In-Vitro Investigation of the Microstructure, Elemental Analysis and Microhardness of Three Hybrid Resin Materials Used as Single-tooth restorations

Introduction: Technology constantly evolves, leading to the extensive usage ofCAD/CAM techniques (subtractive and additive manufacturing) to produce indirectrestorations. Nowadays, hybrid resin materials are commonly used to fabricate singletooth permanent restorations. Aim of the study: The current study evaluated andcompared three commercially available hybrid resin materials used for additive andsubtractive manufacturing of single-tooth permanent restorations. Methodology: 75bar-shaped specimens (14 x 2 x 2 mm) of 3 different hybrid resin materials were used inthis study and classified into 3 main groups. Lava Ultimate group (n=15), Vita Enamicgroup (n=15), and Flexcera Smile Ultra+ group (n=45). Flexcera Smile Ultra+ group wasfurther subdivided into 3 subgroups (n=15): Flexcera Smile Ultra+ A (0-degree printingangle), Flexcera Smile Ultra+ B (45-degree printing angle), and Flexcera Smile Ultra+C (90-degree printing angle). Specimens were investigated regarding microstructure,elemental analysis, and surface microhardness. One-way ANOVA and Kruskal-Wallistests were used for statistical data analysis. Results: Scanning electron microscopicimages showed typical hybrid resin materials with irregularly shaped fillers and differentsizes embedded in the resin matrix. Flexcera Smile Ultra+ specimens showed the higheststatistically significant carbon median value (42.65 wt.%). Lava Ultimate specimensshowed the highest statistically significant silicon and zirconium median values (27.15and 16.38 wt.%, respectively). Vita Enamic specimens showed the highest statisticallysignificant aluminum median value (9.15 wt.%) and surface microhardness mean value(205.02). Conclusions: The 3D printed material had higher resin content, lower fillercontent, and lower surface microhardness than CAD/CAM blocks. Specimens printedwith a 45-degree angle showed the best microhardness results.