I would check another denist. My six year old just had his front tooth pulled at the denist. It was a baby tooth and an infection and need to come out before it effected the adult tooth.
She gave me three options, num his gum in the office, go to another place to have laughing gas, or have him put under.
I choose the office and numbing because he is an easy going kid and I knew he would sit and let them do it. He did very well the last couple pulls he reacted to. He told them it hurt but no tears or anything. They gave him a matchbox and off he went. Now he tells ya they wrenched out my tooth and smiles to show the gap.
I know my oldest daughter would not be able to handle it if she needs to have it done. Her, I would have to have knocked out so she doesn't see, hear or feel anything. She stresses over everything.
If you think he will not sit still I would think about taking him to a place that will put under general anastia (sp?).