Accuracy of occlusal splints printed in different orientations by liquid crystal display technology: an in vitro...

To evaluate the accuracy of occlusal splints printed in different orientations by liquid crystal display technology.

An occlusal splint was digitally designed, and additively manufactured using an LCD printer (Phrozen Sonic 4k, Phrozen) at three orientations relative to the printer building plate: 0, 45, and 70 degrees (n=10). The 3D-printed occlusal splints were digitised using a desktop scanner, resulting in experimental meshes. The meshes were analysed in a metrology software program, comparing the experimental ones with the initially designed occlusal splint (trueness) and each other within the same group (precision). The discrepancies were shown in a colour map and the root mean square indicated the magnitude of the total discrepancy between the meshes. Kruskal-Wallis test was used (α=0.05) followed by post-hoc Dunn's test.

There was no statistical difference in trueness among the groups (P=0.086); however, splints printed at 70 degrees showed better precision compared to those printed at 0 (P<0.001) and 45 degrees (P<0.001). The splints printed at 0 and 45 degrees exhibited a similar discrepancy pattern, with highest values concentrated in the posterior segment-positive on the buccal surface and negative on the lingual surface of molars. In contrast, splints printed at 70 degrees had highest discrepancy values in both anterior and posterior segments, with an inverted pattern on molars.

The accuracy of occlusal splints was affected by the different orientation in terms of precision, with 70 degrees resulted in highest precision compared to 0 and 45 degrees. No difference was found in terms of trueness. Higher discrepancies were found located in molars and incisal edge of anterior teeth.

3D-printing using LCD technology stands out for its affordability and good resolution, however the optimal printing angle remains unclear. Vertical positioning allows more objects to fit on the printer building plate, while horizontal positioning reduces print time. According to literature, for DLP printers, a 0-degree angle provides good accuracy for occlusal splints, whereas a 90-degree angle results in lower accuracy. This study found that for LCD printers, 0, 45, and 70 degrees had similar trueness, with 70 degrees offering the highest precision. Thus, vertical positioning at 70 degrees can be a safe choice for the accuracy of occlusal splints printed on LCD technology.