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Journal Article•DOI•

Accuracy of complete-arch dental impressions: a new method of measuring trueness and precision.

Andreas Ender1, Albert Mehl1•
University of Zurich1
01 Feb 2013-Journal of Prosthetic Dentistry (Elsevier)-Vol. 109, Iss: 2, pp 121-128
TL;DR: The new reference scanner is capable of measuring the precision and trueness of both digital and conventional complete-arch impressions, and the digital impression is less accurate and shows a different pattern of deviation than the conventional impression.
Abstract: STATEMENT OF PROBLEM: A new approach to both 3-dimensional (3D) trueness and precision is necessary to assess the accuracy of intraoral digital impressions and compare them to conventionally acquired impressions. PURPOSE: The purpose of this in vitro study was to evaluate whether a new reference scanner is capable of measuring conventional and digital intraoral complete-arch impressions for 3D accuracy. MATERIAL AND METHODS: A steel reference dentate model was fabricated and measured with a reference scanner (digital reference model). Conventional impressions were made from the reference model, poured with Type IV dental stone, scanned with the reference scanner, and exported as digital models. Additionally, digital impressions of the reference model were made and the digital models were exported. Precision was measured by superimposing the digital models within each group. Superimposing the digital models on the digital reference model assessed the trueness of each impression method. Statistical significance was assessed with an independent sample t test (α=.05). RESULTS: The reference scanner delivered high accuracy over the entire dental arch with a precision of 1.6 ±0.6 µm and a trueness of 5.3 ±1.1 µm. Conventional impressions showed significantly higher precision (12.5 ±2.5 µm) and trueness values (20.4 ±2.2 µm) with small deviations in the second molar region (P<.001). Digital impressions were significantly less accurate with a precision of 32.4 ±9.6 µm and a trueness of 58.6 ±15.8µm (P<.001). More systematic deviations of the digital models were visible across the entire dental arch. CONCLUSIONS: The new reference scanner is capable of measuring the precision and trueness of both digital and conventional complete-arch impressions. The digital impression is less accurate and shows a different pattern of deviation than the conventional impression.

Summary (1 min read)

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Summary

  • With the digital intraoral impression a new class of impression techniques is introduced.
  • Parts of the gypsum model, at least the preparation, had to be digitized with an extraoral scanner to create a digital threedimensional model.
  • Precision describes, how close repeated measurements are to each other.
  • The superimposition of the digital impressions with the reference model gives the basisfor the trueness of the digital impression method.
  • The independent sample t-test was used to analyse statistical differences between the groups 1(a), 2(a) and 3(a) for the precision as well as 1(b), 2(b) and 3(b) for trueness of the different impression methods with p<0.05 (IBM SPSS Statistics Version 19, IBM SPSS, Chicag, USA).
  • Accuracy of conventional impression and gypsum model.
  • In these areas, the difference measurement is not predictable to find the correct nearest signed neighbour.
  • With a accuracy between 3µm and 10µm, the reference scanner is significant below the deviations of conventional full arch impressions and therefore suitable for these ac- curacy and precision measurements.
  • Evaluation of dental arch reproduction using three-dimensional optical digitization J Prosthet Dent, 90(5), 434-440.

