、。
Mr. Suzuki is not a dentist — he's a physician.
Literal
Suzuki-Mr. [topic-は] dentist [copula-ではなく], internist [copula-だ].
ではなく ('is not X, but rather Y') is the contrastive negation + conjunctive form of the copula, a standard way to express 'not X but Y.' 歯科医 (dentist) and 内科医 (internist, internal medicine doctor) are specialized medical terms — 科 is the suffix for medical departments.