Reference Scan Research Articles

Digitization of Dentate and Edentulous Maxillectomy and Mandibulectomy Defects with Three Different Intraoral Scanners: A Comparative In Vitro Study

Objectives: The objective of this study was to compare the trueness and precision of three intraoral scanners (IOSs) for the digitization of dentate and edentulous maxillectomy and mandibulectomy defects in artificial models. Methods: Four representative defect models—a dentate and an edentulous maxillectomy model and a dentate and an edentulous mandibulectomy model—were used for digital scanning. After a reference scan of each model, they were scanned with three IOSs: CEREC AC Omnicam, True Definition, and cara TRIOS 3. For comparison, five conventional impressions with a polysiloxane material were taken and digitized with a laboratory scanner. The obtained data were evaluated with three-dimensional (3D) inspection software and superimposed with the reference scan data by using a best-fit algorithm. The mean absolute 3D deviations of the IOS compared to the reference data (trueness) and when comparing the datasets within the IOS (precision) were analyzed. Linear mixed models and multiple pairwise comparisons were used for statistical analyses. Results: The overall comparison of the four evaluated procedures for data acquisition showed a significant difference in trueness (p < 0.0001) and precision (p < 0.0001). The average mean trueness of the IOSs ranged from 32.17 to 204.43 µm, compared to 32.07 to 64.85 µm for conventional impressions. Here, the conventional impression and cara TRIOS 3 performed the most precisely with no significant difference. CEREC AC Omnicam achieved the worst precision. Conclusions: Using a suitable intraoral scanner, defective jaws even without teeth could be captured in satisfying accuracy. This shows the possibility to use an intraoral scanner for maxillofacial defect patients and gives a vision of using digital technology in maxillofacial prosthetics.

Accuracy of different maxillomandibular relationship recording techniques in the edentulous maxillary arch.

This study investigated the effect of three digital bite registration techniques on the accuracy of intraoral scanning in maxillary edentulous and mandibular dentate arches. Maxillary edentulous and mandible fully dentate models were created. Four dental implants were placed in the maxilla, fitted with scan bodies, and reference scans were obtained using a Nikon Altera 10.7.6 scanner. Digital impressions were acquired 10 times for each model using a Trios 4 intraoral scanner. Three different digital bite records were collected for each pair of mandible and maxilla scans. The first one was a bite record without additional material (WSB), the second utilized a silicone index between the models (WSB silicone), and the third followed a pre-preparation scanning protocol (Pre-PREP). The data was exported in standard tessellation language (STL) format, which was assessed for trueness and precision using statistical analysis. According to mean trueness values, WSB exhibited the lowest value, 173 µm, followed by WSB silicone 242 µm and Pre-PREP 620 µm. The differences were significant only when comparing Pre-PREP to WSB and Pre-PREP to WSB silicone (p <0.05). Regarding precision, WSB demonstrated a mean value of 171.5 µm, followed by WSB silicone with 213.8 µm, and Pre-PREP with 222.2 µm with no significant difference between the groups. The presence of interarch bite registration material adversely affected interocclusal record accuracy, while WSB silicone presented a suitable substitute for WSB.

Influence of operator experience on the complete-arch accuracy and time-based efficiency of three intraoral scanners

Background/purposeThe performance of intraoral scanners (IOSs) relies on the operator's skills. However, whether operator experience influences IOS accuracy remains unclear. This study investigated the effect of operator experience on the trueness accuracy and time-based efficiency of IOSs. Materials and methodsThirty operators were equally divided into two groups on the basis of their IOS-handling experience. Each operator performed simulation scans of a maxillary model in a training dummy by using three IOSs: CEREC Omnicam, Primescan, and Aoralscan 3. A total of 90 scans were generated, and the scan time for image acquisition and the render time required for an IOS to generate a three-dimensional image were recorded. The trueness of each scan was calculated by comparing with a reference scan obtained from an industrial high-precision scanner. The t test and the ANOVA followed by the Tukey post hoc test were used to determine statistical differences. Significance was set at P < 0.01. ResultsFor the three IOSs, no significant difference was noted in trueness accuracy, scan time, or render time between inexperienced and experienced operators. For both inexperienced and experienced operators, Omnicam had significantly less accuracy and longer scan time than did the other IOSs; the render time was significantly shorter for Aoralscan 3 than for the other IOSs. ConclusionOperator experience does not substantially influence the trueness accuracy and time-based efficiency of IOSs; these factors vary across IOS types. The render time for obtaining three-dimensional images is a significant feature for improving the time-based efficiency of IOSs.

