So, as a parent, you should never let your child miss the optimal age for orthodontic treatment, which is defined as 12 years old. However, if there is an inherent deformity of bone development, functional orthodontic appliances need to be fitted from the age of 9 weeks.
Aggressive treatment at 12 years of age is fully capable of correcting bite disorders and facial deformities. If you miss the optimal age for orthodontic treatment, your teeth will only be able to move slightly and will be prone to relapse later.
So it is important to be aggressive in childhood. After orthodontic treatment in adulthood, some problems do exist, such as resorption of the alveolar bone and resorption of the roots of the teeth.