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Year:2013
Accuracyofcomplete-archdentalimpressions:anewmethodofmeasuring
truenessandprecision
Ender,Andreas;Mehl,Albert
Abstract:STATEMENTOFPROBLEM:Anew approachtoboth3-dimensional(3D) truenessand
precisionisnecessarytoassesstheaccuracyofintraoraldigitalimpressionsandcomparethemtocon-
ventionallyacquiredimpressions.PURPOSE:Thepurposeofthisinvitrostudywastoevaluatewhether
anewreferencescanneriscapableofmeasuringconventionalanddigitalintraoralcomplete-archimpres-
sionsfor3Daccuracy.MATERIALANDMETHODS:Asteelreferencedentatemodelwasfabricated
andmeasuredwithareferencescanner(digitalreferencemodel).Conventionalimpressionsweremade
fromthereferencemodel,pouredwithTypeIVdentalstone,scannedwiththereferencescanner,and
exportedasdigitalmodels.Additionally,digitalimpressionsofthereferencemodelweremadeandthe
digitalmodelswereexported. Precisionwasmeasuredbysuperimposingthedigitalmodelswithineach
group.Superimposingthedigitalmodelsonthedigitalreferencemodelassessedthetruenessofeach
impressionmethod.Statisticalsignicancewasassessedwithanindependentsamplettest(฀=.05).RE-
SULTS:Thereferencescannerdeliveredhighaccuracyovertheentiredentalarchwithaprecisionof1.6
±0.6µmandatruenessof5.3±1.1µm.Conventionalimpressionsshowedsignicantlyhigherprecision
(12.5±2.5µm)andtruenessvalues(20.4±2.2µm)withsmalldeviationsinthesecondmolarregion
(P<.001).Digitalimpressionsweresignicantlylessaccuratewithaprecisionof32.4±9.6µmanda
truenessof58.6±15.8µm(P<.001).Moresystematicdeviationsofthedigitalmodelswerevisibleacross
theentiredentalarch.CONCLUSIONS:Thenewreferencescanneriscapableofmeasuringtheprecision
andtruenessofbothdigitalandconventionalcomplete-archimpressions.Thedigitalimpressionisless
accurateandshowsadierentpatternofdeviationthantheconventionalimpression.
DOI:https://doi.org/10.1016/S0022-3913(13)60028-1
PostedattheZurichOpenRepositoryandArchive,UniversityofZurich
ZORAURL:https://doi.org/10.5167/uzh-88978
JournalArticle
AcceptedVersion
Originallypublishedat:
Ender,Andreas;Mehl,Albert(2013).Accuracyofcomplete-archdentalimpressions: anewmethodof
measuringtruenessandprecision.JournalofProstheticDentistry,109(2):121-128.
DOI:https://doi.org/10.1016/S0022-3913(13)60028-1
Dental full arch impression, a new high accurate method of measuring trueness
and precision
A. Ender, A. Mehl
Clinic of Preventive Dentistry, Periodontology and Cariology; Division of Computerized Restor-
ative Dentistry, University of Zurich, Zurich, Switzerland
Abstract
Objectives: With the digital intraoral impression a new class of impression techniques is
introduced. To assess the accuracy of these impressions and compare it to conventio-
nal intraoral impression technique threedimensional trueness and precision measure-
ments are necessary. The aim of this study was to evaluate wether a new reference
scanner is capable to measure these threedimensional deviations occuring with conven-
tional and digital intraoral impression techniques of full arch impressions of an in vitro
model.
Methods: A steel reference model was scanned with the reference scanner to evaluate
precision and trueness. The reference model then was used to perform five conventio-
nal impressions with a polyvinylsiloxanether material (Identium, Kettenbach) in a putty
and wash technique with standard stock trays (ASA Permalock, ASA Dental). The con-
ventional impressions were poured with Type IV stone (CamBase, Dentona) and scan-
ned with the reference scanner. Five digital impressions with a optical intraoral scanning
system (CEREC AC, Sirona) were made. In each group, the models were superimposed
and the differences computed with a signed nearest neighbour method. The 90-10%/2
