Marginal adaptation and fracture resistance of recent 3D printed high-performance polymer and CAD/CAM hybrid ceramic endocrown restorations and designs

The purpose of the current in vitro study was to evaluate and compare the marginal adaptation and fracture resistance of CAD/CAM VITA ENAMIC hybrid ceramic and, 3D printed Nanoksa G-PLUS high-performance polymer endocrown composite restorations constructed for endodontically treated teeth “EET”; considering two distinct coronal preparation designs: standardized anatomic and butt joint. A total of 40 freshly extracted intact human permanent mandibular molars were endodontically treated to receive endocrowns. Specimens were randomly divided into two equal groups “n = 20 each”: Group1 “G1” received 3D printed Nanoksa G-PLUS high-performance polymer, and Group2 “G2” received CAD/CAM VITA ENAMIC hybrid ceramic endocrown restorations. Each main group was further subdivided into two equal subgroups “n = 10 each” based on the coronal preparation design: standardized anatomic “G1A, G2A” and butt joint “G1B, G2B”. All endocrowns were adhesively luted with their respective manufacturer-recommended resin cements. Subsequently, all specimens underwent simulated aging through a chewing simulator and thermo-cycling (CSTC device, CS-4, SD Mechatronik, Germany). Marginal adaptation was quantitatively assessed by measuring the marginal gap distance using a USB Digital stereomicroscope (U500x Digital Microscope, Guangdong, China). Fracture resistance was determined using a universal testing machine (Model 3345; Instron Industrial Products, Norwood, MA, USA). Statistical analysis was performed using IBM SPSS Statistics (version 26), employing a two-way ANOVA followed by Tukey’s post-hoc tests, with significance set at P < 0.05. VITA ENAMIC specimens exhibited significant higher fracture resistance values; (p < 0.0001) and significant lower marginal adaptation (higher marginal gap values) than those of Nanoksa G-PLUS. Successful serviceability of recent endocrown restorations “Nanoksa G-PLUS and VITA ENAMIC” seems critically influenced by the material of construction and the technology of its fabrication. VITA ENAMIC endocrowns combined with anatomic preparation designs yielded the highest fracture resistance, while the Nanoksa G-PLUS endocrowns with butt joint preparation design exhibited the least fracture resistance of all subgroups. Understanding the performance characteristics of these advanced technology of restorative biomaterials, and adhesive bonding systems and preparation designs is crucial for optimizing the clinical outcomes and enhancing serviceability and longevity of endocrown restorations in posterior teeth.