Statement of problem
Intraoral scanners are promising options for removable prosthodontics. However, analog aids, including occlusion rims, are still used, as a completely digital workflow is challenging and scientific evidence on the topic is scarce.
The purpose of this in vitro study was to assess and compare the trueness and precision of scans obtained from a reference typodont of a completely edentulous maxilla by using an intraoral scanner (TRIOS 3 Pod; 3Shape A/S) with scans obtained by using a laboratory scanner (DScan 3; EGS S.R.L.) from both Type IV stone casts and polysulfide impressions.
Material and methods
The polyurethane resin reference typodont was replicated from a clinical cast and was scanned with a metrological machine to obtain a reference scan. Ten digital casts were obtained by applying standardized scanning strategies to the reference typodont with the intraoral scanner. A device was created to make 10 consistent polysulfide impressions, and a scan of each impression was made with the laboratory scanner and then digitally reversed to obtain 10 digital reversed casts. Ten Type IV stone casts were poured and then scanned with the laboratory scanner to obtain 10 digital extraoral scanner casts. The scans in standard tessellation language (STL) format were imported into a dedicated software program, and the trueness and precision were calculated in μm. In addition to descriptive statistics (confidence interval 95%), 1-way ANOVA followed by the Bonferroni test or the Kruskal-Wallis and the Dunn tests were used to analyze differences among groups (α=.05).
The trueness values (95% confidence interval) were digital intraoral scanner cast=48.7 (37.8-59.5), digital reversed cast=249.9 (121.3-378.5), and digital extraoral scanner cast=308.8 (186.6-430.9); significant differences were detected between digital intraoral scanner cast and digital reversed cast (P<.001) and between digital IOS casts and digital extraoral scanner cast (P<.001). The precision values (95% confidence interval) were digital intraoral scanner cast=46.7 (29.7-63.7), digital reversed cast=271.2 (94.6-447.8), and digital extraoral scanner cast=341.4 (175.5-507.3); significant differences were detected between digital intraoral scanner cast and digital reversed cast (P=.003) and between digital intraoral scanner cast and digital extraoral scanner cast (P=.001).
Directly scanning a solid typodont of a completely edentulous maxilla with the intraoral scanner produced better trueness and precision than scanning the polysulfide impressions or the stone casts with a laboratory scanner.
To read this article in full you will need to make a payment
Purchase one-time access:Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
One-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:Subscribe to Journal of Prosthetic Dentistry
Already a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
- A review of computer-aided design/computer-aided manufacture techniques for removable denture fabrication.Eur J Dent. 2016; 10: 286-291
- Computer-aided technology for fabricating complete dentures: systematic review of historical background, current status, and future perspectives.J Prosthet Dent. 2013; 109: 361-366
- Comparison of retention between maxillary milled and conventional denture bases: a clinical study.J Prosthet Dent. 2017; 117: 233-238
- Comparison of fit of dentures fabricated by traditional techniques versus CAD/CAM technology.J Prosthodont. 2019; 28: 428-435
- A new digital denture procedure: a first practitioners appraisal.BMC Oral Health. 2017; 17: 155
- Accuracy of three impression materials on the totally edentulous maxilla: in vitro/in silico comparative analysis.Materials (Basel). 2020; 13: 515
- Three-dimensional differences between intraoral scans and conventional impressions of edentulous jaws: a clinical study.J Prosthet Dent. 2020; 123: 264-268
- Single-arch digital removable complete denture: a workflow that starts from the intraoral scan.J Prosthet Dent. 2018; 120: 20-24
- Removable complete digital dentures: a workflow that integrates open technologies.J Prosthet Dent. 2018; 119: 727-732
- CAD/CAM fabricated complete dentures: concepts and clinical methods of obtaining required morphological data.J Prosthet Dent. 2012; 107: 34-46
- Edentulous jaw impression techniques: an in vivo comparison of trueness.J Prosthet Dent. 2019; 121: 623-660
- Intraoral scanning to fabricate complete dentures with functional borders: a proof-of-concept case report.BMC Oral Health. 2019; 19: 46
- ISO 5725-1. Accuracy (trueness and precision) of measurement methods and results. Part 1: general principles and definitions.International Organization for Standardization, Berlin1994 (Available at:)
