Background and objectives: There has been a lack of studies regarding the marginal seal and structural durability of a novel temporary crown system (Hi-tempo) manufactured from a polylactic (PLA) based resin thermoplastic material especially in terms of cyclic loading. Therefore, the purpose of this pilot study was to investigate the efficiency of this novel temporary crown system’s (Hi-tempo) marginal seal and structural durability in terms of cyclic loading. Methods: A crown preparation was duplicated in bovine teeth (n =15) using a copy mill machine. The specimens were divided into three groups and temporary crowns were fabricated that consisted of: control group, Luxatemp (bis-acrylic), Hi-tempo crown, PLA based and Hi-tempo window type crown, PLA based with resin cusps. Marginal dimensional change was measured before and after cyclic loading with a 93.36 N force, 0.63 HZ, for 45360 cycles (stimulating 21 days in vivo) in water pigmented with a red dye. The marginal change was statistically analysed and the surface roughness was analysed using scanning electron microscopy (SEM). Results: Statistical significance (p<0.05) was found in the marginal changes of the control versus the Hitempo window and the Hi-tempo groups. SEM analysis revealed that the control crowns, had a much rougher surface with micro-cracks compared to PLA based crowns which had homogenous surfaces. All the specimens showed leakage of the red dye into the internal fitting surfaces of the crowns. Conclusions: The novel system showed promising and comparable results in terms of structural durability and marginal seal compared to the conventional system.

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