[Problems] To provide a means and method for providing a pulverized extracted tooth product without causing the extracted teeth to lose their original properties. To provide a new material, originated from the pulverized extracted tooth product and imbued with new properties suited to the regeneration and the like of the alveolar bone. [Solving Means] A method for preparing a pulverized product of extracted tooth, comprising the pulverizing of extracted tooth with a pulverizing apparatus to obtain a pulverized product of an extracted tooth. The pulverizing apparatus comprises a sealable pulverizing chamber and freely rotating pulverizing blade within said pulverizing chamber, and the extracted tooth are pulverized by said pulverizing apparatus together with pieces of physiological saline ice. A method of preparing a demineralized powder originated from an extracted tooth by means of an acid treatment of the pulverized product of extracted tooth obtained by the above method to obtain a demineralized powder. A method of preparing a composite of demineralized powder and apatite by coating the demineralized powder obtained by the above method.