Sigmund Freud was one of the most influential psychologists when it came to the topic of personality. Freud was not originally a psychologist or psychiatrist but a neurologist. After studying a woman in Paris with a mental disorder, Freud directed his attention on the unconscious mind.
For Freud, he came up with the Freud Model of Personality Structure. It is based off of the three ideas that personality is shaped by a person's id, ego, and superego. The Id represents primitive impulses which drives our behavior. This would be the home of the sexual drive otherwise known as the libido that Freud believed to be a main source for a persons unconscious decisions. The Id operated off of the pleasure principle, which would strive for immediate gratification. The ego would be the decision maker of the personality. The ego interacts with the real world and uses the reality principle. The reality principle strove to delay gratification until it could find an appropriate outlet. The superego is known as the sense of morality. This would be the equivalent to voices in our head telling us what is right and what is wrong. According to Freud, this is where our guilt lies.
Freud believed that the three components of personality worked together when creating dreams. He believed that dreams were symbolic. He also believed that dreams were wish fulfillments. He felt that many items such as umbrellas, ties, and tunnels were all sexual innuendos. How ever, I disagree. I do not believe that everything is aimed at being sexual in dreams. Also, I do not agree that if you dream of an object it only means one thing. According to http://www.dreammoods.com/dreamthemes/bodyparts.htm#Teeth, when you have a loose tooth it means that it is a sign of failure where as source http://www.meaning-of-dreams.net/dreams/tooth.html says that if you loose a tooth it signifies the loose of innocence.
As you can see, Freud's theory of dreams is not very accurate when it comes to symbolism due to the fact that everyone interprets dreams different.