Make your own free website on Tripod.com

Welcome to Dr Antony George's Website

My Homepage

Know your teeth

Human beings have two sets of teeth ---- Primary (milk teeth) and Permanent. There are 20 primary and 32 permanent teeth. In some people one or more teeth may be absent, or they may have some extra teeth (supernumerary). Usually the first primary teeth erupt by 6 months and the first permanent by 6 years of age. Children loose their milk teeth between 6 and 11 years of age. By the age of 13 years almost all the permanent teeth have erupted: 8 incisors, 4 canines, 8 premolars and 12 molars. The last 4 molars commonly known as wisdom teeth appear much later, between 18 to 21 years. The main function of your teeth is to chew and cut food. Anterior teeth are used to bite and tear food while the posterior teeth help in chewing. Hence your dental health is an important part of your general health and your overall well-being. teeth
A tooth mainly has four layers:
  1. Enamel
  2. Dentine
  3. Pulp
  4. Cementum
Enamel is the outermost layer of the tooth and also the hardest tissue in the body. It protects the other structures of the tooth and gives the tooth the strength to bite into anything. It is a translucent layer and depending upon its opacity a tooth appears whiter or yellowish.
Dentine lies below the enamel and forms the bulk of the teeth. It is an ivory like substance and is highly resilient, and absorbs all the pressure you exert on your teeth while chewing. Erosion of enamel due to carious lesion exposes this surface to the oral cavity and the tooth becomes sensitive to a variety of stimulus.
Pulp is the central portion of the tooth and is composed of blood vessels and nerves. If a carious lesion is not treated at an early stage it reaches this area causing severe toothache. Once the infection reaches the pulp the tooth can be saved only through Root Canal Treatment [RCT].
Cementum is the outer most layer of the root portion of the tooth and is usually under the gum line. Gum diseases cause the gums to get separated or recede from the tooth surface exposing the cementum. This makes the tooth sensitive to extreme temperatures and to sweets.

CROWN ---- This is the part of the tooth that you can see above the gums.
ROOT ---- This part of the tooth within the bone, below the gums. The root of your tooth is usually twice as long as the crown. The anterior teeth usually have one root while the posteriors may have two to three roots. Each root have a root canal inside, which contains the pulpal tissues. If decay spreads into the pulpal tissues then a root canal treatment (RCT) will be required to save the tooth.
PERIODONTAL LIGAMENT ---- This tissue supports the tooth and holds it in place in the bony socket surrounding the tooth. It cushions both the tooth and the surrounding bone against the shock of chewing and biting. During an periodontal disease these ligaments are destroyed and the tooth becomes mobile.
GUMS ---- Dentists call this the "gingiva." It covers the bone surrounding your teeth. You should brush and floss daily to maintain the gingival health.
BONE ---- The roots of your teeth are anchored by bone. A healthy tooth stimulates and keeps the bone tissues healthy.

Eruption Dates and Sequence of Eruption
decidious teeth/eruption                permenent teeth/eruption

There are 20 primary and 32 permanent teeth. Only 20 milk teeth fall off and new permanent teeth erupt in their place, the rest of the 12 permanent teeth erupt directly into the mouth, they have no predecessors, i.e. all the molars erupt directly into the oral cavity.

The first teeth to erupt into the oral cavity are the lower centrals (middle) teeth at about the age of 5 months, then the upper two central incisors at 6 months. Next to erupt are the lower two lateral incisors, followed by the upper two lateral incisors. By 1 year the lower first molars erupt, soon followed by upper first molars. Then the lower canines and the upper canines. Lower second molars and the upper second molars erupt into the oral cavity when 2 years of age. By 6 years the lower deciduous central incisors are lost and the permanent central incisors erupt. Then the upper centrals. During the same period (6 years) the first permanent molars also erupt directly into the mouth, behind the deciduous second molars. Next is the lower laterals, upper laterals, upper first premolars, lower canines, lower first premolars, lower second premolars, upper canines, upper second premolars, respectively. By 12 years the second molars erupt directly behind the first molars. The third molars or wisdom tooth erupt only by 18 - 21 years.

