Seventh Mississippi State - UAB Conference on Differential Equations and Computational Simulations. Electronic Journal of Differential Equations, Conference 17 (2009), pp. 107-121. Title: Fourth-order partial differential equations for effective image denoising Authors: Seongjai Kim (Mississippi State Univ., MS, USA) Hyeona Lim (Mississippi State Univ., MS, USA) Abstract: This article concerns mathematical image denoising methods incorporating fourth-order partial differential equations (PDEs). We introduce and analyze piecewise planarity conditions (PPCs) with which unconstrained fourth-order variational models in continuum converge to a piecewise planar image. It has been observed that fourth-order variational models holding PPCs can restore better images than models without PPCs and second-order models. Numerical schemes are presented in detail and various examples in image denoising are provided to verify the claim. Published April 15, 2009. Math Subject Classifications: 35K55, 65M06, 65M12. Key Words: Variational approach; PDE-based restoration model; fourth-order PDEs; piecewise planarity condition.