Superimposition Of Models Research Articles

TIP, TORQUE & ROTATIONS: How accurately do digital superimposition software\xa0packages quantify tooth movement?

BackgroundTo investigate the accuracy of three different 3D digital model registration software for tip, torque and rotation measurements, with reference to a 3D digital virtual setup. Twenty maxillary and mandibular pre-treatment scans of patients undergoing clear aligner therapy were used. Digital setups were generated from pre-treatment scans using a tooth movement software. Both the pretreatment digital scans (T1) and digital setups (T2) were converted to STL files to be exported to the 3 studied software that employed: (1) Semiautomatic best fit registration (S-BF), (2) Interactive surface-based registration (I-SB), and (3) Automatic best fit registration (A-BF) respectively. Changes in tip, torque and rotation were calculated for all the registered pairs.ResultsThe change in tooth position was compared between the calculated tooth movement using each of the registration software packages versus the actual generated tooth movement from the digital setups. Continuous data was expressed as mean and standard deviation. Intra Class Correlation Coefficient for agreement between digital simulation and each software was used. Intra and Inter-examiner reliabilities were also assessed using Intra Class Correlation Coefficient. Significance of the obtained results was expressed at p ≤ 0.01. Semiautomatic best fit registration software showed excellent agreement (> 0.90) for all tooth movements, except for good agreement for torque (0.808). Interactive surface-based registration software showed moderate agreement for all measurements (0.50 and < 0.75), except for good agreement for rotation (0.783). Automatic best fit registration software demonstrated excellent agreement (> 0.90) for rotation, good agreement for tip (0.890) and moderate agreement for torque (0.740).ConclusionsOverall, semiautomatic best fit registration software consistently showed excellent agreement in superimpositions compared to other software types. Automatic best fit registration software consistently demonstrated better agreement for mandibular superimpositions, compared to others. Accuracy of digital model superimpositions for tooth movements studied in superimposition studies, can be attributed to the algorithm employed for quantification.

A novel method of superimposing dentition on cone beam computed tomography images of the palatal mucosa coated with barium sulphate

ABSTRACT Purpose This study examined the accuracy of the superimposition of dentition on cone-beam computed tomography (CBCT) images using palatal mucosa with and without barium sulphate coating. Materials and Methods The heads of six slaughtered pigs (six months old) were used. Intraoral digital models of the upper molars and palatal and segmented data from CBCT images with and without barium sulphate coating were acquired from samples. We performed superimposition of intraoral digital models using the palatal soft-tissue portion to compare the superimposition errors between segmented data from CBCT with and without barium sulphate coating. Errors were calculated as the distances between the dentulous areas of the digital model and CBCT data. Results The average error of the superimposition with barium sulphate coating was 0.35 mm, and the maximum was 7.45 mm. When CBCT was performed without the palate being coated with barium sulphate, the average error was 2.16 mm with a maximum of 14.3 mm. Errors when CBCT images were obtained using barium sulphate were significantly smaller than when using uncoated images (p = 0.02). Conclusions A novel and non-invasive method for accurately superimposing an intraoral digital model on CBCT images based on palatal mucosa coated with barium sulphate was developed.

Efficiency evaluation of maxillary molar distalization using Invisalign based on palatal rugae registration

This study aimed to compare the predicted maxillary molar distalization with the achieved clinical outcome using the palatal rugae area for registration and superimposition of digital models. Understanding Invisalign efficiency may assist clinicians in predicting changes, thus applying specific measures to minimize the chance of midcourse correction later. The study sample included 38 patients with a mean age of 25.4 years, eligible for Invisalign treatment and requiring distalization of maxillary molars. Two digital models were acquired using iTero intraoral scanner (Align Technology, Santa Clara, Calif) before treatment and after maxillary first and second molar distalization. The 2 digital models were superimposed using the palatal rugae area for registration. The predicted tooth movement compared to the achieved values. One hundred forty-two maxillary molars (71 first molar and 71 second molar) were measured for distal movement, and 228 maxillary anterior teeth were evaluated for anterior anchorage loss. The predicted distal movement of the maxillary first molar (P<0.0001) and maxillary second molar (P<0.0001) differed significantly from the actual values. There was a statistically significant correlation between the amount of distal molar movement and the amount of anchorage loss (r= 0.3900, P<0.008) for the central incisor, and (r= 0.3595, P<0.013) for the lateral incisor. Invisalign can be used successfully for adult patients requiring maxillary molar distalization when a mean distalization movement of 2.6 mm was prescribed. Clinicians should be aware of the countereffect if maxillary molars are planned to move distally, especially if the patient presented initially with a large overjet, so the need to prescribe overcorrection or the use of auxiliaries can be addressed earlier.

