Dental anatomy
Dental anatomy is
defined as the study of human tooth structures development, appearance, and
classification of teeth fall within its purview the study of dental anatomy,
physiology, and occlusion. This provides one of the basic components of the
skills needed to practice all phases of dentistry.
Formation of the Dentitions
Humans have two sets of teeth in their lifetime, the first
set of teeth to be seen in the mouth is the primary ("baby")
teeth, then those primary teeth are replaced by the permanent
teeth. The term "deciduous teeth" may be used in place
of "primary teeth”. "Succedaneous teeth” refers to those teeth of the
permanent dentition that replace primary teeth.
Primary teeth begin to form prenatally at about 14 weeks in
utero and is completed postnatally at about 3 years of age. The first permanent tooth in this
dentition begin to appear in the oral cavity at the mean age of 6 months old,
and the last emerge at a mean age of 28 ± 4 months.
The first permanent tooth erupt at the age of 6 years old
and The last tooth erupts at the age of to 24. The deciduous Usually, there are
20 primaries teeth and 32 permanent teeth, the last four being third molars or
"wisdom teeth", each of which may or may not grow in.
The denomination of each tooth is often represented by the
initial letter in its name for example I for incisor, C for
canine, P for premolar, M for molar.
The usual eruption sequence of the deciduous teeth
The first deciduous molars erupt before the canines leaving
a space close to the lateral incisor in each quadrant. Contrary to what is
known for the permanent teeth, eruption of the deciduous teeth occurs earlier
in boys than in girls, and the maxillary deciduous teeth precede their
mandibular counterparts.
The
only exception is the mandibular central incisors, which are usually the first
teeth to appear. Also sometimes however the mandibular second molars precede
the corresponding maxillary molars. The deciduous teeth are generally
characterized by interproximal or physiologic spacing. This spacing is more
between the maxillary teeth than the mandibular teeth.
Nomenclature
The first step in understanding dental anatomy is to learn
the nomenclature, or the system of names, used to describe the teeth.
The denomination of each tooth is often represented by the initial letter in its name for example I for incisor, C for canine, P for premolar, M for molar.
Tooth Numbering Systems
NOTATION SYSTEM
These are the systems designated to identify the type of each tooth and its location in each quadrant of the dental arches. Some of these systems are more commonly used in certain countries than others.
Notation systems are used by dentists for identifying and referring to a specific tooth. They are used as quick short cut in clinical record keeping.
The three most common systems are the Palmer notation system. the FDI World Dental Federation notation, and the universal numbering system.
Palmer Notation System
This system is used in Middle East: it is based on denominating the teeth in each quadrant of the dental arches. The permanent teeth are given the numbers 1 through 8, beginning with the 1st incisor and ending with the third molar for each quadrant.
The deciduous teeth are given the letters A through E again beginning with the 1st incisor and ending with the 2nd molar for each quadrant.
The teeth are arranged in two crossed lines representing the 4 quadrants of the dental arches. Each quadrant begins with the initial number or letter close to midline and ends with the last number or letter-designated.
For the permanent teeth uses the numbers 1 through 8.
For the primary teeth uses capital letters A through E.
In this system the arches are divided into crossed lines
representing the 4 quadrants with
the entire dentition being stated as follows:
Palmer notation system
for the permanent teeth
Palmer notation
system for the deciduous teeth
............................................................................................................................................................
For each identification a bracket with a vertical and a horizontal line.
The Two Digits System
FDI (federation dentaire internationale) or two-digit system
Each tooth is identified by a unique two-digit combination. The first digit
identifies the quadrant of the jaw and the second digit identifies the tooth
within the quadrant. Quadrants are allotted the digits 1-4 for the permanent
and 5-8 for the deciduous teeth in a clockwise sequence and starting at the
upper right side. Teeth within the same quadrant are allotted the digits 1-8
(deciduous teeth 1-5 from the midline backwards. The digits must be pronounced
separately.
a) 1
to 4 for the permanent dentition.
b) 5 to 8 for the deciduous dentition.
The second digit indicates the number of the tooth within
any quadrant. Starting from the midline the numbering are 1 to 8 for
the permanent teeth and 1 to 5 for the deciduous teeth.
For the applications of this system
*The first digit is always the number of the quadrant
indicating whether
the tooth is permanent or deciduous.
*The second digit is the number of the particular tooth
within the quadrant
therefore all teeth in one quadrant would have
similar first digit.
The two digits should be pronounced separately e.g.
The right maxillary permanent central incisor is 11 (one one,
not eleven).
The right maxillary lateral incisor is 12 (one two).
Sometimes a dot is inserted between quadrant code and tooth
code in order to avoid indistinctness with other numbering systems e. g.
41 or 4.11 right mandibular permanent central incisor.
81 or 8.1 right mandibular deciduous central incisor.
The FDI system is the system, of choice worldwide. It is
adopted by the World Health Organization (WHO) and is accepted by many other
dental organizations.
The FDI two - digit system complies with the following basic
requirements. It is:
1. Simple to understand and to teach.
2. Easy to pronounce in conversation and dictation.
3. Readily communicable in print and by wire.
4. Easy to translate into computer "input".
5. Easily adaptable to standard charts used in general
practice.
The Universal National System
in the deciduous, consecutive uppercase letters (A-T) are
assigned to identify the teeth Letter A is assigned to the
second molar of the patient's right side of the upper arch, upper left molar
is K and following that arch to the terminus of the
lower jaw, the lower right primary second molar is T.
In the permanent, teeth are numbered 1-32 starting
with the upper right third molar clockwise terminating at the lower right third
molar.
The permanent teeth are number 1 through 32 starting
at the end of the right maxillary quadrant.
The deciduous teeth are designated with the capital
letters A through T.
The number or letter used in this system is always preceded
by the sign # to indicate that the system used is the Universal System. The
two-digit system and the universal system have the advantage that you simply
have to mention the letter or number of the tooth without indicating which
quadrant either verbally or with a bracket.
Example:
82 Right mandibular deciduous second incisor.
Left mandibular deciduous second molar.
# 32 right mandibular permanent third molar.
#A right maxillary deciduous second molar.
#A right maxillary deciduous second molar.
