Objective · To observe the effects of custom made fiber posts on the fracture resistance of young permanent teeth treated with calcium hydroxide for different time. Methods · Forty-five extracted human young permanent teeth (premolar) were selected and randomly assigned to 9 groups.One group was the control group and the rest 8 groups were treated with conventional root canal preparation. Of these 8 groups, 4 groups (F Ⅰ , F Ⅲ , F Ⅵ ,FⅨ ) were restored by custom made fiber posts after being treated with calcium hydroxide for 1, 3, 6, and 9 months respectively, and other 4 groups (C Ⅰ ,CⅢ , C Ⅵ , C Ⅸ ) were not restored by custom made fiber posts. All samples underwent fracture strength tests and their fracture modes were analyzed for the possibility of second repair. Results · The fracture load was decreased with the treatment time after being treated with calcium hydroxide for 1 month (P<0.01). The fracture loads in groups restored by custom made fiber posts were increased after being treated with calcium hydroxide for 6 and 9 months (P<0.05, P<0.01). After being treated with calcium hydroxide for 1 month, groups restored by custom made fiber posts were likely to have fracture modes that facilitate the second repair as compared with groups not restored by custom made fiber posts (P<0.05). Conclusion · The restoration by custom made fiber posts can increase the fracture resistance of young permanent teeth treated with calcium hydroxide for medium and long term ( ≥ 1 month).

Objective To analyze radiation induced alterations of vitronectin and collagen expressions in fibroblasts at different times post-irradiation,so as to evaluate the potential to apply vitronectin as a biomarker of radiation-induced lung fibrosis.Methods The human fibroblast cells WI-38 and IMR-90 were irradiated with 137Cs γ-rays at doses of 0 (control),4,6,8,10 and 12 Gy,respectively.The cells and its supernatant were collected at 6,12,24,36,48 and 60 h post-irradiation.The expressions of vitronectin and collagen Ⅰ and Ⅲ were analyzed by Western blot,PCR and ELISA.Results After irradiation,the expressions of vitronectin and collagen Ⅰ and Ⅲ were positively correlated (r=0.40-0.79,P＜0.05) and were all significantly higher than that in control group (t =3.04-25.45,P ＜0.05) and reached the highest expression levels at 48 h after 8-10 Gy of irradiation (t =2.92-18.86,P ＜ 0.05).Analyses of Real-time PCR and ELISA assay showed that expressions of vitronectin mRNA and its protein level in the cell lysis were significantly increased by radiation (F =27.09-42.62,P ＜ 0.05).Conclusions The expressions of vitronectin in cellular supernatant and its mRNA may be a potential biomarker of radiation-induced fibrosis,and 48 h after 8 Gy irradiation may be an optimum condition of measurement.