Objective To explore the effect of combined application of Pathfile in the VDW-Mtwo nickel titanium file in the elderly narrow canals.Methods 35 teeth with 101 root canals were divided into the two groups by drawing lots.In group A,root canals were prepared with VDW-Mtwo and Pathfile.In group B,root canals were prepared with VDW-Mtwo.All root canals were filled with continuous wave thermoplasticized gutta-percha technique.The operating time for each root canal,the number of broken instruments and postoperative pain were recorded.The efficacy of reparation was analyzed with radiography.Results The root canal preparation time of group A was (5.14 ± 1.25) min,which was significantly shorter than (6.82 ± 1.76) min of group B (t =5.539,P ＜ 0.05) ; The difference was not statistically significant in step formation and just fill rate between the two groups (P =1.00,1.74) ; The instrument intact of group A was 100.00％,which was significantly higher than 79.17％ of group B (x2 =4.279,P =0.039) ;The difference was not statistically significant in pain after operation between the two groups (P =0.20).Conclusion For narrow root canals preparation in the elderly treated with Mtwo and Pathfile would be shorten the preparation time and reduce broken instruments.

pFH23. These studies provide the possibility of further research on the expression of recombinant antigenic genes, the immunity of their expressed products and the protection of animals.

control relatives.A ratio of s/q approached1/q with Penrose' s method.Heritability of SLE was78.8%?4.45%in the first-degree relatives,58.8%?10.9%in the second-degree relatives,and39.2%?32.0%in the third-degree relatives.The weighted mean heritability was75.2%?4.12%.Conclusions SLE has characteristics of polygenic disease.Genetic factor might play an important role in the liability of SLE.

OBJECTIVE:To establish a method for the contents determination of triamcinolone acetonide acetate and tretinoin in Dimensional ointment. METHODS:HPLC was performed on the column of Diamonsil C18 with mobile phase of methanol-0.1%Phosphoric acid solution(87:13,V/V),detection wavelength was 254 nm(0-5 min)and 350 nm(5-20 min),at a flow rate of 1.0 ml/min,column temperature was 25℃,and volume injection was 10 μl. RESULTS:The linear range was 0.5-5 μg/ml for triamcin-olone acetonide acetate(r=0.999 9)and 4.96-49.6 μg/ml for tretinoin(r=0.999 8);RSDs of precision,stability and reproducibility tests were lower than 1%;recoveries were 98.37%-100.03%(RSD=0.58%,n=6)and 98.21%-100.38%(RSD=0.78%,n=6). CON-CLUSIONS:The method is simple,accurate and fast,and suitable for the contents determination of triamcinolone acetonide ace-tate and tretinoin in Dimensional ointment.