The retention force attenuation of titanium clasps on PFM crown

Objectives: The purpose of this study was to investigate the retention force attenuation of titanium clasp on porcelain fused to metal (PFM) crown.

Methods: A standard PFM crown was made simulating the standard mandibular first molar ( Chinese database ), and a standard Aker-clasp cast of pure titanium was fitted on the crown. A universal testing machine was employed. The force values during placement and remove of the clasp on the crown were evaluated. 1500 cycles of placement and removal were carried out. The peak force value when the clasp just went off the crown was investigated and analyzed statistically for every 20 cycles. The attenuation curves of the peak values were evaluated.

Results: The peak retention force of pure titanium clasp displayed a linear decline within the first 520 cycles of placement and removal. Y=12.602-0.145X. R²=0.896. Then, it leveled off at 9.00±0.42N.

Conclusion: Because of the attenuation, it suggested that a regular retention force adjustment be necessary for pure titanium clasp in the first 1-2 years when it applying on the PFM crown.