Effects of Type and Amount of Orthodontic Tooth Movement on Digital Model Superimposition Accuracy

To assess the impact of type or amount of tooth movement on the success of 3D model superimposition by using two different algorithms. The sample consisted of pre-treatment digital maxillary models of forty patients. Eight different groups were created by applying 8 different virtual setups to each model. Teeth crowns were moved 1mm or 2mm in different directions (sagittal, transversal, vertical, combination) using the Ortho Analyzer software. Each model obtained from the virtual setup was overlapped with the original model using the landmark-based (LB) and local-best-fit (LBF) algorithms. In the post-superimposition assessment, the area of the palate vault which was not affected by teeth movements was selected. Both groups and algorithms were compared using RMS (root mean square) and PMA (percentage of perfectly matched areas) numeric data. In addition, the displacement of the right canine (RC) was measured after superimposition. The comparison of the superposition outcomes among the groups was evaluated with one-way ANOVA and Kruskal Wallis. The student t-test was used to compare two algorithms. Both algorithms were not affected by the type of tooth movement. However, the increase in the amount of tooth movement negatively affected the performance of the LB algorithm. LBF achieved the model superimpositions more effectively and faster than LB. No difference was found in RC measurements between the LB and LBF algorithms. The results indicate that LBF offers more sensitive and successful 3D superimposition models. The performance of the LB algorithm was, however, acceptable for analysis of 3D teeth movement.

Active nasoalveolar molding using 3-directional expansion screw for arch alignment in bilateral cleft lip and palate

• A 3-D expansion screw can retract protrusive premaxilla and expand cleft arches simultaneously. • This facilitates quick premaxillary distalization in newborn with bilateral cleft lip and palate. • A separate nasal stent can thus be given early corresponding to period of increased estrogen levels. The alignment of cleft segments is the primary step in presurgical orthopedics and is more critical in the bilateral clefts, in which the arch is segmented into 3 units. The projecting premaxilla poses a great challenge to the alignment of the segmented arch because of its unrestrained forward movement. The lateral segments are often collapsed with anterior narrowing. This results in great difficulty in correctly positioning the premaxillary segment during primary cheiloplasty as there is inadequate space available to align the anterior segment between the collapsed lateral segments. The current report suggests active nasoalveolar molding using a 3-directional expansion screw for simultaneous retraction of the anterior segment and the expansion of the lateral cleft segment to provide adequate space between them to receive the retracted segment. The nasal stent can be given as a separate entity very early in the treatment as the obscuring premaxilla is quickly retracted to allow for nasal stent attachment to the alae. Thus, nasal correction can be initiated early and independently from oral corrections. A 3-dimensional model superimposition revealed retraction of 2.8 mm of the premaxilla and 3.8 mm expansion during a treatment period of 3 months. The cleft defect was reduced by 4.8 mm on the right side and 10.2 mm on the left side, with all 3 cleft segments in good alignment. Good columellar elongation was achieved with satisfactory nasal contour and symmetry.

A novel computer-aided method for direct measurements and visualization of gingival margin changes.

To introduce and validate a computer-aided method for direct measurements and visualization of gingival margin (GM) changes. The method consists of five main steps: digital model acquisition, superimposition, computer-aided GM detection, distance calculation between the GM curves, and visualization. The precision of the method was evaluated with repeatability and reproducibility analysis (n=78 teeth). The method's repeatability was evaluated by repeating the algorithm on the same digital models by two operators. The reproducibility was evaluated by repeating the algorithm on two consecutive digital models obtained with a scan-rescan process at the same time point on the same patient. For demonstration, the proposed method for direct measurements of GM changes was performed on patients who had undergone root coverage procedures and treatment of periodontal disease. Excellent repeatability was found for both intra- and inter-operator variability, that is, 0.00 mm, regarding computer-aided GM detection. The reproducibility of computer-aided GM detection evaluated on scan-rescan models was 0.10 mm. The presented method enables the evaluation of GM changes in a simple, precise, and comprehensive manner through non-invasive acquisition and superimposition of digital models.

