Impact of remnant healthy pulp and apical tissue on outcomes after simulated regenerative endodontic procedure in rat molars

When regenerative endodontic procedures (REPs) are performed on immature teeth diagnosed with pulp necrosis and apical periodontitis, various healing patterns occur. Furthermore, infected immature teeth with endodontic disorders often exhibit some remnant pulp and apical tissue. Therefore, this study investigated the impact of remnant healthy or fully functional pulp and apical tissue on healing patterns after REPs. Simulated REPs were performed on non-infected immature rat molars with different amounts of remnant pulp and apical tissue. Healing patterns in these teeth were assessed after 28 days. Teeth with 0.81–0.91 mm of remnant pulp healed with pulp-like tissue, dentin, and osteodentin-like dentin-associated mineralized tissue (OSD-DAMT); teeth with 0.60–0.63 mm of remnant pulp healed with pulp-like tissue and OSD-DAMT; teeth with 0.13–0.43 mm of remnant pulp healed with periodontal ligament (PDL)-like tissue, OSD-DAMT, and cementum-like dentin-associated mineralized tissue (CEM-DAMT); and teeth with disorganization of pulp and apical tissues at 0.15–0.38 mm beyond the root apex healed with PDL-like tissue, CEM-DAMT, and intracanal bone (IB). Loss of Hertwig’s epithelial root sheath was observed with IB formation. These results showed that four distinct healing patterns occurred after REPs, depending on the preoperative amount of remnant healthy pulp and apical tissue.

The effect of steroid hormone on the expression of the calcium-processing proteins in the immature rat brain

Background The cytosolic calcium concentration is regulated by calcium-processing proteins such as transient receptor potential cation channel subfamily V member 5 (TRPV5), TRPV6, sodium-calcium exchanger 1 (NCX1), and plasma membrane Ca 2+ ATPase 1 (PMCA1). Those calcium-processing proteins are important for physiological functions in the brain. The effects of steroid hormones on calcium-processing protein expressions in the brains are unknown. Thus, the effects of steroid hormones on the distribution, localization, and expressions of calcium-processing proteins in the brain were analyzed. Immature female rats were injected with estrogen (E2), progesterone (P4), dexamethasone (DEX), and their antagonists (ICI 182,780 and RU486).Results We found that TRPV5 and TRPV6 proteins were highly expressed in the cerebral cortex (CT), hypothalamus (HY), and brain stem (BS) compared to that in the olfactory bulb (OB) and cerebellum (CB). Also, the NCX1 protein was highly expressed in CT and BS compared to that in OB, HY, and CB, and PMCA1 protein was highly expressed in CT compared to that in other brain regions. Furthermore, expression levels of TRPV5, TRPV6, NCX1, and PMCA1 proteins were regulated by E2, P4, and/or DEX in the CT and HY. In summary, calcium-processing proteins are widely expressed in the immature rat brain, and expressions of calcium-processing proteins in CT and HY are regulated by E2, P4, and/or DEX and can be recovered by antagonist treatment.Conclusion These results indicate that steroid hormone regulation of TRPV5, TRPV6, NCX1, and PMCA1 proteins may serve as a critical regulator of cytosolic calcium absorption and release in the brain.