- Email: [email protected]
In vitro comparison of trueness of 10 intraoral scanners for implant-supported complete-arch fixed dental prostheses
RESEARCH AND EDUCATION
In vitro comparison of trueness of 10 intraoral scanners for implant-supported complete-arch fixed dental prostheses Caglar Bilmenoglu, DDS, PhD,a Altug Cilingir, DDS, PhD,b Onur Geckili, DDS, PhD,c Hakan Bilhan, DDS, PhD,d and Tayfun Bilgin, DDS, PhDe For implant-supported fixed ABSTRACT dental prostheses, the impresStatement of problem. Digital scanning systems have become popular, but whether these systems sion plays a direct role in the are adequate for complete-arch implant-supported fixed dental prostheses is unclear. success of the treatment, as Purpose. The purpose of this in vitro study was to evaluate the trueness of 10 different dental transferring the intraoral posiintraoral scanners. tional and angular data of the Material and methods. Six implant analogs were installed, and an edentulous mandibular model implants to the gypsum cast composed of scannable Type 4 gypsum was scanned with 10 different intraoral scanners (3D accurately is essential. The Progress, Omnicam, Bluecam, Apollo DI, Planscan, E4D Tech, TRIOS MonoColor Cart, TRIOS Color passive fit of the prosthesis Cart, TRIOS Color Pod, Lythos), 10 times each after the scan body was placed on the implant depends on the impression abutments. The data obtained were then converted into standard tessellation language format. 1-4 step. For the control group, the gypsum model was scanned with an industrial scanner (ATOS Core Computer-aided design and 80). For trueness, the dental and industrial scanning data packs were analyzed with 3D comparison software. Statistical analyses were performed by using the Kruskal-Wallis and computer-aided manufacturing Mann-Whitney U tests. (CAD-CAM) software and hardware have now made the Results. When ranked according to their surface superimposition values, the Color POD, Omnicam, planning, design, and manuApollo DI, Color Cart, MonoColor Cart, and Bluecam scanners were found within the range of 31 to 45 mm. This group was followed by E4D, 3D Progress, Lythos, and Planscan, which were found facture of restorations possible within the range of 82 to 344 mm according to the same criteria. in a much shorter time. Nevertheless, CAD-CAM prosthetic Conclusions. Some of the digital scanners had the necessary performance for the fabrication of dentistry often still depends complete-arch implant-supported fixed dental prostheses. However, the possibility of data loss producing artifacts should be considered. (J Prosthet Dent 2020;-:---) on obtaining a definitive cast from conventional impression procedures. The scanning of these casts with extraoral CAD-CAM systems have been used reliably to scanners and transferring them to the digital platform fabricate tooth-supported or implant-supported fixed constitutes the first step of the CAD-CAM process. dental prostheses of up to 3 units.7 Scanning larger areas However, factors including errors from conventional increases the errors that result from merging multiple impressions and casts, the need for cast storage, and single images, causing image distortion and reducing patient discomfort during impression making are disadaccuracy.8 Although intraoral scanners are typically used 5-7 vantages of scanning conventional casts. for smaller areas (fewer than 3 or 4 units),9,10 studies
The present work was supported by the Research Fund of Istanbul University. Project No. 41219. a Assistant Professor, Department of Prosthodontics, Faculty of Dentistry, Trakya University, Edirne, Turkey. b Professor, Department of Prosthodontics, Faculty of Dentistry, Trakya University, Edirne, Turkey. c Professor, Department of Prosthodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey. d Researcher, Department of Periodontology, Faculty of Health, School of Dentistry, Witten/Herdecke University, Witten, Germany. e Professor, Department of Prosthodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey.
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Clinical Implications Selecting the right scanner is essential for the fabrication of implant-supported fixed dental prostheses. However, to achieve a more accurate scanning performance without any data loss or artifacts, reflections from the necks of the implants must be eliminated, even when scan bodies are used.
have evaluated complete-arch scanning.11-17 However, the trueness specifications of the existing systems and accordingly, the marginal adaptation and passive fitting features of the restorations fabricated with these systems require further research.8,9,18 Accuracy, trueness, and precision terms are described in ISO 5725-1.19 According to this, trueness is described as the closeness of agreement between the arithmetic mean of a measured subject and a known or true value. Precision is described as the closeness of agreement between test results. Test results that justify both trueness and precision are regarded as accurate. Almost all studies have used this definition.12,20-25 In many studies, best-fit algorithm was chosen as the superimposition method of evaluating trueness and precision.8,9,15,16,26,27 The reference scanner used in the present study has been used as the reference scanner in other similar studies.28-30 With a stereoscopic camera system included, the industrial optic scanner (ATOS Core-80; GOM GmbH) is a device that is able to achieve high resolution and high density scanning performance. This device combines 2 separate cameras with a projector that uses a structured light projection centered in the middle. Additionally, the device uses the “Innovative Triple Scan” technology and narrow band blue light as the source of light. The purpose of this in vitro study was to evaluate the general deviation data of the virtual casts obtained from 10 different intraoral scanners by superimposing each of them with the surface of the virtual cast obtained from the reference scanner. The null hypothesis was that all the scanners would show comparable negligible deviations and that no difference would be found in their deviation data. MATERIAL AND METHODS A complete-arch mandibular model (KaVo Basic Study Model; KaVo Dental GmbH) was used as the reference model. The teeth on the model were removed, and an impression was made with a stock tray and polyvinyl siloxane (Affinis Putty Heavy Body; Coltène) impression material. The impression was poured in a Type IV dental stone designed for scanning (GC Fujirock EP OptiXscan; THE JOURNAL OF PROSTHETIC DENTISTRY
Figure 1. Master model.
