Impact of partial edentulous space on the full-arch intraoral scan data precision

Background

The digital data acquisition with an intraoral scanner or a laboratory scanner has been widely used in the field of clinical implant dentistry. The scanning speed and accuracy of intraoral scanners are clinically acceptable in case of partial arch condition. However, in terms of full-arch scanning of implants or abutments for the treatments of partial edentulous cases, the location or width of edentulous space may affect the precision of full-arch intraoral scan data.

Aim/Hypothesis

The goal of this in-vitro test is to evaluate the impact of partial edentulous space on the precision of full-arch scan data using an intraoral scanner with three-dimensional (3D) superimposition analysis.

Material and Methods

Full-arch dentiform cases with four different partial edentulous spaces were used+ case 1 – unilateral, two missing posteriors (#15, 16) + case 2 – bilateral, five missing posteriors (#15,16,24,25,26) + case 3 – five missing anteriors (#11,12,13,21,22) + case 4 – four missing anteriors and two missing posteriors (missing- #11,12,21,22,25,26). A full-arch dentiform with no edentulous space was used as a reference case. For each dentiform, six full-arch scan data were obtained using an intraoral scanner by a single experienced operator. The scanning was performed according to the manufacturers’ instructions, started with an occlusal surface of a second molar. For the precision analysis, every scan data of each dentiform was cross-compared and superimposed using best-fit alignment to evaluate 3D surface deviation. The root mean square estimates values (RMSEs) were calculated and statistically analyzed one-way ANOVA. The level of statistical significance was 0.05.

Results

The means and standard deviations of RMSE values of each dentiform case were as follows- 58 ± 21 μm (case 1) + 100 ± 45 μm (case 2) + 107 ± 49 μm (case 3) + 116 ± 53 μm (case 4) + and 52 ± 15 μm (reference case). The full-arch scan data with no edentulous space (reference case) showed the lowest mean RMSE value. The full-arch scan data with long-span or multiple edentulous spaces (cases 2, 3, and 4) showed higher 3D surface deviation than the data with reference case, with a statistical significance (all, P < 0.05). However, the full-arch scan data with a short-span edentulous space (case 1) showed similar RMSE value with the fully dentate arch scan (P > 0.05).

Conclusion and Clinical Implications

Within the limitations of this in-vitro test, the condition of the partial edentulous space significantly influenced the precision of the full-arch scan data acquired by an intraoral scanner. The full-arch scan data with no edentulous space showed the highest level of precision. A restorative dentist should consider possible distortion of full-arch intraoral scan data in the presence of long-span or multiple partial edentulous spaces.