講演情報
[IO-1]Changes in the flexural strength and surface characteristics of different zones of multilayered translucent zirconia on aging
*Jeong-Min Ham1, Yu-Sung Choi1, Jong-Hyuk Lee1, Seung-Ryong Ha2, Myung-Sik Hong2, Jong-Min Lee1, Min-Woo Chu1, Hyo-Jung Kim1 (1. Department of Prosthodontics, College of Dentistry, Dankook University, 2. Department of Prosthodontics, Dankook University Jukjeon Dental Hospital)
[Objective]
IPS e.max ZirCAD Prime and Prime esthetic (Ivoclar Vivadent, Lichtenstein) has been introduced, which formed a transition zone by using gradient technology. However, some studies on how hydrothermal aging affects the mechanical and surface characteristics of the transition zones of multilayered zirconia are lacking.1 )This study aimed to evaluate the mechanical and surface characteristics of the transition zone in multilayered translucent zirconia after aging, compared to zones of different yttrium oxide content, and analyze the correlation between the 4-point bending flexural strength (4PBFS) and biaxial flexural strength (BFS) in each zone.
[Method]
Two conventional (L: 3Y-TZP of LT; M: 4Y-TZP of MT) and three multilayered (T: 5Y-TZP of MT Multi; P: 3Y/5Y-TZP of Prime; and E: 4Y/5Y-TZP of Prime Esthetic) IPS e.max ZirCAD blocks were used for mechanical and surface characteristics analyses. 525 disk-shaped specimens (diameter: 15.0 mm; thickness: 1.2 mm) and 300 bar-shaped specimens (length: 45.0 mm; width: 4.0 mm; thickness: 3.0 mm) were fabricated and polished on both sides according to ISO 6872:2015. The three specimen subgroups were subjected to different autoclave aging conditions (0, 5, and 10h) at 134oC under 0.2 MPa.2 )A graphical abstract of the materials and method is presented in Figure 1.
[Results and Discussion]
The flexural strength was highest in L, before and after aging. Zones with varying content of yttrium oxide showed consistent correlations between 4PBFS and BFS. The highest nanoindentation hardness and Young’s modulus was observed in T under all conditions, and the Vickers hardness values of L and P were lower than others. Aging led to an increased content of the monoclinic phase, higher surface roughness and defects, particularly in L and P.3) The mechanical and surface characteristics of different zones with varying yttrium oxide content must be considered when fabricating dental restorations from multilayered translucent zirconia blocks.
[References]
1) Inokoshi M, Liu H, Yoshihara K et al. Layer characteristics in strength-gradient multilayered yttria-stabilized zirconia. Dent Mater 2023;39:430-41.
2) Chevalier J, Cales B, Drouin JM. Low-temperature aging of Y-TZP ceramics. J Am Ceram Soc 1999;82:2150-4.
3) Lughi V, Sergo V. Low temperature degradation-aging-of zirconia: A critical review of the relevant aspects in dentistry. Dent mater 2010;26:807-20.
IPS e.max ZirCAD Prime and Prime esthetic (Ivoclar Vivadent, Lichtenstein) has been introduced, which formed a transition zone by using gradient technology. However, some studies on how hydrothermal aging affects the mechanical and surface characteristics of the transition zones of multilayered zirconia are lacking.1 )This study aimed to evaluate the mechanical and surface characteristics of the transition zone in multilayered translucent zirconia after aging, compared to zones of different yttrium oxide content, and analyze the correlation between the 4-point bending flexural strength (4PBFS) and biaxial flexural strength (BFS) in each zone.
[Method]
Two conventional (L: 3Y-TZP of LT; M: 4Y-TZP of MT) and three multilayered (T: 5Y-TZP of MT Multi; P: 3Y/5Y-TZP of Prime; and E: 4Y/5Y-TZP of Prime Esthetic) IPS e.max ZirCAD blocks were used for mechanical and surface characteristics analyses. 525 disk-shaped specimens (diameter: 15.0 mm; thickness: 1.2 mm) and 300 bar-shaped specimens (length: 45.0 mm; width: 4.0 mm; thickness: 3.0 mm) were fabricated and polished on both sides according to ISO 6872:2015. The three specimen subgroups were subjected to different autoclave aging conditions (0, 5, and 10h) at 134oC under 0.2 MPa.2 )A graphical abstract of the materials and method is presented in Figure 1.
[Results and Discussion]
The flexural strength was highest in L, before and after aging. Zones with varying content of yttrium oxide showed consistent correlations between 4PBFS and BFS. The highest nanoindentation hardness and Young’s modulus was observed in T under all conditions, and the Vickers hardness values of L and P were lower than others. Aging led to an increased content of the monoclinic phase, higher surface roughness and defects, particularly in L and P.3) The mechanical and surface characteristics of different zones with varying yttrium oxide content must be considered when fabricating dental restorations from multilayered translucent zirconia blocks.
[References]
1) Inokoshi M, Liu H, Yoshihara K et al. Layer characteristics in strength-gradient multilayered yttria-stabilized zirconia. Dent Mater 2023;39:430-41.
2) Chevalier J, Cales B, Drouin JM. Low-temperature aging of Y-TZP ceramics. J Am Ceram Soc 1999;82:2150-4.
3) Lughi V, Sergo V. Low temperature degradation-aging-of zirconia: A critical review of the relevant aspects in dentistry. Dent mater 2010;26:807-20.
