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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.

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Purpose: The aim of this study was to compare the stresses and retention force of two different attachment systems in implant retained maxillary obturator. Material & Methods: an acrylic model was constructed to simulate edentulous case with maxillary defect and three implants were inserted in the pre-maxillary region. The obturator was constructed with the first design bar with equator attachment (BEA) and screwed to the implants. The retention was measured at the base line and after 90,270,540,810,1080,1620,2160 cycles of insertion and removal respectively. Then the second design bar and clip attachment was constructed, screwed and retention testing procedures repeated as that for the first design. Universal testing machine was used for measuring the retentive forces of each retainer type. The vertical static load of 60 and 90 N was applied (loading machine) at three loading points on the obturator prosthesis for the two bar designs. The readings were tabulated and statistically analyzed. Results: Two-factor ANOVA followed by pair-wise Newman-Keuls post-hoc tests were performed to detect significance between variables (Attachment type and aging). Bar and clip design recorded slightly lesser retention force than that of BEA at base line and at all cycles of insertion and removal but with no significant difference between the two designs. But regarding the effect of aging within each group; there was a significant difference at different cycles of insertion and removal. But regarding the stress analysis Bar and clip recorded to some extent less microstrain values than BEA in most of surfaces at different points of loading. Conclusion: The retention force of Bar and clip was slightly lesser than BEA at any given cycle of insertion and removal. Reduction of mean retentive force continues to occur over time within each group. Bar and clip recorded less micro-strain values than BEA at most of the surfaces specially when applying the load on the posterior intact side.

The purpose of the present study was to evaluate radiographically (the crestal bone level change) and clinically (gingival crevicular fluid and implant stability) in cases with four implants supporting mandibular fixed detachable prostheses versus telescopic overdenture. Methodology: Twenty completely edentulous patients were treated with four interforaminal implants to support either fixed detachable prostheses with distal cantilevers or telescopic overdenture. The peri-implant marginal bone loss was assessed radiographically at distal surface of posterior implant bilaterally was calculated in two different intervals. The first interval (0-6months) and the second interval (0-12months) using a digital panoramic imaging system. Also clinical evaluation for checking the implant stability using the perio-test and measuring the gingival crevicular fluid. Results: Regarding the gingival crevicular fluid, the comparison between both groups at the time of delivery and after 6 months, there was no significant difference between the two groups. But there was a significant difference after 12 months. From the obtained data of periotest, it was recognized that there was no significant difference between the two groups regarding the implant stability. But there was a significant difference within each group at the different follow-up periods. The data of marginal bone loss at the distal surface of posterior implant on both sides revealed that there was a significant difference between the two groups at the 1 st and 2 nd intervals. Conclusion: Both telescopic overdenture and fixed detachable prostheses considered a viable successful treatment option for rehabilitating completely edentulous cases. Telescopic overdentures showed less crestal bone loss at the distal implants than that with the fixed detachable design. The gingival crevicular fluid decreases gradually throughout the study period in both designs denoting successful oral hygiene measurements.

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 study was conducted to evaluate maximum biting force (MBF) in two different attachment systems (bollard a vs. ball and socket attachment) retaining mandibular overdenture using a split-mouth design. SUBJECTS AND METHODS: Twelve completely edentulous patients received complete dentures and after adaption of the patient with the new denture, 24 implants were inserted in the canine region using two-stage surgical technique and conventional loading protocol. Six patients received the Bollard attachment at the right side and the Ball and Socket at the left side. Moreover, the other six patients received the bollard attachment at the left side and the ball and socket attachment at the right side. Each patient was treated according to split-mouth design. Insertion of each of the attachment type was assigned randomly. Using occlusal force meter instrument, MBF was measured immediately after loading (0), after 6 months (6), and after 12 months (12). RESULTS: Significant statistical differences (p < 0.05) were obvious in in MBF between Attachment (1) and Attachment (2) immediately after loading (0 months), after 6 months (6) and after 12 months (12) follow-up visits. CONCLUSION: Mandibular implant retained overdenture received Bollard abutment that retained with the denture by the help of resilient liner “Retention.sil”* without housing have higher biting forces than mandibular implant retained overdenture with ball abutment where the plastic house was picked up by monomer free self-cured acrylic resin.