Parameters Affecting the Retention Force of CAD/CAM Telescopic Crowns: A Focused Review of In Vitro Studies.

Abdullah Kamel,James Tsoi,Gehan Fekry,Amr Badr

doi:10.3390/jcm10194429

Abstract

Telescopic systems constructed using computer aided design and computer aided manufacture (CAD/CAM) can overcome many drawbacks associated with conventionally constructed ones. Since retention is considered the most important function of these retainers, this scoping review aimed to discuss and summarize the parameters that affect this function in CAD/CAM-manufactured telescopic crowns and to compare their retention force values with the recommended retention force. An electronic search was done in Pubmed and Google Scholar databases using different keyword combinations to find the related articles. Seventeen articles that follow the eligibility criteria for this review were selected and analyzed for detection of each of the tested parameters and their effect on retention force. The parameters tested in these articles were divided into parameters related to design, manufacturing, material type, and test condition. Regardless of the effect of these parameters, the retention force values recorded in most of the selected studies laid within or were higher than the recommended retention force (2.5–10 N), which indicated the need to design and set the combination of materials of telescopic systems according to oral biomechanics.

Highlights

A telescopic denture is defined as “an overdenture which is a dental prosthesis that covers and is partially supported by natural teeth, natural tooth roots, and/or dental implants” [1]
The computer aided design and computer aided manufacture (CAD/Computer Aided Manufacture (CAM)) materials of telescopic crowns used in these studies included metals and non-metals
Thirteen articles tested the taper degree effect on the retention force. Eight of these studies [17,19,21,25,33,34,39,42] in which specimens with 0◦, 1◦, 2◦, 4◦, 5◦, and 6◦ taper angle were tested and the results showed that increasing the taper resulted in a decrease in the retention force

Summary

Introduction

A telescopic denture is defined as “an overdenture which is a dental prosthesis that covers and is partially supported by natural teeth, natural tooth roots, and/or dental implants” [1]. The retention is obtained by wedging action Such design is commonly used because it is less technique sensitive and provides a less damaging force to the supporting abutments due to absence of continuous contact between primary and secondary crowns which will act as a force arm [3,9,12,13]. Resilient telescopic design which includes 30-micron spacer between the primary and secondary coping which provides adequate fitting, allows for minimizing the friction between double crowns, and compensates for the mucosal resiliency during functional loading. Such design reduces the possibility of transmitting extra force to the supporting structure, when dental implants are used [14]

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