420 Quantitative Analysis of Chipping on CAD/CAM-milled Edges

Thursday, March 22, 2012: 3:30 p.m. - 4:45 p.m.
Presentation Type: Poster Discussion Session
J.C. ROLF, R. RUSIN, and V.A. RUSSELL, 3M ESPE Dental, St. Paul, MN

Objectives :   

Compare edge integrity of CAD/CAM machined materials of CAD/CAM materials to a new Resin Nano Ceramic CAD/CAM material, 3M™ ESPE™ Lava™ Ultimate CAD/CAM Restorative(LVU). LVU contains about 79 wt% nanoceramic particles that reinforce a highly crosslinked polymeric matrix.  

Methods :   

Test bars (1.24x4x16 mm) were milled on CEREC inLab MCXL in fast-mill mode.  The 4 mm edge was analyzed on 4 bars of each material via optical microscopy using an Olympus MX-61, with a 5X objective, dark field illumination mode for enhancing visibility of chip boundaries, and image stitching for capturing the full length of each edge.  The lengths (along the edge) and heights (perpendicular to edge) of chips were measured with the count & measure tool in the StreamEssentials™ image analysis software by Olympus.  Data were analyzed via ANOVA with Tukey's t-test (p<0.05).


Each 4 mm edge contained between 12-30 chips, depending on the material.  Average chip length, height, and standard deviations for each group of materials are shown in the table.  Each letter in column “SND” denotes groups that are statistically not different (SND) via ANOVA with Tukey's t-test (p>0.05).

Conclusions :  

The mean chip length and height on milled edges of the resin nanoceramic material LVU is smaller than those of MZ, VM2, EMP, and EMX.  LVU has improved edge chipping resistance compared to all tested materials.  The improved edge quality may be attributed to LVU's combination of high strength and low modulus (reported in another study), which allow the material to withstand milling stresses without suffering significant chipping damage.  The edge quality helps support LVU's use in demanding single-unit restorations.



Keywords: CAD/CAM, Ceramics, Dental materials, Digital image analysis and Quality
Presenting author's disclosure statement: I am employed by 3M ESPE.