“The high-performance polymers called PEEK and PEKK have exciting potential in dentistry as a metal alternative for removable and implant prosthetic frameworks.” Professor Paul Tipton
In the High-performance Polymers - Part One article published in Private Dentistry (Oct. 2015), Professor Paul Tipton (Follow on Twitter) gives us an introduction to high-performance polymers (HPP) in dentistry, and discusses polyether ether ketone (PEEK), as a new material for framework fabrication in prosthodontics. In this post, you can follow some of the highlights of this article.
According to Professor Tipton, HPPs are the uppermost class of plastics, possessing better temperature and chemical stability and mechanical properties than the commodity plastics. One family of HPPs to have entered dentistry is Polyarletherketones ('PAEKs'), and consists of several members with varying chemical structures.
Amongst it, the most well-known and widely used is PEEK, and more specifically PEEK-OPTIMA™ polymer from Invibio Biomaterial Solutions, a Victrex plc company. PEEK was invented in the UK in 1978 (ICI - now as Victrex plc.) and was selected by aerospace, semiconductor, automotive and medical industries as a standard material of use in all these sectors. It is typically used as a metal replacement, due to its strength to weight ratio and corrosion resistance. The material can be filled with pigments or reinforcing agents. In their unaltered, natural state they are beige in colour.
Professor Tipton highlights that many of us in the dental industry are inadvertently familiar with PEEK through its use in healing caps, temporary abutments and scan bodies. Short term devices such as these have been sold direct to dentists through the dental companies for many years. Either natural or coloured PEEKs are typical and have been used in these temporary devices for over a decade
In the case of customised prostheses, the upstream material or shape such as the PEEK-OPTIMA based JUVORA Dental Disc becomes the â€˜deviceâ€™ and is regulated and cleared for use for a defined set of indications. PAEKs have appeared here as materials for use in injection press systems or as discs for computer aided design/manufacture (CAD/CAM).
HPP properties vs. metal
When handling a prosthetic framework made, for example a JUVORA dental disc, a striking thing is the difference in weight. Professor Tipton quantifies the difference: identical full arch implant prosthetic substructure frameworks made from PAEK weighs 4.9g, titanium 17g, zirconia 23g and cobalt chrome 33g.
Perhaps the most exciting difference, as reported by Professor Tipton, is the possibility to introduce shock absorption to a prosthesis. This could have a positive impact on patient comfort and damage limitation. Furthermore, the most relevant mechanical property related to the aspect of shock absorption is not compressive strength (as is sometimes promoted), but actually flexural strength and elastic modulus.
Professor Tipton further emphasizes that metals have very high compressive strengths relative to PAEKs but are not shock absorbing. Naturally, a design must also consider the influence of thickness and shape as well, but values for flexural strength and elastic modulus are more indicative of the stiffness of a material and how much it will deflect the load. Stiffer materials have a high elastic modulus meaning that metals require high loads to elastically deform them.
Extract from the article: Elastic modulus comparison of different dental materials and natural bone.
HPPs such as PEEK-OPTIMA or also PEKKs have exciting potential in dentistry as a metal alternative for removable and implant prosthetic frameworks, summarizes Professor Tipton. Their stiffness properties confer promise as a substructure that could add an element of shock absorption and may have benefits for patient comfort, addressing parafunction and damage limitation.