Human closed and open apex premolar teeth express different toll-like receptor.

BACKGROUND: The innate immune activation which promotes inflammation responses in the dental pulp tissue leads to the progression of dentin caries. Accordingly, toll-like receptors (TLRs) are key molecules of the innate immune system that identify pathogen-associated molecular patterns (PAMPs) on microorganisms and may have a critical role in a dental injury. Therefore, this study aimed to investigate the expression of TLR2, TLR3, and TLR4 in the human dental pulp of opened and closed apex teeth. METHODS: Human dental pulps were derived from the healthy opened and closed apex premolar, in which extraction was indicated for orthodontic reasons. The extraction of RNA was performed and the gene expression determined by real-time polymerase chain reaction (RT-PCR). The result from real-time PCR was confirmed using western blot analysis. RESULTS: Real-time PCR data analysis showed that the expression TLR2 and TLR4 were significantly increased in closed apex premolar teeth compared to open apex teeth, whereas TLR3 expression was not significantly different in these two groups (p < .05). CONCLUSION: The results of the present study suggested increased expression of TLR2 and TLR4 by the maturation of the apex, which may be due to the presence of microorganisms in the normal or destructed dental pulp tissue. Thus, identifying the expression of TLRs molecules in dental pulp tissue helps to develop a deeper knowledge of the immune responses in the oral cavity.

Apical Extrusion of Debris after Canal Preparation with Hand-Files Used Manually or Installed on Reciprocating Air-Driven Handpiece in Straight and Curved Canals.

INTRODUCTION: Apical debris extrusion (DE) subsequent to root canal instrumentation, is one of the most important causes of endodontic flare-ups. The aim of this study was to compare the amount of DE after root canal instrumentation using nickel-titanium (NiTi) hand files with step-back manual technique or installed on reciprocating handpiece. METHODS AND MATERIALS: This study was conducted on mesiobuccal (MB) roots of extracted maxillary first molars (n=20) and roots of mandibular premolars (n=20) that were randomly divided into two groups (n=20) according to the armamentarium used for canal preparation (air-driven reciprocating handpiece or hand instrumentation). In each group, the MB and premolar roots were prepared with the main apical sizes of 35 and 40, respectively. The extruded debris were collected and weighed. Finally, the mean dry weights were compared using ANOVA and t-test, and Tukey's Multiple Comparisons Procedures were used to determine the significant differences in amounts of DE. The level of significance was set at 0.05. RESULTS: Regardless of the type of teeth, the mean values of DE, were significantly lower in the handpiece group (P<0.0001). In addition, significantly lower amounts of DE was observed in premolars in similar group (P<0.001). However, this difference was not significant in MB roots of molars (P=0.20). CONCLUSION: Root canal preparation with reciprocating handpiece can lead to significantly lower debris extrusion than the manual step-back technique. In handpiece-prepared canals, the amount of extruded debris was significantly lower in premolar teeth.

In vitro detection of simulated apical root perforation with two electronic apex locators.

INTRODUCTION: The aim of this study was to evaluate the accuracy of two electronic apex locators (Smarpex and NovApex) in detecting apical perforation. MATERIALS AND METHODS: After access cavity preparations, the working length was determined by the first examiner before and after perforation with a stereomicroscope by introducing a K-file size 10 into the canal and size 25 K-file up to the perforation site, respectively. The specimens were embedded in a 17-well plastic box containing alginate. The root canals were irrigated with chlorhexidine 0.2% (CHX) through a 27-gauge needle. Two examiners measured the root canal length twice and the mean value was calculated. The data were analyzed using Kolmogorov-Smirnov and ANOVA tests. RESULTS: The results obtained with each Electronic Apex Locator were compared with the corresponding control length. The statistical analysis showed reliable accuracies in detecting the perforation site for the two experimental electronic apex locators (60% and 80% for NovApex and Smarpex, respectively). CONCLUSION: Although no significant difference was shown between Smarpex and NovApex, these results suggest that electronic apex locators can effectively and reproducibly detect root canal perforations.