P.S.
I just took my almost 3 yo son to the dentist. I would suggest a pediatric dentist. They have experience with helping kids who are younger. It makes a difference.
We talked about what to expect ahead of time- sitting on my lap in the big cool chair, the lights, how the dentist has special tools to help his teeth stay healthy and strong. He knew the dentist would count his teeth. I tried for a few weeks to get him used to my fingers in his mouth and getting him to open wider and stay open wide while brushing. We talked about it every day for many days in advance.
When we brush I try to get him to copy me and open my mouth super wide, or roar like a tiger, sing, or yodel like Tarzan... anything to get those teeth apart enough for me to really see and brush.
At the dentist he sat on my lap. The bright lights bothered him, so he wore sunglasses. For part of the time I also covered his eyes with my hands. It was a pretty quick process, but he did better because he knew what to expect.