BOH Part1

Training of basic oral health workers

Part 1 - Anatomy, physiology, common dental diseases, causes and treatment.

Anatomy

In order to be able to understand the principles of dental prevention , dental diseases and their treatment it is important to know how the human body is built up. The description of the tissues and structures is called Anatomy. We will deal only with the anatomy of the oral region. Description of tissues and

structures will be given only if relevant to dental diseases and their treatment.

BONES

The bones which are important to us, are the upper jaw or MAXILLA and lower jaw or MANDIBLE.

The jaws hold the teeth.

Thanks to its shape the mandible supports the chin and the tongue.

A drawing of the mandible is shown in fig.1

In the mandible we find 2 important openings.

One is the MANDIBULAR FORAMEN which is located at the inside of the mandible behind the last tooth.

The other one is the MENTAL FORAMEN which is located at the outside more in front.

These foramen are connected by a canal which we call the MANDIBULAR CANAL.

Figure 1. Mandible.

NERVES

A nerve is a tissue which enables us to experience signals like pain, temperature, light etc. A second function is to stimulate muscles so that we can walk, write talk, etc. An important nerve for dental treatment is the mandibular nerve.

The mandibular nerve comes from the brain and enters the mandible through the mandibular foramen. It runs through the mandibular canal. Meanwhile it gives tiny branches to the various teeth so that these teeth may feel cold and heat (for example hot tea or cold water). Half of the mandibular nerve leaves the mandible through the mental foramen to give sensitivity to the chin and

lower lip.

Just before the mandibular nerve enters the mandibular foramen a nerve which we call LINGUAL NERVE branches off. The lingual nerve runs to the tongue and the gums at the inside of the mandible, where it gives sensitivity to the gums and the tongue.

In the maxilla several tiny branches from larger nerves give sensitivity to the teeth and the gums at the inside and outside of the maxilla.


Figure 2. Mandibular nerve, Lingual nerve and Buccal nerve.	Figure 3. Anatomy of a tooth.

MUCOSA

The jaw bones and the inside of the lip, the tongue etc. are covered with a tissue which always remains moist. This tissue we call mucosa. It is the skin of the oral cavity.

THE TEETH

In the mouth there are several kinds of teeth.

Incisors. The incisors are the first teeth just behind the lips. The incisors are used for cutting off pieces of food. There are 4 incisors in the maxilla and 4 in the mandible.

Canines. The canines are the strong pointed teeth which are used for tearing off pieces of food like meat. We have 2 canines in the maxilla and 2 canines in the mandible

Premolars. The premolars are the teeth which are used for grinding food. We have 4 premolars in the mandible and 4 premolars in the maxilla.

Molars, are the large teeth which we find in the back of the mouth. Molars are large teeth with cusps and grooves which are used for grinding the food completely. We have 6 molars in the mandible and 6 molars in the maxilla.

In total we have 32 teeth. Both in the mandible and in the maxilla we find, counting to the rear starting from the middle, 2 incisors (1 central, 1 lateral) 1 canine 2 premolars (1st and 2nd) 3 molars (1st, 2nd and 3rd) The 3rd molar is also called wisdom tooth.

The anatomy of the teeth is shown in figure 3, which gives a view of a molar.

A tooth consists of a part which is visible in the mouth. This part we call CROWN. The part of the tooth which is invisible in the jawbone, we call ROOT. The crown has an outer layer of strong hard material which is called ENAMEL. The enamel covers the DENTIN which forms the root and the inner part of the crown.

Inside the dentine is an open space which is called the ROOTCANAL. The rootcanal contains the nerve and the bloodvessels which feed the tooth and give it sensitivity.

As the shape of the teeth varies, also the roots vary in shape and number. We have teeth with 1 root, 2 roots and 3 roots. Fig.4 shows the number of roots for the various teeth.

Teeth with 1 root are: Maxilla: incisors, canines, 2nd premolar. Mandible: incisors, canine, premolars

Teeth with 2 roots are: Maxilla: 1st premolar. Mandible: molars

Teeth with 3 roots: Maxilla: molars

The teeth are fixed into the jawbone by means of fibres. The fibres are fixed in the jawbone and are attached to the root by a layer which is called CEMENTUM. Fig 5 shows how the teeth are fixed into the jawbone,


Fig 4. The total number of teeth.	Fig.5 Tooth, fibres and jawbone.

The fibres and the jawbone are covered by a tissue which we call the gums. The gums surround the teeth like a collar. Gums look pink when healthy.

BABY TEETH.

Usually a baby is born without any teeth. At an average age of 6 months, the baby will develop its first teeth. These are usually

lower incisors. The first set of teeth we call deciduous or BABY TEETH. The baby set of teeth is complete at an average age of 2

1/2 years. The reason for having 2 sets of teeth, a baby set and an adult set, is that the jaws of a child are too small to hold

the adult set of teeth, while the baby needs teeth to start eating solid food, since lactation stops at the age of 2 years.

The first baby teeth fall out at the age of 6 years, to be replaced by adult teeth. The last baby tooth is lost at about 12.

Baby teeth are just like adult teeth, but they are smaller in size. There are no baby premolars.

So the baby set of teeth consists of 5 teeth per quadrant, 4 x 5 = 20 teeth.

- 2 incisors

- 1 canine

- 2 molars

Physiology

Physiology tells us how the function is of the various parts of the body which are described in the anatomy.

For dental workers the main interest is in how the oral cavity functions.

