Variáveis envolvidas no processo de fabricação de coroas e endocrowns via CAD/CAM: efeito em adaptação e comportamento em fadiga

Abstract

The influence of instruments available for digital fabrication of indirect restorations, as well as different restorative materials, on the final aspect of the restoration is still little explored in the literature. Therefore, this thesis is composed of four articles. Study 1 aimed to compile existing scientific evidence on the effect of different intraoral scanners (IOS) and extraoral scanners (EOS) in terms of their accuracy for image acquisition and marginal/internal adaptation of indirect restorations through a scoping review. There is no conclusive evidence that differences between scanners (among the most commonly used systems) impact the marginal/internal adaptation of indirect restorations. However, due to high heterogeneity, the quality of the evaluated evidence is low, and well-designed studies are still encouraged, especially considering validated IOS/EOS as a control comparison condition. Study 2 aimed to compile scientific evidence regarding aspects involved in CAD/CAM milling processing of different types of indirect restorations. As a result, the planned cement space is hardly reproduced by milling machines. Additionally, variables such as the number of axes and characteristics of the diamond burs used impact the adaptation and precision of milling. Study 3 aimed to analyze the marginal/internal adaptation and fatigue behavior of crown restorations with two different materials (a lithium disilicate-based ceramic – LD; and a resin composite– RC), produced with two intraoral scanners (CEREC Primescan AC, Dentsply Sirona – PS; TRIOS 3, 3Shape – TR) and two milling machines (CEREC MC XL, Dentsply Sirona; PrograMill PM7, Ivoclar). IOS affected the axial-occlusal and occlusal adaptation, with no effect on fatigue behavior. RC crowns milled on a 5-axis machine provided superior adaptation and fatigue behavior, while the fatigue behavior of LD crowns was superior using a 5-axis machine compared to a 4-axis one. There is noticeable chipping at the margins of LD crowns due to milling. Study 4 aimed to evaluate the effect of the same two intraoral scanners, milling machines, and restorative materials used in the previous study on the marginal/internal adaptation and fatigue behavior of endocrown restorations. The adaptation of endocrowns is affected by the use of different IOS and milling machines. The restorative material plays an important role in the fatigue behavior of endocrowns, with RC restorations exhibiting superior behavior compared to LD. Angular regions and the pulpal wall appear to be areas with greater difficulty in being adequately milled. It is concluded that intraoral scanning devices, milling machines used in the fabrication of indirect restorations, and the selected restorative material influence the marginal and internal adaptation of crowns and endocrowns.