Re: Factors playing role in denture retention

Upper Dentures are held in place by interfacial surface tension, generally referred to as "suction" or "vacuum" and other important factors such as good base adaptation and border seal.

The same applies for Lower Dentures, but the small support surface area and the pronounced musculature in the lower jaw, reduce the secure grip of dentures, causing displacement of the denture.

Wearing dentures for a number of years causes the underlying surface to resorb, resulting in "shrinkage" of the gum. In worst cases, the "shrinkage" is so severe as to make virtually impossible the construction of stable, satisfactory dentures.

: One hundred nineteen patients with a total of 258 implants participated in the study. They had been monitored regularly during an observation period of 5 to 15 years (mean 9.3 yr). Seventy-five patients had a resilient retention device (ball anchors or a round clip bar); 44 patients had a rigid bar with or without distal extensions. The incidence and rate of complications were calculated for the overall- and for the 2- and 5-year observation periods. Comparisons were made between the three categories of maintenance and the two types of retention. A Kaplan-Meier analysis was applied for calculations of changes of the retention mechanism.

Results: The mean number of complications per overdenture during the entire observation period was 3.5; this did not differ statistically between the two retention groups. Some significant differences were found only for the 2- and 5- year period. Broken, loose, or lost female parts were more frequently observed with resilient devices, as were repairs and relining of the resin denture base, whereas tightening of bar retainers was more typical with rigid bars. A change from a resilient retention device to a rigid bar was performed more often than vice versa but not at a statistically significant level.

Conclusion: Although these long-term results do not indicate a significant difference between the retention groups, a slight superiority of the rigid bar is suggested