Innovative method to assess maxillary arch morphology in oral cleft: 3d-3d superimposition technique

This study aimed to analyze the maxillary growth and development of children with oral clefts using the innovative method of 3D-3D superimposition technique. Children with unilateral complete cleft lip (UCL) and unilateral cleft lip and palate (UCLP) participated in the study. The impressions of the dental arches were executed 1 day before and 1 year after lip repair surgery. A 3D laser scanner digitized the dental models and the stereophotogrammetry system software analyzed the 3D-3D superimpositions in two groups of matches (same child, UCL and UCLP) and one group of mismatches (different individuals). The differences were evaluated by Root Mean Square (RMS) and expressed in millimeters (mm). Kruskal-Wallis test followed by post-hoc Dunn test and Mann-Whitney test were assessed to compare the groups (α=5%). RMS was 1.34 mm (± 0.37) in UCL group, 1.41 mm (± 0.32) in UCLP group, and 3.38 mm (± 1.28) in mismatches group. RMS was significantly greater in mismatches than in matches groups (p<0.0001). No statistically significant differences occurred between genders. The 3D-3D superimposition technique showed the maxillary development after lip repair surgery in the anterior region of the palate. Thus, it is suggested that the cleft amplitude and the palatal segments proportion influenced the morphological heterogeneity and, consequently, the development and maxillary growth of children with orofacial cleft.

Does the choice of the reference model affect the results of 3D-3D superimposition procedure? A comparison of different protocols for personal identification

In literature, 3D-3D superimposition has been widely recognized as a valid method for personal identification. However, very little information is available about possible variability due to differences in protocols of registration of 3D models and calculation of RMS (root mean square) point-to-point distance. Frontal sinuses from 50 CT scans were segmented twice through the ITK-SNAP software and grouped in two samples (1 and 2). Maximum breadth, height and volume were measured. 3D models belonging to the same subject were then superimposed one on each other in 50 matches. In addition, superimposition of 50 random mismatches was performed. For each superimposition, the procedure was repeated four times choosing different reference models both for registration and calculation of RMS. Differences in RMS value among protocols of registration and RMS calculation were assessed through paired Student’s t-test (p < 0.05). Possible correlations between differences in RMS among groups and differences in frontal sinus size between the superimposed models were analysed through calculation of Pearson’s correlation coefficient (p < 0.05). Results showed that RMS calculation did not yield significant differences according to which 3D model is used as reference; on the other hand, RMS values from registration procedure significantly differ according to which model is chosen as reference, but only in the mismatch group (p < 0.001). Differences in RMS value according to RMS calculation are dependent upon all the three measurements, whereas differences according to registration protocols were significantly related only with the breadth of frontal sinuses but only in mismatches (p < 0.001). In no case, superimpositions of RMS values were found between matches and mismatches. This article for the first time proves that the protocol of registration and calculation of RMS significantly influences the results of 3D-3D superimposition only in case of mismatches.

3D Method for Occlusal Tooth Wear Assessment in Presence of Substantial Changes on Other Tooth Surfaces

Early diagnosis and timely management of tooth or dental material wear is imperative to avoid extensive restorations. Previous studies suggested different methods for tooth wear assessment, but no study has developed a three-dimensional (3D) superimposition technique applicable in cases where tooth surfaces, other than the occlusal, undergo extensive morphological changes. Here, we manually grinded plaster incisors and canines to simulate occlusal tooth wear of varying severity in teeth that received a wire retainer bonded on their lingual surfaces, during the assessment period. The corresponding dental casts were scanned using a surface scanner. The modified tooth crowns were best-fit approximated to the original crowns using seven 3D superimposition techniques (two reference areas with varying settings) and the gold standard technique (GS: intact adjacent teeth and alveolar processes as superimposition reference), which provided the true value. Only a specific technique (complete crown with 20% estimated overlap of meshes), which is applicable in actual clinical data, showed perfect agreement with the GS technique in all cases (median difference: −0.002, max absolute difference: 0.178 mm3). The outcomes of the suggested and the GS technique were highly reproducible (max difference < 0.040 mm3). The presented technique offers low cost, convenient, accurate, and risk-free tooth wear assessment.