A CBCT (ICat, Image Sciences International, Hatfield, UK; 576 slices, voxel size 0.3 mm, FOV: 11 × 16 cm) was made of two oligodontia patients (for patient details, see Figs. 1 and 2) for implant planning. Detailed patient information was obtained with regard to the nerve position and bone quality and quantity. In addition, a digital intra-oral scan was made to get a detailed 3D image of the dentition (Chairside Oral Scanner: C.O.S., Lava™).

CBCT and intra-oral scanning data were combined using Simplant Pro (Dentsply, Hasselt, Belgium) in order to obtain a detailed 3D model of both patients (Fig. 3a, b) for virtual implant planning. The intra-oral scans, representing the dentition, were superimposed by a registration process, based on the contour of the corresponding dentition, onto the CBCTs. The intra-oral scan data was imported into the 3D virtual plan software as a stl-file. First, the objects representing the upper and lower dentition were globally positioned on the 3D data of the CBCT using manual translation functions. Next, exact positioning was determined using translation and rotation functions, starting in the mid-sagittal plane based on the contour of the model projected on the two-dimensional (2D) CT data. Refinements to the position were made while scrolling through the 2D CBCT data.

Virtual set-ups of the ultimate treatment goal were made for both patients with the virtual planning software Simplant Pro (Fig. 4a–c). Virtual teeth were aligned in the 3D virtual model. Based on the position of these teeth, the implants were planned in the optimal prosthodontic position; tooth size, optimal implant position, location of the mandibular nerve, bone quality and volume and antagonists were also accounted for. The planning was done by the technical physician (J.K.) for both cases, and the implant positions were checked and optimized by the prosthodontist (M.F. and A.V.), orthodontist (K.J.) and surgeon (G.R.).

Tooth-supported implant drilling templates were designed by the dental technician, based on the final virtual set-ups using the Geomagic Freeform software (3D Systems, Rock Hill, USA), and then fabricated out of polymethacrylate (Fig. 5a, b). The positioning of each implant was enabled with a 5-mm outer diameter metal drill sleeve (Nobel Guide, Nobel Biocare Holding AG, Zürich-Flughafen, Switzerland; Fig. 5a) as drill sleeves minimize deviation in drill position. The templates were checked for fit and stability in the intra-oral situation.