Wednesday 30 November 2011

Human Dentition




Dentition is the type and arrangements of teeth in the oral cavity. In other words it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. The dentition in human can be clinically divided into three stages.

A.      The Primary dentition consists of 20 teeth in all: ten upper and ten lower teeth. Primary teeth or milk teeth or deciduous teeth are called the first teeth of a child.  They start appearing in the mouth at the age of 6 months and continue to do so till the age of 2.5 to 3 years and entirely replaced by about ages 12 - 13. There is no premolar in primary dentition.


Deciduous Dentition


                                                                                                         
B.    The mixed dentition is composed of both primary and permanent teeth. It commences with the eruption of the first of the permanent tooth at about age six, and ends with the loss of the last of the deciduous tooth at about the age of 12-13 years.


C.     Stage of Permanent dentition, lasting from 13 years onwards. During this stage only permanent teeth are present. There are 32 permanent and only 20 deciduous teeth. Therefore, 12 permanent teeth erupt in the oral cavity which does not have any deciduous predecessors.  Deciduous molars are replaced by premolars in the permanent dentition.

Permanent Dentition

         
                                    

 The teeth are arranged in two dental arches: 1. Maxillary or upper arch 2. Mandibular or lower arch. There are equal numbers of teeth in the upper arch and lower arch. The arrangement of teeth is symmetrical in the right and the left halves in each arch. Thus in each arch there is 10 deciduous teeth in deciduous dentition and 16 permanent teeth in permanent dentition. In other words, each of four quadrants of the jaws will have 5 deciduous teeth in primary dentition and 8 permanent teeth in secondary dentition. The teeth of one half of the jaws are exact mirror image of the other half.    

Primary dentition- time of eruption




                                           

Time of eruption of Permanent tooth


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Monday 28 November 2011

Structure of Tooth


Anatomical tooth consists of mainly two parts. The part which is visible in the oral cavity is called crown. And the rest which is embedded in the gum and bone of the jaw is called root. The crown of different tooth may vary in shape and size. The root may be single as it is in the incisors and the canines or they may be multiple as it is in the molars. The part of the root area immediately adjacent to the crown is called the neck of the tooth.
The tooth enamel is a protective tooth structure that covers the exposed part of tooth; crown. It is the hardest of the parts of the tooth and also the hardest of all the tissues of human body. It is a highly mineralized structure. It is thickest over the cusps of molars and incisal edge of incisors. It thins down to a knife edge at the cervical margin. Enamel dissolves in acid media. Inorganic substances forms the main constituent of enamel. The inorganic element is composed of apatite molecules, chiefly hydroxyapatite. Calcium and phosphorus [Ca10(OH)2(PO4)6] form the major constituent of enamel.
Beneath the enamel (and sometimes exposed to the surface if the enamel is missing or worn away) is an intermediate layer of tissues which forms the main mass of tooth is called Dentin. It is also similar to bone but not nearly as hard as enamel. It supports the tooth enamel and absorbs the pressure of mastication. The dentin consists of number of micro-fibers embedded in a dense homogeneous matrix of collagenous protein.
Cementum covers the anatomical root outside the dentin (under the gum line) and it is attached to the bone of the jaw with little elastic fibers(Periodontal Ligaments). Cementum is hard as bone but not as hard as the tooth enamel. The cementum also consists of organic and inorganic matter. Some of the functions of cementum are: 1. It attaches one end of the periodontal ligament and helps to keep the tooth in the socket. 2. It protects root surface from injury and resorption by continuous formation. It repairs any defect in the root. 3. Helps eruption by apposition which compensates for occlusal wear.4. Helps to maintain width of the periodontal ligament.
Inside the dentin there is a cavity called pulp cavity which is filled with pulp. The pulp cavity in the crown area is called the pulp chamber and in the root portion it is known as the pulp canal or the root canal. Dental pulp is found inside the pulp chamber and the root canal. It is a soft connective tissue containing nerves and blood vessels that nourish the tooth. It is the most internal structure of tooth. The nerve fibers and the blood vessels enter into the tooth through an opening called apical foramen. The major functions of pulp are 1. Formative: formation of dentin 2. Sensory: the sensation of tooth is felt through the nerves of the pulp. 3. Nutritive: It supplies nutrition to the dentin through blood vessels and maintain vitality of tooth.4. Defensive: Pulp protect itself and the vitality of the tooth by producing secondary dentin.

Sunday 27 November 2011

Father of Dental Hygiene

           Dr. Alfred Civilion Fones (1869-1938) 
                       Father Of Dental Hygiene 

         Dr. Alfred Civilion Fones (1869-1938), Dentist and Social Reformer, from Bridgeport, Connecticut made a major creative foot step in the’ Dental Hygiene’ movement. He was born in Bridgeport, in 1869 and graduated from the New York College of Dentistry in 1890. In 1906 he trained his cousin, Irene E. Newman, to clean teeth and perform other preventive treatments for children, making the world’s first Dental Hygienist.  In 1913 Dr. Fones opens the Fones Clinic for Dental Hygienist in Bridgeport. It was the world’s first Dental Hygiene School. Dr. Fones, first to use the term "dental hygienist," today is known as the Father of Dental Hygiene.

