kadonye wrote:@intelli, I'm referring to the case where the browning affects so many people in one area.There was a time I could guess where one was brought up by the colour of his teeth e.g most of my friends from Nakuru town have this problem.I was told that it's water in those areas that has fluoride.Same applies to parts of Nyanza,Nor th Rift and Central.
A tooth is formed a few years before it comes out of the gum into the mouth. The hard part of the tooth called enamel is made up of Calcium Hydroxyappatite crystals. This is a compound of Calcim, Phosphates and a Hydroxyl group. In places where the water contains too much fluoride SOME of the Hydroxyl groups are displaced by Fluoride ions so that you end up with formation of Calcium Fluoroappatite crystals. The tooth is therefore made up of a mixture of both Hydroxyappatite and Fluoroappatite crystals. Now think of it this way when all the crystals being used to form the tooth are the same size they can be arranged to fit tightly together so that there are no spaces (voids) between them and you get a uniform solid mass with a consistent smooth texture and colour. In the case of a mixture of crystals of different sizes, (Fluoroappatite crystals are smaller than hydroxyappatite crystals) you get voids when the crystals are layered one upon the other. When the teeth come out into the mouth these voids take up stains and the teeth become brown. This also explains why the teeth are not as brown when they first appear in the mouth in fact some are chalky white but continue to stain as the child matures. They also have a rough surface and in severe cases they can chip away.
Please note that the browning effect of the fluoride is from water that has been ingested that means maji imekunywa. It goes into the stomach then the blood then is deposited on the tooth that is forming while it is still under the gum. Fluoride that comes in contact with the teeth in the mouth as in rinsing and spitting does not cause brown teeth.
Why do some people who take the same water not get the same staining? Two reasons:
Teeth are only being formed when they have not erupted into the mouth. All teeth are already formed by the time the child is 8 years old. If after this he starts taking water with excess fluoride his teeth will not be affected. It is the children whose teeth are still forming who are at risk of tooth discoloration. So anyone who takes this water after age 8 will be unaffected.
People can live in the same area but do not take the same water. Some houses have a tank that collects rain water for drinking and kitchen use and therefore the people there though living in an area with high fluoride water do not drink it. Actually this is what is recommended for people in areas with high fluoride levels in ground water (Nakuru area, Muranga, Karen - langata etc) if they have children younger than 8. Adults and children older than 8 need not worry.