Accuracy of Intraoral Digital Impressions for Whole Upper Jaws, Including Full Dentitions and Palatal Soft Tissues

Influence of splinting scan bodies or incorporating three-dimensionally printed scan aids on the trueness of complete arch digital scans

STATEMENT OF PROBLEM

Studies are sparse on how splinting scan bodies or incorporating 3-dimensionally (3D) printed scan aids influence the trueness of complete arch digital scans.

PURPOSE

The purpose of this in vitro study was to compare the trueness of multisite implant recordings obtained using 6 different methods on an edentulous mandible.

MATERIAL AND METHODS

A definitive cast of an edentulous mandible with 4 multi-unit analogs placed at different angles and interanalog distances was extraorally scanned, and the resulting data were saved as a reference file. To obtain experimental files, 6 distinct methods were used: conventional impression with splinted open-tray impression copings (IC), intraoral scanning (IOS) without splinting scan bodies or using any scan aids (SB), IOS with pattern resin-splinted scan bodies (PR), IOS with composite resin-splinted scan bodies (CR), IOS with 3D printed custom scan bodies (CSB), and IOS with 3D printed auxiliary apparatus (AA). The experimental files were aligned to the reference file in a metrology software program. The 3D comparison algorithm was run to quantify the root mean square estimate error (RMS). Scan bodies in the files were converted to hollow virtual cylinders, and the Cartesian coordinates of the lines passing through the centers of these cylinders were recorded to analyze angular (AD) and linear distortion (LD). LD was further analyzed along the x (∆X), y (∆Y), and z axes (∆Z). One-way ANOVAs with the Tukey HSD test were used for statistical analysis (α=.05).

RESULTS

AD at all sites, LD at all sites, and the RMS error showed significant differences (P<.05). The IC group showed the lowest AD values across all sites, followed by the AA, CSB, PR, CR, and SB groups. The SB group had the greatest LD values at all sites, while the IC group indicated the lowest LD values at all sites except the left anterior site. In terms of 3D distortions, the SB group had the largest RMS value, whereas the IC group showed the lowest RMS value. ∆X, ∆Y, and ∆Z values also showed significant differences at all sites (P<.001) except for the ∆Z values at the right anterior site (P=.194). The highest mean ∆X, ∆Y, and ∆Z values were recorded in the SB group except for the ∆Z measurement of the left posterior site.

CONCLUSIONS

The IC group outperformed the other groups. The AA group exhibited distortion comparable with that of the IC group. Splinting scan bodies or using scan aids enhanced the trueness.

Intraoral ultrasonography image registration for evaluation of partial edentulous ridge: A methodology and validation study

OBJECTIVES

Ultrasound (US) reveals details for diagnosing soft- and hard-tissue dimensions around teeth, implants, and the edentulous ridge, not seen in 2D radiographs. Co-registering free-hand US scans with other 3D modalities presents reliability challenges. This study first aims to develop and validate a registration method to longitudinally reproduce US images of the jawbone on a simulator. In addition, it also evaluates the degree of the anatomical match in humans between US images acquired by the proposed registration method and the commonly used freehand acquisitions in comparison to cone beam computed tomography (CBCT) and intra-oral optical scan (IOS), used as references.

METHODS

A previously introduced ultrasound phantom was employed as a CBCT-US hybrid, suitable for training and technique development of US guides in edentulous ridges. After establishing feasibility in the phantom, the methodology was validated in a cohort of 24 human subjects (26 cases). Soft tissues were delineated on US and IOS, and hard tissues on US and CBCT. US accuracy and repeatability from both guided and freehand scans (non-guided) was assessed as the average distance between US and the references.

RESULTS

Guided US images resembled the references more closely than freehand (non-guided) scans. Notably, delineation of soft and hard tissues was significantly more accurate when employing guides. In the phantom, guided scans exhibited an absolute mean deviation of 81.8 µm for gingiva and 90.4 µm for bone, whereas non-guided scans showed deviations of 150.4 µm and 177.2 µm, respectively. Similarly, in vivo, guided US outperformed non-guided US, with gingiva deviations of 125 µm and 196 µm, and bone deviations of 354 µm and 554 µm, respectively.

CONCLUSIONS

By using a registration method, guided US scans improved repeatability and accuracy of mapping hard and soft tissue of the edentulous ridge when compared to non-guided scans.

CLINICAL RELEVANCE

This guided US imaging method could lay the foundation for longitudinal evaluation of tissue behavior and dimensional changes with improved accuracy.

Utilizing an additively manufactured Kois deprogrammer to record centric relation: A simplified workflow and delivery technique

A technique for fabricating an additively manufactured Kois deprogrammer is described from the initial patient data collection with an intraoral scanner to the 3D printing methods to fabricate the device. The incorporation of digital technologies for manufacturing a Kois deprogrammer provides new clinical and manufacturing tools, providing more efficient and less time-consuming design and manufacturing techniques than conventional techniques while maintaining conventional prosthodontic concepts.

Impact of the superimposition reference area on intraoral scanning accuracy in a partially dentate maxilla

STATEMENT OF PROBLEM

The alignment of 3-dimensional (3D) files involves selecting a reference area before performing a local best fit alignment during the digital scan superimposition and is essential for comparing digital scans. Scan alignment relies on both reference area location and the alignment algorithm. However, a consensus on the impact of different reference areas on intraoral scanning accuracy is lacking.

PURPOSE

The purpose of this in vitro study was to assess the impact of 3 superimposition reference areas on the accuracy of 3 intraoral scanners for a partially dentate maxilla.

MATERIAL AND METHODS

A Kennedy class II resin cast was scanned using 3 intraoral scanners (Primescan, TRIOS 3, and Emerald) outputting 30 digital scans (10 per scanner). Test scans from intraoral scanners were subsequently compared with a reference digital standard tessellation language file generated by a laboratory scanner with validated accuracy. The files were superimposed using best fit alignment for each intraoral scanner using 3 different superimposition reference areas (whole region of interest, palate, and all teeth). Accuracy was assessed by using a 3D analysis program (Geomagic Control X; 3D systems) for each scanner at 4 preselected areas. Test and reference scan differences were depicted on color maps and quantified via root mean square deviations. Differences were analyzed using regression analysis with the post hoc student t test and Bonferroni correction (α=.05).

RESULTS

The TRIOS 3 and Emerald produced positive deviations in the palatal color maps, whereas Primescan produced more uniform color maps, regardless of the superimposition strategy used. Primescan exhibited the best accuracy (trueness and precision) in both palatal and bounded edentulous areas, regardless of the superimposition reference area. The TRIOS 3 recorded the highest distal extension trueness (ranging from 42.9±7.7 µm to 65 ±19.5 µm), and Primescan achieved the highest precision (ranging from 28.5 ±9.8 µm to 48.9 ±16.9 µm), regardless of the superimposition area. Emerald demonstrated the highest teeth trueness (ranging from 31.6 ±6.8 µm to 69.6 ±11.5 µm), while Primescan produced the highest precision (ranging from 17.9 ±6.1 µm to 30.7 ±9.2 µm), regardless of the reference area used.

CONCLUSIONS

The chosen reference area for best fit alignment significantly influenced digital scan accuracy (P<.001). Primescan displayed the highest palatal and bounded edentulous area accuracy, with TRIOS 3 recording the highest distal extension trueness. Emerald recorded the highest teeth trueness and Primescan recorded the highest distal extension and tooth precision. All conclusions were independent of the superimposition strategy used.

A fully digital workflow for the design and manufacture of a class of metal orthodontic appliances

Background

Traditional working procedures requires a lot of clinical processes and processing time.

Methods

The orthodontic metal appliances were made by applying oral scanners, digital images, computer-aided design and computer-aided manufacturing (CAD-CAM) printers.

Results

The computer digital technology simplified the manufacturing process for dental appliances and shorten the duration for clinical operation and technical processing.

Conclusions

The technique described in this paper can guarantee the accuracy of orthodontic appliances and bring revolution the field.

Clinical significance

The CAD-CAM technology provides a fully digital workflow for manufacturing metal orthodontic appliances, which saves a considerable amount of labor and material costs, and significantly reduces heavy metal pollution in the working environment of dental technicians.

Influence of scan extension and starting quadrant on the accuracy of four intraoral scanners for fabricating tooth-supported crowns

STATEMENT OF PROBLEM

Multiple factors can influence the accuracy of intraoral scanners (IOSs). However, the impact of scan extension and starting quadrant on the accuracy of IOSs for fabricating tooth-supported crowns remains uncertain.

PURPOSE

The purpose of the present in vitro study was to measure the influence of scan extension (half or complete arch scan) and the starting quadrant (same quadrant or contralateral quadrant of the location of the crown preparation) on the accuracy of four IOSs.