- Comparing the accuracy (trueness and precision) of models of fixed dental prostheses fabricated by digital and conventional workflows.J Prosthodont Res. 2019; 63: 25-30
- Assessing the feasibility and accuracy of digitizing edentulous jaws.J Am Dent Assoc. 2013; 144: 914-920
- Accuracy of complete-arch model using an intraoral video scanner: an in vitro study.J Prosthet Dent. 2016; 115: 755-759
- Accuracy and reproducibility of virtual edentulous casts created by laboratory impression scan protocols.J Prosthet Dent. 2018; 120: 389-395
- Effect of implant angulation, connection length, and impression material on the dimensional accuracy of implant impressions: an in vitro comparative study.Clin Implant Dent Relat Res. 2010; 12: 63-76
- Effect of 2 impression techniques on the dimensional accuracy of working implant prosthesis models: an in vitro study.J Craniofac Surg. 2014; 25: 822-827
- Accuracy and dimensional stability of elastomeric impression materials.J Prosthet Dent. 1979; 42: 159-162
- Dimensional stability of elastomeric impression materials: a critical review of the literature.Eur J Prosthodont Restor Dent. 2011; 19: 163-166
- Dimensional stability of elastomeric impression materials in custom-made and stock trays.J Prosthet Dent. 1984; 52: 514-517
- Clinically relevant mechanical properties of elastomeric impression materials.Int J Prosthodont. 1998; 11: 219-223
- Mechanical properties of elastomeric impression materials: an in vitro comparison.Int J Dent. 2015; 2015: 428286
- Delayed linear expansion of improved dental stone.J Prosthet Dent. 2002; 88: 26-31
- Comparative evaluation of few physical properties of epoxy resin, resin-modified gypsum and conventional type IV gypsum die materials: an in vitro study.J Contemp Dent Pract. 2012; 13: 48-54
- Evaluation of dimensional stability of elastomeric impression materials during disinfection.Bull Tokyo Dent Coll. 1995; 36: 1-7
- Comparative evaluation of dimensional accuracy of elastomeric impression materials when treated with autoclave, microwave, and chemical disinfection.J Int Oral Health. 2015; 7: 22-24
- Dimensional stability of seven elastomeric impression materials immersed in disinfectants.J Prosthet Dent. 1996; 76: 8-14
- A comparative evaluation of the dimensional stability of three different elastomeric impression materials after autoclaving - an invitro study.J Clin Diagn Res. 2014; 8: 48-50
- Applicability and accuracy of an intraoral scanner for scanning multiple implants in edentulous mandibles: a pilot study.J Prosthet Dent. 2014; 111: 186-194
- Accuracy and precision of polyurethane dental arch models fabricated using a three-dimensional subtractive rapid prototyping method with an intraoral scanning technique.Korean J Orthod. 2014; 44: 69-76
- Accuracy and precision of 3 intraoral scanners and accuracy of conventional impressions: a novel in vivo analysis method.J Dent. 2018; 69: 110-118
- Accuracy of four intraoral scanners in oral implantology: a comparative in vitro study.BMC Oral Health. 2017; 17: 92
- Trueness and precision of four intraoral scanners in oral implantology: a comparative in vitro study.PLoS One. 2016; 11: e0163107
- Clinical implications of elastomeric impression materials used for complete denture construction.Dent Med Res. 2018; 6: 19-23
- Impression materials: a comparative review of impression materials most commonly used in restorative dentistry.Dent Clin North Am. 2007; 51: 629-642
- Impression materials: basic properties.Gen Dent. 2000; 48: 51-56
- Relationship between the two arches and its effect in the diagnosis and treatment of complete denture prosthesis.Quintessence Int Dent Dig. 1979; 10: 37-51
- Comparative evaluation of pressure generated on a simulated maxillary oral analog by impression materials in custom trays of different spacer designs: an in vitro study.Contemp Clin Dent. 2016; 7: 55-60
- Impression materials and storage time influence on cast models accuracy.Int J Exp Dent Sci. 2013; 2: 18
- Evaluation of the accuracy of extraoral laboratory scanners with a single-tooth abutment model: a 3D analysis.J Prosthodont Res. 2017; 61: 363-370
- A modified iterative closest point algorithm for 3D point cloud registration.Comput Aided Civil Infrastruct Eng. 2016; 31: 515-534
- Introduction to factor analysis: what it is and how to do it.Contemp Sociol. 1980; 9: 562
- Dimensional changes of dental impression materials by thermal changes.J Biomed Mater Res. 2001; 58: 217-220
Published online: October 23, 2020
© 2020 by the Editorial Council for the Journal of Prosthetic Dentistry.