- Email: [email protected]
Effect of coded healing abutment height and position on the trueness of digital intraoral implant scans
RESEARCH AND EDUCATION
Effect of coded healing abutment height and position on the trueness of digital intraoral implant scans Burcu Batak, DDS, PhD,a Burak Yilmaz, DDS, PhD,b Karnik Shah, BDS, MS,c Rajat Rathi, BDS,d Martin Schimmel, Dr med dent, MAS, PD,e and Lisa Lang, DDS, MS, MBAf One of the most critical steps in the long-term success of implant restorations is impression accuracy for a definitive cast on which the prosthesis will be fabricated.1 Impression accuracy is affected by implant position, angulation, and depth and in turn affects the fit of the implant-supported prosthesis.2,3 Because implants are functionally ankylosed, the implant-bone interface is not resilient, and, therefore, misfit can lead to mechanical and biological complications, including failure.4,5 Different impression techniques and materials have been used to obtain accurate definitive casts, ensuring an acceptable prosthesis. However, the accuracy of conventional impression techniques and the effect of tray type on impression accuracy are unclear.5-7 In addition, these
ABSTRACT Statement of problem. Information regarding the effect of the height and position of a coded healing abutment (CHA) on the trueness of intraoral digital scans is lacking. Purpose. The purpose of this in vitro study was to investigate the effect of the height and position of a scannable CHA on the trueness (distance and angular deviations) of intraoral digital scans. Material and methods. Scannable CHAs (BellaTek Encode Impression system; Zimmer Biomet Dental) were used in 2 different height pairs (3 mm and 8 mm) on 2 implants at mandibular left second and first molar positions. Each pair was scanned 10 times by using 1 intraoral scanner (TRIOS; 3Shape) by 1 operator to generate a total of 20 intraoral scan files. Master standard tessellation language (STL) files were created for both 3-mm and 8-mm CHA pairs by using a structured blue light scanner (COMET L3D 8M 150 Precision Structured Blue Light Scanner; ZEISS). These master STL files were imported into a software program (PolyWorks Inspector) and were used as the reference for the inspection. Scans obtained by using the intraoral scanner were aligned to the reference scan by using a best-fit alignment to measure the distance and angular deviations. Two-way repeated-measures ANOVA was used to analyze the data, and the Tukey-Kramer test was used to determine significant differences among groups (a=.05). Results. The CHA position had a significant effect on distance deviation (P<.001). However, no significant effect of CHA height on distance deviation was found. The interaction between CHA height and position had a significant effect on the angular deviation (P=.041). The 3-mm posterior CHA (P=.026) and 8-mm anterior CHA (P=.039) had significantly lower angular deviations than the 8-mm posterior CHA. Conclusions. The distance deviation of CHA was significantly influenced by position. CHAs in the anterior had lower distance deviations for both 3 mm and 8 mm. The effect of CHA height on distance deviation was found to be small and was affected by the location of the CHA. Height affected angular deviation depending on the position of the CHA. Both 3-mm posterior and 8-mm anterior CHAs showed lower angular deviations than the 8-mm posterior CHA. (J Prosthet Dent 2019;-:---)
a
Former Visiting Scholar, Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, Ohio; and Research Associate, Department of Prosthodontics, Faculty of Dentistry, Ankara University, Ankara, Turkey. b Professor, Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, Ohio. c Private practice, Austin, Texas. d Former Visiting Scholar, Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, Ohio. e Professor, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; and Professor, Divison of Gerodontology and Removable Prosthodontics, University of Geneva, Geneva, Switzerland. f Associate Professor, Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, Ohio.
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Clinical Implications Clinicians should be careful when selecting the height of a scannable coded healing abutment in situations where 2 implants are placed adjacent to each other in the mandibular molar region, as height may affect the trueness of the digital scan. The location of the implant may affect the trueness when coded healing abutments are used with the intraoral scanner used in this study.
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precision of intraoral scanners have been evaluated, most of the studies have tested scan bodies of a single size.11,13,19 The purpose of this in vitro study was to investigate the effect of the height and position of a scannable CHA on the trueness of intraoral digital scans. The null hypotheses were that the CHA height would not affect the trueness of digital intraoral implant scans and that the implant position would not affect the trueness of digital intraoral scans of implants. MATERIAL AND METHODS
techniques are somewhat difficult to perform, are operator sensitive and time-consuming, involve multiple steps, are uncomfortable for patients, and have the potential for errors at every phase.2-4,8 Advances in computer-aided design and computer-aided manufacturing (CAD-CAM) have allowed the fabrication of accurate implant-supported restorations by using an indirect digital workflow through laboratory scanning of the stone cast after making a definitive impression.9,10 A 2-piece coded healing abutment (CHA), which can be captured by using intraoral scanners and eliminates the need for impression copings,11-13 is distinguished by occlusal surface codes that convey information regarding the implant connection type and size, implant hexagon position, and healing abutment height.14,15 The digital scan file can be sent and stored electronically, eliminating physical space requirements and contributing to efficient digital record keeping, and can be used multiple times when needed.4,5,7 The effect of CHAs on treatment duration and clinical outcomes has been evaluated, comparing their accuracy with that of conventional impression techniques.11-21 In recent years, intraoral scan bodies (ISBs) have been marketed in different shapes and sizes and fabricated out of various materials.22 Some of the scan bodies need specific scanners and some can be used with multiple scanners, whose files may be processed by using different CAD-CAM systems.22 The geometry of ISBs varies from a spherical design to a cylindrical design with diverse intermediate forms, with heights ranging from 3 mm to 17 mm.23 All of them consist of an upper scan region, a middle body, and an apical portion known as the base that attaches to the implant.22,23 However, the requirements of the surface geometry and dimension of the implant scan body for an accurate transfer of the implant position to the virtual model have not been analyzed.22 The literature lacks information on the precision of capturing the dimensions of the scan bodies in regard to different surface geometries and dimensions.23,24 Moreover, although digital scans have been compared with conventional impressions, determining the accuracy of restorations generated from both, and the accuracy and THE JOURNAL OF PROSTHETIC DENTISTRY
A mandibular stereolithographic model with 2 embedded internal connection implants (4-mm diameter/3.4-mm platform × 10 mm in length, 3i T3 platform switched Certain Tapered Implant; Zimmer Biomet Dental) at the mandibular left second and first molar positions was used. CHAs (BellaTek Encode Impression system; Zimmer Biomet Dental) were used in 2 different height pairs on both implants (E1 3-4-3, 3 mm in height, and E2 8-4-3, 8 mm in height). Before scanning, titanium dioxide powder (3M High-Resolution Scanning Spray; 3M ESPE) was sprayed onto the surface of the mandibular stereolithographic model and CHAs for constant reflectivity as it was a clear model. Each pair was scanned 10 times by using 1 intraoral scanner (TRIOS; 3Shape) by 1 operator (R.R.) as per the manufacturer’s protocol to generate a total of 20 intraoral scan files (2 abutment heights, 10 scans per size, 1 scanner). The scanning procedure was performed in the same order as recommended by the manufacturer (occlusal and lingual surfaces followed by the buccal surface). The obtained 3D data were converted and recorded as standard tessellation language (STL) data. One master scan was obtained from each group by using an advanced blue light optical laboratory scanner (COMET L3D 8M 150 Precision Structured Blue Light Scanner; ZEISS) having measurement uncertainty certified to 12+0.03L mm (L is the length of the material scanned). These master scan files were obtained in STL format, and these STL files were imported into a software program (PolyWorks Inspector) and were used as the reference for the inspection. Data collected using the intraoral scanner were aligned to the reference by using a best-fit alignment. In the software (PolyWorks Inspector), a best-fit alignment is an automatic algorithm that iteratively translates and rotates the data group, or intraoral scans, to bring it as close as possible to the reference. With this alignment type, only the unchanged features of the STL files are used to help reduce any error that may ensue from the software using outlying data. For each master STL, a coordinate system was created and used throughout the entire inspection (Fig. 1). The Batak et al
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Figure 2. Anterior and posterior coded healing abutment. Figure 1. Coordinate system for master standard tessellation language file.
