periodontics
Academic and clinical term for the study and treatment of periodontal diseases.
He is majoring in periodontics at university.
歯周病学 is sometimes used interchangeably but more narrowly refers to the study of periodontal diseases, while 歯周治療学 emphasizes the therapeutic aspect.
Compound of 歯周 (periodontal) + 治療 (treatment) + 学 (study). A modern academic term.