A comparison of the flexibility and fracture point of cast cobalt-chromium, milled cobalt-chromium, laser printed cobalt-chromium and milled Polyetherketoneketone partial denture clasps

Removable partial dentures (RPD) are a cost-effective way of replacing missing teeth. Acrylic RPDs can be used successfully, but those with metal frameworks are superior due to their increased strength, durability, retention, fit, longevity and decreased soft tissue coverage. Cast cobalt-chromium (CrCo) metal alloys have traditionally been used in RPDs, but have shortcomings. Metal may increase the weight and is inflexible, making it unsuitable for clasps on small teeth or those with deep undercuts. The casting process can result in unpredictable internal porosity, which can cause irreparable fracturing of the clasps. Furthermore, metal clasps in the aesthetic zone are unsightly. Polyetherketoneketone (PEKK) is a new-generation thermoplastic used in orthopaedic surgery to manufacture prosthetic components due to its desirable physical properties, ease of manufacture and tissue biocompatibility. It may also have possible dental applications if used with computer-aided design (CAD) and computer-aided manufacturing (CAM) processes to make RDP frameworks. Other advantages include good chemical resistance, desirable mechanical strength and flexibility, excellent abrasion resistance, flame resistance, antibacterial properties, and no backscatter, shadows or artefacts during conventional X-ray imaging or radiotherapy. It has flexibility and elasticity comparable to cortical bone, is lightweight and may be used in 3D imaging, printing and milling processes