Laser digitization of casts to determine the effect of tray selection and cast formation technique on accuracy☆,☆☆,★,★★,♢,♢♢,♦
Section snippets
Material and methods
A total of 56 impressions were made of a machined stainless steel master die. The master die was shaped like a dental arch with 5 metal studs resembling teeth prepared for a fixed prosthesis (Fig. 3).12The occlusal surfaces of the studs were marked with crosshairs
Results
The RMSE for the die measurements for between-stud distances was 92.2 μm. When compared to the RMSE for the casts (Table II), there was not much difference; in fact, some RMSEs for casts were smaller.Location measured RMSE (μm) A-B 100.6 (82.4 with one outlier removed) A-C 120.6 A-D 96.7 A-E 86.2 B-C 106.9 (93.4 with one outlier removed) B-D 84.4 B-E 105.7 C-D 109.6 C-E 113.6 D-E 100.3 HA 21.7 (9.3 with one outlier removed) HB 131.5 (12.1 with four outliers removed) HC
Discussion
If the casts had in truth no systematic differences from each other, one would still expect a few of the 45 tests to give P<.05, purely by chance. This fact and the absence of any pattern in the 4 significant tests suggest that these tests may have all been type I errors, or false-positive findings. Specifically, if all 45 null hypotheses were true and the 45 tests were independent, the chance of 4 or more significant tests would be 0.18. Similarly, the lack of consistency or trend of the cast
Conclusions
Within the limitations of this study, in which a 3-dimensional optical digitizer was used for evaluation purposes, neither impression tray type nor cast formation technique affected accuracy. Custom and stock impression trays used in combination with an elastomeric impression material produced equally accurate casts.
Supplementary Files
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Cited by (56)
Volumetric evaluation and three-dimensional accuracy of different elastomeric impression materials
2018, Measurement: Journal of the International Measurement ConfederationCitation Excerpt :According to the studies above accuracy of impression materials were related to many factors, such as the type of impression materials and trays, various impression techniques and the geometry of the master model. In previous studies, the master models used for assessment of impression materials were designed linear [2,3], or arch form [27,42]. It was stated that arch shaped master models would be more relevant to clinical conditions in the evaluation of impression materials [23].
Effect of dental technician disparities on the 3-dimensional accuracy of definitive casts
2017, Journal of Prosthetic DentistryIn vivo precision of conventional and digital methods of obtaining complete-arch dental impressions
2016, Journal of Prosthetic DentistryEvaluation of additive manufacturing (AM) techniques for the production of metal-ceramic dental restorations
2015, Journal of Manufacturing ProcessesCitation Excerpt :However, the digitization of an oral impression is arduous, because of its concave geometries, and could result in a poor virtual representation. Consequently, at the moment, the indirect procedure, involving impression taking and replica production, is still more accurate, and thus the stone replica is commonly digitized [3–5]. A technician can design the restoration from a Virtual Model of the prepared tooth, using a specific CAD tool.
The effect of pouring time on the dimensional stability of casts made from conventional and extended-pour irreversible hydrocolloids by 3D modelling
2015, Journal of Dental SciencesCitation Excerpt :Acceptable methods of measuring the dimensional accuracy of casts include measuring with microscopes,28,29 micrometers,30 dial gauges,31 calipers,32 and digital modeling,9 and there is no general agreement as to which measuring device is best. Although manual measuring techniques offer a number of advantages in that they are easy to use, inexpensive, and readily available, they have the disadvantages of being time-consuming, subject to operator fatigue and error, and capable of making linear measurements in only a few locations.21,33 The use of digital models to measure dimensional stability is a relatively new technique that has an accuracy of up to 10 μm, and the models have been found to be as reliable as traditional stone models.9
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This research was supported by the University of Minnesota School of Dentistry Summer Research Fellowship Program NIH/5T35-DE07098-19, the University of Minnesota School of Dentistry Dental Research Institute, NIH/NIDCR grant P30 DE09737, and the Minnesota Dental Research Center for Biomaterials and Biomechanics. This research was presented at the IADR annual meeting in Washington DC, April 8, 2000.
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aAssistant Professor, Division of Prosthodontics, Department of Restorative Sciences, School of Dentistry.
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bAssociate Professor, Division of Prosthodontics, Department of Restorative Sciences, School of Dentistry.
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cDental Student, Summer Research Fellowship, School of Dentistry.
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dProfessor, Department of Oral Sciences, Minnesota Dental Research Center for Biomaterials and Biomechanics.
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eSenior Research Associate, Division of Biostatistics.
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Reprint requests to: Dr Mary Elizabeth Brosky, Department of Restorative Sciences, 9-450a Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, Fax: (612)626-1496, E-mail: [email protected]