Standard Tessellation Language Research Articles

Comparison of dimensional accuracy between direct-printed and thermoformed aligners.

ObjectiveThe purpose of this study was to evaluate and compare the dimensional accuracy between thermoformed and direct-printed aligners.MethodsThree types of aligners were manufactured from the same reference standard tessellation language (STL) file thermoformed aligners were manufactured using Zendura FLXTM (n = 12) and Essix ACETM (n = 12), and direct-printed aligners were printed using Tera HarzTM TC-85DAP 3D Printer UV Resin (n = 12). The teeth were not manipulated with any tooth-moving software in this study. The samples were sprayed with an opaque scanning spray, scanned, imported to Geomagic® Control XTM metrology software, and superimposed on the reference STL file by using the best-fit alignment algorithm. Distances between the aligner meshes and the reference STL file were measured at nine anatomical landmarks.ResultsMean absolute discrepancies in the Zendura FLXTM aligners ranged from 0.076 ± 0.057 mm to 0.260 ± 0.089 mm and those in the Essix ACETM aligners ranged from 0.188 ± 0.271 mm to 0.457 ± 0.350 mm, while in the direct-printed aligners, they ranged from 0.079 ± 0.054 mm to 0.224 ± 0.041 mm. Root mean square values, representing the overall trueness, ranged from 0.209 ± 0.094 mm for Essix ACETM, 0.188 ± 0.074 mm for Zendura FLXTM, and 0.140 ± 0.020 mm for the direct-printed aligners.ConclusionsThis study showed greater trueness and precision of direct-printed aligners than thermoformed aligners.

Influence of ambient light conditions on the accuracy and scanning time of seven intraoral scanners in complete-arch implant scans

PurposeThe purpose of this in vitro study was to evaluate the effect of ambient light illuminance on the accuracy and scanning time of different intraoral scanners (IOSs) in complete-arch implant scans. Material and methodsSeven IOSs (TRIOS 3, Primescan, Element 5D, i700, i500, CS3700, and CS3600) at 5 ambient lighting illuminances (100, 500, 1000, 5000, and 10 000 lux) were evaluated. An edentulous cast with 4 implants was selected as the master model. An implant scan body was tightened on each implant. The cast was digitized by using a laboratory scanner to obtain a reference standard tessellation language (STL) file, and 50 scans (10 per ambient light condition) were recorded with each IOS. Scanning time was recorded by using a digital chronograph. Intraoral scan deviations were calculated by using a 3D metrology software program (Geomagic Control X). Kruskal-Wallis and pairwise comparison tests were used to analyze the data (α=0.05). ResultsThe trueness and precision values obtained for each IOS tested were significantly different under the varying lighting conditions assessed. TRIOS 3 (34.0 ± 3.3 µm trueness; 24.5 ± 14.9 µm precision), Element 5D (34.5 ± 7.1 µm trueness; 25.9 ± 7.6 µm precision), and CS3700 (34.9. ±13.0 µm trueness; 34.6 ± 19.2 µm precision) performed better under 100 lux illumination, CS3600 (69.5 ± 24.0 µm trueness; 36.6 ± 20.1 µm precision) at 500 lux; i500 (36.2 ± 5.1 µm trueness; 21.4 ± 6.8 µm precision) at 1000 lux; i700 (34.8 ± 2.2 µm trueness; 15.4 ± 5.0 µm precision) at 5000 lux, and Primescan (37.4 ± 37.3 µm trueness; 26.2 ± 26.2 µm precision) at 10,000 lux. Additionally, the scanning time was different under different illuminance for each IOS. The fastest IOS in all light conditions was Primescan, with significant differences with all the groups (P<.01), followed by TRIOS 3 in all groups except under 100 lux illumination, where i700 was the second fastest. ConclusionsAmbient light influenced the accuracy and scanning time of IOSs assessed; however, the effect was not the same for all devices. It is necessary to optimize ambient light illuminance for each IOS to maximize scanning accuracy.

