Marco is considering that people will always need dentists because he knows we all have teeth and we should go to the dentist at least once a year to get dental cleaning and thus avoid or prevent cavities; besides, a lot of people get cavities and then, older people usually need to get replacement dental pieces. So, we can say Marco considers it is safe to start his own practice beause he is confident that he will be able to get enough patients to keep it going.
Marco is confident that he will always have work as a dentist and that he will be able to settle his own office. The reason is that people have always required dentists to examine their teeth and in the future they will invariably need specialized professionals who take care of their teeth as well.
