Abstract: PURPOSE: To evaluate the effect of impressions made by agar/alginate compared with silicon rubber material. METHODS: Five moulds of bi-root canal molar, with different root canal angles of 0°, 10°, 20°, 30° and 40° were made. Twenty impressions were made for each mould with either silicon rubber or agar/alginate. The effects of two methods were evaluated and the influence of angles between root canals on the impression methods was analyzed. The data was analyzed with SPSS16.0 software package. RESULTS: Significant difference of integrality rate (IR) of impression was not found in silicon rubber group among different angle groups (P>0.05). IR of 40° group(60%) was significantly lower than that of 0°(95%) and general IR(83%) when using agar(P<0.05). IR of agar(60%) was statistically lower than silicon rubber(90%) in 40° group (P<0.05).The success rate of agar method was significantly lower than silicon rubber method in 40° group. The general IR of agar (83%) was significantly lower than that of silicon rubber (95%)(P<0.05). A significant negative correlation was observed between root canal angles and IR(r=-0.901,P=0.037). CONCLUSIONS: Silicon rubber impression materials are suggested for impression taking when root canal angles are over 30° in molars, while agar/alginate impression method is qualified for smaller angles. The general IR of silicon rubber material is better than that of agar when taking the impression of post and core in molar.

Key words: Agar, Impression, Root canal, Post and core, Integrity rate