What Tooth Is Number 5 and Where Is It Located?

Tooth number 5 is the upper right first premolar, located just behind the canine (eye tooth) on the right side of your upper jaw. That number comes from the Universal Numbering System, which is the standard method used by dentists across the United States. If your dentist mentions “number 5” during an exam or on an insurance form, they are talking about a small but functionally important tooth that sits roughly at the corner where your smile transitions from the front teeth to the back chewing teeth.

Exactly Where Tooth Number 5 Sits in Your Mouth

The Universal Numbering System counts teeth starting from the upper right side of your mouth, working across to the upper left, then dropping down to the lower left and sweeping back to the lower right. Tooth #1 is your upper right third molar (wisdom tooth), and the count moves forward from there. By the time you reach #5, you have passed the third molar (#1), second molar (#2), first molar (#3), and second premolar (#4). Tooth #5, the first premolar, sits directly behind the upper right canine (#6).

If you run your tongue along the right side of your upper teeth starting from the front, you will first feel the central incisor, lateral incisor, and then the pointy canine. The next tooth back, the one with a broader biting surface and two small cusps on top, is #5. It is the first of the premolars, sometimes called bicuspids because of those two cusps. On the opposite side of your upper jaw, the mirror image of #5 is tooth #12, the upper left first premolar.

Why Your Dentist Might Call It Something Different

The Universal system is dominant in the United States, but it is not the only numbering scheme in the world. The FDI (Fédération Dentaire Internationale) system, also known as the ISO system, is the international standard used in most countries outside North America. Under the FDI system, the same tooth that Americans call #5 is labeled #14. A study comparing these numbering systems noted that the maxillary right first premolar is #5 in the Universal system, #14 in the FDI system, and #4 in the Palmer notation, which is still used in parts of the UK and some dental schools.¹

This numbering confusion can matter practically. If you move between countries or see specialists trained in different systems, “tooth 14” could mean your upper right first premolar (FDI) or your upper left first molar (Universal). When transferring dental records internationally, make sure the tooth name (upper right first premolar) is written out alongside the number, especially for surgical or orthodontic planning.

What the First Premolar Actually Does

Premolars are transitional teeth. They are not as sharp as canines and not as broad as molars. The first premolar has a flattish biting surface with two cusps, one facing toward your cheek and one facing toward your tongue. This shape makes it well suited for crushing and tearing food into smaller pieces before the molars grind them down. It handles the intermediate step between biting off a chunk and pulverizing it.

The upper first premolar typically has two roots, one pointing toward the cheek and one toward the palate, though single-rooted and three-rooted variations exist. This two-root anatomy sets it apart from the lower first premolar, which almost always has a single root. The dual roots anchor the tooth firmly but also make it relevant in certain clinical situations, particularly when the roots sit close to the maxillary sinus above.

Orthodontic Extractions and Why Premolars Are Often the First to Go

If you have ever had braces or been told you need teeth pulled before orthodontic treatment, there is a good chance the first premolars were the teeth in question. When there is significant crowding or the front teeth protrude too far forward, orthodontists need to create space somewhere in the arch. The first premolars are popular extraction candidates because removing them opens up room in a strategic location, close enough to the front teeth to allow effective retraction of the incisors, but far enough back that the gap can be closed without leaving an obvious cosmetic hole.

An orthodontic case report described the correction of a Class I malocclusion with severe crowding and bimaxillary protrusion using first premolar extractions specifically, noting that factors like bone discrepancy, jaw relationships, facial profile, and dental asymmetries all feed into whether first or second premolars are the better choice.² In practice, this decision is never automatic. Some patients do better with second premolar extractions, and in many cases, no extractions are needed at all. But when the plan calls for pulling teeth, the first premolar’s location and the fact that its loss causes minimal functional harm make it a frequent target.

The Maxillary Sinus Connection

One anatomical detail about tooth #5 that most people never think about is its relationship to the maxillary sinus, the air-filled cavity inside the cheekbone just above the upper teeth. The roots of upper premolars and molars can sit very close to the floor of this sinus, and how close matters for dental procedures like implants, root canals, and extractions.

A study of the distances between root tips and the sinus floor found that the gap was longest in the first premolar area compared to other posterior teeth, meaning #5 generally has a bit more bone buffer between its root tips and the sinus than, say, the second premolar or molars do.³ That same study also found, though, that the cortical bone plate forming the sinus floor is thinnest in the first premolar area. So while the root tips of #5 tend to sit farther from the sinus cavity, the bone between them is more delicate.

This anatomy becomes important if tooth #5 is lost and you want a dental implant placed immediately. Research on immediate extraction implant placement found that in about a quarter of first premolar sites, there was less than 3 mm of bone above the root apex to engage with an implant, raising the risk of perforating the sinus floor during surgery.⁴ For the second premolar, that percentage jumped to over 60%. The practical takeaway is that implant placement in this area requires careful three-dimensional imaging beforehand, and your surgeon may choose an implant with a wider diameter rather than a longer one to avoid pushing into the sinus.

