Where Is Tooth Number 4 Located in Your Mouth?

Tooth number 4 is the upper right first premolar, sitting just behind the upper right canine (the “eye tooth”) and just in front of the upper right second premolar. In the Universal Numbering System used by dentists across the United States, the count starts at 1 with the upper right third molar (wisdom tooth) and moves forward along the arch, making the first premolar the fourth tooth from the back on that side. This small but hardworking tooth occupies a transitional zone in your mouth, bridging the tearing function of the canines and the grinding power of the molars, and it has some anatomical quirks that make it surprisingly interesting from a clinical standpoint.

How the Numbering Works

The Universal Numbering System assigns every permanent tooth a number from 1 to 32. It begins at the upper right third molar (tooth 1) and counts forward across the upper arch to the upper left third molar (tooth 16), then drops down to the lower left third molar (tooth 17) and sweeps back across the lower arch to the lower right third molar (tooth 32). Under this system, tooth 4 always refers to the maxillary (upper) right first premolar. If your dentist uses the FDI (Fédération Dentaire Internationale) system common in many other countries, that same tooth would be labeled 14, where the “1” refers to the upper right quadrant and the “4” to the first premolar position within it. Knowing which system your dentist uses avoids confusion, especially if you are reading dental records from another country.

The first premolars are also sometimes called “first bicuspids,” an older name that references the two cusps (pointed tips) on their biting surface. Your mouth has four first premolars in total: one in each quadrant. Tooth 4 is specifically the one in the upper right.

Exactly Where It Sits and What Surrounds It

To find tooth 4, slide your tongue along your upper right teeth starting from the front. You will pass the central incisor, the lateral incisor, and then the canine, which is the pointy tooth at the corner of your arch. The very next tooth behind the canine is tooth 4. It is flanked on one side by that canine (tooth 3) and on the other by the second premolar (tooth 5). Below it, when your jaws are closed, it meets the lower right first premolar (tooth 29 in the Universal system).

Because it is in the upper jaw, tooth 4’s roots point upward toward the floor of the maxillary sinus, the air-filled cavity inside your cheekbone. This proximity matters during dental procedures. A cone-beam CT study found that upper first premolars most often have a “spaced” relationship with the sinus floor, meaning there is a comfortable cushion of bone between the root tips and the sinus cavity. Actual root-tip penetration into the sinus was not observed for first premolars, making them safer neighbors to the sinus than the second premolars or molars further back.

1PubMed Central. Evaluation of the Proximity of the Maxillary Teeth Root Apices to the Maxillary Sinus Floor in Romanian Subjects: A Cone-Beam Computed Tomography Study

Studies measuring the actual distance report that the buccal (cheek-side) root of an upper first premolar sits roughly 5 to 8 mm from the sinus border, while the palatal (tongue-side) root sits about 4 to 7 mm away.

2Journal of Endodontics. Proximity of Premolar Roots to Maxillary Sinus: A Radiographic Survey Using Cone-beam Computed Tomography That gap is reassuring for routine fillings and crowns, though it becomes relevant if infection at the root tip spreads upward or if an implant is placed after the tooth is lost.

What Tooth 4 Looks Like

The crown of tooth 4, the part visible above the gumline, is smaller than a molar but broader than a canine. It typically has two cusps on its biting surface: a larger one facing the cheek and a smaller one facing the tongue. This two-cusp design is where the old name “bicuspid” comes from. The crown is somewhat flattened from cheek to tongue, giving it a shape that works well for crushing food rather than slicing or grinding it.

Unusual crown variations do exist. A documented case report described maxillary first premolars with three cusps rather than the usual two, a presentation the authors called the first of its kind in the literature.

3PubMed Central. Maxillary and mandibular first premolars showing three-cusp pattern: an unusual presentation Another rare anomaly is dens evaginatus, an extra bump of enamel on the biting surface. While this has been documented more frequently on second premolars, its occurrence anywhere on premolars can create problems if it wears down or fractures and exposes the nerve inside.

4PubMed Central. Multiple Talon Cusps and Dens Evaginatus in the Maxillary Dentition With Coexisting Single-Tooth Hypodontia: A Case Report

Root Anatomy and Why Dentists Care About It

Below the gumline, tooth 4 is one of the more anatomically unpredictable teeth. Upper first premolars are famous among dentists for their variable root structure. One imaging study of a Middle Eastern population found that about 90% of upper first premolars had two roots, roughly 8% had a single root, and just under 2% had three roots.