MATERIAL AND METHODS

A typodont with a crown preparation on the left first molar was digitized (T710) to obtain a reference scan. Four scanner groups were created: TRIOS 5, PrimeScan, i700, and iTero. Then, 3 subgroups were defined based on the scan extension and starting quadrant: half arch (HA subgroup), complete arch scan starting on the left quadrant (CA-same subgroup), and complete arch scan starting on the right quadrant (CA-contralateral subgroup), (n=15). The reference scan was used as a control to measure the root mean square (RMS) error discrepancies with each experimental scan on the tooth preparation, margin of the tooth preparation, and adjacent tooth areas. Two-way ANOVA and pairwise multiple comparisons were used to analyze trueness (α=.05). The Levene and pairwise comparisons using the Wilcoxon Rank sum tests were used to analyze precision (α=.05).

RESULTS

For the tooth preparation analysis, significant trueness and precision differences were found among the groups (P<.001) and subgroups (P<.001), with a significant interaction group×subgroup (P=.002). The iTero and TRIOS5 groups obtained better trueness than the PrimeScan and i700 groups (P<.001). Moreover, half arch scans obtained the best trueness, while the CA-contralateral scans obtained the worst trueness (P<.001). The iTero group showed the worst precision among the IOSs tested. For the margin of the tooth preparation evaluation, significant trueness and precision differences were found among the groups (P<.001) and subgroups (P<.001), with a significant interaction group×subgroup (P=.005). The iTero group obtained best trueness (P<.001), but the worst precision (P<.001) among the IOSs tested. Half arch scans obtained the best trueness and precision values. For the adjacent tooth analysis, trueness and precision differences were found among the groups (P<.001) and subgroups tested (P<.001), with a significant interaction group×subgroup (P=.005). The TRIOS 5 obtained the best trueness and precision. Half arch scans obtained the best accuracy.

CONCLUSIONS

Scan extension and the starting quadrant impacted the scanning trueness and precision of the IOSs tested. Additionally, the IOSs showed varying scanning discrepancies depending on the scanning area assessed. Half arch scans presented the highest trueness and precision, and the complete arch scans in which the scan started in the contralateral quadrant of where the crown preparation was obtained the worst trueness and precision.

Utilizing additively manufactured custom devices to record mandibular motion by using optical jaw tracking systems: A dental technique

A technique is described for fabricating additively manufactured custom holder devices to assist optical jaw tracking systems. Most jaw tracking systems provide standardized holders attached to the trackers. The technique described aims to provide a more efficient custom holder design that improves marker retention and mandibular motion recording, decreases the incidence of the procedure complications such as tracker decementation or displacement, and increases the efficiency of the intervention by reducing the positioning time of the trackers in the patient's mouth during the clinical appointment.

Influence of connected and nonconnected calibrated frameworks on the accuracy of complete arch implant scans obtained by using four intraoral scanners, a desktop scanner, and a photogrammetry system

STATEMENT OF PROBLEM

Different techniques have been proposed for increasing the accuracy of complete arch implant scans obtained by using intraoral scanners (IOSs), including a calibrated metal framework (IOSFix); however, its accuracy remains uncertain.

PURPOSE

The purpose of this in vitro study was to compare the accuracy of complete arch scans obtained with connecting and non-connecting the implant scan bodies (ISBs) recorded using intraoral scanners (IOSs), a laboratory scanner (LBS), and photogrammetry (PG).

MATERIAL AND METHODS

A cast with 6 implant abutment analogs was obtained. Six groups were created: TRIOS 4, i700, iTero, CS3800, LBS, and PG groups. The IOSs and LBS groups were divided into 3 subgroups: nonconnected ISBs (ISB), splinted ISBs (SSB), and calibrated framework (CF), (n=15). For the ISB subgroups, an ISB was positioned on each implant abutment analog. For the SSB subgroups, a printed framework was used to connect the ISBs. For the CF subgroups, a calibrated framework (IOSFix) was used to connect the ISBs. For the PG group, scans were captured using a PG (PIC Camera). Implant positions of the reference cast were measured using a coordinate measurement machine, and Euclidean distances were used as a reference to calculate the discrepancies using the same distances obtained on each experimental scan. Wilcoxon squares 2-way ANOVA and pairwise multiple comparisons were used to analyze trueness (α=.05). The Levene test was used to analyze precision (α=.05).

RESULTS

Linear and angular discrepancies were found among the groups (P<.001) and subgroups (P<.001). Linear (P=.008) and angular (P<.001) precision differences were found among the subgroups.

CONCLUSIONS

The digitizing method and technique impacted the trueness and precision of the implant scans. The photogrammetry and calibrated framework groups obtained the best accuracy. Except for TRIOS 4, the calibrated framework method improved the accuracy of the scans obtained by using the IOSs tested.

Virtual tumor mapping and margin control with 3-D planning and navigation

Computer technology-based treatment approaches like intraoperative navigation and intensity-modulated radiation therapy have become important components of state of the art head and neck cancer treatment. Multidirectional exchange of virtual three-dimensional patient data via an interdisciplinary platform allows all medical specialists involved in the patients treatment to take full advantage of these technologies. This review article gives an overview of current technologies and future directions regarding treatment approaches that are based on a virtual, three-dimensional patient specific dataset: storage and exchange of spatial information acquired via intraoperative navigation allow for a highly precise frozen section procedure. In the postoperative setting, virtual reconstruction of the tumor resection surface provides the basis for improved radiation therapy planning and virtual reconstruction of the tumor with integration of molecular findings creates a valuable tool for postoperative treatment and follow-up. These refinements of established treatment components and novel approaches have the potential to make a major contribution to improving the outcome in head and neck cancer patients.

A Systematic Review of the Use of Intraoral Scanning for Human Identification Based on Palatal Morphology

A common application for intraoral scanners is the digitization of the morphology of teeth and palatal rugae. Palatal scans are most commonly required to fabricate complete dentures and immediate transitional dentures and serve as a reference point for assessing orthodontic results. However, they are also frequently included by accident, even though the main purpose of intraoral scanning is to reconstruct dentition using computer-aided manufacturing (CAM). The literature shows that the identification of disaster victims has frequently involved palatal rugae impressions. As the skull provides sound insulation, the rugae are resistant to heat, chemicals, and stress. Antemortem data might be difficult to find during a forensic inquiry, particularly in disaster victim identification cases. In contrast with DNA and fingerprints, there is a greater likelihood of having a dental record that contains palatal scans. With specialized software, the scans can be exported as open stereolithography (STL) files. Considering that a full case consumes up to about 100 MB of hard drive space, long-term storage should not be an issue compared to a plaster model. Additionally, dentists widely use online databases to exchange data for smile design, implant registration, and orthodontic purposes. This will produce a digital database that grows quickly and is readily usable for forensic investigations. The uniqueness of forensic features is frequently challenged; however, palatal morphology's unique trait could make it possible as it is characteristic of individuals as well as the most distinguishing factor. This review will highlight how rugae, palatal morphology, mirroring, superimposition, and geometrics can serve in forensic identification.

Effect of various surface treatments on relining bond strength of CAD-CAM denture base materials

PURPOSE

The aim of this study was to analyze the impact of various surface treatments and production methods on the shear bond strength (SBS) between reline material and denture base resins.

MATERIALS AND METHODS

One-hundred-twenty specimens were produced using conventional heat-polymerization, subtractive, and additive techniques. Each group consisted of 40 specimens. The specimens were divided into four subgroups, each with 10 samples, for surface treatments. These subgroups were: (1) Control-only monomer application, (2) 50 μm airborne-particle abrasion, (3) 110 μm airborne-particle abrasion, and (4) Roughening with tungsten carbide bur. Representative specimens from each subgroup were examined under SEM. Then, auto-polymerized resin was condensed in the center of the specimens. Specimens were subjected to thermal aging (5000 cycles at 5-55°C). The SBS test was conducted and failure loads were recorded. The data were evaluated by two-way ANOVA and Tukey pairwise multiple comparisons method (p < 0.05).

RESULTS

The additively produced group showed significantly lower SBS than conventional and subtractive groups (p < 0.001), with no significant differences between the subtractive and conventional groups. Specimens that underwent monomer application only showed the lowest SBS among surface treatments, while 50 μm airborne-particle abrasion showed the highest SBS. Based on the partial eta-squared analysis results, the surface treatment mainly impacted SBS.

CONCLUSIONS

Among the surface treatment methods, treating denture bases with 50 μm airborne-particle abrasion is more effective for maintaining adhesion, especially in the additive technique.

Accuracy of intraoral scanners in different complete arch scan patterns

STATEMENT OF PROBLEM

The accuracy (trueness and precision) of intraoral scanners and complete arch scans remains controversial.

PURPOSE

The purpose of this in vitro study was to compare the trueness and precision of 3 intraoral scanners with various scan patterns.

MATERIAL AND METHODS

Four standard metal spheres were installed on a dental maxillary cast according to American National Standard/American Dental Association (ANSI/ADA) specification no. 132. Six distances among the center of spheres were measured with a coordinate measuring machine and used as references. Four different scanning patterns were assigned: zigzag, occlusal-palatal-buccal, occlusal-buccal-palatal, and molar-to-canine. Dental Wings and TRIOS 3 applied to the first 3 scan patterns, while True Definition applied to all patterns (n=30). Six distances in the scan files were also measured and calculated for relative errors of trueness and precision. A ratio less than 0.0025 was considered acceptable and used for binary outcome analysis. Differences among scanners and scan patterns in terms of trueness and precision were analyzed with the chi-squared test, Fisher exact test, and logistic regression (α=.05).

