Title: Load-bearing Properties of Lithia-based Glass-ceramic for Minimally Invasive Restorations
Lahari Bhavishetty (Presenter)
New York University
Marina Kaizer, New York University
Minglei Zhao, New York University
Eric Cheng, New York University
Yu Zhang, New York University
Objectives: To improve the application load-bearing capacity of lithium-disilicate (LiDi) glass-ceramic via intaglio surface resin infiltration.
Methods: Discs of LiDi (HT-A2 IPS e.maxCAD, Ivoclar Vivadent) were cut from CAD/CAM blocks (ø12×1 mm) and ground to 15 µm finish. Acid etching (5% HF) was performed for 20, 60, or 120 s (n=10/group). A control, not etched group was included. A second batch of samples was acid etched for 120 s followed by resin infiltration: a coupling agent (Monobond Plus, Ivoclar) was applied and kept in vacuum for 10 min, then heat-treated at 140°C for 2h; after cooling, a thin layer of fluid resin (mix of low molecular-weight monomers) or viscous resin (UDMA, Sigma Aldrich) was applied and kept in vacuum for 10min; Light curing for 1 min was performed for the fluid resin. High-temperature-pressure polymerization (200°C for 1h) was used for UDMA. Color coordinates (CIELab) were measured on plate specimens over white and black backgrounds with a coupling agent (glycerol) to calculate the translucency parameter (TP). Characterization of microstructure and composition was performed with SEM and XRD. Load-bearing capacity was determined by piston-on-3-balls biaxial flexural test.
Results: A trend of reduction in load-bearing capacity was observed with increasing etching times. HF acid etching not only erodes the glass matrix, but also reduces the crystal content on the surface, as observed by SEM-BSE and XRD. The viscous UDMA lacked the ability to infiltrate the porosity created by acid etching, reducing both the TP (36 ±3) and the load-bearing (237 ±37 N). The opposite effect was observed when the fluid resin was used, with the infiltrated group showing load-bearing (290 ±13 N) significantly higher than the etched counterpart 120s (267 ±7 N). TP was not affected by fluid resin infiltration or etching time (~44 ±1).
Conclusions: The intaglio surface resin infiltration can enhance load-bearing capacity of LiDi.