In-Vitro Evaluation of Strain Induced by Various Extra Coronal Attachment Materials in Removable Partial Dentures Restoring Mandibular Kennedy Class I Following Clinical Simulation for One Year

ABSTRACT
Purpose: The objective of this study was to evaluate the strain induced by various extra coronal attachment materials retaining removable partial dentures restoring mandibular Kennedy class I following clinical simulation for one year.
Materials and Methods: Twelve identical models, fabricated by 3D printing, representing Kennedy class I mandibular partially edentulous cases with bilateral first premolars as primary abutments were used. Each model had four removable dies; canines and first premolars bilaterally. On these dies, bilateral splinted crowns were fabricated and grouped according to the extra coronal attachment material used (PEEK/BioHPP, zirconia and metal). Each group included four model, each model was designed having four slots for strain gauges (two on each side). These slots were positioned 1mm distal to the 1st premolar (SG1 and SG3) and at the edentulous ridge (SG2 and SG4) 1 cm away from the first one. Removable partial dentures were fabricated, and a universal testing machine was employed to assess the strain induced under unilateral and bilateral loading conditions. This assessment was conducted both prior to and after clinical simulation for one year. The clinical simulation involved chewing simulator sessions and cycles of insertion and removal for the denture.
Results: PEEK (BioHPP) group exhibited the least strain induced, both prior to and after clinical simulation for one year, under both unilateral and bilateral loading conditions.
Conclusions: PEEK (BioHPP) extra coronal attachment used for retaining removable partial denture provides more favorable stress dissipation in comparison to zirconia and metal attachments.
KEYWORDS:
PEEK, zirconia, metal, strain gauges