RESULTS

The zigzag scan pattern from TRIOS 3 and the occlusal-buccal-palatal pattern from True Definition exhibited 100% acceptable precision. TRIOS 3 revealed the highest number of acceptable trueness values in the occlusal-palatal-buccal scan (88.3%). The scan patterns from Dental Wings and TRIOS 3 were related to the trueness. TRIOS 3 and True Definition were 12.8 and 6.4 times more likely to obtain acceptable trueness than Dental Wings (P<.001). The zigzag scan pattern had the highest chance of obtaining acceptable trueness.

CONCLUSIONS

The scan patterns influenced the trueness and precision of the intraoral scanners in different ways. For the best trueness, TRIOS 3 should be applied with an occlusal-palatal-buccal scan pattern, Dental Wings should be applied with a zigzag scan pattern, while True Definition can be used with any scan pattern.

Intraoral digital implant scans: Parameters to improve accuracy

PURPOSE

To report the means to maximize the predictability and accuracy of intraoral digital implant scans through the evaluation of operator and patient-related factors.

MATERIALS AND METHODS

A search of published articles related to factors that can decrease the scanning accuracy of intraoral digital implant scans was completed in four data sources:MEDLINE, EMBASE, EBSCO, and Web of Science. All studies related to variables that can influence the accuracy of intraoral digital implant scans obtained by using intraoral scanners (IOSs) were considered. These variables included ambient lighting, scanning pattern, implant scan body (ISB) design, techniques for splinting ISBs, arch location, implant position, and inter-implant distance.

RESULTS

Among operator-related factors, ambient lighting conditions, scanning pattern, and ISB design (material, geometry, and retention design) can impact the accuracy of intraoral digital implant scans. The optimal ISB for maximizing IOS accuracy is unclear; however, polymer ISB can wear with multiple reuse and sterilization methods. Among patient-related factors, additional variables should be considered, namely arch (maxillary vs. mandibular arch), implant position in the arch, inter-implant distance, implant depth, and angulation.

CONCLUSIONS

Ambient lighting conditions should be established based on the IOS selected to optimize the accuracy of intraoral digital implant scans. The optimal scanning pattern may vary based on the IOS, clinical situation, and the number of implants. The optimal ISB design may vary depending on the IOS used. Metallic implant scan bodies are preferred over polymer ISB designs to minimize wear due to multiple use and sterilization distortion. Among patient-related factors, additional variables should be considered namely the arch scanned, implant position in the arch, inter-implant distance, implant depth, and angulation. The impact of these factors may vary depending on the IOS selected.

Trueness and precision of complete arch dentate digital models produced by intraoral and desktop scanners: An ex-vivo study

OBJECTIVES

The study aimed to compare the trueness and precision of five intraoral scanners (Emerald S, iTero Element 5D, Medit i700, Primescan, and Trios 4) and two indirect digitization techniques for both teeth and soft tissues on fresh mandibular and maxillary cadaver jaws.

METHODS

The maxilla and mandible of a fully dentate cadaver were scanned by the ATOS industrial scanner to create a master model. Then, the specimens were scanned eight times by each intraoral scanner (IOS). In addition, 8 polyvinylsiloxane (PVS) impressions were made and digitized with a Medit T710 desktop scanner. Stone models were then poured and again scanned with the desktop scanner. All IOS, PVS, and stone models were compared to the master model to calculate the mean absolute surface deviation for mandibular teeth, maxillary teeth, and palate.

RESULTS

For mandibular teeth, the PVS trueness was only significantly better than the Medit i700 (p < 0.001) and Primescan (p < 0.05). In maxillary teeth, the PVS trueness was significantly better than all IOSs (p < 0.05-0.001); the stone trueness was significantly better than Emerald S (p < 0.01), Medit i700 (p < 0.001) and Primescan (p < 0.01). In the palate, PVS and stone trueness were significantly lower than the iTero Element 5D (p < 0.01) and Trios 4 (p < p < 0.01). Stone trueness was significantly lower than the Medit i700 (p < 0.05). The precision in the palate was significantly lower for PVS and stone than for Emerald S (p < 0.01, p < 0.05), iTero Element 5D (p < 0.01, p < 0.01), Primescan (p < 0.001, p < 0.001), and Trios 4 (p < 0.001, p < 0.01). Significant differences in trueness between the IOSs were observed only in the mandibular teeth. The Medit i700 performed worse than Emerald S (p < 0.01) and iTero Element 5D (p < 0.01). For mandibular teeth, the Medit i700 was significantly more precise than Primescan (p < 0.01) and the Emerald S (p < 0.05). The Trios 4 was significantly less precise than Emerald S (p < 0.05). The precision of Medit i700 was significantly worse than iTero Element 5D (p < 0.01) for maxillary teeth, as well as the Primescan (p < 0.01) and Trios 4 (p < 0.05) for the palate.

CONCLUSIONS

In general, indirectly digitized models from PVS impressions had higher trueness than IOS for maxillary teeth; precision between the two methods was similar. IOS was more accurate for palatal tissues. The differences in trueness and precision for mandibular teeth between the various techniques were negligible.

CLINICAL SIGNIFICANCE

All investigated IOSs and indirect digitization could be used for complete arch scanning in mandibular and maxillary dentate arches. However, direct optical digitization is preferable for the palate due to the low accuracy of physical impression techniques for soft tissues.

Influence of interdental spaces and the palate on the accuracy of maxillary scans acquired using different intraoral scanners

PURPOSE

To assess the influence of interdental spaces and scanning the palate on the accuracy of maxillary scans acquired using three intraoral scanners (IOSs).

MATERIALS AND METHODS

A virtual completely dentate maxillary cast without interdental spaces was obtained and modified to create 1, 2, and 3 mm of interdental spacing between the anterior teeth. These three files (reference standard tessellation language files) were used to print three reference casts. The reference casts were scanned using three IOSs: TRIOS4, iTero Element 5D, and Aoralscan2. Three groups were created based on the interdental spaces: 0, 1, 2, and 3 mm (n = 10). The groups were subdivided into two subgroups: no palate (NP subgroup) and palate (P subgroup). The reference STL files were used to measure the discrepancy with the experimental scans by calculating the root mean square (RMS) error. Three-way analysis of variance (ANOVA) and post hoc Tukey pairwise comparison tests were used to analyze trueness. The Levene test was used to analyze precision (α = 0.05).

RESULTS

Trueness ranged from 91 to 139 μm and precision ranged from 5 to 23 μm among the subgroups tested. A significant correlation was found between IOS*group (p<0.001) and IOS*subgroup ( p<0.001). Tukey test showed significant trueness differences among the interdental spaces tested (p<0.001). The 1- and 2-mm groups obtained better trueness than the 0- and 3-mm groups (p<0.001). An 11 μm mean trueness discrepancy was measured among the different interdental space groups tested. The P subgroups demonstrated significantly higher trueness when compared to the NP subgroups (p<0.001). The discrepancy between the maxillary scans with and without the palate was 4 μm. Significant precision discrepancies were found (p = 0.008), with the iTero group showing the lowest precision.

CONCLUSION

Interdental spaces and incorporation of the palate on maxillary intraoral scans influenced trueness and precision of the three IOSs tested. However, the scanning discrepancy measured may be of no clinical relevance.

Effect of scanning strategies on the accuracy of digital intraoral scanners: a meta-analysis of in vitro studies

PURPOSE

This study aimed to investigate whether the accuracy of intraoral scanners is influenced by different scanning strategies in an in vitro setting, through a systematic review and meta-analysis.

MATERIALS AND METHODS

This review was conducted in accordance with the PRISMA 2020 standard. The following PICOS approach was used: population, tooth impressions; intervention, the use of intraoral scanners with scanning strategies different from the manufacturer's instructions; control, the use of intraoral scanners following the manufacturers' requirements; outcome, accuracy of intraoral scanners; type of studies, in vitro. A comprehensive literature search was conducted across various databases including Embase, SciELO, PubMed, Scopus, and Web of Science. The inclusion criteria were based on in vitro studies that reported the accuracy of digital impressions using intraoral scanners. Analysis was performed using Review Manager software (version 5.3.5; Cochrane Collaboration, Copenhagen, Denmark). Global comparisons were made using a standardized mean difference based on random-effect models, with a significance level of α = 0.05.

RESULTS

The meta-analysis included 15 articles. Digital impression accuracy significantly improved under dry conditions (P < 0.001). Moreover, trueness and precision were enhanced when artificial landmarks were used (P ≤ 0.02) and when an S-shaped pattern was followed (P ≤ 0.01). However, the type of light used did not have a significant impact on the accuracy of the digital intraoral scanners (P ≥ 0.16).