Toward a whole-of-virtual school framework for promoting student physical activity: a scoping review protocol

BackgroundThe advent of full-time virtual schooling presents unique challenges and opportunities for the promotion of physical activity (PA) among children and adolescents. Despite the recognized benefits of PA as an essential component for combating non-communicable diseases and ensuring holistic development, there is a notable gap in understanding how to effectively integrate PA within the digital learning environments of full-time virtual schools. Current efforts to promote student PA are targeted for implementation exclusively in contexts characterized by physical school campuses that are bound to their surrounding local communities. This is problematic given the digital, widely distributed, and contextually unmoored nature of virtual schooling. Our aim in this scoping review is to advance research on whole-of-school physical activity promotion within full-time virtual schools by examining the published literature on whole-of-school PA promotion within full-time virtual schools. Specifically, this review will map the literature, consolidate knowledge claims and practical implications, and identify evidence gaps that merit further investigation.Methods/designThis review will be conducted using evidence-informed scoping review methodology and reporting guidelines. Articles will be included if they are peer-reviewed English-language research, commentary, practical, or grey literature and relate to the participation, support, design, development, and/or provision of remote online PA interventions delivered through primary/elementary and/or secondary/middle school/high schools. Searches will be conducted in PsycInfo, ERIC, SportDiscus, and Web of Science. Additional hand-searching, reference scans, and grey literature searches will also be performed. Two trained research assistants will independently complete study screening and selection and data charting with guidance from a senior author. Charted data will be displayed in table form, and depending on the results, data will also be synthesized through qualitative content analysis using the Active Schools guiding framework as an analytical and interpretive lens.DiscussionThis scoping review will serve as a guidepost for the application and advancement of research on whole-of-school PA promotion through full-time virtual schools. The results will address the increased importance of equitable online learning and PA promotion due to the expanding virtual education landscape, with implications for public health and education policy.Systematic review registrationOpen Science Framework: https://osf.io/f6wau/.

Comparison of trueness, time, and number of images among different denture digitization protocols

AbstractPurposeTo compare trueness, time, and number of images of different denture digitization protocols.Materials and MethodsMaxillary and mandibular complete prostheses (n = 10) were fabricated and attached with four fiducial markers. Reference scans were obtained using a laboratory scanner. Test scans were obtained using three different protocols: intraoral scanner (IOS) with manufacturer's scanning pattern (MA), IOS with rolling scanning pattern (RO), and IOS‐ polyvinylsiloxane technique (IOS‐PVS). The scan time and number of images taken were recorded for analysis. Using 3‐dimensional (3D) inspection software (Geomagic control X), corresponding test scans were superimposed to the reference scan using overall best fit. For trueness analysis, the root mean square (RMS) value of the overall best‐fit superimposition was calculated. One‐way ANOVA followed by Games‐Howell and Tukey post‐hoc tests were applied to analyze trueness, scan time, and number of images. Qualitative analysis of trueness was performed using 3D color mapping.ResultsThe lowest RMS value was in the mandibular RO protocol (0.10 ±0.01 mm). The highest RMS value was mandibular scans of the IOS‐PVS protocol (1.46 ± 0.09 mm). The longest digitization time was recorded in the maxillary MA group (3.34 ± 0.70 min), while the shortest was in the mandibular RO protocol (2.48 ± 0.56 min). Qualitative analysis revealed that deviation in IOS‐PVS protocol occurred around the border area of the prosthesis.ConclusionThe denture digitization protocols tested significantly affected trueness, total scanning time, and number of images. Digitizing dentures using the RO protocol improved trueness and reduced scanning time and the number of images.

Deep learning-based whole-brain B1 +-mapping at 7T.

This study investigates the feasibility of using complex-valued neural networks (NNs) to estimate quantitative transmit magnetic RF field (B1 +) maps from multi-slice localizer scans with different slice orientations in the human head at 7T, aiming to accelerate subject-specific B1 +-calibration using parallel transmission (pTx). Datasets containing channel-wise B1 +-maps and corresponding multi-slice localizers were acquired in axial, sagittal, and coronal orientation in 15 healthy subjects utilizing an eight-channel pTx transceiver head coil. Training included five-fold cross-validation for four network configurations: used transversal, sagittal, coronal data, and was trained on all slice orientations. The resulting maps were compared to B1 +-reference scans using different quality metrics. The proposed network was applied in-vivo at 7T in two unseen test subjects using dynamic kt-point pulses. Predicted B1 +-maps demonstrated a high similarity with measured B1 +-maps across multiple orientations. The estimation matched the reference with a mean relative error in the magnitude of (2.70 ± 2.86)% and mean absolute phase difference of (6.70 ± 1.99)° for transversal, (1.82 ± 0.69)% and (4.25 ± 1.62)° for sagittal ( ), as well as (1.33 ± 0.27)% and (2.66 ± 0.60)° for coronal slices ( ) considering brain tissue. trained on all orientations enables a robust prediction of B1 +-maps across different orientations. Achieving a homogenous excitation over the whole brain for an in-vivo application displayed the approach's feasibility. This study demonstrates the feasibility of utilizing complex-valued NNs to estimate multi-slice B1 +-maps in different slice orientations from localizer scans in the human brain at 7T.

