AbstractAN IN-VITRO COMPARISON OF THE RETENTION OF PREFABRICATED PARALLEL-SIDED VENTED TITANIUM POSTS CEMENTED WITH THREE DIFFERENT DUAL-POLYMERIZABLE RESIN CEMENTSBy Maha M. El-Sayed, B.D.S., D.M.D.A Thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University.Virginia Commonwealth University, 2003Thesis Director: David R. Burns, D.M.D. Associate Professor and Program DirectorGraduate ProsthodonticsDepartment of ProsthodonticsPurpose: The purpose of this in-vitro study was to compare the retentive strength of an autopolymerizing resin cement to three dual-polymerizable resin cements when used to cement paraposts without light activation and to relate diametral tensile stress and hardness as a measure of the degree of polymerization to the retentive strength of the different dual-polymerizable resin cements. Material and methods: 60 human extracted premolar teeth were endodontically-treated and randomly divided into 4 test groups (n=15). Parapost XP posts (size 5) were cemented using Panavia 21(control), Panavia F, RelyX Unicem and Linkmax resin cements. The latter three cements were dual-polymerizable and were not light-activated, and the control cement was autopolymerizable. Also, 140 resin cement samples were fabricated for diametral tensile stress and Knoop hardness testing. Each test had 70 samples, 10 of each of the following groups: Panavia 21, Panavia F light-activated, Panavia F autopolymerized, RelyX Unicem light-activated, RelyX Unicem autopolymerized, Linkmax light-activated, Linkmax autopolymerized. Post retention, diametral tensile stress and surface hardness tests were performed 1 week after sample fabrication or post cementation.Results: ANOVA and Tukey-Kramer statistical analysis revealed significant differences among the test groups for the three tests. Conclusions: Within the limitations of this in vitro study, tested dual-polymerization resin cements had similar or superior parapost retention to the control autopolymerizing resin cement without photoactivation. Dual-polymerizable resin cements had improved diametral tensile stress and surface hardness when light-activated than when autopolymerized. No correlation was observed between surface hardness and diametral tensile stress or between the tested physical properties of the resin cements and their retentive qualities