CONCLUSION

The accuracy of digital intraoral scanners can be enhanced by employing scanning processes using artificial landmarks and digital impressions under dry conditions.

Accuracy of Intraoral Scanner for Recording Completely Edentulous Arches-A Systematic Review

Scanning edentulous arches during complete denture fabrication is a crucial step; however, the quality of the resulting digital scan is still questionable. The purpose of this study is to systematically review studies (both clinical and in vitro) and determine whether intraoral scanners have clinically acceptable accuracy when recording completely edentulous arches for the fabrication of removable complete dentures. An electronic search in medical databases like PubMed, Scopus, and Web of Science (WOS), using a combination of relevant keywords, retrieved 334 articles. After full-text evaluation, twelve articles fulfilled the inclusion criteria for this review (eight clinical studies and four in vitro studies). A quality analysis of the included studies was carried out using the QUADAS-2 tool. The accuracy values varied between different intraoral scanners. Different regions of the edentulous arches showed differences in trueness and precision values in both in vitro and clinical studies. Peripheral borders, the inner seal, and poorly traceable structures like the soft palate showed maximum discrepancies. The accuracy of intraoral scanners in recording clear anatomic landmarks like hard tissues with attached mucosa was comparable to conventional edentulous arch impressions. However, higher discrepancies were recorded when digitizing mobile and poorly traceable structures. Intraoral scanners can be used to digitize denture-bearing areas, but the interpretation of the peripheral border and the soft palate should be carefully carried out.

Accuracy of intraoral scanning versus conventional impressions for partial edentulous patients with maxillary defects

This study aimed to evaluate the accuracy of digital dental impressions obtained by intraoral scanning (IOS) for partial edentulous patients with maxillary defects by comparing them with conventional impression techniques. Ten subjects underwent an experimental procedure where three ceramic blocks were affixed to the healthy palate mucosa. Digital dental impressions were captured using IOS and subsequently imported into software. Conventional impressions obtained by silicone rubber were also taken and scanned. Linear distance and best-fit algorithm measurements were performed using conventional impression techniques as the reference. Twenty impressions were analyzed, which included 30 pairs of linear distances and 10 best-fit algorithm measurements. Regarding linear distance, paired two-sample t-test demonstrated no significant differences between IOS and model scanning in groups A and C, whereas significant differences were found in group B (P < 0.05). Additionally, ANOVA revealed significant differences among the groups (P < 0.05). No significant differences were found for the best-fit algorithm measurement of the dentition. IOS can provide accurate impressions for partial edentulous patients with maxillary defects and its accuracy was found to be comparable with conventional impression techniques. A functional impression may be needed to ensure accurate reproduction of soft and hard tissues in defect or flap areas.

Comparative Analysis between 3D-Printed Models Designed with Generic and Dental-Specific Software

With the great demand in the market for new dental software, the need has been seen to carry out a precision study for applications in digital dentistry, for which there is no comparative study, and there is a general ignorance regarding their applications. The purpose of this study was to investigate the accuracy differences between digital impressions obtained using generic G-CAD (general CAD) and D-CAD (CAD dental) software. Today, there is a difference between the design software used in dentistry and these in common use. Thus, it is necessary to make a comparison of precision software for specific and generic dental use. We hypothesized that there is no significant difference between the software for specific and general dental use.

METHODS

A typodont was digitized with an intraoral scanner and the models obtained were exported in STL format to four different softwares (Autodesk MeshMixer 3.5, Exocad Dental, Blender for dental, and InLAB). The STL files obtained by each software were materialized using a 3D printer. The printed models were scanned and exported in STL files, with which six pairs of groups were formed. The groups were compared using analysis software (3D Geomagic Control X) by superimposing them in the initial alignment order and using the best fit method.

RESULTS

There were no significant differences between the four analyzed software types; however, group 4, composed of the combination of D-CAD (Blender-InLAB), obtained the highest average (-0.0324 SD = 0.0456), with a higher accuracy compared to the group with the lowest average (group 5, composed of the combination of the Meshmixer and Blender models), a generic software and a specific software (0.1024 SD = 0.0819).

CONCLUSION

Although no evidence of significant difference was found regarding the accuracy of 3D models produced by G-CAD and D-CAD, combinations of groups where specific dental design software was present showed higher accuracy (precision and trueness). The comparison of the 3D graphics obtained with the superimposition of the digital meshes of the printed models performed with the help of the analysis software using the best fit method, replicating the same five reference points for the six groups formed, evidenced a greater tolerance in the groups using D-CAD.

Design of palatal and lingual augmentation prostheses by using an intraoral scanner for a patient after a glossectomy: A clinical report

Computer-aided design and computer-aided manufacturing was used to fabricate palatal and lingual augmentation prostheses for a patient with dysphagia after a glossectomy. The function of these prostheses was comparable with that of those fabricated by conventional methods. The patient outcome suggests that an intraoral scanner can be effectively used for the fabrication of augmentation prostheses for patients with dysphagia and a high risk of aspiration.

Effect of relative humidity on the accuracy, scanning time, and number of photograms of dentate complete arch intraoral digital scans

STATEMENT OF PROBLEM

Intraoral scanners (IOSs) have been used in dentistry for diagnostic and treatment purposes; however, the influence of environmental factors such as humidity or temperature on the accuracy of intraoral scanning is uncertain.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of relative humidity and ambient temperature on the accuracy, scanning time, and number of photograms of dentate complete arch intraoral digital scans.

MATERIAL AND METHODS

A completely dentate mandibular typodont was digitized by using a dental laboratory scanner. Four calibrated spheres were attached following the International Organization for Standardization (ISO) standard 20 896. A watertight box was designed to simulate 4 different relative humidity conditions (50%, 70%, 80%, and 90%) (n = 30). An IOS (TRIOS 3) was used to obtain a total of 120 complete arch digital scans (n = 120). Scanning time and number of photograms of each specimen were recorded. All the scans were exported and compared with the master cast by using a reverse engineering software program. The linear distances among the reference spheres were used to calculate trueness and precision. A unifactorial analysis of variance (ANOVA) and Levene tests followed by the post hoc Bonferroni test were used to analyze trueness and precision data, respectively. A unifactorial ANOVA followed by a post hoc Bonferroni test was also conducted to analyze scanning time and the number of photogram data.

RESULTS

Statistically significant differences were found in trueness, precision, number of photograms, and scanning time (P<.05). Regarding trueness and precision, significant differences were found between the 50% and 70% relative humidity groups and the 80% and 90% relative humidity groups (P<.01). Regarding scanning time and number of photograms, significant differences were obtained among all groups, except between the 80% and 90% relative humidity groups (P<.01).

CONCLUSIONS

The relative humidity conditions tested influenced accuracy, scanning time, and number of photograms in complete arch intraoral digital scans. High relative humidity conditions resulted in the decreased scanning accuracy, longer scanning time, and greater number of photograms of complete arch intraoral digital scans.

A guide for maximizing the accuracy of intraoral digital scans: Part 2-Patient factors

OBJECTIVES

To describe the factors related to patient intraoral conditions that impact the scanning accuracy of intraoral scanners (IOSs). A new classification for these influencing factors is proposed to facilitate dental professionals' decision-making and maximize the accuracy and reliability of intraoral digital scans.

OVERVIEW

Variables related to intraoral conditions of the patient that can influence the scanning accuracy of IOSs include tooth type, presence of interdental spaces, arch width variations, palate characteristics, wetness, existing restorations, characteristics of the surface being digitized, edentulous areas, interimplant distance, position, angulation, and depth of existing implants, and implant scan body selection.

CONCLUSIONS

The knowledge and understanding of the patient's intraoral conditions that can impact the scanning accuracy of IOSs is a fundamental element for maximizing the accuracy of IOSs.

CLINICAL SIGNIFICANCE

The patient's intraoral conditions, or patient factors, can significantly impact intraoral scanning accuracy. Dental professionals must know and understand these influencing patient factors to maximize the accuracy of IOSs.

The discriminative potential of palatal geometric analysis for sex discrimination and human identification

Previous 3D superimposition studies of digital scans of the human palate, using geometric and surface morphology comparisons, have shown its usefulness in assisting in the identification process, including its ability to distinguish identical twins. This study aimed to evaluate the discriminative potential when only simple geometric analysis is used. Its aim is not only to determine if geometric comparison alone is sufficient not only to assist in identification but if it supports the hypothesis of assisting in sex discrimination when no other comparative data is available. The palates of 64 monozygotic (M.Z.T.) and 39 dizygotic (D.Z.T.) twins were digitized three times using a scanner. Digital smoothing was used to remove the rugae, and palatal height, depth, and width were measured. The study confirmed that the smoothing function had little effect on the discriminatory function since the Mean Absolute Distance (MAD) between M.Z.T. (0.430 ± 0.018 mm versus 0.425 ± 0.022 mm p = 0.061) or D.Z.T. (0.621 ± 0.058 mm versus 0.586 ± 0.053 mm, p = 0.284) scans show little change. By combining the height, depth, and width into a discriminative function, the sex correctly correlated 83.9% of the time, identity by 91.2% sensitivity, and twining by 68.5%. The difference in the 3D palatal model between twin siblings is primarily due to palate geometrics. Since geometric comparison requires far less computation time, geometric comparison alone can be used as an adjunct metric for limiting the possible matches in a dental 3D database in determining both sex and identity, especially if no other evidence is available.

