Complete arch digital implant scan accuracy with screw-retained or snap-on scan bodies: A comparative in vitro study

Different scan body types have been reported to influence intraoral scanning accuracy. Stiff implant connections allow the use of snap-on scan bodies. However, data on the influence of scan body retention type are lacking.

The purpose of this in vitro study was to assess and compare the accuracy of complete arch digital scanning with that of screw-retained or snap-on scan bodies.

An edentulous mandibular master model with 4 conical connection analogs was digitized with an extraoral optical scanner to achieve a reference file. Seventy-six test scans were obtained with an intraoral scanner: 38 using screw-retained and 38 using snap-on scan bodies. The resulting 76 test files were aligned to the reference file with a best fit algorithm. Linear (ΔX, ΔY and ΔZ- axis), and angular deviations (ΔANGLE) were evaluated for each implant position (n=304). Three-dimensional (3D) deviation was calculated for each position according to the Euclidean distance (ΔEUC). Descriptive analysis and multivariable analysis were stratified considering scan body type and implant position (α=.05).

Considering ΔEUC, scan body type showed no significant difference (P=.097), while implant position was statistically significant (P<.001), with the left second premolar as the most critical and the right lateral incisor the most accurate. Considering ΔANGLE, the snap-on scan bodies were significantly better (P=.033). The implant position also resulted in statistically significant differences (P<.001) with the left second premolar being the most critical and the right lateral incisor as the most accurate.

Snap-on scan bodies showed comparable 3D and higher angular accuracy compared with screw-retained scan bodies. Tilted posterior implants were the least accurate and resulted in more critical positions, especially the most distal position to be recorded.