705 Accuracy of Digital Model Articulation for Chairside CAD/CAM Restorations

Friday, March 23, 2012: 10:45 a.m. - 12:15 p.m.
Presentation Type: Oral Session
D.J. POTICNY, Dept. of Cariology and Restorative Sciences, University of Michigan, Ann Arbor, MI, and D. FASBINDER, Dept. of Cariol & Rest. Sci. & Endo, University of Michigan, Ann Arbor, MI
Objectives: This study evaluated the accuracy of two scanning techniques used for virtual model alignment when designing restorations with a chairside CAD/CAM system. 

Methods:  A master model was developed with a crown preparation (tooth #14) and an occlusal stop distal to the preparation (Distal Stop) and adjacent crown preparations (teeth #2 and #3) with no occlusal stop distal to the preparations (Distal Extension).  For each test group, the maxillary and mandibular teeth were scanned with a CEREC AC (Sirona Dental Systems) to create ten independent data files.  One group for each crown preparation used a bite registration scanning technique and another group used the buccal bite scanning technique to virtually align the models for the crown design.  Each file was used to design and mill a ceramic crown (IPS Empress CAD/Ivoclar) that was seated on the master model with a silicon material.  The vertical dimension was recorded with a polyvinylsiloxane bite registration material to measure variation from the control model.  The bite registration was sectioned mesiodistally and measured in cross-section at 20X using a measuring microscope and 3D software program.



Occlusal vertical dimension (microns)

Distal Extension

Distal Stop

Master (control)

3125.12+28.95 a

3032.17+12.08 a

Bite Registration Scan

3279.52+69.41 b

3175.06+53.08 b

Buccal Bite Scan

3104.37+35.91 a

3048.51+44.86 a

The data was analyzed using a two-way ANOVA and significant differences were determined with a Tukey test (p<0.05).  Letters indicate significantly different groups.


There was no significant difference in the occlusal vertical dimension between the master model and the crowns made with the buccal bite scan technique.  There was a significant difference in the occlusal vertical dimension between the master model and the crowns made with the bite registration scanning technique.  The buccal bite scanning technique resulted in a more accurate occlusal mounting compared to the bite registration technique.

Keywords: CAD/CAM, Computers, Effectiveness, Occlusion and Technology