Assessment of methods used for 3-dimensional superimposition of craniofacial skeletal structures: a systematic review

Abstract

Background So far, several techniques have been recommended for the assessment of craniofacial changes through skeletal tissue superimposition, but the evidence that supports them remains unexplored. The purpose of the present study is to assess the available literature on skeletal-tissue superimpositions of serial craniofacial CT or CBCT images used to detect morphological changes. Materials and Methods Medline (via Pubmed), EMBASE, Google Scholar, Cochrane Library, Open Grey and Grey Literature Report were searched (last search: 17.11.2019) using specific terms that fulfilled the requirements of each database in the context of the study aim. Hand searches were also performed. The outcomes of interest were the accuracy, precision, or agreement between skeletal-tissue superimposition techniques to assess changes in the morphology of craniofacial structures. Studies of any design with sample size ≥3 were assessed by two authors independently. The study protocol was registered in PROSPERO (ID: CRD42019143356). Results Out of 832 studies, fifteen met the eligibility criteria. From the 15 included studies, 12 have shown high total risk of bias, one low risk of bias, and two studies have shown unclear risk of bias. Thirteen out of the 15 studies showed high applicability concerns, two unclear and no study had low applicability concerns. There was high heterogeneity among studies regarding the type of participants, sample size, growth status, machines, acquisition parameters, superimposition techniques, assessment techniques and outcomes measured. Fourteen of them were performed on Cone Beam Computed Tomography (CBCT) and one on Computed Tomography (CT) derived 3D models. Most of the studies (eleven) used voxel-based registration, one landmark-based registration and three studies compared different registration techniques, which include the surface-based registration. Concerning the area of interest, nine studies focused on the anterior cranial base and certain facial structures, four on maxillary structures and four on mandibular structures. Non-growing participants were included in six studies, growing in eight, whereas one study had both. Conclusion Most of the available studies had methodological shortcomings and high applicability concerns. At the moment, certain voxel-based and surface-based superimpositions seem to work properly and to be superior to landmark-based superimposition. However, further research in the field is required to develop and properly validate these techniques on different samples, through high quality studies with low applicability concerns.

Valid 3D Surface Superimposition References to Assess Facial Changes During Growth

“…Here, the CBCT derived facial surface models were used to assess the outcomes of 3D facial image superimposition techniques as related to the internal skeletal con guration. It has been shown that CBCT derived facial soft-tissue surface models are quite similar to those obtained by stereophotogrammetry 13,43,44 , allowing the assessment of changes in facial morphology in regards to standard reference structures, namely the anterior cranial base 3,4,8,18 . Thus, through the comparison with well-established anterior cranial base superimposition techniques 3,4,8,18 , the performance of the surfacebased techniques was thoroughly assessed.…”

“…Among others, this facilitates treatment decision-making and prediction of outcomes for ongoing or future interventions. The present study investigated, for rst time, various 3D facial surface superimposition areas in growing individuals and compared their applicability to those of a standard 3D anterior cranial base superimposition technique 4,8,21,25 , which has been previously validated 3,18,20 .…”

“…Furthermore, it shows a constant relationship over time to natural head position 47,48 , which represents the primary way people present themselves during everyday life interactions. These features have designated the anterior cranial base area as the gold standard, both for growing and non-growing individuals 4,8,18,21,25,39 . For this reason, we validated various facial surface superimposition techniques based on the comparison of their outcomes to those of the anterior cranial base superimposition.…”

“…The pairs of CBCTs (T0 and T1) were superimposed on the anterior cranial base (ACB) using a previously validated voxel-based best t approach 3,18,20 . Since the anterior cranial base is morphologically stable already at an early age 21,22 , it is located centrally in the craniofacial complex, and it has a steady relation to the natural head position 23 , superimposition in this area is considered a gold standard for the assessment of maxillofacial structures 4,8 . The selection of the reference area was performed on the CBCT T1, in a multiplanar view and consisted of a rectangular box of voxels, which included the anterior cranial base 3,18 .…”

“…Furthermore, there is no study comparing two facial surface superimposition methods to each other or to another method. Therefore, the present investigation assessed various 3D facial superimposition reference areas in growing patients, using CBCT derived data, and compared them to a voxel-based anterior cranial base (ACB) superimposition, which is considered the gold standard approach 3,8,18 .…”