Mahmoud S.H^a, El-negolyS^b, Ibrahim A^c, Ibrahim R^d a: Professor and chairman of Operative Dentistry, Operative Dentistry Department, Faculty of Dentistry, Mansoura University. b: Assistant Professor of Biomaterial, Biomaterials Department, Faculty of Dentistry, Mansoura University. c: Lecturer of Operative Dentistry , Operative Dentistry Department, Faculty of Dentistry, Mansoura University. d: Assistant Lecturer, Operative Dentistry Department, Faculty of Dentistry, Mansoura University. Abstract: Objectives: To evaluate the 18-month clinical performance of MOD indirect composite inlays luted with three resin cement strategies, and observein-vitro both microtensile bond strength (µTBS) and microleakage of these cements with the same indirect composite inlays after immersion in lactic acid and distilled water. Materials and Methods: For clinical trial, a total of 60 MOD cavities were selected and restored with indirect composite inlays SR Nexo paste (IvoclarVivadent AG Schaan, Liechtenstein) luted with three different resin cement strategies; an etch&rinseVariolink N (IvoclarVivadent AG Schaan, Liechtenstein), self-etch (SE) Panavia F2.0 (Kurary medical, Okayama, Japan) and self-adhesive (SA) RelyXUnicem(3M ESPE, ST Paul, MN USA). The restorations were evaluated at baseline, after 6, 12 and 18-month using USPHS criteria. For µTBS and microleakage investigations, standardized MOD cavities were prepared in 96 intact human molars (N=48 for each test). Specimens were divided into three groups corresponding to the resin cement used in the clinical trial and restored with the same indirect composite. Each group was subdivided into two subgroups regarding to storage media (lactic acid or distilled water). Then, each subgroup was divided into two haves according to the storage time (24h or 168h). Results:For clinical trial, no loss of restorations was recorded after 18-month for all the three groups. There was no significant difference between the baseline and 18-month results for any type of resin cements. However, significant difference was recorded regarding marginal discoloration. For microleakage and µTBS investigations, there was significant difference between the three resin cement strategies in different storage media and times. Conclusion: All the three resin cements strategies tested, showed acceptable clinical performance after 18-month.   Mahmoud S.H^a, El-negolyS^b, Ibrahim A^c, Ibrahim R^d a: Professor and chairman of Operative Dentistry, Operative Dentistry Department, Faculty of Dentistry, Mansoura University. b: Assistant Professor of Biomaterial, Biomaterials Department, Faculty of Dentistry, Mansoura University. c: Lecturer of Operative Dentistry , Operative Dentistry Department, Faculty of Dentistry, Mansoura University. d: Assistant Lecturer, Operative Dentistry Department, Faculty of Dentistry, Mansoura University. Abstract: Objectives: To evaluate the 18-month clinical performance of MOD indirect composite inlays luted with three resin cement strategies, and observein-vitro both microtensile bond strength (µTBS) and microleakage of these cements with the same indirect composite inlays after immersion in lactic acid and distilled water. Materials and Methods: For clinical trial, a total of 60 MOD cavities were selected and restored with indirect composite inlays SR Nexo paste (IvoclarVivadent AG Schaan, Liechtenstein) luted with three different resin cement strategies; an etch&rinseVariolink N (IvoclarVivadent AG Schaan, Liechtenstein), self-etch (SE) Panavia F2.0 (Kurary medical, Okayama, Japan) and self-adhesive (SA) RelyXUnicem(3M ESPE, ST Paul, MN USA). The restorations were evaluated at baseline, after 6, 12 and 18-month using USPHS criteria. For µTBS and microleakage investigations, standardized MOD cavities were prepared in 96 intact human molars (N=48 for each test). Specimens were divided into three groups corresponding to the resin cement used in the clinical trial and restored with the same indirect composite. Each group was subdivided into two subgroups regarding to storage media (lactic acid or distilled water). Then, each subgroup was divided into two haves according to the storage time (24h or 168h). Results:For clinical trial, no loss of restorations was recorded after 18-month for all the three groups. There was no significant difference between the baseline and 18-month results for any type of resin cements. However, significant difference was recorded regarding marginal discoloration. For microleakage and µTBS investigations, there was significant difference between the three resin cement strategies in different storage media and times. Conclusion: All the three resin cements strategies tested, showed acceptable clinical performance after 18-month.