Midline
Definition
The anatomical midpoint of the dental arch dividing it into left and right halves. In notation systems, position 1 is always the central incisor closest to the midline on each side.
- Location
- Anatomical midpoint of the dental arch
- Function
- Divides arch into left and right halves
- Notation convention
- Position 1 nearest midline on each side
- Field
- Forensic odontology
Common questions
Why does every tooth-numbering system need a fixed midline reference?+
Without a shared starting point, examiners recording or comparing dental charts from different sources could not be certain they were referring to the same tooth, so the midline anchors every counting or coding scheme to a common anatomical landmark.
Does the midline always align exactly with facial symmetry?+
Not necessarily; dental midline can shift from skeletal or facial midline due to crowding, missing teeth, or asymmetric jaw growth, which is itself sometimes a useful individualising feature in identification work.
Related terms
- FDI Notation
- The two-digit system published by the Federation Dentaire Internationale. The first digit (1-4 for permanent, 5-8 for deciduous) encodes the quadrant; the...
- Palmer Notation
- A grid-based system where a bracket symbol indicates the quadrant and a number 1-8 (or letter A-E for deciduous) indicates position from...
- Quadrant
- One of four sections of the dentition: upper right, upper left, lower left, lower right. The midline divides left from right; the...
- Universal Numbering System
- The North American standard. Permanent teeth are numbered 1-32 running clockwise from the maxillary right third molar. Deciduous teeth are lettered A-T...