Positional trueness of abutments by using a digital die-merging protocol compared with complete arch direct digital scans and conventional dental impressions

Statement of problemComplex prosthodontic treatments frequently require capturing an accurate impression of abutment teeth throughout the dental arch. Intraoral digital scanning has been reported to be accurate within single dental quadrants; however, the positional trueness of complete arch intraoral digital scans is not well understood. PurposeThe purpose of this in vitro study was to compare the positional trueness of a complete arch digital scan generated by digitally merging portions of a direct digital scan from an intraoral scanner (IOS) with a digitized polyvinyl siloxane (PVS) complete arch impression. Material and methodsA 3D printed reference cast was scanned with a desktop scanner, and reference standard tessellation language (STL) data sets were obtained. The reference cast was used to generate 4 nonmerged (NM) groups and 2 die-merged (DM) groups. In the NM groups (n=10), a direct digital scan of the reference cast was made with an IOS (NM-IOS), the PVS impression of the reference cast was digitized by using a cone beam computed tomography (CBCT) scanner (NM-PVS-CBCT) or a desktop scanner (NM-PVS-DESK), and the gypsum cast made from the PVS impression was digitized by using a desktop scanner (NM-STONE). In the DM groups (n=10), individual dies were cropped from the complete arch digital scan from the NM-IOS group and merged with the digital scans from the NM-PVS-DESK and NM-PVS-CBCT groups to generate the DM-PVS-DESK and DM-PVS-CBCT groups, respectively. Deviation was measured as the absolute value of the distance from a reference position on the reference cast. The Kruskal-Wallis and Dunn pairwise comparison tests were used to compare the difference in deviation between the groups (α=.05). ResultsThe NM-STONE and NM-PVS-DESK groups demonstrated the highest positional trueness, with global deviations of 19.6 and 17.7 μm, respectively, with no statistically significant difference (P>.999). However, both the NM-IOS and NM-PVS-CBCT groups differed significantly from the NM-STONE group (P<.001 and P=.003, respectively) and the NM-PVS-DESK group (P<.001 and P=.004, respectively). In the DM groups, the DM-PVS-CBCT group presented a higher deviation than the DM-PVS-DESK group. ConclusionsComplete arch digital scans of PVS impressions digitized with a desktop scanner exhibited less positional deviation than those digitized with a CBCT scanner or complete arch digital scans generated with an IOS. Complete arch digital scans generated with an IOS and CBCT scanner result in more deviations in the posterior regions, and their positional trueness may not be sufficient to construct an accurate digital scan. Generating a complete arch digital scan by digitally merging portions of a direct digital scan from an IOS with a digitized PVS complete arch impression is a suitable alternative to the contemporary workflow of digitizing a stone cast with a desktop scanner.

Evaluation of the accuracy of soft tissue thickness measurements with three different methodologies: An in vitro study.

Soft tissue thickness (STT) influences esthetics, peri-implant, and periodontal health. Non-invasive methods of STT evaluation include cone-beam computed tomography (CBCT) with Digital Imaging and Communications in Medicine (DICOM) files and registration of DICOM files with an intraoral scan or Standard Tessellation Language (STL) files. This study compares three methodologies: bone sounding, DICOM data alone, and DICOM and STL registration to absolute histomorphologic values. Five human maxillas, including teeth numbers 6 to 11, provided 90 sites for analysis. For standardization, reference grooves were placed at the cervical margin and the long axis of each tooth. Direct measurements with a no. 25 K-file were completed at the facial soft tissues at 3.00, 5.00, and 7.00mm from the apical marginal reference. Indirect measures were performed with implant planning software. Histological measurements were rendered with imaging software. One-way analysis of variance (ANOVA) was used to compare the three techniques for the differences from histologic measurements (α=0.05). Seventy-two sites were included for final analysis. The overall mean histological STT (mSTT) was 0.73±0.31mm. Bone sounding overestimated mSTT, 0.22±0.20mm (P&lt;0.001); whereas, DICOM alone underestimated mSTT, -0.23±0.19mm (P&lt;0.001). DICOM and STL registration had non-statistically significant differences, -0.04±0.21mm (P=0.429). Intraclass correlation coefficient (ICC) of DICOM and STL registration achieved the highest agreement with histology (ICC: 0.74). DICOM and STL file registration had the highest agreement with histological STT supporting the use of DICOM and STL registration for the evaluation of STT.

Digital planning of composite customized veneers using Digital Smile Design: Evaluation of its accuracy and manufacturing.

