Comparison of ball retained over denture's retention the most anterior and posterior implant positions at symphysis

The aim of this study was tocompare retention of implant-tissue supported overdentures with ball attachments in the most anterior and posterior implant positionsat symphysis.

An acrylic resin model of edentulous mandible with no undercuts was fabricated. Two pairs of implants, two by two, were placed symmetrically in the most anterior and posterior positions at symphysis.Two were placed 5mm from midline in anterior position while two others 5mm infront of mental foramina site in posterior position. A metallic overdenture was made on the model precisely. Then an over denture housing was prepared on the frame work and joined to it. The ball abutments were screwed on the pair of implants in different positions and the complex of attachment housing and clinical insert, were attached into the over denture housing. Five samples were tested for each position. Zwick testing machine loaded and measured tensile forces invertical direction for each sample. Maximum Dislodging Force (MDF) was recorded at the moment of completed attachment of over denture from the model. Independent sample T-test was performed to analyse the data and results reported by confidence coefficient of 95%.

There was no statistically difference in retention of implant-tissue supported over dentures in the most anterior and posterior positions of implants at symphyseal region (P>0.05).

The amount of retention is the same in the most anterior and posterior positions of implans at symphysis.