Polymer-infiltrated ceramics (PICs) were prepared by monomer infiltration into porous ceramic preforms and subsequent polymerization by varying the silane concentration in the range of 1 to 20 wt% to investigate the effect of silane concentration on mechanical properties of the PICs. The optimized hardness, the strength and the fracture toughness of 99.5 Hv, 271±10 MPa and 3.74±0.11 MPa·m^1/2 were observed for the PICs having a silane concentration of 14%. However, they started to decrease when the silane content was raised more than 15%. The fracture mode was changed from intergranular to transgranular fracture across the ceramic particles with increasing the silane content. Most of the crack energy was dissipated by passing through the ceramic particles rather than through the polymer. The PICs exhibited no evidence of causing cell lysis or toxicity regardless of silane concentration, implying that the PICs are clinically suitable for use as dental restorations.

1~20 wt% 실란 처리한 다공성 세라믹 전성형체에 단량체를 침투하고 중합반응을 거쳐 고분자 침투 세라믹(PIC)을 제조하여 실란 농도별 PIC 기계적 물성을 조사하였다. 최적의 경도(99.5 Hv), 강도(271±10 MPa), 파괴인성(3.74±0.11 MPa·m^1/2)이 14 wt% 실란 처리한 PIC에서 관찰되었다. 하지만, 실란 농도가 15% 이상이 되면 기계적 물성은 감소하였다. 파괴거동은 실란 농도가 증가함에 따라 입계파괴에서 입내파괴로 변화하였다. 대부분의 균열 에너지는 세라믹 입자를 통과하면서 소진되었다. PIC는 실란 농도에 관계없이 세포 용해 또는 독성을 일으키지 않아 임상적으로 치과용 수복물에 적합하였다.

Keywords: polymer-infiltrated ceramics, silane-treatment, mechanical properties, cytotoxicity

Although tougher ceramics have been used in dentistry, all ceramic systems limit a widespread use due to the brittleness and higher hardness.^1-8 It is necessary to develop a dental material with similar mechanical properties to that of natural human enamel and dentin. Nowadays, the development of dental esthetic materials has switched to more polymer-based resin composites.⁸ Ceramics and polymers are highly suitable for the synthesis of composites with tailored mechanical properties due to their synergic combination of excellent strength and flexibility, which can be used for dental restorations.^8-11 Unlike conventional processing of dispersion of ceramic particles in a polymer matrix, a stabilized interpenetrating network materials can be achieved by infiltration of monomers in a porous ceramic matrix, followed by polymerization. By replacing loose ceramic particles in the polymer matrix by a stable ceramic matrix, higher strength, elastic modulus, toughness, and better wear resistance are possible.^8-13
The ceramic inlays can be fabricated by using a CAD/CAM machine at the chairside in the dental surgery. Especially, the prefabricated leucite-reinforced glass ceramic blocks were available for milling using a CAD/CAM machine because of easy manipulation, excellent fit, and aesthetics.¹³ In addition, the same chemical composition of porcelain and glass ceramic made it possible to perform conventional finishing processes such as add-ons, staining and glazing. However, their mechanical properties of the glass ceramics were not suitable for use even in a single crown.^8,13 In the present study, the polymerinfiltrated ceramic composites (PICs) are prepared to improve the mechanical properties by modifying the ceramic matrix surface with a silane coupling agent, (3-(trimethoxysilyl)propyl methacrylate), having the same active function as the resin before the monomer infiltration into the porous ceramic matrix to improve the interface strength between the organic polymer and the inorganic ceramic.^9,14 The silane coupling agents are adhesion promoters to chemically unify dissimilar materials used in dentistry.¹⁴ The PIC, a hybrid block for milling, can be used as the material of choice for dental inlay materials. Mechanical properties, cytotoxicity and cell proliferation of the PICs were examined.