Overview - ISO 18675:2022 (Dentistry - Machinable ceramic blanks)
ISO 18675:2022 specifies test methods and reporting requirements for machinable ceramic blanks used to fabricate dental fixed restorations. The standard covers evaluation of common dental ceramic blank types (green, partially sintered and fully dense), with particular attention to materials such as zirconia and glass ceramics. It defines tests for shrinkage, homogeneity, warpage, dimensional changes after crystallization or sintering, and machining-induced damage - and sets out the expected contents of the test report.
Key topics and technical requirements
- Classification of blanks: type 1 (green), type 2 (partially sintered), type 3 (fully dense).
- Shrinkage factor and homogeneity: methods to determine linear/volumetric shrinkage for partially sintered zirconia and to assess uniformity across a blank. (Example specimen guidance: bar-size specimens with widths around 7.5 mm and lengths around 60 mm are described for measurement.)
- Warpage testing: procedures for quantifying distortion after final sintering or post-processing for different blank sizes.
- Dimensional stability after crystallization: tests for glass-ceramic materials that require post‑machining crystallization and may undergo distortion.
- Machining damage assessment: methods to evaluate surface/subsurface defects that reduce strength or affect minimum machinable thickness.
- Merlon fracture (machinability) test: standardized milling geometries and characterization procedures to assess how a material behaves under typical CAD/CAM machining.
- Test report contents: standardized information to be recorded and reported for traceability and quality control.
Practical applications and users
ISO 18675:2022 is intended for:
- Dental material manufacturers validating machinable blanks before release.
- Dental CAD/CAM system and milling-machine manufacturers integrating shrinkage and homogeneity data into compensation algorithms.
- Dental laboratories and clinics conducting incoming quality checks of blanks used for crowns, bridges and multi-unit restorations.
- Regulatory, quality and R&D teams assessing machinability, dimensional accuracy and post‑processing stability for product development and compliance.
Practical uses include quality control, supplier qualification, CAD/CAM compensation settings, and failure‑mode analysis related to machining damage or post-crystallization distortion.
Related standards
- ISO 6872 - Dentistry: Ceramic materials (material property context)
- ISO 1942 - Dentistry vocabulary (terms and definitions)
- ISO 10993-1 and ISO 7405 - referenced when assessing biological/toxicological concerns
Keywords: ISO 18675:2022, machinable ceramic blanks, dentistry, zirconia, glass-ceramic, shrinkage factor, warpage, machining damage, dental CAD/CAM.