GC Corp). This was followed by the placement of the dental implant analogs (Straumann 4.1 mm Bone Level; Institut Straumann AG) in the left and right canine, first premolar, and first molar positions with the help of a parallelometer (Paraflex; BEGO GmbH), and the gaps between the extraction sockets and the dental implant analogs were filled with the same dental stone. Abutments (Ti-Base; Dentsply Sirona) were hand tightened to the analogs, and scan bodies were placed on the abutments to proceed to the scanning phase (Fig. 1). An industrial optical scanner (ATOS Core-80; GOM GmbH) was used as the reference scanner. Fourteen reference point markers (Reference Point Markers; GOM GmbH), which were identifiable for both the scanning device and the software, were attached to the cast. Five different scans were conducted on the same cast to ensure the trueness and the precision of the industrial scanner. The scanning procedures in this study were all carried out in a vibration-free environment by using a tripod or a special measurement stand. The comparison made to ensure the internal consistency of the reference scanner found that the deviation value of the device was 1.8 mm, which found a consistency rate of 99%. For the experimental groups, the dental stone cast was scanned 10 times with each intraoral scanner, the 3D Progress (MHT S.p.A. & MHT Optic Research AG), Omnicam (Dentsply Sirona), Bluecam (Dentsply Sirona), Apollo DI (Dentsply Sirona), E4D (E4D Technologies), Planscan (Planmeca E4D Technologies), TRIOS MonoColor CART (3Shape A/S), TRIOS Color CART (3Shape A/S), TRIOS Color POD (3Shape A/S), and Lythos (Ormco Corp) (n=10). The output data files of 3D Progress, Planscan, and Lythos were generated directly as standard tessellation language (STL) files. The output data files of Omnicam, Bluecam, and Apollo DI were converted to STL format with Cerec inLab SW4 software (Dentsply Sirona), and the output data files of the TRIOS group were converted with Rhinoceros software (McNeel & Associates) with a plug-in Bilmenoglu et al
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Table 1. Converting extensions Intraoral Scanners
Output Data Extension
3D Progress (ZFX)
.stl
Scan Software
Converting Software-1
Converting Software-2
-
-
3D MHT
Converted Data Extension .stl
Omnicam
.con
Cerec SW4
Cerec Connect SW4
Cerec inLab SW4
.stl
Bluecam
.con
Cerec SW4
Cerec Connect SW4
Cerec inLab SW4
.stl
Apollo DI
.csar
Apollo DI
-
Cerec inLab SW4
.stl
Planscan
.stl
Romexis 3.6.0.R
-
-
.stl
E4D Tech
.d4d
Design Center 2.0.0.19
Romexis 3.6.0.R
-
.stl
Mono Color CART
.dcm
3Shape TRIOS
3Shape Dental Manager
Rhinoceros 5.0 + Dental Shaper
.stl
Color CART
.dcm
3Shape TRIOS
3Shape Dental Manager
Rhinoceros 5.0 + Dental Shaper
.stl
Color POD
.dcm
3Shape TRIOS
3Shape Dental Manager
Rhinoceros 5.0 + Dental Shaper
.stl
Lythos
.stl
Ormco 1.9.10398
-
-
.stl
Figure 2. Selection of implant areas on virtual cast.
Figure 3. Colormap representation of deviations.
(Dental Shaper; CIM System). The output data file of E4D scanner was converted into STL format with Romexis software (Planmeca E4D Technologies) (Table 1). To specify the surface deviation, a total of 100 virtual 3D casts, which were derived from 10 scans made with each of the 10 scanners involved in the experimental group, were superimposed with 1 of the 5 scans (reference model) performed with the reference scanner (trueness). To test the precision of the reference scanner, the chosen reference model was also superimposed with each of the other 4 scans of the same group. Therefore, 104 individual superimpositions were carried out, 100 of which belonged to the experimental model, and the remaining 4 belonged to the control group model. The superimposition procedures were carried out with software (ATOS Professional v7.5 SR2; GOM GmbH) in accordance with the best-fit algorithm method. Before superimposing the models, the areas where the 6 implants had been placed on the 3D models obtained with the intraoral scanners of the experimental group were selected one by one, and the remaining areas were deleted and not included in the scanning procedure (Figs. 2, 3). Statistical analysis was performed with software (IBM SPSS Statistics, v22.0; IBM Corp). The normality of data distribution was tested with the Shapiro-Wilk test. The
Kruskal-Wallis Test and the Mann-Whitney U Test were used to compare the parameters that did not exhibit normal distribution (a=.05).
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RESULTS Reference scanner precision values for 4 superimpositions were calculated as 1.8 mm, 1.7 mm, 1.9 mm, and 1.9 mm. The superimposition deviation values of the tested intraoral scanners are presented in Table 2. A statistically significant amount of differentiation was found between the deviation values obtained through the surface superimposition of the scanner-generated virtual models with the reference model (P<.05) (Table 2 and Fig. 4). The deviation that emerged from the surface superimposition involving the Atos Master scanner was found to be significantly lower than that of the other scanners (P<.05). DISCUSSION The null hypothesis that all the scanners would show comparable negligible deviations and that no difference would be between their deviation data was rejected. Although some of the tested scanners found similar deviations (Table 2 and Fig. 4), none of them can be
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Table 2. Differences in trueness of scanners Values of Differences Trueness (mm), Mean
SD
Atos Master
1.8
±0.1
1.8
TRIOS Color Pod
30.9
±9.7
28.7
Omnicam
32.1
±7.3
31.7
Apollo
37.7
±8.2
34.5
TRIOS Color Card
40.3
±19.7
34.0
TRIOS Mono Color
43
±14.8
40.0
44.8
±13.9
43.5
E4D
82.3
±11.3
81.7
3D Progress
102.5
±21.4
97.5
Lythos
112.7
±62.8
121.1
344.7
±65.9
354.3
Scanner
Bluecam
Planscan P
Median
<.001**
SD, Standard deviation. Kruskal-Wallis Test ** P<.001.
