Comparative evaluation of the effect of ditching by laboratory technicians and standard approach on marginal adaptation of cast restorations

Marginal adaptation of cast restorations is essential for their long-term success. As dentists usually assign ditching of dies to laboratory technicians, and ditching has a significant effect on marginal adaptation, the aim of this study was to compare ditching by laboratory technicians and standard approach on marginal adaptation of cast restoration. In this laboratory experimental study a metal-ceramic preparation was carried out on an acrylic left mandibular first molar with a heavy chamfer finish line. Thirty working casts were obtained, 25 of which were ditched by laboratory technicians working in Isfahan and 5 others were ditched by a prosthodontist according to a standard approach. Then, castings were made on the ditched dies and vertical marginal discrepancies were measured in both groups under a stereomicroscope and with the use of a digital camera on four tooth surfaces. Data was analyzed using t-test and ANOVA. Statistical significance was defined at p value < 0.05. Mean vertical marginal discrepancies of all the tooth surfaces were 436.03 ± 318.04 and 117.17 ± 83.49 microns in the laboratory technician and standard groups, respectively, with statistically significant differences between the two groups (p value < 0.0001). However, there were no significant differences between the means of vertical marginal discrepancies in the standard (p value = 0.95) and laboratory technician (p value = 0.58) groups. Based on the results, ditching by dental practitioners is more accurate. It appears provision of educational program for laboratory technicians on ditching dies and referring the questionable cases to dental practitioners are essential.