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Background: The purpose of the study was to investigate the accuracy of mini-implant placement with the use of a computer designed surgical guide derived by intraoral scanning alongside Cone-Beam Computed Tomography (CBCT) or the use of a 2D radiograph. Methods: Thirty-five mini-implants (Aarhus® System: n = 20, Ø: 1.5 mm and AbsoAnchor®: n = 15, Ø: 1.3–1.4 mm) were placed in the maxilla and mandible of 15 orthodontic patients for anchorage purposes in cases where a CBCT was needed due to impacted teeth or for safety reasons. All were placed with the help of a computer designed surgical guide. One implant became loose and was excluded from the study. For 18 mini-implants (study group), CBCT and intraoral scanning were used for guide design, while for 16 (control group) only intraoral scanning and panoramic imaging information were used. Mini-implant position was recorded by angular and linear measurements on digital models created by combining Digital Imaging and Communications in Medicine (DICOM) and stereolithography (.stl) files. Accuracy in positioning was determined by comparing corresponding measurements for virtual and real positioned mini-implants on digital models before and after operation. The results were statistically analyzed with t-tests and the Mann-Whitney test. Results: No significant statistical differences were found for pre- and post-operational angular measurements in the study group, while significant statistical differences occurred on the same measurements for the control group (coronal angle 13.6° pre-op and 22.7° post-op, p-value = 0.002, axial angle 13.4° pre-op and 15.9° post-op, p-value = 0.034). Linear measurements pre- and post-operational for either group presented no significant statistical differences. Conclusions: A 3D designed and manufactured surgical guide with information concerning CBCT and intraoral scanning ensures accuracy on mini-implant placement while design of the guide without the use of a CBCT is less accurate, especially on inclination of the implant.

This paper is part of a doctoral dissertation (PhD) research that investigates the development of a procedure for reliable 2D crowdsourced cadastral surveying introducing the use of new Information Technology IT tools and increased citizen participation, supported by m-services. For the development of this procedure, the formal cadastral procedure applied currently in two Europeans countries, Greece and Romania, for their modern nation-wide projects is firstly investigated. The first part of this paper briefly investigates the current stage of progress of those projects in both countries, as well as the specifications and procedures applied for the cadastral surveys, and assesses the level of participation of the right holders and the efficiency of the current procedures. Then, a proposal for a crowdsourced general procedure with increased participation of the right holders in the initial cadastral data collection phase is designed that it may be of value either for the planners of those two projects to improve their projects towards a more fit-for-purpose approach and successfully meet the deadlines timely, or for researchers and planners of other projects with similar nation-wide approaches which also require accurate, assured and authoritative end products. For the assessment of the applicability of the proposal, three case studies are held and tested in urban, rural and suburban areas in both countries, using both a commercial application and an open source one. These crowdsourced surveys are compared to the formal cadastral surveys that have been compiled by cadastral professionals in both countries and the achieved results are assessed and judged as satisfactory in terms of geometric accuracies and the avoidance of gross errors in the location of the parcels. A proposal for future research in order to further improve the proposed procedure is discussed.

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