In their close collaboration, dentists and dental technicians need to be able to refer to specific teeth clearly. The term mandibular left second molar is correct and clear as it stands, but it is far too long-winded. Based on the dental formula, various notations have been developed to allow clear communication when referring to the teeth within each dental arch.
The Zsigmondy-Palmer system (also called the Set-Square or Chevron system) names the teeth as the observer sees the dentition from the front. The teeth are numbered consecutively from one to eight starting from the midline to the back, so that the same teeth in the four halves of the jaws (maxilla and mandible, left and right) are given the same numbers. The numbers are arranged in a cross, where the lines of the cross indicate the occlusal plane (horizontal) and the middle of the face (vertical).
The tooth notation is written as one sees the teeth when sitting opposite someone and looking into that person's mouth, ie, the directionals right and left refer to the patient's right and left. An individual tooth is identified by drawing a section of the dentition cross and writing the number assigned to the tooth in it; for example, a maxillary right first molar is represented as 6 (Fig 1-16a).
For the primary dentition, the notation follows the same pattern as the permanent dentition, but the teeth are named using lowercase letters in the cross:Thus, the primary mandibular left second molar is designated.
Federation Dentaire Internationale (FDI) tooth notation is the two-digit system of notation for the permanent and primary teeth that was introduced internationally on January 1, 1971. The maxilla and mandible are divided into four quadrants: maxillary right (1), maxillary left (2), mandibular left (3), and mandibular right (4).
Starting from the midline of the arch and moving distally, the teeth are numbered consecutively from one to eight, and the number of the quadrant is placed in front of the tooth number (Figs 1-16a and 1-16b). Tooth 36 is therefore the mandibular left first molar.
The FDI notation for the primary teeth uses the following consecutive numbers to name the quadrants: maxillary right (5), maxillary left (6), mandibular left (7), and mandibular right (8). The primary teeth are numbered from one to five, starting from the midline of the arch (Fig 1-16c). Thus, the primary mandibular right first molar is designated 84.
The Haderup system (or European system) is set out like a cross, but the maxillary teeth are denoted with a plus symbol (+) and the mandibular teeth with a minus symbol (-).The position of the symbol denotes which half of the jaw it refers to: in front of the tooth number (ie, to the left) means the left side, and after the number (ie, to the right) means the right side. The maxillary right first premolar is therefore 4+.
In the Haderup system, a zero placed in front of the tooth number indicates a primary tooth; for example, the primary mandibular left second molar is -05. Studies have shown that the permanent dentition appears to be evolving, so that the last molar (wisdom tooth) and the maxillary lateral incisor are gradually reducing in size or are completely absent in some individuals. When a complete replacement of the permanent dentition is carried out, the wisdom teeth are not replaced, which is why such dentures are often known as "28ers" and why the diagrams of the dental arches for prosthetic restorative treatment show only 28 teeth.