No abstract

Advances in treatment of tooth injury have shown that tooth regeneration from the pulp was a viable alternative of root canal therapy. In this study, we demonstrated that Gutta-percha, nanocomposites primarily used for obturation of the canal, are not cytotoxic and can induce differentiation of dental pulp stem cells (DPSC) in the absence of soluble mediators. Flat scaffolds were obtained by spin coating Si wafers with three Gutta-percha compounds: GuttaCore™, ProTaper™, and Lexicon™. The images of annealed surfaces showed that the nanoparticles were encapsulated, forming surfaces with root mean square (RMS) roughness of 136-211 nm. Then, by culturing DPSC on these substrates we found that after some initial difficulty in adhesion, confluent tissues were formed after 21 days. Imaging of the polyisoprene (PI) surfaces showed that biomineral deposition only occurred when dexamethasone was present in the media. Spectra obtained from the minerals was consistent with that of hydroxyapatite (HA). In contrast, HA deposition was observed on all Gutta-percha scaffolds regardless of the presence or absence of dexamethasone, implying that surface roughness may be an enabling factor in the differentiation process. These results indicate that Gutta-percha nanocomposites may be good candidates for pulp regeneration therapy.

No abstract

We have shown that Computed Microtomography (CMT) is able to map the internal distribution of the filler particles in ProTaper TM , Lexicon TM , and GuttaCore TM materials, and explain the differences in their tensile and ductility properties, prior to mechanical manipulation. Working of uncrosslinked ProTaper™ and Lexicon TM samples resulted in a five-fold increase in ductility and the tensile elongation at break. CMT mapping of the internal structure showed that large, periodic, striations formed across the interior of the sample corresponding to the formation of regions with low filler particle density. In contrast to metals which harden upon working, this migration of particles away from the high stress regions resulted in stress softening, as predicted by the Mullins effect.The results indicate that CMT is an effective method for 3-D visualization of the internal particle distribution which permits the determination of structure-property relationships and facilitates the design of new materials.