percentile of the differences from each comparison was taken to compute the mean va-
lue for precision. The trueness of each impression method was assessed through su-
perimposition of the impressions with the refefence scan of the steel reference model.
Results: The reference scanner delivers an accuracy with 1.6±0.6 µm for precision and
5.3±1.1 µm for trueness over a full dental arch scan. The conventional impression me-
thod shows significant higher (p<0.001) precision (12.5±2.5 µm) and trueness (20.4±2.2
µm) with only little amount of larger deviations at the second molar region. The digital
impression method was significantly less accurate (p<0.001) with a precision of
32.4±9.6 µm and trueness of 58.6±15.8 µm. More systematic deviation of the digital
model is visible across the entire dental arch.
Significance:The new reference scanner is capable to measure precision and trueness
of both conventional and digital full arch impressions. The digital intraoral impression is
less accurate and shows a complete different pattern of deviation than the conventional
impression method.
Introduction
Dental impressions are a major step in restorative dentistry. They transfer the intraoral
situation of the preparation, the adjacent teeth, the soft tissue and the antagonist to an
extraoral model. This model is then used to produce the final restoration.
The accuracy of this model influences the fit or the restorations which is a major factor
for longevitiy of the restoration (Wettstein, Sailer, Roos, & Hammerle, 2008)(Perakis,
Belser, & Magne, 2004)(Persson, ODEN, ANDERSSON, & Sandborgh-Englund, 2009).
Todays gold standard impression technique ist the physical impression with elastomeric
impression material and stock trays (CI). This negative form of the patients teeth is then
poured with stone, resulting in a physical gypsum model. Various techniques are
described in literature in order to archieve most accurate results (Piwowarczyk, Ottl,
Buchler, Lauer, & Hoffmann, 2002)(Chandran, D. Jagger, R. Jagger, & Barbour, 2010).
With the development of CAD/CAM systems and especially the use of zirkoniumdioxid
for dental restorations, the digital model becomes more and more important. Parts of the
gypsum model, at least the preparation, had to be digitized with an extraoral scanner to
create a digital threedimensional model. On this digital model, the restoration is desig-
ned on a computer with special design software and then milled out of a material block
in a CNC milling machine (Luthardt, Sandkuhl, Herold, & Walter, 2001). After milling, the
dental technician finishes the restoration at the gypsum model. The latest development
in CAD/CAM dentistry is the digital intraoral impression (DI)(Fasbinder, 2010)(Beuer,
Schweiger, & Edelhoff, 2008). The digital intraoral impression(DI) results in a threedi-
mensional virtual model from scanning the patients teeth directly inside the mouth.
Construction and milling can be carried out without a conventional intraoral impression
(CI) with the gypsum model and the following extraoral digitization. If needed, a physical
model can be by rapid prototyping (SLA, 3D-printing or miling) from the intraoral digital
impression data (Fasbinder, 2010).
A fundamental question, beside the clinical handling of the devices for the digital intra-
oral impression (DI) and the ease of the following steps in the digital workflow, is the ac-
curacy of this new impression technique.
Accuracy consists of precision and trueness (ISO 5725-1). Precision describes, how
close repeated measurements are to each other. The higher the precision, the more
predictable is the measurement. Trueness describes, how far the measurement is from
Citations
More filters
Journal Article•DOI•
3D printing in dentistry.

