Evaluation of custom posts and cores fabricated by two digital technologies in core and post space dimensions.

PURPOSE: To evaluate the adaptability between posts and post spaces and the rationality of cores fabricated by two digital custom post-and-core processes. MATERIALS AND METHODS: Titanium post-and-cores were fabricated by digital scanning impression technology or digital scanning wax-pattern technology on tooth defect molds of incisors, premolars, and molars, with traditional lost-wax casts of these teeth as the controls. Micro-CT and a laboratory scanner were used to determine intervals between post wall and root canal wall of the root apex, middle, and cervix of each sample in cross-, sagittal, and coronal sections; intervals between the end of post and tooth; diameters of cervical, middle, and incisal part at cross-, sagittal, and coronal sections of each sample, as well as shoulder widths. RESULTS: The three fabrication processes showed significant differences in intervals between post-and-core prostheses and root canal walls, diameters of all parts of cores, and shoulder widths. Scanning impressions showed significant advantages in the main part of post-and-cores in incisors and premolars, while the scanning wax-pattern process showed obvious inferiorities in premolars and molars. As to core spatial size, values of measured sites in the scanning impression process were closer to the standard than those of the traditional process, while differences between the measured value of the scanning wax-pattern process were much more obvious than in the traditional process. CONCLUSIONS: The use of digital custom post-and-core scanning impressions improved the rationality and precision of post-and-core dimensions compared with two other processes.

'Gold' lost in restoration: Evaluation of core morphology of custom metal posts and cores, and analysis of precious metal debris.

1 Objectives: To investigate the deviations between the morphological dimensions of finished cores and desired dimensions made by three available fabricating techniques. To assess the precious metal loss in custom precious metal post and core restorative treatment in the dental clinic. 2 Methods: Titanium posts and cores were fabricated using three different techniques: digital scanning impression technology, digital scanning wax-pattern technology, and the traditional lost-wax casting method. Geomagic Studio was used to fit the scanned model data to the digital design data of the expected preparation and to analyze the 3D deviations between the two. Precious metal debris from the precious metal post and core was collected, processed, weighed and analyzed for precious metal elements by energy-dispersive X-ray spectroscopy layered images. 3 Results: In all 48 pairs of models, there were positive and negative deviations, with the largest mean positive deviation of (0.752 ± 0.037 mm) for models made by the semi-digital scanning wax-pattern technique. A total of 7001.3 mg of metals was recovered from the waste streams collected, which contained precious metals-mainly gold, silver, and platinum. 4 Conclusions: There were discrepancies between the custom core and the expected preparation regardless of the fabrication process used. The digital scanning impression technology showed better dimensional rationality of crown cores. Custom precious metal posts and cores can have an average precious metal loss of 129.7 mg per case in the dental clinic.