Maxillary teeth are the teeth anchored in the maxilla, the bone that forms the upper jaw. Adults have sixteen of them in a full set: four incisors, two canines, four premolars, and six molars, arranged in an arch from the midline back to the wisdom teeth. Each type has a distinct shape tuned to a specific job, from slicing food to grinding it, and the upper jaw’s anatomy introduces quirks you won’t find in the lower jaw, including a close relationship with the sinus cavities overhead and a palate that can actually be widened during growth.
The Four Types of Maxillary Teeth
Your upper teeth break down into four categories, each with a recognizable shape and a clear role in the dental arch.
- Incisors: The four front teeth, split into two central and two lateral incisors. They are flat, chisel-shaped, and single-rooted. Their primary job is cutting and shearing food. They also support the upper lip and play a role in speech.
- Canines: One on each side, flanking the lateral incisors. These are the most robust single-rooted teeth in the mouth, with a pointed cusp and a root that is typically the longest of any tooth. They are designed for gripping and tearing.
- Premolars: Four in total, two on each side behind the canines. Also called bicuspids because they usually have two cusps. Premolars serve as a transition between the tearing function of canines and the grinding power of molars.
- Molars: Six in total (including the third molars, or wisdom teeth), with broad, multi-cusped crowns and multiple roots. They handle the heavy work of crushing and grinding food.
Children have a simpler version of this lineup. The primary (baby) dentition in the upper jaw includes eight incisors, four canines (which erupt as the same pointed teeth), and eight molars, but no premolars. The premolars replace the primary molars when the permanent teeth come in.
How Maxillary Incisors Shape Your Smile and Speech
The upper incisors do more than bite into an apple. They are the most visible teeth when you smile, and their size, shape, and alignment have an outsized effect on facial aesthetics. Research on smile attractiveness has identified several measurable components, including the arc formed by the incisal edges of the upper front teeth and how it aligns with the curvature of the lower lip, the amount of gum tissue visible above the central incisors, and the ratio of visible tooth width to overall smile width.
Maxillary lateral incisors show considerable variation in shape from person to person. Some are broad and well-formed, while others are unusually small or peg-shaped, a trait that has clinical consequences beyond appearance. Research on orthodontic patients has noted that these shape variations can affect both aesthetics and the way upper and lower teeth mesh together during function.1PubMed Central. Morphological Diversity of Permanent Maxillary Lateral Incisors and Their Impact on Aesthetics and Function in Orthodontically Treated Patients Incisors also matter for speech. Several sounds in English and other languages depend on the tongue contacting or approaching the back of the upper front teeth or the ridge just behind them. Losing primary upper front teeth early in childhood can cause speech distortion, particularly with sounds like “s,” “z,” “f,” and “v.”2PubMed. Premature loss of primary anterior teeth and its consequences to primary dental arch and speech pattern
Why Upper Canines Are Structurally Unique
The maxillary canines deserve special attention because they sit at a mechanical crossroads in the dental arch. They mark the corner where the front teeth transition into the side teeth, and their anatomy reflects that pivotal role. The root of an upper canine is the longest of any tooth, anchored deep in the jawbone and sitting just below the floor of the nasal passage. That long root gives the canine exceptional stability under load.3British Dental Journal. Canine guidance on crowned teeth: time for a rethink?
This stability matters because the canines often act as the primary guide when your jaw slides side to side. In what dentists call “canine guidance,” the upper and lower canines are the main teeth in contact during lateral movements, and the back teeth separate slightly. Research shows that this arrangement can reduce tension in the chewing muscles compared to distributing the side-to-side contact across several teeth.4PubMed Central. Electromyographic activity of the masseter muscle in individuals with group function and canine guidance The canine essentially acts as a steering tooth, limiting friction and wear on the rest of the dentition.5PubMed Central. Canine Rise Method: A Conservative Approach for Worn Teeth Rehabilitation with Different Adhesive Restorative Materials
That said, the long root that makes a canine so stable also creates challenges. If the tooth needs a root canal filling, the length of the canal can make the procedure harder to complete thoroughly. And if a post is placed inside the root afterward, it may only reach partway down, potentially acting as a lever that increases fracture risk.3British Dental Journal. Canine guidance on crowned teeth: time for a rethink?