CHAs used for inspection were labeled as either the anterior or posterior CHA, and those same labels were used for every inspection (Fig. 2). Cylinders were fitted to each CHA, and using the cylinder axes, angular deviations were measured and reported as 3D-angle measurements. In this measurement method, the nominal axis (the axis of the cylinder created from the master STL) is considered to be at an angle of zero, and then the resultant angle between the data and reference axes is reported as the 3D angle. To determine the position of each CHA, circles were fitted to cross-sections at 2 locations of each CHA. The circle center points were used to report the positional deviations relative to the origin of the coordinate system. The cross-sections were created 0.5 mm from the top and 0.5 mm up from the bottom of each CHA (Fig. 3). Additionally, the cross-sections were made normal to the x-y plane. Therefore, there was no difference between the nominal and measured values for the z-direction. To measure the z displacement, a plane was created at the top of each CHA, and then a point was created at the intersection of that plane and axis of the CHA. The distance from that point to the base of the lower jaw mold was measured and reported as the z displacement. On each CHA, there were 2 planes at the top (Fig. 4). Planes were extracted from those surfaces, and then an average plane was created from those two. The angle between the averaged plane and the first plane was in the x-y plane and showed the difference in orientation of the CHAs compared with the master STL. Each distance was calculated from the reference in each of the 3 dimensions using the following formula: qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 3D Distance= Dx +Dy2 +Dz2
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Figure 3. Cross-sections 0.5 mm from top and bottom of each coded healing abutment.
Two-way repeated-measures ANOVA (MIXED procedure; SAS Proprietary Software v9.3; SAS Institute Inc) was used to analyze the data. Tukey-Kramer tests were used to resolve the interaction for the angular deviations. The between-subject factor was the CHA height, and the within-subject factor was the position. For the angular deviation measurements, the restricted maximum likelihood estimation method was used to eliminate the need for normality and equality of variances (a=.05). RESULTS Mean distance deviations and 95% confidence intervals between virtual models produced from scans (master scan by using laboratory scanner and 10 scans by using an intraoral scanner) are presented in Figure 5. Position had a significant effect on the distance deviation (P<.001). Anterior position showed lower distance deviations for both 3-mm and 8-mm CHAs. However, no significant effect of CHA height was found on the distance deviation (Table 1).
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Figure 4. A, Two planes at top of each coded healing abutment. B, Average plane created from these two.
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Table 1. Analysis of variance of distance deviations DF
SS
Mean Square
F
P
CHA
1
40906.324
40906.324
1.75
.204
Error
17
397790.203
23399.424
d
d
1
152839.277
152839.277
85.45
<.001
3D Distance Deviation (µm)
Source
500
Position
400 300
1
758.261
758.261
0.42
.524
Error (position)
17
30407.192
1788.658
d
d
CHA, coded healing abutment.
200 100 0
Position×CHA
Anterior
Posterior
Anterior
3mm
Posterior Position
8mm
Coded Healing Abutment
Figure 5. Mean distance deviations and 95% confidence intervals.
Mean angular deviations and 95% confidence intervals between virtual models produced from scans (master scan by using laboratory scanner and 10 scans by using an intraoral scanner) are presented in Figure 6. The interaction between CHA height and position had a significant effect on angular deviations (Table 2). According to the Tukey-Kramer test, the 3mm posterior CHA had significantly lower angular deviations than the 8-mm posterior CHA (P=.026). The 8-mm anterior CHA had significantly lower angular deviations than the 8-mm CHA in the posterior position (P=.039). DISCUSSION In terms of the trueness of the digital implant scans made in this study, the CHA position had a significant effect on the distance deviation. The interaction between the CHA height and position had a significant effect on the angular deviation. Therefore, the null hypotheses were rejected. THE JOURNAL OF PROSTHETIC DENTISTRY
An absolute passive fit has been stated to be impossible to attain, and different authors propose different acceptable levels of misfit.1-7,10,22,23,25,26 However, providing the best possible fit and maximum accuracy should always be the goal within the limits of acceptable biological tolerance.25,26 The dimensional accuracy of digital models generated by intraoral scanning has been reported to be higher than that of scanned conventional impressions and gypsum casts.27 The variability of scanned data as specified by the International Organization for Standardization (ISO) standard 5725-1 depends on factors such as equipment capability, calibration condition, operator-based problems, time passed between several scans, and measurements and environmental factors such as temperature and humidity.27,28 The accuracy of intraoral scanners was specified by ISO-5725-1 in terms of precision and trueness.28 Precision describes how close repeated measurements are to each other. Trueness expresses how close a measurement is to the actual dimensions of the object.23,28,29 It is difficult to analyze the trueness of complex objects and surfaces 3-dimensionally. To use a repeated best-fit algorithm is the most powerful method of evaluating the accuracy of the objects because of the failure of reference points.29 The superimposition of 3D data sets has been investigated and the methodology discussed.29,30 Therefore, a best-fit algorithm was used in the present study. Batak et al
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Table 2. Analysis of variance of angular deviations DF
SS
Mean Square
F
P
CHA
1
0.404
0.404
5.28
.035
Error
17
1.298
0.076
d
d
1
0.074
0.074
3.97
.063
Position×CHA
1
0.091
0.091
4.91
.041
Error (position)
17
0.315
0.019
d
d
3D Angular Deviation (°)
Source
0.8
Position
0.6
CHA, coded healing abutment.
