Porphyromonas gingivalis lipids inhibit osteoblastic differentiation and function.

Porphyromonas gingivalis produces unusual sphingolipids that are known to promote inflammatory reactions in gingival fibroblasts and Toll-like receptor 2 (TLR2)-dependent secretion of interleukin-6 from dendritic cells. The aim of the present study was to examine whether P. gingivalis lipids inhibit osteoblastic function. Total lipids from P. gingivalis and two fractions, phosphoglycerol dihydroceramides and phosphoethanolamine dihydroceramides, were prepared free of lipid A. Primary calvarial osteoblast cultures derived from 5- to 7-day-old CD-1 mice were used to examine the effects of P. gingivalis lipids on mineralized nodule formation, cell viability, apoptosis, cell proliferation, and gene expression. P. gingivalis lipids inhibited osteoblast differentiation and fluorescence expression of pOBCol2.3GFP in a concentration-dependent manner. However, P. gingivalis lipids did not significantly alter osteoblast proliferation, viability, or apoptosis. When administered during specific intervals of osteoblast growth, P. gingivalis total lipids demonstrated inhibitory effects on osteoblast differentiation only after the proliferation stage of culture. Reverse transcription-PCR confirmed the downregulation of osteoblast marker genes, including Runx2, ALP, OC, BSP, OPG, and DMP-1, with concurrent upregulation of RANKL, tumor necrosis factor alpha, and MMP-3 genes. P. gingivalis total lipids and lipid fractions inhibited calvarial osteoblast gene expression and function in vivo, as determined by the loss of expression of another osteoblast differentiation reporter, pOBCol3.6GFPcyan, and reduced uptake of Alizarin complexone stain. Finally, lipid inhibition of mineral nodule formation in vitro was dependent on TLR2 expression. Our results indicate that inhibition of osteoblast function and gene expression by P. gingivalis lipids represents a novel mechanism for altering alveolar bone homeostasis at periodontal disease sites.

Effect of selected accelerants on setting time and biocompatibility of mineral trioxide aggregate (MTA).

OBJECTIVE: Various additives have been suggested to be used with mineral trioxide aggregate (MTA) to improve its handling characteristics. The purpose of this study was to evaluate the effects of various additives on setting time and cell attachment on gray MTA (GMTA). STUDY DESIGN: Single-rooted caries-free teeth were split, and dentin disks with class I cavity were made and filled with test and control materials. Setting time was measured using Gilmore apparatus. Mouse MC3T3-E1 osteoblasts and L929 mouse fibroblasts were grown on dentin and GMTA disks. Cell attachment was examined under fluorescent microscope. RESULTS: Adding KY liquid, CaCl(2), and NaOCl to GMTA improved the handling properties and decreased setting time. Osteoblasts and fibroblasts attached and spread on GMTA mixed with additives in a manner similar to GMTA mixed with water. CONCLUSIONS: The various additives could be possible substitutes to water to decrease MTA setting time. MTA is biocompatible when mixed with the various additives.

Cytotoxicity evaluation of endosequence root repair material.

OBJECTIVE: The purpose of this study was to evaluate the cytotoxicity of EndoSequence Root Repair Material (Brasseler USA, Savannah, GA) and compare it with gray and white MTA. STUDY DESIGN: Samples of 2 mg freshly mixed or set gray MTA (GMTA), white MTA (WMTA), EndoSequence Root Repair Material (ERRM), and AH26 were eluted with 300, 600, and 1,000 microL cell culture medium for 24 and 72 hours. L929 cells were seeded into 96-well plates at 3 x 10(4) cells/well and incubated with 100 microL elute from each elute group. Cells cultured only with culture medium served as negative control. AH26 was used as positive control. After 24 hours' incubation, cell cytotoxicity was evaluated by MTT assay. Cell viability was calculated as percentage of the control group. The results were analyzed with 1-way analysis of variance. RESULTS: For both set and fresh samples, there were no significant cell viability differences among GMTA, WMTA, and ERRM. Cell viability in the AH26 group was less than in all of the other 3 materials. CONCLUSION: This study suggests that ERRM may have cell viability similar to GMTA and WMTA in both set and fresh conditions.