effect of implant position on retention and stability of mandibular implant-supported overdentures

The standard of treatment of edentulous people is implant retained overdenture. The aim of this study was to compare the effect of different implant location [ABDE, 6AE6, 6BD6] on the retention and stability of mandibular implant overdenture with ball attachment. An experimental study was designed. An acrylic resin model of edentulous mandible with six implant in the location of first molars, first premolar and between lateral incisor and canine on the left and right side was fabricated. A metallic overdenture was fabricated precisely adapted to the model and attached to a Zwick testing machine [crosshead speed of 51 mm/min]. The ball attachments were screw in three ways. First the balls in ABDE, then ball in 6AE6 and then balls in 6BD6 position were screwed. Dislodging tensile forces were applied in three vertical, oblique, anterior-posterior directions for each sample. For each of these three situations, five tests were done. The maximum dislodging force was measured. Normal distributions of data were analyzed with Shapiro-Wilk test. Levene test analazed the variances. A Three-way ANOVA test was employed followed by Tukey's test. The amount of vertical load is significantly higher than the oblique and Ant-post load [P<0.001]. The amount of ant-post load is signifivantly higher than the oblique load [P<0.001]. The average of MDF is significantly higher in 6BD6 position [P<0.001]. This average is also signifivatnly lower in ABDE position [P<0.001]. The amount of measured force in ABDE and 6BD6 position was the least and the most respectively [ABDE=64.51 N and 6AE6=66.06 N]. Vertical and oblique dislodging force are the minimum and maximum measured forces respectively [mean vertical= 87.95 N, mean Lateral= 48.1 N and mean Ant.Post= 63.5 N] Lateral and Ant.Post dislodgment values are higher in 6BD6 and 6AE6 respectively. In vertical dislodgment the retention values in the most in 6BD6 position. Vertical retention in higher than lateral and Ant.Post retentions. The more posterior position the distal implant the more the retention and stability