Error propagation from intraoral scanning to additive manufacturing of complete-arch dentate models: an in vitro study

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

OBJECTIVES

This study compared the accuracy of seven intraoral scanners (IOS) by the virtual-fit method.

METHODS

Four maxillary arches with tooth abutments were scanned with an industrial reference scanner (n=1) and by Aoralscan3, EmeraldS, Helios600, Lumina, Mediti700, Primescan, and Trios5 IOSs (each n=12). Two complete-arch fixed frameworks were designed on each IOS scan with a 70 µm (group 70) and a 90 µm internal cement space (group 70+20, additional 20 µm at the margin). The virtual-fit method was comprised of superimposing the framework designs onto the reference scan using a non-penetrating algorithm simulating the clinical try-in. Internal and marginal gaps were measured. Precision was estimated by the mean absolute errors (MAE).

RESULTS

In group 70, Mediti700 (43 µm), Primescan (42 µm), and EmeraldS were in the best homogenous subset for the marginal gap, followed by the Lumina (67 µm), Aoralscan3 (70 µm), and Trios5 (70 µm), whereas Helios600 (118 µm) was in the third subset. Based on the MAE at the margin, Mediti700, Trios5, and EmeraldS were in the first-best homogenous subset, followed by Primescan. Lumina and Helios600 were in the third subset, and Aoralscan3 was in the fourth subset. In group 70+20, the marginal gap was significantly decreased for Lumina and Aoralscan3, whereas MAE significantly decreased for EmeraldS and Aoralscan3. The rank of IOSs was similar for the internal gap.

CONCLUSION

EmeraldS, Mediti700, Primescan, and Trios5 meet the marginal and internal fit criteria for fixed tooth-borne complete arch restorations. Increasing the cement space during design could enhance restoration fit.

CLINICAL SIGNIFICANCE

The virtual-fit alignment method can effectively evaluate the accuracy of different intraoral scanners, offering valuable clinical guidance for distinguishing among them. Recent software and hardware versions of long-standing IOS manufacturers are suitable for fabricating complete arch restoration.

Effect of 3D printer, implant analog and angulation on the accuracy of analog position in implant casts

OBJECTIVES

To evaluate the accumulative effect of 3D printer, implant analog systems, and implant angulation on the accuracy of analog position in implant casts.

METHODS

A reference cast, presenting a case of a three-unit implant-supported prosthesis, was scanned with a coordinate measurement machine, producing the first reference data set (CMM, n = 1). The second reference data set (n = 10) was prepared using an intraoral scanner (IOS) (Trios4). Test quadrant casts were produced using three DLP type 3D printers, Max (MAX UV385), Pro (PRO 4K65 UV), and Nex (NextDent 5100), and three implant analog systems, El (Elos), Nt (Nt-trading), and St (Straumann) (n = 90). Stone casts were also produced via analog impressions (Stone, n = 10). After digitization, the accuracy of 3D distance, local angulation (angle between implants) and global angulation (angle between the implant center axis and an axis perpendicular to the global plane) was evaluated by comparing the reference (CMM, IOS), test (3D print), and control (Stone) groups using metrology software. Data were statistically analyzed using three-way ANOVA and Tukey`s tests (α = 0.05).

RESULTS

IOS was truer in 3D implant distance and more precise in capturing local angulation than Stone (p ≤ 0.05). Other measurements were similar between both groups (p > 0.05). The amount of error introduced in the workflow by IOS and 3D printing was mostly similar (p > 0.05). 3D printed casts had similar or even higher accuracy than Stone group (p > 0.05). In most cases, higher trueness was achieved when using PRO 4K65 UV 3D printer and Elos implant analog system (p ≤ 0.05).

CONCLUSION

3D printer, implant analog system, and implant angulation have a significant effect on the accuracy of analog position in implant casts. Limited-span implant-supported cases could be reproduced digitally with similar accuracy as conventional methods.

CLINICAL SIGNIFICANCE

A fully digital workflow with a carefully selected 3D printer and implant analog system can increase the accuracy of digitally produced implant casts with comparable accuracy to conventional workflow.

Trueness of maxillomandibular relationship in 3D-printed and conventional casts

OBJECTIVES

To compare the trueness of maxillomandibular relationship between articulated 3D-printed and conventional diagnostic casts in maximum intercuspation (MIP).

