title: Selection of an experimental unit in rat caries studies.
abstract: In two separate experiments, none of the 14 subunits examined consistently ranked dentifrices similarly to the ranking obtained when the individual rat was used as the experimental unit. Arbitrarily dividing the rat into subunits and then comparing results among these subunits may lead to false conclusions since the rankings using subunits vary within each experiment and from experiment to experiment.
mesh_terms: D000818:Animals; D002118:Calcium / Q000627:therapeutic use; D003731:Dental Caries / Q000517:prevention & control*; D003802:Dentifrices / Q000627:therapeutic use; D004195:Disease Models, Animal; D005460:Fluorides, Topical / Q000627:therapeutic use; D010710:Phosphates / Q000627:therapeutic use; D010919:Placebos; D011676:Punched-Card Systems; D051381:Rats; D012107:Research Design; D012964:Sodium / Q000627:therapeutic use; D014001:Tin / Q000627:therapeutic use
chemical_list: D003802:Dentifrices; D005460:Fluorides, Topical; D010710:Phosphates; D010919:Placebos; D014001:Tin; D012964:Sodium; D002118:Calcium