Your teeth are made of a hard, bonelike material. There are four parts:

• Enamel, your tooth's hard surface
• Dentin, the hard yellow part under the enamel
• Cementum, the hard tissue that covers the root and keeps your teeth in place
• Pulp, the soft connective tissue in the center of your tooth. It contains nerves and blood vessels.

You need your teeth for many activities that you may take for granted. These include eating, speaking and even smiling.

• Teeth are important for eating, speaking, self-confidence and overall health.
• We have two sets of teeth over our lifetime – baby (deciduous or primary) teeth and adult (permanent or secondary) teeth.
• Baby teeth begin to appear from around six months of age. Permanent teeth begin to appear at around the age of six or seven years.

Image: Dental Health Services Victoria

A person has two sets of teeth over their lifetime – baby teeth (also known as deciduous, primary or milk teeth) and adult (secondary or permanent) teeth. Baby teeth usually start to appear at about six months of age and children usually have their full set of 20 baby teeth by age three.

From about six or seven years of age, some baby teeth start to fall out and are slowly replaced by the adult teeth. By around 21 years of age, the average person has 32 adult teeth (which includes 4 wisdom teeth); 16 on the top and 16 on the bottom. Some people have less or even more than this number of teeth, which you can discuss with your oral health professional.

The health of your mouth is an important part of your overall health. Diseases in teeth and gums can affect other parts of your body, including the heart.

Role of teeth

Teeth play an important role in eating, chewing and nutrition. They are different shapes and sizes to bite, tear, crush or grind food before it is swallowed. They also help us to form sounds and speak clearly, and they are an important part of a person’s smile. In this respect, teeth can be associated with a person’s confidence and social interaction.

Baby teeth also play an important role in holding space for the adult teeth. For these reasons it is important to keep them healthy and prevent the early loss of these teeth due to disease.

Your tooth

Your teeth are made up of the following parts:

• crown – the part of the tooth that sits above the gum line
• enamel – the hard, smooth, white outer layer that protects the crown. Enamel is harder than bone and doesn’t have any nerves or a blood supply. Chipped or decayed enamel cannot grow back and may lead to further decay or wear.
• dentine – the middle layer under the enamel. If the enamel is damaged or decayed and the underlying dentine is exposed, the tooth can be sensitive to temperature and sweet or acidic foods.
• pulp – the living centre of the tooth containing blood vessels and nerves. The nerve provides the sensation of temperature, pressure and pain.
• root – the section of tooth that is usually below the gum line within the bone of the jaw. Different teeth can have one or many roots where nerves and blood vessels pass in and out of the pulp.
• cementum – a material that covers the root surface.

Teeth and eating

Teeth help us to eat by breaking food into smaller pieces so that it can be swallowed and digested. Over time, teeth can get worn down from normal and abnormal use.

Teeth have different shapes to do different jobs. Types include:

• incisors are front teeth which bite together like a pair of scissors. There are 4 upper and 4 lower incisors each in the baby and adult sets of teeth.
• canines are pointy shaped teeth (sometimes called fangs or eye teeth) just back from the incisors, which are used to tear food. There are 2 upper and 2 lower canines in the baby and adult sets of teeth
• premolars are between the canines and molars and help crush food. There are 4 upper and 4 lower adult premolars. There are no premolars in the baby teeth.
• molars are the back teeth, larger than premolars with big flat surfaces to grind food. There are six upper and six lower adult molars, and four upper and four lower molars in the baby teeth.

Caring for teeth

Teeth are important for eating, speaking and socialising, so it’s important to take good care of them.