Effects of Operator Experience and Scanning Distance on Intraoral Scanner Accuracy

Aim: This study aimed to evaluate the effect of operator experience and scanning distance on the accuracy of the intraoral scanner in terms of trueness and precision. Material and Methods: Reference data were obtained by scanning a partially edentulous gypsum model with implant analogs in regions 15, 16, 26, and 27 using a desktop scanner. Two expert dentists, one experienced and one inexperienced, performed test scans using the Trios 5 scanner. All data were transferred to analysis software. The scan bodies in the test scans were superimposed with the reference scan bodies for trueness measurement using a best-fit algorithm, calculating the deviation between the datasets. Precision measurement involves aligning the test scan data with each other using the same method. The effect of operator experience and scanning distance on scanner accuracy was evaluated using independent-sample t-tests. Results: Full-arch scans exhibited higher trueness and precision deviations than partial-arch scans. For partial-arch scans by the experienced operator, the mean trueness deviation was 7.45µm, compared to 55.56µm for full-arch scans (p&lt;0.001). Inexperienced operator results were 7.60µm and 58.90µm, respectively (p&lt;0.001). Operator experience had no significant effect on trueness. For partial-arch scans performed by the experienced operator, the mean precision deviation was 2.73µm, compared to 33.87µm for full-arch scans (p&lt;0.001). Inexperienced operator results were 3.36µm and 39.79µm, respectively (p&lt;0.001). Operator experience significantly affected precision in partial-arch scans (p=0.044) but not in full-arch scans (p=0.563). Conclusion: Scanner accuracy decreased with increasing scanning distance. The effect of operator experience on scanner accuracy was insignificant.

Scan accuracy of wireless intraoral scanners while digitizing a combined scan body-healing abutment system

ObjectivesTo investigate the accuracy (trueness and precision) of wireless and wired intraoral scanners (IOSs) when scanning an implant with the combined healing abutment-scan body (CHA-SB) system. MethodsA partially edentulous mandibular model with a CHA-SB at the right first molar site was digitized with 2 wireless (NeoScan 2000 (NW) and TRIOS 4 wireless (T4 W)) and 2 wired (NeoScan 1000 (N) and TRIOS 4 wired (T4)) IOSs 44 times in total (n = 11). The reference scan file was generated by digitizing the same master model and CHA-SB with an industrial-grade optical scanner. All files were imported into a metrology-grade analysis software program to evaluate the surface (root mean square, RMS), linear, and angular deviations of the top part of the SB. The average deviation values defined the precision of the scans. The data were statistically analyzed (α = 0.05). ResultsIOS type affected the surface and angular deviations and the precision (linear deviations on the x-axis) of the scans (p ≤ 0.043). T4 W had lower RMS than N and T4 (p ≤ 0.031). T4 had higher angular deviations than N on the XZ plane and had the lowest angular deviations on the YZ plane (p ≤ 0.011). T4 W scans had higher precision than N scans (p = 0.024). ConclusionDespite some differences in the trueness or precision of scans, tested IOSs mostly enabled similar scan accuracy. Regardless of the IOS, the implant scans had a tendency to tilt mesiobuccally, which can be considered clinically small. Clinical SignificanceTested wireless intraoral scanners may be suitable alternatives to their wired counterparts while digitizing an implant with a combined healing abutment-scan body system in the posterior region. However, the crowns fabricated from tested scans might require buccal, mesial, and occlusal surface veneering and distal surface adjustments.

