In vitro study of compressive fracture strength of Empress 2 crowns cemented with various luting agents
김민호, 양재호, 이선형, 정헌영, 장익태,
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김민호 ( Kim Min-Ho ) - 서울대학교 치과대학 치과보철학교실
양재호 ( Yang Jae-Ho ) - 서울대학교 치과대학 치과보철학교실
이선형 ( Lee Sun-Hyung ) - 서울대학교 치과대학 치과보철학교실
정헌영 ( Chung Hun-Young ) - 서울대학교 치과대학 치과보철학교실
장익태 ( Chang Ik-Tae ) - 서울대학교 치과대학 치과보철학교실
KMID : 0362420010390030260
Abstract
All-ceramic restorations have had a more limited life expectancy than metal ceramic restorations because of their low strength. Their relatively lower strength and resistance to fracture have restricted the use of all-ceramic crowns to anterior applications where occlusal loads are lower. But there has been increasing interest in all-ceramic restorations because patients are primarily concerned with improved esthetics. Many efforts have been made to improve the mechanical properties of dental ceramics. This study was designed to elucidate the influence of the luting agent on the strength of the Empress 2 crown (staining technique) cemented on human teeth. Seventy extracted human permanent molar teeth were chosen. Teeth were prepared for Empress 2 crowns with milling machine on a surveyor. A dental bur was placed in the mandrel that was positioned so that the long axis of the bur was perpendicular to the surveyor base. Dimensions of the Empress 2 crown preparation were 6degree taper on each side, 1.5+/-0.1mm shoulder margin, and 4mm crown height. The luting cements used in this study were as follow: 1. Uncemented 2. Zinc phosphate cements (Confi-Dental) 3. Conventional glass ionomer cement : Fuji 1(GC) 4. Resin-modified glass ionomer cements : Fuji plus(GC) 5. Adhesive cements : Panavia F(Kuralay), Variolink II(Vivadent), Choice (Bisco). Fracture test using Instron : The crowns were loaded in compressive force to evaluate the effect of these cements on the breaking strength of these all-ceramic crowns. A steel ball with a diameter of 4mm was placed on the occlusal surface and load was applied to the steel ball by a cylindrical bolt with a crosshead speed of 0.5mm per minute until fracture occurred. The fractured surface was examined using Scanning Electron Microscopic Image (SEM) to discover the correlation between fracture strength and bonding capacity. Within the limitation of this in vitro study design, the results were as follows : 1. Cementations significantly increased the fracture resistance of empress ceramic crowns compared to control. Uncemented(206.9 N); ZPC(812.9N); Fuji 1(879.5N); Fuji Plus (937.7N); Choice (1105.4N); Variolink II(1221.1N); Panavia F(1445.2N). 2. Resin luting agent, treated by a silane bond enhancing agents, yielded a significant increase in fracture resistance. In some of the Panavia F group, a fracture extended into dentin. 3. According to SEM images of fractured Empress crowns, the stronger the bond at both interfaces (crown and die), the more fracture strength was acquired.
키워드
Fracture strength; Empress 2 crown; Human teeth; Cementation method
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