Some tips include:

• Brush twice a day, in the morning and at night before bed - use a toothbrush with a small head and soft bristles. Gently brush your teeth and along your gum line, making sure to brush each tooth on the front, back, and top.
• Start toothbrushing from the first tooth - use toothbrushes with a small head and soft bristles. You can also use a wet cloth to wipe over teeth and gums for babies. Only use water to clean your baby’s teeth and gums until they are 18 months of age. Use age appropriate tooth brushes as you get older.
• From 18 months of age, use fluoride toothpaste - use a low-fluoride children’s toothpaste for children aged 18 months to six years, and standard fluoride toothpaste for from age six years and older.
• Avoid sugary, acidic or carbonated (fizzy) foods and drinks - watch out for sweet and sticky foods, soft drinks, fruit juices, energy drinks and even diet ‘no sugar’ carbonated drinks which can cause tooth decay in excess. If you do have these, it is better to have them at mealtimes rather than between meals.
• Drink plenty of tap water - most of Victoria’s has fluoridated tap water, which helps repair the tooth surface. If your water is not fluoridated (eg tank water), talk to your oral health professional about how to you can get the right amount of fluoride to best protect your teeth.
• Have a regular check-up - regular check-ups are important for identifying and treating any issues before they become bigger and harder to treat. There are also a number of treatments which help to prevent disease. Ask your oral health professional how often you should have a dental check-up.
• Wear a mouthguard when you train for and play sports where your teeth could get damaged - for example football, rugby, soccer, basketball, netball, water polo or hockey.
• Wear an occlusal splint or night guard at night if you have habits such as clenching or grinding of teeth - such habits can cause teeth and fillings to wear down, fracture, and be sensitive or even split in half.
• Quit smoking to improve your oral health and general health.

Tooth conditions

Some examples of problems that can affect the teeth include:

• tooth decay
• gum disease
• loss of the tooth surface (enamel) through:
  • dental erosion (caused by acids from food and drinks, or acids coming up from the stomach)
  • dental abrasion (often due to incorrect or forceful tooth brushing)
  • dental attrition and abfraction (often due to grinding or chewing)
• tooth and jaw alignment problems such as crooked, crowded or overlapping teeth
• tooth grinding (bruxism)
• tooth trauma, such as a broken or knocked out tooth
• developmental defects of the teeth such as ‘chalky teeth’ (molar hypomineralisation)

During the course of your lifetime, you have two sets of teeth (one set of teeth is a dentition). Your 20 deciduous teeth, or baby teeth, first begin to appear at about 6 months of age. Between approximately age 6 and 12, these teeth are replaced by 32 permanent teeth. Moving from the center of the mouth toward the side, these are as follows (image):

• The eight incisors, four top and four bottom, are the sharp front teeth you use for biting into food.
• The four cuspids (or canines) flank the incisors and have a pointed edge (cusp) to tear up food. These fang-like teeth are superb for piercing tough or fleshy foods.
• Posterior to the cuspids are the eight premolars (or bicuspids), which have an overall flatter shape with two rounded cusps useful for mashing foods.
• The most posterior and largest are the 12 molars, which have several pointed cusps used to crush food so it is ready for swallowing. The third members of each set of three molars, top and bottom, are commonly referred to as the wisdom teeth, because their eruption is commonly delayed until early adulthood. It is not uncommon for wisdom teeth to fail to erupt; that is, they remain impacted. In these cases, the teeth are typically removed by orthodontic surgery.

The teeth are secured in the alveolar processes (sockets) of the maxilla and the mandible. Gingivae (commonly called the gums) are soft tissues that line the alveolar processes and surround the necks of the teeth. Teeth are also held in their sockets by a connective tissue called the periodontal ligament.

The two main parts of a tooth are the crown, which is the portion projecting above the gum line, and the root, which is embedded within the maxilla and mandible. Both parts contain an inner pulp cavity, containing loose connective tissue through which run nerves and blood vessels. The region of the pulp cavity that runs through the root of the tooth is called the root canal. Surrounding the pulp cavity is dentin, a bone-like tissue. In the root of each tooth, the dentin is covered by an even harder bone-like layer called cementum. In the crown of each tooth, the dentin is covered by an outer layer of enamel, the hardest substance in the body (image).

Although enamel protects the underlying dentin and pulp cavity, it is still nonetheless susceptible to mechanical and chemical erosion, or what is known as tooth decay. The most common form, dental caries (cavities) develops when colonies of bacteria feeding on sugars in the mouth release acids that cause soft tissue inflammation and degradation of the calcium crystals of the enamel. The digestive functions of the mouth are summarized in image.