ObjectivesThis study aimed to evaluate the production of customized composite veneers starting from a two‐dimensional (2D) digital preview using the Digital Smile System (DSS).Material and MethodsA photographic examination of 30 patients was performed by taking two digital pictures of the face and a digital preview through the DSS. Moreover, optical scans of the dental arches were obtained and the data were entered into a three‐dimensional (3D) software to prepare a virtual preview. The standard tessellation language files were sent for production using CAD‐CAM technology. The Friedman test, Bonferroni, and Dunn post hoc tests were used, comparing the linear measurements of the 2D and 3D plans and the final veneers (α = .05).ResultsSignificant differences emerged between the pictures and digital scans on the mesial–distal widths of the lateral incisors and canine. Linear measurements in the 2D plan were significantly different from those of the 3D plan, except for the height measures of incisors. No significant changes were found on comparing the parameters of the 2D and 3D plans with those of the final pieces.ConclusionsThe customized veneers were clinically adequate and similar to 2D and 3D plans, although significant differences emerged between the picture and digital scans as well as between the 2D and 3D plans.

Evaluation of ridge lap accuracy and adaptation of the diagnostic tooth arrangement fabricated with CAD-CAM systems: An in vitro study

Statement of problemDigital light processing (DLP) and milling (MIL) are computer-aided design and computer-aided manufacturing (CAD-CAM) systems that have become popular for fabricating definitive complete dentures. However, few studies have compared the accuracy of the ridge laps of diagnostic tooth arrangements fabricated with these systems and their adaptation with the denture base sockets. PurposeThe purpose of this in vitro study was to comparatively analyze the accuracy of the ridge laps of the diagnostic tooth arrangements fabricated by using MIL and different layer thicknesses in DLP. Material and methodsA virtual definitive complete denture was designed with a CAD software program on a scanned virtual digital cast, divided into diagnostic tooth arrangement and a denture base that accommodated the arrangement, and saved as a standard tessellation language (STL) file. From this file, 27 diagnostic tooth arrangements were fabricated by DLP (50 μm and 100 μm) and MIL. The ridge laps were scanned and overlapped on the file (reference data) to analyze the accuracy (trueness and precision). The ridge laps of all groups were overlapped on the reference denture base data to analyze their adaptation with the sockets. The measurements of the trueness, precision, and adaptation were analyzed statistically by using the nonparametric Kruskal-Wallis test and post hoc Mann-Whitney U test with Bonferroni correction. ResultsThe diagnostic tooth arrangements showed significant differences among the groups (P<.001). The values were the lowest in the MIL group and highest in the DLP group for the following parameters: trueness root-mean-square (RMS) value, 173 ±7 μm versus 286 ±15 μm; precision RMS value, 22 ±3 μm versus 57 ±20 μm; and adaptation RMS value, 41 ±5 μm versus 112 ±13 μm. ConclusionsOf the 2 diagnostic tooth arrangements fabricated with the CAD-CAM systems, the one fabricated with MIL was clinically more appropriate.

Triangular mesh reduction of digitized maxillectomy defects for prosthetic rehabilitation: A 3D deviation study

ObjectivesTo evaluate the effect of triangular mesh reduction on the trueness of digitized complete-arch dentate and edentulous maxillectomy defects models. Material and MethodsTwenty gypsum maxillectomy defect models (dentate and edentulous group: n = 10) were digitized using the Trios 3 intraoral scanner, scanning the teeth, mucosa and maxillectomy defect. These datasets (reference, R0) were saved as standard tessellation language (STL) files, and triangular mesh reduction was performed using the Meshmixer reduction tool. Digital test-datasets with file sizes reduced by 50%(R1), 75%(R2), and 90%(R3) were generated (each: n = 20). Each test-dataset was compared to the R0 file using a 3D evaluation software (GOM Inspect), applying automated pre-alignment followed by a best-fit alignment, and root mean square (RMS) 3-dimensional (3D) deviations were calculated. Statistical analyses were performed, at a level of significance of α=0.05. ResultsThe number of triangles, and STL file size were synchronized with each other and inversely proportional to the amount of mesh reduction. The resulting mean percentages of the STL file sizes were 50.00% for R1, 24.93% for R2, and 10.00% for R3. There were no 3D deviations at 50% triangular mesh reduction. The 3D deviations increased with the amount of mesh reduction: at 75% reduction the median deviations were lower (dentate:0.0016 mm, IQR:0.0015–0.0018; edentulous:0.0016 mm, IQR:0.0015–0.0016), than at 90% (dentate:0.004 mm, IQR:0.0038–0.0041; edentulous:0.003 mm, IQR:0.0036–0.0039). A statistically significant increase in 3D deviations was observed with higher degrees of mesh reduction (p<0.001). ConclusionsTriangular mesh reduction results in a significant increase in 3D deviations if the reduction is more than 75%. Clinical SignificanceDigital models of patients with maxillectomy defects can be saved with a mesh reduction of 50% without affecting the trueness. The use of a 50% mesh reduction decreases the required storage capacity by 50%.