Accuracy of virtual surgical planning in segmental osteotomy in combination with bimaxillary orthognathic surgery with surgery first approach

BackgroundThis study aimed to assess the accuracy of virtual surgical planning (VSP) in segmental osteotomy in combination with bimaxillary orthognathic surgery with surgery first approach (SFA) by means of three-dimensional (3D) measuring and superimposition, so as to promote the application of digital technology in combined orthodontic-orthognathic treatment.Methods20 patients treated with segmental osteotomy in combination with bimaxillary orthognathic surgery with SFA from 2018 to 2020 were included. All of them acquired VSP performed by ProPlan CMF 3.0 software (Materialise Corporation, Belgium). The preoperative (T0) 3D model of VSP and the postoperative (T1) 3D model, reconstructed by the cone-beam computed tomography (CBCT) data acquired one week after surgery, were compared by measuring the 3D coordinates of the landmarks as well as 3D model superimposition for deviation analysis. The deviation analysis was achieved by Geomagic Studio 2013 (3D Systems Corporation, USA). The differences which represented the accuracy of VSP were evaluated by the root mean square deviation (RMSD) and the Bland–Altman method.ResultsThere was no statistically significant difference between the 3D coordinates of T1 and T0 (P > 0.05), and the mean overall RMSD was 1.37 mm, within the clinical relevance of 2 mm. The RMSD of sagittal direction (1.76 mm) was greater than that of coronal and vertical directions (1.09 mm and 1.24 mm), and the RMSD of maxillary and mandibular aspects were basically equal (1.30 mm and 1.45 mm). The Bland–Altman method showed the T0 and T1 measurements were in good agreement. The mean RMSD obtained from the deviation analysis was 1.85 mm, within the clinical relevance.ConclusionsVSP in segmental osteotomy in combination with bimaxillary orthognathic surgery with SFA proved to acquire accurate outcome in this study.

The effects of corticotomy and piezocision in orthodontic canine retraction: a randomized controlled clinical trial

BackgroundThe aims of this study were to evaluate the efficacy of alveolar corticotomy (AC) and piezocision (PZ) in accelerating maxillary canine retraction, and their effects on multiple bone remodeling expression in gingival crevicular fluid (GCF). A split-mouth, randomized controlled clinical trial was performed at the Department of Orthodontics of Pontifical Catholic University of Minas Gerais, Brazil. Eligibility criteria included orthodontic need for first maxillary premolars extractions, followed by canine retraction. Fifty-one adult patients were recruited and randomly assigned to 3 groups (allocation ratio 1:1:1). Random allocation of surgical or control interventions to each side of the maxillary arch was also conducted: G1 − AC × Control, G2 − PZ × Control, and G3 − AC × PZ. Both the definition of the group and the decision of the experimental or control sides were randomized by the software. Intraoral digital scans were performed before, 7 and 14 days after the beginning of canine retraction, and subsequently, at every 14 days until a maximum period of 6 months. GCF samples were collected before, and 1, 2, 4, 8, and 12 weeks. The primary outcome consisted in the cumulative distal movement of the canines and was measured by digital model superimposition. The secondary outcome consisted in GCF bone remodeling samples that were quantified in a multiplex immunoassay. The measurements examinator was properly blinded.ResultsForty-seven patients, 19 males and 28 females, were analyzed (mean age 20.72, SD = 6.66, range 15 to 38). Statistically significant differences in canine distal movement between AC and control in G1 were not observed (p > 0.05). In G2, PZ showed lower cumulative incisal and cervical measurements than control from the 2nd to the 24th week (p < 0.05). In G3, PZ showed a lower cumulative incisal and cervical measurements than AC from the16th to the 24th week (p < 0.05). In all groups, differences on biomarkers expression occurred at specific timepoints (p < 0.05), but a distinct pattern was not observed.ConclusionsAC and PZ were not effective to accelerate maxillary canine retraction and did not induce a distinct pattern of biomarker expression.Trial registrationNCT03089996. Registered 24 March 2017 - Registered.

Effects of submucosally administered platelet-rich plasma on the rate of tooth movement.