450 TRIOS Color POD 400 350
Trueness (µm)
300
Omnicam Apollo DI TRIOS Color CARD TRIOS Mono Color CARD Bluecam
250 200 150
E4D D4D Tech ZFX Lythos PlanScan
100 50 0 Figure 4. Deviation data of tested scanners.
regarded as negligible, and all scanners found significantly higher deviations as compared with the reference model. The left and right canine, first premolar, and first molar areas are representative implant locations for a complete-arch fixed restoration, and to avoid the challenges of scanning 2 adjacently placed implants, the dental implant analogs were placed at these locations. A scannable Type 4 dental stone was used to avoid the effects of powdering on digital scanning procedures,26 and the surface was not abraded. According to the manufacturer, the setting expansion of this dental stone was less than 0.09% within 2 hours, and the scans were performed a few days after the dental stone cast was prepared. During this period, the cast was stored in a
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protective box and at a constant room temperature. However, the dental stone cast was not rescanned at the end of the study, and whether the scan bodies had been displaced was not determined. These were limitations of the study. Software (ATOS Professional V7.5 SR2; GOM GmbH) was used for superimposition procedures, and the best-fit algorithm was chosen as the superimposition method, as used in other studies.8,9,26,27 In the best-fit algorithm method, the relevant computer software superimposes the casts both from the control group and the experiment group with the maximum number of overlapping points and presents the points that do not overlap as the points of deviation (Fig. 5). To exclude the other overlapping points, the areas where the 6 implants
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Figure 5. Superimposing.
placed on the 3D model of the experimental group were selected one by one, and the remaining areas were deleted. In addition, soft tissue was eliminated by individual selection of implants. Not replicating the gingiva in the study model is a limitation of this study, but the lack of gingiva facilitated the scanning. The reference model used in this study was composed of scannable Type 4 dental stone that could be scanned without powder even in systems that specified powdering. However, powder-free trials made with the Apollo DI scanner resulted in excessive data loss because of reflection. Therefore, the powder (Apollo DI Speed Spray; Dentsply Sirona), which was suggested by the manufacturer, was used in accordance with their instructions. Optical artifacts, distortion of captured images, and missing data have been reported with digital scanners.11 The 10 virtual models obtained from Apollo DI were forwarded to other software (Cerec inLab SW4; Dentsply Sirona) for data conversion after being monitored on the screen and confirmed for accuracy after the scanning process. However, after the data format conversion, one of the virtual casts was detected to be too deformed for superimposing. Similarly, after the scanning carried out by E4D, one of the virtual casts was also not found sufficiently clear to provide data for the study. This outcome is thought to have occurred during the data transfer procedure and/or while the format of the visual file was being converted. Therefore, the measurement and statistical analysis procedures were carried out by using Apollo and E4D based on 9 different scanning instances instead of 10. After the format conversion process, 1 virtual cast from the Apollo DI scanner and 3 virtual casts from the TRIOS Color CART scanner did not have the implant in the unilateral molar areas (Fig. 6). Opaque scan bodies were placed on the titanium abutments during the scanning procedure. Nevertheless, the polished titanium surface on the neck of the implant (between the gypsum
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Figure 6. Minor deformation on TRIOS Color Cart group.
Figure 7. Polished titanium surface.
and the scan body) remains uncovered (Fig. 7). In spite of powdering, it was impossible to prevent the reflections from these areas during scanning. Because no scanning data were generated for the areas where reflections occurred, it seems that during the generation, compilation, and transfer of the remaining data and/or during the format conversion process, the software used did not regard the existing implant data as a part of the virtual cast and instead considered it excessive data and consequently deleted it. In the present study, similar to previous studies,8,18,20 the amount of deviation only on implant sections was found to be 44.8 ±13.9 mm for Bluecam. However, the ZFX IntraScan, which used the same infrastructure as the 3D Progress, achieved accuracy values of 102.5±21.4 mm.11 Additionally, the implants in the present study were positioned parallel to each other at the crestal level.21 All of the scanning procedures were carried out by the author CB without previous experience in digital scanning procedures by using the methods specified by the manufacturers.21 In-group scanning procedures were
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carried out on the same day at 5-minute to 10-minute intervals in order to allow the scanners to cool down, while the scanning procedures of different groups were performed on different days. In spite of the fact that the 3 different casts of the TRIOS group and by using the same camera technology obtained results in the same range, the portable device was able to produce better scanning sensitivity, which is probably because, unlike the CART models, the portable model was connected to a different computer with a better central processing unit, random access memory, and graphics processing unit. Future studies should be conducted on the clinical use of these devices. CONCLUSIONS Base on the findings of this in vitro study, the following conclusions were drawn: 1. TRIOS devices, Omnicam, Apollo DI, and Bluecam are suitable for implant-supported complete-arch fixed dental prostheses. 2. Data loss because of artifacts, reflections, and the inability to merge the data must be considered. 3. Even when scan bodies are used, reflections from the neck of implants can affect scanning accuracy. REFERENCES 1. Lorenzoni M, Pertl C, Penkner K, Polansky R, Sedaj B, Wegscheider WA. Comparison of the transfer precision of three different impression materials in combination with transfer caps for the Frialit-2 system. J Oral Rehabil 2000;27:629-38. 2. Phillips K, Nicholls J, Rubenstein J. The accuracy of three implant impression techniques: a three - dimensional analysis. Int J Oral Maxillofac Implants 1994;9:533-40. 3. Skalak R. Biomechanical considerations in osseointegrated prostheses. J Prosthet Dent 1983;49:843-8. 4. Tan KB, Rubenstein JE, Nicholls JI, Yuodelis RA. Three-dimensional analysis of the casting accuracy of one-piece, osseointegrated implant-retained prostheses. Int J Prosthodont 1993;6:346-63. 5. Chen SY, Liang WM, Chen FN. Factors affecting the accuracy of elastometric impression materials. J Dent 2004;32:603-9. 6. Nissan J, Laufer BZ, Brosh T, Assif D. Accuracy of three polyvinyl siloxane putty-wash impression techniques. J Prosthet Dent 2000;83:161-5. 7. Beuer F, Naumann M, Gernet W, Sorensen JA. Precision of fit: zirconia threeunit fixed dental prostheses. Clin Oral Investig 2009;13:343-9. 8. Ender A, Mehl A. Accuracy of complete-arch dental impressions: a new method of measuring trueness and precision. J Prosthet Dent 2013;109: 121-8. 9. Luthardt RG, Loos R, Quaas S. Accuracy of intraoral data acquisition in comparison to the conventional impression. Int J Comput Dent 2005;8:283-94. 10. Almeida e Silva JS, Erdelt K, Edelhoff D, Araujo E, Stimmelmayr M, Vieira LC, et al. Marginal and internal fit of four-unit zirconia fixed dental prostheses based on digital and conventional impression techniques. Clin Oral Investig 2014;18:515-23. 11. Patzelt SB, Emmanouilidi A, Stampf S, Strub JR, Att W. Accuracy of full-arch scans using intraoral scanners. Clin Oral Investig 2014;18:1687-94.
