Most adults have eight premolars — two in each quadrant — that sit between the canine and molar teeth.
Ask someone how many teeth an adult has, and most will say 32. Ask them to name the types, and premolars usually get forgotten — lumped in with molars or vaguely assumed to be back teeth. The confusion makes sense. Premolars, also called bicuspids, transition from the tearing action of canines to the grinding action of molars, so they don’t always stick in memory the way incisors or wisdom teeth do.
But that fuzzy distinction skips over an important part of your oral anatomy. Most adults have exactly eight premolars: two in each of the four dental quadrants. Here’s how they fit into the permanent set, what they do, and why their root structure and groove patterns matter during a dental exam.
Eight Premolars: Two Per Quadrant
The short answer is eight. Divide the mouth into four sections — upper right, upper left, lower right, lower left — and each quadrant holds two premolars. Cleveland Clinic confirms that the permanent adult set of 32 teeth includes eight premolars alongside eight incisors, four canines, and 12 molars.
Premolars sit directly behind your canines. They are a permanent-teeth-only feature, meaning you won’t find them in a child’s primary (baby) dentition. The first premolar neighbors the canine, and the second premolar sits just behind it, directly before the first molar. They are often called bicuspids because most have two main cusps — a buccal and a palatal or lingual cusp — that give them their flat, grinding surface.
Knowing your premolars is helpful because they are common sites for cavities and are frequently evaluated during orthodontic treatment planning.
Why the Count Matters for Chewing and Oral Health
So why does the exact number of premolars matter for your day-to-day oral health? They handle a unique part of the chewing cycle that no other tooth type covers quite the same way. People care about tooth count for different reasons — chewing efficiency, orthodontic work, or general health — and premolars are the functional bridge in your mouth.
- Mechanical role: Premolars help tear, crush, and grind food into smaller pieces. They act as a functional bridge between canines and molars, transferring the workload during chewing.
- Size and shape: Premolars are larger and wider than canine teeth but significantly smaller than molars. While a molar has four cusps or points, a premolar has two to three cusps.
- Anatomical differences: Upper (maxillary) premolars are trapezoidal in shape. Lower (mandibular) premolars are rhomboidal. The upper first premolar usually has two roots; other premolars typically have a single root.
- Decay risk: Mayo Clinic notes that cavities most often occur in back teeth, including molars and premolars, due to their grooves and location. Limiting sugary snacks and beverages can help protect them from decay.
- Orthodontic considerations: First premolar extractions are common in orthodontics to create space for crowding. Studies highlight that this pattern can produce significant retraction of incisors and influence lip position.
Knowing the count and location of your premolars helps you speak the same language as your dentist. When they mention decay on tooth number four or thirteen, you’ll know exactly which tooth they mean — your upper left first premolar.
How Premolars Compare to Molars and Canines
The easiest way to confuse teeth is to assume all back teeth do the same job. Premolars and molars have different shapes, cusps, and root structures that reflect their specific roles. A quick comparison of the five tooth types shows where premolars fit.
| Tooth Type | Number | Cusps | Typical Root Complexity |
|---|---|---|---|
| Incisors | 8 | 1 | Single root |
| Canines | 4 | 1 | Single root, long |
| Premolars | 8 | 2-3 | 1-2 roots |
| Molars | 8-12 | 4 | 2-3 roots |
| Wisdom Teeth | 0-4 | 4 | Variable |
The table shows premolars are the only tooth type that bridges two distinct functions — tearing and grinding. Their root structure also varies more than most people realize. For example, a study available through the EPA, a premolar root canal study, found that 69.9% of upper first premolars had two canals, while most mandibular premolars had a single root. This variability matters for anyone preparing for root canal treatment, as a dentist needs to know how many canals a premolar has to ensure the procedure is thorough.
Steps to Keep Your Premolars Healthy
Because premolars sit further back in the mouth, they can be harder to clean than your front teeth. This makes them vulnerable to plaque buildup and decay concentrated in their grooves.
- Brush the back surfaces thoroughly. Tilt your toothbrush vertically to reach the premolars behind the canines. Gentle up-and-down strokes clear the grooves where food collects.
- Floss between them daily. Premolars touch each other and adjacent molars, creating tight spaces that trap food and bacteria. Flossing before brushing helps loosen debris.
- Limit sugary snacks and sips. The grooves in premolars are a prime location for cavities. Rinsing with water after sweets can help lower your decay risk.
- Watch for gum disease signs. Redness, swelling, or bleeding when flossing near the premolars can indicate gingivitis that needs professional attention.
- Attend regular dental check-ups. Dentists often catch early decay in premolars during cleanings. X-rays can pick up cavities between premolars before they become painful.
These five steps target the specific risks premolars face due to their position and shape. Consistency with daily hygiene makes a significant difference in preventing common issues like premolar cavities and gum disease.
What Makes Premolars Unique in Adult Dentition
Unlike incisors, which are usually simple in structure, or molars, which are large and complex, premolars follow a distinct developmental path. They are unique to the permanent dentition and are not present in the primary (baby) teeth set.
A case report hosted by the NIH examined unusual three-cusp patterns on premolars — the premolar development lobes paper is a useful reference for understanding how these teeth form. It is stated that maxillary premolars and the mandibular first premolar develop from four lobes (mesial, distal, buccal, and palatal), whereas a mandibular second premolar with two lingual cusps develops from five lobes. This lobe-based development explains the variation in cusp number across premolars.
Their position in the mouth means they bear significant chewing force without the broad base of a molar. This makes their root structure — single or dual — especially important for long-term stability.
| Feature | Premolars | Molars |
|---|---|---|
| Root count | 1-2 (upper first has 2) | 2-3 |
| Cusp count | 2-3 | 4 |
| Primary job | Tear & grind | Grind |
The Bottom Line
So when someone asks how many premolars an adult has, the answer is eight — two in each quadrant of the mouth. These bicuspid teeth sit behind your canines and ahead of your molars, and they play a key role in crushing and grinding food into smaller pieces during the chewing cycle.
If you are curious about your own premolar count or root structure, your dentist can point them out during your next cleaning and check the grooves for early signs of decay — the most common trouble spot for these hard-working teeth, which can often be managed with good oral hygiene and regular professional care.
References & Sources
- Epa. “Reference” In a study of root morphology, 69.9% of upper first premolars had two canals, and most mandibular premolars had a single root.
- NIH/PMC. “Pmc3583109” The maxillary premolars and mandibular first premolar develop from four lobes (mesial, distal, buccal, and palatal).