Retention and stability of different implant configurations of four implants supporting mandibular implant overdenture retained by telescopic attachments. In-vitro study.

Aim: this study aimed at was evaluation of retention and stability of four implant supported mandibular overdentures retained by telescopic attachments with different configurations. Materials and methods: three acrylic models for edentulous mandibular arch, each of which received four implants in; quadrilateral configuration "model A", curved configuration "model B" and linear configuration "model C". Five experimental overdentures (acrylic blocks) were made for each model. Resistance to vertical and oblique (lateral, posterior and anterior) displacement forces were recoded to represent retention and stability respectively with directional pull-test. Results: Model A provided the highest significant retention (p value <0.001). Regarding stability, Model A provided the highest significant lateral and anterior stability (p value <0.001). Model C provided the highest significant posterior stability (p value <0.001. Conclusion: Quadrilateral configuration of four implant placement in edentulous mandible provided the best retention and stability for mandibular implant overdenture except for posterior stability where linear configuration had the best resistance to posterior displacement forces.