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12. Imburgia M, Logozzo S, Hauschild U, Veronesi G, Mangano C, Mangano FG. Accuracy of four intraoral scanners in oral implantology: a comparative in vitro study. BMC Oral Health 2017;17:92105. 13. Braian M, Wennerberg A. Trueness and precision of 5 intraoral scanners for scanning edentulous and dentate complete-arch mandibular casts: A comparative in vitro study. J Prosthet Dent 2019;122:129-36. 14. Di Fiore A, Meneghello R, Graiff L, Savio G, Vigolo P, Monaco C, et al. Full arch digital scanning systems performances for implant-supported fixed dental prostheses: a comparative study of 8 intraoral scanners. J Prosthodont Res 2019;63:396-403. 15. Osnes CA, Wu JH, Venezia P, Ferrari M, Keeling AJ. Full arch precision of six intraoral scanners in vitro. J Prosthodont Res 2019. doi: 10.1016/j.jpor.2019. 05.005. [Epub ahead of print]. 16. Mangano FG, Hauschild U, Veronesi G, Imburgia M, Mangano C, Admakin O. Trueness and precision of 5 intraoral scanners in the impressions of single and multiple implants: a comparative in vitro study. BMC Oral Health 2019;19:101-15. 17. Keul C, Guth JF. Accuracy of full-arch digital impressions: an in vitro and in vivo comparison. Clin Oral Investig 2019. doi: 10.1007/s00784-019-029652. [Epub ahead of print]. 18. Ender A, Mehl A. Full arch scans: conventional versus digital impression an in-vitro study. Int J Comput Dent 2011;14:11-21. 19. International Organization of Standardization. ISO 5725-1. Accuracy (trueness and precision) of measurement methods and results. Part 1: General principles and definitions. Geneva: ISO; 1994. Available at: https://www.iso. org/obp/ui/#iso:std:iso:5725:-1:ed-1:v1:en. 20. van der Meer WJ, Andriessen FS, Wismeijer D, Ren Y. Application of intraoral dental scanners in the digital workflow of implantology. PLoS One 2012;7:e43312. 21. Gimenez B, Ozcan M, Martinez-Rus F, Pradies G. Accuracy of a digital impression system based on active wavefront sampling technology for implants considering operator experience, implant angulation, and depth. Clin Implant Dent Relat Res 2015;17:54-64. 22. Abduo J, Elseyoufi M. Accuracy of intraoral scanners: a systematic review of influencing factors. Eur J Prosthodont Restor Dent 2018;26: 101-21. 23. Mangano FG, Veronesi G, Hauschild U, Mijiritsky E, Mangano C. Trueness and precision of four intraoral scanners in Oral Implantology: a comparative in vitro study. PLoS One 2016;11:e0163107. 24. Medina-Sotomayor P, Pascual MA, Camps AI. Accuracy of four digital scanners according to scanning strategy in complete-arch impressions. PLoS One 2018;13:e0202916. 25. Guth JF, Runkel C, Beuer F, Stimmelmayr M, Edelhoff D, Keul C. Accuracy of five intraoral scanners compared to indirect digitalization. Clin Oral Investig 2017;21:1445-55. 26. Mehl A, Ender A, Mormann W, Attin T. Accuracy testing of a new intraoral 3D camera. Int J Comput Dent 2009;12:11-28. 27. Steinhauser-Andresen S, Detterbeck A, Funk C, Krumm M, Kasperl S, Holst A, et al. Pilot study on accuracy and dimensional stability of impression materials using industrial CT technology. J Orofac Orthop 2011;72:111-24. 28. Nedelcu RG, Persson AS. Scanning accuracy and precision in 4 intraoral scanners: an in vitro comparison based on 3-dimensional analysis. J Prosthet Dent 2014;112:1461-71. 29. Ongul D, Gokcen-Rohlig B, Sermet B, Keskin H. A comparative analysis of the accuracy of different direct impression techniques for multiple implants. Aust Dent J 2012;57:184-9. 30. Trifkovic B, Budak I, Todorovic A, Vukelic D, Lazic V, Puskar T. Comparative analysis on measuring performances of dental intraoral and extraoral optical 3D digitization systems. Measurement 2014;47:45-53. Corresponding author: Dr Caglar Bilmenoglu Trakya Üniversitesi Dis¸ Hekimli g i Fakültesi Balkan Yerles¸kesi Merkez/Edirne TURKEY Email: [email protected]; [email protected] Copyright © 2019 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2019.11.017
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In vitro comparison of trueness of 10 intraoral scanners for implant-supported complete-arch fixed dental prostheses Caglar Bilmenoglu, DDS, PhD,a Altug Cilingir, DDS, PhD,b Onur Geckili, DDS, PhD,c Hakan Bilhan, DDS, PhD,d and Tayfun Bilgin, DDS, PhDe For implant-supported fixed ABSTRACT dental prostheses, the impresStatement of problem. Digital scanning systems have become popular, but whether these systems sion plays a direct role in the are adequate for complete-arch implant-supported fixed dental prostheses is unclear. success of the treatment, as Purpose. The purpose of this in vitro study was to evaluate the trueness of 10 different dental transferring the intraoral posiintraoral scanners. tional and angular data of the Material and methods. Six implant analogs were installed, and an edentulous mandibular model implants to the gypsum cast composed of scannable Type 4 gypsum was scanned with 10 different intraoral scanners (3D accurately is essential. The Progress, Omnicam, Bluecam, Apollo DI, Planscan, E4D Tech, TRIOS MonoColor Cart, TRIOS Color passive fit of the prosthesis Cart, TRIOS Color Pod, Lythos), 10 times each after the scan body was placed on the implant depends on the impression abutments. The data obtained were then converted into standard tessellation language format. 