Complete Digital Workflow for Prosthesis Prototype Fabrication with Double Digital Scanning: Accuracy of Fit Assessment.

To assess the accuracy of a complete digital workflow protocol for fabrication of printed prosthesis prototypes for maxillary immediate loading treatment. A maxillary stone cast with 4 abutment-level implant analogs with adequate antero-posterior spread was fabricated. This stone cast served as a reference cast and a zirconia prosthesis was also fabricated to serve as an interim prosthesis. Double digital scanning was used for digital scans of the reference cast and the interim prosthesis, respectively. An intraoral scanner (TRIOS® 3) was used to capture the standard tessellation language (STL) files. These STL files were then imported to computer-aided design (CAD) software (Exocad DentalCAD) and superimposed into a final design STL file that was exported to 3 different (Form 3b+, Carbon M2, Sprintray Pro95) three-dimensional (3D) printers to produce a total of 90 printed prototypes (n = 30 from each 3D printer). Two blinded clinicians assessed the accuracy of fit of each digitally fabricated prosthesis prototype on the reference cast, utilizing the screw-resistance test and radiographs. The Fisher's exact test was used to test the difference between the groups. Out of the 90 digitally fabricated prototypes, 86 (95.6%) presented with accurate fit. The accuracy of fit ranged from 87% (26/30) for Sprintray Pro95 to 100% (30/30) for the Form 3b+ and M2 Carbon groups. Digitally fabricated prosthesis prototypes can be generated with a complete digital workflow leading to clinically acceptable fit, while reducing the number of appointments and treatment time. The 3D printer had an effect on the accuracy of prosthesis prototype fit.

3D Printing in Dental Science

3D printing is a technology that describes a manufacturing process previously planned and designed in a computer to create an object 1,2. This technology was introduced in dentistry by Chuck Hull since 1986 and allowed the automation and thus improved dental workflow 2. Technologies used in 3D printing involves: Stereolithography (SLA), bioprinting, fused deposition modeling (FDM), selective laser sintering (SLS), and PolyJet printing. We can choose one of them depending on the clinical use and material, need of accuracy among others. To 3D printing you need to use a scanner with an integrated software in order to capture the 3D images of the object being scanned. Those 3D images are stored in Standard Tessellation Language (STL) file 3. But what “Tessellation” means? Tessellation is the covering process of a surface, using one or more geometric shapes, with no overlaps and no gaps. It means that the object scanned is copied in detail with high reliability and then can be printed. Before printing, the software cuts the STL file into multiple horizontal layers and creates the G-code for the machine command for the printer. Thus, the resolution of the printer is determined by its layer thickness (z-axis) which represents the vertical accuracy of 3D printer 1. There are two approaches used to fabricate 3D objects: subtractive approach (milling); additive approach (layered manufacturing) 4 . The first, normally use a small model or block to machining it and is indicated to fabricate ceramic crowns in dentistry. The last, can produce complex structures and thus is suitable for reproduce the anatomy of different structures of oral cavity 4.

Chemical Composition and Flexural Strength Discrepancies Between Milled and Lithography-Based Additively Manufactured Zirconia.

To evaluate the chemical composition, flexural strength, and Weibull characteristics of milled and lithography-based additively manufactured (AM) zirconia. A virtual design of a bar (25×4×2mm) was completed using a software program. The standard tessellation language file was used to manufacture all the specimens: 3Y-TZP zirconia (Priti multidisc ZrO2 monochrome) milled (M group) and 3Y-TZP zirconia (LithaCon 3Y 210) lithography-based AM (CeraFab System S65 Medical) (AM group) bar specimens (n = 20). The chemical composition of the specimens was determined by using energy dispersive X-ray (EDAX) elemental analysis in a scanning electron microscope. Flexural strength was measured in all specimens using 3-point bend test according to ISO/CD 6872.2 with a universal testing machine (Instron Model 8501). Two-parameter Weibull distribution values were calculated. The Shapiro-Wilk test revealed that the data were normally distributed (p < 0.05). Flexural strength values were analyzed using independent Student's t-test (α = 0.05). There were no major chemical composition differences observed between M and AM groups. The AM specimens (1518.9 ± 253.9 MPa) exhibited a significantly higher flexural strength mean value compared to the milled (980.5 ± 130.3 MPa) specimens (DF = 13, T-value = -5.97, p < 0.001). The Weibull distribution presented the highest shape for M specimens (11.49) compared to those of AM specimens (6.95). There was no significant difference in the chemical composition of milled and AM zirconia material tested. AM zirconia tested exhibited significantly higher flexural strength compared with the milled zirconia evaluated.

