Computer aided analysis of digitized dental stone replicas by dental CAD/CAM technology.
OBJECTIVE
To determine the reproducibility of digitized dental stone replicas compared to the master model and the reliability of the computer aided analysis.


METHODS
Four master dies, prepared for complete crowns were fabricated in presintered yttria-stabilized tetragonal zirconia (Y-TZP). Eight vinyl polysiloxane impressions (PROVIL novo; Heraeus Kulzer) were taken of each die and stone replicas were poured in type IV stone (Vel-Mix Stone; Kerr). The master dies and the stone replicas were digitized in a touch-probe scanner (Procera Forte; Nobel Biocare AB), to create triangulated surface-models. The point-cloud from the first of the repeated digitizations of each master die was used as CAD-reference-models (CRM). Discrepancies between the points in the triangulated surface-models and the corresponding CRM were measured by a matching-software (CopyCAD 6.504 SP2; Delcam Plc). The distribution of the discrepancies was analyzed and presented in color-difference-maps.


RESULTS
The precision of the measuring method, presented as the repeatability coefficient, ranged between 7 and 16 microm (entire surface), whereas the analysis of the stone replicas revealed a precision (repeatability coefficient) ranging from 19 to 26 microm. The accuracy of the replica to master (the mean discrepancy) ranged from 0.5 to 2.0 microm (95% confidence interval 1.5-2.9 microm).


CONCLUSIONS
The greatest precision of the measurement was seen in the jacket surface of the die. The size of the stone replicas varied and the repeatability coefficient was on average 15 microm (2-25 microm) greater for the replica-to-master alignment than the repeated digitizations of the master.
Persson
Anna S K
AS
Institute of Odontology, Karolinska Institutet, Huddinge, Sweden.
Andersson
Matts
M
Odén
Agneta
A
Sandborgh-Englund
Gunilla
G
D001641:Bicuspid / Q000033:anatomy & histology; D002133:Calcium Sulfate / Q000737:chemistry; D017076:Computer-Aided Design; D003442:Crowns; D003481:Cuspid / Q000033:anatomy & histology; D003760:Dental Impression Materials / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007180:Incisor / Q000033:anatomy & histology; D003765:Models, Dental; D008963:Molar / Q000033:anatomy & histology; D011145:Polyvinyls / Q000737:chemistry; D015203:Reproducibility of Results; D012833:Siloxanes / Q000737:chemistry; D012984:Software; D013499:Surface Properties; D015019:Yttrium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
D003760:Dental Impression Materials; D011145:Polyvinyls; C068743:Provil; D012833:Siloxanes; C034183:vinyl polysiloxane; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium; D002133:Calcium Sulfate