Accuracy evaluation of fixed prosthetic constructions made by milling and printing technologies and the influence of temperature changes

The aim of this study is to evaluate the internal and external fit accuracy of fixed metal-ceramic prosthetic constructions made by milling and printing technologies and the influence of temperature changes on this accuracy. An acrylic resin tooth was prepared according to the standard guidelines for a metal-ceramic crown. A standard intraoral silicone impression was taken and a stone model was prepared. The stone model was scanned by an extraoral digital scanner and a digital copy of the prosthetic field was created. The digital copy was used to create a digital prototype of the future metal substructure for the metal-ceramic crown. Using the same data, the metal substructure was formed once by milling technology, and once by 3D-printing technology. The internal surface of both samples was measured. The stone model preparation surface was also measured. All data were compared to the digital prototype. According to the standard technology, a dental technician applied ceramic material, by hand as usual, in layers and the constructions were sintered. After the thermal procedure, once again the substructure’s internal surface was measured and compared with the previous data. The constructions were finished by glazing by the dental technician applying the last layer ceramic and sintering it. The construction’s internal surface was again measured and the data obtained were compared with the previous data. Conclusion about the influence of the temperature changes caused by the sintering process on the metal substructures was made using the data acquired by all the measurements made between the different stages. The difference in the internal fit of the constructions made by the milling and the 3D-printing technology will not affect to crown’s ergonomics. The quality of the internal fit for the construction made by milling technology is better than this made by 3D-printing technology. Unnoticeable changes in the internal surface were found after the temperature changes caused by the process of sintering for both types of constructions. Both types of technologies could be used to produce high quality accurate metal substructures for the needs of the fixed prosthetic dental medicine. The temperature changes caused by the sintering process during the standard metal-ceramic technology have a small influence to the construction’s internal fit.