Growth and differentiation of osteoblastic cells on 13-93 bioactive glass fibers and scaffolds.

This in vitro study was conducted to evaluate the ability of two types of constructs of bioactive, silica-based 13-93 glass fibers to support the growth and differentiation of MC3T3-E1 osteoblastic cells. The two types of constructs tested included single-layer 13-93 glass fiber rafts and three-dimensional porous scaffolds formed from sintered 13-93 fibers. Scanning electron micrographs showed a closely adhering, well-spread morphology of MC3T3-E1 cells seeded on both types of constructs. The scanning electron microscopy images also showed a continuous increase in cell densities during a 6 day incubation on 13-93 glass fiber rafts and scaffolds. Quantitative fluorescence measurements of DNA also revealed a linear increase in cell density during a 6 day incubation on both types of 13-93 constructs. Examination of scaffolds incubated in MTT containing medium showed the presence of metabolically active viable cells within the interior of the scaffold. The addition of ascorbic acid to MC3T3-E1 cells cultured on the 13-93 glass fibers triggered a threefold increase in alkaline phosphatase, a key indicator of osteoblast differentiation. The sintered scaffolds were found to have open, interconnected pores favorable for tissue ingrowth with a compressive strength similar to cancellous bone. Collectively, the results indicate that 13-93 glass fiber scaffolds are a favorable substrate for the growth and differentiation of osteoblasts and a promising material for bone tissue engineering and repair of bone defects.

Potential iatrogenic tetracycline staining of endodontically treated teeth via NaOCl/MTAD irrigation: a preliminary report.

This study reported red-purple staining of light-exposed, root-treated dentin when root canals were rinsed with 1.3% NaOCl as initial rinse followed by the use of BioPure MTAD as final rinse. This intrinsic dentin staining occurred irrespective of whether the root canals were filled, and could be observed even in crown dentin when the latter was sequentially immersed in NaOCl and MTAD. Bench-top reproductions of the phenomenon revealed that the exothermic reaction is not an acid-base reaction. Conversely, the reaction is of a redox nature that highly resembled the previously reported mechanism of tetracycline staining, in which photo-oxidation of tetracycline resulted in a red-purple tetracycline degradation product that has a high affinity for hydroxyapatite. This photo-oxidative degradation process is probably triggered by the use of NaOCl as an oxidizing agent, and may be prevented by rinsing the NaOCl-treated dentin with ascorbic acid, a reducing agent, before the application of MTAD.