The Effect Of Crystallization Temperature On The Flexural Strength Of Lithium Disilicate Glass-Ceramics

Abstract

Objective: To assess the impact of different crystallization protocols on the flexural strength of Amber Mill CAD glass-ceramics. Materials and Methods: Amber Mill CAD ceramic blocks (HASSBIO America Inc., Fairfax, VA) of a known Vita Classic shade (A1) shade were selected for testing against control lithium disilicate CAD blocks (IPS e.max CAD, Ivoclar Vivadent, Amherst, NY) of the same shade. Four different translucencies were selected for Amber Mill CAD blocks and were as follows: HT, MT, LT, and MO. Two different translucencies were selected for IPS e.max CAD blocks and were as follows: HT and LT. The partially crystallized blocks were sectioned and placed into 6 groups for each temperature protocol for a total of 36 samples for Amber Mill CAD and 19 samples for IPS e.max CAD. The size and dimensions of the sectioned samples were as follows: thickness =1.5mm, width = 4mm, and length = 14mm. Four different crystallization protocols at various temperatures, as recommended by the manufacturer, were used with Amber Mill CAD blocks, and two different crystallization protocols were used with IPS e.max CAD blocks following manufacturer recommendations. The samples of each group were subjected to 3-point bending test following the ISO 6872:2015 recommendations. Results: A two-way ANOVA statistical analysis method was used to interpret the collected data in the first objective. A one-way ANOVA and multiple pairwise-comparison were used to interpret the collected data in the second objective. The mean averages of maximum flexural strength for Amber Mill CAD samples were 269.54 MPa, 280.10 MPa, 277.55 MPa, and 254.16 MPa for the following translucencies: HT, MT, LT, and MO, respectively. The mean averages of maximum flexural strength for the control IPS e.max CAD samples were 302.99 MPa and 283.49 MPa for the following translucencies: HT and LT, respectively. Comparisons were conducted between all four different crystallization temperatures of Amber Mill CAD ceramics (HT, MT, LT, MO). Conclusion: There was no significant difference in the mean average of flexural strength between the HT and LT groups of the Amber Mill CAD blocks when compared to the control HT and LT groups of IPS e.max CAD blocks (p>0.05). When comparing the four crystallization protocols of Amber Mill CAD samples for flexural strength, there was no statistical difference between them (p>0.05). Therefore, clinicians can use all recommended crystallization protocols without impacting overall strength.