Your son being afraid of the dentist
is quite common. The dentist office has the unfair reputation of being a place where there are drills, pain, and things that taste bad. Sometimes, parents have to bribe their kids to go to the dentist willingly or take them against their will. This is where skilled parenting becomes important. Making sure your kids know that you are the boss, but also you will protect them from anything that would hurt them.
I suggest that you contact your dental office prior to your next appointment for your son. Explain to the staff about your son's fear so that they know he has this problem. If they know that he is afraid of what might come next, they are more likely to be sympathetic and helpful when he is getting his examination. Keep in mind that these types of issues are common in kids and he should grow out of it soon. You should also discuss the issue with your son's pediatrician
at his next visit. Sometimes it takes another perspective from a person experienced with kids to understand a fear such as this one. Good luck.