The raw data obtained directly from x-ray acquisition device may yield a comparatively poor image quality representation. In case of medical images human involvement and perception is of prime importance. It is a difficult task to interpret fine features in various contrast situations . Dentists interpret the dental x-rays using their knowledge, perception and experience. So there is a chance of error in deciding the right medical treatment. Nowadays digital dental radiographs, in which enhancement is done automatically, are available but the system are very costly. Our algorithm will give alternate solution to this problem. It includes X-ray imaging its processing for identifying the exact location depth of damage in affected tooth. In this paper , we explore image segmentation using ISEF algorithm and active contour model to detect and diagnose the dental caries in case of decayed tooth.