INTRODUCTION: The use of platelet concentrates remains controversial. Several techniques for platelet concentrates are available and each method leads to a different product with different biology and potential uses. Platelet rich fibrin (PRF) is an autologous biomaterial composed of a fibrin clot matrix entrapping leukocytes, cytokines, living progenitor cells, and platelets capable of releasing various growth factors. One of the recent platelet concentrates is the mineralized plasmatic matrix (MPM) which has a different way of preparation. It creates a stable homogeneous single-moldable compound. OBJECTIVES: The aim of this experimental study was to compare the effect of PRF to MPM when combined with biphasic calcium phosphate alloplast in treating horizontal critical sized ridge defects in a canine model. MATERIALS AND METHODS: A split mouth design was carried out using the third and fourth mandibular premolars of two healthy mongrel dogs. A total of eight horizontal critical sized ridge defects were surgically created. The defects on the left side (group I); were managed with MPM composite, MPM compact layer, then collagen membrane. On the right side (group II); defects were managed with PRF mixed with biphasic calcium phosphate alloplast followed by the application of PRF compact strips, then collagen membrane. The dogs were sacrificed after 4 weeks. Samples were dissected and prepared for histological evaluation. RESULTS: Histological results showed that quality of bone formed in MPM group was superior to PRF. This was evident with the formation of well-organized compact bone in MPM specimens versus immature woven trabecular bone in PRF ones. CONCLUSIONS: The fibrin network that is produced in the MPM composite allows for its homogeneity. This offers a very good stability for the graft which was found to be more effective in enhancing wound healing during guided bone regeneration of horizontal ridge defects.