1-4 step. For the control group, the gypsum model was scanned with an industrial scanner (ATOS Core Computer-aided design and 80). For trueness, the dental and industrial scanning data packs were analyzed with 3D comparison software. Statistical analyses were performed by using the Kruskal-Wallis and computer-aided manufacturing Mann-Whitney U tests. (CAD-CAM) software and hardware have now made the Results. When ranked according to their surface superimposition values, the Color POD, Omnicam, planning, design, and manuApollo DI, Color Cart, MonoColor Cart, and Bluecam scanners were found within the range of 31 to 45 mm. This group was followed by E4D, 3D Progress, Lythos, and Planscan, which were found facture of restorations possible within the range of 82 to 344 mm according to the same criteria. in a much shorter time. Nevertheless, CAD-CAM prosthetic Conclusions. Some of the digital scanners had the necessary performance for the fabrication of dentistry often still depends complete-arch implant-supported fixed dental prostheses. However, the possibility of data loss producing artifacts should be considered. (J Prosthet Dent 2020;-:---) on obtaining a definitive cast from conventional impression procedures. The scanning of these casts with extraoral CAD-CAM systems have been used reliably to scanners and transferring them to the digital platform fabricate tooth-supported or implant-supported fixed constitutes the first step of the CAD-CAM process. dental prostheses of up to 3 units.7 Scanning larger areas However, factors including errors from conventional increases the errors that result from merging multiple impressions and casts, the need for cast storage, and single images, causing image distortion and reducing patient discomfort during impression making are disadaccuracy.8 Although intraoral scanners are typically used 5-7 vantages of scanning conventional casts. for smaller areas (fewer than 3 or 4 units),9,10 studies
The present work was supported by the Research Fund of Istanbul University. Project No. 41219. a Assistant Professor, Department of Prosthodontics, Faculty of Dentistry, Trakya University, Edirne, Turkey. b Professor, Department of Prosthodontics, Faculty of Dentistry, Trakya University, Edirne, Turkey. c Professor, Department of Prosthodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey. d Researcher, Department of Periodontology, Faculty of Health, School of Dentistry, Witten/Herdecke University, Witten, Germany. e Professor, Department of Prosthodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey.
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Clinical Implications Selecting the right scanner is essential for the fabrication of implant-supported fixed dental prostheses. However, to achieve a more accurate scanning performance without any data loss or artifacts, reflections from the necks of the implants must be eliminated, even when scan bodies are used.
have evaluated complete-arch scanning.11-17 However, the trueness specifications of the existing systems and accordingly, the marginal adaptation and passive fitting features of the restorations fabricated with these systems require further research.8,9,18 Accuracy, trueness, and precision terms are described in ISO 5725-1.19 According to this, trueness is described as the closeness of agreement between the arithmetic mean of a measured subject and a known or true value. Precision is described as the closeness of agreement between test results. Test results that justify both trueness and precision are regarded as accurate. Almost all studies have used this definition.12,20-25 In many studies, best-fit algorithm was chosen as the superimposition method of evaluating trueness and precision.8,9,15,16,26,27 The reference scanner used in the present study has been used as the reference scanner in other similar studies.28-30 With a stereoscopic camera system included, the industrial optic scanner (ATOS Core-80; GOM GmbH) is a device that is able to achieve high resolution and high density scanning performance. This device combines 2 separate cameras with a projector that uses a structured light projection centered in the middle. Additionally, the device uses the “Innovative Triple Scan” technology and narrow band blue light as the source of light. The purpose of this in vitro study was to evaluate the general deviation data of the virtual casts obtained from 10 different intraoral scanners by superimposing each of them with the surface of the virtual cast obtained from the reference scanner. The null hypothesis was that all the scanners would show comparable negligible deviations and that no difference would be found in their deviation data. MATERIAL AND METHODS A complete-arch mandibular model (KaVo Basic Study Model; KaVo Dental GmbH) was used as the reference model. The teeth on the model were removed, and an impression was made with a stock tray and polyvinyl siloxane (Affinis Putty Heavy Body; Coltène) impression material. The impression was poured in a Type IV dental stone designed for scanning (GC Fujirock EP OptiXscan; THE JOURNAL OF PROSTHETIC DENTISTRY
Figure 1. Master model.
