Fit accuracy is one of the most important criteria for the success of ceramic restorations. Marginal discrepancies can increase the rate of microleakage, dissolution caused by oral fluids, and chemo-mechanical degradation. The internal gap dictates the cement space and affects strength and retention of the restoration.
Digital technologies were introduced with the aim of automating the production and standardizing the quality of dental restorations. Digital dentistry allows the production of dental restorations using advanced technologies such as subtractive or additive manufacturing through direct and indirect optical scanners. These systems were suggested to generate more accurately fitting restorations.
In the digitally-produced restorations, several factors have been documented to influence the fit accuracy including restoration-related, impression-related and manufacturing-related parameters.
However, additional factors related to the scanning device, design software and settings are significant in dictating the fit at the restoration-tooth interface. In substractive procedures, milling machine accuracy, milling-related conditions such as quality and size of the burs and material properties are important factors that can influence the adaptation. Laser speed and intensity, angle and building direction, number of layers, shrinkage between layers, amount of supportive material and post-processing procedures are related factors affecting the accuracy in additive technologies.