PROBLEM TO BE SOLVED: To produce inorganic agglomerated particles which has a high X-ray imaging ability and a narrow particle size distribution, and to produce dental organic-inorganic composite filler using them.SOLUTION: Inorganic agglomerated particles which has a narrow particle size distribution and a high X-ray imaging ability are prepared by preparing an aqueous suspension containing first primary inorganic particles (A), such as silica compound oxide particles, which show negative zeta potential in water, second primary inorganic particles (B) consisting of such as YbFwhich have a high X-ray imaging ability and show positive zeta potential in water, and ionic surfactant, such as anionic surfactant, and subsequently by spray drying the aqueous suspension.