The Surprising Complexity of Premolar Roots
Premolars look straightforward from the outside, with two cusps on top and a modest crown, but beneath the gumline they can be surprisingly complicated. The maxillary first premolar, in particular, is one of the most variable teeth in the mouth when it comes to root anatomy. A literature review found that roughly 42% of maxillary first premolars have a single root, while about 57% have two roots, and a small fraction have three.6PubMed. Root and Root Canal Morphology of Maxillary First Premolars: A Literature Review and Clinical Considerations Those proportions shift by population and even by sex. A study in a Japanese population found that about 65% of maxillary first premolars were single-rooted, with women more likely to have single roots than men.7Journal of Dental Sciences. Evaluation of root and root canal morphology in maxillary premolar teeth
Regardless of how many roots you see on an X-ray, the vast majority of maxillary first premolars have two root canals inside. About two-thirds of the time, those canals start separate and stay separate from top to bottom.6PubMed. Root and Root Canal Morphology of Maxillary First Premolars: A Literature Review and Clinical Considerations Many also contain lateral canals, branching tunnels, and other internal quirks that can make root canal treatment challenging if the clinician is expecting a simple anatomy.8PubMed Central. Root form and canal anatomy of maxillary first premolars: a cone-beam computed tomography study The second premolar, by contrast, is almost always single-rooted, with a single canal in about seven out of ten cases, though two-canal configurations become more common with age.7Journal of Dental Sciences. Evaluation of root and root canal morphology in maxillary premolar teeth
Upper Molars and the Cusp of Carabelli
The maxillary first molar is the largest tooth in the upper arch, typically carrying four or five cusps and three separate roots, a buccal pair (one toward the cheek, one toward the midline) and a single palatal root on the tongue side. Those three roots splay outward in a tripod arrangement that helps the tooth absorb heavy vertical and lateral chewing forces. The maxillary first molar erupts around age six, making it the first permanent tooth most children get in the upper jaw, and it bears a disproportionate share of the chewing workload over a lifetime.
One distinctive feature of the upper first molar is the cusp of Carabelli, a small extra bump on the palatal surface of the main inner cusp. It does not contribute to chewing, but it shows up frequently enough to be considered a normal anatomical variant rather than an anomaly. Studies have found this trait on roughly 53% of permanent maxillary first molars, with an even higher prevalence on primary second molars, around 68%.9Dentistry: Advanced Research. Cusp of Carabelli: Observations of an Odontogenic Trait Its size ranges from a faint groove to a fully formed fifth cusp, and its frequency varies among ethnic groups, making it useful in population studies and forensic identification.
When Maxillary Teeth Erupt
The permanent maxillary teeth don’t all arrive at once. They follow a predictable sequence, though the exact age varies by a year or two from child to child. In the upper jaw, the first molar leads the way, typically appearing around age six. The central incisors come next, followed by the lateral incisors, then the first premolar. After that, the canine emerges, then the second premolar, and finally the second molar. This sequence is different from the lower jaw, where the canine tends to erupt before either premolar rather than between them.10PubMed Central. Chronology and Sequence of Permanent Tooth Eruption in a Multi-Ethnic Urban Population
In both boys and girls, the maxillary second molars are the last permanent teeth to erupt, typically in the early teen years. Third molars, if they develop at all, come much later, generally between ages 17 and 25, and they frequently lack the space to emerge properly. A common issue with the eruption sequence is the maxillary canine, which sometimes fails to come in on its own because it has the longest path to travel from its development site high up in the jaw to its final position in the arch. When a canine gets stuck, or “impacted,” the consequences extend beyond that one tooth; treatment usually requires orthodontic intervention and sometimes minor surgery to guide it into place.
