Youngest Age for Getting Dental Implants?

I am 18 years old. My front four teeth (two top and two bottom) are missing. After undergoing 2-3 years of periodic root canal to keep the teeth, I had them removed, and a denture made (only for my top two teeth). I have used it for about 5 years, and I was advised that the best option would be dental implants, but these were not viable until I was 18 years old.That time has now come, and the same dentist has advised that “Implants are generally placed in patients who are at least 25 years of age as placement any earlier could result in subsidence of the implants.” He has suggested an anterior bridge. I have been saving for dental implants and putting off travel and study until my mouth is sorted, I suppose it is a mental roadblock in my mind. I don’t feel like I am growing any more (I’m 6″5′ so I hope I’m not) and my question is what has changed which means 25 is now the advised age, and are implants still an option? Or should I look into an anterior bridge?