Comparison of Maximum Intercuspal Contacts of Articulated Casts and Virtual Casts Requiring Posterior Fixed Partial Dentures

Abstract

Purpose: To evaluate the accuracy of the CEREC CAD/CAM system in reproducing the maximum intercuspal contacts of the casts, which include posterior teeth preparation for a fixed partial denture (FPD). Materials and Methods: Ten pairs of gypsum casts were mounted in articulators in maximum intercuspal position (MIP) to serve as patient simulation models. Tooth #19 was removed from the cast. Occlusal contacts in MIP were identified with articulating paper, and digital impressions of the casts with unprepared teeth and buccal images in MIP were taken. Teeth #18 and #20 were prepared for an FPD, and full-and half-arch digital impressions of the casts with prepared teeth and buccal images from different sides were taken. In each situation, screenshot images of the virtual casts with occlusal contacts were saved as JPEG files. The proportions of congruence of virtual contacts with cast contacts were analyzed by superimposing screenshot images of the virtual casts onto the screenshot images of the casts with the indicated occlusal contacts in a transparent manner using an image-processing program. The data were statistically analyzed with a paired t-test. Results: The highest percentages of virtually indicated contacts identical to the cast contacts were observed in non-prepared full-arch digital impressions. Comparison of full-arch impressions taken before and after tooth preparation showed no difference for congruence even if the buccal image was taken from the contralateral or ipsilateral side (p > 0.05). After tooth preparation, comparing full-and half-arch digital impressions revealed that half-arch impression showed significantly lower percentages of identical contacts (p < 0.05). When comparing the buccal image side, no significant difference was detected between ipsilateral and contralateral images both for non-prepared and prepared casts (p > 0.05). Conclusion: When there is no posterior antagonist contact following tooth preparation for an FPD, taking a full-arch digital impression and designing the restoration on fullarch virtual models can be advocated.

Clinical study on the success of posterior monolithic zirconia crowns and fixed dental prostheses: preliminary report

“…This may be attributed to lack of accuracy of CAD software in simulating jaw occlusion, which includes posterior multiple teeth preparations. 11 To minimize discrepancies, taking a full-arch digital impression and designing the restoration on full-arch virtual models, as well as gathering bite image impressions before preparation, has been strongly advocated by Arslan et al 11 The esthetic success of a dental restoration depends on a number of factors, such as crown contour, surface texture, translucency, and color. In the present study, crown contours were generally found to be "excellent".…”

Accuracy of Dynamic Virtual Articulation: Trueness and Precision

“…Others have evaluated deviations in virtual articulation using 2D or 3D analysis software to superimpose and calculate distortions between images of virtual models but only at a static relationship in maximum intercuspation and without movements. These studies demonstrated that accuracy between mechanical and virtual models was comparable . Common to all of these studies is testing the static relationship of maxillary and mandibular teeth/models in the static maximum intercuspation position.…”

Construction of virtual intercuspal occlusion: Considering tooth displacement

“…Overlap is the ratio of overlap of the virtual contact areas compared with the reference. The closer the result of the 3 indexes are to 1, the better 23‐29 …”