|
Sign In to gain access to subscriptions and/or personal tools.
|
Accuracy of a System for Creating 3D Computer Models of Dental Arches
R. DeLong1,*,
M. Heinzen1,
J.S. Hodges2,
C.-C. Ko1 and
W.H. Douglas1
1 Minnesota Dental Research Center for Biomaterials and Biomechanics, Department of Oral Science, University of Minnesota School of Dentistry, Moos Health Science Tower, 515 Delaware Street SE, Minneapolis, MN 55455; and
2 Division of Biostatistics and Oral Health Clinical Research Center, Department of Preventive Sciences, University of Minnesota;
View larger version (57K):
[in this window]
[in a new window]
|
Figure 1. Block diagram of the experimental method. Three-dimensional computer models were created in a clinically relevant four-step process: (1) make impression, (2) pour cast, (3) scan cast, and (4) process the scan data. Accuracy of the computer models and error introduced at each step were measured according to four physical models: a steel "dental" standard, impressions of the steel standard, and a stone standard and stone casts made from the impressions. The steel and stone standards were measured independently by means of a coordinate measuring machine (CMM). Mathematical computer models of the standards were created from the CMM measurements. Measurement parameters with dental relevance were also calculated from the CMM measurements. Computer models of the stone standard, impressions, and casts were created with custom software that processed data from an optical scanner. Model accuracy and errors introduced at each step in the model creation process were calculated by comparison of the impression, cast, and stone standard computer models with the mathematical computer models. Comparing VDP-calculated parameters with those calculated by the CMM measurements determined the accuracy of the VDP software measurement tools.
|
|
View larger version (44K):
[in this window]
[in a new window]
|
Figure 2. Distributions of the absolute differences between computer and mathematical models. (A) Contour plots (Range, -0.100 mm to +0.100 mm) of the difference between a stone cast model and the steel mathematical model and the difference between an impression model and the steel mathematical model. Differences are displayed on the mathematical model. The contour plots show large distortions in the stone cast. (B) The absolute distance distribution is a plot of the percent of absolute distances between a computer model and the mathematical model that are less than or equal to a given absolute distance. For example, 90% of the absolute distances between the stone cast model and the steel mathematical model (Stone Cast) are less than or equal to 0.050 mm. The absolute distances between the impression models and steel mathematical model (Impressions) and the absolute distances between stone cast models and the stone mathematical model (Stone Standard) are nearly identical and lie below the Stone Cast curve. Ideally, the slope of the curve would be zero, indicating that the absolute distance between the two surfaces was the same across the entire surface, with a magnitude of zero. Distortions in the stone cast are apparent because its distribution curve compared with the steel mathematical standard lies above the analogous curve comparing it with the stone mathematical standard. The abrupt rise in the last 0.1% of distances represents scanner errors that should be excluded.
|
|
Journal of Dental Research, Vol. 82, No. 6,
438-442 (2003)
DOI: 10.1177/154405910308200607
 CiteULike  Complore  Connotea  Del.icio.us  Digg  Reddit  Technorati  Twitter What's this?
|
|
