The objective of this study was to compare the efficiency of the dental diagnostic and procedural coding systems between general public health database (ICD-10/ICD-9-CM), the dental public health database (CDT), and ICD-10-TM. The study was performed in 3 aspects, i.e. coverage, discrimination ability, and accuracy. For the coverage, the manuals were compared to the dental procedural checklists and patients’ records from the Dental Department, Thammasat University Hospital. For the discrimination ability, the manuals were compared to the checklists, and the unclear codes were identified and analyzed. For accuracy, coders who want to ICD workshops performed the 40 diagnostic and procedural code tests. The coverage of the procedural codes of ICD-9-CM, CDT, and ICD-10-TM was 72.7%, 92.1%, and 92.6% respectively, while the percentage of unclear codes was 9.6, 4.4, and 3.2 respectively. The accuracy of diagnostic code in ICD-10 was 69.3%, and ICD-10-TM was 78.4%. The accuracy of procedural code in ICD-9-CM was 37.2%, CDT was 40.5%, and ICD-10-TM is 41.3%. It can be concluded that ICD- 10-TM provides more accuracy than ICD-10 for diagnosis, with more details. For procedural coding system, ICD-10-TM was
comparable to the dental public health database CDT, in terms of its properties. However, its coverage and discrimination ability are clearly better than ICD-9-CM.