Crown Workflow: Implant-Supported Crown: Cement-Retained

Important: This workflow starts after the implant has been properly checked for integration, typically 2-3 months after placement. The implant must pass the percussion test, sound solid, and have an x-ray taken to ensure no bone loss, non-integration, or fenestrations that might prevent proper restoration.

If the implant was placed using a two-stage protocol, a healing abutment (gingival former) should be seated, and then a healing time of at least 2 weeks between surgical exposure and impressions should be observed.

The healing period with proper abutments is critical to success. Use healing abutments that represent the size of the tooth being replaced at the gum line in its natural state. This allows the crowns to be contoured to match the patient’s existing natural teeth without requiring extensive porcelain work, resulting in more hygienic and esthetic restorations with properly formed sulcus before crown fabrication.

Capture impressions using one of the following methods:

• Open-tray traditional impression (see page 52)

• Closed-tray traditional impression (see page 56)

• Digital impression (see page 60)

Important: Open-tray traditional impression is the most recommended method for anything more than one implant. Open-tray impression techniques are more accurate according to the literature, but the impression posts must be splinted together using acrylic resin or light-cured material to prevent any positional discrepancy after the impression is poured. This is especially critical for all-on-four cases or multiple implant cases with 4, 5, or 6 implants, where any incorrectly positioned implant at impression time will cause the entire restoration to fail and require remaking.

Closed-tray traditional impression is not as accurate as open-tray methods, as proven in the literature. Several factors contribute to this, including potential movement if the impression tray isn’t held firmly during the procedure, which can create discrepancies and cause loose fit of the impression posts.

Digital impressions are effective as long as all necessary anatomy is captured and the impression post can be properly duplicated during the scanning procedure.

Remove the healing abutment and verify healthy, pink periimplant tissue with no signs of inflammation or recession around the implant platform.

Important: Proper sulcus shaping improves the chances of achieving a hygienic, esthetic implant crown and enhances long-term success by reducing the risk of peri-implantitis from bacterial infiltration around an improperly contoured crown that could cause bone loss.

Trial fit the crown and check margins, contacts, occlusion, embrasure form, and overall esthetics before final cementation.

Position the abutment onto the implant and finger-tighten the abutment screw, ensuring initial engagement and alignment with the internal connection.

Important: Taking a periapical radiograph is an essential step because improperly adjusted contacts can prevent the crown from seating correctly, potentially causing the mesial-distal seating configuration to be compromised.

This incomplete seating can lead to micro-leakage around the crown, peri-implantitis, and eventual implant loss. Taking a radiograph to verify proper seating is crucial for successful implant procedures.

Using a calibrated torque wrench, tighten the abutment screw to the manufacturer’s specified torque value, typically between 25-35 Ncm.

Pack teflon tape or cotton pellet into the abutment screw access hole to protect the screw head and allow future retrieval if needed.

Important: Cement volume control is critical when cementing crowns. Studies show dentists routinely use 20 times more cement than needed, resulting in 95% extrusion beyond margins. Excessive cement expression creates significant risks: improper cleaning around margins becomes difficult, and margin visibility is compromised during the procedure.

For implant crowns, this problem is particularly serious since margins are often subgingival, making excess cement removal nearly impossible. This retained cement acts as a bacterial reservoir, significantly increasing peri-implantitis risk and potential implant failure.

Best practices require applying only a thin film of cement inside the crown - just enough to create adequate retention while preventing marginal extrusion. Careful cement control and thorough removal protocol are essential for optimal retention, proper margin visualization, and long-term restoration success.

Apply a thin layer of cement along the internal walls of the crown, avoiding excess particularly near the margins. Seat the crown firmly onto the abutment by placing it under finger pressure, having the patient bite down, then positioning a wood stick between the occlusion to hold the crown in place as the cement sets.

Remove excess cement while still in the rubbery stage, using floss and scalers to ensure complete cleanup subgingivally and around all margins.

Check and adjust proximal contacts, emergence profile, and occlusal contacts in both centric and excursive movements using articulating paper.

Polish all adjusted surfaces thoroughly, as this step is critical - rough, unpolished contacts can wear away adjacent natural teeth and create spacing, while rough occlusal surfaces can abrade opposing natural teeth over time.