307 FUNDAMENTAL RESEARCH Volume 33, Number 3, 2020 Correspondence to: Prof Dr Bogna Stawarczyk Department of Prosthetic Dentistry University Hospital, Ludwig- Maximilians-University Munich Goethestraße 70 80336 Munich, Germany Fax: +49 89 4400 59502 Email: bogna.stawarczyk@ med.uni-muenchen.de Submitted August 8, 2019; accepted October 24, 2019. ©2020 by Quintessence Publishing Co Inc. Fracture Load of Veneered Telescopic Secondary Crowns Made of High-Performance Polymer on Zirconia Primary Crowns: Impact of Veneering Technique Nina Lümkemann, MSc Marlis Eichberger, CDT Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians-University Munich, Munich, Germany. Ralph Riquier, CDT r2dental, Remchingen, Germany. Ryan J. Murphy, PhD Technology Division, Solvay Dental 360, Solvay Specialty Polymers USA, Alpharetta, Georgia, USA. Bogna Stawarczyk, MSc Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians-University Munich, Munich, Germany. R emovable partial dentures (RPDs) remain an important treatment option for the replacement of missing teeth. 1 However, there is a clinical need for innovation in RPDs regarding improvements in design, fabrication, ft, and esthetics. 1 To achieve these improvements, high-performance polymers such as polyether ether ketone (PEEK) and polyether ketone ketone (PEKK) have been investigated as alterna- tives to commonly used metallic materials. 2–5 Among RPDs retained with clasps, telescopic crowns present a great option for their esthetic and retentive elements. 6,7 The telescopic crown is defned as an artif- cial crown constructed to ft over a coping, another crown, a bar connector, or any other suitable rigid support for the dental prosthesis. 8 A comparison of telescopic crown– and clasp-retained RPDs showed no differences between the two types in terms of survival rates, complications, or abutment teeth survival. 9 Telescopic crowns were found to be less traumatic than other retainers, 7 to provide better esthetics, to facilitate access to cleaning by the patient or dentist, and retain certain teeth longer. 6 Purpose: To analyze the impact of different veneering techniques on the fracture load of telescopic secondary crowns made of a high-performance polymer (Ultaire aryl ketone polymer [UAKP]). Materials and Methods: Zirconia primary crown models (taper of 0 degrees) were prepared (N = 48), polished, scanned, and divided into four veneering groups (n = 12 each): premanufactured, digital, full anatomical, and vestibular. For all groups except vestibular, a standardized telescopic secondary crown (thickness: 0.6 mm, circular margin: 1 mm) was constructed, adapted to the corresponding primary crown, milled from UAKP, and veneered. The veneered master crown was developed based on the premanufactured group. After surface polishing, all specimens were artifcially aged in a chewing simulator (1.2 million cycles, 50 N, 1.1 Hz, between 5°C and 55°C). Fracture load was tested in a universal testing machine with a piston (Ø = 6 mm, 1 mm/minute). Fracture patterns were analyzed. For statistical analysis, Kolmogorov-Smirnov test and descriptive statistics followed by one-way ANOVA with post hoc Scheffé test were conducted (P < .05). Results: Signifcant differences in fracture load were found between different veneering techniques (P < .001), with the highest values for the vestibular and digital groups, followed by the premanufactured group. Full anatomical veneering showed the signifcantly lowest fracture load (1,885 ± 397 N). For all specimens, cohesive brittle fractures with similar fracture patterns occurred, irrespective of the veneering technique. Conclusion: The veneering technique of telescopic secondary crowns made of high-performance polymer affects overall stability. All veneering techniques provided suffcient fracture load values for telescopic secondary crowns made of UAKP. Digital veneers seem the most recommendable. Int J Prosthodont 2020;33:307–314. doi: 10.11607/ijp.6669 © 2020 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.