Diseases of the Teeth

Adults have 32 permanent teeth, including the incisors, canines, premolars, and molars. As shown in Figure 1, the crown of a tooth rises above the gingiva, and the root is the portion embedded in alveolar bone. The periodontal ligament suspends a tooth and its roots in the bone and is made up of collagen fibers. The major component of teeth is a bone-like substance called dentin. Inside the tooth lies the pulp, containing blood vessels and nerves. The crown is covered by enamel and the roots are covered by cementum.

Fig.1 Tooth Anatomy

Diseases of the teeth are frequently identified by clinical inspection of the oral cavity and by x-ray examination. Common radiographs include periapical views to identify the crown and root, bite-wing radiographs to examine the interproximal spaces, occlusal views to image large segments of the dental arch, and panoramic views to identify both dental arches and their supporting structures. Periapical, bite-wing, and occlusal radiographs are intraoral films made by placing film inside the patient's mouth and directing the x-ray beam through the area to be imaged. Panoramic radiographs, which are extraoral films requiring special equipment to obtain, are frequently used since they can display the entire maxillomandibular region on a single film.

Dental caries, or injury and destruction of the calcified structures of the teeth by Streptococcus species and other bacteria, continue to be extremely prevalent in the United States. Although less than 15% of US adults are free of caries, the absolute number of caries per individual during the past 50 years has declined. This is due in part to preventive measures such as water fluoridation and the use of toothpaste, supplements, and mouth rinses that contain fluoride.

Caries may occur on smooth tooth surfaces, chewing surfaces, and most commonly in pits and fissures (Fig 2). To prevent caries in the pits and grooves of occlusal surfaces of posterior teeth, dental sealants have been developed. These materials modify the resistance of teeth to caries by coating the occlusal grooves with an adherent material such as a plastic resin. Dental sealants are currently indicated for newly erupted teeth with significant pits and fissures or for patients with significant previous occlusal caries. Once dental caries occur, they are treated by removal of the affected tissue and replacement with a restorative material such as silver amalgam, gold, or composite. The primary goal, however, is prevention of caries through dietary modification, limitation of sucrose-containing food, use of fluoride supplements, and antibacterial measures such as daily personal oral hygiene and regular professional cleanings.

Fig 2. Pit and Fissure

taken from : http://www.medscape.com/viewarticle/410839

dental composite

Dental composites (white fillings) are a group of restorative materials used in dentistry. As with other composite materials, a dental composite typically consists of a resin-based oligomer matrix, such as a bisphenol A-glycidyl methacrylate BISMA or urethane dimethacrylate (UDMA), and an inorganic filler such as silicon dioxide silica. Compositions vary widely, with proprietary mixes of resins forming the matrix, as well as engineered filler glasses and glass ceramics. The filler gives the composite wear resistance and translucency. A coupling agent such as silane is used to enhance the bond between these two components. An initiator package begins the polymerization reaction of the resins when external energy (light/heat, etc.) is applied. A catalyst package can control its speed.

the teeth and your teeth

You bite into an apple and then try to start talking to your friend about yesterday's math homework. Suddenly something feels funny — one of your baby teeth has fallen out! It's been loose forever, and now there it is, right in your hand. And you have an empty space in your mouth big enough to poke a drinking straw through.

Before you put that tooth under your pillow, did you know that there is much more to that tooth than meets the eye? A single tooth has many different parts that make it work. And teeth play an important role in your daily life. They not only let you eat stuff like apples, they also help you talk. So let's talk teeth!

Tiny Teeth

Unlike your heart or brain, your teeth weren't ready to work from the day you were born. Although babies have the beginnings of their first teeth even before they are born, teeth don't become visible until babies are about 6 to 12 months old.

After that first tooth breaks through, more and more teeth begin to appear. Most kids have their first set of teeth by the time they are 3 years old. These are called the primary or baby teeth, and there are 20 in all. When a child gets to age 5 or 6, these teeth start falling out, one by one.

A primary tooth falls out because it is being pushed out of the way by the permanent tooth that is behind it. Slowly, the permanent teeth grow in and take the place of the primary teeth. By about age 12 or 13, most kids have lost all of their baby teeth and have a full set of permanent teeth.

