Finding appropriate caries treatments is of paramount importance in dental decision making. That is, finding restorative treatment alternatives predicated on the dental disease and findings are advantageous and gainful in dental restorative decision making. The most immediate problem in clinical decision support systems in dentistry is to capture a doctor's clinical knowledge of treatments. This study is to specify the inter-relations among disease, anatomy, and treatment for restorative treatment decision support, and to conceptualize restorative treatment. As an explanatory example, we expound the developmental process of our ontology, and the formal approach used, for caries treatment.