Digital Dentistry and CAD/CAM Workflows
What this domain tests
The scan-to-design-to-manufacture chain: data quality, design parameters, and the manufacturing tolerances that decide whether a digitally produced restoration fits.
Core rules
- Scanning. Intraoral scans are captured as STL or proprietary-exported file sets. Capture the margin region and one uninvolved tooth on each side of the span; stitch or rescan any area flagged for missing data rather than designing over it.
- Design parameters. Mark the margin precisely; set the insertion axis before trimming; cement gap commonly 0.02–0.05 mm with a margin-adjacent zone of near-zero clearance (about 0.5–1.0 mm) so the restoration seats without binding.
- Minimum thickness. Monolithic zirconia needs roughly 0.5–0.7 mm occlusally; lithium disilicate about 1.0–1.5 mm depending on the manufacturer's instructions. Connector cross-sections follow the same rules as analogue zirconia bridges.
- Manufacturing. Milled zirconia is produced oversize to allow for sintering shrinkage, typically around 20–25% linear. Nest with the sprue on a non-critical surface. Printed resins need layer-height control, washing and proper post-curing; biocompatibility depends on full cure.
- Verification. Check the digital design against contacts and occlusion before exporting, and check the finished unit on the printed or stone model before delivery.
Worked example
A scanned maxillary premolar shows a blurred margin on the lingual. Designing a margin there will produce an open margin regardless of milling precision. Rescan the quadrant, or adjust the scan's margin by hand only if the region is genuinely readable. Then place the sprue on the occlusal surface, set the cement gap, and verify the intaglio in the design software's cross-section view before nesting.
Traps that cost marks
- Marking a margin on an unreadable scan.
- Forgetting sintering shrinkage compensation in CAM.
- Placing a sprue on a margin or a contact area.