Effect of Scanner Tip Size and Edentulous Arch Length on Intraoral Scan Accuracy in Kennedy Class I Cases

This in vitro study aimed to investigate the effect of scanner tip size on the accuracy of Kennedy Class I mandibular arch scans, using two different IOSs both featuring interchangeable tip sizes.

A Kennedy Class I mandibular typodont model was digitized with a laboratory scanner (3Shape E4) to obtain a reference STL file. Two different intraoral scanners (Mediti900 and Dexis3800W) each equipped with interchangeable tip sizes (large/medium) were used for the experimental scans. 10 digital scans per each group with a total of 40 scans were performed (n=10). The experimental and reference STL files were superimposed using Geomagic Design X software. Root mean square (RMS) and interquartile range (IQR) values were calculated for four predefined regions: anterior (A), short-span edentulous (SE), long-span edentulous (LE), and total (T).

Statistically significant differences were found among scanners, tip sizes and scanned areas (p<0.001). Scans obtained with larger tips showed lower RMS and IQR values, indicating improved trueness and precision (p < 0.001). Medit demonstrated significantly lower RMS values in the posterior edentulous areas whereas Dexis performed significantly better in the anterior areas (p < 0.001).

Within the limitations of this in vitro study, both Medit i900 and Dexis IS 3800W provided clinically acceptable accuracy for Kennedy Class I mandibular arches. Accuracy was influenced by scanner type, tip size, and scanned area. Larger tips improved accuracy in edentulous regions, whereas smaller tips provided advantages in narrow areas.