Two imaging techniques for 3D quantification of pre-cementation space for CAD/CAM crowns.
OBJECTIVE
Internal three-dimensional (3D) "fit" of prostheses to prepared teeth is likely more important clinically than "fit" judged only at the level of the margin (i.e. marginal "opening"). This work evaluates two techniques for quantitatively defining 3D "fit", both using pre-cementation space impressions: X-ray microcomputed tomography (micro-CT) and quantitative optical analysis. Both techniques are of interest for comparison of CAD/CAM system capabilities and for documenting "fit" as part of clinical studies.


METHODS
Pre-cementation space impressions were taken of a single zirconia coping on its die using a low viscosity poly(vinyl siloxane) impression material. Calibration specimens of this material were fabricated between the measuring platens of a micrometre. Both calibration curves and pre-cementation space impression data sets were obtained by examination using micro-CT and quantitative optical analysis. Regression analysis was used to compare calibration curves with calibration sets.


RESULTS
Micro-CT calibration data showed tighter 95% confidence intervals and was able to measure over a wider thickness range than for the optical technique. Regions of interest (e.g., lingual, cervical) were more easily analysed with optical image analysis and this technique was more suitable for extremely thin impression walls (<10-15μm). Specimen preparation is easier for micro-CT and segmentation parameters appeared to capture dimensions accurately.


CONCLUSIONS
Both micro-CT and the optical method can be used to quantify the thickness of pre-cementation space impressions. Each has advantages and limitations but either technique has the potential for use as part of clinical studies or CAD/CAM protocol optimization.
Rungruanganunt
Patchanee
P
Department of Reconstructive Sciences, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-1615, USA. PATCH@NSO1.UCHC.EDU
Kelly
J Robert
JR
Adams
Douglas J
DJ
D002484:Cementation / Q000379:methods*; D017076:Computer-Aided Design; D003442:Crowns; D003760:Dental Impression Materials; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016014:Linear Models; D023861:Photography, Dental; D011145:Polyvinyls; D017755:Prosthesis Fitting / Q000379:methods; D012833:Siloxanes; D014172:Transillumination; D055114:X-Ray Microtomography
D003760:Dental Impression Materials; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane; D003776:Dental Porcelain