[...]

A. Dawood, B. Marti Marti, V. Sauret-Jackson, Alastair Darwood1•
University of Nottingham1
01 Dec 2015-British Dental Journal
TL;DR: The types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery are reviewed.
Abstract: 3D printing has been hailed as a disruptive technology which will change manufacturing. Used in aerospace, defence, art and design, 3D printing is becoming a subject of great interest in surgery. The technology has a particular resonance with dentistry, and with advances in 3D imaging and modelling technologies such as cone beam computed tomography and intraoral scanning, and with the relatively long history of the use of CAD CAM technologies in dentistry, it will become of increasing importance. Uses of 3D printing include the production of drill guides for dental implants, the production of physical models for prosthodontics, orthodontics and surgery, the manufacture of dental, craniomaxillofacial and orthopaedic implants, and the fabrication of copings and frameworks for implant and dental restorations. This paper reviews the types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery.

692 citations

Journal Article•DOI•
Intraoral scanners in dentistry: a review of the current literature

[...]

Francesco Mangano, Andrea Gandolfi, Giuseppe Luongo, Silvia Logozzo1•
University of Perugia1
12 Dec 2017-BMC Oral Health
TL;DR: Optical impressions reduce patient discomfort; IOS are time-efficient and simplify clinical procedures for the dentist, eliminating plaster models and allowing better communication with the dental technician and with patients; however, with IOS, it can be difficult to detect deep margin lines in prepared teeth and in case of bleeding, there is a learning curve, and there are purchasing and managing costs.
Abstract: Intraoral scanners (IOS) are devices for capturing direct optical impressions in dentistry. The purpose of this narrative review on the use of IOS was to: (1) identify the advantages/disadvantages of using optical impressions compared to conventional impressions; (2) investigate if optical impressions are as accurate as conventional impressions; (3) evaluate the differences between the IOS currently available commercially; (4) determine the current clinical applications/limitations in the use of IOS. Electronic database searches were performed using specific keywords and MeSH terms. The searches were confined to full-text articles written in English and published in peer-reviewed journals between January 2007 and June 2017. One hundred thirty-two studies were included in the present review; among them, 20 were previous literature reviews, 78 were in vivo clinical studies (6 randomized controlled/crossover trials, 31 controlled/comparative studies; 24 cohort studies/case series; 17 case reports) and 34 were in vitro comparative studies. Optical impressions reduce patient discomfort; IOS are time-efficient and simplify clinical procedures for the dentist, eliminating plaster models and allowing better communication with the dental technician and with patients; however, with IOS, it can be difficult to detect deep margin lines in prepared teeth and/or in case of bleeding, there is a learning curve, and there are purchasing and managing costs. The current IOS are sufficiently accurate for capturing impressions for fabricating a whole series of prosthetic restorations (inlays/onlays, copings and frameworks, single crowns and fixed partial dentures) on both natural teeth and implants; in addition, they can be used for smile design, and to fabricate posts and cores, removable partial prostheses and obturators. The literature to date does not support the use of IOS in long-span restorations with natural teeth or implants. Finally, IOS can be integrated in implant dentistry for guided surgery and in orthodontics for fabricating aligners and custom-made devices.

376 citations

Cites background from "Accuracy of complete-arch dental im..."

  • ...To date, the literature does not support the use of IOS in full-arch impressions: several studies and literature reviews have shown that the accuracy of IOS is not yet sufficient in such challenging clinical cases [7, 8, 35, 37, 39]....

    [...]

  • ...Prosthodontics Resin inlays/onlays [65, 66] Long-span fixed partial dentures and/or fixed full arches (6–8 elements) [7, 8, 35, 37, 39]...

    [...]

Journal Article•DOI•
Advancements in CAD/CAM technology: Options for practical implementation

[...]

Tariq F. Alghazzawi1•
Taibah University1
01 Apr 2016-Journal of Prosthodontic Research
TL;DR: A comprehensive review of the current published literature investigating the various methods and techniques for scanning, designing, and fabrication of CAD/CAM generated restorations along with detailing the new classifications of CAD-CAM technology is presented.

359 citations

Journal Article•DOI•
Accuracy of full-arch scans using intraoral scanners

[...]

