Numerous studies have been conducted on human tartar (Dawes, 1998, Tsuda et al., 1996, Mishima et al., 2007, Mishima et al., 2009, Mishima et al., 2010, Mishima et al., 2011, Mishima et al., 2012). Human tartar is divided into supragingival and subgingival tartar depending on its location. This site-dependent difference also affects the tissue structure and chemical composition of the crystal, and the changes in this crystal depend on the sex and age of the human (Mishima et al., 2007, Mishima et al., 2009, Mishima et al., 2010, Mishima et al., 2011, Mishima et al., 2012).

Periodontal disease-related experiments often involve dogs that are prone to tartar formation (Hamp et al., 1972, Pavlica et al., 2004, Legeros and Shannon, 1979, Loux et al., 1972). Detailed comparative studies on tartar among animal species have not been conducted extensively. 　Therefore, the research subjects vary depending on the purpose, and the oral environment differs depending on the animal species. In this study, we focused on dogs (Lavy et al., 2012), whose salivary pH differs from that of humans, and are often used as laboratory animals. Dogs are companion animals for humans and, similar to humans, have a high incidence of periodontal disease. Therefore, there is growing interest in the prevention of periodontal disease in dogs. Calcite (calcium carbonate; CaCO3) is also present in the crystalline components of tartar (Legeros & Shannon (1979)); however, only a few detailed studies have been conducted. This study aimed to compare the histological structure and chemical composition of human and dog supragingival tartar using histological and analytical methods.