Assessment of Force Retention between Milled Metallic and Ceramic Telescopic Crowns with Different Taper Angles Used for Oral Rehabilitation

Abstract

The present study assessed the retention forces corresponding to different telescopic systems used in removable prosthetic dentures. The telescopic systems were represented by Co–Cr alloy or zirconia-based primary crowns and Co–Cr secondary crowns. All crowns were manufactured using computer-aided design/computer-aided manufacturing technology (CAD/CAM). Two types of reference abutment teeth (upper canine and first upper molar) were selected in order to obtain the telescopic crowns and two taper angles—of 0° and 2°—were used for the design of the crowns. A number of 120 samples of telescopic crowns were obtained and subjected to mechanical tests, following a specific protocol, on a mechanical testing equipment. The retention of the telescopic systems was evaluated for different sets of cycles (up to 360), represented by movements that simulate the intraoral insertion and disinsertion of the telescopic systems. The present study highlights that the telescopic systems in which the primary crown is made of zirconia ceramics presents more advantages than those made of Co–Cr. All telescopic systems studied, highlighted that by modifying the taper angle from 0° to 2°, the retention forces have decreased, irrespective of the materials used for the fabrication of the primary crown, suggesting that by using a taper angle of 0°, which is known to be ideal, more efficient, and reliable prosthesis can be developed. Thus, even though the ceramic–metallic telescopic system exhibited the highest retention, all telescopic crowns evaluated registered values between 2–7 N, indicating that they are suitable for clinical use.

Retention forces between primary and secondary CAD/CAM manufactured telescopic crowns: an in vitro comparison of common material combinations

“…Using the present telescopic-crown materials under in vivo conditions, the retention forces should be tested intraorally, and if exceeding the desired forces, manual polishing of the primary crowns’ outer and/ or secondary crowns’ inner surfaces may be applied. Furthermore, increasing the offset between primary and secondary crowns, increasing the taper, or reducing the length of the retentive portions may represent further options during the CAD/CAM process to decrease retention forces [ 19 – 21 , 32 , 34 ].…”

Effect of Using Different Primary Crown Materials on the Retention of CAD/CAM Telescopic Partial Dentures

“…The values of the forces recorded for the Co-Cr system were mainly within the range of 1-3 N which are considered low values that may cause potential problems during use. This was explained due to the utilization of a hard and wear resistant primary crown material (ZrO 2 ) opposing a less hard secondary crown material (Co-Cr), as in the metalceramic biomaterials coupling, that can be considered advantageous [44].…”

Comparing digital and traditional guides in first molar implant surgery: A randomized clinical trial

“…In addition, the traditional implant guide does not exhibit the three-dimensional structure of the implant bone area, and there is no accurate positioning marker [23][24][25]. Additionally nowadays a completely digital workflow is possible in clinical dentistry, from digital impression, thorough manufacturing production to final framework, showing good clinical reliability [26] and excellent patients' feedback [27] in many fields of dentistry. Therefore, the intraoral fit in the control group was not as good as that in the digital guide group.…”