Creating an effective curriculum for cosmetology students to promote early detection of melanoma in salons and barber shops: a scoping review

This scoping review aims to summarize available research literature on previous skin cancer educational programs among hair professionals or cosmetology students to inform the creation of an effective cosmetology school curriculum that will promote early detection of melanoma on the scalp and neck. Cutaneous melanoma on the scalp and neck is a significant cause of morbidity and mortality in the United States, and the number of new cases continues to rise. Hair professionals can detect this cancer by regularly inspecting the skin under these hair-bearing areas. Providing skin cancer education to cosmetology students can potentially affect significant changes in screening and referral practices, improving the stage at which this cancer is treated. All articles in this study involved hair professionals or cosmetology students in the context of hair salons, barbershops, or cosmetology schools. These articles included a focus on skin cancer or melanoma education. A systematic search of electronic databases (CINAHL, MEDLINE, Science Direct, and Google Scholar) for full-length, peer-reviewed journal articles written in English in the last 20 years was performed in August 2022 and January 2023. Articles were initially screened by title, abstract, and keywords, followed by full-length review and reference scanning. Data were systematically extracted from included articles, summarized, and presented in narrative and table form. Search terms included “hairdressers, barbers, cosmetology students, salons, barbershops, cosmetology schools, education, curriculum, intervention, knowledge, skin cancer, and melanoma." Thirteen sources of evidence were included in the review, all of which were empirical research studies. Nine studies evaluated the effectiveness of a skin cancer educational intervention for hair professionals or cosmetology students, and 4 assessed skin cancer knowledge, attitudes, or beliefs in this population. All interventions improved knowledge, confidence, screening behaviors, or referral practices in hair professionals or cosmetology students. No specific educational modality was more effective than another, no apparent difference was seen with different intervention lengths, and the type of information included within each educational modality was rarely discussed. Most hair professionals believe they lack adequate training or confidence in skin cancer detection and are interested in becoming educated on this subject. Short videos or live lectures were the preferred skin cancer educational modalities among hair professionals and cosmetology students. Brief skin cancer educational programs improve cosmetology students and hair professionals’ knowledge about melanoma and screening practices. This population has a perceived and measured need for skin cancer education. Including this type of program in the cosmetology school curriculum can effectively disseminate information to these individuals, leading to earlier diagnosis of melanomas on the scalp and neck, thus decreasing the mortality rate of this disease. Further research, including larger, diverse samples and more rigorous study designs, is needed to bolster the results of the review findings.

The use of plasma exchange with albumin replacement in the management of Alzheimer's disease: a scoping review.

AD is a progressive neurodegenerative disorder causing significant cognitive decline and impaired daily functioning. Current treatments offer only modest relief, and many amyloid-targeting therapies have failed, prompting exploration of alternative approaches such as PE with albumin replacement. This scoping review systematically maps the literature on PE with albumin replacement in AD management, focusing on outcomes, methodologies, and reported benefits and risks. A comprehensive search in PubMed, supplemented by reference scanning and hand-searching, identified studies involving PE with albumin replacement in AD patients. Data charting and critical appraisal were conducted using standardized tools. Seven primary studies from the AMBAR (Alzheimer Management by Albumin Replacement) trial met the inclusion criteria, consistently reporting improvements in cognitive function, positive neuroimaging results, and favorable neuropsychiatric outcomes. For instance, one study found a significant slowing of cognitive decline (p < 0.05) among patients receiving PE with albumin replacement. Another study showed better preservation of hippocampal volume and improved brain perfusion metrics in the treatment group (p < 0.05). The intervention was generally well-tolerated with manageable side effects. PE with albumin replacement is a promising therapeutic approach for AD, warranting further investigation to confirm its efficacy and safety across broader settings. https://osf.io/v6dez/?view_only=1cd9637e7e0347d39713bf19aac0dfe8.

Custom integration of a magnetic-field monitoring system into a 32-channel MRI head coil.

Customizing a Siemens 32-channel coil for use in a Philips 3T MRI system with incorporated magnetic field probes for collecting high-quality MRI and magnetic-field monitoring data concurrently. The development process of the custom coil involved several (iterative) phases. Standard temporal SNR and B1 + data were collected with the 32-channel Siemens and for reference the 32-channel/8-channel Philips head coils before and afterthe custom coil was made compatible with the 3T Philips Achieva system, and magnetic field probes were installed into it along with ancillary electronics around it. Quality assurance tests were conducted in each of the build phases to ensure that the modifications did not affect MRI or field-monitoring data negatively. To test the finished custom coil, we collected high angular resolution diffusion imaging (HARDI) datasets on a spherical silicon oil phantom both with and without concurrent field monitoring and a 32-channel Philips coil without concurrent field monitoring, where the latter two served as reference scans to assess the improved performance of the custom coil with field monitoring. Similar HARDI-MRI data were also collected in vivo with the finished custom coil together with field monitoring data. The custom coil provided excellent temporal SNR especially at the edges where cortical gray matter is expected. When using concurrent field monitoring in HARDI acquisitions, the custom coil alleviated ghosting artifacts in phantom data and provided in vivo images with 1.4-mm isotropic resolution. The custom MRI coil with integrated magnetic-field monitoring probes provided improved imaging performance.

