Types of Human Teeth with their functions | Incisors to Molars

On the basis of functions human teeth are classified into 4 types. These are Incisors, Canines, Premolar and Molars. Teeth are the white hard substances pres

FORENSIC SCIENCEFORENSIC ODONTOLOGY

Shubham Kumar

1/29/20248 min read

Humans encompasses multiple types of teeth, each type of teeth, possess a unique function. Moreover, teeth are the basic engine of our survival vehicle, without, teeth we can't go far. Therefore, we should understand the types and functioning of our teeth, so that we can take care of them according to their needs.

In this article we are going to get a valuable insight about the type of teeth a human possess. Moreover, we will uncover the functions and unique abilities of the same.

Human Teeth

Teeth are the white hard substances present in the human mouth, essential for human survival and accessing the food. Unlike, amphibians, Human lacks the potential to swallow the food. Therefore, teeth are very essential for the breakdown of the food when we eat it. The set of teeth in human is called as dentine. There are two different sets of teeth found in humans. Permanent Dentine, also known as adult teeth, contains 32 pairs, whereas Temporary dentine, also known as deciduous or baby teeth, contain 20 pairs. Both the dentine possesses similar types of teeth, which are Incisors, Canine, Premolars and Molars. However, Temporary dentine doesn't possess premolars.

The permanent Dentine encompasses 32 pairs set of teeth- 8 incisors, 4 canines, 8 pre-molars and 12 molars.

The temporary dentine encompasses 20 pairs set of teeth- 8 incisors, 4 canines, 8 molars.

Types of Teeth

On the basis of functions human teeth are classified into 4 types. These are Incisors, Canines, Premolar and Molars.

Incisors

Incisors are the teeth used for cutting. There are 8 incisors in both the primary and permanent dentine: 4 maxillary and 4 mandibular. Both the maxilla and mandible have 2 frontal incisors called central incisors and 2 more incisors along the sides of central incisors called lateral incisors. Incisors have a slightly constrained neck and a single root.

Temporary Dentine has 8 incisors. Four on maxilla and four on mandible. Permanent Dentine has 8 incisors. Four on maxilla and four on mandible.

Anatomy of Incisors
  • Incisors are a group of four front teeth located in both the upper (maxillary) and lower (mandibular) dental arches. In each arch, there are two central incisors and two lateral incisors, making a total of eight incisors in the entire dentition. They are positioned at the front of the mouth, flanking the midline, and are the first teeth to be seen when a person smiles.

  • The shape of incisors is unique and easy to identify. They have a flat, chisel-like appearance with sharp cutting edges that facilitate their primary function of cutting and shearing food during the initial stages of chewing. The incisors' crown is typically wider mesiodistally (from front to back) than it is from labial to lingual (from the front surface to the back surface).

Function of Incisors
  • Biting and Cutting: Incisors are the first teeth to come into contact with food during the biting process. Their sharp edges allow them to cut and incise food into smaller, manageable pieces, making it easier for the posterior teeth (premolars and molars) to further break down the food during chewing and grinding.

  • Speech Articulation: Incisors also play a crucial role in speech articulation. Specifically, the upper incisors are essential for pronouncing certain speech sounds, such as "f," "v," "s," and "z." These sounds are known as labiodental and lingual-alveolar consonants, and their proper production relies on the precise placement of the tongue against the upper incisors.

  • Aesthetic Appeal: Incisors significantly contribute to a person's smile and facial appearance. They are highly visible when a person smiles, and their alignment and condition can greatly impact the aesthetics of the smile.

Note:

Incisor teeth, especially in the upper jaw, can easily get injured in accidents because they’re not well-protected and because of their size and shape. These kinds of injuries happen a lot to kids; at least 1 in 10 children get affected. When these accidents happen, they can cause big problems for the way their teeth work, how they look, how they feel about going to the dentist, and their overall quality of life. This affects not just the kids but also the people taking care of them.

Canines

Canines are sharp teeth specialized for cutting and tearing flesh. They are placed next to the lateral incisors in both the maxilla and mandible jaw. Moreover, they have a sharp edge and a thin neck, a prime reason for their deep penetration and hard tearing of food and flesh we eat.

Permanent Dentine has 4 canines. Four on maxilla and four on mandible. Temporary Dentine has 4 canines. two on maxilla and two on mandible.

Anatomy of Canines
  • Canines, also known as cuspids, are prominent teeth located at the corners of both the maxillary (upper) and mandibular (lower) dental arches. They are known for their distinctive shape, characterized by a pointed and conical crown. This pointed crown gives canines a sharp, "fang-like" appearance.

  • The crown of a canine tooth is supported by a single, sturdy root, making it one of the most stable teeth in the mouth. Canine teeth have a thin neck and are positioned between the incisors and premolars in the dental arch.

Function of Canines
  1. Cutting and Tearing: Canines are specialized for cutting and tearing food, particularly tough and fibrous substances like meat. Their pointed shape and sharp edges make them efficient at piercing and slicing through food items.

  2. Gripping: Canines also play a role in gripping and holding food in place during the chewing process. They help stabilize food while the molars grind it into smaller, digestible pieces.

  3. Aesthetic and Speech: Canine teeth are visible when a person smiles, and their alignment significantly impacts the aesthetics of the smile. Additionally, the upper canines are essential for certain speech sounds, such as "s" and "z," as they guide the airflow when pronouncing these sounds.

