Introduction to Implant-Supported Crowns

Implant-supported crowns represent one of the most technically demanding — and rewarding — areas of dental laboratory work. Unlike tooth-supported restorations, implant crowns connect directly to an osseointegrated implant fixture via an abutment, meaning fit precision and proper load distribution are critical to long-term success.

This overview walks through the laboratory fabrication process from start to finish, covering both the conventional and digital approaches.

Step 1: Receiving the Case

The process begins when the dental clinic sends the case to the laboratory. This may arrive as:

  • A physical implant-level impression with an impression coping, requiring the lab to pour a master cast with an implant analog.
  • A digital scan file (STL) captured with a scan body placed on the implant, which encodes the implant's position and angulation in 3D space.

Review the prescription carefully for implant system, connection type (internal hex, external hex, conical, etc.), and restoration type (cement-retained or screw-retained).

Step 2: Virtual or Physical Model Work

For digital workflows, the STL file is imported into CAD software. The scan body data is matched to a library of virtual implant components, establishing an accurate virtual model. For physical workflows, a master cast is poured using die stone, with the implant analog correctly positioned.

Step 3: Abutment Selection or Design

The next decision is whether to use a stock abutment (prefabricated, selected for the given emergence profile) or a custom abutment (designed to match the specific soft tissue contour of the patient).

Custom abutments can be milled from titanium or zirconia and allow precise control over the emergence profile, margin placement, and crown seating. For most aesthetic cases, a custom abutment is the preferred choice.

Step 4: Crown Design and Material Selection

With the abutment finalized, the crown is designed in CAD software. Key considerations include:

  • Occlusal clearance: Verify adequate space for the chosen material's minimum thickness recommendations.
  • Interproximal contacts: Design contacts that mirror natural tooth anatomy.
  • Emergence profile: The crown's contour as it exits the gumline should support soft tissue health.

Material selection depends on the position (posterior vs. anterior) and aesthetics required. Monolithic zirconia is a common choice for posterior implant crowns due to its strength and low chipping risk.

Step 5: Milling and Sintering

The designed crown (and any milled abutment) is manufactured via a 5-axis milling machine. Zirconia restorations then undergo sintering in a furnace to achieve full density and final dimensions. Post-sintering adjustments are made before finishing.

Step 6: Surface Finishing and Characterization

After milling and sintering, the restoration is polished and characterized. Options include:

  • Full-contour polish with diamond pastes for a glazed monolithic appearance
  • Staining and glazing to add surface color and texture
  • Cutback and layering with feldspathic porcelain for maximum aesthetics

Step 7: Screw Access Considerations (Screw-Retained Cases)

For screw-retained restorations, a screw access channel must be incorporated into the crown design. The channel location is determined by the implant angulation and should emerge in a non-aesthetic area (typically the central fossa for posteriors).

Quality Checks Before Delivery

Before the case ships, verify the following on the articulator or digital model:

  1. Passive fit on the analog/abutment
  2. Correct occlusal contacts in maximum intercuspation and lateral excursions
  3. No sharp margins or rough surfaces
  4. Accurate shade match (if applicable)

Thorough quality checks at the lab stage reduce chair time and remakes, strengthening your relationship with the referring clinician.