0.4
0.2
0.0
Anterior
Posterior
3mm
Anterior
Posterior Position
8mm
Coded Healing Abutment
Figure 6. Mean angular deviations and 95% confidence intervals.
Comparing the distance and angular deviation results of the present study with other studies can be challenging because the results can be affected by the choice of digitization method, reference scanner, best-fit alignment, and distribution and number of surface data points. Fluegge et al23 compared the positional stability of dental implant scan bodies with different implant and abutment connection geometries by using repeated scans. The first part of their experimental protocol was similar to that of the present study in that they positioned scan bodies and scanned 10 times by using a laser scanner (D250; 3Shape) without removing the model from the scanning tray between the scanning cycles. However, they used Type IV gypsum casts from 2 partially edentulous patients, each with 2 implant analogs of different implant systems (maxilla model: left canine and second premolar; mandibular model: left second premolar and first molar positions) and the corresponding polyetheretherketone (PEEK) scan bodies. In the present study, a mandibular stereolithographic model with 2 embedded internal connection implants and titanium CHAs was used. Fluegge et al23 used 1 scanner and compared the precision of the models, as the first model served as reference and the next 9 models were each recorded onto the first models. In the present study, the trueness of STL files obtained from an intraoral scanner was evaluated. To create reference images for the assessment of trueness, Lim et al31 performed an intaglio scan of impressions made with a polyether impression material by using a calibrated desktop scanner (7Series; Dental Wings Inc). In the present study, a master STL was created by using an advanced blue light optical laboratory scanner (COMET L3D 8M 150 Precision Structured Blue Light Scanner; ZEISS), Batak et al
and then 10 scanned data were superimposed on the master model as did Lim et al.31 A different software program was used for the superimposition (PolyWorks software in current, Geomagic in the study by Lim et al,31 and Rapidform XOR2 in the study by Fluegge et al23). Howell et al16 used mandibular stereolithographic models that had parallel implants on one side and nonparallel implants on the contralateral side. The accuracy of Biomet 3i Encode Robocast Technology and conventional implant impression techniques (open tray, closed tray) was compared. All casts were scanned by using 1 intraoral scanner (TRIOS; 3Shape), and a CAD software program (Rapidform XOR; INUS Technology) was used to analyze the scanned data. The difference between the reference data (master model) and the measured data in definitive casts was analyzed for each impression technique. According to the results of that study, the deviation range for the closed tray method at the parallel side (right) was 25.1 to 44.8 mm and 43.2 to 66.2 mm for the nonparallel side (left). For the open tray method, the deviation range was 16.4 to 22.2 mm at the parallel side (right) and 25.3 to 73.9 mm at the nonparallel side (left). For CHA, the deviation range was 41.7 to 131.3 mm at the parallel side (right) and 119 to 126.7 mm at the nonparallel side (left). Eliasson and Ortorp11 analyzed the accuracy by measuring the difference between the reference data obtained from the master model and the measured data in the 15 definitive casts. A laser measuring machine (LMM) (LK, Integra; Metris Metrology Solutions) was used to make the measurements with a highaccuracy 3D laser sensor. All data were calculated in mm as the 3D displacement of the center point (x-, y-, z-axis) of individual implant analogs, concerning the center points of the analogs in the definitive cast. The 3D displacement was 79.5 mm on the test side (pick-up coping) and 31.2 mm on the control side (CHA). In the present study, distance deviations differed between 255.949 and 448.029 mm. When compared with the studies of Eliasson and Ortorp11 and of Howell et al,16 the distance deviation results of the present study are higher. The studies by Eliasson and Ortorp11 and Howell et al16 differ from the present study in the test design, materials, and equipment. The main difference between these studies and the present study
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was that in the present study, STL files from 2 different scanners were used, whereas Eliasson and Ortorp11 and Howell et al16 used only 1 scanner. The distance deviations in current study were also higher than the results found in 2 recently published studies.32,33 The deviations obtained in the present study are high when clinically acceptable discrepancies are considered.34 This may be because, in the present study, 1 model with CHA in different heights was scanned by using 2 different scanners (advanced blue light optical laboratory scanner and intraoral scanner); however, previous studies11,16 compared the master model and definitive casts by using 1 scanner. In the present study, the error found at the impression stage can be considered clinically high. As the fabrication process will continue from the impression stage to design and manufacturing, the error may increase, remain the same, or possibly decrease throughout the process, and the definitive prosthesis fit may be affected accordingly. To fully understand the effect of the error recorded at the impression level, the prosthesis should be fabricated and prosthesis fit should be evaluated to determine the effect of errors at the impression level on the definitive prosthesis fit. The effect of these discrepancies on the accuracy of fit of prostheses was not investigated in this study and should be studied to see whether these discrepancies increase, decrease, or remain during the fabrication process. This was an in vitro study, and the results should be corroborated with clinical studies. Also, the results may differ when different scanners with varying scanning protocols are used. The results may show variation when different operators perform the scanning, and the effect of the operator on the scan accuracy should also be studied. CONCLUSIONS Within the limitations of this in vitro study, the following conclusions were drawn: 1. Trueness of CHA scanning was significantly influenced by the position of the CHA. 2. The anterior CHAs had smaller distance deviations for both CHA heights. 3. The effect of CHA height on distance deviation alone was not found significant; however, height had an effect on the angular deviation depending on the position of the CHA. REFERENCES 1. Lee H, So JS, Hochstedler JL, Ercoli C. The accuracy of implant impressions: a systematic review. J Prosthet Dent 2008;100:285-91. 2. Pesce P, Pera F, Setti P, Menini M. Precision and accuracy of a digital impression scanner in full-arch implant rehabilitation. Int J Prosthodont 2018;31:171-5.
