Stress concentration and bone resorption in the jaw for dental implants with shoulders

The stress distributions around particularly shaped dental implants are investigated. These implants have conical shoulders in the upper part to transfer the masticatory forces to the cortical shell of the jaw. By combined interferometrical and photoelasticity measurements with plane models - assuming the bone as homogeneous - and by an additional finite-element analysis with a more refined model - simulating the true inhomogeneous structure of the jaw with the cortical shell and the spongy interior by elements with different Young's moduli - it is shown that the main stress peaks arise below the shoulders for every arbitrary laoding direction. These areas of stress concentration coincide with resorption zones which are systematically observed in the lower jaw of dogs after replacing single teeth by such shoulder implants made of alumina ceramic. The provides evidence that a direct correlation between stress concentration and resporption exists.