A new proposal for improving the accuracy of intraoral scanning for partially edentulous residual ridge

PURPOSE

This study investigated the usefulness of a newly proposed intraoral scanning method, using markers that can be used directly in the oral cavity, in order to improve the accuracy of impression taking of the residual ridge for fabrication of removable partial dentures.

METHODS

An intraoral scanner was used to scan a dental model of a partially edentulous mandibular arch (Kennedy Class I). As markers, pieces of dried pasta were used. The scanning operation was performed under three conditions. In Condition 1, scanning was performed on the remaining teeth and the residual ridge without markers. In Condition 2, scanning of the remaining teeth and residual ridge was performed with markers. In Condition 3, the markers were removed from the model used in Condition 2, and the residual ridge was scanned again. The scanning data of each condition was superimposed on the control data, and the shape error was calculated and compared among the conditions.

RESULTS

There was a significant difference in trueness of the residual ridge before and after marker application. The application of markers improved the trueness, while maintaining precision. Re-scanning after removing the marker did not affect trueness between before and after re-scanning and the re-scanned region showed shape continuity with the surrounding region.

CONCLUSION

The present method using markers that can be used in the oral cavity was effective in improving the accuracy of impression taking at the residual ridge.

Comparison of accuracy between digital and conventional implant impressions: two and three dimensional evaluations

PURPOSE

The present study compared the accuracy between digital and conventional implant impressions.

MATERIALS AND METHODS

The experimental models were divided into six groups depending on the implant location and the scanning span. Digital impressions were captured using the intraoral optical scanner TRIOS (3Shape, Copenhagen, Denmark). Conventional impressions were taken with the monophase impression material based on addition-cured silicones, Honigum-Mono (DMG, Hamburg, Germany). A high-precision laboratory scanner D900 (3Shape, Copenhagen, Denmark) was used to obtain digital data of resin models and stone casts. Surface tessellation language (STL) datasets from scanner were imported into the analysis software Geomagic Qualify 14 (3D Systems, Rock Hill, SC, USA), and scan body deviations were determined through two-dimensional and three-dimensional analyses. Each scan body was measured five times. The Sidak t test was used to analyze the experimental data.

RESULTS

Implant position and scanning distance affected the impression accuracy. For a unilateral arch implant and the mandible models with two implants, no significant difference was observed in the accuracy between the digital and conventional implant impressions on scan bodies; however, the corresponding differences for trans-arch implants and mandible with six implants were extremely significant (P<.001).

CONCLUSION

For short-span scanning, the accuracy of digital and conventional implant impressions did not differ significantly. For long-span scanning, the precision of digital impressions was significantly inferior to that of the traditional impressions.

Dimensional Changes in Extraction Sockets: A Pilot Study Evaluating Differences between Digital and Conventional Impressions

Traditionally, soft tissue records are obtained by dental impression using impression materials; however, accurately recording the soft tissue immediately after tooth extraction is difficult. We measured the tissue changes after tooth extraction and compared two impression modalities (digital versus conventional) by measuring the changes at the soft tissue level. In this case, 15 patients with 17 single extraction sites were enrolled. Conventional impression (CI) using vinyl polysiloxane material and digital impression (DI) using an intraoral scanner were prepared immediately after extraction (T0) and at 2 months post-extraction (T1). Standard tessellation language files were generated for superimposition of the tissue surface. The tissue changes and discrepancies were measured on the superimposed surfaces. The differences in the changes and the discrepancy between the tissue surface impression at each time point were compared. At all measuring levels, the total tissue change was significantly different between groups DI and CI (p < 0.05). DI exhibited a more pronounced tissue surface at both time points, and the total discrepancy was statistically significantly greater at T0 than at T1 (p < 0.05). The values from DI and CI demonstrated small but significantly different for the same study material. The interpretation of such differences may depend on the clinical situation or scientific value.

Digital versus conventional full-arch impressions in linear and 3D accuracy: a systematic review and meta-analysis of in vivo studies

OBJECTIVES

The purpose of this systematic review was to compare the accuracy of digital and conventional full-arch impressions in vivo.

MATERIALS AND METHODS

This systematic review was conducted according to the PRISMA and registered at the PROSPERO (CRD42021232736). Electronic and hand searches were performed to identify in vivo studies comparing the linear or 3D accuracy of digital and conventional impressions. The risk of bias (ROB) of included studies was assessed by QUADAS-2, and the overall quality of evidence was assessed by GRADE.

RESULTS

Twenty-two studies met the inclusion criteria, and 13 studies were included in the meta-analysis. There was no significant difference between digital and conventional impressions in the linear measurements of tooth width, anterior Bolton ratio, overall Bolton ratio, intercanine distance (ICD), and intermolar distance (IMD). The repeated measurement mean errors (RMEs) were less than 0.1 mm, the intra-examiner intraclass correlation coefficient (ICC) values were more than 0.9, and the inter-examiner ICC values were more than 0.87 for both impression techniques. The 3D deviation between digital and alginate impressions was 0.09 mm. The 3D precision of both impression techniques was less than 0.1 mm.

CONCLUSIONS

The trueness of digital and alginate full-arch impressions was similar, and both impression techniques showed high precision. More research was needed to compare digital impressions and other conventional impression materials.

CLINICAL RELEVANCE

For patients with completely natural dentition, the digital impressions obtained directly from intraoral scanning can be considered a viable alternative to alginate impressions.

Digital intraoral scanner devices: a validation study based on common evaluation criteria

Background

The evolution of intraoral scanners (IOSs) is rapid, and new IOSs appear on the market with different properties depending on the manufacturers. There is no uniform rating system based on a defined set of aspects that has reported in the literature that can be used to compare these devices. This validation study aimed to compare different IOSs based on objective and comprehensive parameters.

Methods

In this study, 12 different IOSs were examined. The IOSs that were tested in this study in order of their delivery included the 3Shape Trios 3 Pod®, Planmeca Emerald®, Straumann DWIO®, GC Aadva®, iTero Element 2®, CEREC Primescan®, Medit i500®, 3Shape Trios 4 Move®, Carestream CS3600®, 3Shape Trios 4 Pod®, Carestream CS3700®, and Planmeca Emerald S®. IOSs were evaluated in four different ways: (a)summary chart, (b)comparative assessment, (c)data based on in vitro measurements and (d)accuracy measurements. A scoring system was created to enable an objective rating of IOSs.

Results

The differences among IOSs were demonstrated in point scores (summary chart[max. 10 points] + weight of IOSs[max. 2.5 points] + circumference of IOSs[max. 2.5 points] + in vitro scanning time[max. 2.5 points] + pauses in data capture[max. 2.5 points] + accuracy[max. 10 points] = summary[max. 30 points]). Trios 4 Pod achieved the greatest cumulative score (23.37 points), furthermore it earned the highest points for summary chart and scanning speed. Regarding scanning continuity, the best-performing IOSs, which tied at identical point scores, were the Trios 3 and 4 Pod, Trios 4 Move, iTero Element 2, CS3600 and CS3700. The most accurate IOS was the CEREC Primescan, although it earned the lowest points of the comparative assessment (heaviest IOS). GC Aadva scored 5.73 points of a maximum of 30 points, which was the poorest result in this study.

Conclusion

The scoring system reflects the differences among IOS devices based on the evaluated objective parameters and can be used to help clinicians select the right IOS device. The new generations of IOSs have more special properties, and their accuracy is higher than the previous versions.

Trial registration The permission for this study was granted by University Ethics Committee of Semmelweis University (SE RKEB number:108/2019).

Accuracy of Additively Manufactured Dental Casts Compared with That of Virtual Scan Data Obtained with an Intraoral Scanner: An In Vitro Study

The study aimed to evaluate the time-related accuracy of additively manufactured dental casts and to compare it with scan data obtained with an intraoral scanner in vitro. Twenty-eight markers were attached to a set of dentiforms as reference model, and the distances between the markers were measured using a digital caliper. An intraoral scanner was used to obtain the virtual scan data of the reference model with a total of 30 scans per arch. The distances between markers were measured using a three-dimensional inspection software for all scans (group IOS). Scan data were additively manufactured using a 3D printer, and the distances between markers were measured as in the reference model immediately after post-polymerization (group PPIA), 1 day (group PP1D), 7 days (group PP7D), and 30 days after post-polymerization (group PP30D). The linear deviation in group IOS was 199.74 ± 11.14 μm, PPIA was 242.88 ± 49 μm, PP1D was 259.9 ± 42.59 μm, PP7D was 289.82 ± 39.74 μm, and PP30D was 315.8 ± 33.28 μm, in comparison with the reference model, with significant differences among all groups (all p < 0.05). When additively manufacturing casts from scan data to verify the quality of dental prostheses designed virtually, the prostheses should be adapted to casts manufactured within one week.