The History of Oral and Dental Hygiene


Introduction

Dental hygiene has not always been the way as it is now. Some people take this daily routine very lightly and suffer the consequences later. Today, maintaining healthy teeth and gum is a lot easier than what it use to be back a few thousand years ago. Many of us will be walking around right now with a mouth full of bad odors and in some cases a mouth without teeth if we were still practicing oral hygiene the old way.

Early Civilization

Around 3500 B.C. people pretty much ate their food and went about their business until the Egyptians invented a form of ‘toothbrush’ by using a stick frayed at the end to make it soft.  Tombs of the ancient Egyptians have been found containing tooth sticks alongside their owners. To clean the teeth the soft end of the stick was rubbed against the gum and teeth to clean them. This was done without any cleaning material such as our present day toothpaste. In some instances, people used porcupine quill to pick food particles from between their teeth or chewed on a stick to clean them. The Ebers papyrus contains much reference to gingival disease and offers a number of prescriptions for strengthening the teeth and gums. These remedies were made from various plants and minerals and were applied to the gum in the form of paste with honey or vegetable gum. Oral hygiene was practiced by Sumerians of 3000 BC, and elaborately gold tooth picks found in the excavations at Ur in Mesopotamia suggest an interest in cleanliness of the mouth.
Ancient Chinese medical works also discussed periodontal disease and dental hygiene. In the oldest book, written by Huang-Ti about 2500 BC, there is chapter devoted to dental and gingival disease. Oral diseases were divided into three types: Fong Ya, or inflammatory conditions; Ya Kon, or disease of the soft investing tissues of the teeth; and Chong Ya, or dental caries. The Chinese were among the earliest people to use the “Chew Stick” as a tooth pick and tooth brush to clean the teeth and massage the gingival tissues. The Chinese are believed to have invented the first natural bristle toothbrush made from the bristles from pigs' necks in the 15th century, with the bristles attached to a bone or bamboo handle. The downside in using this toothbrush was that the bristles were too tough and caused serious bleeding of the gum after using it. To deal with this problem, people eventually replaced the toothbrush bristles with hair from the back of horses, which were much softer than boar bristles.
The medical works of ancient India devote a significant amount of space to oral and periodontal problems. In the Susruta Samhita, there is numerous description of severe periodontal disease. In a later treatise Charaka Samhitha, tooth brushing and oral hygiene are stressed: “The stick for brushing the teeth should be either astringent or pungent or bitter. One of its ends should be chewed in the form of a brush. It should be used twice a day, taking care that the gum not be injured”.
Again, it was the Egyptians who came up with the idea of using something on the toothbrush to improve the cleaning of the teeth and at the same time remove bad breath. They made a powdered mixture consisted of rock salt, mint, and pepper. The mixture was mixed with saliva and applied to the gum. The downside to using this was the same old problem of bleeding gum.  Persians also gave it a shot of making toothpaste. They tried making toothpaste from the ashes from burnt goat’s feet. This also led to gum bleeding and widespread diseases. Obviously, a lot of people died from this. In the eighteen-century, the British also tried their hands at making toothpaste. The toothpaste was made of brick dust, crushed clay. This toothpaste caused serious erosion of the tooth enamel. This toothpaste did not stay around long.
Ancient toothpastes were used to treat some of the same concerns that we have today – keeping teeth and gums clean, whitening teeth and freshening breath. The ingredients of ancient toothpastes were however very different and varied. Ingredients used included a powder of ox hooves' ashes and burnt eggshells that was combined with pumice. The Greeks and Romans favoured more abrasiveness and their toothpaste ingredients included crushed bones and oyster shells. The Romans added more flavoring to help with bad breath, as well as powdered charcoal and bark. The Chinese used a wide variety of substances in toothpastes over time that has included ginseng, herbal mints and salt. By the nineteen-century, there were several types of toothpaste available. There was toothpaste in particular made from- charcoal powder.
Later Dr. Alfred Civilion Fones (1869-1938), Dentist and Social Reformer, from Bridgeport, Connecticut made a major creative foot step in the’ Dental Hygiene’ movement. He was born in Bridgeport, in 1869 and graduated from the New York College of Dentistry in 1890. In 1906 he trained his cousin, Irene E. Newman, to clean teeth and perform other preventive treatments for children, making the world’s first Dental Hygienist.  In 1913 Dr. Fones opens the Fones Clinic for Dental Hygienist in Bridgeport. It was the world’s first Dental Hygiene School. Dr. Fones, first to use the term "dental hygienist," today is known as the Father of Dental Hygiene.

Saturday 26 November 2011

Functions Of Tooth




1.  Phonation: The teeth work with the other structures in the oral cavity like tongue,palate (both hard and soft palate) and lips to make sounds.
2.  Mastication: Humans have different types of tooth each having typical appearance and performing particular function. The Incisors arranged in the anterior part of the oral cavity help to incise the food. They are flat and sharp. Canine are the teeth which present at each corner of mouth help in shearing the food. Next to the Canines the Premolars which have broader grinding surface and play a major role in grinding and chewing the food. The molars are large teeth arranged at the back of the oral cavity having a large grinding surface mainly to grind the food.
3.  Aesthetics: They offer support to the facial tissues and hence play a major role in the facial appearance.
4.  Protection. It has also got a major role in self protection and attack, especially in animals as they have more stronger teeth than human.