (Insight Endo for Henry Schein, Melville, NY) and ProTaper Gold (Dentsply Tulsa Specialties), with ten files from each brand (total n=30). Scanning electron microscope (SEM) images of the files at 50x magnification were acquired before and after the files were used on endodontic training blocks, and the images were analysed by two independent investigators using ImageJ software. The nominal tip diameter (D0), taper and true pilot tip length (measured as the distance from the advertised diameter size of the file to the tip of the file) were recorded for each file and were analysed for statistical differences using repeated measures of analysis of variance (r-ANOVA) and Tukey's post-hoc test (P<0.05). RESULTS: The marginal means of the nominal size showed statistically significant differences between brands of the same size; statistically significant differences were also observed between the advertised sizes and the actual sizes (P<0.001). The mean taper values showed statistically significant differences from the advertised (p<0.001) sizes, except for the ProTaper Gold (P=0.023) group. The changes in the true pilot tip length before and after use were not statistically significant (P>0.05). The pilot tip lengths varied between brands. CONCLUSION: All nominal tip diameters and most taper sizes of the analysed brands show statistically significant differences from the nominal sizes advertised by the manufacturers. The differences in true pilot tip lengths between brands indicate a current lack of standardization.

Effect of endodontic instrument taper on post retention.

The purpose of this study was to evaluate the effect of various tapers of canal preparations on the retention of posts. Ninety human central or lateral mandibular incisors were prepared by removing the clinical crown at the CEJ and instrumenting the canals with instruments of varying tapers. The groups comprising 10 teeth each were divided as follows: Taper 0.02 Ni-Ti hand files (control), Taper 0.04 ProFile Series 29, Taper 0.06 ProFile Series 29, Taper 0.08 ProFile GT Rotary, Taper 0.10 ProFile GT Rotary, Taper 0.12 ProFile GT Rotary, Taper 0.08* ProFile GT Rotary 0.08 taper with #50/.12 taper in coronal third, Taper 0.10* ProFile GT Rotary 0.10 taper with #50/.12 taper in coronal third, Taper 0.12* ProFile GT Rotary 0.12 taper with #50/.12 taper in coronal third. Canals were filled with gutta-percha and AH 26 sealer using lateral condensation. Gutta-percha was removed with a heated 5/7 plugger until a level of 5 mm of gutta-percha was left in the apical segment of the root. Post channel preparation was made to the appropriate size with minimal change in canal shape with the Premier IntegraPost drill, and the corresponding IntegraPost was cemented with 3M Vitremer cement. The roots were fixed in copper rings with mounting plaster and mounted on an Instron TT machine. The posts were subjected to gradually increasing vertical tensile force until dislodgment of the post occurred. Force (lb) required to dislodge the post was obtained for each tooth, and the average force of the groups was compared using a one-way ANOVA with Tukey's multiple comparisons. The highest resistance to dislodgment was obtained with Taper 0.04 (79.10 +/- 10.73), whereas the lowest was obtained by the Taper 0.02 (18.70 +/- 13.44). No statistical difference was found between six of the groups: Taper 0.08*, Taper 0.10, Taper 0.12*, Taper 0.10*, Taper 0.12, and Taper 0.06. Taper 0.08 was statistically inferior to Taper 0.04 but not Taper 0.02. The 0.04 taper seems to be the best taper for maximal resistance to post dislodgment.

Potential correlation between statins and pulp chamber calcification.

INTRODUCTION: 3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) are the first-line pharmaceuticals for the prevention and treatment of dyslipidemia. A recent investigation has shown that statins induced odontoblastic differentiation of dental pulp stem cells. Statins enhance the differentiation of human dental pulp cells by up-regulating mineralization nodules and odontogenic markers. This study tested the hypothesis that the systemic administration of statins results in increased dental pulp calcification. METHODS: This retrospective case-control study used digital bitewing radiographs of mandibular molars. Subjects (N = 90) aged ≥60 years were assigned to either test (n = 45) or control (n = 45) groups based on the systemic use of statins. The dimensions of the pulp chambers were measured using a standardized method for height and mesiodistal distances. The chi-square test was used to analyze the data. Multiple linear regression model analysis was performed to explore the association between statin intake and pulp calcification. RESULTS: Three of the 45 mandibular molars in the test group exhibited almost complete pulp chamber obliteration. There was a significant reduction in pulp chamber height ratio shown in the statin group compared with the control group (P < .0001). When the mesiodistal width was compared between the 2 groups, there was no significant difference (P = .3730). CONCLUSIONS: The significant increase of calcification and loss of vertical height of the pulp chamber observed in mandibular molars in patients on statin medication indicated a possible increased odontoblastic activity. Therefore, systemic statins could be a contributing factor for pulp chamber calcification.