6yr old's new teeth growing up behind milk teeth

KazDub

My 6 year old has two very wobbly milk teeth on his bottom jaw. They don't seem to want to come out though and his two permanent teeth are very well developed behind them. It is the very front two teeth, so I would have expected that regular things such as chewing would have helped loosen them up. I keep asking him to try and wiggle them as much as is comfortable, but he doesn't ever remember to do it.
Is there any need to bring him to a dentist, or is this a common enough thing? I'm worried that due to the limited space, the new teeth won't settle in to the correct gaps.

Dianthus

Sounds about right for lower incisors. However if there is a generalised lack of space& all the deciduous(baby) teeth are very close together, then yes, he might need orthodontic intervention in the next few years. There isn't a whole lot you can correct, space-wise, for a 6 year old though.
As an aside, his first permanent(adult) molars should be coming through about now. It would be important to bring him to a dentist to at least introduce him to the environment. Or you could bring him to the surgery to watch you having a checkup. Then his first experience won't be too traumatic (pain->filling/extraction)
For now, the focus should be on prevention of tooth decay (fissure sealants, oral hygiene instruction, ect) . . Any crowding is easily corrected when the time is right.