The cheeks, tongue, and palate frame the mouth, which is also called the oral cavity (or buccal cavity). The structures of the mouth are illustrated in image.

At the entrance to the mouth are the lips, or labia (singular = labium). Their outer covering is skin, which transitions to a mucous membrane in the mouth proper. Lips are very vascular with a thin layer of keratin; hence, the reason they are "red." They have a huge representation on the cerebral cortex, which probably explains the human fascination with kissing! The lips cover the orbicularis oris muscle, which regulates what comes in and goes out of the mouth. The labial frenulum is a midline fold of mucous membrane that attaches the inner surface of each lip to the gum. The cheeks make up the oral cavity’s sidewalls. While their outer covering is skin, their inner covering is mucous membrane. This membrane is made up of non-keratinized, stratified squamous epithelium. Between the skin and mucous membranes are connective tissue and buccinator muscles. The next time you eat some food, notice how the buccinator muscles in your cheeks and the orbicularis oris muscle in your lips contract, helping you keep the food from falling out of your mouth. Additionally, notice how these muscles work when you are speaking.

The pocket-like part of the mouth that is framed on the inside by the gums and teeth, and on the outside by the cheeks and lips is called the oral vestibule. Moving farther into the mouth, the opening between the oral cavity and throat (oropharynx) is called the fauces (like the kitchen "faucet"). The main open area of the mouth, or oral cavity proper, runs from the gums and teeth to the fauces.

When you are chewing, you do not find it difficult to breathe simultaneously. The next time you have food in your mouth, notice how the arched shape of the roof of your mouth allows you to handle both digestion and respiration at the same time. This arch is called the palate. The anterior region of the palate serves as a wall (or septum) between the oral and nasal cavities as well as a rigid shelf against which the tongue can push food. It is created by the maxillary and palatine bones of the skull and, given its bony structure, is known as the hard palate. If you run your tongue along the roof of your mouth, you’ll notice that the hard palate ends in the posterior oral cavity, and the tissue becomes fleshier. This part of the palate, known as the soft palate, is composed mainly of skeletal muscle. You can therefore manipulate, subconsciously, the soft palate—for instance, to yawn, swallow, or sing (see image).

A fleshy bead of tissue called the uvula drops down from the center of the posterior edge of the soft palate. Although some have suggested that the uvula is a vestigial organ, it serves an important purpose. When you swallow, the soft palate and uvula move upward, helping to keep foods and liquid from entering the nasal cavity. Unfortunately, it can also contribute to the sound produced by snoring. Two muscular folds extend downward from the soft palate, on either side of the uvula. Toward the front, the palatoglossal arch lies next to the base of the tongue; behind it, the palatopharyngeal arch forms the superior and lateral margins of the fauces. Between these two arches are the palatine tonsils, clusters of lymphoid tissue that protect the pharynx. The lingual tonsils are located at the base of the tongue.

The mouth, or oral cavity, is the first part of the digestive tract. It is adapted to receive food by ingestion, break it into small particles by mastication, and mix it with saliva. The lips, cheeks, and palate form the boundaries. The oral cavity contains the teeth and tongue and receives the secretions from the salivary glands.

Lips and Cheeks

The lips and cheeks help hold food in the mouth and keep it in place for chewing. They are also used in the formation of words for speech. The lips contain numerous sensory receptors that are useful for judging the temperature and texture of foods.

Palate

The palate is the roof of the oral cavity. It separates the oral cavity from the nasal cavity. The anterior portion, the hard palate, is supported by bone. The posterior portion, the soft palate, is skeletal muscle and connective tissue. Posteriorly, the soft palate ends in a projection called the uvula. During swallowing, the soft palate and uvula move upward to direct food away from the nasal cavity and into the oropharynx.

Tongue

The tongue manipulates food in the mouth and is used in speech. The surface is covered with papillae that provide friction and contain the taste buds.