5The Open Dentistry Journal. Evaluation of Variations in Root Canal Anatomy and Morphology of Permanent Maxillary Premolars among the Emirate Population using CBCT Those proportions shift across ethnic populations, but the two-root form is consistently the most common.

Inside those roots, the canal system, the narrow passageways containing nerves and blood vessels, can be even more varied. A cone-beam CT study found that upper first premolars displayed a wide range of canal configurations, with the most common pattern involving two separate canals that run from top to bottom.

6PubMed Central. Root form and canal anatomy of maxillary first premolars: a cone-beam computed tomography study This variability is clinically significant because missed canals during a root canal procedure are one of the main reasons treatment fails.

7PubMed Central. Root canal treatment of a maxillary first premolar with three roots

If you ever need a root canal on tooth 4, your dentist or endodontist will likely take extra imaging beforehand precisely because of this unpredictability. A tooth that looks like a simple single-rooted premolar on a standard X-ray can turn out to harbor two or even three canals when viewed in three dimensions.

The Role of Tooth 4 in Chewing

Premolars are sometimes overlooked in favor of the big molars, but they carry a real share of the chewing load. Research has found that roughly 90% of chewing function occurs in the first molar and premolar region combined.

8PubMed. Chewing and occlusal function Tooth 4 and its neighbors are responsible for the initial crushing of food before it moves back to the molars for final grinding.

Interestingly, chewing on premolars produces a different jaw movement pattern than chewing on molars. When you chew on the first premolar area, the closing angle of the lower jaw is narrower, the path the jaw joint traces is shorter, and the speed of jaw movement is slower compared to molar chewing.

9PubMed. Influence of changing the chewing region on mandibular movement In practical terms, premolar chewing is a more controlled, less forceful motion. This makes sense given that these teeth are positioned closer to the front of the mouth, where the jaw has less mechanical leverage than it does further back near the molars.

Losing tooth 4 does not necessarily cripple your ability to chew, but it shifts the workload onto adjacent teeth and can change how the opposing lower premolar wears over time. This is one reason dentists prefer to restore or replace the tooth rather than leave the gap open.

When Tooth 4 Erupts

Tooth 4 is not one of the first permanent teeth to show up. The typical eruption sequence in the upper jaw places the first premolar fourth in line, after the first molar, the central incisor, and the lateral incisor. In boys, the recorded maxillary sequence is first molar, central incisor, lateral incisor, and then first premolar. Girls follow a similar pattern but with the first molar often beating the central incisor to the surface.

10PubMed Central. Changes in the Sequence of Eruption of Permanent Teeth; Correlation between Chronological and Dental Age and Effects of Body Mass Index of 5-15-year-old Schoolchildren

Most children get their upper first premolars somewhere between ages 10 and 12. This timing coincides with the shedding of the baby first molar that occupied that spot. Parents sometimes notice a gap after the baby tooth falls out and before the premolar fully comes in, which is normal. The eruption process can be delayed or accelerated by factors like body mass index, nutrition, and individual genetics, but wide deviations from the expected sequence are uncommon enough to warrant a check by a dentist if they occur.

Why Tooth 4 Is Often the One Pulled for Braces

If you have ever had orthodontic treatment or know someone who has, there is a good chance upper first premolars were the teeth that were extracted to make room. Orthodontists frequently choose first premolars for extraction because they sit in a strategically useful position: removing them creates space right where the crowding tends to be worst, between the canines and molars, without sacrificing the canine’s important role in guiding your bite or the molar’s heavy grinding function.

The decision to extract first premolars versus second premolars depends on several patient-specific factors, including how severe the crowding is, what the facial profile looks like from the side, how much anchorage the orthodontist needs, and whether the wisdom teeth are likely to cause problems later.

11PubMed Central. Choosing the Right Extraction Pattern: First Premolars vs. Second Premolars In cases of significant crowding or a protruding upper jaw, the first premolar is often the better choice because it allows the front teeth to be pulled back further. When crowding is milder, extracting the second premolar instead can preserve a more natural arch shape.

Orthodontic extraction of premolars is a very common procedure. A study tracking 100 patients who had premolars removed for orthodontic purposes found an average of about two to three premolars extracted per patient, with over 70% of the teeth having fully developed roots at the time of removal.