In Vivo Complete-Arch Implant Digital Impressions: Comparison of the Precision of Three Optical Impression Systems

(1) Multiple in vitro studies reported insufficient accuracy of intraoral scanners (IOSs) for complete-arch multiple implant impression. The aim of the study is to analyze the precision of three IOSs, PIC dental (Pic dental, Iditec North West SL), TRIOS 3 (3Shape), and True Definition (Midmark Corporation) and the influence of several factors in the edentulous complete maxillary and mandibular arch. (2) A fully edentulous patient with eight implants in the maxillary and in the mandibular jaw was selected. Five impressions were taken per system and arch. A suprastructure was designed on each digital working cast. The precision was analyzed comparing each of the 28 distances and seven relative angulations of the abutments of all the designed suprastructures. The descriptive statistics, the Student's t-test, and the ANOVA test were used to analyze the data (α = 0.05). (3) Significant differences were observed when comparing the IOSs in some of the distances and angulations. (4) The increase in the distance between implants affected the precision of T and TD but not the PIC system. The type of arch did not affect the PIC precision, but the T and TD systems performed worse in the mandibular arch. The system with the best precision was the PIC, followed by TD, and then T.

Effect of the implant-supported provisional restoration on the accuracy of digital peri-implant mucosa replication - a clinical study

OBJECTIVE

This study aimed to quantitatively evaluate the effect of implant-supported provisional restorations (ISPRs) on the accuracy of the intraoral scanned peri-implant soft-tissue profile in the esthetic area.

MATERIALS AND METHODS

Sixteen patients with a single ISPR in the maxillary central incisor's region were recruited for this study. Three impression methods were sequentially used in each patient: (1) an intraoral scanning (IOS) with the ISPR, (2) a conventional impression using the ISPR as impression coping, and (3) a routine IOS without the ISPR. The stereolithography files of the three impression methods obtained from the same patient were superimposed, and the conventional impression method was used as the reference model. Two-dimensional (2D) and three-dimensional (3D) analyses were performed to measure the peri-implant soft-tissue deviation between the reference models and IOS from the groups with or without the ISPR, respectively. Data were presented as the means ± standard deviations. Two-way analyses of variance with post hoc Sidak's multiple comparisons and paired t-tests were performed for 2D and 3D analyses, respectively. The significance level was set at p<0.05.

RESULTS

The peri-implant mucosa without the ISPR immediately collapsed (<20 s), particularly on the palatine side of the labial mucosa and labial side of the palatine mucosa. Consequently, the IOS without the ISPR led to 414.7±116.0 μm of overall dimensional deformation in the cuff-like submucosal region, which was significantly larger (p<0.0001) than that in the IOS with the ISPR (230.6±85.5 μm).

CONCLUSION

ISPRs are important for accurate replication of the intraorally scanned peri-implant soft-tissue profile.

Trueness of full-arch IO scans estimated based on 3D translational and rotational deviations of single teeth-an in vitro study

OBJECTIVES

To three-dimensionally evaluate deviations of full-arch intraoral (IO) scans from reference desktop scans in terms of translations and rotations of individual teeth and different types of (mal)occlusion.

MATERIALS AND METHODS

Three resin model pairs reflecting different tooth (mal)positions were mounted in the phantom head of a dental simulation unit and scanned by three dentists and three non-graduate investigators using a confocal laser IO scanner (Trios 3®). The tooth-crown surfaces of the IO scans and reference scans were superimposed by means of best-fit alignment. A novel method comprising the measurement of individual tooth positions was used to determine the deviations of each tooth in the six degrees of freedom, i.e., in terms of 3D translation and rotation. Deviations between IO and reference scans, among tooth-(mal)position models, and between dentists and non-graduate investigators were analyzed using linear mixed-effects models.

RESULTS

The overall translational deviations of individual teeth on the IO scans were 76, 32, and 58 µm in the lingual, mesial, and intrusive directions, respectively, resulting in a total displacement of 114 µm. Corresponding rotational deviations were 0.58° buccal tipping, 0.04° mesial tipping, and 0.14° distorotation leading to a combined rotation of 0.78°. These deviations were the smallest for the dental arches with anterior crowding, followed by those with spacing and those with good alignment (p < 0.05). Results were independent of the operator's level of education.

CONCLUSIONS

Compared to reference desktop scans, individual teeth on full-arch IO scans showed high trueness with total translational and rotational deviations < 115 µm and < 0.80°, respectively.

CLINICAL RELEVANCE

Available confocal laser IO scanners appear sufficiently accurate for diagnostic and therapeutic orthodontic applications. Results indicate that full-arch IO scanning can be delegated to non-graduate dental staff members.

Accuracy of Master Casts Generated Using Conventional and Digital Impression Modalities: Part 2—The Full Arch Dimension

The aim of this study was to evaluate the accuracy of master casts generated by conventional (putty and light body consistencies polyvinyl siloxane and alginate) and digital impression techniques on a typodont master model with full-arch-prepared abutment teeth. The null hypotheses tested were as follows: (1) no statistically significant differences in accuracy between casts made by the two impression modalities and the typodont master model at each of the four locations (horizontal straight, horizontal curved, horizontal cross arch, and vertical), and (2) no statistically significant differences in dimensions measured at each of the four locations between the casts generated using the conventional and digital impression techniques. For the conventional technique, 10 impressions each were made for the typodont model using polyvinyl siloxane and alginate impression materials, and the casts were poured. For the digital technique, the typodont model was scanned 10 times using a TRIOS-3 3Shape intraoral scanner, and the casts were printed. The measurements for the horizontal (anteroposterior and cross arch) and vertical dimensions were made using a stereomicroscope and the accuracy of fabricated casts was expressed as the percentage of deviation from the typodont master model’s values. A one-way ANOVA and Tukey’s test (p < 0.05) were used to analyze the data. In the current study, the only measurement that did not exceed 0.5% in dimensional change was with the stone casts produced by both the 3M ESPE PVS and Kromopan alginate impression materials at the HAPC dimension. The casts generated by impressions made using the 3M ESPE PVS impression material were the most accurate, whereas the casts generated by making digital impressions using the TRIOS-3 3Shape intraoral scanner were the least accurate among the three tested groups. The greatest number of distortions above 0.5% (at all dimensional locations) was produced by the digital models printed using the ASIGA 3D printer.

Intraoral Scanners in Orthodontics: A Critical Review

Background: The use of digital technology has exponentially increased over recent years. Intraoral scanners, especially, have gained traction within orthodontics. The objective of the present review is to investigate the available evidence to create an up-to-date presentation of various clinical aspects of intraoral scanners in orthodontics. Methods: Search without restrictions in seven databases (Pubmed, CENTRAL, Cochrane Reviews, Scopus, Web of Science, Clinical Trials, Proquest) since inception, and hand searching until October 2020, were conducted. Results: The majority of studies were either cross-over or parallel group studies. The accuracy and reproducibility of intraoral scanners, in comparison to conventional methods, were investigated in several studies, with controversial results. The duration of the procedure did not report any clear outcome in favor of any method. Patients seem to prefer intraoral scanning, even though numerous studies point out the importance of operators’ experience and skills. Conclusions: Despite the innovations that intraoral scanners have brought in orthodontic clinical practice, there are still some challenges and limitations in their use. The majority of existing limitations may be overcome with experience and good clinical skills. More high-quality studies need to be conducted so that clinicians can have a clear image of this new technology.

CT-Based Modeling of the Dentition for Craniomaxillofacial Surgical Planning

ABSTRACT

Historically, the accuracy of imaging teeth by computed tomography (CT) has been suboptimal and deemed inadequate for surgical planning of orthognathic procedures. However, recent advances in CT hardware and software have significantly improved the accuracy of imaging occlusal anatomy. This technical note describes a quantitative means of evaluating the accuracy of CT-based modeling of teeth. Three-dimensional models of the dentition were created from a CT scan obtained of a craniomaxillofacial skeleton. Multiple reconstruction algorithms and modeling parameters were applied. The dentition of the same skeleton was scanned using a handheld optical scanning device to serve as the "gold standard." Semi-automated registrations of CT and optically acquired models were performed and deviation analysis was conducted. On average, the deviation of the CT model with the optical scan measured 0.19 to 0.25 mm across the various reconstruction and modeling parameters, with a mean of 0.22 mm. Computed tomography underestimated contours at cusp tips, while overestimating contours in occlusal groves. The use of bone reconstruction algorithms and decreased model smoothing resulted in more accurate models, though greater surface noise. Future studies evaluating the clinical effectiveness of CT-based occlusal splints should take this finding into account.

