Tuesday, 3 November 2015
Tuesday, 6 October 2015
Types of Teeth and Their Functions
The four front teeth in each arch are called incisors, and their
function is to cut food with their sharp thin edges. On each side of
the incisors, at the corners of the mouth, are the canines. These teeth
have one cusp, or pointed edge, and are used for holding or grasping
food, and are very strong, stable teeth. Behind the canines are the
premolars, which are designed for holding food like the canines because
they have cusps, but they also function to crush food. Sometimes these
teeth are referred to as bicuspids, meaning two cusps, but this is not
always accurate because some premolars may have three cusps. Therefore
the term premolar is preferred. The teeth farthest back in the mouth
are the molars. These teeth have broad chewing surfaces with four or
five cusps, and are designed for grinding food. The incisors and
canines are called anterior teeth, because they are located in the front
of the mouth, while the premolars and molars are called posterior teeth
because they are located in the back of the mouth.
In
addition to aiding in acquiring and chewing food, teeth perform several
other important functions within the oral cavity. They begin the
digestive process by breaking down food; they protect the oral cavity;
they aid in proper speech; and they affect physical appearance. There
are several types of teeth, and each performs its own special function
in the chewing process, depending on its size, shape and location within
the jaws. Starting at the midline, the permanent dentition is
comprised of incisors, canines, premolars and molars. The primary
dentition is the same except it has no premolars.
Incisors
There are four incisors in each arch. Two central incisors and two lateral incisors.
There are two canines in each arch. They are sometimes referred to as cuspids.
There are for premolars in each arch. Two first premolars and two second premolars. They are sometimes referred to as bicuspids. There are no premolars in the primary dentition.
There are three molars in each arch of the permanent dentition. Two first molars, two second molars and two third molars. Third molars are sometimes called wisdom teeth. There are two molars in each arch of the primary dentition. Two first molars and two second molars.
| Primary Dentition |
 |
| Primary dentition diagram of primary teeth in order in the arch. |
| Permanent Dentition |
 |
| Permanent dentition diagram of permanent teeth in order in the arch. |
Incisors
There are four incisors in each arch. Two central incisors and two lateral incisors.
- Location – the central incisors are side by side at the midline. There is a lateral incisor on each side of the central incisors.
- Shape – single rooted, crowns are arched and angle toward one sharp incisal edge.
- Function – to cut or incise food with their thin edges.
There are two canines in each arch. They are sometimes referred to as cuspids.
- Location – next to the lateral incisors, establishes the cornering of the arches.
- Shape – anchored with the longest root, one pointed cusp.
- Function – used for holding, grasping, and tearing food. Referred to as the cornerstone of the mouth.
There are for premolars in each arch. Two first premolars and two second premolars. They are sometimes referred to as bicuspids. There are no premolars in the primary dentition.
- Location – first premolars are next to the canines followed by the second premolars.
- Shape – maxillary first premolars have a bifurcated root, all others have one root, one prominent cusp with one or two lesser lingual cusps.
- Function – holding food, like canines because they have cusps; also to crush food.
There are three molars in each arch of the permanent dentition. Two first molars, two second molars and two third molars. Third molars are sometimes called wisdom teeth. There are two molars in each arch of the primary dentition. Two first molars and two second molars.
- Location – first molars are next to the second premolars, second molars next to the first molars and third molars next to the second molars. The third molars are the farthest teeth in the mouth.
- Shape – bifurcated or trifurcated roots, broad chewing surfaces with four to five cusps.
- Function – grinding food.
Why Do Honeybees Dance?
Julian O'Dea :
When a honeybee returns to the hive after a successful foraging trip, she often performs a dance that reflects in miniature the details of her trip. Yet current research suggests that locational information contained in the dance is not communicated to other bees. So what is the reason for the dance? Here, Julian O'Dea offers an evolutionary explanation.
Julian O'Dea :
When a honeybee returns to the hive after a successful foraging trip, she often performs a dance that reflects in miniature the details of her trip. Yet current research suggests that locational information contained in the dance is not communicated to other bees. So what is the reason for the dance? Here, Julian O'Dea offers an evolutionary explanation.
James Hansen:
All glaciers in America's Glacier National Park are retreating inexorably to their final demise. Global warming is real, and the melting ice is a portent of potentially disastrous consequences. Yet most gloom-and-doom climate scenarios exaggerate trends of the agents that drive global warming. Study of these forcing agents shows that global warming can be slowed, and stopped, with practical actions that yield a cleaner, healthier atmosphere.
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