1. Preparation Inlay preparations: ≥1.5mm occlusal reduction Isthmus ≥2mm
Wall divergence: ― to +6°
Gingival seat ≥1.2mm & flat
Box: wall flare 6°
Pulpal/axial line angle: rounded

2. Flat seat (no lip)
Rounded
≥2mm
≥1.2mm

3. 6° flare

4. ― to 6° divergence
≥1.5mm
≥2mm
6° divergence

5. Must fit the diameter of 1.6mm or 1.2mm milling diamond
Gentle curves
Must fit the diameter of 1.6mm or 1.2mm milling diamond

6. Preparation Onlay preparations: Working cusp reduction ≥2.0mm
Non-working cusp reduction ≥1.5mm
Shoulder ≥1.2mm

7. Flat (no lip)
≥1.2mm
≥1.2mm
≥1.2mm

8. ≥2mm
Flat, parallel planes

9. Gentle curve to fit 1.6 or 1.2 milling diamond
Smooth, straight flares
Flat, 1.2mm
Gentle curve to margin
Flat floor parallel to camera face

10. Preparation Crown preparations: Working cusp reduction ≥2.0mm
Non-working cusp reduction ≥1.5mm
Shoulder ≥1.2mm
Rounded transitions

11. ≥1.5mm
≥2mm
≥2mm

12. Flat & parallel
Height of contour
Smooth transition

13. ≥1.2mm
≥1.2mm
≥1.2mm
≥1.2mm