Trueness and precision of milled and 3D printed root-analogue implants: A comparative in vitro study

Objectives: The present study aimed to evaluate the accuracy (trueness and precision) of titanium and zirconia multi-rooted root analogue implants (RAIs) manufactured by milling and 3D-printing. Methods: A multi-rooted RAI was designed based on a mandibular second molar segmented from cone-beam computed tomography (CBCT). The manufactured RAIs were divided into four groups: 3D-printed titanium (PT) and 3D-printed zirconia (PZ) (n=10 each), as well as milled titanium (MT) and milled zirconia (MZ) (n=5 each). The specimens were scanned with a high-precision scanner, and the scanned data were imported into 3Dmeasurement software to evaluate the precision and trueness of each group. Root mean square (RMS) deviations were measured and statistically analysed (One-way ANOVA, Tukey's, p <= 0.05). Results: PZ showed the highest precision with RMS value of 21 +/- 6 mu m. Nevertheless, there was no statistically significant difference in precision among the other groups. Regarding trueness, MZ showed the highest trueness with RMS value of 66 +/- 3 mu m, whereas MT showed the lowest trueness result. Inspection sections showed that MT had significantly high RMS deviation in the furcation area (612 +/- 64 mu m), whereas PZ showed significantly high RMS deviation at the apical area (197 +/- 17 mu m). Conclusions: The manufacturing process significantly influenced the RAI accuracy. PZ exhibited the highest precision, whereas MZ exhibited the highest trueness, followed by PT. Finally, our results suggest that 3D-printing can reproduce concave surfaces and less accessible areas better than milling. Clinical Significance: Milled and 3D-printed RAIs showed promising results in terms of precision and trueness. However, further clinical research is needed to advocate their use as immediate implants. Additionally, the inherent volumetric changes of the various materials during manufacturing should be considered.