Accuracy of three digital waxing–guided trial restoration protocols for controlling the depths of tooth preparation for ceramic veneers

Statement of problemThe accuracy of digital waxing–guided trial restoration protocols that have been implemented with ceramic veneers has not been reported. PurposeThe purpose of this in vitro study was to evaluate the accuracy of 3 digital trial restorations fabricated from digital waxing for ceramic veneers. Material and methodsA uniform 0.3-mm digital waxing added to the facial surface of 30 maxillary central typodont incisors was created in a software program. The trial restorations were fabricated on typodont teeth with autopolymerizing acrylic resin by using a silicone index based on 3-dimensionally printed casts designed from the digital waxing. The 30 maxillary central incisors were divided into 3 groups: the depth cutter (0.5 mm, Komet) (DC) group, the round bur (1.5 mm, Diatech) (RB) group, and the specially designed calibrated depth bur (laser mark of 0.5 mm, Gaofeng) (CD) group. The 3 groups were randomly prepared with a random number table by 2 experienced prosthodontists aiming to produce an even facial clearance of 0.5 mm. The dimensional differences in the standard tessellation language (STL) files between the surfaces of the original teeth, digital waxing, trial restorations, and prepared teeth in the software program were measured and analyzed at the same 9 points on the labial surface. One-way ANOVA with a post hoc test was used to identify significant discrepancies between trial restorations and waxing and differences in the reduction depth of typodont teeth (RDT) and the reduction depth (RD) among the 3 techniques (α=.05). The mean relative differences (MRDs) were calculated to determine the accuracy (%). ResultsThe thickness of the trial restorations was significantly greater than that of the digital waxings, with a discrepancy of 0.20 ±0.14 mm, especially at the cervical site. With the use of a trial restoration, the RDTs of the middle (-0.01 ±0.11 mm) and cervical locations (0.09 ±0.20 mm) showed significantly smaller preparation depths than did the other locations. Significant differences in RD were found among the 3 guided techniques (P<.05). Group DC presented the most accurate result of 0.51 ±0.08 mm with an MRD of 2%, whereas the results of 0.57 ±0.10 mm with an MRD of 14% and 0.60 ±0.11 mm with an MRD of 20% were obtained from group RB and group DC, respectively. ConclusionsThe trial restoration was significantly thicker than its corresponding waxing. The DC technique presented the most accurate reduction result among the 3 protocols examined.

PRESS and Piezo Microsurgery (Bony Lid): A 7-Year Evolution in a Residency Program—Part 2: PRESS-Defined Site Location

IntroductionTreatment of a failing endodontic procedure via microsurgical revision presents better outcomes due, in part, to the integration of the surgical operating microscope and cone-beam computed tomography into clinical practice. However, challenges still remain with respect to the operational locations and the techniques required to address them. Posterior sites, with substantial cortical plate thicknesses and sensitive anatomy, present the dichotomy of visualization versus postsurgical regeneration of bone. The bony lid technique bridges the gap between these 2 concepts, and the application of piezosurgery renders a precise and biocompatible osseous incision. The purpose of this article was to outline through case reports the progression of piezo-guided surgery in a resident setting. MethodsThe first 2 evolutions of the technique used a surgeon-defined method for site location. This third and final evolution uses a digital workflow to virtually plan the surgical procedure, integrating Standard Tessellation Language and Digital Imaging and Communication in Medicine files to create 3-dimensional guides with exacting resection locations, levels, and angles. Export of the virtually planned guide in postproduction generates the precision endodontic surgical stent to accurately define the site location and parameters of the procedure. All surgeries were executed using the piezosurgical method with increasing levels of guidance and precision throughout the evolution process. ResultsEach step in the technique implementation enabled the resident to assimilate a new technique and skill set while maintaining bone architecture and minimizing volume loss postoperatively. The patient benefits were an increase in intraoperative safety and postoperative comfort. The resident benefits were accelerated regeneration timetables and increases in the confidence level of the resident and the number of scheduled posterior surgical procedures. ConclusionsThe progression from crude on-site measurements to elegant and precise surgical guides enabled the access and manipulations of difficult surgical sites without compromising visibility, postoperative osseous regeneration, or patient comfort.

