Skip to content
✦ Odonto Fácilby dra_iswmi

Language

EspañolEnglish
Dental AnatomyBasic

Upper or lower? How to identify a tooth

To tell whether a tooth is upper or lower, look at the roots and the size of the crown: upper molars usually have 3 roots and lower ones, 2.
A skull with the bone cut away to show the upper and lower roots: the number and shape of the roots help you tell which arch each tooth is from.
A skull with the bone cut away to show the upper and lower roots: the number and shape of the roots help you tell which arch each tooth is from.Photo: Grey Geezer · CC BY-SA 4.0, Wikimedia Commons

What you need to know

  • Upper molars: almost always have 3 roots: mesiobuccal, distobuccal and palatal.
  • Lower molars: almost always have 2 roots, one mesial and one distal. In some people a third root appears on the lingual side (radix entomolaris).
  • Upper first premolar: the premolar that most often has 2 roots (buccal and palatal). In CT studies, about a third of them do.
  • Lower premolars: almost always have just 1 root.
  • Incisors: the upper central is the widest incisor in the mouth (≈8.5 mm according to textbooks); the lower incisors are much narrower.
  • The palatal root only exists in upper teeth: if you see it, it's an upper tooth.
  • There's always variation between people: that's why it's confirmed with a radiograph.

Most common number of roots

ToothUpperLower
Incisors11
Canine11
First premolar1 or 21
Second premolar11
Molars32

Terms in plain words

Palatal rootA root that faces the palate. Only upper teeth have it.
Facial (labial or buccal)The surface that faces the lips or the cheeks.
Radix entomolarisAn extra third root, located lingually and distally, in some lower molars.

For the exam

You're given a molar with 3 roots, and one of them points toward the palate. Is it upper or lower?

Show answerHide answer

Upper: the palatal root only exists in upper teeth.

Sources

  1. Pan JYY, et al. Root canal morphology of permanent teeth in a Malaysian subpopulation using cone-beam computed tomography. BMC Oral Health. 2019;19:14. View source
  2. Nelson SJ. Wheeler's Dental Anatomy, Physiology and Occlusion. 11th ed. Elsevier (textbook).
  3. Comparative Measurement of Mesiodistal Width of Six Anterior Maxillary and Mandibular Teeth in Rajasthan Population. View source
Practice this topic →

More from Dental Anatomy

FDI
Dental AnatomyBasic

FDI notation: how teeth are numbered

Each tooth is named with 2 digits: the first tells you the quadrant and the second, the position counting from the midline.
Eruption
Dental AnatomyBasic

Eruption chronology: when each tooth comes in

The first baby tooth comes in at around 6 months; at age 3 there are 20 primary teeth, and by around age 21 all 32 permanent teeth have come in.
Successors
Dental AnatomyBasic

Successional and non-successional teeth

The permanent molars don't replace any baby tooth: that's why they're called non-successional, and there are 12 of them.

← SuccessorsCarabelli →