Influence of short-span scans on trueness in the digital transfer of the maxillomandibular relationship

ObjectivesThis study aimed to assess the influence of the location and distribution of short-span scans, serving as intermediate registration data, on the trueness of digitally transferring the maxillomandibular relationship in full-mouth rehabilitation. MethodsMaxillary and mandibular complete-arch preparation casts mounted on an articulator were scanned, with and without interim restorations, using an intraoral scanner. Four types of short-span scans—right anterior, left anterior, right posterior, and left posterior—were captured from maxillary and mandibular casts. Each scan comprised two prepared teeth and two crowned teeth arranged alternately. These short-span scans served as intermediate data and were cross-registered with complete-arch interim restorations and preparation casts to transfer the maxillomandibular relationship. Based on the number (1 or 2), location (anterior or posterior), and distribution (unilateral or bilateral) of short-span scans, they were categorized into six groups. Trueness was assessed by evaluating the mandibular 3-dimensional (3D), spatial distance, angle, and linear distance deviations between the test and reference scans. ResultsSignificant differences in the trueness of digital cross-mounting were observed among the six groups (P < .05). The group registering the bilateral posterior areas exhibited the smallest 3D, spatial distance, angle, and linear distance deviations, whereas the group registering one anterior area showed the largest deviations. ConclusionThe number, location, and distribution of the registered short-span scans significantly affected the trueness of transferring the maxillomandibular relationship. A posterior short-span scan had higher trueness than an anterior scan. The symmetrical distribution of the two registered larger short-span scans over the cross-arch enhanced the registration trueness. Clinical significanceDigital cross-mounting in full-mouth rehabilitation using short-span scans enhances transfer accuracy, improves patient comfort, and increases chairside efficiency.

Evaluating the accuracy of CEREC intraoral scanners for inlay restorations: impact of adjacent tooth materials

BackgroundThe accuracy of intraoral scanning is critical for computer-aided design/computer-aided manufacturing workflows in dentistry. However, data regarding the scanning accuracy of various adjacent restorative materials and intraoral scanners are lacking. This in vitro study aimed to evaluate the effect of adjacent restorative material type and CEREC's intraoral scanners on the accuracy of intraoral digital impressions for inlay cavities.MethodsThe artificial tooth was prepared with an occlusal cavity depth of 2 mm, a proximal box width at the gingival floor of 1.5 mm, and an equi-gingival margin extended disto-occlusally at the transition line angle on both the lingual and buccal sides for an inlay restoration. The adjacent teeth were veneered with crowns made of gold and zirconia, and an artificial tooth (resin) was utilized as the control group. The inlay cavity and adjacent teeth (Gold, Zirconia, and resin) were scanned 10 times using Chairside Economical Restoration of Esthetic Ceramics (CEREC) Primescan (PS), Omnicam (OC), and Bluecam (BC). A reference scan was obtained using a laboratory scanner (3-shape E3). Scanning was performed according to the manufacturer's instructions, including powder application for the BC group. Standard tesselation language files were analyzed using a three-dimensional analysis software program. Experimental data were analyzed using a two-way analysis of variance and the Tukey’s post-hoc comparison test.ResultsThe restorative materials of the adjacent teeth significantly affected the accuracy of the intraoral digital impressions (p < .05). The zirconia group exhibited the highest trueness deviation, followed by the resin and gold groups, with each demonstrating a statistically significant difference (p < .05). The resin group demonstrated the highest maximum positive deviation and deviation in precision. Gold exhibited the lowest average deviation value for trueness compared with those of the other adjacent restorative materials. Intraoral scanner type significantly influenced the trueness and precision of the scan data (p < .05). The average deviation of trueness according to the intraoral scanner type increased in the following order: BC > PS > OC. The average deviation in precision increased in the following order: PS>OC>BC (p < .05).ConclusionThe restorative materials of the adjacent tooth and the type of intraoral scanner affect the accuracy of the intraoral digital impression. The trueness of the digital images of the BC group, obtained by spraying the powder, was comparable to that of the PS group. Among the adjacent restorative materials, zirconia exhibited the lowest trueness. In contrast, PS demonstrated the highest precision among the intraoral scanners, while resin displayed the lowest precision among the adjacent restorative materials.

