Abstract

Dental luting cements are important materials in securing FPD to abutment teeth. During the cementation process of FPDs finger force is applied to fully seat the restoration in place. Normally the dentist maintains force on the restoration until the luting cement sets, however, little is known as to the consistency of force application over time. The aim of this study was to compare the force applied by dentists during cementation of all-Zirconia FPD manufactured by CAD CAM and to investigate the effect that this has on the seating and fit of the cemented FPD. Two plastic teeth mounted in Frasaco jaws (teeth 24 and 26 were prepared for a three unit all ceramic (zirconia) bridge to replace tooth 25. Each tooth was prepared in the laboratory with a high-speed hand piece and coolant to a pre-set standard. Ten practitioners were recruited for this study and allocated one SLA model and one all zirconia bridge each. RelyX™ Unicem 2 Clicker™ self-adhesive Universal Resin Cement was used as the luting cement. Each examiner performed the seating procedure six times over a two week period, the participants applied the force for two minutes in each time. To measure the cementation force (Newton), a universal testing machine (Instron) was used. Finally, the internal and marginal fit (µm) was determined using SEM. The results showed high initial force which reduced and plateaued after 30 seconds. Maximum force applied was 88.0 N and the minimum was 8.0 N with a mean value of 27.23 N. SPSS was used to perform statistical analysis. Two-way ANOVA with post hoc test were performed on the force results and showed significant difference between most examiners. One-way ANOVA was performed on the internal and marginal fit results and this showed no significant difference between all examiners. Dentists apply different forces when seating FPDs but this does not affect the internal and marginal fit of FPD.