Accuracy of cast posts and cores using a new investigative method.

Generally, two techniques are used to fabricate a cast post and core (CPC): direct and indirect. To date, research has made no clear indication as to a comparative level of accuracy between the techniques. Therefore, the purpose of the current study was to compare the accuracy of two techniques to produce CPCs for posterior teeth using a new method. Nine endodontically treated human premolars were used for fabricating CPCs using the direct and indirect methods. A total of 18 CPCs were produced, two for each tooth, cast in high noble type IV gold. A silicone impression material was inserted into the root canals, followed by the CPCs. The remaining material in the space between the canal wall and the CPC was weighed using an electronic precision balance. By evaluating the weight of the silicon specimens, the accuracy and intimacy of fit were obtained. Since the number of samples was small, a Student t-test was used for statistical evaluation at a 90% confidence interval. The CPCs obtained by using each method were independently examined by two clinicians for proper fit. Power analysis indicated that for a 90% confidence interval and 0.8 power value, nine specimens would be necessary to achieve a statistically meaningful test. The mean value for the weight of the nine specimens obtained using the direct method was 10.3 ± 2.6 mg, while the mean value for the corresponding specimens obtained using the indirect method was significantly smaller, 7.4 ± 2.3 mg. The Student t-test value was P = 0.006. The indirect method provided CPCs with a better fit and higher accuracy. The Student t-test demonstrated a significant difference between the direct and indirect procedures. The indirect method is a valuable technique for the dental practitioner when multiple posterior cast posts and cores are necessary or interocclusal space is limited.