GC Corp). This was followed by the placement of the dental implant analogs (Straumann 4.1 mm Bone Level; Institut Straumann AG) in the left and right canine, first premolar, and first molar positions with the help of a parallelometer (Paraflex; BEGO GmbH), and the gaps between the extraction sockets and the dental implant analogs were filled with the same dental stone. Abutments (Ti-Base; Dentsply Sirona) were hand tightened to the analogs, and scan bodies were placed on the abutments to proceed to the scanning phase (Fig. 1). An industrial optical scanner (ATOS Core-80; GOM GmbH) was used as the reference scanner. Fourteen reference point markers (Reference Point Markers; GOM GmbH), which were identifiable for both the scanning device and the software, were attached to the cast. Five different scans were conducted on the same cast to ensure the trueness and the precision of the industrial scanner. The scanning procedures in this study were all carried out in a vibration-free environment by using a tripod or a special measurement stand. The comparison made to ensure the internal consistency of the reference scanner found that the deviation value of the device was 1.8 mm, which found a consistency rate of 99%. For the experimental groups, the dental stone cast was scanned 10 times with each intraoral scanner, the 3D Progress (MHT S.p.A. & MHT Optic Research AG), Omnicam (Dentsply Sirona), Bluecam (Dentsply Sirona), Apollo DI (Dentsply Sirona), E4D (E4D Technologies), Planscan (Planmeca E4D Technologies), TRIOS MonoColor CART (3Shape A/S), TRIOS Color CART (3Shape A/S), TRIOS Color POD (3Shape A/S), and Lythos (Ormco Corp) (n=10). The output data files of 3D Progress, Planscan, and Lythos were generated directly as standard tessellation language (STL) files. The output data files of Omnicam, Bluecam, and Apollo DI were converted to STL format with Cerec inLab SW4 software (Dentsply Sirona), and the output data files of the TRIOS group were converted with Rhinoceros software (McNeel & Associates) with a plug-in Bilmenoglu et al
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Table 1. Converting extensions Intraoral Scanners
Output Data Extension
3D Progress (ZFX)
.stl
Scan Software
Converting Software-1
Converting Software-2
-
-
3D MHT
Converted Data Extension .stl
Omnicam
.con
Cerec SW4
Cerec Connect SW4
Cerec inLab SW4
.stl
Bluecam
.con
Cerec SW4
Cerec Connect SW4
Cerec inLab SW4
.stl
Apollo DI
.csar
Apollo DI
-
Cerec inLab SW4
.stl
Planscan
.stl
Romexis 3.6.0.R
-
-
.stl
E4D Tech
.d4d
Design Center 2.0.0.19
Romexis 3.6.0.R
-
.stl
Mono Color CART
.dcm
3Shape TRIOS
3Shape Dental Manager
Rhinoceros 5.0 + Dental Shaper
.stl
Color CART
.dcm
3Shape TRIOS
3Shape Dental Manager
Rhinoceros 5.0 + Dental Shaper
.stl
Color POD
.dcm
3Shape TRIOS
3Shape Dental Manager
Rhinoceros 5.0 + Dental Shaper
.stl
Lythos
.stl
Ormco 1.9.10398
-
-
.stl
Figure 2. Selection of implant areas on virtual cast.
Figure 3. Colormap representation of deviations.
(Dental Shaper; CIM System). The output data file of E4D scanner was converted into STL format with Romexis software (Planmeca E4D Technologies) (Table 1). To specify the surface deviation, a total of 100 virtual 3D casts, which were derived from 10 scans made with each of the 10 scanners involved in the experimental group, were superimposed with 1 of the 5 scans (reference model) performed with the reference scanner (trueness). To test the precision of the reference scanner, the chosen reference model was also superimposed with each of the other 4 scans of the same group. Therefore, 104 individual superimpositions were carried out, 100 of which belonged to the experimental model, and the remaining 4 belonged to the control group model. The superimposition procedures were carried out with software (ATOS Professional v7.5 SR2; GOM GmbH) in accordance with the best-fit algorithm method. Before superimposing the models, the areas where the 6 implants had been placed on the 3D models obtained with the intraoral scanners of the experimental group were selected one by one, and the remaining areas were deleted and not included in the scanning procedure (Figs. 2, 3). Statistical analysis was performed with software (IBM SPSS Statistics, v22.0; IBM Corp). The normality of data distribution was tested with the Shapiro-Wilk test. The
Kruskal-Wallis Test and the Mann-Whitney U Test were used to compare the parameters that did not exhibit normal distribution (a=.05).
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RESULTS Reference scanner precision values for 4 superimpositions were calculated as 1.8 mm, 1.7 mm, 1.9 mm, and 1.9 mm. The superimposition deviation values of the tested intraoral scanners are presented in Table 2. A statistically significant amount of differentiation was found between the deviation values obtained through the surface superimposition of the scanner-generated virtual models with the reference model (P<.05) (Table 2 and Fig. 4). The deviation that emerged from the surface superimposition involving the Atos Master scanner was found to be significantly lower than that of the other scanners (P<.05). DISCUSSION The null hypothesis that all the scanners would show comparable negligible deviations and that no difference would be between their deviation data was rejected. Although some of the tested scanners found similar deviations (Table 2 and Fig. 4), none of them can be
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Table 2. Differences in trueness of scanners Values of Differences Trueness (mm), Mean
SD
Atos Master
1.8
±0.1
1.8
TRIOS Color Pod
30.9
±9.7
28.7
Omnicam
32.1
±7.3
31.7
Apollo
37.7
±8.2
34.5
TRIOS Color Card
40.3
±19.7
34.0
TRIOS Mono Color
43
±14.8
40.0
44.8
±13.9
43.5
E4D
82.3
±11.3
81.7
3D Progress
102.5
±21.4
97.5
Lythos
112.7
±62.8
121.1
344.7
±65.9
354.3
Scanner
Bluecam
Planscan P
Median
<.001**
SD, Standard deviation. Kruskal-Wallis Test ** P<.001.
