9 year old front teeth won't erupt

[Rita Doshi]

My son had 2 mesiodens that were extracted by an oral surgeon last year. We found the mesiodens when his front permanent teeth wouldn't come. The dentist extracted the 4 baby teeth and after a couple of months looked closely and found mesiodens. It's been a year since his mesiodens were removed. Out of the 4 teeth, the first on his left side has erupted although I feel it's not out all the way. I see 2 in the gum. I can even see the white color thru the gums but it's been like that since last 6 months. They won't erupt. The dentist cannot find the 4th tooth. The dentist also said that the root hasn't been formed for the 2 teeth that are visible in his gums. Any advice ?