Expression of receptor activator of NF-κB ligand and osteoprotegerin in peri-implant tissues during unloading period / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To observe the expression of receptor activator of NF-κB ligand (RANKL) and its decoy receptor osteoprotegerin (OPG) during unloading period of dental implants.</p><p><b>METHODS</b>An animal model of dental implants was established in Beagle dogs. Bone remodeling was tested at 3, 7, 15, 30, 60 and 90 days after the placement of implants. RANKL and OPG mRNA expression were quantified by real-time PCR. Then mandibular bones were resected and some sections were observed.</p><p><b>RESULTS</b>The most prominent period of bone remodeling occurred at 7 day after the placement of implants (OPG/RANKL mRNA, 2.15 ± 0.1). The expression of RANKL and OPG increased in a time-dependent manner in both soft and hard tissue. After 7 days they gradually decreased.</p><p><b>CONCLUSIONS</b>Both OPG and RANKL were expressed in peri-implant tissues, and the changing tendency of RANKL and OPGmRNA was consistent with the change of bone remodeling. The active stage for bone remodelling in peri-implant tissues during unloading period is about 7 days after implantation.</p>

Comparison of cytotoxicity between chemical retraction agents on human gingival fibroblasts in vitro / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To choose the best retraction agent for the clinic by evaluating cytotoxic effects of six chemical retraction agents on human gingival fibroblasts (HGF) in vitro.</p><p><b>METHODS</b>HGF were treated with six chemical retraction agents which included 20% Al2(SO4)3, 5% Al2(SO4)3, 15.5% Fe2(SO4)3, 13.3% Fe2(SO4)3, 0.1% HCl-epinephrine and 0.01% HCl-epinephrine. The damage of direct contact and proliferation inhibit were observed by methyl thiazolyl tetrazolium (MTT) colorimetric assay, the ultra structure was observed under transmission electron microscope (TEM).</p><p><b>RESULTS</b>All of chemical retraction agents caused cell damage and proliferation inhibit. The ability of cytotoxic effect increased in an order of 0.01% HCl-epinephrine<0.1% HCl-epinephrine<5% Al2(SO4)3<20% Al2(SO4)3<Fe2(SO4)3. There was no statistically significant difference between 13.3% Fe2(SO4)3 group and 15.5% Fe2(SO4)3 group. At HCl-epinephrine group and 5% Al2(SO4)3 group, the number of organelles were decreased, mitochondria and endoplasmic reticulum were swollen. At 20% Al2(SO4)3 group, organelles swelling and decreased number of organelles became more severe, the nuclear chromatin was unevenly distributed. Cell degeneration could be made by Fe2(SO4)3.</p><p><b>CONCLUSION</b>0.01% HCl-epinephrine was the least toxic gingival retraction agents, 13.3% Fe2(SO4)3 and 15.5% Fe2(SO4)3 are found to have the strongest cytotoxic effect on cell cultures.</p>