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3. Moreira AH, Rodrigues NF, Pinho AC, Fonseca JC, Vilaça JL. Accuracy comparison of implant impression techniques: a systematic review. Clin Implant Dent Relat Res 2015;17:e751-64. 4. Moreno A, Giménez B, Özcan M, Pradíes G. A clinical protocol for intraoral digital impression of screw-retained CAD/CAM framework on multiple implants based on wavefront sampling technology. Implant Dent 2013;22: 320-5. 5. Papaspyridakos P, Chen CJ, Gallucci GO, Doukoudakis A, Weber HP, Chronopoulos V. Accuracy of implant impressions for partially and completely edentulous patients: a systematic review. Int J Oral Maxillofac Implants 2014;29:836-45. 6. Marghalani A, Weber HP, Finkelman M, Kudara Y, El Rafie K, Papaspyridakos P. Digital versus conventional implant impressions for partially edentulous arches: an evaluation of accuracy. J Prosthet Dent 2018;119:574-9. 7. Moura RV, Kojima AN, Saraceni CHC, Bassolli L, Balducci I, Özcan M, et al. Evaluation of the accuracy of conventional and digital impression techniques for implant restorations. J Prosthodont 2019;28:e530-5. 8. Hacker T, Heydecke G, Reissmann DR. Impact of procedures during prosthodontic treatment on patients’ perceived burdens. J Dent 2015;43: 51-7. 9. Vecsei B, Joós-Kovács G, Borbély J, Hermann P. Comparison of the accuracy of direct and indirect three-dimensional digitizing processes for CAD/CAM systems-An in vitro study. J Prosthodont Res 2017;61:177-84. 10. Nedelcu R, Olsson P, Nyström I, Rydén J, Thor A. Accuracy and precision of 3 intraoral scanners and accuracy of conventional impressions: a novel in vivo analysis method. J Dent 2018;69:110-8. 11. Eliasson A, Ortorp A. The accuracy of an implant impression technique using digitally coded healing abutments. Clin Implant Dent Relat Res 2012;14: e30-8. 12. Al-Abdullah K, Zandparsa R, Finkelman M, Hirayama H. An in vitro comparison of the accuracy of implant impressions with coded healing abutments and different implant angulations. J Prosthet Dent 2013;110: 90-100. 13. Ng SD, Tan KB, Teoh KH, Cheng AC, Nicholls JI. Three-dimensional accuracy of a digitally coded healing abutment implant impression system. Int J Oral Maxillofac Implants 2014;29:927-36. 14. Grossmann Y, Pasciuta M, Finger IM. A novel technique using a coded healing abutment for the fabrication of a CAD/CAM titanium abutment for an implant-supported restoration. J Prosthet Dent 2006;95:258-61. 15. Abduo J, Chen C, Le Breton E, Radu A, Szeto J, Judge R, et al. The effect of coded healing abutments on treatment duration and clinical outcome: a randomized controlled clinical trial comparing Encode and conventional impression protocols. Int J Oral Maxillofac Implants 2017;32:1172-9. 16. Howell KJ, McGlumphy EA, Drago C, Knapik G. Comparison of the accuracy of Biomet 3i Encode Robocast technology and conventional implant impression techniques. Int J Oral Maxillofac Implants 2013;28: 228-40. 17. Telleman G, Raghoebar GM, Vissink A, Meijer HJA. The use of a coded healing abutment as an impression coping to design and mill an individualized anatomic abutment: a clinical report. J Prosthet Dent 2011;105:181-5. 18. Ramsey CD, Ritter RG. Utilization of digital technologies for fabrication of definitive implant-supported restorations. J Esthet Restor Dent 2012;24: 299-309. 19. Mahn DH, Prestipino T. CAD/CAM implant abutments using coded healing abutments: a detailed description of the restorative process. Compend Contin Educ Dent 2013;34:612-5. 20. Nayyar N, Yilmaz B, McGlumphy E. Using digitally coded healing abutments and an intraoral scanner to fabricate implant-supported, cement-retained restorations. J Prosthet Dent 2013;109:210-5. 21. Carpentieri JR, Lazzara RJ. A simplified impression protocol for fabrication of anatomical, cement-retained CAD/CAM abutments. Int J Periodontics Restorative Dent 2014;34:19-25. 22. Mizumoto R, Yilmaz B. Intraoral scan bodies in implant dentistry: a systematic review. J Prosthet Dent 2018;120:343-52. 23. Fluegge T, Att W, Metzger M, Nelson K. A novel method to evaluate precision of optical implant impressions with commercial scan bodies-an experimental approach. J Prosthodont 2017;26:34-41. 24. Alikhasi M, Alsharbaty MHM, Moharrami M. Digital implant impression technique accuracy: a systematic review. Implant Dent 2017;26:929-35. 25. Karl M, Graef F, Schubinski P, Taylor T. Effect of intraoral scanning on the passivity of fit of implant-supported fixed dental prostheses. Quintessence Int 2012;43:555-62. 26. Fukazawa S, Odaira C, Kondo H. Investigation of accuracy and reproducibility of abutment position by intraoral scanners. J Prosthodont Res 2017;61:450-9. 27. Tomita Y, Uechi J, Konno M, Sasamoto S, Iijima M, Mizoguchi I. Accuracy of digital models generated by conventional impression/plaster-model methods and intraoral scanning. Dent Mater J 2018;37:628-33.
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28. International Organization for Standardization. ISO 5275-1. Accuracy (trueness and precision) of measurement methods and results. Part 1: General principles and definitions. Geneva: International Organization for Standardization; 1994. Available at: http://www.iso.org/iso/home.html. 29. Lee SJ, Betensky RA, Gianneschi GE, Gallucci GO. Accuracy of digital versus conventional implant impressions. Clin Oral Implants Res 2015;26: 715-9. 30. 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. 31. Lim JH, Park JM, Kim M, Heo SJ, Myung JY. Comparison of digital intraoral scanner reproducibility and image trueness considering repetitive experience. J Prosthet Dent 2018;119:225-32. 32. Mizumoto RM, Yilmaz B, McGlumphy EA Jr, Seidt J, Johnston WM. Accuracy of different digital scanning techniques and scan bodies for complete-arch implant-supported prostheses. J Prosthet Dent 27 Apr 2019. pii: S00223913(19)30076-9. https://doi.org/10.1016/j.prosdent.2019.01.003. 33. Mizumoto RM, Özcan GAM, Yilmaz B. The effect of scanning the palate and scan body position on the accuracy of complete-arch implant scans. Clin Implant Dent Relat Res 25 Jul 2019. https://doi.org/10.1111/cid.12821.
