Implant prosthodontics refers to rehabilitating partially or edentulous patients with removable or fixed prostheses anchored to one (or more) dental implant(s). The workflow, intended through data collection to transfer the implants’ intraoral position to the dental lab in order to create a prosthesis, was once completely analog. To this day, various digital technologies have been applied to the reconstructive process, both in the clinic and the lab. However, many aspects still require investigation. To date, to install a single implant in the posterior area, full-arch CBCT scans are used and display anatomical structures outside of the region of interest. According to the results of Manuscript 1, the radiographic FOV reduction does not affect the accuracy of registration for single tooth gaps in the posterior area and in the absence of sources of artifacts. Improvements are needed to further decrease patients´ radiation dose for virtual implant planning purposes. After registration of the radiographic and surface scans, the ideal implant must be selected. Prefabricated titanium thread–shaped implants are founded on long-term data from the literature. An alternative option for immediate implant installation is offered by RAIs. CAD/CAM custom-made RAIs reproduce the shape of the dental root(s) based on the digitally segmented 3D radiographic dataset and are fabricated before surgery. In the included retrospective investigation (Manuscript 2), clinical outcomes and PROMs from a patient cohort rehabilitated with FDPs supported by custom-made RAIs were collected and analyzed. An optimal esthetic outcome and favorable results in terms of peri-implant soft tissues were reported after a mean follow-up of 19 months. Data regarding marginal bone loss (1.20 ± 0.73 mm after 12.1 ± 6.9 months) and survival rate (94.4% after 18.9 ± 2.4 months), however, were 123 comparable or inferior to data on threaded stock implants. It also appears that the implementation of RAIs bears, at this moment, no relation to the necessary expenses and production efforts. In addition, Natural Dental Implants (NDI Berlin), the company marketing the evaluated implant system, ceased operations at the end of January 2020. For accurate implant installation, a surgical guide can be used. In Manuscripts 3 and 4, a protocol to create economic and sterilizable surgical guides by ME was described. Comparable results in terms of the trueness of the final implant position to market-available surgical guides created by SLA were assessed (Manuscript 3). In the second manuscript, the impact of variables (e.g., implant planning software and surgical guide designs) on the accuracy, intended as trueness and precision, of implant positioning was evaluated (Manuscript 4). Both evaluated variables revealed a significant influence on the outcome, but low mean deviations of ≤ 0.32 mm and ≤ 2.63° were assessed. Moreover, the cytotoxicity of the biopolymer used to create the surgical guides was tested in vitro in Manuscript 5 and confirmed the biocompatibility for short-term intraoral use. The last study in the present thesis (Manuscript 6) investigated the feasibility of scanning a one-piece ZrO2 implant without a scan body, revealing comparable accuracy to a two-piece titanium implant with a scan body. Furthermore, a digital reconstruction tool was applied to complete incomplete scans. The use of one-piece implants is limited due to surgical and prosthetic limitations. Nevertheless, scan body–free digitization might also be applicable to two-piece implants at some point. For reconstructive purposes, CAD systems might rely on the implant shoulder and internal conformation rather than the scan body geometry in the future.