To evaluate the effects of submucosally administered platelet-rich plasma (PRP) on the rate of maxillary canine retraction. Levels of soluble receptor activator of nuclear factor-κb ligand (sRANKL) and osteoprotegerin (OPG) in the gingival crevicular fluid (GCF) were also measured over 2 months. This split-mouth trial involved 20 sites in 10 subjects randomly assigned to PRP (experimental) side and control side. After alignment, the freshly prepared PRP was injected submucosally distal to the experimental side maxillary canine, and retraction was performed using NiTi closed-coil springs (150 g) on 0.019 × 0.025-inch stainless steel wire. The rate of canine movement was assessed using digital model superimposition at 0, 30, and 60 days. The OPG and sRANKL were assayed using enzyme-linked immunosorbent assay from GCF collected at 0, 1, 7, 21, 30, and 60 days. Twenty sites were analyzed using paired t test. The rate of tooth movement increased significantly by 35% on the PRP side compared with the control side in the first month (P = .0001) and by 14% at the end of the second month (P = .015). Using the Mann-Whitney U test, OPG levels were found to be significantly decreased on the 7th (P = .003) and 30th day on the PRP side (P = .01), while sRANKL became detectable by the third week postinjection on the PRP side (P = .069). Submucosal injection of platelet-rich plasma significantly increased tooth movement during the 60-day observation period. Local injection of PRP significantly altered the levels of OPG and sRANKL in GCF.

Comparison of achieved and predicted crown movement in adults after 4 first premolar extraction treatment with Invisalign

In this study, we compared achieved and predicted crown movements of maxillary and mandibular first molars, canines, and central incisors in adults after 4 first premolar extraction treatment with Invisalign. Seventeen adult patients who received 4 first premolar extraction treatment with Invisalign and completed the first series of aligners were included. Superimposition of pretreatment and actual posttreatment dental models was acquired using registrations of pretreatment and posttreatment craniofacial models on the basis of bone surfaces and registrations of craniofacial and dental models on the basis of dental crown surfaces, respectively. Superimposition of pretreatment and predicted posttreatment models was acquired from ClinCheck software. Achieved and predicted 3-dimensional crown movements of maxillary and mandibular first molars, canines, and central incisors were then compared using the paired t test. Relative to predicted changes, first molars achieved greater mesial displacement, mesial tipping, and buccal inclination in both the maxilla and mandible, greater intrusion in the maxilla, and greater mesial-lingual rotation and less constriction in the mandible. Canines achieved greater distal tipping in both the maxilla and mandible, less retraction in the maxilla, and greater lingual inclination and extrusion in the mandible. Central incisors achieved greater distal tipping and lingual inclination and extrusion in both the maxilla and mandible and less retraction in the maxilla. Tooth crown movements were not fully achieved as predicted following Invisalign treatment. Differences focused on mesial tipping, buccal inclination, mesial displacement, and intrusion of the first molars, as well as distal tipping, lingual inclination, insufficient retraction, and intrusion of the canines and central incisors.

Intraoral scanners for capturing the palate and its relation to the dentition

Proper superimposition of intraoral scan generated 3D models enables detailed assessment of soft and hard tissue surface changes. This requires accurate 3D models and stable structures as superimposition references. In the maxilla, different reference areas have been proposed, mostly located at the palatal region. In this in vivo study we evaluated the precision of two intraoral scanners (TRIOS 3, 3Shape and CS 3600, Carestream) at the maxilla, focusing on the palate itself and also on its spatial relation to the dentition, following palatal superimposition. Precision was tested through the superimposition of repeated scans on the palate and the dental arch. Overall, the median precision of both scanners was high (< 0.1 mm). Scanner precision was comparable when the palatal area was tested individually. However, TRIOS 3 showed higher precision regarding the assessment of the dental arch, following superimposition of repeated models on the palate (median difference: approximately 40 μm). In few cases, local areas of higher imprecision were present for both scanners, exceeding 0.3 mm. Thus, scanner precision seems to be high in small, but slightly reduced considering larger areas, with differences between scanners. However, the effect on individual tooth position relative to the palate was for both scanners limited.