How Tooth Number 5 Factors into Smile Appearance

When you smile broadly, how many teeth show? For most people, the visible zone extends from the canine area back to somewhere around the premolars. Whether your first premolar, second premolar, or even first molar shows during a natural smile affects how the smile is perceived. A study evaluating smile aesthetics in a Chinese cohort found that smiles displaying teeth back to the second premolar were rated as more attractive than smiles that showed teeth all the way to the first molar.⁵

Tooth #5, the first premolar, is right at the edge of this aesthetically sensitive zone. For people with narrow smiles, it may barely show. For people with wide or gummy smiles, it is fully on display. This is part of why cosmetic dentists pay attention to premolar appearance when planning veneers, whitening, or orthodontic finishing. If your #5 is discolored, rotated, or oddly shaped, it can affect the overall look of your smile more than you might expect from a “back” tooth.

Common Dental Problems at This Position

The first premolar is not inherently more prone to cavities or gum disease than its neighbors, but its position creates a couple of vulnerabilities. The contact point between the canine and the first premolar can be a tight spot where floss does not slide in easily, making it an area where plaque builds up and interproximal decay (cavities between teeth) can develop if hygiene slips. This is one of those spots your dentist is specifically checking on X-rays.

Premolars can also crack. Because they are smaller than molars but still used for significant chewing force, especially if you have a habit of chewing ice or hard candy, the cusps of a premolar can fracture. Vertical root fractures are another concern, particularly in teeth that have had root canal treatment and lost some structural integrity. Detecting these fractures on standard dental X-rays can be tricky, and sometimes a crack in tooth #5 goes undiagnosed until the symptoms become obvious.

Another scenario where tooth #5 comes up clinically is an impacted or malpositioned premolar. While impacted wisdom teeth get most of the attention, premolars can occasionally fail to erupt properly, especially when there is crowding in the developing dental arch. In children, a retained baby molar that does not fall out on schedule can block the first premolar from moving into its correct position.

Premolar Development and Forensic Age Estimation

First premolars develop and erupt on a predictable timeline, which makes them useful for more than just chewing. They typically begin forming in the jawbone around age two and erupt into the mouth somewhere between ages 10 and 12, replacing the first baby molar. Because tooth development follows biological age more reliably than height or skeletal growth in many cases, forensic scientists use premolar developmental stages as a tool for estimating the age of children and adolescents.

A study of Indian children evaluated the developmental stages of canines and first premolars using standardized staging criteria and found that these teeth provided useful data for forensic age estimation, while also highlighting that population-specific reference data is important because development timelines can vary between ethnic groups.⁶ This has real-world applications in legal proceedings, immigration cases, and disaster victim identification, where a panoramic dental X-ray showing the stage of premolar root formation can help establish whether someone is a child or an adult.

When a Dental Chart Says “Number 5” and You Are Not Sure What Happened

If you are reading your own dental chart or an insurance explanation of benefits and see a reference to tooth #5, here is how to decode what you are looking at. The tooth number tells you which tooth is involved. The procedure codes (often called CDT codes) next to it tell you what was done. Common procedures you might see attached to #5 include:

• D2740 or D2750: A crown, either porcelain or porcelain-fused-to-metal, placed on the tooth.
• D3320: Root canal treatment on a premolar, typically involving the two canals that correspond to the two roots.
• D7140 or D7210: Extraction, either simple or surgical.
• D2391 or D2392: A composite (tooth-colored) filling on one or more surfaces.

If the chart shows “missing” next to #5 and you are sure you have never had a tooth pulled there, it is worth asking about. Sometimes teeth are congenitally absent, meaning they never developed. Premolar agenesis, while less common than missing wisdom teeth or lateral incisors, does occur, and a person can go their whole life with a retained baby tooth in the spot where #5 should have erupted.

The Mirror Tooth and Lower Counterpart

In the Universal system, teeth are numbered so that the upper arch is 1 through 16 (right to left) and the lower arch is 17 through 32 (left to right). The tooth directly below #5 in your bite, the lower right first premolar, is #28. Meanwhile, the matching tooth on the upper left side is #12. These three teeth, #5, #12, and their lower counterparts #21 and #28, form a functional set. If one is extracted for orthodontic purposes, the others are often extracted too to keep the bite balanced.

The lower first premolar (#28) differs from #5 in some notable ways. It almost always has a single root instead of two, and its crown is smaller with less pronounced cusps. It also sits farther from the mandibular nerve canal than the lower molars do, which generally makes procedures on it less risky from a nerve-damage standpoint. If you ever need implants in this area, the considerations are quite different compared to the upper jaw, where the sinus proximity complicates things.

Premolars in the Animal Kingdom

Humans are not the only species with premolars, but the way ours look and function reflects millions of years of dietary adaptation. In many carnivores, the premolars are blade-like and designed for shearing meat. In herbivores, they tend to be broad and flat for grinding plant material. Human premolars sit somewhere in between, with a moderately flat surface that works for both crushing and some grinding, reflecting our omnivorous diet. The transition from a three-premolar arrangement (seen in many primates and earlier human ancestors) to our current two premolars per quadrant happened gradually over evolutionary time, and the teeth we lost were on the front end of the premolar row, not the back.

This evolutionary history explains why our premolars are sometimes called “bicuspids” in older dental terminology. The two-cusp design is a hallmark of teeth that serve a dual purpose, not fully specialized for slicing or for grinding, but capable of doing a reasonable job at both. Some dental schools still use “bicuspid” as the primary term, so if you see it on a dental chart or hear it from an older practitioner, it means the same thing as premolar.