How Are Premolar Teeth Different from Molars and Canines?
Premolars or bicuspids or premolar teeth are a type of teeth present between our molars and our canine teeth. Humans have two sets of premolars for every quadrant leading to 8 premolars in total in our mouth. These premolars have at least 2 cusps and are used for chewing food.
They contain properties of both canines (in the front) and molars (in the rear), and they help food transfer from the canines to the molars. The function of premolar teeth is to act as a transitional vessel for the food from the front to the back of our mouth for proper breakdown, thus earning it the name of “transitional” teeth.
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Structure of Premolars
The premolar teeth numbers are 8 in our mouth with 2 of each of the following -
Maxillary first premolar
Maxillary second premolar
Mandibular first premolar
Mandibular second premolar
The structure of these premolars all differ from each other. Let’s take a look at them.
Maxillary First Premolar
The crown is more ovoid, being wider than the rest.
At first, these first premolars look similar to their neighbor, the canines.
They generally contain two roots but can sometimes have just one.
Maxillary Second Premolar
Their shape and structure are similar to the first premolars but their distobuccal and mesial-buccal corners are more rounded.
Their cups are more equal and smaller in size.
They usually have one root.
They have smaller occlusal fissures.
Mandibular First Premolar
These premolars are the smallest out of the 4 premolars.
They have a very short lingual cusp with a broader buccal cusp. The lingual cusp is just half the size of the buccal cusp.
From the occlusal, only 2/3rd of the buccal surface of this premolar is visible.
They usually have one root with a round or oval cross-section.
Mandibular Second Premolar
Their crown is larger than even the mandibular first premolar.
They have a smaller better-developed lingual cusp with a broader buccal cusp.
The buccal and the lingual cusp is separated by an occlusal fissure which is both mesiodistal and well-defined.
They usually have one root with a round or oval cross-section.
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Taking Care of Premolar Teeth
The most common cause of premolar teeth pain is cavities. Due to their wide cusps, a lot of food gets stuck there leading to cavities. However, there is no extra special care to be taken of one’s premolars. Just like the rest of our teeth, premolars require thorough brushing twice daily with a good quality toothbrush. This will strengthen your tooth enamel. You can also use floss to clear out any plaque from your teeth.
Difference Between Premolar and Molar Teeth
There is very little difference between our molar and premolar teeth. But even that little difference is significant. Their main difference lies in their shape and size. Premolars might look wider and larger than your narrower canine teeth, but they are smaller than molars.
Again, while both molars and premolars contain fissures and pits in their cusps, the fissures are much deeper in the molars. This leads to a greater risk of cavities in your molars than in your premolars.
The molars and premolars also differ regarding the number of roots they have. Only the maxillary or the upper first premolar has two roots while the rest have a single root. On the other hand, the molars are always accompanied by roots except for the upper molars, which may also have three roots.
Premolars in Other Mammals
Premolars were found in primitive placental mammals. The premolar teeth numbers in them were 4 every quadrant but two of them, the medial ones (closest to the front of their mouth) have been lost already since apes and old world monkeys.
Fun Facts
Human premolars are known as Pm3 and Pm4 by paleontologists.
Our premolars are our most commonly removed teeth. Almost 48.8% of cases require the removal of premolars during orthodontic treatment.
FAQs on Premolar Teeth: Structure, Functions, and Key Facts
1. What are premolar teeth and where are they located in the dental arch?
Premolar teeth, also known as bicuspids, are permanent teeth located between the pointed canine teeth and the large molar teeth. An adult human has a total of eight premolars, with two situated in each quadrant of the mouth (upper left, upper right, lower left, lower right). They act as transitional teeth, bridging the gap between the tearing function of canines and the grinding function of molars.
2. What is the primary function of premolar teeth in digestion?
The primary function of premolar teeth is to crush and grind food into smaller, more manageable pieces before it is passed to the molars for final grinding. Their broad occlusal (biting) surface with multiple cusps is perfectly designed for this initial grinding process, which is a key step in the mechanical digestion of food, increasing the surface area for enzymes to act upon.
3. How do premolar teeth differ from molars in terms of structure and size?
Premolars and molars differ in several key aspects:
- Size: Premolars are generally smaller and less broad than molars.
- Cusps: Premolars typically have one or two cusps (hence the name bicuspid), whereas molars have four or more prominent cusps.
- Roots: Most premolars have a single root, except for the upper first premolars which often have two. In contrast, upper molars typically have three roots, and lower molars have two.
- Number: There are eight premolars in a full adult set of teeth, compared to twelve molars (including wisdom teeth).
4. At what age do permanent premolars typically erupt?
Permanent premolars are not present in the primary (baby) set of teeth. They begin to erupt by replacing the primary molars. The first premolars usually appear between the ages of 10 and 11, while the second premolars follow shortly after, typically erupting between the ages of 10 and 12.
5. Why are premolars often called 'bicuspids', and what is the significance of their cusps?
The term 'bicuspid' literally means 'two cusps'. This name is commonly used for premolars because many of them, particularly the lower ones, feature two prominent points or cusps on their biting surface. These cusps are crucial for their function; they interlock with the cusps of the opposing teeth to efficiently crush, shear, and grind food particles during chewing.
6. Since children don't have premolars, which teeth do the permanent premolars replace?
This is a common point of confusion. The permanent premolars do not replace any primary premolars because none exist. Instead, they erupt in the space occupied by the primary molars (also known as deciduous molars). When a child is around 10-12 years old, their eight primary molars fall out, and the eight permanent premolars grow in their place.
7. From a biological standpoint, why might premolars be removed for orthodontic treatment?
Premolars are sometimes strategically removed during orthodontic treatment to resolve issues of severe overcrowding. From a biological and functional perspective, they are often chosen for extraction because:
- Their removal creates significant space within the dental arch to allow other teeth to be aligned properly.
- They have a less critical role in aesthetics compared to front teeth and a less essential grinding role than the larger molars.
- Removing a premolar from each quadrant can help achieve a balanced and stable bite (occlusion) after the teeth are straightened.
8. What are the key features that distinguish a first premolar from a second premolar?
While both are premolars, the first and second premolars have distinct features. Generally, the first premolar is slightly larger and more angular, often resembling the canine next to it. The upper first premolar is unique as it frequently has two roots. The second premolar is typically smaller, with more rounded cusps that make it look more like a small molar. It almost always has a single root.
