Studies On The Measuring Accuracy Of Root ZX And Propex

Objective: With the teeth in vitro as research objects, some factors which may have influence on the measurement accuracy of Propex and Root ZX would be studied, including completely dry root canal, irrigate liquids and the size of the apical foramen, besides, the comparative study on the measurement accuracy of the two devices would also be brought into the research scope.Methods: Experiment 1: Thirty teeth in vitro were implanted into the model in vitro and then measured orderly by Root ZX (A) and Propex (B), both of which were operated according to their own instructions. The working length of root canal (LR or LP) was obtained by EAL (Electronic apical locator) when the root canals were filled with different irrigate fluids, including completely dry, 3% H2O2, 0.9% NaCl and 2.5% NaClO. For the teeth which have been measured, the micro-observation of root apex was done and then the actual working length of root canal (LW=L-D) was obtained by means of software calculation. Finally, the difference value between LW and LR/LP was calculated, and the statistical analysis for the difference value was done. Experiment 2: The 40 teeth in vitro were randomly divided into four groups (A, B, C, D) with 10 in each group. To get the ones with different diameter (0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm), the root canal were pretreated orderly by different size K file ( type 15⁴0,type 15⁶0,type 15⁸0,type 15¹00). Under microscope, for the four groups (A, B, C, D), different type K files (type 40, type 60, type 80, type 100) were respectively used to measure the actual length of the root canal (L). And then the teeth in vitro were implanted into the model in vitro and then measured orderly by Root ZX (A) and Propex (B), both of which were operated according to their own instructions. And the length of root canal (L_R0 or L_P0) was obtained by EAL. Finally, the difference value between L and L_R0/L_P0 was calculated, and the statistical analysis for the difference value was done. Results: The results showed that the measuring deviations of Root ZXand Propex had no statistical significance (p>0.05) when the root canals were filled with different irrigate fluids, including completely dry, 3% H2O2, 0.9% NaCl and 2.5% NaClO. But the measuring deviation between Root ZX and Propex had statistical significance (p<0.05) when the same root canal was measured. Meanwhile, the measuring deviation of Root ZX and Propex had statistical significance (p<0.05) when the size of apical foramen was different. Regardless of using the small-sized files or using the large-sized files which corresponding to root canals, the measuring deviations of Root ZX and Propex had statistical significance (p<0.05). And the accuracy of Root ZX and Propex had no statistical difference (p>0.05).Conclusions: 1. When the root canals were completely dry or filled with the same irrigate fluid, the measuring deviation of Propex was smaller than that of Root ZX, but the differences between them had no statistical significance. 2. The size of apical foramen and the size of file could affect the accuracy of Root ZX and Propex, respectively. The bigger the size of apical foramen and the smaller the size of file, the greater the deviation. So files which corresponding to root canals should be recommended to the clinical application, when measuring the working length of root canals.