why mandibular molars have two roots and maxillary molars three in humans?
535287
the reason is that's the way your God or evolution made it happen...  whatever your belief, some things happen simply because...  \n\nthe truth is that maxillary 3rd molars typically don't have 3 roots.  the root anatomy is usually conical/fused in nature.  the same goes for mandibular 3rd molars.  the root structure is highly variable.  sometimes there can be 4 roots or a single fused root.  the mandibular second molars can have 3 roots or they can be fused as well.  the point is that teeth are highly variable.  genetics and chance play a role in tooth development.  human teeth develop the way they do because of the genetic code and its evolution over time.
142547
X-rays reveal defects in the oral cavity, restorations, supernumerary teeth, the size, shape, and position of teeth.
109455
Hystricomorphy, a unique muskoskeletal pattern involving the jaw, enables the mouth to be opened in a large gape. \n\nHystricomorphy is characteristic of the hystricomorph rodents, but has also now been found in the extinct saber-toothed Barbourofelis. \n\nAlthough it is believed that a highly-detailed phylogenetic analysis should spot the independent acquisition of the two complexes of traits, it is acknowledged that supposedly-unique character complexes could arise through convergence and ‘fool’ the evolutionist into believing that they had arisen from common ancestry. (What qualifies as a chimeric creature?)
114968
Norm is correct.  An adult can still have deciduous teeth and generally the reason is because a permanent tooth never developed to push it out and take its place.
880714
The human dentition has 32 permanent teeth.
1071305
The axial skeleton forms the central axis of the body. It consists of the skull, the vertebral column, the ribs and the sternum or breastbone.  There are 80 bones total in the axial skeleton, and I'm sorry but I'm not going to type them all out for you.  I will, however, provide you with some links so that you can see what they are if you need to know all 80.  They have great diagrams.\n\nhttp://webschoolsolutions.com/patts/systems/skeleton.htm#axial\nhttp://www.botany.uwc.ac.za/sci_ed/grade10/manphys/axial.htm
59263
Abutment teeth are used for the support of a prosthesis. For example, if you get a bridge to fill a gap where a tooth was, the two teeth on the sides (abutment teeth) will support a prosthetic tooth in the middle where the void is.  So a bridge looks like this:\n[crown over abutent tooth]-[prosthetic]-[crown over abutment tooth]   (making a 3 teeth prothetic in one piece to fill the void).\nHope it helps.
62243
because man has incisors, canines and molars..\n\ncanines to rip and shred.. incisors to slice and bite off ...and molars to chew.
152264
Yes.  Maxillary is the upper arch and mandibular is the lower arch.
1176853
Wisdom teeth are third molars that usually appear between the ages of 18 and 20 (although they may appear when older, younger, or may not appear at all). They are called "wisdom teeth" because they appear so late—much later than the other teeth, at an age where people are supposedly wiser than as a child, when the other teeth erupt. Often they need to be removed when they impact against other teeth—colloquially known as "coming in sideways."\n\nWisdom teeth are sometimes described as an example of a "vestigial" trait. Some argue that recent changes to softer diets which cause less wear on the teeth may be causing the third molars to be less useful, and, in fact, problematic in many humans. Alternately, it is possible that wisdom teeth were useful when it was common for humans to lose several teeth to decay by the age when they appear.\n\nAlthough most people have four wisdom teeth, it is possible to have more or fewer. Absence of one or more wisdom teeth is an example of hypodontia. Any extra teeth are referred to as Supernumerary teeth. [1] [2]
299858
it is thought that the apple exercises the gums. Improves bllod hence stops gum disease. the teeth are attached to ligament like structures within the gum and these are able to move up and down. Our modern day diet stops this process from happening because it's too soft. As cavemen we would have been eating raw meat and veg. They didn't have tooth brushes then and yet the skulls are often found with teeth intact thousands of years later.
935047
1) holy crap you're asking that here? :P\n\n2) shark's tooth can hold a smaller sample.\n\n3) can get more lanes with a shark's tooth comb.
983435
If it's a baby tooth, it's just the way they fall out.\n\nIf it's not a baby tooth, it doesn't have room in the arch.  This is most common with lower premolars (bicuspids) and it is due to taking out a baby tooth too early instead of doing the children's version of root canal treatment.  The tooth usually grows out towards your tongue.  This needs to be evaluated by your dentist to see if it can be corrected or if it should just be removed.\n~
1125908
4th molars are exquisitely rare but i have definitely seen them before.  in fact, when i was in dental school i saw a prisoner that actually chewed with his 4th molars.  most of the time they are tucked up behind your eyeball they are so far buried in bone.  having one removed should actually be easier than a third molar simply because it's such a small tooth.\n\nyou are special for sure.
1040304
The tooth is basically encased in bone. They usually cut away the "roof" of bone and a little bit around the tooth to get it out. The hole that is left over usually fills back in with bone and shouldn't cause any problems.
873122
I think the #3-#4 issue is just coincidence.  I wonder if you have a sinus infection, though.  The roots of these teeth are literally right at the lower border of the sinus.  You might even have a sinus perforation, which is not uncommon with #3 extractions.  Take a deep breath of air, pinch your nose and try to blow the air out through your nose.  Don't use a crazy amount of force, but just enough to see if the air holds in your nose or if it is leaking into your mouth.  (Yes, that's right.)  If it is getting into your mouth, you need to have this opening closed by an oral surgeon.\n\nAt a minimum, I suggest that you might need an antibiotic to clear up your sinus, which may have a lingering infection from your tooth.  (Biaxin or Zithromax are a good choice for sinus infections.)
207782
I'm a genetic anomoly.  I've lost particular teeth two and three times and had hem grow back.  I had some extra teeth.  Even now, at the age of 28 and with all my adult teeth fully surfaced, I have seen in my X-rays a nascent incissor in my skull--and that's a tooth I've lost twice already.\n\nNormal people only get to lose their baby teeth once, but freaks like me have extra sets of teeth.