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.

This study aimed to evaluate the retentive force of polyetheretherketone (PEEK) and zirconia secondary crowns on ready-made titanium implant abutments (with height, diameter, and taper as 5.5 mm, 4.5 mm, and 6°, respectively) as the primary crown. PEEK, zirconia, and titanium secondary crowns were fabricated using a CAD/CAM system. Insertion and removal tests of secondary crowns on the primary crown were conducted for 2,000 cycles. The initial retentive forces recorded at the 100th cycle for PEEK, zirconia, and titanium were 13.0±7.9, 2.9±2.6, and 27.6±1.7 N, respectively. The retentive forces of PEEK and zirconia showed no significant difference among all cycles. However, the retentive force of the titanium used as a control decreased (20.3±2.8 N) significantly at the 2,000th cycle. Although the retentive force of PEEK was lower than that of titanium, it was within the range that can provide a suitable retentive force of 5 N for removable dental prostheses.

AIM: The aim of this study is to evaluate two different designs in mandibular bilateral free end saddle cases with the use of osseointegrated implants. The designs evaluated were OT-strategy extracoronal attachment and bar attachment. Radiographic evaluation was carried out for implants and natural abutment in terms of bone density. MATERIALS AND METHODS: This study was conducted on 10 patients with bilateral distal extension area with missing molars bilaterally; the patients were divided into two groups after implant insertion on the second molar area. Group I: Patients received extracoronal attachment distal to the last natural abutment teeth with the construction of metallic removable partial denture (RPD). Group II: Patients received bar attachment with the construction of metallic RPD. Both groups have the maxillary arch edentulous with the construction of complete maxillary dentures within our study. Radiographic evaluation for bone density was done for both groups at the time of prosthesis insertion, 3, 6, and 9 months later. A comparison between the two groups regarding each follow-up period was performed by an independent t-test. RESULTS: Although there were some differences between both designs in the 1st-time intervals, generally, there were no significant differences between the two designs all over the 3-time intervals. CONCLUSION: From the results of this study, it was concluded that: Although there were no significant differences between both designs, bar-attachment showed better results which should be confirmed with more future researches.