# In-vitro study of the wear behavior of telescopic crowns made of CoCr, zirconia or PEEK

## TL;DR

This study examines how different materials used in telescopic crowns wear over time, aiming to improve the longevity of dentures.

## Contribution

The study evaluates wear behavior of modern materials like CoCr, zirconia, and PEEK in telescopic crowns.

## Key findings

- The PEEK-PEEK combination showed the greatest wear on primary crowns.
- ZrO2-ZrO2 combinations caused the most wear on secondary crowns.
- PEEK secondary crowns with ZrO2 primary crowns showed the least wear.

## Abstract

Purpose: Double-crown-retained dentures (DCRD) are an established treatment in dentistry. In some cases, the retention between primary crown (PC) and secondary crown (SC) loosens due to wear during daily handling of the denture. The aim of the present study was to examine modern materials for PCs and SCs with regard to their wear behavior. Materials and Methods: Cyclic pull-off tests were conducted on each 40 specimens in five test groups. PCs made of CoCr, PEEK and ZrO2 were cemented onto a prepared resin tooth. SCs were made of the same materials and combined to the following PC-SC combinations: CoCr-CoCr, CoCr-PEEK, PEEK-PEEK, ZrO2-PEEK, ZrO2-ZrO2. The wear areas on the contact surfaces between the PCs and the SCs were examined on SEM images. Results: Wear marks in form of scratches, chipping, ductile deformation or combinations of these forms were observed on the PCs and SCs in the various material combinations. The greatest wear on PCs was observed in the PEEK-PEEK group, while the greatest wear on SCs was observed in the ZrO2-ZrO2 group. The least wear was observed on SCs made of PEEK in combination with PCs made of ZrO2. Conclusion: When using modern materials for DCRDs, the combination of different materials for PCs and SCs must be taken into account. The data found in this study show that only minor wear occurs at SCs made of PEEK, especially in combination with PCs made of ZrO2. Therefore, this combination seems particularly suitable for increasing the longevity of DCRDs.