Wisdom tooth: which number, where it is located, and how many there are

The eighth tooth, third molar, "wisdom tooth" — these all refer to the same tooth, which erupts later than the others or does not appear at all. Below are brief answers about numbering, location, and the number of such teeth, without promises and without scare tactics.

Wisdom tooth — which number it is and how it is designated

In the dental arch it is the eighth: before it come the central and lateral incisors, the canine, two premolars, and two molars. Hence the colloquial "figure eight," and in dentistry, the "third molar." An adult usually has four such teeth: one on the right and one on the left of the upper and lower jaw.

In the two-digit international system, the first digit indicates the quadrant and the second the tooth number. The upper right wisdom tooth is recorded as 18, the upper left as 28, the lower left as 38, and the lower right as 48. Numbers 38 and 48 refer to the lower wisdom teeth; during their eruption, while only the edge of the tooth is visible, inflammation in the gingival pocket — pericoronitis — often occurs.

Where the upper and lower wisdom teeth are located

Both teeth are the farthest back in the arch, immediately behind the second molars. The upper ones are located in the posterior part of the upper jaw; they often erupt toward the cheek and injure the mucosa. The lower ones are located in the posterior part of the lower jaw and often tilt toward the adjacent second molar.

Because of the tilt, a gap remains between the second and third molars where food gets trapped. This area is difficult to clean with a brush, so plaque and tartar accumulate there more often, and caries of the adjacent tooth, gingivitis, or pericoronitis develops.

How many wisdom teeth there are and why they may be absent

Usually there are four — a pair on each jaw. Less commonly, additional fourth molars occur. There may also be fewer: the tooth germ does not form at all, and then it is called primary agenesis of the third molar. The absence of wisdom teeth is considered a variant of the norm, not a pathology. The third molar is regarded as a rudimentary organ, and the increasing frequency of its absence is linked to changes in diet — a decrease in the proportion of hard food.

The tooth may form but not emerge into the mouth: this condition is called impacted. If it has partially appeared, it is called a partially impacted tooth. In that case, a gingival "hood" forms over it, under which food debris is retained.

Why the wisdom tooth is so called

It is a late tooth: it erupts at 17–25 years of age, sometimes later, rarely earlier, and sometimes it does not erupt at all. The name reflects the age: the figure eight appears when a person's mental development is considered already complete. This tooth has no special properties — it is an ordinary molar, simply the last in the arch.

Structure: roots, germs, and the tooth under the gum

In structure, the figure eight does not differ from other teeth: enamel on the outside, dentin beneath it, the root covered with cementum, and pulp with nerves and vessels in the center. The difference is usually in shape: the shape of the crown and roots often differs from the usual.

The germs of all teeth, including wisdom teeth, form in the womb. Until eruption, the tooth remains under the gum and bone, and its position can be assessed on an image, such as a panoramic one: the doctor looks at the tilt, how much the tooth is covered by the gum, and what is happening with the adjacent molar.

When to see a dentist

If the tooth has erupted normally and does not cause concern, it is usually left in place and monitored at routine check-ups. Reasons to come earlier: pain and swelling in the posterior part of the jaw, an unpleasant taste in the mouth, fever, food trapping between the second and third molars. The doctor will ask about complaints, examine the oral cavity, and, if necessary, refer for an X-ray.

Problems described with difficult eruption:

• pain and swelling in the area of the tooth;
• pericoronitis — inflammation of the gum over a partially erupted tooth;
• food trapping and caries of the adjacent tooth;
• gum disease and tartar;
• fluid accumulation around the tooth (cyst) and abscess.

See a dentist urgently if bleeding does not stop, pain and swelling increase, or high fever or general malaise appears.

If episodes recur, the option of removal is discussed with the doctor: much depends on the position of the tooth, the condition of the surrounding tissues, and the complaints. After removal, if it comes to that, pain and swelling usually begin to subside within one to two days, and people most often return to normal activities the next day.

Eruption of a wisdom tooth is not in itself a reason to call an ambulance; 103/112 — for a life-threatening condition (for example, severe deterioration of well-being).

This material is for reference: it does not replace a dentist's consultation, and the decision on observation or removal is made together with the doctor.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer