Effect Of Implant Abutment Connection Designs, And Implant Diameters On Screw Loosening

Objectives: The purpose of this in-vitro study was to evaluate screw loosening of two different forms of implant abutment connection designs,and two implant diameters by measuring removal torque value before and after cyclic loading.

Methods: Twenty implant fixtures were divided equally into 2 groups (N =10): group I fixture with conical hybrid connection (CH), group II fixture with internal hex connection (IH). Each group was divided into two subgroups according to implant diameters: subgroup A (3.3 mm),subgroup B (4.2 mm).Each fixture was vertically placed in the center of acrylic resin block and connected to the abutments with a 20 Ncm tightening torque. The samples were subjected to eccentric cyclic loading (at a distance 5mm) away from center of abutment at 100000 cycles. Screw loosening was evaluated before and after cyclic loading by measuring RTVs in (Ncm) using a digital torque gauge .The values of removal torque in Ncm before and after cyclic loading were analyzed using the SPSS statistical analysis.
Results: For GI The initial RTVs loss ratio measurement was (14.45±3.18) and decreased significantly after loading.it was (11.47±3.64). For GII The initial RTVs loss ratio measurement was (20.47±4.99) and increased significantly after loading.it was (35.35±4.26). There is no significant effect upon screw loosening for small and standard diameter
Conclusions: within the limitation of this study the results suggested that the implant abutment connection design, and dynamic cyclic loading have an effect on screw loosening. Conical hybrid connections showed a better screw stability than internal hex connection.A standard diameter was more advantageous in terms of the torque loss rate than small diameter.