Teeth

A complete set of deciduous (primary) teeth contains 20 teeth. There are 32 teeth in a complete permanent (secondary) set. The shape of each tooth type corresponds to the way it handles food.

Both physical and chemical digestion begin in the mouth or oral cavity, which is the point of entry of food into the digestive system. The food is broken into smaller particles by mastication, the chewing action of the teeth. All mammals have teeth and can chew their food to begin the process of physically breaking it down into smaller particles.

The chemical process of digestion begins during chewing as food mixes with saliva, produced by the salivary glands (Figure 16.5). Saliva contains mucus that moistens food and buffers the pH of the food. Saliva also contains lysozyme, which has antibacterial action. It also contains an enzyme called salivary amylase that begins the process of converting starches in the food into a disaccharide called maltose. Another enzyme called lipase is produced by cells in the tongue to break down fats. The chewing and wetting action provided by the teeth and saliva prepare the food into a mass called the bolus for swallowing. The tongue helps in swallowing—moving the bolus from the mouth into the pharynx. The pharynx opens to two passageways: the esophagus and the trachea. The esophagus leads to the stomach and the trachea leads to the lungs. The epiglottis is a flap of tissue that covers the tracheal opening during swallowing to prevent food from entering the lungs.

Figure 16.5 (a) Digestion of food begins in the mouth. (b) Food is masticated by teeth and moistened by saliva secreted from the salivary glands. Enzymes in the saliva begin to digest starches and fats. With the help of the tongue, the resulting bolus is moved into the esophagus by swallowing. (credit: modification of work by Mariana Ruiz Villareal)

Babies are usually born with 20 baby teeth (also known as primary teeth). They start to come through the gums at about 6 months and all the teeth have usually appeared by the time the baby is 2 to 3 years old. This process is called teething. The teeth will fall out at various times during childhood.

About baby teeth

Babies are born with the following teeth:

• 4 second molars
• 4 first molars
• 4 canine teeth
• 4 lateral incisors
• 4 central incisors

There is one set on each side of the upper jaw, and one on each side of the lower jaw.

The teeth in the centre of the bottom jaw often come through first, sometime between 4 months and 10 months.

Each child is different so don’t worry if your baby’s teeth appear earlier or later. Talk to your dentist if you are worried.

Diagram showing the 5 sets of temporary teeth.

Your child’s jaw will continue to grow and permanent teeth will start to replace the baby teeth when the child is around age 6.

The outer covering of baby teeth is made of thinner enamel than the enamel of permanent teeth and this makes the baby teeth look whiter. It also means they are more likely to get tooth decay.

Baby teeth also have shorter and different shaped roots from permanent teeth, making it easier for the roots to dissolve later and to allow space for permanent teeth to grow underneath them.

Babies can be quite uncomfortable when they are teething. Try chilled (not frozen) teething rings, wash cloths or dummies to ease the pain.

Baby teeth are important

Baby teeth help your child to chew food easily and to pronounce words properly. They are also needed to hold a place in the jaw for the permanent teeth to come through later.

It is important to keep baby teeth clean. This will protect against infection, cavities and pain. Decayed baby teeth can damage the permanent teeth underneath.

How to care for baby teeth

Baby teeth can start to decay as soon as they appear in the mouth. Frequent exposure to sugary liquids can destroy the teeth.

You should wipe your baby’s gums with a wet facecloth or a clean gauze pad after each feed. You can brush your baby’s first tooth as soon as it appears with a soft toothbrush and a little water.

Older children should be supervised while they are cleaning their teeth. Children over 18 months can use a pea-sized amount of children’s low-fluoride toothpaste and if possible should be taught not to swallow it. They should rinse with water after brushing.

To reduce the risk of tooth decay:

• Never allow your baby to fall asleep with a bottle containing milk, formula, fruit juice or sweetened liquid.
• Don’t dip a dummy in sugar or honey.
• Clean the dummy before you give it to your baby.
• Visit your dentist by about 12 months.

If you are worried about your baby’s tooth development, call Pregnancy, Birth and Baby on 1800 882 436 to talk to a maternal child health nurse.