Finite Element Analysis and Fatigue Test of INTEGRA Dental Implant System

Abstract

The study involved numerical FEA (finite element analysis) of dental implants. Based on this, fatigue tests were conducted according to the PN-EN 14801 standard required for the certification of dental products. Thanks to the research methodology developed by the authors, it was possible to conduct a thorough analysis of the impact of external and internal factors such as material, geometry, loading, and assembly of the dental system on the achieved value of fatigue strength limit in the examined object. For this purpose, FEM studies were based on identifying potential sites of fatigue crack initiation in reference to the results of the test conducted on a real model. The actions described in the study helped in the final evaluation of the dental system design process named by the manufacturer as INTEGRA OPTIMA 3.35. The objective of the research was to identify potential sites for fatigue crack initiation in a selected dental system built on the INTEGRA OPTIMA 3.35 set. The material used in the research was titanium grade 4. A map of reduced von Mises stresses was used to search for potential fatigue crack areas. The research [loading] was conducted on two mutually perpendicular planes positioned in such a way that the edge intersecting the planes coincided with the axis of the system. The research indicated that the connecting screw showed the least sensitivity (stress change) to the change in the loading plane, while the value of preload has a significant impact on the achieved fatigue strength of the system. In contrast, the endosteal implant (root) and the prosthetic connector showed the greatest sensitivity to the change in the loading plane. The method of mounting [securing] the endosteal implant using a holder, despite meeting the standards, may contribute to generating excessive stress concentration in the threaded part. Observation of the prosthetic connector in the Optima 3.35 system, cyclically loaded with a force of F ≈ 300 N in the area of the upper hexagonal peg, revealed a fatigue fracture. The observed change in stress peak in the dental connector for two different force application surfaces shows that the positioning of the dental system (setting of the socket in relation to the force action plane) is significantly decisive in estimating the limited fatigue strength.

Keywords: INTEGRA IMPLANTS; INTEGRA OPTIMA; PN-EN 14801; dental implant cracks; dental implant damage; finite element analysis.

Figure 1

Geometrical model of the OPTIMA 3.35 dental set.

Figure 2

Contact condition screw—implant (thread domain)—friction coefficient in the thread µ = 0.4.

Figure 3

(a) FEA mesh of the entire set with division into elements and (b) boundary conditions—point of force application.

Figure 4

The tested system OPTIMA 3.35 on a brass base.

Figure 5

(a) Research Workstation: Dora 14801. (b) The most favorable mounting of the system to the holder at the testing station met the guidelines of PN-EN 14801.

Figure 6

(a) Map of reduced stresses of the endosteal implant for T = 0.08. (b) Map of reduced stresses of the connecting screw joining the endosteal implant with the prosthetic connector for T = 0.08. (c) Map of reduced stresses of the prosthetic connector for T = 0.08. Arrow shows the highest stresses.

Figure 7

Geometry of the hexagonal peg and marked [in red] planes of load action.

Figure 8

Boundary conditions for the OPTIMA 3.35 dental set; loading in the X-Z plane.

Figure 9

Number of stress cycles (S-N curve) or Wöhler curve for the Optima 3.35 dental system (material: titanium).

Figure 10

Identification of the most stressed areas in the connector and SEM microscope study results; visible: fatigue focus observed in the upper area of the fracture—corner, perifocal area, primary displacements, and fatigue lines. Load force F ≈ 300 N.

Figure 11

SEM Image (30×) of the breakthrough in the area of the connecting screw under the load force F ≈ 300 N (plastic fracture).

Figure 12

Macro photo of a broken hexagonal peg of the prosthetic connector.