The effect of thermo-mechanical fatigue on the retentive force and dimensional changes in polyetheretherketone clasps with different thickness and undercut

Performance of Graphene-Based and Polyether-Ether-Ketone Polymers as Removable Partial Denture Esthetic Clasp Materials after Cyclic Fatigue

“…In the current study, the ranges of the retentive force of PEEK and GBP materials were 3.70–1.68 and 2.90–1.43 N, respectively ( Table 2 ). These values were close to the clasp retentive force of polymeric materials tested in some studies, especially for pressed and milled PEEK materials, and slightly lower than other literature values [ 6 , 8 , 11 , 12 , 15 , 19 , 20 , 29 , 30 , 31 , 34 ]. As there is no standardized method for clasp retention measurement, variations could be seen between different studies, and therefore the comparison should be limited to articles with the same design, such as analog material, aging method, rate of displacement, number of pull-off cycles, clasp attachment site, amount of undercut tested, and shape of the specimens [ 7 , 11 , 12 , 29 , 32 , 41 ].…”

“…The current study was conducted to assess the use of GBP material as a clasp material after the success of the PEEK material to be an esthetic replacement to Co-Cr material in such application [ 13 , 19 , 20 , 29 ]. Recently, graphene-based polymer was introduced as milled CAD-CAM discs that are appropriate for several dental applications [ 28 ].…”

“…Although, the important value that should be recognized is the value of the minimum retentive force that is acceptable for clinical use. Whereas some authors believed that 2.3 N was enough for clasp retention [ 29 ], others recommend keeping values between 3 and 5 N to avoid periodontal ligament trauma that occurs at 10 N [ 4 ]. Peng et al [ 13 ], in a more in-depth study about PEEK clasp optimization, confirmed that 1.6 N is the minimum value required clinically for clasp retention.…”

“…Many studies evaluated different materials used as RPD framework, especially the direct retainer component [ 4 , 7 , 11 , 12 , 15 , 19 , 20 , 29 , 30 , 31 , 32 ]. Most of the methodologies have applied cantilever bending, three-point loading, cyclic fatigue of insertion and removal of the actual clasp, and virtual stress–strain analysis [ 13 , 17 , 33 , 34 , 35 ].…”

“…The analog tooth was fabricated from a cast alloy, extracted tooth, or lithium disilicate crowns. Clasp deformation due to loading was also investigated by micro-computerized tomography (µ CT), statistically deformable models, and calculation of the total deformation by stress analysis software [ 11 , 13 , 17 , 29 , 33 ]. Scanning electron microscopy was also a beneficial method for studying the surface changes because of friction on both the clasp fitting surface and the counter analog tooth surface [ 7 , 11 , 29 , 31 ].…”