Sometimes the jaws are not large enough to accommodate the last molars. Theories postulate that in modern (more evolved) human beings the jaws are smaller and less developed than those of our prehistoric predecessors. The cooked and soft foods does not require big strong jaws to chew, unlike the uncooked fibrous foods eaten by prehistoric man. Theories also suggests that as the human race continues to develop and evolve, there will be some point in the future when human beings will no longer have wisdom teeth. In fact, even now in the general population some people don't have wisdom teeth.

If the milk teeth are lost at an earlier age due to carries, trauma or any other cause, the permanents may get delayed to erupt into the oral cavity. The permanents erupt only when 1/2 to 1/3 of the roots of the tooth has been formed. Sometimes the gums may get fibrosed or thick if the deciduous are lost early and may require surgical intervention for the normal eruption of the permanent teeth. Supernumerary (extra tooth) are common in between the upper centrals (mesiodens). This will require earlier extraction to allow proper positioning and normal eruption of the centrals.

When the permanent lower or upper centrals erupt by 6 years it is common for them to erupt inside the deciduous incisors. Later they get pushed out into the arch. Sometimes the upper permanent incisors may get locked behind the lower permanent incisors. This will require interceptive orthodontics to bring the upper incisors into normal occlusion (bite). Interceptive orthodontics may also be required if the child has mouth breathing, thumb sucking or tongue thrusting. Serial extractions may be done to prevent proclination of teeth. In many cases after all the care taken the teeth may erupt misaligned (crooked) and will require  orthodontic correction after all the permanents have erupted (12 - 13 years), for a beautiful smile.

Deciduous or Primary Teeth (Milk Teeth)
Name of the Tooth Number Eruption Date Shedding Date
Central Incisor 4 Nos:
2 upper
2 lower
6 - 10 months 6 -7 years
Lateral Incisor 4 Nos:
2 upper
2 lower
10 - 16 months 7 - 8 years
Canine 4 Nos:
2 upper
2 lower
11/2 - 2 years 9 - 12 years
First molar 4 Nos:
2 upper
2 lower
1 - 11/2 years 9 - 11 years
Second molar 4 Nos:
2 upper
2 lower
2 - 21/2 years 10 - 12 years
Permanent Teeth (Adult Teeth)
Name of the Tooth Number Eruption Date
Central Incisor 4 Nos:
2 upper&2 lower
6 - 7 years
Lateral Incisor 4 Nos:
2 upper&2 lower
7 - 8 years
Canine 4 Nos:
2 upper&2 lower
11 - 12 years
First premolar 4 Nos:
2 upper&2 lower
10 - 12 years
Second premolar 4 Nos:
2 upper&2 lower
11 - 12 years
First molar 4 Nos:
2 upper&2 lower
6 - 7 years
Second molar 4 Nos:
2 upper&2 lower
11 - 13 years
Third molar (Wisdom Tooth) 4 Nos:
2 upper&2 lower
18 - 21 years

 

* My Homepage * Know your teeth * Know your Gums (Gingiva) * Eruption Dates * Six Golden Rules * Brushing\Flossing Technique * Wisdom tooth * Tooth Decay * Extraction * Dental Implant * Surgical Extraction * Orthognathic Surgery * Asymmetry of the face * Gummy Smile * Prognathism{Long Jaw} * Beggs\Straight wire{Orthodontia} * Bleaching{Tooth Whitening} * Habit Breaking * Interceptive Orthodontics * Discolouration\Veneers * Composite\Amalgam Fillings * Root Canal Treatment{RCT} * Crown{Porcelain\Castmetal} * Flap Surgery/Splinting * Bridges{Porcelain\Castmetal} * TMJ (Joint) Disorders * Bell's Palsy {Facial Paralysis} * Ankylosis{Difficulty in mouth opening} * Cleft Lip and Palate * Trigeminal Neuralgia * In a Lighter vein


This site is produced, designed and maintained by
Dr Antony George, Trichur Institute of Head And Neck Surgery (TIHANS),
Shornur Road,Trichur,Kerala-680001,India.
Ph: 0091-0487-335145, 335185
email me
This page is best viewed with IE4+ or Navigator4+ at 800*600px.
copyright ŠAug 2000. No part of this website may be transmitted or reproduced in anyway. Every effort has been made to supply correct and accurate information, but I assume no responsibility for its use.

updated Aug2002.