3D-printed inlays with different cavity depths impact intraoral-scanner’s accuracy in-vitro

Original Research


Introduction: CAD/CAM restorations of deep cavities are the challenges faced by intraoral-scanner (IOS) for accurate 3D data acquisition. This study aimed to evaluate the influence of cavity depth on the accuracy of intraoral digital impressions.

Methods: Three different mesio-occlusal class II inlay cavities on first maxillary molars were designed and 3D-printed with respective proximal box’s height of 1, 2 and 3mm (group 1, 2, 3 respectively), each of which was scanned 10 times using an IOS. The reference scans of inlay cavities were obtained by an industrial scanner. Data were 3D superimposed with reference impression for trueness (n=10) and intergroup superimposed (n=45) for precision. Outcome variables for value of trueness were mean average deviation (mm), minimum/maximum average deviation (mm) and unacceptable/total elements distribution ratio (%), and for value of precision was mean average deviation (mm).

Results: The 1mm-depth group resulted in the best trueness and precision significantly. For the trueness, there were significant differences between 3 groups with each other, the lowest deviation was for group 1 (21μm) statistically, followed by group 2 (24μm), group 3 (26μm). For the precision, group 1 showed the lowest scattered images statistically (mean deviation 4.7μm), then group 2, 3 (6μm and 13.8μm respectively). The deviated areas were located mostly at gingival walls of the cavity.

Conclusion: The deeper the cavity, the less accurate the digital impressions, which may raise clinical concerns. It suggests the cavity elevation with resin composite might optimize the 3D acquisition of IOS to ensure the fitness of CAD-CAM restorations.

Graphical abstract