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

Purpose: Evaluation of seating accuracy of interim crowns for the immediate restoration of immediate implants (I-Imp) and delayed implants (D-Imp) placed via static computer-assisted implant surgery (sCAIS).

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

Results: 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 the I-Imp crowns (0.55 mm). The 2 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.

Conclusions: Prefabricated interim I-Imp crowns suffered from greater errors that affected the proximal contact quality than DImp 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 will require clinical adjustments. Thus, caution is needed before routine use of prefabricated interim crowns on I-Imp.