I can give you a reasonable idea. Could refine it with top-down and profile shots of the lower jaw, better wear indicators than the uppers.
Based on what I see here, this guy is around 1/2 way through the useful life of his teeth (if nothing else kills them first, deer and elk starve to death when their teeth wear out). That useful life varies from 8-9 years in low elevation resident bucks in the sagebrush, to 13-14 years for mountain migratory bucks. Based on where you killed him, the latter applies.
I think Rock is spot-on, though I'd be less surprised if he was 6.5 than if 8.5; I would estimate he is most likely 6.5, next 7.5, and less likely to be 5.5 or 8.5 - but more likely to be 8.5 than 5.5. I'm highly confident in the no less than 5.5, no more than 8.5 range.
If you have the lower jaw, I would be pretty confident in estimating age +/- 1 year. To get closer than that, you'd have to send the two center front incisors to Mattson's lab in MT; it's worth the $40 or so to some guys to have the most precise estimate possible.
Interesting, I would think that the higher elevation bucks would have a shorter lifespan than deer in the foothills. Why is that? More grass rather than tough sagebrush? never even thought about it.
You guessed right - teeth wear faster when the deer are on cured out forage for six months of the year instead of three. In addition, dust coats the forage much of the time in summer, adding grit that also wears teeth faster.
