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Grinding damage assessment for CAD-CAM restorative materials
Philippe Curran1, Maria Cattani-Lorente2, H W Anselm Wiskott2
1Division of Oral and Maxillofacial Surgery, Unit of Oral Surgery and Implantology, Department of Surgery, University of Geneva & University Hospitals of Geneva, Geneva, Switzerland.
Summary
Grinding CAD-CAM ceramics with diamond discs causes damage, significantly reducing the strength of glass-ceramics. Softer materials like resin-infiltrated feldspar and nano-ceramic composites are more resistant to this surface damage.
Area of Science:
- Dental Materials Science
- Biomaterials Engineering
- Ceramic Engineering
Background:
- Computer-Aided Design/Computer-Aided Manufacturing (CAD-CAM) materials are widely used for dental restorations.
- Grinding and finishing procedures can induce surface and subsurface damage, potentially compromising the mechanical integrity of these materials.
- Understanding the impact of grinding on different CAD-CAM materials is crucial for ensuring restoration longevity.
Purpose of the Study:
- To evaluate the extent of surface and subsurface damage on five different CAD-CAM restorative materials after grinding with diamond discs.
- To quantify the potential loss in fracture strength based on measured crack sizes.
- To compare the damage susceptibility and strength reduction across various ceramic and composite materials.
Main Methods:
- Five CAD-CAM materials were tested: Lithium disilicate (LIT), leucite glass-ceramic (LEU), feldspar ceramic (VM2), resin-infiltrated feldspar ceramic (EN), and nano-ceramic composite (LU).
- Specimens were ground using diamond discs of 75µm, 54µm, and 18µm grit sizes.
- Chip damage at the bonded interface was quantified using Scanning Electron Microscopy (SEM).
- Fracture mechanics principles were applied to estimate fracture stresses and strength loss based on chip dimensions.
Main Results:
- Grinding with a 75µm diamond disc caused critical chips (avg. 100µm) in glass-ceramics (LIT, LEU, VM2), leading to an estimated strength loss of 33-54%.
- Softer materials, resin-infiltrated feldspar ceramic (EN) and nano-ceramic composite (LU), exhibited minimal damage (avg. 26µm and 17µm chips, respectively) with no significant strength loss.
- Even finer grinding (18µm) remained detrimental to Lithium disilicate (LIT), causing 43µm chips and a 42% potential strength reduction.
Conclusions:
- Grinding glass-ceramics and feldspar ceramics with diamond discs induces significant surface and subsurface damage, reducing their strength.
- Resin-infiltrated and nano-ceramic composite materials demonstrate superior resistance to grinding-induced damage compared to traditional glass-ceramics.
- Post-grinding polishing is essential, particularly for glass-ceramics, to mitigate strength degradation.