Sebastian B. M. Patzelt1, Sebastian B. M. Patzelt2, Archontia Emmanouilidi1, Susanne Stampf1, Joerg R. Strub1, Wael Att1 •
University Medical Center Freiburg1, University of Maryland, Baltimore2
01 Jul 2014-Clinical Oral Investigations
TL;DR: The results suggest that the inaccuracies of the obtained datasets may contribute to inaccuracies in the final restorations of intraoral scanners in full-arch scans.
Abstract: This study aimed to evaluate the accuracy of intraoral scanners in full-arch scans. A representative model with 14 prepared abutments was digitized using an industrial scanner (reference scanner) as well as four intraoral scanners (iTero, CEREC AC Bluecam, Lava C.O.S., and Zfx IntraScan). Datasets obtained from different scans were loaded into 3D evaluation software, superimposed, and compared for accuracy. One-way analysis of variance (ANOVA) was implemented to compute differences within groups (precision) as well as comparisons with the reference scan (trueness). A level of statistical significance of p < 0.05 was set. Mean trueness values ranged from 38 to 332.9 μm. Data analysis yielded statistically significant differences between CEREC AC Bluecam and other scanners as well as between Zfx IntraScan and Lava C.O.S. Mean precision values ranged from 37.9 to 99.1 μm. Statistically significant differences were found between CEREC AC Bluecam and Lava C.O.S., CEREC AC Bluecam and iTero, Zfx Intra Scan and Lava C.O.S., and Zfx Intra Scan and iTero (p < 0.05). Except for one intraoral scanner system, all tested systems showed a comparable level of accuracy for full-arch scans of prepared teeth. Further studies are needed to validate the accuracy of these scanners under clinical conditions. Despite excellent accuracy in single-unit scans having been demonstrated, little is known about the accuracy of intraoral scanners in simultaneous scans of multiple abutments. Although most of the tested scanners showed comparable values, the results suggest that the inaccuracies of the obtained datasets may contribute to inaccuracies in the final restorations.

356 citations

Cites background or methods from "Accuracy of complete-arch dental im..."

  • ...Previous studies used metal-based [12, 15, 18] or gypsum [14] reference models....

    [...]

  • ...Ender and Mehl described similar findings of highest deviations in posterior areas due to errors in software processing [15]....

    [...]

  • ...These deviations might be related to incorrect software stitching processes and a summation of matching errors of the captured data during processing [15, 31, 32]....

    [...]

  • ...Maximum differences of up to 170 μmwere found in posterior areas [15]....

    [...]

Journal Article•DOI•
In vivo precision of conventional and digital methods of obtaining complete-arch dental impressions.

[...]

Andreas Ender1, Thomas Attin1, Albert Mehl1•
University of Zurich1
01 Mar 2016-Journal of Prosthetic Dentistry
TL;DR: Conventional and digital impression methods differ significantly in the complete-arch accuracy; however, they achieve equal and higher precision than some conventional impression materials.
Abstract: Statement of problem Digital impression systems have undergone significant development in recent years, but few studies have investigated the accuracy of the technique in vivo, particularly compared with conventional impression techniques. Purpose The purpose of this in vivo study was to investigate the precision of conventional and digital methods for complete-arch impressions. Material and methods Complete-arch impressions were obtained using 5 conventional (polyether, POE; vinylsiloxanether, VSE; direct scannable vinylsiloxanether, VSES; digitized scannable vinylsiloxanether, VSES-D; and irreversible hydrocolloid, ALG) and 7 digital (CEREC Bluecam, CER; CEREC Omnicam, OC; Cadent iTero, ITE; Lava COS, LAV; Lava True Definition Scanner, T-Def; 3Shape Trios, TRI; and 3Shape Trios Color, TRC) techniques. Impressions were made 3 times each in 5 participants (N=15). The impressions were then compared within and between the test groups. The cast surfaces were measured point-to-point using the signed nearest neighbor method. Precision was calculated from the (90%-10%)/2 percentile value. Results The precision ranged from 12.3 μm (VSE) to 167.2 μm (ALG), with the highest precision in the VSE and VSES groups. The deviation pattern varied distinctly according to the impression method. Conventional impressions showed the highest accuracy across the complete dental arch in all groups, except for the ALG group. Conclusions Conventional and digital impression methods differ significantly in the complete-arch accuracy. Digital impression systems had higher local deviations within the complete arch cast; however, they achieve equal and higher precision than some conventional impression materials.

314 citations

Cites methods from "Accuracy of complete-arch dental im..."

  • ...THE JOURNAL OF PROSTHETIC DENTISTRY investigated complete dental arch casts fabricated from digital impressions.(39,43,44) A previous study showed high accuracy of a new reference scanner for replicating the complete-arch geometry....

    [...]

  • ...A previous study showed high accuracy of a new reference scanner for replicating the complete-arch geometry.(43) This reference scanner enables a direct comparison of conventional and digital impressions....

