Background: This systematic review summarizes the current knowledge on the
superimposition of three-dimensional (3D) diagnostic records to realize an orthodontic virtual
patient. The aim of this study is to analyze the accuracy of the state-of-the-art digital workflow.
Methods: The research was carried out by an electronic and manual query eectuated from ISS (Istituto
Superiore di Sanit\ue0 in Rome) on three dierent databases (MEDLINE, Cochrane Library and ISI WEB
OF SCIENCE) up to 31st January 2020. The search focused on studies that superimposed at least two
dierent 3D records to build up a 3D virtual patient\u2014information about the devices used to acquire 3D
data, the software used to match data and the superimposition method applied have been summarized.
Results: 1374 titles were retrieved from the electronic search. After title-abstract screening, 65 studies
were selected. After full-text analysis, 21 studies were included in the review. Dierent 3D datasets
were used: facial skeleton (FS), extraoral soft tissues (ST) and dentition (DENT). The information
provided by the 3D data was superimposed in four dierent combinations: FS + DENT (13 papers),
FS + ST (5 papers), ST + DENT (2 papers) and all the types (FS + ST + DENT) (1 paper). Conclusions:
The surface-based method was most frequently used for 3D objects superimposition (11 papers),
followed by the point-based method (6 papers), with or without fiducial markers, and the voxel-based
method (1 paper). Most of the papers analyzed the accuracy of the superimposition procedure
(15 papers), while the remaining were proof-of-principles (10 papers) or compared dierent methods
(3 papers). Further studies should focus on the definition of a gold standard. The patient is
going to have a huge advantage from complete digital planning when more information about
the spatial relationship of anatomical structures are needed: ectopic, impacted and supernumerary
teeth, root resorption and angulations, cleft lip and palate (CL/P), alveolar boundary conditions,
periodontally compromised patients, temporary anchorage devices (TADs), maxillary transverse
deficiency, airway analyses, obstructive sleep apnea (OSAS), TMJ disorders and orthognathic and
cranio-facial surgery
