In vitro retention loss of attachment-retained removable partial denture

To investigate the importance of attachment types on the retention loss of extracoronal attachment-retained removable partial dentures depending on the usage period.

In order to observe the retention loss of 5 different attachments (OT Strategy, OT Strategy-metal protected, Vario-stud-snap and Vario-soft 3 and ERA-RV) over time, attachment-retained partial dentures representing Kennedy II mod. I case were placed in a custom-made, retention test machine. For each minute, eight separating and joining movements were performed and retention values (Newton) of the attachments were recorded by computer. The retention tests implemented in 540,1080 and 2160 cycles. The data were evaluated statistically according to the two-way ANOVA and Tukey parametrical tests.

The slide type attachment providing the best retention force was observed to be the most worn out by this process (p < 0.01) while the ball type attachments, which typically have the lesser retention force, showed less retention loss (p < 0.01).

It can be concluded that the retention attributes of the attachment-retained dentures were affected by the specific type of precision attachment as well as the usage period.

Precision attachments with ball-type plastic matrices may be recommended for the clinical use due to their retention stability over time.