08 March 2024

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Comparison of different intraoral scanning strategies for inlay restorations

Lorenzo Breschi, Diego D’Urso

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Introduction: Since the introduction of intra-oral scanners (IOSs), various scanning strategies have been proposed. However, the optimal and most effective strategy is currently uncertain. In a recent in vitro study Salem et al. attempted to address this question by investigating the marginal and internal fit of CAD-CAM inlay restorations using the CS 3700 IOS. The study focused on the mesio-occluso-distal (MOD) ceramic inlay restorations.

Materials and methods: A total of 30 typodont maxillary right first molar teeth with previously prepared MOD inlay cavities were used (ANA-4 VCER; Frasaco). The inlay preparations underwent scanning using 3 different strategies: linear, wave, and S-figure scanning strategies. Each scan strategy group was scanned 10 times, resulting in 30 standard tessellation language (STL) files. To mitigate potential operator fatigue effects, a maximum of 5 scans were conducted on the same day. Subsequently, thirty restorations were milled from lithium disilicate CAD blocks (IPS e.max; Ivoclar AG) and cemented in their respective typodont-prepared inlay cavities. The marginal gap was set at 0 μm and the cement gap at 30 μm, beginning 1-mm away from the margin. Ultimately, a stereomicroscope was used to measure the marginal and internal gaps at predetermined points. 

Results: Statistically significant differences were observed for the marginal and internal fit of the inlay restorations (P<.001) across all scanning strategy groups. The findings from this in vitro study indicate that the linear group exhibited the lowest overall mean marginal and internal gap values, followed by the wave group. Conversely, the S-figure group showed the highest overall mean marginal gap values (P<.001).

Conclusions: The study revealed that the scanning strategy employed by the IOS significantly influenced the marginal and internal fits of the MOD ceramic inlay restorations. Specifically, the linear scan strategy demonstrated the superior marginal and internal fits when using the CS 3700 IOS for inlay restorations. 

Keywords: Intraoral scanners (IOSs); CAD-CAM; accuracy; strategies; inlay restorations

For more information: Mohamed M. Salem, Waleed A. Elmahy, Dina M. Nasr. Effect of different intraoral scanning strategies on the marginal and internal fit of CAD-CAM inlay restorations: An in vitro study. The Journal of Prosthetic Dentistry, 2023, ISSN 0022-3913,

Source: https://doi.org/10.1016/j.prosdent.2023.11.007.