Comparison of the efficacy of two-time versus one-time micro-osteoperforation on maxillary canine retraction in orthodontic patients: A split-mouth randomized controlled clinical trial

Micro-osteoperforation (MOP), a minimally invasive technique for accelerating the rate of orthodontic tooth movement has been research extensively, but with varied clinical results. To compare the efficacy of one-time versus two-time micro-osteoperforation on the rate of maxillary canine retraction, its influence on anchorage loss, canine angulation and the levels of interleukin (IL-1β) in gingival crevicular fluid (GCF). The split-mouth study included 16 patients in which the left and right sides were randomly allocated to the control side (one-time MOP) and experimental side (two-time MOP). MOP was performed on both sides distal to the maxillary canines and canine retraction was carried out using NiTi closed coil springs (150gm) and direct anchorage with miniscrew implants. The second MOP was performed on experimental side one month after the first MOP. The rate of canine movement was assessed using 3D model superimposition over a period of six months. The type of tooth movement, anchorage loss and levels of IL-1β were also evaluated. Sixteen patients (mean age, 17.87±3.34 years) were analysed for a rate of canine retraction, anchorage loss, and type of tooth movement, while 15 patients were analysed for IL-1β. The rate was significantly higher on two-time MOP side after two months (P<0.001). No statistical difference was found in anchorage loss and controlled tipping of canines was observed. The IL-1β levels immediately after 2nd MOP were significantly higher than 1st MOP (P<0.001). The two-time intervention of MOP is more efficacious than one-time MOP in accelerating tooth movement.

Maxillary expansion with clear aligners in the mixed dentition: A preliminary study with Invisalign® First system.

The aim of this study was to evaluate maxillary arch changes in patients treated with Invisalign® First system in the mixed dentition, focusing on arch width, arch perimeter, arch depth, molar inclination and alveolar expansion. A retrospective study was carried out. The sample consisted of 20 patients, 12 females and 8 males, treated with clear aligners for maxillary expansion. Arch widths, arch perimeter, arch depth and molar inclination were measured on pre-treatment and post-treatment digital dental models. Superimposition of digital models was performed to evaluate alveolar expansion. There were significant increases in all measurements regarding arch width and arch perimeter, while arch depth and molar inclination significantly decreased. Alveolar expansion was recorded at all the reference points considered. Shapiro-Wilk test was used to check normal distribution. Average and standard deviations were calculated for all measurements. Paired t-test was run to report significant changes between T0 and T1. The statistical significance was set at p<0.05. Intraclass correlation coefficient was used to assess reliability. In case of mild crowding or limited transverse maxillary deficiency, Invisalign® First clear aligners could be a reasonable alternative to traditional slow maxillary expanders.

Healing of Post-Extraction Sockets Filled with Anorganic Bovine Bone and Covered with a Xenogeneic Collagen Matrix. Radiological 2D and 3D Results of a Pilot Study to Assess Dimensional Stability.

Analysis of short-term results regarding dimensional stability of post-extraction sockets managed via a preservation protocol using deproteinized bovine bone matrix and a xenogeneic collagen matrix. Materials and methods Fifteen patients needing extraction of one single-rooted premolar tooth were treated in a pilot study. Five patients were treated in each centre. After tooth extraction, sockets were filled with anorganic bovine bone matrix and covered with a xenogeneic collagen matrix. Six months later, implants were placed. Dimensional changes in the treated sites were digitally evaluated using the best-fit superimposition of pre-and post-socket preservation models. Results After six months of healing, the vertical reduction of the grafted sites was 0.31 ± 0.24 mm (p < 0.001). Volumetric analysis of superimposed models showed an average palatal-lingual contraction of 0.33 ± 0.51 mm3 (p = 0.02). At the vestibular level, the average contraction was found to be 0.8 ± 0.3 mm3 (p < 0.001). Finally, the analysis of linear variations in the treated sites on a single sagittal section at the crystal level, and at 3 and 7 mm apically respect to the crest, both towards the vestibule and palate, generally showed more marked resorption at the crestal level compared to apical measurements. Conclusion: The clinical protocol herein employed for socket preservation showed a positive effect in preventing the physiological post-extraction remodeling.

