Investigations on the accuracy of 3D-printed drill guides for dental implantology

This article describes the computer-aided design/computer-aided manufacture (CAD/CAM) accuracy of dental drill guides for application in guided surgery. Today, the availability of three-dimensional (3D) desktop printers allows for the cost-effective production of drill guides by dental laboratories. Our investigations show the accuracy of produced guides by eliminating influencing factors that exist in the guided surgery workflow. To investigate this accuracy, a method was developed to evaluate the CAD/CAM production technology apart from sources of error from cone beam computed tomography (CBCT) scans, intraoral scans, software or human error. By using a CAD/CAM-milled idealized reference model, as well as CAD data from a scanned dental model with integrated reference spheres, drill guides with different offset values were designed using the coDiagnostiX^® implant-planning software. The Bone Level Roxolid^® SLActive^® implant system (length 8 mm, diameter 3.3 mm) was chosen. The virtual position in relation to both the drill guide and the reference model was determined based on the planning data and exported STL files, respectively. Virtual and physical measurements were performed through the center coordinates of the used drill sleeves (T-sleeve: 5 mm), by applying a defined reference coordinate system (RCS) of the dental model. Drill guide templates were printed using a FotoDent^® guide on a dental desktop printer (D30), based on a defined digital workflow. After insertion of the respective drill sleeves, surgical guides were secured on the reference models using quadrangular fixation, thus allowing a tactile measurement by applying a coordinate measurement device for determination of physical position relation. Through the central points of the drill sleeves, both the coronal and apical points of the planned implant drilling as well as angular deviation were calculated and reviewed against the CAD measurements. On average, a deviation of 0.25 degrees of the planned implant was detected. Keywords: stereolithography, digital light processing, 3D printing, CAD/CAM, guided surgery, drill guide