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The invention of computerized axial tomography (now known as computerized tomography) and developments of interactive software to allow virtual planning, with the aim to guide the surgery precisely toward a specific target, has dramatically improved general, as well as oral, surgery. Virtual dental implant planning allows for a prosthetically driven approach, resulting in the best possible design of the prosthesis, better esthetics, optimized occlusion and loading. This approach has also changed the surgical paradigm of using extensive flaps to obtain a proper view of the surgical area because flapless implant surgery, with or without immediate loading, has become more predictable. Two types of guided implant surgery protocols - static and dynamic - are described in the literature. The static approach, better known as computer-guided surgery, refers to the use of a tissue-supported surgical template. This reproduces the virtual implant position directly from computerized tomographic data and this information can be converted to guide templates to be used during surgery, with or without raising a mucoperiosteal flap. Dynamic guided surgery, also called navigation, reproduces the virtual implant position directly from computerized tomographic data and uses motion-tracking technology to guide the implant osteotomy preparation. As the technology developed further, different levels of evidence were presented that showed various degrees of accuracy. Several protocols for guided surgery are available in the literature and are distinguished by different guide production techniques, methods of support and drilling/placement protocols. Currently, implant planning software using cone-beam computerized tomography data has made it possible to plan the optical implant position virtually the optimal implant position, taking the surrounding vital anatomic structures and future prosthetic requirements into consideration. This paper summarizes the evolution and ongoing trends in digital and virtual planning and in implant surgery. The purpose of this overview was to clarify the different concepts in guided surgery and their respective advantages, disadvantages and limitations. The outcome of guided surgery is assessed in terms of implant survival, precision and complications. Clinical cases are given to demonstrate briefly the workflow and clinical guidelines for safe use of these approaches.

Intra-oral scanners will play a central role in digital dentistry in the near future. In this study the accuracy of three intra-oral scanners was compared. Materials and methods: A master model made of stone was fitted with three high precision manufactured PEEK cylinders and scanned with three intra-oral scanners: the CEREC (Sirona), the iTero (Cadent) and the Lava COS (3M). In software the digital files were imported and the distance between the centres of the cylinders and the angulation between the cylinders was assessed. These values were compared to the measurements made on a high accuracy 3D scan of the master model. Results: The distance errors were the smallest and most consistent for the Lava COS. The distance errors for the Cerec were the largest and least consistent. All the angulation errors were small. Conclusions: The Lava COS in combination with a high accuracy scanning protocol resulted in the smallest and most consistent errors of all three scanners tested when considering mean distance errors in full arch impressions both in absolute values and in consistency for both measured distances. For the mean angulation errors, the Lava COS had the smallest errors between cylinders 1–2 and the largest errors between cylinders 1–3, although the absolute difference with the smallest mean value (iTero) was very small (0,0529°). An expected increase in distance and/or angular errors over the length of the arch due to an accumulation of registration errors of the patched 3D surfaces could be observed in this study design, but the effects were statistically not significant.Clinical relevanceFor making impressions of implant cases for digital workflows, the most accurate scanner with the scanning protocol that will ensure the most accurate digital impression should be used. In our study model that was the Lava COS with the high accuracy scanning protocol.

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The aim of the present study was to evaluate the effect of the build angle and the support configuration (thick versus thin support) on the dimensional accuracy of 3D-printed full-coverage dental restorations. Materials and Methods: A full-coverage dental crown was digitally designed and 3D-printed using stereolithography-additive manufacturing (SLA-AM) technology. Nine different angles were used during the build process: 90, 120, 135, 150, 180, 210, 225, 240, and 270 degrees. In each angle, the crown was printed using a thin and a thick support type, resulting in 18 specimens. The specimens were digitally scanned using a highresolution optical surface scanner (IScan D104i; Imetric 3D). The dimensional accuracy was evaluated by digital subtraction technique. The 3D digital files of the scanned printed crowns (test model), exported in standard tessellation language (STL) format, were superimposed with the STL file of the designed crown (reference model) using Geomagic Studio 2014 (3D Systems). Results: The root mean square estimate value and color map results suggest that the build angle and support structure configuration have an influence on the dimensional accuracy of 3D-printed crown restorations. Among the tested angles, the 120-degree build angle showed a minimal deviation of 0.029 mm for thin support and 0.031 mm for thick support, indicating an accurate fit between the test and reference models. Furthermore, the deviation pattern observed in the color map was homogenously distributed and located further away from the critical marginal area. Conclusions: Within the limitations of this study, the selection of build angle should offer the crown the highest dimensional accuracy and self-supported geometry. This allows for the smallest necessary support surface area and decreases the time needed for finishing and polishing. These properties were mostly observed with a build angle of 120 degrees combined with a thin support type.