Effect of different intraoral scanning strategies on the marginal and internal fit of CAD-CAM inlay restorations: An in vitro study

<bold>Statement of problem: </bold>Whether the scanning strategy of intraoral scanners (IOSs) affects the accuracy of the digital recording for an indirect ceramic inlay restoration is unclear. Furthermore, which strategy would be optimal and most effective is uncertain. <bold>Purpose: </bold>The purpose of this in vitro study was to evaluate the impact of 3 different scanning strategies using the Carestream CS 3700 IOS on the marginal and internal fit of a mesio-occluso-distal (MOD) ceramic inlay restoration. <bold>Material and methods: </bold>A typodont master model (ANA-4 VCER; Frasaco) was used with a standardized preprepared MOD inlay maxillary first molar typodont tooth (ANA-4 ZP16 CER99-008; Frasaco) (N=30). These inlay preparations were scanned with the CS 3700 IOS using 3 different scanning strategies: linear, wave, and S-figure scanning strategies. Each scan strategy group was scanned 10 times for all groups to obtain 30 standard tessellation language (STL) files. Thirty restorations were milled from lithium disilicate CAD blocks (IPS e.max; Ivoclar AG) and cemented into their typodont-prepared inlay cavities. A single examiner used a stereomicroscope to measure the marginal and internal gaps at the predetermined points. A 1-way ANOVA was used for the statistical analysis, followed by the Tukey post hoc test with Bonferroni adjustment. All tests were 2-tailed (alpha=.05). <bold>Results: </bold>All scanning strategy groups demonstrated statistically significant differences for the marginal and internal fit of the inlay restorations (P<.001). Overall, the linear scanning strategy showed the lowest mean marginal and internal gap values (29.2 +/- 3.6 <mu>m and 39.0 +/- 6.4 mu m), followed by the wave scanning strategy, which had comparable mean marginal and internal gap values: 49.1 +/- 3.6 mu m and 48.2 +/- 6.0 mu m, respectively. The S-figure scan strategy had the highest mean marginal and internal gap values: 50.2 +/- 12.6 mu m and 71.3 +/- 7.7 mu m, respectively. <bold>Conclusions: </bold>Inlay restorations scanned by the linear scan strategy had the best marginal and internal fit when scanned with the CS 3700 IOS.