The effect of film thickness and surface texture on the resistance of cemented extracoronal restorations to lateral fatigue loading

Purpose: The aim of the present study was to assess the effect of cement-fi lm thickness and surface texture (roughness) on the resistance of cemented crowns to dynamic lateral loading. Materials and Methods: Crown and abutmen t analogues were cemented using zinc-oxide-eugenol, zinc-phosphate, glass-i onomer, and composite cements. The space left for the cement lute was 0.02, 0.05, 0.1, 0.2, and 0.5 mm. The 3 degrees of surface texture subjected to investigation were (1) polished with up to 4,000-grit paper, (2) sanded usi ng a 1,000-grit paper, and (3) sandblasted with 50-mu m aluminum oxide. Tes ting was conducted according to the staircase procedure. The specimens were subjected to rotational fatigue loading until the cement bond failed or th e components reached 1,000,000 stress cycles. Results: The results showed t hat the relation between cement thickness and resistance to dynamic lateral loading is hyperbolic. For the zinc-oxide-eugenol, the zinc-phosphate, and the glass-ionomer cements increasing surface texture had a moderate effect . For composite cement, sandblasting doubled the resistance to dynamic late ral loading. For both parameters tested (cement thickness and surface textu re), the ascending order of resistance was: zinc-oxide-eugenol, zinc-phosph ate, and glass-ionomer cements. Crowns cemented with composite cement prese nted the highest resistance to dynamic lateral loading. Conclusion: Within the confines of the present experimental design, it is concluded that (1) d ecreasing the width of the cement layer increases the resistance to dynamic lateral loading, and (2) texturing the surface of the abutment and the res torations as after sandblasting increases the resistance to dynamic lateral loading.