Effect of Bacterial Lipopolysaccharide Contamination on Gutta Percha- versus Resilon-Induced Human Monocyte Cell Line Toxicity.

OBJECTIVES: Cytotoxic effects of obturation materials were tested in presence and absence of endotoxin on human monocytes in vitro. MATERIALS AND METHODS: Human monocytes from THP-1 cell line were cultured. Three millimeters from the tip of each Resilon and gutta percha points were cut and directly placed at the bottom of the culture wells. Cultured cells were exposed to gutta percha (groups G1 and G2) and Resilon (R1 and R2). Ten µg/ml bacterial lipopolysaccharide (LPS) was added to the culture wells in groups G1 and R1. Positive control included the bacterial LPS without the root canal filling material and the negative control contained the cells in culture medium only. Viability of cells was tested in all groups after 24, 48, and 72 hours using the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay for at least 3 times to obtain reproducible results. Optical density values were read and the data were analyzed using three-way ANOVA and post hoc statistical test. RESULTS: The results showed that cells in G2 had the lowest rate of viability at 24 hours, but the lowest rate of viable cells was recorded in G1 at 48 and 72 hours. The effect of LPS treatment was not statistically significant. Resilon groups showed cell viability values higher than those of gutta percha groups, although statistically non-significant (P=0.105). Cell viability values were lower in gutta percha than Resilon groups when LPS-treated and LPS-untreated groups were compared independently at each time point. CONCLUSION: It could be concluded that none of the tested root canal filling materials had toxic effects on cultured human monocyte cells whether in presence or absence of LPS contamination.

Er,Cr:YSGG laser influence on microleakage of class V composite resin restorations.

One of the most challenging issues following restoration is microleakage. The aim of this study was to investigate the effects of Er,Cr:YSGG laser with and without acid etching on microleakage of class V composite restorations. A total of 68 human intact premolars were selected, disinfected, and randomly allocated to four experimental groups (n = 16) as well as positive and negative controls (n = 2 each). Dimensionally, similar class V cavities were prepared on buccal surface of each tooth under the following conditions: group 1, bur cavity preparation and chemical etching (BE); group 2, bur cavity preparation and Er,Cr:YSGG laser conditioning (BLc); group 3, Er,Cr:YSGG laser cavity preparation and chemical etching (LE); and group 4, Er,Cr:YSGG laser cavity preparation and Er,Cr:YSGG laser conditioning (LLc). All samples were restored with composite. The teeth were sealed and immersed in 1 % methylene blue for 48 h before being sectioned. The microleakage evaluation was done under a stereomicroscope (×20). The leakage scores were recorded and Kruskal-Wallis and Mann-Whitney tests were used for statistical evaluations. The highest microleakage score was seen in gingival margins of group 4 (LLc) and the lowest in occlusal margins of group 3 (LE). The overall difference in leakage scores among the groups was statistically significant (p < 0.001) with gingival margins showing a significantly higher score than its occlusal counterparts (p < 0.001). It was noted that less microleakage could be achieved when cavities were prepared by laser compared to bur. In addition, less microleakage was seen in acid-etched cavities than laser-conditioned counterparts.

Evaluation of the root canal morphology of mandibular second premolars in an Iranian population.

OBJECTIVE: A detailed knowledge of root canal anatomy is a prerequisite for successful endodontic treatment. Such information is highly dependent upon the ethnicity of the population of interest. Lack of sufficient national information concerning internal anatomy can lead clinicians to increase their rate of treatment success. The aim of this study was to evaluate external root morphology and root canal anatomy of mandibular second premolars in an Iranian population. MATERIALS AND METHODS: Two hundred seventeen human extracted mandibular second premolars were selected. Each tooth was radiographed both mesiodistally and buccolingually. Then, access cavities were prepared for each tooth and root canal negotiated before being immersed into 1% fuchsine solution. Teeth were de-coronated and their roots sectioned into three equal (cervical, middle and apical) parts. Cross sections were visualized under 40X magnification. RESULTS: Among all roots examined, 132 were straight both mesiodistally and buccolingually, 56 were mesiodistally curved, but buccolingually straight, 11 were mesiodistally straight, but buccolingually curved and 18 samples were curved in both aspects. Internal anatomical evaluation showed 198 samples (91.24%) with a single and 19 (8.75%) with more than one canal. CONCLUSION: Although straight roots are common in mandibular second premolars, curvatures in mesiodistal, buccolingual or both directions are not uncommon in the Iranian population. Single-canalled roots are also frequent in these teeth, but Vertucci's types II, III, IV, V, and C-shaped configurations are also encountered.