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34. Abduo J, Judge RB. Implications of implant framework misfit: a systematic review of biomechanical sequelae. Int J Oral Maxillofac Implants 2014;29:608-21. Corresponding author: Dr Burcu Batak Department of Prosthodontics Faculty of Dentistry Ankara University Emniyet mah. Incitas sok. 06560 Yenimahalle, Ankara TURKEY Email: [email protected] Acknowledgments The authors would like to thank Dr William Johnston for his contribution to this manuscript. Copyright © 2019 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2019.06.012
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Effect of coded healing abutment height and position on the trueness of digital intraoral implant scans Burcu Batak, DDS, PhD,a Burak Yilmaz, DDS, PhD,b Karnik Shah, BDS, MS,c Rajat Rathi, BDS,d Martin Schimmel, Dr med dent, MAS, PD,e and Lisa Lang, DDS, MS, MBAf One of the most critical steps in the long-term success of implant restorations is impression accuracy for a definitive cast on which the prosthesis will be fabricated.1 Impression accuracy is affected by implant position, angulation, and depth and in turn affects the fit of the implant-supported prosthesis.2,3 Because implants are functionally ankylosed, the implant-bone interface is not resilient, and, therefore, misfit can lead to mechanical and biological complications, including failure.4,5 Different impression techniques and materials have been used to obtain accurate definitive casts, ensuring an acceptable prosthesis. However, the accuracy of conventional impression techniques and the effect of tray type on impression accuracy are unclear.5-7 In addition, these
ABSTRACT Statement of problem. Information regarding the effect of the height and position of a coded healing abutment (CHA) on the trueness of intraoral digital scans is lacking. Purpose. The purpose of this in vitro study was to investigate the effect of the height and position of a scannable CHA on the trueness (distance and angular deviations) of intraoral digital scans. Material and methods. Scannable CHAs (BellaTek Encode Impression system; Zimmer Biomet Dental) were used in 2 different height pairs (3 mm and 8 mm) on 2 implants at mandibular left second and first molar positions. Each pair was scanned 10 times by using 1 intraoral scanner (TRIOS; 3Shape) by 1 operator to generate a total of 20 intraoral scan files. Master standard tessellation language (STL) files were created for both 3-mm and 8-mm CHA pairs by using a structured blue light scanner (COMET L3D 8M 150 Precision Structured Blue Light Scanner; ZEISS). These master STL files were imported into a software program (PolyWorks Inspector) and were used as the reference for the inspection. Scans obtained by using the intraoral scanner were aligned to the reference scan by using a best-fit alignment to measure the distance and angular deviations. Two-way repeated-measures ANOVA was used to analyze the data, and the Tukey-Kramer test was used to determine significant differences among groups (a=.05). Results. The CHA position had a significant effect on distance deviation (P<.001). However, no significant effect of CHA height on distance deviation was found. The interaction between CHA height and position had a significant effect on the angular deviation (P=.041). The 3-mm posterior CHA (P=.026) and 8-mm anterior CHA (P=.039) had significantly lower angular deviations than the 8-mm posterior CHA. Conclusions. The distance deviation of CHA was significantly influenced by position. CHAs in the anterior had lower distance deviations for both 3 mm and 8 mm. The effect of CHA height on distance deviation was found to be small and was affected by the location of the CHA. Height affected angular deviation depending on the position of the CHA. Both 3-mm posterior and 8-mm anterior CHAs showed lower angular deviations than the 8-mm posterior CHA. (J Prosthet Dent 2019;-:---)
a
Former Visiting Scholar, Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, Ohio; and Research Associate, Department of Prosthodontics, Faculty of Dentistry, Ankara University, Ankara, Turkey. b Professor, Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, Ohio. c Private practice, Austin, Texas. d Former Visiting Scholar, Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, Ohio. e Professor, Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; and Professor, Divison of Gerodontology and Removable Prosthodontics, University of Geneva, Geneva, Switzerland. f Associate Professor, Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Columbus, Ohio.
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Clinical Implications Clinicians should be careful when selecting the height of a scannable coded healing abutment in situations where 2 implants are placed adjacent to each other in the mandibular molar region, as height may affect the trueness of the digital scan. The location of the implant may affect the trueness when coded healing abutments are used with the intraoral scanner used in this study.
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precision of intraoral scanners have been evaluated, most of the studies have tested scan bodies of a single size.11,13,19 The purpose of this in vitro study was to investigate the effect of the height and position of a scannable CHA on the trueness of intraoral digital scans. The null hypotheses were that the CHA height would not affect the trueness of digital intraoral implant scans and that the implant position would not affect the trueness of digital intraoral scans of implants. MATERIAL AND METHODS
techniques are somewhat difficult to perform, are operator sensitive and time-consuming, involve multiple steps, are uncomfortable for patients, and have the potential for errors at every phase.2-4,8 Advances in computer-aided design and computer-aided manufacturing (CAD-CAM) have allowed the fabrication of accurate implant-supported restorations by using an indirect digital workflow through laboratory scanning of the stone cast after making a definitive impression.9,10 A 2-piece coded healing abutment (CHA), which can be captured by using intraoral scanners and eliminates the need for impression copings,11-13 is distinguished by occlusal surface codes that convey information regarding the implant connection type and size, implant hexagon position, and healing abutment height.14,15 The digital scan file can be sent and stored electronically, eliminating physical space requirements and contributing to efficient digital record keeping, and can be used multiple times when needed.4,5,7 The effect of CHAs on treatment duration and clinical outcomes has been evaluated, comparing their accuracy with that of conventional impression techniques.11-21 In recent years, intraoral scan bodies (ISBs) have been marketed in different shapes and sizes and fabricated out of various materials.22 Some of the scan bodies need specific scanners and some can be used with multiple scanners, whose files may be processed by using different CAD-CAM systems.22 The geometry of ISBs varies from a spherical design to a cylindrical design with diverse intermediate forms, with heights ranging from 3 mm to 17 mm.23 All of them consist of an upper scan region, a middle body, and an apical portion known as the base that attaches to the implant.22,23 However, the requirements of the surface geometry and dimension of the implant scan body for an accurate transfer of the implant position to the virtual model have not been analyzed.22 The literature lacks information on the precision of capturing the dimensions of the scan bodies in regard to different surface geometries and dimensions.23,24 Moreover, although digital scans have been compared with conventional impressions, determining the accuracy of restorations generated from both, and the accuracy and THE JOURNAL OF PROSTHETIC DENTISTRY
A mandibular stereolithographic model with 2 embedded internal connection implants (4-mm diameter/3.4-mm platform × 10 mm in length, 3i T3 platform switched Certain Tapered Implant; Zimmer Biomet Dental) at the mandibular left second and first molar positions was used. CHAs (BellaTek Encode Impression system; Zimmer Biomet Dental) were used in 2 different height pairs on both implants (E1 3-4-3, 3 mm in height, and E2 8-4-3, 8 mm in height). Before scanning, titanium dioxide powder (3M High-Resolution Scanning Spray; 3M ESPE) was sprayed onto the surface of the mandibular stereolithographic model and CHAs for constant reflectivity as it was a clear model. Each pair was scanned 10 times by using 1 intraoral scanner (TRIOS; 3Shape) by 1 operator (R.R.) as per the manufacturer’s protocol to generate a total of 20 intraoral scan files (2 abutment heights, 10 scans per size, 1 scanner). The scanning procedure was performed in the same order as recommended by the manufacturer (occlusal and lingual surfaces followed by the buccal surface). The obtained 3D data were converted and recorded as standard tessellation language (STL) data. One master scan was obtained from each group by using an advanced blue light optical laboratory scanner (COMET L3D 8M 150 Precision Structured Blue Light Scanner; ZEISS) having measurement uncertainty certified to 12+0.03L mm (L is the length of the material scanned). These master scan files were obtained in STL format, and these STL files were imported into a software program (PolyWorks Inspector) and were used as the reference for the inspection. Data collected using the intraoral scanner were aligned to the reference by using a best-fit alignment. In the software (PolyWorks Inspector), a best-fit alignment is an automatic algorithm that iteratively translates and rotates the data group, or intraoral scans, to bring it as close as possible to the reference. With this alignment type, only the unchanged features of the STL files are used to help reduce any error that may ensue from the software using outlying data. For each master STL, a coordinate system was created and used throughout the entire inspection (Fig. 1). The Batak et al
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Figure 2. Anterior and posterior coded healing abutment. Figure 1. Coordinate system for master standard tessellation language file.
