Some will say as soon as the baby gets teeth (seemed a little early to me). Others say at a year. That's a good time to get an early start.
I took my son when he turned 2. It was great for him, and we've had his twice a year check ups ever since.
I took my daughter for a first visit (no x rays nor exams, just look in the mouth and get her comfortable with the dentist) at 2. He looked her over and told me that I could wait until she was closer to 3 to bring her again. She's very shy and since her teeth showed no signs of decay, he said, "Keep up the good work brushing!" and said we could wait.
We have great dental coverage, though, so I didn't hesitate to take them early.
At this age, no, you don't need to take her. If you brush her teeth, don't let her go to bed with a bottle (what they call "baby bottle-itus") and she has no accidents, you can probably safely wait until 2. Or even later. Many don't take their kids until 3 or 4.
I personally wanted my children to be very used to the dentist, and I wanted dental care to be completely preventative (as in, preventing problems instead of fixing problems). I didn't want to wait until 3 or 4 and find that my kids already had decay and cavities. By taking them early, i feel like we've gotten a great start and we're not having to react to any tooth problems, KWIM?