There are 28 permanent teeth in all — eight more than the original set of baby teeth. Between the ages of 17 and 21, four more teeth called wisdom teeth usually grow in at the back of the mouth. They complete the adult set of 32 teeth.

Tooth Tour

Let's take a tour of your teeth. Look in the mirror at your own teeth or check out a friend's smile. The part of the tooth you can see, which is not covered by the gum (your gums are the pink, fleshy part), is called the crown. The crown of each tooth is covered with enamel (say: ih-nam-ul), which is very hard and often shiny. Enamel is a very tough substance and it acts as a tooth's personal bodyguard. Enamel works as a barrier, protecting the inside parts of the tooth.

If you were able to peel away the enamel, you would find dentin (say: den-tin). Dentin makes up the largest part of the tooth. Although it is not as tough as enamel, it is also very hard.

Dentin protects the innermost part of the tooth, called the pulp. The pulp is where each tooth's nerve endings and blood supply are found. When you eat hot soup, bite into a super-cold scoop of ice cream, fall and hurt a tooth, or get a cavity, it's your pulp that hurts. The nerve endings inside the pulp send messages to the brain about what's going on ("That ice cream is too cold!"). The pulp also contains the tooth's blood vessels, which feed the tooth and keep it alive and healthy.

The pulp goes all the way down into the root of the tooth, which is under the gum. Cementum (say: sih-men-tum) makes up the root of the tooth, which is anchored to the jawbone.

Tooth Types

You've probably noticed that you have different types of permanent teeth in your mouth. Each one has its own function.

Your two front teeth and the teeth on either side of them are incisors (say: in-sy-zurs). There are four on the top and four on bottom.

Incisors are shaped like tiny chisels, with flat ends that are somewhat sharp. These teeth are used for cutting and chopping food. Think back to that apple you ate: You used your incisors to crunch into the skin of the apple.

The pointy teeth beside your incisors are called canine (say: kay-nine) teeth. There are four of them, two on top and two on bottom. Because these teeth are pointy and also sharp, they help tear food.

Next to your canine teeth are your premolars (say: pree-mo-lurs), which are also called bicuspid teeth. You have eight premolars in all, four on top and four on the bottom. You'll need to open a bit wider to see these teeth, but when you do, you'll notice that their shape is completely different from both incisors and canines. Premolars are bigger, stronger, and have ridges, which make them perfect for crushing and grinding food.

If you open your mouth really wide, you'll see your molars (say: mo-lurs). You have eight of these, four on the top and four on the bottom. Sometimes these are called your 6-year molars and your 12-year molars because that is around the time when they come in.

Molars are the toughest of the bunch. They are even wider and stronger than premolars, and they have more ridges. Molars work closely with your tongue to help you swallow food. How? The tongue sweeps chewed-up food to the back of your mouth, where the molars grind it until it's mashed up and ready to be swallowed.

As we mentioned earlier, the last teeth a person gets are wisdom teeth. These are also called third molars. They are all the way in the back of the mouth, one in each corner.

Wisdom teeth aren't used for anything and they are often removed because they can cause problems in a person's mouth. Some people believe that wisdom teeth may have been used by people millions of years ago to help them chew food. It's believed that they're called wisdom teeth because they come in later in life, when a young person is older and wiser.

Tooth Talk

Your teeth are great for chewing, but you also need them to talk. Different teeth work with your tongue and lips to help you form sounds. Try saying the word "tooth" slowly and notice how your tongue first hits the inside of your incisors to produce the hard "t" sound and then goes in between your upper and lower teeth to make the "th" sound.

And if you love to sing "la la la la la," you can thank those teeth every time you sing a song. Pay attention to what happens to your teeth and tongue every time you make the "l" sound.

Treating Teeth Kindly

Brushing your teeth with fluoride toothpaste is your best bet when it comes to keeping your teeth in tip-top shape. Try to brush after eating or at least twice a day. It's especially important to brush before bedtime.

