Comparative evaluation of different layer thickness in 3D-printed endodontic guides: an in vitro study

BACKGROUND: Guided endodontics has become essential for achieving minimally invasive and predictable access cavity preparation in advanced canal obliteration. However, the dimensional accuracy of endodontic guides depends on several 3D printing parameters, particularly layer thickness. This in vitro study evaluated the effect of two different layer thicknesses—50 μm and 100 μm—on the dimensional accuracy of stereolithographically printed endodontic guides. METHODS: Twenty-four endoguides were produced using a Form 3B+ printer (Formlabs, USA) with Biomed Clear Resin V2. Layer thickness was the only variable, while other printing parameters were standardized. After post-processing, specimens were scanned with a 3Shape E1 scanner, and STL files were superimposed using MeditDesign software. Dimensional deviations were calculated as root mean square (RMS, mm) values. Data were analyzed using an independent samples t-test (p < 0.05). RESULTS: Guides printed at 50 μm showed a mean RMS deviation of 0.066 ± 0.019 mm, while those printed at 100 μm exhibited 0.106 ± 0.035 mm (p = 0.002). Thinner layers resulted in significantly higher dimensional accuracy. CONCLUSION: Within the limitations of this in vitro study, reducing layer thickness significantly improved the dimensional fidelity of 3D-printed endodontic guides. However, although this difference was statistically significant, its clinical relevance should be interpreted with caution, as the absolute deviations observed in both groups were in the range of approximately 0.1 mm.