Factors influencing the reliability of measurements in eyes with full-thickness macular holes: are we measuring incorrectly?

PurposeThe calliper function is used for manual measurements of full thickness macular holes (FTMHs). We aimed to investigate whether a reproducible difference could be detected beyond interobserver variability between two...

Influence of apical finish line location of tooth preparations on the scanning accuracy of intraoral scanners with various focal lengths and scanning technologies

Statement of problemLimited studies have reported the influence of finish line location on the accuracy of intraoral scanners (IOSs). Focal length is a hardware characteristic of IOSs. Whether there is a relationship between scanning accuracy of tooth preparations with the finish located at different apical positions and focal length and IOS technology or system remains uncertain. PurposeThe purpose of the present in vitro study was to assess the influence of the apical finish line location of tooth preparations on the accuracy of 4 IOSs with various focal lengths and scanning technologies. Material and methodsA maxillary typodont with a crown preparation on the left first molar was digitized (T710). Afterwards, a removable die was created on the prepared first molar of the virtual cast and duplicated to create 4 dies with different apical finish line locations: 2- or 1-mm supragingival, 0-mm or equigingival, and −0.5-mm or intracrevicular. The cast and die designs were additively fabricated (Asiga Pro 4K with Keystone Model Ultra). Each die was independently scanned by using the same laboratory scanner (reference scans). Four groups were created: TRIOS 5, i700, iTero, and Primescan. Four subgroups were developed depending on the apical position of the finish line (n=15). In each subgroup, the cast was assembled by positioning the corresponding die into the cast. The cast was then scanned by using the corresponding IOS. The reference scans were used as a control to compute the root mean square (RMS) error discrepancies with each experimental scan on the preparation and margin of the preparation areas. Two-way ANOVA and pairwise comparisons were used to analyze trueness (α=.05). The Levene and pairwise comparisons using the Wilcoxon Rank sum test were used to analyze precision (α=.05). ResultsTrueness discrepancies in the preparation area were found among the groups (P=.010) and subgroups (P<.001), with a significant interaction between group×subgroup (P<.001). The −0.5 mm location obtained significantly worse trueness in the preparation area. The TRIOS 5 and i700 obtained the best trueness in the preparation area. Trueness discrepancies in the margin area were found among the groups (P=.002) and subgroups (P<.001), with a significant interaction between group×subgroup (P=.004). The −0.5 mm location obtained the worst trueness in the margin area. The i700 and Primescan obtained the best trueness in the margin area. Precision discrepancies were found in the preparation area (P<.001). The TRIOS 5 obtained the best precision in the preparation area (P=.001). Precision discrepancies in the margin area were obtained (P<.001). The 1-mm subgroup obtained the best precision (P=.001). ConclusionsThe apical position of the finish line of the tooth preparation tested affected the trueness and precision of the IOSs tested.

The impact of mandibular partial edentulous distal extension on virtual occlusal record accuracy when using two different intraoral scanners: An in vitro analysis

ObjectivesThis in vitro study was formulated to clarify how mandibular partial edentulous distal extension involving three missing teeth affects the virtual occlusal record (VOR) accuracy, in terms of both trueness and precision, when using two different intraoral scanners (IOSs) – the Primescan (PS) and Trios 4 (TR) scanners. MethodsA typodont model missing the left mandibular second premolar, first molar, and second molar as well as the right mandibular first molar was mounted on a semi-adjustable articulator. Four implants were placed at the sites of the missing mandibular teeth. Six pairs of stainless steel markers (diameter: 0.5 mm) were affixed to the maxillary and mandibular casts in the buccal gingiva adjacent to the implants and on the facial surfaces of teeth as reference positions for measurements. The model was digitized with an inEox X5 laboratory scanner to create a reference dataset. Intraoral scans were performed with the PS and TR scanners, with each scan duplicated 10 times to generate 20 paired IOS files. Automatic VOR generation followed the bilateral buccal scan protocol, divided into PS and TR groups (n = 10). Six subgroups of linear distances between interarch markers were assessed with Geomagic Control software, comparing deviations from the reference scan. Data normality was confirmed with the Shapiro-Wilk test. Trueness was evaluated with two-way ANOVAs and pairwise comparisons performed with Tukey's test, whereas precision was assessed with the Levene test (α=0.05). ResultsThe mean linear deviation (Δd) and standard deviation (SD) of VOR were both significantly affected by marker position (P < 0.001), and a significant position × scanner interaction was detected (P < 0.001). Negative mean deviations were observed for the distally extended edentulous areas in both groups. PS scans exhibited trueness that was significantly better than that for TR scans in the D16–46, D13–43, D23–33, and D27–37 subgroups (P < 0.05), whereas there were no significant differences in the D25–35 or D26–36 subgroups. PS scanning was associated with significantly better precision than TR scanning (P < 0.001), and worse precision was observed at D27–37 for both tested IOSs. ConclusionsMandibular partial edentulous distal extension can significantly affect VOR accuracy. The type of IOS could also affect VOR accuracy depending on the area being scanned, with better overall performance observed for the Primescan device as compared to the Trios 4 scanner. Both of these IOSs tended to underestimate VOR occlusal dimensions in mandibular distally extended edentulous areas. Clinical SignificanceMandibular distal edentulous areas can contribute to occlusal dimensions that are underestimated in digital workflows, which may result in infraocclusal discrepancies that arise when performing restorations. IOSs and VOR scanning protocols should thus be carefully considered in order to minimize these risks.

