Numerical Investigation of Preferable Cast Clasp Arm Design

Objective: The aim of the study was to optimize the design of retentive dental circumferential cast clasp arms using numerical simulations. Methods: Purposely designed experimental 3D models of the clasp arms were modeled on the buccal surface of an upper premolar, in order to be exported for numerical simulations. Preformed clasp wax patterns for circumferential clasps were taken as models. The parameters like width (1.6, 1.8 and 2 mm at the base), and ratio thickness/width (0.4, 0.5, 0.6 and 0.8) were varied and solid models were generated. The finite element models were obtained by importing the solid models into finite element analysis software. They were subdivided into 7266 solid elements, connected at 1709 nodes. All the nodes at the base of the clasp arms were restrained in all directions and a concentrated load of 5 N was applied at the inner tip of the clasp arm. Generated stresses and displacements were calculated numerically and plotted graphically. Results: The maximal stress values were present on the inner surface of the clasp arms and regarding the stress distribution, for the thicker arms the stress surfaces were smaller. This indicates that in a more rigid clasp arm the stresses are more concentrated. Stresses decrease with the increase of the cross-section area and with the increase of the thickness/width ratio. The displacements were maximal at the tip in all cases and it is important to select the proper displacement for the clasp arm, in order to be effective. Conclusion: The numerical investigation can generate experimental clasp models, which can be used to select their preferable design for each particular case. For the experimental clasp arm on the premolar a width of 1.8 mm at the base and a 0.4 thickness/width ratio would be optimal. (Grant ID_1264)