450 TRIOS Color POD 400 350
Trueness (µm)
300
Omnicam Apollo DI TRIOS Color CARD TRIOS Mono Color CARD Bluecam
250 200 150
E4D D4D Tech ZFX Lythos PlanScan
100 50 0 Figure 4. Deviation data of tested scanners.
regarded as negligible, and all scanners found significantly higher deviations as compared with the reference model. The left and right canine, first premolar, and first molar areas are representative implant locations for a complete-arch fixed restoration, and to avoid the challenges of scanning 2 adjacently placed implants, the dental implant analogs were placed at these locations. A scannable Type 4 dental stone was used to avoid the effects of powdering on digital scanning procedures,26 and the surface was not abraded. According to the manufacturer, the setting expansion of this dental stone was less than 0.09% within 2 hours, and the scans were performed a few days after the dental stone cast was prepared. During this period, the cast was stored in a
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protective box and at a constant room temperature. However, the dental stone cast was not rescanned at the end of the study, and whether the scan bodies had been displaced was not determined. These were limitations of the study. Software (ATOS Professional V7.5 SR2; GOM GmbH) was used for superimposition procedures, and the best-fit algorithm was chosen as the superimposition method, as used in other studies.8,9,26,27 In the best-fit algorithm method, the relevant computer software superimposes the casts both from the control group and the experiment group with the maximum number of overlapping points and presents the points that do not overlap as the points of deviation (Fig. 5). To exclude the other overlapping points, the areas where the 6 implants
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Figure 5. Superimposing.
placed on the 3D model of the experimental group were selected one by one, and the remaining areas were deleted. In addition, soft tissue was eliminated by individual selection of implants. Not replicating the gingiva in the study model is a limitation of this study, but the lack of gingiva facilitated the scanning. The reference model used in this study was composed of scannable Type 4 dental stone that could be scanned without powder even in systems that specified powdering. However, powder-free trials made with the Apollo DI scanner resulted in excessive data loss because of reflection. Therefore, the powder (Apollo DI Speed Spray; Dentsply Sirona), which was suggested by the manufacturer, was used in accordance with their instructions. Optical artifacts, distortion of captured images, and missing data have been reported with digital scanners.11 The 10 virtual models obtained from Apollo DI were forwarded to other software (Cerec inLab SW4; Dentsply Sirona) for data conversion after being monitored on the screen and confirmed for accuracy after the scanning process. However, after the data format conversion, one of the virtual casts was detected to be too deformed for superimposing. Similarly, after the scanning carried out by E4D, one of the virtual casts was also not found sufficiently clear to provide data for the study. This outcome is thought to have occurred during the data transfer procedure and/or while the format of the visual file was being converted. Therefore, the measurement and statistical analysis procedures were carried out by using Apollo and E4D based on 9 different scanning instances instead of 10. After the format conversion process, 1 virtual cast from the Apollo DI scanner and 3 virtual casts from the TRIOS Color CART scanner did not have the implant in the unilateral molar areas (Fig. 6). Opaque scan bodies were placed on the titanium abutments during the scanning procedure. Nevertheless, the polished titanium surface on the neck of the implant (between the gypsum
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Figure 6. Minor deformation on TRIOS Color Cart group.
Figure 7. Polished titanium surface.
and the scan body) remains uncovered (Fig. 7). In spite of powdering, it was impossible to prevent the reflections from these areas during scanning. Because no scanning data were generated for the areas where reflections occurred, it seems that during the generation, compilation, and transfer of the remaining data and/or during the format conversion process, the software used did not regard the existing implant data as a part of the virtual cast and instead considered it excessive data and consequently deleted it. In the present study, similar to previous studies,8,18,20 the amount of deviation only on implant sections was found to be 44.8 ±13.9 mm for Bluecam. However, the ZFX IntraScan, which used the same infrastructure as the 3D Progress, achieved accuracy values of 102.5±21.4 mm.11 Additionally, the implants in the present study were positioned parallel to each other at the crestal level.21 All of the scanning procedures were carried out by the author CB without previous experience in digital scanning procedures by using the methods specified by the manufacturers.21 In-group scanning procedures were
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carried out on the same day at 5-minute to 10-minute intervals in order to allow the scanners to cool down, while the scanning procedures of different groups were performed on different days. In spite of the fact that the 3 different casts of the TRIOS group and by using the same camera technology obtained results in the same range, the portable device was able to produce better scanning sensitivity, which is probably because, unlike the CART models, the portable model was connected to a different computer with a better central processing unit, random access memory, and graphics processing unit. Future studies should be conducted on the clinical use of these devices. CONCLUSIONS Base on the findings of this in vitro study, the following conclusions were drawn: 1. TRIOS devices, Omnicam, Apollo DI, and Bluecam are suitable for implant-supported complete-arch fixed dental prostheses. 2. Data loss because of artifacts, reflections, and the inability to merge the data must be considered. 3. Even when scan bodies are used, reflections from the neck of implants can affect scanning accuracy. REFERENCES 1. Lorenzoni M, Pertl C, Penkner K, Polansky R, Sedaj B, Wegscheider WA. Comparison of the transfer precision of three different impression materials in combination with transfer caps for the Frialit-2 system. J Oral Rehabil 2000;27:629-38. 2. Phillips K, Nicholls J, Rubenstein J. The accuracy of three implant impression techniques: a three - dimensional analysis. Int J Oral Maxillofac Implants 1994;9:533-40. 3. Skalak R. Biomechanical considerations in osseointegrated prostheses. J Prosthet Dent 1983;49:843-8. 4. Tan KB, Rubenstein JE, Nicholls JI, Yuodelis RA. Three-dimensional analysis of the casting accuracy of one-piece, osseointegrated implant-retained prostheses. Int J Prosthodont 1993;6:346-63. 5. Chen SY, Liang WM, Chen FN. Factors affecting the accuracy of elastometric impression materials. J Dent 2004;32:603-9. 6. Nissan J, Laufer BZ, Brosh T, Assif D. Accuracy of three polyvinyl siloxane putty-wash impression techniques. J Prosthet Dent 2000;83:161-5. 7. Beuer F, Naumann M, Gernet W, Sorensen JA. Precision of fit: zirconia threeunit fixed dental prostheses. Clin Oral Investig 2009;13:343-9. 8. Ender A, Mehl A. Accuracy of complete-arch dental impressions: a new method of measuring trueness and precision. J Prosthet Dent 2013;109: 121-8. 9. Luthardt RG, Loos R, Quaas S. Accuracy of intraoral data acquisition in comparison to the conventional impression. Int J Comput Dent 2005;8:283-94. 10. Almeida e Silva JS, Erdelt K, Edelhoff D, Araujo E, Stimmelmayr M, Vieira LC, et al. Marginal and internal fit of four-unit zirconia fixed dental prostheses based on digital and conventional impression techniques. Clin Oral Investig 2014;18:515-23. 11. Patzelt SB, Emmanouilidi A, Stampf S, Strub JR, Att W. Accuracy of full-arch scans using intraoral scanners. Clin Oral Investig 2014;18:1687-94.