METHODS

Reference casts were articulated in MIP, and scanned using a Coordinate Measurement Machine (CMM, n = 1). Digital scans were made from the reference casts by using an intraoral scanner (IOS, n = 10) (Trios 4; 3Shape A/S). IOS scans were processed to create 3D-printed casts by using MAX UV385 (Asiga) and NextDent 5100 (3DSystems) 3D-printers. The conventional workflow implemented vinylpolysiloxane (VPS) impressions and Type IV stone. Stone and 3D-printed casts were articulated and digitized with a laboratory scanner (E4; 3Shape A/S). The 3D-printed casts were scanned on two occasions: with and without positioning pins. Inter-arch distances and 3D-contact area were measured and compared. Statistical tests used were Shapiro-Wilk, Levene's, Welch's t-test, and 2-way ANOVA (α=0.05).

RESULTS

IOS group showed similar or better maxillomandibular relationship trueness than stone casts and 3D-printed casts (p < 0.05). 3D-contact area analysis showed similar deviations between 3D-printed and stone casts (p > 0.05). The choice of 3D-printer and presence of positioning pins on the casts significantly influenced maxillomandibular relationship trueness (p < 0.05).

CONCLUSIONS

Articulated 3D-printed and stone casts exhibited similar maxillomandibular relationship trueness.

CLINICAL SIGNIFICANCE

Although 3D-printing methods can introduce a considerable amount of deviations, the maxillomandibular relationship trueness of articulated 3D-printed and stone casts in MIP can be considered similar.

Coordinate-based data analysis of the accuracy of five intraoral scanners for scanning completely dentate and partially edentulous mandibular arches

STATEMENT OF PROBLEM

Current methods for assessing the accuracy of intraoral scanners (IOSs) that reduce errors and provide comprehensive data compared with previous methods are lacking.

PURPOSE

The purpose of this in vitro study was to present a coordinate-based data analysis method to compare the accuracy of 5 IOSs for scanning completely dentate and partially edentulous casts.

MATERIAL AND METHODS

Reference scans of 2 complete arch casts (completely and partially dentate) were digitized using a high-precision laboratory scanner (Ceramill Map 600). Each cast was scanned 10 times each using 5 IOSs (3Shape TRIOS 3, Planmeca Emerald, iTero Element 5D, Medit i500, and Shining Aoralscan 3). The dataset of all 10 test groups was analyzed by using a reverse engineering software program (Geomagic Wrap). Each test cast was aligned with the reference cast by 3-dimensional (3D) superimposition to determine the translation and rotation along the x-, y-, and z-axes. The dataset was analyzed using the Kruskal-Wallis and post hoc Bonferroni tests (α=.05).

RESULTS

Significant differences were observed in all parameters among all scanners when scanning the same cast (P<.05). Significant differences were observed in at least 1 parameter for all scanners, except Element 5D after scanning different casts using the same scanner. Deviations in the test data generally relocated toward the mesial, buccal, and apical sides, and the casts were almost always rotated clockwise around the y-axis and counterclockwise around the z-axis. For the completely dentate cast, among all IOSs, Element 5D demonstrated the highest accuracy in most of the measured parameters, specifically in the y-axis translation (0.06[0.07] mm), z-axis translation (0.08[0.05] mm), and y-axis rotation (0.21[0.16] degree) (P<.05). For the partially edentulous cast, Element 5D displayed higher accuracy in most of the measured parameters, including the x-axis translation (0.11[0.14] mm) and z-axis rotation (0.12[0.18] degree) (P<.05). Emerald also displayed higher accuracy in most of the measured parameters, including the y-axis translation (0.05[0.08] mm) and y-axis rotation (0.14[0.12] degree) (P<.05). Element 5D exhibited no difference in the scanning accuracy between the 2 types of casts (P>.05).

CONCLUSIONS

Element 5D offered a high level of accuracy and was an appropriate scanner for both situations. The method presented in this study provides a good assessment of accuracy deviations in complete arch scans using 3D coordinate-based data analysis.

Positional trueness of three removable die designs with different root geometries manufactured using stereolithographic 3D printing

STATEMENT OF PROBLEM

Three-dimensional (3D) printed casts are a suitable alternative to dental stone casts. Contemporary dental design computer programs permit designing definitive casts with removable dies with different root geometries and retention mechanisms. Studies on the positional trueness of 3D-printed removable dies with different root geometries are lacking.

PURPOSE

The purpose of this in vitro study was to investigate the 3D displacements of three 3D-printed removable die designs with different root geometries.

