The computational complexity when a block configuration in an encoding target region is determined is reduced while the degradation of coding efficiency is suppressed. The dental surgical procedure is done by seeing the images displayed on the screen. Validity of a lookup transaction performed on the balanced tree is determined by verifying a version value of only the leaf node accessed during the lookup operation against the retrieved version information. Machining may be used to remove any annular region of increased thickness so that the remaining sheet material has the same thickness. The pellets are made of a mixture including a polymeric binder and the chemically active conditioning agent, in a defined weight ratio and in a narrow range of particle sizes. Then, one of the determined algorithms is selected to maximize compression.