Guided endodontic treatment in a region of limited mouth opening: a case report of mandibular molar mesial root canals with dystrophic calcification

BackgroundThe endodontic treatment of calcified root canals in molars is a challenging and time-consuming procedure. Even with the aid of a surgical microscope, the risk of root perforation is high, especially in the furcation area. The purpose of this study is to report the Computer-Aided-Design and Manufacturing (CAD–CAM) workflow, the innovative strategies for the template ideation, and the guided endodontic treatment of a mandibular molar with dystrophic calcification in the mesial root canals.Case presentationA 58-year-old female patient, ASA I, was referred to endodontic treatment in the right first mandibular molar for prosthetic reasons. The mesiobuccal and mesiolingual canals appeared obliterated in the radiographic images. The absence of dental crown, tooth inclination, and the limited mouth opening of the region contributed to a poor visual reference of the tooth in the dental arch and the direction of the remaining lumens of the canals. Despite using surgical microscopy, the conventional technique led to the deviation of the mesiobuccal canal towards the furcation area. The obliteration of both mesial root canals was confirmed using the Cone Beam Computer Tomography. The clinical history associated with the tomography diagnosis was compatible with dystrophic calcifications in the pulp canals. The patient was submitted to an intra-oral scanning as well. The Digital Imaging and Communications in Medicine data (DICOM) were segmented. The Standard Tessellation Language (STL) files were processed following the CAD–CAM workflow, aiming to create two different endodontic templates with a new open design concept. The templates with open design allowed direct visualization of the operative field, irrigation, and dentin debris removal. The strategy of the guidance sleeves niche as half-cylinders allowed the drill insertion in a limited mouth opening region.ConclusionsThe digital planning and guided access permitted to overcome the case limitations and then re-establish the glide path following the original anatomy of the root canals. The guided endodontic represents a personalized technique that provides security, reduced risks of root perforation, and a significant decrease of the working time to access obliterated root canals even in the mesial root canal of mandibular molars, a region of limited mouth opening.

Influence of different material substrates on the accuracy of 3 intraoral scanners: A single-blinded in vitro study.

To compare the accuracy of three commercially available intraoral scanners when imaging various dental material substrates. A maxillary dentate typodont model with 11 different dental material substrates was prepared and scanned using three intraoral scanners (TRIOS 3, 3Shape; CS 3600, Carestream; and Emerald S, Planmeca). The model was further scanned with a laboratory scanner (7series, Dental Wings) for reference. Files were exported in standard tessellation language format and inserted into a metrology 3D mesh software (CloudCompare). In terms of influence of different substrates on IOS trueness, a significant effect on the performance of TRIOS 3 and Emerald S was revealed. Concerning the accuracy of different intraoral scanners when scanning more translucent and reflective materials, pairwise comparisons revealed significant differences among scanners. In terms of complete-arch trueness and precision, pairwise comparisons revealed that TRIOS 3 had significantly higher trueness and precision compared to CS3600 and Emerald S. The complete-arch trueness and precision of CS3600 and Emerald S did not differ significantly. Dental material substrates influenced the accuracy of all three tested scanners. The full metal crown exhibited significantly lower trueness compared to other substrates across all three scanners. For the high-translucency substrate group, TRIOS 3 exhibited significantly higher trueness compared to CS 3600. Polished and unpolished class II amalgam restorations of similar dimensions did not exhibit significant differences in trueness regardless of intraoral scanner. In terms of complete-arch accuracy, TRIOS 3 had significantly higher trueness and precision compared to CS 3600 and Emerald S. All three scanners exhibited complete-arch average accuracy below 100 μm.

