Hmmm. I see what you're saying... (and damn if it isn't hard to analyze your own pronounciation without getting into the worst case of observer-effect you ever heard tell of. Bloody feedback loop, anyway.)

I'd swear some people insert a vowel between the t and r.

After reading through much of Wikipedia's information on dental consonants, I've come to the conclusion that I just speak differently to other people. (T, D, N and L are listed as dental, but I pronounce them in an alveolar fashion. TH, now, that one's dental.)