The best way to brush your teeth is in little circles — go around and around until you have covered every surface of every tooth. Brush up and down, rather than side to side. You'll also want to clean between your teeth with dental floss (a special string for cleaning your teeth) at least once a day. That removes food and plaque (sticky stuff that can cause cavities or gum disease) that get stuck in between your teeth. You can also brush your tongue to help keep your breath fresh!

It's also important to visit your favorite tooth experts — your dentist and dental hygienist. During your appointment, they'll look out for any problems and clean and polish your teeth. Sometimes the dentist will take X-rays to get a better picture of what is going on in your mouth. You also might get a fluoride treatment while you're there.

In between dentist visits, you can prevent problems by eating fewer sugary snacks and sugary drinks, such as soda. Sugar can hurt your teeth and cause tooth decay, or cavities. But if you take care of your teeth now, you'll be chewing like a champ for the rest of your life!

Reviewed by: Kenneth H. Hirsch, DDS, and Larissa Hirsch, MD
Date reviewed: May 2007

source : http://kidshealth.org/kid/htbw/teeth.html

the dentitry

Dentistry is the "evaluation, diagnosis, prevention and/or treatment (nonsurgical, surgical or related procedures) of diseases, disorders and/or conditions of the oral cavity, maxillofacial area and/or the adjacent and associated structures and their impact on the human body". Dentistry is necessary for complete oral health. Those in the practice of dentistry are known as dentists. Other people aiding in oral health service include dental assistants, dental hygienists. dental technicians, and dental therapists.



History

Evidence of ancient dentistry has recently been found in a Neolithic graveyard in the Indus River basin of Pakistan. Teeth dating from around 7000 to 5500 BC show evidence of holes from dental drills. The teeth were found in people of the Indus Valley Civilization. A Sumerian text from 5000 BC describes a "tooth worm" as the cause of dental caries. Evidence of this belief has also been found in ancient India, Egypt, Japan, and China. The legend of the worm is also found in the writings of Homer, and as late as the 1300s AD the surgeon Guy de Chauliac still promoted the belief that worms cause tooth decay.

The Edwin Smith Papyrus, written in the 17th century BC but which may reflect previous manuscripts from as early as 3000 BC, includes the treatment of several dental ailments. In the 18th century BC, the Code of Hammurabi referenced dental extraction twice as it related to punishment. Examination of the remains of some ancient Egyptians and Greco-Romans reveals early attempts at dental prosthetics and surgery.

Ancient Greek scholars Hippocrates and Aristotle wrote about dentistry, including the eruption pattern of teeth, treating decayed teeth and gum disease, extracting teeth with forceps, and using wires to stabilize loose teeth and fractured jaws. The first use of dental appliances or bridges comes from the Etruscans from as early as 700 BC. Roman medical writer Cornelius Celsus wrote extensively of oral diseases as well as dental treatments such as narcotic-containing emollients and astringents.

Medieval dentist extracting a tooth. London; c. 1360-75.

Historically, dental extractions have been used to treat a variety of illnesses. During the Middle Ages and throughout the 19th century, dentistry was not a profession in itself, and often dental procedures were performed by barbers or general physicians. Barbers usually limited their practice to extracting teeth, which not only resulted in the alleviation of pain, but often cured a variety of ailments linked to chronic tooth infection. Instruments used for dental extractions date back several centuries. In the 14th century, Guy de Chauliac invented the dental pelican^[30] (resembling a pelican's beak) which was used up until the late 18th century. The pelican was replaced by the dental key which, in turn, was replaced by modern forceps in the 20th century.^{[citation needed]}

The first book focused solely on dentistry was the "Artzney Buchlein" in 1530, and the first dental textbook written in English was called "Operator for the Teeth" by Charles Allen in 1685. It was between 1650 and 1800 that the science of modern dentistry developed. It is said that the 17th century French physician Pierre Fauchard started dentistry science as we know it today, and he has been named "the father of modern dentistry". Among many of his developments were the extensive use of dental prosthesis, the introduction of dental fillings as a treatment for dental caries and the statement that sugar derivate acids such as tartaric acid are responsible for dental decay.

source : http://en.wikipedia.org/wiki/Dentistry