Automated extrinsic calibration of solid-state frame LiDAR sensors with non-overlapping field of view for monitoring indoor stockpile storage facilities

Several industrial and commercial bulk material management applications rely on accurate, current stockpile volume estimation. Proximal imaging and LiDAR sensing modalities can be used to derive stockpile volume estimates in outdoor and indoor storage facilities. Among available imaging and LiDAR sensing modalities, the latter is more advantageous for indoor storage facilities due to its ability to capture scans under poor lighting conditions. Evaluating volumes from such sensing modalities requires the pose (i.e., position and orientation) parameters of the used sensors relative to a common reference frame. For outdoor facilities, a Global Navigation Satellite System (GNSS) combined with an Inertial Navigation System (INS) can be used to derive the sensors’ pose relative to a global reference frame. For indoor facilities, GNSS signal outages will not allow for such capability. Prior research has developed strategies for establishing the sensor position and orientation for stockpile volume estimation while relying on multi-beam spinning LiDAR units. These approaches are feasible due to the large range and Field of View (FOV) of such systems that can capture the internal surfaces of indoor storage facilities.The mechanical movement of multi-beam spinning LiDAR units together with the harsh conditions within indoor facilities (e.g., excessive humidity, wide range of temperature variation, dust, and corrosive environment in deicing salt storage facilities) limit the use of such systems. With the increasing availability of solid-state LiDAR units, there is an interest in exploring their potential for stockpile volume estimation. Despite their higher robustness to harsh conditions, solid-state LiDAR units have shorter distance measurement range and limited FOV when compared with multi-beam spinning LiDAR. This research presents a strategy for the extrinsic calibration (i.e., estimating the relative pose parameters) of installed solid-state LiDAR units inside stockpile storage facilities. The extrinsic calibration is made possible using deployed spherical targets and a complete, reference scan of the facility from another LiDAR sensing modality. The proposed research introduces strategies for: 1) automated extraction of the spherical targets; 2) automated matching of these targets in the solid-state LiDAR and reference scans using invariant relationships among them; and 3) coarse-to-fine estimation of the calibration parameters. Experimental results in several facilities have shown the feasibility of using the proposed methodology to conduct the extrinsic calibration and volume evaluation with an error percentage less than 3.5% even with occlusion percentages reaching up to 50%.

Complete-arch accuracy of seven intraoral scanners measured by the virtual-fit method

ObjectivesThis study compared the accuracy of seven intraoral scanners (IOS) by the virtual-fit method. MethodsFour maxillary arches with tooth abutments were scanned with an industrial reference scanner (n=1) and by Aoralscan3, EmeraldS, Helios600, Lumina, Mediti700, Primescan, and Trios5 IOSs (each n=12). Two complete-arch fixed frameworks were designed on each IOS scan with a 70 µm (group 70) and a 90 µm internal cement space (group 70+20, additional 20 µm at the margin). The virtual-fit method was comprised of superimposing the framework designs onto the reference scan using a non-penetrating algorithm simulating the clinical try-in. Internal and marginal gaps were measured. Precision was estimated by the mean absolute errors (MAE). ResultsIn group 70, Mediti700 (43 µm), Primescan (42 µm), and EmeraldS were in the best homogenous subset for the marginal gap, followed by the Lumina (67 µm), Aoralscan3 (70 µm), and Trios5 (70 µm), whereas Helios600 (118 µm) was in the third subset. Based on the MAE at the margin, Mediti700, Trios5, and EmeraldS were in the first-best homogenous subset, followed by Primescan. Lumina and Helios600 were in the third subset, and Aoralscan3 was in the fourth subset. In group 70+20, the marginal gap was significantly decreased for Lumina and Aoralscan3, whereas MAE significantly decreased for EmeraldS and Aoralscan3. The rank of IOSs was similar for the internal gap. ConclusionEmeraldS, Mediti700, Primescan, and Trios5 meet the marginal and internal fit criteria for fixed tooth-borne complete arch restorations. Increasing the cement space during design could enhance restoration fit. Clinical significanceThe virtual-fit alignment method can effectively evaluate the accuracy of different intraoral scanners, offering valuable clinical guidance for distinguishing among them. Recent software and hardware versions of long-standing IOS manufacturers are suitable for fabricating complete arch restoration.

