Accuracy of intraoral scanbodies regarding manufacturing tolerances.

Objectives: Intraoral scanners are gaining more and more importance, especially for implant supported fixed denture prosthesis (FDP). However, their application does not warrant passive intraoral fit of the final restoration. Most studies available investigated the scanning path but there are only few investigations analyzing the accuracy of intraoral scanbodies (ISB). The aim of the present study was to assess the manufacturing tolerances of three different intraoral scanbodies with a multisensor coordinate measuring machine with x-ray computed tomography and to investigate their influence of the transfer of the intraoral implant position.

Methods: Three different ISB (H1410, MEDENTiKA, Hügelsheim, Germany/H9.S3D4.150, nt-trading, Mannheim, Germany/cara H10/20, Kulzer, Hanau, Germany) were measured by a multisensor coordinate measuring machine with x-ray computed tomography Tomoscope S (Werth Messtechnik, Gießen, Germany) and exported as a stl-file. Length, diameter and angle deviations between the measurements and the respective CAD data provided by the manufacturer were compared (gom Inspect, Braunschweig, Germany). All data were subjected to an univariate ANOVA and analyzed by means of pairwise comparisons (p-value<0.05). Statistical analysis was performed with SPSS 22.0 (IBM, Chicago, USA).

Results: Length deviations ranged from 0.13±2.9μm (Kulzer) to 22.08±3.0μm (MEDENTiKA). Diameter deviations ranged from 6.48±0.8μm (Kulzer) to 10.92±1.4μm (NT-Trading). Angle deviations ranged from 0.06±0.03° (Medentika) to 0.13±0.11° (NT-Trading). There were significant differences for length and diameter deviations between the different ISB.
Conclusions: Three-dimensional deviations results in an inaccurate transfer of the intraoral implant position. This could be responsible for inaccurate fitting positions of FDPs. Referring to the investigated ISB, small length and high angle deviations leads to higher divergences for the intraoral to extraoral implant position transfer. ISB manufacturing tolerances should be improved to achieve a higher accuracy in intra- to extraoral transfer. The used x-ray is suitable for precise measurements.