As a Pediatric Dentist I get the unique chance to see kids grow from an early age. It is amazing to me to see how much the age a child transitions to hard foods affects their personal dental and facial growth! As I have been practicing for 10 years now I have seen a direct correlation between children who both breast feed and bottle feed past age one and those who do not. Children who have a liquid and soft diet into their toddler years are much more likely to have crowded teeth and more narrow faces.
On the other hand, children who start a hard diet under the age of one, especially those who are eating a majority of solids by 9-10 months, often have many benefits. They develop stronger facial muscles, causing their jaw to widen and giving more room for teeth and tongue. These children also tend to have fewer breathing problems and allergies and tend to sleep better.
If I had a piece of diet advice to give a new parent, it would be to start to introduce basic solids when you start the weaning process at around 8 months old. Continue with solid foods until they eventually replace all breast or bottle feeding by age 1. This will make for stronger facial muscles, better teeth and health.
Dr. Al Burns