CHAs used for inspection were labeled as either the anterior or posterior CHA, and those same labels were used for every inspection (Fig. 2). Cylinders were fitted to each CHA, and using the cylinder axes, angular deviations were measured and reported as 3D-angle measurements. In this measurement method, the nominal axis (the axis of the cylinder created from the master STL) is considered to be at an angle of zero, and then the resultant angle between the data and reference axes is reported as the 3D angle. To determine the position of each CHA, circles were fitted to cross-sections at 2 locations of each CHA. The circle center points were used to report the positional deviations relative to the origin of the coordinate system. The cross-sections were created 0.5 mm from the top and 0.5 mm up from the bottom of each CHA (Fig. 3). Additionally, the cross-sections were made normal to the x-y plane. Therefore, there was no difference between the nominal and measured values for the z-direction. To measure the z displacement, a plane was created at the top of each CHA, and then a point was created at the intersection of that plane and axis of the CHA. The distance from that point to the base of the lower jaw mold was measured and reported as the z displacement. On each CHA, there were 2 planes at the top (Fig. 4). Planes were extracted from those surfaces, and then an average plane was created from those two. The angle between the averaged plane and the first plane was in the x-y plane and showed the difference in orientation of the CHAs compared with the master STL. Each distance was calculated from the reference in each of the 3 dimensions using the following formula: qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 3D Distance= Dx +Dy2 +Dz2
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Figure 3. Cross-sections 0.5 mm from top and bottom of each coded healing abutment.
Two-way repeated-measures ANOVA (MIXED procedure; SAS Proprietary Software v9.3; SAS Institute Inc) was used to analyze the data. Tukey-Kramer tests were used to resolve the interaction for the angular deviations. The between-subject factor was the CHA height, and the within-subject factor was the position. For the angular deviation measurements, the restricted maximum likelihood estimation method was used to eliminate the need for normality and equality of variances (a=.05). RESULTS Mean distance deviations and 95% confidence intervals between virtual models produced from scans (master scan by using laboratory scanner and 10 scans by using an intraoral scanner) are presented in Figure 5. Position had a significant effect on the distance deviation (P<.001). Anterior position showed lower distance deviations for both 3-mm and 8-mm CHAs. However, no significant effect of CHA height was found on the distance deviation (Table 1).
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Figure 4. A, Two planes at top of each coded healing abutment. B, Average plane created from these two.
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Table 1. Analysis of variance of distance deviations DF
SS
Mean Square
F
P
CHA
1
40906.324
40906.324
1.75
.204
Error
17
397790.203
23399.424
d
d
1
152839.277
152839.277
85.45
<.001
3D Distance Deviation (µm)
Source
500
Position
400 300
1
758.261
758.261
0.42
.524
Error (position)
17
30407.192
1788.658
d
d
CHA, coded healing abutment.
200 100 0
Position×CHA
Anterior
Posterior
Anterior
3mm
Posterior Position
8mm
Coded Healing Abutment
Figure 5. Mean distance deviations and 95% confidence intervals.
Mean angular deviations and 95% confidence intervals between virtual models produced from scans (master scan by using laboratory scanner and 10 scans by using an intraoral scanner) are presented in Figure 6. The interaction between CHA height and position had a significant effect on angular deviations (Table 2). According to the Tukey-Kramer test, the 3mm posterior CHA had significantly lower angular deviations than the 8-mm posterior CHA (P=.026). The 8-mm anterior CHA had significantly lower angular deviations than the 8-mm CHA in the posterior position (P=.039). DISCUSSION In terms of the trueness of the digital implant scans made in this study, the CHA position had a significant effect on the distance deviation. The interaction between the CHA height and position had a significant effect on the angular deviation. Therefore, the null hypotheses were rejected. THE JOURNAL OF PROSTHETIC DENTISTRY
An absolute passive fit has been stated to be impossible to attain, and different authors propose different acceptable levels of misfit.1-7,10,22,23,25,26 However, providing the best possible fit and maximum accuracy should always be the goal within the limits of acceptable biological tolerance.25,26 The dimensional accuracy of digital models generated by intraoral scanning has been reported to be higher than that of scanned conventional impressions and gypsum casts.27 The variability of scanned data as specified by the International Organization for Standardization (ISO) standard 5725-1 depends on factors such as equipment capability, calibration condition, operator-based problems, time passed between several scans, and measurements and environmental factors such as temperature and humidity.27,28 The accuracy of intraoral scanners was specified by ISO-5725-1 in terms of precision and trueness.28 Precision describes how close repeated measurements are to each other. Trueness expresses how close a measurement is to the actual dimensions of the object.23,28,29 It is difficult to analyze the trueness of complex objects and surfaces 3-dimensionally. To use a repeated best-fit algorithm is the most powerful method of evaluating the accuracy of the objects because of the failure of reference points.29 The superimposition of 3D data sets has been investigated and the methodology discussed.29,30 Therefore, a best-fit algorithm was used in the present study. Batak et al
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Table 2. Analysis of variance of angular deviations DF
SS
Mean Square
F
P
CHA
1
0.404
0.404
5.28
.035
Error
17
1.298
0.076
d
d
1
0.074
0.074
3.97
.063
Position×CHA
1
0.091
0.091
4.91
.041
Error (position)
17
0.315
0.019
d
d
3D Angular Deviation (°)
Source
0.8
Position
0.6
CHA, coded healing abutment.