    [...]

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More filters
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Digital dentistry: an overview of recent developments for CAD/CAM generated restorations

[...]

Florian Beuer1, Josef Schweiger1, Daniel Edelhoff1•
Ludwig Maximilian University of Munich1
10 May 2008-British Dental Journal
TL;DR: An overview of CAD/CAM-technologies and systems available for dentistry today is given, which enable the access to new, almost defect-free, industrially prefabricated and controlled materials and an improvement in precision and planning, as well as an increase in efficiency.
Abstract: As in many other industries, production stages are increasingly becoming automated in dental technology. As the price of dental laboratory work has become a major factor in treatment planning and therapy, automation could enable more competitive production in high-wage areas like Western Europe and the USA. Advances in computer technology now enable cost-effective production of individual pieces. Dental restorations produced with computer assistance have become more common in recent years. Most dental companies have access to CAD/CAM procedures, either in the dental practice, the dental laboratory or in the form of production centres. The many benefits associated with CAD/CAM generated dental restorations include: the access to new, almost defect-free, industrially prefabricated and controlled materials; an increase in quality and reproducibility and also data storage commensurate with a standardised chain of production; an improvement in precision and planning, as well as an increase in efficiency. As a result of continual developments in computer hardware and software, new methods of production and new treatment concepts are to be expected, which will enable an additional reduction in costs. Dentists, who will be confronted with these techniques in the future, require certain basic knowledge if they are to benefit from these new procedures. This article gives an overview of CAD/CAM-technologies and systems available for dentistry today.

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Journal Article•DOI•
Clinical evaluation of all-ceramic crowns fabricated from intraoral digital impressions based on the principle of active wavefront sampling

[...]

Andreas Syrek1, Gunnar Reich, Dieter Ranftl1, Christoph Klein1, Barbara Cerny1, Jutta Brodesser1 •
Escuela Politécnica del Ejército1
01 Jul 2010-Journal of Dentistry
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333 citations

Journal Article•DOI•
Full arch scans: conventional versus digital impressions--an in-vitro study.

[...]

Andreas Ender1, Albert Mehl1•
University of Zurich1
01 Jan 2011-International journal of computerized dentistry
TL;DR: In-vitro results show that accuracy of the digital impression is similar to that of the conventional impression, which will have to be confirmed in further clinical studies.
Abstract: The digital intraoral impression has become a central part of the CAD/CAM technique The objective of the present study was to compare the accuracy (trueness and precision) of digital impressions of the full arch with that of conventional impressions on the in-vitro model For this purpose, a master model was acquired with a new reference scanning process, the measuring trueness of which was +/- 41 microm and the precision +/- 25 microm On the one hand, conventional impressions and then plaster models (n = 5) were produced from this master model, and on the other hand, digital impressions were made with the Cerec AC Bluecam and the Lava COS system (each n = 5) The plaster models were also scanned with the reference scanner The available data records were superimposed and the differences determined The deviation from the master model defines the trueness of the impression method The deviations of the models among one another demonstrate the precision of the method The trueness of the impressions was 55 +/- 218 microm in the conventional impression group, for digital impressions with Cerec Bluecam it was 49 +/- 142 microm and for digital impressions with Lava COS 403 +/- 141 microm The precision was 613 +/- 179 microm for conventional impression with Impregum, 309 +/- 71 microm for digital impression with the Cerec Bluecam and 601 +/- 313 microm for digital impression with Lava COS These in-vitro results show that accuracy of the digital impression is similar to that of the conventional impression These results will have to be confirmed in further clinical studies

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Journal Article•DOI•
A New Optical 3-D Device for the Detection of Wear

[...]