Intraoral Digital Scans for Fabricating Tooth-Supported Prostheses Using a Custom Intraoral Scan Body

This article describes a technique to assist with intraoral digital scans for fabricating tooth-supported prostheses by using a custom intraoral scan body when the extension of the scan or the clinical characteristics might compromise the reliability of the intraoral digital scan. A preliminary intraoral scan of the tooth preparations is used to design a custom intraoral scan body which is manufactured using polymethylmethacrylate and a 5-axis milling machine. A low-viscosity polyvinyl siloxane impression of the tooth preparations is obtained using the custom intraoral scan body. Subsequently, the custom intraoral scan body is digitized using an intraoral scanner. A design software program is used to align the digitized custom intraoral scan body with the preliminary intraoral scan to obtain the definitive virtual cast. This technique aims to reduce manual conventional laboratory procedures such as pouring dental impression or die trimming which might minimize inaccuracies on the virtual definitive cast.

Intraoral scanning of neonates and infants with craniofacial disorders: feasibility, scanning duration, and clinical experience

OBJECTIVE

The aim of this study was to evaluate intraoral scanning (IOS) in infants, neonates, and small children with craniofacial anomalies for its feasibility, scanning duration, and success rate. Impression taking in vulnerable patients can be potentially life-threatening, with the risk of airway obstruction and aspiration of impression material. The advantage of increasingly digitalized dentistry is demonstrated.

MATERIALS AND METHODS

IOS was captured with the Trios 3® (3Shape, Copenhagen, Denmark) intraoral scanner. The underlying disorders were divided into cleft lip and palate (CLP), Trisomy 21 (T21), Robin Sequence (RS), Treacher Collins syndrome (TC), and isolated mandibular retrognathia (MR). Scan data were analysed by scanning duration, number of images, possible correlations of these factors with the different craniofacial disorders, patient age, and relationship between first and subsequent scans. Clinical experiences with the repeated digital impressions are described.

RESULTS

Patient data of 141 scans in 83 patients were analysed within an 11-month period. Patients had a median age of 137 days. Median scanning duration was 138 seconds, resulting in a median of 352 images. There was a statistically significant difference in scanning duration (P = 0.001) between infants and neonates. IOS took longest in patients with CLP (537 seconds) and shortest in T21 patients (21 seconds), although there was no statistically significant difference between aetiologies. There was no statistically significant difference between first and subsequent scans in scanning duration. In four cases the IOS had to be repeated, and one patient ultimately required conventional impression taking (all CLP patients; success rate 94%). No severe adverse events occurred.

CONCLUSION

IOS is a fast, safe, and feasible procedure for neonates, small children, and infants with craniofacial malformations. One special challenge for both technician and user was identified in patients with CLP, though implementing this new approach of digital impression taking was otherwise found to be highly successful in everyday clinical routine.

Effect of different arch widths on the accuracy of three intraoral scanners

PURPOSE

The purpose of this study was to compare the accuracy of three intraoral scanner (IOS) systems with three different dental arch widths.

MATERIALS AND METHODS

Three dental models with different intermolar widths (small, medium, and large) were attached to metal bars of different lengths (30, 40, and 50 mm). The bars were measured with a coordinate measuring machine and used as references. Three IOSs were compared: TRIOS 3 (TRI), True Definition (TD), and Dental Wings (DW). The relative length and angular deviation of both ends of the metal bars from the scan data set (n = 15) were calculated and analyzed.

RESULTS

Comparing among scanners in terms of trueness, the relative length deviation of DW in the small (1.28%) and medium (1.08%) arches were significantly higher than TRI (0.46% and 0.48%) and TD (0.33% and 0.18%). The angular deviation of DW in the small (1.75°) and medium (1.83°) arches were also significantly greater than TRI (0.63° and 0.40°) and TD (0.55° and 0.89°). Comparing within scanner, the large arch of DW showed better accuracy than other arch sizes (P < .05). On the other hand, the larger arch of TD presented a greater tendency of angular deviation in terms of trueness. No significant differences were found in terms of trueness between the arch widths of TRI group.

CONCLUSION

The different widths of the dental arches can affect the accuracy of some intraoral scanners in full arch scan.

The Influence of Hard- and Software Improvement of Intraoral Scanners on the Implant Transfer Accuracy from 2012 to 2021: An In Vitro Study

This study aimed to investigate the transfer accuracy (trueness and precision) of three different intraoral scanning families using different hardware and software versions over the last decade from 2012 to 2021, compared to a conventional impression. Therefore, an implant master model with a reference cube was digitized and served as a reference dataset. Digital impressions of all three scanning families (True definition, TRIOS, CEREC) were recorded (n = 10 per group), and conventional implant impressions were taken (n = 10). The conventional models were digitized, and all models (conventional and digital) were measured. Therefore, it was possible to obtain the deviations between the master model and the scans or conventional models in terms of absolute three-dimensional (3D) deviations, deviations in rotation, and angulation. The results for deviations between the older and newer scanning systems were analyzed using pairwise comparisons (p < 0.05; SPSS 26). The absolute 3D deviations increased with increasing scan path length, particularly for the older hardware and software versions (old vs. new (MW ± SD) True Definition: 355 ± 62 µm vs. 483 ± 110 µm; TRIOS: 574 ± 274 µm vs. 258 ± 100 µm; and CEREC: 1356 ± 1023 µm vs. 110 ± 49 µm). This was also true for deviations in rotation and angulation. The conventional impression showed an advantage only regarding the absolute 3D deviation compared to the older systems. Based on the data of the present study, the accuracy of intraoral scanners is decisively related to hardware and software; though, newer systems or software do not necessarily warrant improvement. Nevertheless, to achieve high transfer accuracy, regular updating of digital systems is recommended. The challenge of increasing errors with increasing scan paths is overcome in the most recent systems. The combination of two different scanning principles in a single device seems to be beneficial.

Three-dimensional assessment of virtual bracket removal for orthodontic retainers: A prospective clinical study

INTRODUCTION

Computer-aided design and manufacturing of orthodontic retainers from digitally debonded models can be used to facilitate same-day delivery. The purpose of this prospective clinical study was to validate a novel technique for virtual bracket removal (VBR) in-office, comparing the accuracy with 2 orthodontic laboratories that use VBR for retainer fabrication in the digital workflow.

METHODS

The sample consisted of 40 intraoral scans of 20 patients. Four groups were compared. The scans without brackets were used as a control group. VBR was performed by 3 groups: In-office VBR (Software Meshmixer, version 3.5.474; Autodesk, San Rafael, Calif), Orthodent Laboratory (ODL; Buffalo, NY), and New England Orthodontic Laboratory (NEOLab; Andover, Mass). The virtually debonded models were superimposed onto the control models using surface-based registration. Regional 3-dimensional Euclidean distances between surface points of superimposed models were calculated for comparative analysis of surface changes after VBR using Vector Analysis Module (Canfield Scientific, Fairfield, NJ) software.

RESULTS

The accuracy of VBR using the Meshmixer did not differ significantly from the VBR protocols used by the 2 laboratories. However, there was a statistically significant difference between the 2 laboratories, with ODL showing lower accuracy than NEOLab. Although some differences were statistically significant, they were very small and not considered clinically relevant. There was also a statistically significant difference between the 3 tooth segments (incisors, canines/premolars, and first molars), with VBR of the first molars and second premolars showing the least accuracy.

CONCLUSIONS

The VBR techniques using the in-office Meshmixer, ODL, and NEOLab were considered accurate enough for the clinical use of orthodontic retainers fabricated from printed models.

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.

Influence of rescanning mesh holes and stitching procedures on the complete-arch scanning accuracy of an intraoral scanner: An in vitro study

PURPOSE

To measure the impact of different scanning patches on the accuracy (trueness and precision) of an intraoral scanner (IOS).

MATERIAL AND METHODS

A typodont was digitized using an industrial optical scanner (GOM Atos Q 3D 12 M) to obtain a reference mesh. The typodont was scanned using an IOS (TRIOS 3). Three groups were generated based on the rescan areas created: no mesh holes (G0 group), 3 mesh holes distributed on the digital scan (G1 group), and 3 mesh holes located on the left quadrant of the digital scan (G2 group). In the G0 group, a digital scan was completed following the manufacturer's scanning protocol. In the G1 group, a digital scan was obtained following the same protocol as G0 group. Three 12-mm diameter holes were created in the occlusal surfaces of the left second first molar, incisal edges of the central incisors, and right first molar of the digital scan using the IOS software. In the G2 group, a digital scan was obtained following the same protocol as G0 group. Three 12-mm diameter holes in the digital scan were created in the occlusal surface of the left first molar and left second and first premolars using the IOS software program. The discrepancy between the control and the experimental digital scans was measured using the root mean square calculation. The Kolmogorov-Smirnov test demonstrated that data were normally distributed. One-way ANOVA followed by post hoc multiple comparison Bonferroni test were used to analyze the data (α = .05).