12PubMed Central. Incidence of Risk and Complications Associated with Orthodontic Therapeutic Extraction Complications from these extractions are generally rare, though root shape and surrounding bone density can occasionally make the procedure trickier than expected.

Restoring Tooth 4 After Damage

Because it sits in the premolar zone that handles so much chewing force, tooth 4 is susceptible to fractures and wear, particularly if it has large fillings that weaken the remaining tooth structure. The good news is that modern restorative materials hold up well. A lab study testing different composite (tooth-colored) filling materials on upper premolars found that restored teeth could withstand forces well over 900 newtons, with some materials reaching above 1,100 newtons before fracture. For context, normal chewing forces in the premolar area are considerably lower than that. Teeth that were prepared (drilled) but left without any filling fractured at dramatically lower forces, in the range of 380 to 630 newtons, underscoring how much a well-placed restoration reinforces a weakened tooth.

13Journal of Oral & Dental Health. Evaluation of Fracture Resistance in Maxillary Premolar Teeth Restored with Different Direct Composite Restorative Material

For tooth 4 specifically, the dual-root anatomy and sometimes thin walls between the canals can make root canal treatment technically demanding. A case report of a three-rooted maxillary first premolar highlighted how undetected extra roots and canals are a major cause of failed root canal therapy.

7PubMed Central. Root canal treatment of a maxillary first premolar with three roots If your dentist suspects unusual anatomy, they may refer you to an endodontist (root canal specialist) who has access to surgical microscopes and advanced imaging.

Tooth 4 and Your Smile

How much of tooth 4 is visible when you smile depends on the width of your smile and the shape of your dental arch. In a narrow smile, only the front six teeth (canine to canine) show, and tooth 4 stays hidden. In a broader smile, the premolars become visible and contribute to how full and balanced the smile looks. Research on smile aesthetics in a Chinese population found that smiles displaying teeth back through the second premolar (tooth 5, one behind tooth 4) were rated as the most attractive among the groups compared.

14Elsevier / International Dental Journal. The Influence of the Maxillary Posterior Region on Smile Aesthetics in a Chinese Cohort

This finding suggests that tooth 4 lives right at the aesthetic boundary. A smile wide enough to reveal it looks more complete than one that stops at the canines, but the sweet spot seems to extend one tooth further, to the second premolar. Cosmetic dentists pay attention to this when designing veneers or planning orthodontic alignment: ensuring tooth 4 is well-shaped and properly aligned contributes to a broader, more appealing smile even if it is not the star of the show.

For people who have had tooth 4 extracted for orthodontic reasons, the canine is typically moved back to close the gap, and the result, when well-managed, is usually undetectable to casual observers. The canine may be reshaped slightly to mimic the first premolar’s profile. The aesthetic concern, then, is less about having or missing tooth 4 and more about whether the teeth that remain are well-aligned and proportionate.

When Tooth 4 Causes Unexpected Problems

A few clinical scenarios make tooth 4 surprisingly troublesome. One is a cracked tooth that has not yet fully separated. Because the upper first premolar tends to have two roots that splay apart with a relatively thin bridge of tooth structure between them, it is prone to a characteristic vertical fracture running from the biting surface down between the roots. Patients often describe intermittent sharp pain when biting, especially on hard or chewy foods. This fracture can be invisible on standard X-rays and difficult to diagnose until it progresses far enough to become obvious.

Another scenario involves referred pain. Because tooth 4’s roots sit near the floor of the maxillary sinus, infection at the root tip can sometimes mimic sinus symptoms, or conversely, a sinus infection can produce what feels like a toothache in the premolar area. Dentists and ENT doctors both encounter patients who are being treated for the wrong condition because the pain was attributed to the sinus rather than the tooth, or vice versa. If you have a lingering ache in the upper cheek area that does not respond to either antibiotics or dental treatment alone, it is worth asking your provider to consider the other possibility.

The proximity to the infraorbital nerve, which exits the skull just above the premolar region, can also occasionally cause numbness or tingling in the cheek and upper lip after dental procedures on tooth 4. This is almost always temporary, resolving within hours or days as the local anesthetic wears off or minor nerve irritation settles down, but it can be alarming if your dentist has not warned you about it beforehand.