A Fatigue Toughness and Polymerization Shrinkage of Post-cure Heat Treated Composite Resins

광중합 복합레진에 대한 가열처리 피로내성 및 중합수축에 미치는 영향

This study was conducted to evaluate whether the fatigue toughness of visible light cured composite resins could be improved and how much percentage of polymerzation shrinkage could be affected by additional heat treatment. 7 materials were investigated for this study: P-50, Lite-fil CR inlay, Pekafil, Clearfil CR inlay, Clearfil photo posterior, Z -100 and Progress. Diametral tensile strengths and linear shrinkages of composite resins were taken under visible light cured and additional post-cure heated condition and compared each other. A fatigue toughness of above materials was evaluated by measuring diametral tensile strength after they were repeatedly loaded with 120kgf/$cm^2$ up to 3000 cycles. The results obtained were as follows : 1. When composite resins were cured just by visible light, Lite fil CR inlay, Z -100 and Progress showed respectively higher diametral tensile strength than the other materials. Clearfil CR inlay, Clearfil photo posterior and Progress exhibited strong fatigue toughness compared to P-50 and Pekafil. 2. Post-cure heat treated composite resins had higher diametral tensile strengths than visible light cured composite resins at fatigue toughness test as well as no fatigue toughness test. 3. When Composite resins were additionally polymerized by post-cure heat treatment, P-50 showed weak fatigue toughness, on the contrary, Clearfil CR inlay, Z-100, Progress showed strong one. 4. When composite resins were cured just by visible light, percentage of polymerization linear shrinkage was the lowerest in Clearfil CR inlay, followed by, in ascending order, Clearfil photo posterior, Lite-fil CR inlay, Progress, Pekafil, P-50, and Z-100. In the case of post- cure heat treated composite resins, percentage of linear shrinkage was the lowest in Clearfil photo posterior, followed by, in ascending order, Lite-til CR inlay, Clearfil CR inlay, Progress, P-50, Pekafil and Z-100. 5. Percentage of polymerization linear shrinkage was greater in the post-cure heat treated composite resins than in the visible light cured composite resins and linear shrinkage increased significantly in Pekafil, Clearfil CR inlay, and Clearfil photo posterior between at the visible light cured and at the post-cure heat treated condition. The above results is saying that additional post-cure heat treatment on the composite resins for posterior restoration is able to affect on improvement of strength and fatigue toughness and lead to increase polymerization of composite resins.