  4. Supporting Facial Structure: Canines contribute to the overall structure and appearance of the face, helping to maintain the shape of the lips and facial profile.

Note:

Canines have strong, long roots that can handle more pressure compared to incisors. When teenagers have too many teeth and not enough space for them to come in properly (dental crowding), their canines might not come out as they should. In X-rays, these unerupted canines are often found either up in the roof of the mouth or high up in the outer part of the gums. Sometimes, oral surgery is needed to help these teeth come out the right way.

Premolars

Premolars are teeth with 2 cups on their heads, usually called as cuspids. However, they are not found in temporary dentine but present in permanent dentine and are present after the canines. Furthermore, are smaller and shorter in size than the canines.

Temporary Dentine has 0 premolars. On the other hand, Permanent Dentine has 8 premolars. Four on maxilla and Four on mandible.

Anatomy of Premolars
  • Premolars, also known as bicuspids, are the teeth located behind the canines in both the maxillary (upper) and mandibular (lower) dental arches. They are characterized by having two prominent cusps or pointed projections on the biting surface, which is why they are referred to as bicuspids.

  • Premolars typically have a flatter and wider crown compared to canines, making them well-suited for grinding and crushing food. They have one or two roots depending on the specific tooth and are situated between the canines and molars.

Function of Premolars
  1. Grinding and Crushing: Premolars are primarily responsible for grinding and crushing food during the chewing process. The two cusps on their biting surface create a flat, broad area that efficiently breaks down food particles into smaller, digestible pieces.

  2. Supporting Mastication: Premolars work in conjunction with molars to support the mastication (chewing) process. They begin the process of breaking down food into smaller fragments before it reaches the molars for further grinding.

  3. Aiding in Speech: The alignment and position of premolars in the dental arch can affect speech articulation, particularly when pronouncing certain sounds and syllables.

  4. Supporting Facial Structure: Premolars contribute to the overall structure and alignment of the teeth within the dental arch, which, in turn, helps maintain the proper shape of the face and lips.

Note:

Premolar teeth sit between the canines and molars and have features of both. In baby teeth, there are no premolars. Dentists often remove premolar teeth to make more room in the mouth, especially before getting braces to fix crooked teeth.

Molars

Molars are the biggest and largest among all the teeth in dentine. They have three to five cups on their heads usually called as tri-cuspids. In temporary dentine, molars are present behind the canines, but in permanent dentine, molars are present behind the 2nd premolars.

Temporary Dentine has 8 Molars. Four on maxilla and Four on mandible. Permanent Dentine has 12 molars. six on maxilla and sex on mandible.

Anatomy of Molars:
  • In each quadrant of the human dental arch, there are three molars, making a total of twelve molars in the entire mouth—three in the upper (maxillary) arch and three in the lower (mandibular) arch on each side. Molars are positioned behind the premolars and form the posterior-most part of the dental arch.

  • Molars have a distinct structure that sets them apart from other teeth. They possess multiple cusps (raised projections) on their biting surfaces, which are adapted for grinding and crushing food. The cusps vary in number and arrangement depending on the type of molar.

Types of Molars:
  • First Molars: The first molars, also known as the six-year molars, are the first permanent molars to erupt in the mouth. They usually emerge between the ages of 6 to 7 years, behind the primary molars. First molars have four or five cusps and are among the largest teeth in the mouth. They have a significant impact on the alignment of the dental arch and the occlusion (bite) of the teeth.

  • Second Molars: The second molars, also known as the twelve-year molars, erupt behind the first molars. They typically emerge between the ages of 11 to 13 years. Second molars have four cusps and are also essential for chewing and maintaining proper dental alignment.

  • Third Molars (Wisdom Teeth): The third molars, commonly referred to as wisdom teeth, are the last molars to erupt in the mouth. They usually emerge between the ages of 17 to 25 years, although the timing can vary among individuals. Wisdom teeth can be the most problematic molars, as they often lack sufficient space to erupt properly, leading to various dental issues, such as impaction and crowding.

Function of Molars:
  • Chewing and Grinding: Molars play a central role in the mechanical breakdown of food. Their broad, flat surfaces and multiple cusps allow them to crush, grind, and chew food effectively. By breaking down food into smaller particles, molars aid in the initial stages of digestion, facilitating better nutrient absorption in the gastrointestinal tract.

  • Food Processing: As part of the dentition's chewing mechanism, molars complement the roles of other teeth. Incisors help with cutting and tearing food, canines aid in ripping and tearing, and premolars assist in initial grinding. Molars take on the final and most substantial grinding tasks, ensuring that food is appropriately processed before being swallowed.

  • Maintaining Dental Alignment: Molars are instrumental in maintaining the alignment of the dental arch and preserving the occlusion (bite) of the teeth. Proper dental alignment is essential for effective chewing, speaking, and maintaining the overall structure and stability of the jaw.

Note:

Molar teeth are prone to tooth decay because they have deep grooves on the top surface and a wide area where they touch neighboring molars. These spots are harder to clean compared to the flat surfaces on the front, back, tongue, and roof of the mouth.

Reference

  • "Forensic DNA Typing" by John M. Butler

  • "The Forensic Casebook: The Science of Crime Scene Investigation" by Ngaire E. Genge

  • "Forensic Science: A Very Short Introduction" by Jim Fraser

  • "Practical Crime Scene Processing and Investigation" by Ross M. Gardner