In-Vitro Horizontal Marginal Adaptation Comparison of CAD/CAM Zirconium Copings

Objectives: Limited data exists regarding dental CAD/CAM system accuracy and precision. This study evaluated the horizontal marginal adaptation of zirconium-oxide copings from contemporary CAD/CAM systems.

Methods: Zirconium-oxide copings were milled using KaVo Everest (ZH, ZS), Nobel Biocare Procera (MOD40, Piccolo, Forte), 3M ESPE Lava, Wieland Zeno, and Sirona CEREC (In-Ceram Zirconium) and compared to control cast copings (n=10). Ninety polyvinylsiloxane impressions were made of a master metal die exhibiting a heavy chamfer preparation finish-line. Type IV dies were scanned, finish line detected, and copings designed with 50µm cement space 1mm from finish line. Control cast copings were fabricated using the lost wax technique. Standardized digital photographs were taken of each coping on the metal master die. The absolute mean horizontal marginal adaptation in microns was determined using the measurement tool in Adobe Photoshop CS2.

Results: The ANOVA revealed statistically significant differences in absolute mean horizontal marginal adaptation between manufacturer groups (p<0.0001). The Procera groups were horizontally under-extended, whereas the remaining groups were horizontally over-extended.

Group	Absolute Mean Marginal Adaptation (µm)	Group Comparisons
Procera-Forte	2.21±1.87	A    B
Procera-MOD40	4.23±1.89	A    B    C
Procera-Piccolo	4.65±2.32	A    B    C
Everest-ZH	6.49±2.20	B    C    D
Control-Cast	9.34±2.81	C    D    E
Cerec-inLab	11.86±5.85	D    E
Everest-ZS	27.04±3.76	F
3M ESPE-Lava	29.72±0.72	F
Wieland-Zeno	30.68±2.34	F

Means with same letter not significantly different, Tukey's HSD test, p>0.05.

Conclusion: Apparent differences among manufacturer's CAD/CAM processes result in varying degrees of horizontal marginal misfit for as-milled zirconium-dioxide copings. Thus, the extent of margin refinement of CAD/CAM copings required by the dental technician through either selective subtractive hand finishing or porcelain margin repair also varies. Further investigations regarding coping rotational resistance form and intaglio coping fit are required. Supported by NIH/NIDCR T32 DEO14678, University of Iowa, College of Dentistry.