Retention Assessment of High Performance Poly-etheretherketone Removable Partial Denture Frameworks Constructed by Various Techniques (in vitro Study)

Poly-etheretherketone is a novel material used in the construction of the removable partial dentures frameworks instead of the metal frameworks. This material can be fabricated by various techniques. Most common methods are the injection molding or Computer Aided Design/Computer Aiding Manufacturing (CAD/CAM) milling techniques. The fabrication technique may affect the adaptation of the frameworks by influencing the retention.

To assess the effect of the processing techniques of high performance Poly-etheretherketone either by injection molding (pressing) or  CAD/CAM  milling techniques on removable partial denture frameworks retention for rehabilitation of upper class I Kennedy classification.

This in vitro studywas performed on one epoxy resin model representing the partially edentulous maxillary arch with natural teeth extending from first premolar to first premolar. First premolars and canines were reduced to receive porcelain fused to metal crowns with 0.50mm mesio-buccal retentive undercuts, distal guiding planes and mesial occlusal rest seat on first premolars and cingulum rest seat on canines. Considering the construction technique of frameworks, twenty samples were divided into two groups. In the group I, ten frameworks were fabricated by injection molding, and in the group II, ten frameworks were fabricated by CAD/CAM. The removal and insertion was carried out at 120, 720 and 1440 cycles for both groups, respectively. The retention values were measured by using Universal Testing Machine before cycling and after each interval.

Independent t-test showed significant difference on retention at different simulation cycles between groups. Group II exhibited significantly less retention than group I (p< 0.001), while comparing the retention at different cycles within each group by paired sample t-test exhibited significant decrease of retention till the end of the cycling (p< 0.001).

From the retention point of view, high performance poly-etheretherketone frameworks fabricated by injection molding technique provided a promising method over CAD/CAM technique milling method.