Evaluation of Poly-ether-ether-ketone (PEEK) mandibular two implant retained overdenture on zirconium oxide bar retained with heat cured soft liner

Purpose: The aim of study was to evaluate the Poly-ether-ether-ketone (PEEK) mandibular overdenture on zirconium oxide (ZrO₂) bar retained with heat cured soft liner regarding the peri-implant soft tissue changes around the fixtures.
Material and methods: Ten completely edentulous patients were chosen for this study (average age from 55-65 with main age 60. A complete denture was constructed and adjusted for insertion and delivery for all patients. On the planned sites in the canine region, CAD-CAM limiting surgical stereolithographic Stent (STL) was fabricated. Implant fixtures have been surgically placed. Zirconium oxide bar was constructed after the osseointegration period. The patients were divided into two groups according to the shape of a zirconium oxide bar:

Group (I): zirconium oxide bar without cantilever extension.
Group (II): zirconium oxide bar with cantilever attachment extension.

The master cast was screened with zirconium bar. PEEK overdenture with 1 mm space for heat cured soft liner was constructed. CAM manufacturing of PEEK overdenture was done. Soft liner was incorporated in the surface of the overdenture. The peri-implant soft tissue changes were evaluated by using the following variables (1) gingival index (2) bleeding index (3) probing depth. The measurements were evaluated immediately following mandibular overdenture insertion (T0), six months (T6) and one year (T12) after mandibular overdenture insertion.

Results: Gingival scores significantly increased with advance of time for group I (p < .001) and group II (p=.015). Group II showed significant higher gingival scores than group I at T6 (p=.045). Bleeding scores significantly increased with advance of time for group II only (p=.005). There was no significant difference in bleeding scores between groups at different observation times. Probing depth significantly increased with advance of time for group I (p < .001) and group II (p < .001). Group II showed significant higher pocket depth than group I at T12 (p=.021). No markedly difference in vertical bone loss between T6 and T12 for both groups.  

 
Conclusion:
1-       Using PEEK framework over mandibular two implant supported zirconium oxide bar without cantilever and without retaining mechanism of the bar in form of clip or sleeve is considered a promising treatment solution.
2-       Using heat cured soft liner in the desired areas beneath the bar maintain good peri-implant results either with or without cantilever extension.