The aim of this research was to design an optimum 6R passive haptic robotic arm (PHRA) to work in a limited workspace during dental implant surgery. Misplacement of an implant during dental surgery causes longer recuperation periods and functional disorders. In this study, a passive guidance robot arm was designed as a surgical aid tool for a dentist during the operation to reduce the surgical complications. Optimum design of a 6R robot is a complex issue since minimum energy has to be consumed while maximum workspace is to be achieved using optimized link lengths. The methodology used deals not only with link lengths of manipulator but also mass and inertia of the links along with the location of the tool path. Another feature of the methodology is to maximize haptic device transparency using an objective function that includes end-effector torques/forces with workspace limits taken as constraints. The objective function was obtained from dynamic equations and the constraints were defined using kinematic equations. The constrained nonlinear optimization problem was solved using Sequential Quadratic Programming (SQP) and Genetic Algorithms (GA). Main contribution of this paper is an optimization algorithm that considers spatial dynamics to reduce parasitic torques leading to an optimal 6R robot design. Details of the methodology, solutions, and performance of the optimization techniques are presented.