Temporospatial localization of dentine matrix protein 1 following direct pulp capping with calcium hydroxide in rat molars.

AIM: To examine the temporospatial expression of dentine matrix protein 1 (DMP1; a noncollagenous protein involved in mineralized tissue formation), osteopontin (another noncollagenous protein detected during reparative dentinogenesis) and nestin (a marker of differentiating/differentiated odontoblasts), following direct pulp capping with calcium hydroxide in rat molars. METHODOLOGY: The maxillary first molars of 8-week-old Wistar rats had their pulps exposed and capped with calcium hydroxide. The pulp-capped teeth were collected from 6 h to 14 days postoperatively and processed for immunohistochemistry for DMP1, osteopontin and nestin. Cell proliferation was monitored using 5-bromo-2'-deoxyuridine (BrdU) labelling. RESULTS: The capped pulps initially exhibited superficial necrotic changes followed by the formation of new matrix and its mineralization. DMP1 immunoreactivity was observed in the matrix beneath the necrotic layer from 6 h onwards and present in the outer portion of the newly formed mineralized matrix from 7 days onwards. Osteopontin displayed a similar expression pattern, although it occupied a narrower area than DMP1 at 6 and 12 h. Nestin-immunoreactive cells appeared beneath the DMP1-immunoreactive area at 1 day, were distributed beneath the newly formed matrix at 5 days and exhibited odontoblast-like morphology by 14 days. BrdU-positive cells significantly increased at 2 and 3 days (P < 0.05) and then decreased. CONCLUSIONS: The deposition of DMP1 at exposed pulp sites preceded the appearance of nestin-immunoreactive cells, active cell proliferation and new matrix formation after pulp capping with calcium hydroxide in rat molars, suggesting that DMP1 acts as a trigger of pulp repair. The colocalization of DMP1 and osteopontin suggests that these two proteins play complementary roles.

Bioactivity evaluation of three calcium silicate-based endodontic materials.

AIM: To compare white ProRoot MTA (WMTA), EndoSequence BC sealer (BC sealer) and Biodentine with regard to their ability to produce apatites and cause Ca and Si incorporation in adjacent human root canal dentine after immersion in phosphate-buffered saline (PBS). METHODOLOGY: Root sections of human single-rooted teeth were filled with one of the materials and immersed in PBS for 1, 7, 30 or 90 days (n = 5 each). Morphology and elemental composition of surface precipitates and interfacial dentine were analysed using a wavelength-dispersive X-ray spectroscopy electron probe microanalyser with image observation function. Ca- and Si-incorporation depths in the interfacial dentine were measured. In addition, the amount of Ca ions released from the test materials was measured by EDTA titration. RESULTS: All materials produced surface precipitates of acicular or lath-like morphology with Ca/P ratio of 1.6 : 2.0. Within dentinal tubules, the three materials formed tag-like structures that were frequently composed of Ca- and P-rich and Si-poor materials, suggesting intratubular precipitation. Ca- and Si-incorporation depths were in the order of Biodentine > WMTA > BC sealer, with a significant difference between BC sealer and the others at several time-points (P < 0.05, anova and Tukey's honestly significant difference test). The concentration of released Ca ions was in the order of Biodentine > WMTA > BC sealer with significant differences between the materials (P < 0.05). CONCLUSIONS: Compared with Biodentine and WMTA, BC sealer showed less Ca ion release and did not show Ca and Si incorporation as deeply in human root canal dentine when immersed in PBS for up to 90 days.

Uptake of calcium and silicon released from calcium silicate-based endodontic materials into root canal dentine.

AIM: To compare Biodentine and White ProRoot mineral trioxide aggregate (MTA) with regard to Ca and Si uptake by adjacent root canal dentine in the presence of phosphate-buffered saline (PBS). METHODOLOGY: Root canals of bovine incisor root segments were instrumented, filled with either Biodentine or MTA (n = 20 each) and then immersed in Ca-and Mg-free PBS for 1, 7, 30 or 90 days (n = 5 each). Unfilled, unimmersed dentine specimens (n = 5) served as controls. The specimens were sectioned longitudinally, and the ultrastructure of the dentine-material interface and the elemental composition/distribution in the material-adjacent dentine were analysed using a wavelength-dispersive X-ray spectroscopy electron probe microanalyser with image observation function. Data were statistically analyzed using one-way anova and Tukey's honestly significant difference test or the Mann-Whitney U-test. RESULTS: Along the material-dentine interface, both materials formed a tag-like structure that was composed of either Ca- and P-rich crystalline deposits or the material itself. The width of a Ca- and Si-rich layer detected along the dentine layer of the material-dentine interface showed increases over time. The Ca- and Si-rich layer width was significantly larger (P < 0.05) in Biodentine than MTA at 30 and 90 days. CONCLUSIONS: Both Biodentine and MTA caused the uptake of Ca and Si in the adjacent root canal dentine in the presence of PBS. The dentine element uptake was more prominent for Biodentine than MTA.

Neuron-immune interactions in the sensitized thalamus induced by mustard oil application to rat molar pulp.

We have reported that mustard oil application to the rat dental pulp induces neuronal activation in the thalamus. To address the mechanisms involved in the thalamic changes, we performed neuronal responsiveness recording, immunohistochemistry, and molecular biological analysis. After mustard oil application, neuronal responsiveness was increased in the mediodorsal nucleus. When MK801 (an N-methyl-D-aspartate receptor antagonist) was applied to the mediodorsal nucleus, the enhanced responsiveness was decreased. N-methyl-D-aspartate receptor 2D, glial fibrillary acidic protein, and antigen-presenting cell-related gene mRNAs in the contralateral thalamus were up-regulated at 10 minutes after mustard oil application, but were down-regulated within 10 minutes after the antagonist application. OX6-expressing microglia and glial fibrillary acidic protein-expressing astrocytes did not increase until 60 minutes after mustard oil application. These results suggested that the thalamic neurons play some roles in regulating the glial cell activation in the mediodorsal nucleus via N-methyl-D-aspartate receptor 2D during pulp inflammation-induced central sensitization.