MATERIAL AND METHODS

The digital file of a dental stone alveolar cast with root-form removable dies (MOD UJ IV Fixed Prosthetics; Ivoclar AG) was used as a reference to create 3 removable die and alveolar cast designs (Root Form, RF; Conical, CON; Cylindric, CYL) with different root geometries in 2 dental design computer programs (DentalCAD 3.1 Rijeka; exocad; GmbH; InLab CAD 22.0; Dentsply Sirona). 3 equidistant Ø1-mm spheres (C, Cervical; M, Middle; O, Occlusal) were designed on the buccal surface of the coronal portion of the removable die to evaluate their displacement. A total of 45 alveolar casts with 45 removable dies were fabricated using a stereolithographic 3D printer (Form 3; Formlabs); each die group consisted of 15 specimens. After fabrication and postprocessing, the specimens were scanned, and their digital files were analyzed in a metrology-grade computer program to evaluate the displacement of the removable dies with respect to the position of the die in the master reference file. Subsequently, the data were analyzed using a 3-way analysis of variance (ANOVA) followed by step-down Bonferroni-corrected pairwise comparisons (α=.05).

RESULTS

Two statistically significant 2-way interactions were detected between the independent variables, die design and direction (P<.001), and location and direction (P<.001). The post hoc analysis identified significant differences between the displacement values of RF and CYL (P<.001) and RF and the CON (P<.001) designs on the Y axis. The measured displacements were statistically different between the C and O locations on the Y axis (P=.001) and the M and O locations on the Z axis (P=.006).

CONCLUSIONS

The root geometry of a 3D-printed removable die and alveolar cast can affect seating, and variable degrees of tipping of the removable die can be seen. The seating and congruence of the removable die with the interocclusal space and relationships observed intraorally should be confirmed before adjusting indirect restorations.

In vitro comparison of five desktop scanners and an industrial scanner in the evaluation of an intraoral scanner accuracy

OBJECTIVES

The study aimed to compare the precision of ATOS industrial, 3ShapeE4, MeditT710, CeramillMap400, CSNeo, PlanScanLab desktop, and Mediti700 intraoral scanners. The second aim was to compare the trueness of Mediti700 assessed by ATOS and desktop scanners.

METHODS

Four plastic dentate models with 7-12 abutments prepared for complete arch fixed dentures were scanned by all scanners three times. Scans were segmented to retain only the abutments. The precision and trueness were calculated by superimposing scans with the best-fit algorithm. The mean absolute distance was calculated between the scan surfaces. The precision was calculated based on the 12 repeats. Trueness was evaluated by superimposing the desktop and IOS scans to the industrial scans. IOS was also aligned with the two most accurate desktop scanners.

RESULTS

The precision of 3ShapeE4 and MeditT710 (3-4μm) was only slightly lower than that of ATOS (1.7μm, p<0.001) and significantly higher than CeramillMap400, CSNeo, and PlanScanLab (6-10 μm, p<0.001). The trueness was the highest for the 3Shape E4 (12-13 μm) and Medit T710 (13-16 μm) without significant difference. They were significantly better than CeramillMap400, CSNeo, and PlanScanLab (22-31μm, p<0.001). Accordingly, the Mediti700 trueness was evaluated by ATOS, 3ShapeE4, and MeditT710. The three trueness was not significantly different; ATOS (23-26 μm), 3Shape E4 (22-25 μm), and Medit T710 (20-23 μm).

CONCLUSIONS

All desktop scanners had the acceptable accuracy required for a complete arch-fixed prosthesis. The 3Shape E4 and the Medit T710 might be used as reference scanners for studying IOS accuracy.

CLINICAL SIGNIFICANCE

3ShapeE4, MeditT710, CeramillMap400, CSNeo, PlanScanLab laboratory, and Mediti700 intraoral scanners can be used for the prosthetic workflow in a complete arch. 3ShapeE4 and the MeditT710 could be used to test the accuracy of various phases of a laboratory workflow, replacing the industrial scanners.

Obturator Manufacturing for Oronasal Fistula after Cleft Palate Repair: A Review from Handicraft to the Application of Digital Techniques

An oronasal fistula (ONF) is an abnormal structure between the oral and nasal cavities, which is a common complication of cleft palate repair due to the failure of wound healing. When some patients with ONF are unsuitable for secondary surgical repair, the obturator treatment becomes a potential method. The objectives of the obturator treatment should be summarized as filling the ONF comfortably and cosmetically restoring the dentition with partial function. The anatomy of patients with cleft palate is complex, which may lead to a more complex structure of the ONF. Thus, the manufacturing process of the obturator for these patients is more difficult. For performing the design and fabrication process rapidly and precisely, digital techniques can help, but limitations still exist. In this review, literature searches were conducted through Medline via PubMed, Wiley Online Library, Science Direct, and Web of Science, and 122 articles were selected. The purpose of this review was to introduce the development of the obturator for treating patients with ONF after cleft palate repair, from the initial achievement of the obstruction of the ONF to later problems such as fixation, velopharyngeal insufficiency, and infection, as well as the application of digital technologies in obturator manufacturing.