Albert Mehl1, W. Gloger1, Karl-Heinz Kunzelmann1, Reinhard Hickel1•
Ludwig Maximilian University of Munich1
01 Nov 1997-Journal of Dental Research
TL;DR: A highly accurate 3-D optical scanner has been developed that utilizes the principles of triangulation and a reference-free automated3-D superimposition software and the ability of the system to determine wear of posterior fillings three-dimensionally has been shown.
Abstract: For the clinical performance of new dental restorative materials to be accurately assessed, the three-dimensional anatomical changes of the functional surfaces of the restoration must be elucidated over time. To this end, a highly accurate 3-D optical scanner has been developed that utilizes the principles of triangulation and a reference-free automated 3-D superimposition software. The aim of this study was to assess the accuracy and the precision of the new system with and without referenced positioning. Additionally, the ability of the system to determine wear of posterior fillings three-dimensionally has been shown. Gypsum replicas of restored teeth were evaluated. The tooth surfaces were scanned with a resolution of 250,000 surface points within a measuring time of 20 to 40 sec. The results show that the precision and accuracy of 3-D data acquisition depend on the surface inclination. Up to an angle of 60 degrees, the precision is better than 3 microns, and the accuracy is better than 6 microns. If exact repositioning of the object before and after occlusal loading is possible, e.g., with in vitro studies, differences on the surface can be determined with a precision of 2.2 microns. In reference-free measurements, which are a necessity in clinical studies, the 3-D data acquisition in combination with the automatic matching program can detect wear with an accuracy of 10 microns. The application of this measuring device for the detection of wear of a composite filling functioning in the mouth has been shown. Since this measuring technique is automated, and measurements of high accuracy can be attained in a short period of time, this system offers the possibility for complex analyses of three-dimensional wear to be conducted on a large number of samples in clinical studies.

234 citations

Journal Article•DOI•
Dimensional accuracy of dental casts: influence of tray material, impression material, and time.

[...]

Sudsukh Thongthammachat1, B. Keith Moore1, M. Thomas Barco1, Suteera Hovijitra1, David T. Brown1, Carl J. Andres1 •
Indiana University – Purdue University Indianapolis1
01 Jun 2002-Journal of Prosthodontics
TL;DR: This study evaluated the influence on dimensional accuracy of dental casts made with different types of trays and impression materials and poured at different and multiple times and found silicone impression material has better dimensional stability than polyether.
Abstract: Purpose This study evaluated the influence on dimensional accuracy of dental casts made with different types of trays and impression materials and poured at different and multiple times. Materials and Methods Two types of stock trays (plastic stock tray, perforated metal stock tray) and 4 types of custom tray materials (autopolymerizing acrylic resin, thermoplastic resin, and 2 types of light-polymerized acrylic resins) were used with 2 types of impression materials (addition polymerizing silicone and polyether), to make impressions of a metal master model. Each tray and impression material was used to make 5 impressions. Casts were made by multiple pourings at 30 minutes, 6 hours, 24 hours, and 30 days after impression making. Using a measuring microscope, 12 distances were calculated based on measurements of 8 reference points. The absolute value of the difference of each measurement was calculated, as was the corresponding measurement on the master model. A Bayesian model using a simple noninformative prior was used to analyze these data. Results Statistical differences within 6 μm were found only with thermoplastic resin tray material for addition silicone, and for thermoplastic resin tray material and 1 type of light-polymerized acrylic resin for polyether. Neither stock trays nor custom trays contributed to the differences in accuracy of the casts. All deviations in casts made with silicone impression material were within a clinically acceptable range. For the polyether, distortions occurred that were clinically unacceptable. Impressions made from polyether distorted over time. Silicone impression material has dimensional stability up to 30 days. Conclusion Accurate casts can be made with either stock trays or custom trays. An impression made from polyether should be poured only once and within 24 hours after impression making, because of the distortion of the material over time. Silicone impression material has better dimensional stability than polyether.

190 citations

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Frequently Asked Questions (1)
Q1. What are the contributions in this paper?

PURPOSE: The purpose of this in vitro study was to evaluate whether a new reference scanner is capable of measuring conventional and digital intraoral complete-arch impressions for 3D accuracy.