Mammalian Teeth (Dentition) - SS1 Biology Lesson Note

Dentition refers to the arrangement, type, and number of teeth in an animal's mouth. It plays a crucial role in an animal's feeding habits and determines how they process and consume their food. Different types of teeth are adapted for specific functions such as biting, tearing, grinding, or chewing depending on the animal.

Homodont dentition and heterodont dentition are two different types of tooth arrangements seen in animals.

1.     Homodont Dentition: Homodont dentition refers to a dental arrangement where all teeth are the same in shape and size. In animals with homodont dentition, each tooth performs a similar function. Homodont dentition is commonly observed in animals that have simple feeding habits and consume a uniform diet. For example, most fish, reptiles (such as crocodiles), and some mammals (such as dolphins) have homodont dentition. In these animals, the teeth are typically pointed and cone-shaped, allowing for grasping and swallowing prey whole or in large pieces.

Figure 74 image from gettyimages.idk

1.     Heterodont Dentition: Heterodont dentition refers to a dental arrangement where different types of teeth are present in the mouth, each specialized for a specific function. Heterodont dentition allows for a more diverse diet and facilitates the processing of various types of food. It is found in many mammals, including humans. In heterodont dentition, teeth are differentiated into specific types such as incisors, canines, premolars, and molars, each with a distinct shape and function. Incisors are typically used for biting, canines for tearing, premolars for grinding and crushing, and molars for further grinding and chewing.

Figure 75 images from shaalaa.com

Milk teeth, also known as deciduous teeth or baby teeth, are the first set of teeth that develop in humans and many other mammals. They typically begin to erupt around six months of age and are gradually replaced by permanent teeth during childhood.

Humans have two sets of teeth: the milk teeth and the permanent teeth. Milk teeth are temporary and serve as placeholders for the permanent teeth that will eventually take their place. There are 20 milk teeth in total, consisting of:

1.     Incisors: There are four upper and four lower incisors in the milk dentition. These are the front teeth used for biting and cutting food.

2.     Canines: There are two upper and two lower canines in the milk dentition. Canines have a pointed shape and are used for tearing food.

3.     Molars: There are four upper and four lower molars in the milk dentition. These back teeth have a broader surface area for grinding and chewing food.

 

As a child grows, the milk teeth gradually start to fall out as the permanent teeth erupt. The process of shedding milk teeth and the eruption of permanent teeth typically occurs between the ages of six and twelve years. Permanent teeth are larger, stronger, and meant to last throughout adulthood. They include:

1.     Incisors: There are four upper and four lower incisors in the permanent dentition, just like in the milk dentition. These teeth continue to be used for biting and cutting food.

2.     Canines: There are two upper and two lower canines in the permanent dentition as well. Canines help with tearing and gripping food.

3.     Premolars: The milk molars are replaced by premolars in the permanent dentition. There are four upper and four lower premolars. They assist in grinding and crushing food.

4.     Molars: In addition to the premolars, the permanent dentition includes the third molars, also known as wisdom teeth. These are located at the back of the mouth and may or may not erupt fully. Wisdom teeth often require extraction due to problems like impaction or overcrowding.

The transition from milk teeth to permanent teeth is a natural part of dental development in humans. It allows for the growth of larger and stronger teeth to accommodate the changing needs of the growing child.