RÉSUMÉ
BACKGROUND: A previously described economic model was based on average values for patients diagnosed with chronic periodontitis (CP). However, tooth loss varies among treated patients and factors for tooth loss include CP severity and risk. The model was refined to incorporate CP severity and risk to determine the cost of treating a specific level of CP severity and risk that is associated with the benefit of tooth preservation. METHODS: A population that received and another that did not receive periodontal treatment were used to determine treatment costs and tooth loss. The number of teeth preserved was the difference of the number of teeth lost between the two populations. The cost of periodontal treatment was divided by the number of teeth preserved for combinations of CP severity and risk. RESULTS: The cost of periodontal treatment divided by the number of teeth preserved ranged from (US) $1,405 to $4,895 for high or moderate risk combined with any severity of CP and was more than $8,639 for low risk combined with mild CP. The cost of a three-unit bridge was $3,416, and the cost of a single-tooth replacement was $4,787. CONCLUSION: Periodontal treatment could be justified on the sole basis of tooth preservation when CP risk is moderate or high regardless of disease severity.