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12. Imburgia M, Logozzo S, Hauschild U, Veronesi G, Mangano C, Mangano FG. Accuracy of four intraoral scanners in oral implantology: a comparative in vitro study. BMC Oral Health 2017;17:92105. 13. Braian M, Wennerberg A. Trueness and precision of 5 intraoral scanners for scanning edentulous and dentate complete-arch mandibular casts: A comparative in vitro study. J Prosthet Dent 2019;122:129-36. 14. Di Fiore A, Meneghello R, Graiff L, Savio G, Vigolo P, Monaco C, et al. Full arch digital scanning systems performances for implant-supported fixed dental prostheses: a comparative study of 8 intraoral scanners. J Prosthodont Res 2019;63:396-403. 15. Osnes CA, Wu JH, Venezia P, Ferrari M, Keeling AJ. Full arch precision of six intraoral scanners in vitro. J Prosthodont Res 2019. doi: 10.1016/j.jpor.2019. 05.005. [Epub ahead of print]. 16. Mangano FG, Hauschild U, Veronesi G, Imburgia M, Mangano C, Admakin O. Trueness and precision of 5 intraoral scanners in the impressions of single and multiple implants: a comparative in vitro study. BMC Oral Health 2019;19:101-15. 17. Keul C, Guth JF. Accuracy of full-arch digital impressions: an in vitro and in vivo comparison. Clin Oral Investig 2019. doi: 10.1007/s00784-019-029652. [Epub ahead of print]. 18. Ender A, Mehl A. Full arch scans: conventional versus digital impression an in-vitro study. Int J Comput Dent 2011;14:11-21. 19. International Organization of Standardization. ISO 5725-1. Accuracy (trueness and precision) of measurement methods and results. Part 1: General principles and definitions. Geneva: ISO; 1994. Available at: https://www.iso. org/obp/ui/#iso:std:iso:5725:-1:ed-1:v1:en. 20. van der Meer WJ, Andriessen FS, Wismeijer D, Ren Y. Application of intraoral dental scanners in the digital workflow of implantology. PLoS One 2012;7:e43312. 21. Gimenez B, Ozcan M, Martinez-Rus F, Pradies G. Accuracy of a digital impression system based on active wavefront sampling technology for implants considering operator experience, implant angulation, and depth. Clin Implant Dent Relat Res 2015;17:54-64. 22. Abduo J, Elseyoufi M. Accuracy of intraoral scanners: a systematic review of influencing factors. Eur J Prosthodont Restor Dent 2018;26: 101-21. 23. Mangano FG, Veronesi G, Hauschild U, Mijiritsky E, Mangano C. Trueness and precision of four intraoral scanners in Oral Implantology: a comparative in vitro study. PLoS One 2016;11:e0163107. 24. Medina-Sotomayor P, Pascual MA, Camps AI. Accuracy of four digital scanners according to scanning strategy in complete-arch impressions. PLoS One 2018;13:e0202916. 25. Guth JF, Runkel C, Beuer F, Stimmelmayr M, Edelhoff D, Keul C. Accuracy of five intraoral scanners compared to indirect digitalization. Clin Oral Investig 2017;21:1445-55. 26. Mehl A, Ender A, Mormann W, Attin T. Accuracy testing of a new intraoral 3D camera. Int J Comput Dent 2009;12:11-28. 27. Steinhauser-Andresen S, Detterbeck A, Funk C, Krumm M, Kasperl S, Holst A, et al. Pilot study on accuracy and dimensional stability of impression materials using industrial CT technology. J Orofac Orthop 2011;72:111-24. 28. Nedelcu RG, Persson AS. Scanning accuracy and precision in 4 intraoral scanners: an in vitro comparison based on 3-dimensional analysis. J Prosthet Dent 2014;112:1461-71. 29. Ongul D, Gokcen-Rohlig B, Sermet B, Keskin H. A comparative analysis of the accuracy of different direct impression techniques for multiple implants. Aust Dent J 2012;57:184-9. 30. Trifkovic B, Budak I, Todorovic A, Vukelic D, Lazic V, Puskar T. Comparative analysis on measuring performances of dental intraoral and extraoral optical 3D digitization systems. Measurement 2014;47:45-53. Corresponding author: Dr Caglar Bilmenoglu Trakya Üniversitesi Dis¸ Hekimli g i Fakültesi Balkan Yerles¸kesi Merkez/Edirne TURKEY Email: [email protected]; [email protected] Copyright © 2019 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2019.11.017
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