Seating Accuracy of Prefabricated Interim Crowns on Immediate and Delayed Implants: A Laboratory Study

To evaluate the seating accuracy of interim crowns for immediate restorations of immediate implants (I-Imps) and delayed implants (D-Imps) placed via static computer-assisted implant surgery (sCAIS).

A maxillary training model was modified by removing the central incisors and simulating a fresh extraction socket at one site and a healed ridge at the other site. An I-Imp was planned in the extraction socket and a D-Imp was planned in the healed site. The planned implants were used to design the sCAIS surgical template and interim crowns for immediate restoration of the implants. A total of 14 surgical models received sCAIS implants and then the interim crowns were placed. Subsequently, the models with the seated crowns were scanned by a laboratory scanner. The virtual planning model was superimposed against every surgical model to measure the vertical, horizontal, and proximal contact errors of each crown.

All the crowns were positioned more incisally than the planned crowns. This was significantly more noticeable for the D-Imp crowns (0.81 mm) than for the I-Imp crowns (0.55 mm). The two crown groups had similar horizontal errors (I-Imp = 0.35 mm, D-Imp = 0.36 mm). The D-Imp crowns had minimal proximal contact error (0.14 mm), but the I-Imp crowns had significantly greater proximal contact error (0.74 mm) in the form of open distal contacts. This pattern of error appears related to the relationship between the socket morphology and the planned implant position.

Prefabricated interim I-Imp crowns suffered from more errors that affected the proximal contact quality than D-Imp crowns. The observed deviation of the I-Imp crowns can be attributed to the socket morphology and its relation to the planned implant position. The deviations of the I-Imp crowns are clinically significant and would require clinical adjustments; therefore, caution is advised when using prefabricated interim crowns on I-Imps.