Xray -how much does that lead sheet really protect you?

You're pretty safe. Here's a link showing the amount of radiation you can get from various dental x-rays. Compare those millirem values (1/1000 of a REM) to the limit for occupational exposure (3 REM per quarter, 5 REM per year). Stay below 1000 x-rays per quarter and you should be fine.

Then why the lead sheet in the first place? Just to kind of make us fools feel better? And why don't we cover our brains? Well for me it may be that my skull is so thick.

lol

Perhaps the lead apron is so they don't have to inquire about possible pregnancies. Do guys get the lead apron too?

Yes, we do.
And I make sure mine is long enough.

The dentist always asks this question. Could you be pregnant? I've only answered yes once. Usually I say I am 99% sure I am not.

At least for routine dental xrays - the dentist will not take an xray if you say yes to this question. The one time I did, the dentist got all giddy and excited (most women must answer the question no I guess) and he informed me it was good to know as he would not take an xray then.

The site Engineer linked is quite informative, although the article failed to acknowledge the effects of the concentration of the dose in a dental X-ray to the "skin" area around the mouth (as opposed to the equivalent full body dose). These doses as tabulated for a single X-ray are fairly high, though well below the threshold at which any disease effects can be inferred from a statistical analysis of large populations.

One error in the article - the increase in the background dose resulting from a move from a city at sea level to Denver is much higher that noted in the article - the increase is more on the order of 350 mrem/year whole body dose - an amount more than twice the legal limit for radiation workers in this country. Moreover much of this increase comes from the radon gas that is ubiquitous in mountainous areas with lots of granite in the soil: this is one of the more dangerous ways of getting radiation in that it occurs inside your body from the inhaled gas. Moreover the decay product is a particle which stays in the lungs and is itself radioactive.

The largest source of public radiation is cosmic - from the sun. Next is from terrestrial radon. Medical diagnostic X-rays, airline travel, radiation from the burning of coal, and self radiation from the radioactive elements within our bodies come next. Radiation from nuclear power plants doesn't even make the top twenty sources.

The lead apron in the dental or medical office is mostly for the patient's psychological comfort.

I figured as much - the lead sheet thingy. Logically it makes more sense to wear a tin foil hat than a lead apron over your body when the xray machine is pointed right at your mouth and even pointed up a bit. It isn't directed at my body so it would seem more radiation is pointed at your brain and my brain is a bit important to me (I can see George's point of view as a man is more concerned about a different part of his anatomy).

And also you don't cover up for a mamo...

This one male friend of mine in college - used to cover his waist area with books when walking out of the library at college. He was concerned that the detector thing (the one that makes sure you are not trying to steal books) would make him impotent.