Thank you for your query.
Cavities in teeth occur because of poor oral hygiene
and not burshing the teeth regularly and especially before retiring in the night. Depending on your son's age further course of action can be planned in consultation with the dentist
. As you have not mentioned your son's age and the number of cavities present it is difficult for me to provide any opinion.
If your son's permanent teeth
have not started to erupt yet then most of the dentists suggest that oral hygiene be maintained. However if the teeth have large cavities then there is no alternative to filling or root canal treatment
I hope I have answered your quer to your satisfaction.