Dimensional ridge changes in conjunction with four implant timing protocols and two types of soft tissue grafts: A pilot pre‐clinical study

To determine the effect of (1) implant placement timing and (2) the type of soft tissue graft in terms of ridge profile changes. Four implant treatment modalities were applied in the mesial root areas of the third and fourth mandibular premolars of 10 mongrel dogs alongside connective-tissue graft (CTG) and volume-stable cross-linked collagen matrix (VCMX): immediate, early, and delayed placement (DP), and DP following alveolar ridge preservation (ARP). All dogs were sacrificed 3months after soft tissue augmentation. Standard Tessellation Language files from designated time points were analysed. Compared with the pre-extraction situation, the median width of the ridge demontstrated a linear increase only in group ARP/CTG (0.07 mm at the 2-mm level), whereas all other groups showed a reduction (between -1.87and -0.09 mm, p > .05). Groups ARP/CTG (0.17 mm) and DP/CTG (0.05 mm) exhibited a profilometric tissue gain in a set region of interest (p > .05). The net effect of CTG and VCMX ranged from 0.14 to 0.79 mm. Dimensional ridge changes varied between treatment protocols. ARP with CTG led to the smallest difference in ridge profile between the pre-extraction and the study end time point. Both CTG and VCMX enhanced the ridge contour.

Effect of splinting scan bodies on trueness of complete-arch implant impression using different intraoral scanners: an in vitro study.

To evaluate the trueness of seven different intraoral scanners (IOSs) in making a complete-arch digital scan with and without splinting the scan bodies. A polyurethane cast of an edentulous mandible with four dental implant analogs was prepared. A reference scan was made using a laboratory scanner. The reference model was scanned with each of the seven investigated IOSs (control groups, n = 10 per scanner), and scanned again after splinting the scan bodies (study groups, n = 10 per scanner). Each scan was exported as a standard tessellation language (STL) file and transferred to a comprehensive metrology software program (Geomagic Control X). In order to measure the trueness, four points (A, B, C, and D) were determined on the scan bodies, and the distance between point A and the other points (DAB, DAC, and DAD) was measured. The measurements were tested for normality using the Kolmogorov-Smirnov test and probability plots. Trueness was compared using three-way analysis of variance (ANOVA), and pairwise comparisons were performed using the post hoc Tukey and paired sample t tests. Statistical analyses were two-sided, and the significance level was set at 5%. Splinting the scan bodies improved the trueness values of the digital scans, while increasing the interimplant distance decreased them. A significant association was found between the trueness values and all three tested variables, including splinting the scan bodies, type of IOS, and interimplant distance (P < 0.001). Based on the present findings, splinting the scan bodies can improve the trueness of complete-arch digital implant scans due to the improvement in morphologic landmarks by the stitching process, regardless of the type of IOS or the interimplant distance. (Int J Comput Dent 2023;26(1): 19-0; doi: 10.3290/j.ijcd.b2599297).

Biomechanical behavior of endocrown restorations with different cavity design and CAD-CAM materials under a static and vertical load: A finite element analysis

Statement of problemThe influence of different restorative materials, the divergence angle, and the preparation design of the pulp chamber floor in endocrowns on stress distribution is unclear. PurposeThe purpose of this finite element analysis study was to evaluate the stress distribution and maximum von Mises stress values in endocrown restorations and remaining teeth. Material and methodsAn endodontically treated first mandibular molar was prepared with 2-mm occlusal reduction, a butt-joint margin, and a mesial box with a 4-mm buccolingual extension to receive an endocrown restoration. The model was then scanned, and the exported standard tessellation language file was designed according to the anatomic references by using a computer-aided design software program. The reference model was duplicated, and 27 variations were formed: restorations made of IPS e.max, Vitablocs MarkII, and Vita Enamic, as well as different divergence angles of 6, 12, and 16 degrees prepared with 3 variations of pulp chamber floor designs, keeping the natural form, adding a 1-mm glass ionomer pulp chamber base, and adding a 2-mm extension into the distal canal. Stress distribution under axial loading and maximum von Mises stress values were analyzed and calculated by using the Ansys software program. ResultsThe endocrown restoration presented the lowest von Mises stress values when a 6-degree divergence angle was used with Vitablocs MarkII. However, in other layers such as enamel, resin cement, and pulpal floor, the lowest von Mises stress values were observed in IPS e.max restorative material when the divergence angle was increased to 16 degrees. No difference was found in the stress distribution pattern and maximum von Mises stress values in the alveolar bone or periodontal ligament. ConclusionsEndocrowns fabricated with lithium disilicate ceramics without intraradicular extension exhibited lower stresses on tooth structure. An increase in the divergence angle improved the stress distribution on tooth structure; however, sound dental tissue should not be removed to achieve better stress distribution.