Buccal Pedicle Flap Combined With Porcine Collagen Matrix: A Follow‐Up of 2 Years on 40 Consecutive Cases

A thick peri-implant mucosa is of importance to prevent recession, color alterations, bone remodeling and promote "creeping attachment." A volume stable porcine cross-linked collagen matrix has been recently introduced for soft tissue regeneration and volume maintenance. The aim of this study was to investigate peri-implant soft tissue healing and stability on 40 consecutive patients treated with buccal pedicle flap combined with the use of the collagen matrix. The buccal pedicle flap combined with a volume stable collagen matrix was executed at second stage surgery. The average initial mucosa thickness was 1.32 mm whereas the average band of keratinized mucosa was 1.65 mm and the height 1.3 mm. Four months after surgical procedure and before delivering the final restoration, the peri-implant soft tissue measurements were significantly increased: the average band of keratinized mucosa was 5.10 mm, the mucosa thickness was 3.27 mm, and the mucosa height was 3.32 mm. After 2 years of follow-up, the superimposition of 3D models described an overall volumetric stability of the augmented mucosa with no signs of soft tissue collapse. The proposed modified buccal pedicle flap was demonstrated to perform well in terms of decreased morbidity, maintenance of blood supply, stabilization of the pedicle, superior haemostasis, and speed of treatment. No significant variations of the keratinized tissue were registered when the buccal pedicle flap was executed in conjunction with the collagen matrix that however provided color match with the surrounding tissue as well as an increased mucosa thickness.

Computer-aided superimposition of the frontal sinus via 3D reconstruction for comparative forensic identification.

The anatomical uniqueness of the frontal sinus morphology has been widely used for comparative forensic identification using various techniques, mostly including 2D X-rays or one fixed slice of an axial computed tomography (CT) scan image. However, computer-aided 3D automatic graphical comparison techniques can provide accurate comparisons between two 3D models that allow users to comply with even the strictest deviation standards, avoiding error-prone identification of frontal sinuses with similar morphologies. The study proposes the use of a computer-aided comparative paradigm based on the 3D-3D frontal sinus model superimposition process and further assesses the anatomical uniqueness of frontal sinuses using a large Chinese Han sample. Three hundred thirty-six patients older than 20years with two multi-slice CT scans were collected. Frontal sinus 3D models were semi-automatically segmented through Dolphin Imaging software. Automatic pairwise comparisons of 336 matched pairs from the same person and 340 mismatched pairs from different individuals with an analysis of average root mean square (RMS) point-to-point distance were performed using Geomagic Studio Qualify software. RMS ranged between 0.005 and 1.032 (mean RMS 0.390 ± 0.25mm) in the group of matches and between 1.107 and 19.363 (mean RMS 4.49 ± 2.69mm) in the group of mismatches. On average, the RMS value was over ten-fold greater in mismatches than in matches. Statistically significant differences in RMS between the group of matches and mismatches were assessed using the Mann-Whitney U test (p < 0.05). This study supports the value of the frontal sinus with a 3D computer-aided superimposition method for human identification with large samples when DNA, fingerprints, and dental materials are not accessible.

Insights on the Structural Variations of the Furin-Like Cleavage Site Found Among the December 2019-July 2020 SARS-CoV-2 Spike Glycoprotein: A Computational Study Linking Viral Evolution and Infection.

The SARS-CoV-2 (SARS2) is the cause of the coronavirus disease 2019 (COVID-19) pandemic. One unique structural feature of the SARS2 spike protein is the presence of a furin-like cleavage site (FLC) which is associated with both viral pathogenesis and host tropism. Specifically, SARS2 spike protein binds to the host ACE-2 receptor which in-turn is cleaved by furin proteases at the FLC site, suggesting that SARS2 FLC structural variations may have an impact on viral infectivity. However, this has not yet been fully elucidated. This study designed and analyzed a COVID-19 genomic epidemiology network for December 2019 to July 2020, and subsequently generated and analyzed representative SARS2 spike protein models from significant node clusters within the network. To distinguish possible structural variations, a model quality assessment was performed before further protein model analyses and superimposition of the protein models, particularly in both the receptor-binding domain (RBD) and FLC. Mutant spike models were generated with the unique 681PRRA684 amino acid sequence found within the deleted FLC. We found 9 SARS2 FLC structural patterns that could potentially correspond to nine node clusters encompassing various countries found within the COVID-19 genomic epidemiology network. Similarly, we associated this with the rapid evolution of the SARS2 genome. Furthermore, we observed that either in the presence or absence of the unique 681PRRA684 amino acid sequence no structural changes occurred within the SARS2 RBD, which we believe would mean that the SARS2 FLC has no structural influence on SARS2 RBD and may explain why host tropism was maintained.

