Application of a 3-dimensional measurement system to complete denture impressions.
BACKGROUND
Little is known about tissue displacement at the tissue/denture base interface during impression making.


OBJECTIVE
This study used a new 3-dimensional measurement system to analyze and compare 2 complete denture reline impression techniques (1 occluding and 1 digital) to determine which resulted in less displacement of the tissue/denture base interface during impression making.


METHODS
The experiment included 10 completely edentulous subjects. For each subject, 3 mandibular casts were obtained: (1) a reference cast of the existing denture base, (2) a cast made with an occluding reline impression technique, and (3) a cast made with a digital reline impression technique. With the use of an optical 3-dimensional measurement system, the corresponding casts in a common coordinate system were analyzed geometrically. For each cast, the coordinates of the barycentric point and the high point were determined. For the same subject, the differences between the coordinates of the barycentric points of the 3 casts were calculated 2-by-2. The same calculation was performed for the high points. To determine whether these differences, which represent the displacements of the barycentric points and the high points, were statistically significant, the Wilcoxon signed-rank test for paired group comparisons was applied (P<.05). Cartographic differences among the casts from the same subject also were compared.


RESULTS
The uncertainty of measurement for the location of the barycentric and highest point was +/-57 microm. The uncertainty in the differences among the cartographic displays was +/-0.1 mm. Vertically, the mean distance that separated the barycentric points obtained with the 2 impression methods was 0.04 mm. Cartography data showed that the greatest dimensional differences between the 2 impression techniques (minimum 0.25 mm; maximum 1.5 mm) were located near the retromolar pad and along the lingual flange.


CONCLUSIONS
Within the limitations of this 3-dimensional in vivo study, displacement of the tissue/denture base interface was essentially equivalent with the use of an occluding and a digital mandibular impression technique.
Rignon-Bret
Christophe
C
Department of Prosthetic Dentistry, Rene Descartes University, Montrouge, Paris, France. rignon-bret@odontologie.univ-paris5.fr
Dupuis
Raphael
R
Gaudy
Jean-François
JF
D000368:Aged; D000369:Aged, 80 and over; D002138:Calibration; D003724:Dental Arch / Q000473:pathology; D003760:Dental Impression Materials / Q000737:chemistry; D003761:Dental Impression Technique; D003819:Denture Bases; D003823:Denture Rebasing; D003824:Denture, Complete; D020724:Elastomers / Q000737:chemistry; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008334:Mandible / Q000473:pathology; D016555:Matched-Pair Analysis; D009061:Mouth Mucosa / Q000473:pathology / Q000503:physiopathology; D009066:Mouth, Edentulous / Q000473:pathology / Q000503:physiopathology; D055095:Optics and Photonics / Q000295:instrumentation; D011312:Pressure; D018709:Statistics, Nonparametric; D013499:Surface Properties; D016474:Weight-Bearing
D003760:Dental Impression Materials; D020724:Elastomers