A novel reference model for dental scanning system evaluation: analysis of five intraoral scanners.

PURPOSEThe aim of this in vitro study was to investigate the accuracy (trueness and precision) of five intraoral scanners (IOS) using a novel reference model for standardized performance evaluation.MATERIALS AND METHODSFive IOSs (Medit i500, Omnicam, Primescan, Trios 3, Trios 4) were used to digitize the reference model, which represented a simplified full-arch situation with four abutment teeth. Each IOS was used five times by an experienced operator, resulting in 25 STL (Standard Tessellation Language) files. STL data were imported into 3D software (Final Surface®) and examined for inter- and intra-group analyses. Deviations in the parameter matching error were calculated. ANOVA F-test and Kruskal-Wallis test were applied for inter-group comparisons (α = .05); and the coefficient of variation (CV) was calculated for intra-group comparisons (in % ± SD).RESULTSPrimescan (matching error value: 0.015), Trios 3 (0.016), and Trios 4 (0.018) revealed comparable results with significantly higher accuracy compared to Medit i500 (0.035) and Omnicam (0.028) (P < .001). For intra-group comparison, Trios 4 demonstrated the most homogenous results (CV 15.8%).CONCLUSIONThe novel reference model investigated in this study can be used to assess the performance of dental scanning technologies in the daily routine setting and in research settings.

A Comparative Evaluation of Trueness of Two Intraoral Scanners for a Partially Edentulous Arch - An In Vivo Study

Aim: The purpose of this in vivo study was to evaluate the trueness of two intraoral scanners, 3SHAPE TRIOS IOS and CARESTREAM CS3600 IOS in comparison with conventional elastomeric monophase vinyl polysiloxane impression and also to comparatively evaluate the accuracy of maxillary and mandibular arches when digital impressions are performed. Methods: Sixteen partially edentulous patient cases which followed the inclusion criteria were selected for the study. As a reference model, the STL (Standard Tessellation Language) file obtained by digitization of cast poured using conventional impression technique was used. As test models, the STL files obtained by two intraoral scanners were applied. Three-dimensional analyses were carried out between these three groups and the obtained deviation values were statistically analyzed using the student ‘t’ test. Results: The analysis done by student test-test showed no statistically significant differences (p=0.837) in mean X, Y, Z coordinate deviations between the 3 SHAPE TRIOS IOS® and CS3600 IOS® groups. The results showed that the mean X, Y, Z coordinate deviation in 3SHAPE TRIOS IOS group (0.001±0.008) was not statistically significant when compared to the CS3600 IOS group (0.0017± 0.11). Conclusion: 3SHAPE TRIOS® IOS showed lesser deviation when compared to CARESTREAM CS3600® IOS but there were no statistically significant differences between the two intraoral scanners. Further, it was also concluded that maxillary and mandibular arches do not show any difference in accuracy. Hence both the intraoral scanners can be used with equal efficiency for restorative procedures.

The Utilization of Three-Dimensional Printing in Creating a Surgical Instrument: An Areola Cookie Cutter.

Three-dimensional (3D) printing is a rapidly evolving technology with many applications in the medical field. It involves printing solid objects from a digital file. In this paper, we describe our experience with the use of 3D printing in creating an areola cookie cutter that is compatible with sterilization. The objective of this study is to explore accurate and cost-effective methods of producing patient-specific areola cookie cutters. Auto computer-aided design (CAD) 3D software was used to design a digital model that was subsequently converted to a standard tessellation language (STL) file. The models were printed with the Formlabs Form 3+ SLA printer (Somerville, MA) using a resin material. Washing and curing were then performed followed by autoclave sterilization of the models. A total of 3 areola cookie cutters were created, each with different sizes (33, 38, and 42 mm) using resin material (Formlabs BioMed Clear Resin; Somerville, MA). All 3 models were able to withstand autoclave sterilization. The use of 3D printing has proven to be a valuable tool in Plastic surgery. We describe our experience of designing and producing an areola cookie cutter using a 3D printer; our model is compatible with the process of sterilization. We emphasize the advantages of a quick production time and accuracy in design.