Canine Impaction and the Lateral Incisor Connection
Impacted upper canines are among the most common dental eruption problems, and researchers have been investigating why they happen. One well-supported theory points to the maxillary lateral incisor as a guiding influence: the canine appears to use the root of the neighboring lateral incisor as a kind of physical signpost during its descent into the arch. When that lateral incisor is missing or abnormally small (peg-shaped), the canine may lose its way and become impacted.
Studies bear this out. In one investigation, patients with impacted canines had significantly more peg-shaped lateral incisors, about 15.5% of the impacted group compared to just 3.1% in controls. When a peg-shaped lateral incisor was present, the probability of being in the impacted-canine group was over 80%.11PubMed Central. Association between maxillary canine impaction and other dental anomalies A separate study found a similar pattern: among patients with impacted canines, 21 had anomalous lateral incisors, compared to only three in the control group.12Dental Press Journal of Orthodontics. Relation between agenesis and shape anomaly of maxillary lateral incisors and canine impaction This relationship is one reason dentists monitor the development of lateral incisors carefully in children, as their shape can serve as an early warning sign for canine problems.
The Nerve and Blood Supply of Upper Teeth
The maxillary teeth receive their nerve signals and blood supply from a network that is more complex than older textbooks suggest. The traditional description lists the three superior alveolar nerves (anterior, middle, and posterior) running through bony canals in the wall of the maxillary sinus, branching downward to reach each tooth. Imaging studies using high-resolution CT combined with microscopic examination have confirmed that these canals contain both nerves and blood vessels, but the nerve network turns out to run more horizontally than the vertical layout typically shown in diagrams.13PubMed. The Relationships of the Maxillary Sinus With the Superior Alveolar Nerves and Vessels as Demonstrated by Cone-Beam CT Combined With μ-CT and Histological Analyses
More recently, research has shown that the palatal side of the upper teeth gets its own dedicated supply as well. Branches of the greater palatine nerve and artery, along with the nasopalatine nerve and sphenopalatine artery, reach the teeth, the surrounding bone, and the periodontal tissue through small openings on the palatal side of the jaw.14PubMed. The greater palatine nerve and artery both supply the maxillary teeth This dual supply matters in practice. Dentists sometimes find that a standard injection to numb the cheek-side nerves doesn’t fully anesthetize an upper tooth, and the palatal contribution is a likely reason. Supplemental palatal injections can make the difference between a comfortable procedure and a painful one.
How Upper Teeth Can Cause Sinus Problems
One of the more surprising features of the upper jaw is how close the roots of the back teeth sit to the floor of the maxillary sinus, the air-filled cavity inside the cheekbone. In some people, the roots of the premolars and molars actually poke through the sinus floor, separated from the sinus lining by only a paper-thin layer of bone or no bone at all. This proximity means that infections originating in these teeth can spread upward into the sinus.
Odontogenic sinusitis, or sinus infection caused by a dental source, is more common than many people realize. A study using cone-beam CT scans to evaluate maxillary sinusitis found that the first and second molars were about eleven times more likely to be involved than premolars. The palatal root of the first molar was the most frequently implicated root, followed by the mesiobuccal root of the second molar.15PubMed. Cone-beam computed tomography evaluation of maxillary sinusitis If you have chronic sinus symptoms on one side of your face, especially if they are accompanied by upper back tooth pain or a history of dental work, a dental origin is worth investigating. Treatment for odontogenic sinusitis usually needs to address the tooth problem first, because antibiotics and sinus rinses alone won’t resolve the infection if a diseased root keeps seeding bacteria into the sinus.
Bone Density Differences Between the Upper and Lower Jaw
The maxilla and the mandible are built differently. The lower jaw tends to be denser and more compact, especially in the back sections where molars sit. The upper jaw, by contrast, has a larger proportion of spongy trabecular bone, particularly in the areas above the premolars and molars where the maxillary sinus hollows out the interior. Research measuring trabecular bone density has confirmed that the lower jaw shows significantly greater density than the upper jaw at most tooth positions.16Implant Dentistry. Distribution of Trabecular Bone Density in the Maxilla and Mandible
This difference becomes particularly relevant when dental implants are placed. Implant stability depends heavily on the density and volume of bone available to grip the implant’s threaded surface. Analyses of implant stability have found that maxillary implants tend to show lower initial stability values than mandibular implants, likely because of the less dense bone they are anchored in.17The Saudi Dental Journal. Do dental implants installed in different types of bone (I, II, III, IV) have different success rates? To compensate, surgeons may choose wider or longer implants, use bone-grafting techniques, or allow a longer healing period before loading the implant with a crown. Success rates for maxillary implants are still high overall, but the softer bone does demand more careful planning.
