Is the word dentista the same in Brazilian and European Portuguese?

Yes

The word "dentista" is identical in meaning, spelling, and grammar in both Brazilian and Continental Portuguese. The only difference lies in pronunciation. In Brazilian Portuguese, the vowels are generally more "open" and clearly articulated. In Continental Portuguese, unstressed vowels (like the "e" in the first syllable) are often "reduced" or "closed," sometimes becoming almost silent, making the word sound more like "d'ntista."

Brazilian Portuguese Examples

• Eu preciso marcar uma consulta no dentista. (I need to schedule an appointment with the dentist.)
• O meu dentista é muito legal. (My dentist is very nice.)
• Você foi ao dentista ontem? (Did you go to the dentist yesterday?)
• Estou com uma dor de dente e preciso de um dentista. (I have a toothache and I need a dentist.)
• O dentista me disse que está tudo bem. (The dentist told me that everything is fine.)

Continental Portuguese Examples

• Tenho de marcar uma consulta no dentista. (I have to schedule an appointment with the dentist.)
• O meu dentista é muito atencioso. (My dentist is very attentive.)
• Já foste ao dentista este mês? (Have you [informal] been to the dentist this month?)
• Fui ao dentista fazer uma limpeza. (I went to the dentist to get a cleaning.)
• O dentista disse-me que está tudo bem. (The dentist told me that everything is fine.)