In vitro evaluation of the impact of intraoral scanner, scanning aids, and the scanned arch on the scan accuracy of edentulous arches.

To assess the accuracy of complete maxillary and mandibular edentulous arch scans obtained using two different intraoral scanners (IOSs), with and without scanning aids, and to compare these results to those obtained using conventional impression methods. Two IOSs were used (TRIOS 4 [TRI] and Emerald S [EMR]) to scan maxillary and mandibular typodonts. The typodonts were scanned without scanning aids [TRI_WSA and EMR_WSA groups] (n = 10). The typodonts were then scanned under four scanning aid conditions (n = 10): composite markers [TRI_MRK and EMR_MRK groups], scanning spray [TRI_SPR and EMR_SPR groups], pressure indicating paste [TRI_PIP and EMR_PIP groups], and liquid-type scanning aid [TRI_LQD and EMR_LQD groups]. Conventional impressions of both arches were also made using irreversible hydrocolloids in stock trays [IHC] and using polyvinyl siloxane (PVS) impression material in custom trays (n = 10) which were digitized using a laboratory scanner. Using a metrology software program, all scans were compared to a reference scan in order to assess trueness and to each other to assess precision. Trueness and precision were expressed as the root mean square (RMS) of the absolute deviation values and the statistical analysis was modeled on a logarithmic scale using fixed-effects models to meet model assumptions (α = 0.05). The main effect of arch (p = 0.004), scanner (p < 0.001), scanning aid (p = 0.041), and the interaction between scanner and scanning aid (p = 0.027) had a significant effect on mean RMS values of trueness. The arch (p = 0.015) and scanner (p < 0.001) had a significant effect on the mean RMS values of precision. The maxillary arch had better accuracy compared to the mandible. The TRIOS 4 scanner had better accuracy than both the Emerald S scanner and conventional impressions. The Emerald S had better precision than conventional impressions. The scanning spray and liquid-type scanning aids produced the best trueness with the TRIOS 4 scanner, while the liquid-type scanning aid and composite markers produced the best trueness for the Emerald S scanner. The scanned arch and the type of scanner had a significant effect on the accuracy of digital scans of completely edentulous arches. The scanning aid had a significant effect on the trueness of digital scans of completely edentulous arches which varied depending on the scanner used.

Effect of preparation design and scan pattern on the accuracy of intraoral scans for complete arch laminate veneers under simulated intraoral variables.

The purpose of the study was to investigate the influence of different preparation designs and scan patterns on the accuracy of intraoral scans for complete-arch maxillary laminate veneers. Three maxillary typodonts were used to obtain reference models with three different laminate veneer preparation designs: windows (W), beveled (B), and incisal overlap (IO). Reference scans were obtained with a desktop scanner. A total of 90 complete arch intraoral scans were made with an intraoral scanner (Medit i700) following three different scan patterns: straight motion (SM), zigzag motion (ZM), and combined motion (CM). Ten scans were made in each subgroup and exported as standard tessellation language (STL) files. Assessment of accuracy was conducted with a 3D software analysis program (Geomagic Control X). Each STL file was individually aligned with the reference scan using the best fit algorithm tool, and 3D differences were calculated using the root mean square (RMS) value. Two-way analysis of variance (ANOVA) followed by post hoc comparison tests were applied to analyze precision and trueness data (α = 0.05). Two-way ANOVA and post hoc comparison tests revealed significant differences among different preparation designs and scan patterns (p < 0.05). Regarding trueness, the IO when scanned with SM presented higher mean RMS than the other preparation designs (W and B) scanned with the same scanning pattern (p < 0.05). Regarding precision, the groups of W and IO presented significantly higher mean RMS than the group of B when scanned with ZM (p < 0.05). Accuracy of intraoral scans for complete-arch laminate veneers was affected by different laminate veneer preparation designs and scan patterns. Modifying scan pattern according to preparation design helps to improve scan accuracy for complete-arch laminate veneers.