Assessment of reference areas for superimposition of serial 3D models of patients with advanced periodontitis for volumetric soft tissue evaluation

This study aimed to determine the optimal reference area for superimposition of serial 3D dental models of patients with advanced periodontitis. Ten pre- and post-periodontal treatment 3D models (median time lapse: 13.1months) of patients with advanced periodontitis were acquired by intraoral scanning. Superimposition was performed with the iterative closest point algorithm using four reference areas: (A) all stable teeth, (B) all teeth, (C) third palatal rugae and (D) the whole model. The superimposition accuracy was evaluated at two stable evaluation regions using the mean absolute distance and evaluated with two-way ANOVA and post-hoc multivariate model. The intra- and inter-operator reproducibility was calculated by intraclass correlation coefficient (ICC). Superimposition accuracy evaluated at stable tooth evaluation region were 71±29μm, 73±21μm, 127±52μm and 113±53μm for areas A, B, C and D, respectively. All reference areas showed similarly high ICC values >0.990, except for reference area C showing ICC of 0.821 (intra-operator) and 0.767 (inter-operator) for tooth evaluation area. Area A and B provide the highest accuracy for superimposition of serial 3D dental models acquired by intraoral scanning of patients with advanced periodontitis.

An Augmented Reality inspection tool to support workers in Industry 4.0 environments

Among the key technologies of Industry 4.0, Augmented Reality (AR) is one of the most promising and enabling technologies for supporting factory workers and engineers at the workplace. To this end, the paper proposes a novel AR tool to assist operators during the inspection activities for the detection of production and assembly errors. In fact, thanks to the superimposition of the 3D models, as designed by the technical office, a worker can easily detect the presence of design discrepancies on the final physical assembled product and report them by adding 3D annotations directly on virtual models.This AR tool has been developed by using ARCore™ libraries to ensure, in the first place, its compatibility with commonly used devices for which workers are already trained and, secondly, to take advantage of the hybrid-tracking techniques that combine vision- and sensor-based methods to improve the reliability of the AR visualization. Nevertheless, the proposed AR tool adopts multiple markers to minimize tracking errors and therefore to provide greater freedom of movement to the user, who can use the tool also for the assessment of large-size products.Field experimentations have been carried out on a real case study with end-users in order to assess its usability and perceived mental workload through the SUS (System Usability Scale) and NASA-TLX (Task Load Index) standard questionnaires, respectively. The usability study was performed taking into account also objective metrics, i.e., by analysing user performance in target acquisition tasks while interacting with the AR tool. Statistical analysis proved that the adoption of this AR tool requires low mental demand, and its usability has reached a high level of satisfaction both by the factory workers and engineers involved in the user study.

The influence of the model superimposition method on the assessment of accuracy and predictability of setup models.

The aim of this study was to evaluate the influence of different superimposition methods on the accuracy and predictability of conventional and virtual diagnostic setups. Ten finished cases were used to make aconventional setup and avirtual setup. Second molars were not moved in the two setup situations to allow areference for superimposition. Conventional and virtual setups were superimposed and compared by second molar registration and the whole surface best fit method (WSBF). Conventional and virtual setups were compared to the posttreatment models with WSBF and palatal rugae best fit (PRBF). Anterior, intermediate, and posterior regions of the dental arches were compared. The paired t-test was used to compare the mean differences between conventional and virtual setups, posttreatment models and both conventional and virtual setups by the WSBF method, and between maxillary posttreatment and virtual setup models using the WSBF and PRBF methods. Conventional and virtual setups differed depending on the two superimposition methods used. Superimposition of the posttreatment models and both setups using WSBF presented no statistically significant differences. There were statistically significant differences between posttreatment and virtual setup models using WSBF and PRBF superimposition methods. The model superimposition method influenced the assessment of accuracy and predictability of setup models. There were statistically significant differences between the maxillary posttreatment and virtual setup models using the WSBF and the PRBF superimposition methods. It is important to establish stable structures to evaluate the accuracy and predictability of setup models.