0.4
0.2
0.0
Anterior
Posterior
3mm
Anterior
Posterior Position
8mm
Coded Healing Abutment
Figure 6. Mean angular deviations and 95% confidence intervals.
Comparing the distance and angular deviation results of the present study with other studies can be challenging because the results can be affected by the choice of digitization method, reference scanner, best-fit alignment, and distribution and number of surface data points. Fluegge et al23 compared the positional stability of dental implant scan bodies with different implant and abutment connection geometries by using repeated scans. The first part of their experimental protocol was similar to that of the present study in that they positioned scan bodies and scanned 10 times by using a laser scanner (D250; 3Shape) without removing the model from the scanning tray between the scanning cycles. However, they used Type IV gypsum casts from 2 partially edentulous patients, each with 2 implant analogs of different implant systems (maxilla model: left canine and second premolar; mandibular model: left second premolar and first molar positions) and the corresponding polyetheretherketone (PEEK) scan bodies. In the present study, a mandibular stereolithographic model with 2 embedded internal connection implants and titanium CHAs was used. Fluegge et al23 used 1 scanner and compared the precision of the models, as the first model served as reference and the next 9 models were each recorded onto the first models. In the present study, the trueness of STL files obtained from an intraoral scanner was evaluated. To create reference images for the assessment of trueness, Lim et al31 performed an intaglio scan of impressions made with a polyether impression material by using a calibrated desktop scanner (7Series; Dental Wings Inc). In the present study, a master STL was created by using an advanced blue light optical laboratory scanner (COMET L3D 8M 150 Precision Structured Blue Light Scanner; ZEISS), Batak et al
and then 10 scanned data were superimposed on the master model as did Lim et al.31 A different software program was used for the superimposition (PolyWorks software in current, Geomagic in the study by Lim et al,31 and Rapidform XOR2 in the study by Fluegge et al23). Howell et al16 used mandibular stereolithographic models that had parallel implants on one side and nonparallel implants on the contralateral side. The accuracy of Biomet 3i Encode Robocast Technology and conventional implant impression techniques (open tray, closed tray) was compared. All casts were scanned by using 1 intraoral scanner (TRIOS; 3Shape), and a CAD software program (Rapidform XOR; INUS Technology) was used to analyze the scanned data. The difference between the reference data (master model) and the measured data in definitive casts was analyzed for each impression technique. According to the results of that study, the deviation range for the closed tray method at the parallel side (right) was 25.1 to 44.8 mm and 43.2 to 66.2 mm for the nonparallel side (left). For the open tray method, the deviation range was 16.4 to 22.2 mm at the parallel side (right) and 25.3 to 73.9 mm at the nonparallel side (left). For CHA, the deviation range was 41.7 to 131.3 mm at the parallel side (right) and 119 to 126.7 mm at the nonparallel side (left). Eliasson and Ortorp11 analyzed the accuracy by measuring the difference between the reference data obtained from the master model and the measured data in the 15 definitive casts. A laser measuring machine (LMM) (LK, Integra; Metris Metrology Solutions) was used to make the measurements with a highaccuracy 3D laser sensor. All data were calculated in mm as the 3D displacement of the center point (x-, y-, z-axis) of individual implant analogs, concerning the center points of the analogs in the definitive cast. The 3D displacement was 79.5 mm on the test side (pick-up coping) and 31.2 mm on the control side (CHA). In the present study, distance deviations differed between 255.949 and 448.029 mm. When compared with the studies of Eliasson and Ortorp11 and of Howell et al,16 the distance deviation results of the present study are higher. The studies by Eliasson and Ortorp11 and Howell et al16 differ from the present study in the test design, materials, and equipment. The main difference between these studies and the present study
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was that in the present study, STL files from 2 different scanners were used, whereas Eliasson and Ortorp11 and Howell et al16 used only 1 scanner. The distance deviations in current study were also higher than the results found in 2 recently published studies.32,33 The deviations obtained in the present study are high when clinically acceptable discrepancies are considered.34 This may be because, in the present study, 1 model with CHA in different heights was scanned by using 2 different scanners (advanced blue light optical laboratory scanner and intraoral scanner); however, previous studies11,16 compared the master model and definitive casts by using 1 scanner. In the present study, the error found at the impression stage can be considered clinically high. As the fabrication process will continue from the impression stage to design and manufacturing, the error may increase, remain the same, or possibly decrease throughout the process, and the definitive prosthesis fit may be affected accordingly. To fully understand the effect of the error recorded at the impression level, the prosthesis should be fabricated and prosthesis fit should be evaluated to determine the effect of errors at the impression level on the definitive prosthesis fit. The effect of these discrepancies on the accuracy of fit of prostheses was not investigated in this study and should be studied to see whether these discrepancies increase, decrease, or remain during the fabrication process. This was an in vitro study, and the results should be corroborated with clinical studies. Also, the results may differ when different scanners with varying scanning protocols are used. The results may show variation when different operators perform the scanning, and the effect of the operator on the scan accuracy should also be studied. CONCLUSIONS Within the limitations of this in vitro study, the following conclusions were drawn: 1. Trueness of CHA scanning was significantly influenced by the position of the CHA. 2. The anterior CHAs had smaller distance deviations for both CHA heights. 3. The effect of CHA height on distance deviation alone was not found significant; however, height had an effect on the angular deviation depending on the position of the CHA. REFERENCES 1. Lee H, So JS, Hochstedler JL, Ercoli C. The accuracy of implant impressions: a systematic review. J Prosthet Dent 2008;100:285-91. 2. Pesce P, Pera F, Setti P, Menini M. Precision and accuracy of a digital impression scanner in full-arch implant rehabilitation. Int J Prosthodont 2018;31:171-5.