Palatal Expansion and the Midpalatal Suture
Unlike the mandible, which is a single fused bone by early childhood, the maxilla consists of two halves joined at the midline by the midpalatal suture. In children and young adolescents, this suture is still open, which means the palate can be physically widened using an orthodontic device called a rapid maxillary expander. This treatment corrects a narrow upper jaw, creates space for crowded teeth, and can improve breathing by widening the nasal passages.
The window for this procedure depends on when the suture fuses. Maturation varies considerably from person to person. Some female patients show early fusion of the suture by age eleven, while some males begin fusing around fourteen, but the range is wide.18PubMed Central. Midpalatal Suture Maturation Stage in 10- to 25-Year-Olds Using Cone-Beam Computed Tomography Once the suture has fully fused, a standard palatal expander will no longer split the bone apart; at that point, surgical assistance is needed to separate the halves before expansion can work.19PubMed Central. Prediction of rapid maxillary expansion by assessing the maturation of the midpalatal suture on cone beam CT Because age alone is an unreliable predictor of suture status, CT imaging is increasingly used to check the degree of fusion before committing to a treatment plan, especially in teenagers and young adults where the outcome is uncertain.
Forensic Identification Through the Upper Jaw
The maxilla holds features that are useful long after the teeth have finished their biological work. On the roof of the mouth, a series of ridges called palatal rugae form a pattern as early as the third month of fetal development and persist for life. These ridges are unique to each individual, including identical twins, and are relatively well shielded from external damage by the surrounding lips, teeth, cheek fat pads, and bone. Because they resist decomposition and even incineration better than many other soft tissues, palatal rugae have been studied as an identification method comparable to fingerprints.20Austin Journal of Forensic Science and Criminology. Forensic Dentistry as a Tool for Identification
Beyond rugae, the maxillary teeth themselves carry identification value through dental records, which match the shape, restorations, missing teeth, and root anatomy visible on X-rays. Features like the cusp of Carabelli mentioned earlier, the number of premolar roots, and any prosthetic work all contribute to a dental profile that is extremely difficult to duplicate. In mass-disaster scenarios where DNA analysis may be slow or degraded, comparing postmortem dental findings against antemortem records remains one of the fastest and most reliable ways to identify individuals. The upper jaw’s combination of durable bone, distinctive tooth anatomy, and unique soft-tissue patterning makes it one of the most information-dense areas of the human skeleton for forensic purposes.
How the Mammalian Upper Jaw Evolved
The bone that holds your maxillary teeth has an evolutionary backstory that is stranger than it looks. In most vertebrates, the very front of the upper jaw is formed by a separate bone called the premaxilla, which holds the incisors. In humans and other placental mammals, the premaxilla appears to be fused seamlessly with the maxilla, and for a long time it was assumed that this was simply a case of two ancestral bones merging. Developmental studies comparing embryos from mice, bats, goats, and cattle found that what we call the premaxilla actually has two distinct developmental origins, but the part that corresponds to the “true” premaxilla of reptiles and amphibians was entirely lost during therian mammal evolution. What looks like a fused premaxilla in your upper jaw actually corresponds to a different ancestral bone, one related to the vomer found in the palates of non-mammalian vertebrates.21PubMed. Evolution of the therian face through complete loss of the premaxilla This rearrangement is part of what gave mammals their distinctive flat face and flexible upper lip, features that reptiles and amphibians lack. The maxillary teeth you use every day sit in a jaw whose architecture is, from an evolutionary standpoint, a novelty that made the mammalian face possible.