Dental Anatomy: Tooth Numbering Systems

Tooth Numbering Systems

• There are three tooth numbering systems: Palmer, Universal, and International
• These systems are used to document patient treatment and record dental information accurately
• Each system has its own unique notation and method of identifying teeth

Palmer Tooth Notation System

• Most frequently used among orthodontists and practitioners in the United Kingdom
• Divides the upper and lower arch into four quadrants
• Uses simple brackets to represent the four quadrants of dentition
• In deciduous teeth, uppercase alphabetic letters represent the primary teeth in each quadrant
• In permanent teeth, numbers 1-8 are used in each quadrant, starting from the midline

Universal Numbering System

• Adopted by the American Dental Association in 1975
• Uses numbers 1-32 to identify the 32 teeth in the permanent dentition
• Maxillary teeth are numbered from 1-16, starting from the maxillary right third molar
• Mandibular teeth are numbered from 17-32, starting from the mandibular left third molar
• In primary dentition, uppercase letters A-T are used to identify the 20 teeth

International Numbering System (Federation Dentaire Internationale)

• Uses two digits to identify teeth, with the first digit indicating the dentition, arch, and side, and the second digit indicating the tooth position
• For permanent dentition, the first digit is 1-4, and the second digit is 1-8, starting from the midline
• For deciduous dentition, the first digit is 5-8, and the second digit is 1-5, starting from the midline

Tooth Structure

• Each tooth has a crown and root portion
• The crown is covered with enamel, and the root is covered with cementum
• The crown and root join at the cementoenamel junction (CEJ)
• The main bulk of the tooth is composed of dentin

Tooth Surfaces

• The facial surface of the tooth is towards the face or lip

• The lingual surface of the tooth is towards the tongue or palate

• The occlusal surface is the surface of premolars and molars that come in contact with opposing jaw during closure

• The proximal surfaces are the sides of the tooth next to an adjacent tooth, with mesial surfaces facing towards the midline and distal surfaces facing away from the midline### Line Angles and Point Angles

• Line angle is formed by the junction of two surfaces and is named after both surfaces.

• Point angle is formed by the junction of three surfaces and is named after these three surfaces.

Line Angles of Anterior and Posterior Teeth

• Anterior teeth have 6 line angles:
  • Mesio-occlusal line angle
  • Mesio-buccal line angle
  • Mesio-lingual line angle
  • Disto-occlusal line angle
  • Disto-buccal line angle
  • Disto-lingual line angle
• Posterior teeth have 8 line angles:
  • Mesio-occlusal line angle
  • Mesio-buccal line angle
  • Mesio-lingual line angle
  • Disto-occlusal line angle
  • Disto-buccal line angle
  • Disto-lingual line angle
  • Bucco-occlusal line angle
  • Linguo-occlusal line angle

Point Angles

• Anterior teeth have 4 point angles:
  • Distolinguo incisal point angle
  • Distolabio incisal point angle
  • Mesiolinguo incisal point angle
  • Mesiolabio incisal point angle
• Posterior teeth have 4 point angles:
  • Distolinguo occlusal point angle
  • Distobucco occlusal point angle
  • Mesiolinguo occlusal point angle
  • Mesiobucco occlusal point angle

Division into Thirds

• The crown and roots can be divided into thirds for descriptive purposes.
• The crown is divided into:
  • Occlusal or incisal third
  • Middle third
  • Cervical third
• The root is divided into:
  • Cervical third
  • Middle third
  • Apical third
• The crown can be divided in three directions:
  • Inciso- or occlusocervically
  • Mesiodistally (into mesial third, middle third, and distal third)
  • Labio- or buccolingually (into labial or buccal third, middle third, and lingual third)