Influence of prosthesis type and intraoral scanner-based extraoral scanning protocol on the passive fit of CAD-CAM verification devices.

Abstract

Purpose: To evaluate the impact of different complete-arch digital scanning techniques and prosthesis types on the passive fit of computer-aided design and computer-aided manufacturing (CAD-CAM) verification devices.

Materials and methods: Two different maxillary master casts with four multi-unit abutment (MUA) implant analogs (FP-1 and FP-3 prosthesis types) were used as the basis for fabricating verification devices through two impression techniques (OptiSplint and RevEX). Group 1 utilized digital scans of splinted scanbodies reinforced with a light-polymerizing acrylic resin and metal mesh on the FP-1 cast (OptiSplint technique), Group 2 employed the same impression technique as Group 1 on the FP-3 cast, Group 3 applied digital scans of reverse scanbodies connected to a passively fitting interim prosthesis on FP-1 cast (RevEX technique), and Group 4 used the same impression technique as Group 3 on FP-3 cast. A total of 40 milled verification devices were fabricated, with 10 devices allocated to each group. The misfit of verification devices was assessed using visual inspection, tactile sensation, and a one-screw test, with any disagreements between the two primary examiners resolved by a third evaluator. Agreement between the clinicians was assessed using Cohen's kappa statistics and percent agreement. The percentage of misfits was calculated for each group and compared between groups using Fisher's exact tests (α = 0.05).

Results: The misfit analysis showed the lowest misfit (10%) in Group 1 (OptiSplint-FP1), followed by Groups 3 (RevEX-FP1) and 4 (RevEX-FP3) at 20%, and the highest (40%) in Group 2 (OptiSplint-FP3), with no significant differences between groups by Fisher's exact tests (p > 0.05). Odds ratios indicated six times higher misfit odds for FP-3 than FP-1 with OptiSplint, no difference for FP-1 versus FP-3 with RevEX (odds ratio = 1.0), and lower odds with RevEX compared to OptiSplint under FP-3 conditions (odds ratio = 0.375). Inter-examiner agreement was strong, with 90% concordance and a Kappa statistic of 0.66, demonstrating substantial consistency.

Conclusion: OptiSplint is preferable for FP1 cases, whereas RevEX suits FP3 cases when intraoral-scanner-based extraoral workflows are used. Despite these recommendations, misfits occurred in every group, suggesting that a verification cast may be prudent when adopting these newer scanning approaches. Clinicians should consider fabricating an additional verification cast with splinted scanbodies or a clinically satisfactory interim implant prosthesis. This cast can confirm implant positions whenever modern scanbodies such as OptiSplint or RevEX are incorporated into the workflow.