Xuehua Tang1, Chengzhong Tang2, Han Su2, Huinan Luo2, Takashi Nakamura3, Hirofumi Yatani3. 1. Department of Stomatology, Jinling Hospital, Nanjing University School of Medicine, Nanjing 210002, China; Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan. Electronic address: t-xuehua2008@hotmail.com. 2. Department of Stomatology, Jinling Hospital, Nanjing University School of Medicine, Nanjing 210002, China. 3. Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan.
Abstract
OBJECTIVES: We evaluated the effects of repeated heat-pressing on the mechanical properties and microstructure of IPS e.max Press. METHODS: A total of 20 specimens were fabricated including 10 heat-pressed once and another 10 heat-pressed twice. The density, porosity, and surface roughness (Ra) were evaluated. Three-point flexural strength following the ISO 6872 and Vickers hardness were measured, and fracture toughness (KIC) was calculated. Specimens were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). RESULTS: Compared to a single heat-press treatment, the density decreased and porosity increased after two heat-pressing events. A significant difference in density was observed. The flexural strength, Vickers hardness and fracture toughness significantly decreased after two heat-pressing events. The XRD patterns show that the intensity of the crystalline phase better corresponds to lithium disilicate (Li2Si2O5) after two heat-presses than only one. The SEM images detailed the interlocking microstructure of rod-shaped Li2Si2O5 crystals after one heat-press. These became oriented after two heat-presses, and the crystal size became larger. CONCLUSION: This study showed that repeated heat-pressing was detrimental to the density, porosity, strength, hardness, and toughness of IPS e.max Press.
OBJECTIVES: We evaluated the effects of repeated heat-pressing on the mechanical properties and microstructure of IPS e.max Press. METHODS: A total of 20 specimens were fabricated including 10 heat-pressed once and another 10 heat-pressed twice. The density, porosity, and surface roughness (Ra) were evaluated. Three-point flexural strength following the ISO 6872 and Vickers hardness were measured, and fracture toughness (KIC) was calculated. Specimens were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). RESULTS: Compared to a single heat-press treatment, the density decreased and porosity increased after two heat-pressing events. A significant difference in density was observed. The flexural strength, Vickers hardness and fracture toughness significantly decreased after two heat-pressing events. The XRD patterns show that the intensity of the crystalline phase better corresponds to lithium disilicate (Li2Si2O5) after two heat-presses than only one. The SEM images detailed the interlocking microstructure of rod-shaped Li2Si2O5 crystals after one heat-press. These became oriented after two heat-presses, and the crystal size became larger. CONCLUSION: This study showed that repeated heat-pressing was detrimental to the density, porosity, strength, hardness, and toughness of IPS e.max Press.
Authors: Larissa Natiele Miotto; Mariana de Oliveira Carlos Villas-Bôas; Edgar Dutra Zanotto; Eduardo Bellini Ferreira; Laiza Maria Grassi Fais; Lígia Antunes Pereira Pinelli Journal: J Mater Sci Mater Med Date: 2021-08-28 Impact factor: 3.896
Authors: Tariq S AbuHaimed; Saeed J Alzahrani; Sami A Farsi; Lulwa E Al-Turki; Maher S Hajjaj Journal: Materials (Basel) Date: 2022-09-30 Impact factor: 3.748