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3. Moreira AH, Rodrigues NF, Pinho AC, Fonseca JC, Vilaça JL. Accuracy comparison of implant impression techniques: a systematic review. Clin Implant Dent Relat Res 2015;17:e751-64. 4. Moreno A, Giménez B, Özcan M, Pradíes G. A clinical protocol for intraoral digital impression of screw-retained CAD/CAM framework on multiple implants based on wavefront sampling technology. Implant Dent 2013;22: 320-5. 5. Papaspyridakos P, Chen CJ, Gallucci GO, Doukoudakis A, Weber HP, Chronopoulos V. Accuracy of implant impressions for partially and completely edentulous patients: a systematic review. Int J Oral Maxillofac Implants 2014;29:836-45. 6. Marghalani A, Weber HP, Finkelman M, Kudara Y, El Rafie K, Papaspyridakos P. Digital versus conventional implant impressions for partially edentulous arches: an evaluation of accuracy. J Prosthet Dent 2018;119:574-9. 7. Moura RV, Kojima AN, Saraceni CHC, Bassolli L, Balducci I, Özcan M, et al. Evaluation of the accuracy of conventional and digital impression techniques for implant restorations. J Prosthodont 2019;28:e530-5. 8. Hacker T, Heydecke G, Reissmann DR. Impact of procedures during prosthodontic treatment on patients’ perceived burdens. J Dent 2015;43: 51-7. 9. Vecsei B, Joós-Kovács G, Borbély J, Hermann P. Comparison of the accuracy of direct and indirect three-dimensional digitizing processes for CAD/CAM systems-An in vitro study. J Prosthodont Res 2017;61:177-84. 10. Nedelcu R, Olsson P, Nyström I, Rydén J, Thor A. Accuracy and precision of 3 intraoral scanners and accuracy of conventional impressions: a novel in vivo analysis method. J Dent 2018;69:110-8. 11. Eliasson A, Ortorp A. The accuracy of an implant impression technique using digitally coded healing abutments. Clin Implant Dent Relat Res 2012;14: e30-8. 12. Al-Abdullah K, Zandparsa R, Finkelman M, Hirayama H. An in vitro comparison of the accuracy of implant impressions with coded healing abutments and different implant angulations. J Prosthet Dent 2013;110: 90-100. 13. Ng SD, Tan KB, Teoh KH, Cheng AC, Nicholls JI. Three-dimensional accuracy of a digitally coded healing abutment implant impression system. Int J Oral Maxillofac Implants 2014;29:927-36. 14. Grossmann Y, Pasciuta M, Finger IM. A novel technique using a coded healing abutment for the fabrication of a CAD/CAM titanium abutment for an implant-supported restoration. J Prosthet Dent 2006;95:258-61. 15. Abduo J, Chen C, Le Breton E, Radu A, Szeto J, Judge R, et al. The effect of coded healing abutments on treatment duration and clinical outcome: a randomized controlled clinical trial comparing Encode and conventional impression protocols. Int J Oral Maxillofac Implants 2017;32:1172-9. 16. Howell KJ, McGlumphy EA, Drago C, Knapik G. Comparison of the accuracy of Biomet 3i Encode Robocast technology and conventional implant impression techniques. Int J Oral Maxillofac Implants 2013;28: 228-40. 17. Telleman G, Raghoebar GM, Vissink A, Meijer HJA. The use of a coded healing abutment as an impression coping to design and mill an individualized anatomic abutment: a clinical report. J Prosthet Dent 2011;105:181-5. 18. Ramsey CD, Ritter RG. Utilization of digital technologies for fabrication of definitive implant-supported restorations. J Esthet Restor Dent 2012;24: 299-309. 19. Mahn DH, Prestipino T. CAD/CAM implant abutments using coded healing abutments: a detailed description of the restorative process. Compend Contin Educ Dent 2013;34:612-5. 20. Nayyar N, Yilmaz B, McGlumphy E. Using digitally coded healing abutments and an intraoral scanner to fabricate implant-supported, cement-retained restorations. J Prosthet Dent 2013;109:210-5. 21. Carpentieri JR, Lazzara RJ. A simplified impression protocol for fabrication of anatomical, cement-retained CAD/CAM abutments. Int J Periodontics Restorative Dent 2014;34:19-25. 22. Mizumoto R, Yilmaz B. Intraoral scan bodies in implant dentistry: a systematic review. J Prosthet Dent 2018;120:343-52. 23. Fluegge T, Att W, Metzger M, Nelson K. A novel method to evaluate precision of optical implant impressions with commercial scan bodies-an experimental approach. J Prosthodont 2017;26:34-41. 24. Alikhasi M, Alsharbaty MHM, Moharrami M. Digital implant impression technique accuracy: a systematic review. Implant Dent 2017;26:929-35. 25. Karl M, Graef F, Schubinski P, Taylor T. Effect of intraoral scanning on the passivity of fit of implant-supported fixed dental prostheses. Quintessence Int 2012;43:555-62. 26. Fukazawa S, Odaira C, Kondo H. Investigation of accuracy and reproducibility of abutment position by intraoral scanners. J Prosthodont Res 2017;61:450-9. 27. Tomita Y, Uechi J, Konno M, Sasamoto S, Iijima M, Mizoguchi I. Accuracy of digital models generated by conventional impression/plaster-model methods and intraoral scanning. Dent Mater J 2018;37:628-33.
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28. International Organization for Standardization. ISO 5275-1. Accuracy (trueness and precision) of measurement methods and results. Part 1: General principles and definitions. Geneva: International Organization for Standardization; 1994. Available at: http://www.iso.org/iso/home.html. 29. Lee SJ, Betensky RA, Gianneschi GE, Gallucci GO. Accuracy of digital versus conventional implant impressions. Clin Oral Implants Res 2015;26: 715-9. 30. 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. 31. Lim JH, Park JM, Kim M, Heo SJ, Myung JY. Comparison of digital intraoral scanner reproducibility and image trueness considering repetitive experience. J Prosthet Dent 2018;119:225-32. 32. Mizumoto RM, Yilmaz B, McGlumphy EA Jr, Seidt J, Johnston WM. Accuracy of different digital scanning techniques and scan bodies for complete-arch implant-supported prostheses. J Prosthet Dent 27 Apr 2019. pii: S00223913(19)30076-9. https://doi.org/10.1016/j.prosdent.2019.01.003. 33. Mizumoto RM, Özcan GAM, Yilmaz B. The effect of scanning the palate and scan body position on the accuracy of complete-arch implant scans. Clin Implant Dent Relat Res 25 Jul 2019. https://doi.org/10.1111/cid.12821.
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34. Abduo J, Judge RB. Implications of implant framework misfit: a systematic review of biomechanical sequelae. Int J Oral Maxillofac Implants 2014;29:608-21. Corresponding author: Dr Burcu Batak Department of Prosthodontics Faculty of Dentistry Ankara University Emniyet mah. Incitas sok. 06560 Yenimahalle, Ankara TURKEY Email: [email protected] Acknowledgments The authors would like to thank Dr William Johnston for his contribution to this manuscript. Copyright © 2019 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2019.06.012
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