Judging by the before and after photos, it is obvious that Seacrest has changed dramatically through the years. It wouldn't be an exaggeration to say that he underwent some pretty intense plastic surgery to look like that.
It is apparent that Seacrest had a quick fix to his teeth by getting veneers, a really expensive teeth treatment that the majority of celebrities prefer.
It is evident that Seacrest's nose used to be very bulbous in the past, but now the shape of his nose is changed as the roundness of his nasal tip is reduced, an obvious indication of a nose job.
When asked about how he keeps himself looking young, Ryan Seacrest has never revealed his secret. For instance, when someone asked how he looks younger than his age Ryan Seacrest comically replied: "placenta." In addition, Ryan Seacrest has been quoted stating the following about botox: "I've never done Botox in my life. But I've probably tried everything else under the sun."
Conclusion: Whatever plastic surgery procedure Ryan Seacrest undergoes, it is obvious that works for him as he appears younger than his actual age.