Effect of preparation type on the accuracy of different intraoral scanners: An in vitro study at different levels of accuracy evaluation

Abstract

Objective Evaluation of the effect of preparation type (inlay, onlay, and crown) on the accuracy of different intraoral scanning (IOS) systems at the preparation and arch segment levels. Materials and Methods Three molars were prepared for inlay, onlay, and crown. Each preparation was scanned 10 times by CEREC Omnicam, Trios 3 (TS), and Medit i500 scanners. Each image was trimmed twice. The first trimming produced a preparation image (PI), and the second trimming extracted a segment image (SI) that involved the preparation with the adjacent teeth. Trueness and precision were calculated at the PI and SI levels. Results At the PI level, all IOS systems had similar trueness pattern for all preparations, where the inlay had the best trueness followed by the crown and onlay. At the SI level, the different preparations showed similar trueness. The precision did not show a clear pattern of superiority for any preparation. The TS was significantly more precise than other IOS systems at the PI and SI levels, for every preparation. The proximal areas suffered from the greatest errors, regardless of preparation type. Conclusions The preparation type influenced PI trueness, and the IOS system affected PI and SI precisions. Clinical Significance The smaller and less complex preparations have greater IOS accuracy than larger and more complex preparations. As the proximal areas are more affected regardless of the preparation, a more accessible proximal area for scanning is desirable.

Digital workflow in implant prosthodontics: The critical aspects for reliable accuracy

“…In the absence of a scientifically validated scan strategy, we have relied on our experience that suggests to apply the following precautions which should be matter for future research projects: The IOS tip should be held close and parallel to the occlusal surface of the teeth or the gingiva in the edentulous spaces; although most of the IOS allow a contact scan, there are some devices that have a certain depth of field to respect. In this case, the advice is to try not to have oscillations outside the optimal working area 20,33 It should not advance too quickly in order to facilitate stitching; a movement that is too rapid may create a poor and approximate acquisition of points 20,24,33 .…”

“…A random movement may not have these sure foundations to progress with the stitching of new surfaces. 20,24,33 Consequently, the acquired objects could incorporate distortions that are difficult to be appreciated once the mesh is created.…”

“…In this case, the advice is to try not to have oscillations outside the optimal working area. 20,33 • It should not advance too quickly in order to facilitate stitching; a movement that is too rapid may create a poor and approximate acquisition of points. 20,24,33 On the other hand, dwelling too much on areas already correctly acquired can worsen the quality of the final mesh.…”

“…So, the advice is to scan the surfaces at their best, then move forward, avoiding to return several times in areas already fully scanned. The movements should be linear and not chaotic or random; a linear movement creates portions of surfaces on which new points are based for the progression. A random movement may not have these sure foundations to progress with the stitching of new surfaces 20,24,33 . Consequently, the acquired objects could incorporate distortions that are difficult to be appreciated once the mesh is created. The cheeks, lips and tongue should be kept away from the teeth through the use of appropriate devices and the field should be as dry as possible 34 ; the visibility and accessibility of the operating field is a crucial factor.…”

Evaluating the accuracy of CAD/CAM optimized stones compared to conventional type IV stones

“…Extraoral scanners capture the whole surface to acquire more data simultaneously The blue light-emitting diode (LED) extraoral scanner was used in the present study. The scanner uses stripe light triangulation, and the accuracy was 6 μm [ 14 , 30 – 32 ].…”