RESULTS

Trueness values ranged from 15 to 26 μm and the precision ranged from 21 to 150 μm. Significant differences in trueness mean values were found among the groups tested (F(2, 42) = 6.622, P = .003); the Bonferroni test indicated significant mean differences between the G0 and G2 groups (mean difference=0.11, SE=0.003, and P = .002). For precision evaluation, significant precision differences were found between the groups tested (F(2, 39)=9.479, P < .001); the Bonferroni test revealed significant precision differences between G0 and G2 groups (mean difference=-0.12, SE=0.030, and P = .001).

CONCLUSIONS

Rescanning mesh holes and stitching procedures decreased the trueness and precision of the IOS tested; furthermore, the number and dimensions of mesh holes rescanned represented an important factor that influenced the scanning accuracy of IOS tested.

CLINICAL SIGNIFICANCE

It is a fundamental procedure obtaining intraoral digital scans without leaving mesh holes, so the rescanning techniques are minimized and, therefore, the scanning accuracy of the intraoral scanner tested is maximized.

Soft tissue-based registration of intraoral scan with cone beam computed tomography scan

The aim of this study was to evaluate a novel soft tissue-based method to register an intraoral scan (IOS) with a cone beam computed tomography (CBCT) scan. IOS and CBCT data were obtained from eight dentate patients (mean age 21±2 years; three male, five female) and 14 fully edentulous patients (mean age 56±9 years; eight male, six female). An algorithm was developed to create a soft tissue model of the CBCT scan, which allowed a soft tissue-based registration to be performed with the IOS. First, validation was performed on dentate jaws with registration of the palatal mucosal surface and accuracy evaluation at the level of the teeth. Second, fully edentulous jaws were registered using both the palatal and alveolar crest mucosal surfaces. Distance maps were created to measure the method accuracy. The mean registration error was 0.49±0.26mm for the dentate jaws. Registration of the fully edentulous jaws had a mean error of 0.16±0.08mm at the palate and 0.16±0.05mm at the alveolar crest. In conclusion, the high accuracy of this registration method may allow the digital workflow to be optimized when no teeth are available to perform a regular registration procedure.

Development and virtual validation of a novel digital workflow to rehabilitate palatal defects by using smartphone-integrated stereophotogrammetry (SPINS)

Palatal defects are rehabilitated by fabricating maxillofacial prostheses called obturators. The treatment incorporates taking deviously unpredictable impressions to facsimile the palatal defects into plaster casts for obturator fabrication in the dental laboratory. The casts are then digitally stored using expensive hardware to prevent physical damage or data loss and, when required, future obturators are digitally designed, and 3D printed. Our objective was to construct and validate an economic in-house smartphone-integrated stereophotogrammetry (SPINS) 3D scanner and to evaluate its accuracy in designing prosthetics using open source/free (OS/F) digital pipeline. Palatal defect models were scanned using SPINS and its accuracy was compared against the standard laser scanner for virtual area and volumetric parameters. SPINS derived 3D models were then used to design obturators by using (OS/F) software. The resultant obturators were virtually compared against standard medical software designs. There were no significant differences in any of the virtual parameters when evaluating the accuracy of both SPINS, as well as OS/F derived obturators. However, limitations in the design process resulted in minimal dissimilarities. With further improvements, SPINS based prosthetic rehabilitation could create a viable, low cost method for rural and developing health services to embrace maxillofacial record keeping and digitised prosthetic rehabilitation.

Design of a Single-Tooth Model and Its Application in Oral Scan System Assessment

Intraoral scanners have been widely used in the application of dentistry. Accuracy includes trueness and precision; they have an important position in the assessment of intraoral scanners. The existing standard models are divided into the inlay and the crown, but the operation is relatively complicated. In this study, in order to simplify the current standard model, we designed a new integration model to compare the accuracy of two intraoral scanners (CEREC and TRIOS) and an extraoral scanner (SHINING). The coordinate measuring machine measured value is the gold standard. Values of the length and angle were analyzed by converting the scanned digital impressions into an STL (standard triangulation language) format to evaluate the accuracy of the intraoral scanner and to verify the feasibility of the designed model. The result shows that the integration model can be successfully scanned and imaged. In the case of the powder-free integration model, intraoral scanner precision, trueness, 3D fitting, and imaging are better than the extraoral scanner. It can be seen straightly from the measurement result and the 3D fitting result that the intraoral scanner can acquire the shape of the standard model integrally with good repeatability. Therefore, it can be concluded that TRIOS is superior to CEREC and SHINING in accuracy, and the integration model is feasible as a reference in the examination of intraoral scanners. The performance of the newly designed integration model that can be scanned is clinically significant, suggesting that this model can be used as a standard reference model.

Accuracy of impression-making methods in edentulous arches: An in vitro study encompassing conventional and digital methods

STATEMENT OF PROBLEM

Studies evaluating the accuracy of edentulous arch impressions encompassing conventional and digital methods are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate 8 impression-making methods for edentulous arches and to determine the effects of using a 3-dimensionally printed polyetheretherketone (PEEK) scanning aid on the accuracy of intraoral scanners.

MATERIAL AND METHODS

Three sets of edentulous arch typodonts were scanned with an industrial scanner as a reference. Subsequently, a scanning aid for the edentulous arch was individually designed on each reference scan dataset by using a 3-dimensional modeling software program and fabricated in PEEK with a 3-dimensional printer. Each typodont was scanned with 2 intraoral scanners 12 times, with and without the assistance of a scanning aid for the edentulous arch. Impressions were made with 4 different conventional impression materials (irreversible hydrocolloid, polysulfide, polyether, and polyvinyl siloxane)-12 times for each typodont-the casts were poured and digitized with a tabletop scanner. Each scan data set was superimposed over the corresponding scan data set, and the original and absolute distance values from the paired surface points were obtained to measure the trueness and precision. These were expressed by using the mean, median, root mean square, and (90 percentile-10 percentile)/2 of the absolute distance value (NMT) concepts, based on the raw data extraction protocol. A repeated-measures ANOVA followed by a post hoc Bonferroni test was conducted (α=.05).

RESULTS

The impression-making methods did not show statistically significant differences (P>.05) for either trueness or precision, particularly when the median values of the original and absolute distance values from the paired surface points were chosen as the standard values. One of the intraoral scanners used exhibited significantly superior outcomes to conventional impression materials when scanned with the scanning aid for the edentulous arch for both trueness and precision when the mean, root mean square, and NMT concepts were applied (P<.05).

CONCLUSIONS

Intraoral scanners demonstrated accuracy comparable with that of conventional impression materials for making edentulous arch impressions, regardless of the concepts used to express the trueness and precision. The PEEK-based scanning aid for the edentulous arch did not improve the accuracy of the intraoral scanners; however, its application resulted in higher accuracy compared with that of conventional impression materials.

Accuracy of Intraoral Scanners for Recording the Denture Bearing Areas: A Systematic Review

PURPOSE

To systematically review clinical and laboratory studies that investigated the accuracy of intraoral scanners in recording denture bearing areas.

MATERIALS AND METHODS

Electronic and manual searches were conducted to identify all the available clinical and laboratory studies reporting the accuracy of digital impressions for recording denture related soft tissues. After the application of predetermined inclusion and exclusion criteria, the final list of articles was reviewed to meet the objective of this study.

RESULTS

The inclusion criteria were met by 18 studies out of which 8 were clinical and the rest were laboratory investigations. The eligible studies assessed the accuracy of intraoral scanners in recording both the denture supporting structures and the peripheral mobile tissues. The accuracy results were different among the various intraoral scanners. Likewise, the effect of several influencing factors, such as artificial markers, scanner head size, scanning strategy, and the operator's experience, were evaluated.

CONCLUSION

While the accuracy of intraoral scanners was comparable to the conventional techniques in recording bony structures with attached mucosa, they were not capable of accurately registering the mobile tissues. In addition, factors such as presence of a marker, larger scanner head size and specific scanning techniques appeared to improve the accuracy of the digital impression.

A digital approach to robust and esthetic implant overdenture construction

OBJECTIVE

Overdenture therapy is an important option for implant rehabilitation. However, numerous reports suggest that mechanical/technical complications and failures can limit therapeutic success. The goal of this report is to illustrate a digital approach to design and construction of a robust overdenture with high-esthetic value.

MATERIALS AND METHODS

Beginning with new denture design to establish esthetic parameters, 3D modeling of a metal framework and the denture teeth are completed in a connected manner. This enables connection of rapidly printed, prototype dentition that is attached directly to the framework without intervening wax or acrylic components. Following evaluation of the dentition and required adjustments, the final dentition is milled from resin and processed to the selective laser sintered framework.

RESULTS

The advantages of the digital workflow include the control of dimensions and strength of the framework, the esthetic relationship of the framework to the dentition and the facilitation of esthetic try-in of the dentition.

CONCLUSION

Enhancing a robust overdenture can be readily achieved using a digital workflow.

CLINICAL SIGNIFICANCE

The use of digital technology enables the clinical team to plan and produce prostheses with dimensions and contours that support long-term function and esthetics. The clinical chair time can be potentially reduced by use of digital design that facilitates try-in and reduces major errors by improved communication between the patient, dentist, and technician.