![]() 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. In the conical design, the retention is obtained by wedging action. Moreover, there is a rapid loss of retention due to continuous contact of double crowns which results in progressive wear and excessive force on the supporting structures, so it is only used with strongly supported abutments. Although this design provides sufficient retention at the beginning, it has many drawbacks such as technique sensitivity as it requires precise manufacturing procedures to allow fit between the secondary and primary crown. In the cylindrical design, the retention is obtained by friction between the parallel walled primary and the secondary crowns. The retention mechanism of the double crown system differs according to its design. These retainers are quite commonly used, at least in Germany and Sweden, because of their merits of incorporating proper distribution of force on the abutment, allowing for effective oral hygiene with the maintenance of periodontal health, achievement of good esthetics, and good survival rate. Such retainers are made up of two crowns primary crown (inner crown), attached to tooth or implant, and secondary crown (outer crown) attached to the denture. This type of prosthesis uses the double crown system as retainers or attachments. ![]() 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.Ī 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”. The parameters tested in these articles were divided into parameters related to design, manufacturing, material type, and test condition. 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. ![]() An electronic search was done in Pubmed and Google Scholar databases using different keyword combinations to find the related articles. 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. Telescopic systems constructed using computer aided design and computer aided manufacture (CAD/CAM) can overcome many drawbacks associated with conventionally constructed ones.
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