The oral cavity is the entrance into the digestive system. This system makes the food which we eat (bread, porridge etc.) of use

to the body. The first step is that this food is ground to very tiny pieces so that we can swallow it. When we have food we use

the incisors to cut off a piece, or the canines to tear off a piece. With the premolars and molars this chunk of food is ground

completely. During chewing the food is thoroughly mixed with saliva. When the food is ground enough we swallow so that it

moves to the stomach.

The first function of teeth therefore is CHEWING. A second and also very important function is that the lips and the cheek are supported by the teeth so that the face maintains its normal shape. When somebody has lost all his teeth we see how

important teeth are in maintaining proper shape of the face. This function we call: MAINTAINING SHAPE OF THE FACE.

A third function is that the teeth assist in proper speech. By pressing the tongue against the teeth some sounds are made, for

example say: tooth. If a person does not have teeth it is very difficult to understand him. His speech is a problem.

This function we call: ASSIST IN SPEAKING.

Dental diseases and their treatment

Maintaining dental health is important. However, if we fail to keep our teeth and gums healthy, dental diseases develop.

The 2 main dental diseases are called CARIES (=tooth-decay) and GINGIVITIS (=gum-disease)

Of course there are more dental diseases. Some of these will be discussed later (page...).

As almost all of our patients suffer from caries or gingivitis and related problems we will discuss these first.

CARIES

Caries is the disease which attacks the enamel and dentine of a tooth. In this process the enamel dissolves in places and a

cavity arises.

Causes

If you do not brush your teeth PLAQUE forms. Plaque forms in the grooves of a tooth, in between the teeth and on the teeth along

the gums.

After the plaque has formed, BACTERIA enter the plaque. These bacteria take the SUGAR from the food you eat and transform it into ACID.

This acid dissolves the enamel. It starts superficially everywhere that plaque is present. When the enamel

dissolves, a hole or cavity forms in the tooth.

Progress

The progress of caries can be divided into stages. The various stages are:

Plaque collects on the teeth at all places where no proper brushing is carried out.

Bacteria enter the plaque. The bacteria take the sugar from the food we eat and transform it into acid. The acid dissolves the enamel. As can be seen in fig.6, caries moves along the weakest spots which are towards the nerve.

Fig.7 shows the process reaching the dentine. As dentine is much softer than enamel, caries will spread more rapidly. The spreading will occur in all directions including towards the nerve.

As is shown in figure 8a, the caries reaches the pulp cavity where the nerve is located. The nerve gets irritated by the acid produced by the bacteria. An irritated nerve aches. At this stage one might develop a serious toothache. The tooth is now extremely sensitive to hot or cold drinks and food. In the meantime pieces of enamel might have chipped off, leaving a big hole in the tooth. This is shown in fig.8b .

If no treatment is given at this stage the nerve will not be able to withstand the irritation longer than 2 days. Then the nerve will die. This makes the toothache stop very quickly by itself, since a dead nerve cannot be irritated. When the nerve is dead, bacteria will enter the root canal and produce all kinds of waste materials. These materials usually leave the tooth through the cavity in the crown, as can be seen from fig.9. If for one reason or another this outlet gets blocked, the waste materials might leave the tooth through the opening in the root tip. Then waste materials will irritate the tissues around the root tip and an inflammation will develop there. After 3 days pus forms. This condition we call PERIAPICAL ABSCESS. A peri-apical abscess causes a severe toothache. However, the tooth is not sensitive to hot or cold drinks or food. The tooth is very painful when tapered. Fig.10 shows the relation of the root tip and the abscess.


Fig. 6 Caries in enamel.	Fig. 7 Caries in dentine.	Fig. 8a Caries reaching the nerve.

Fig. 8b Enamel has chipped	Fig.9 Waste materials leave the tooth through the cavity	Fig.10 Periapical abscess around the root tip.

Duration of process

Caries is a process which takes time to develop. Roughly we can say that it takes about 3 months from when plaque forms on the

teeth to the first signs of caries. The first sign is a change in the colour of the enamel. White spots appear on the smooth surfaces, the grooves of the teeth turn brown. It takes about 6 months from when the plaque forms to the presence of a cavity. It takes between 2 months and 2 years for decay to reach the nerve. It takes from 1 week up to several years from the time the nerve dies to the development of a periapical abscess.

Signs and symptoms

sensitivity to cold drinks, later on sensitivity to hot food as well

brown lines in the grooves of a tooth

soft brown spots in the grooves

holes in which a dental probe sticks or can penetrate

toothache especially when going to sleep

pain when the tooth is tapped with an instrument

patient avoids using the affected teeth

Treatment of caries

Whatever the stage reached, oral hygiene instruction should be given. However, the type of treatment given for caries depends on

the stage reached.

-if caries has developed but is not yet affecting the nerve (stage b + c) a filling can be made.

-if the nerve is involved, treatment depends on how serious the decay is. The following can be given:

-a filling

-rootcanal treatment

-an extraction

-If the nerve is dead we can extract the tooth as is done in most cases or we can give root canal treatment.

GINGIVITIS

Gingivitis is the disease, which affects the gums and supporting tissues of a tooth.

Causes.

Gingivitis starts with dirt on the teeth. If you do not brush your teeth, a layer of dirt will arise. This layer is called PLAQUE. Plaque grows in the grooves of a tooth, in between the teeth and on the teeth along the gums. For gingivitis, only the plaque along the gums is important.

When plaque collects on the teeth along the gums, bacteria start entering the plaque. These bacteria live on substances from food,

and, in due course, produce waste materials. These waste materials irritate the gums. If a tissue gets irritated you get HYPERAEMIA, causing a redness of the gums. When touching a hyperaemic area, for example with a toothbrush, this area bleeds very easily. This is the first sign of gingivitis. BLEEDING GUMS.

Progress

If nothing changes in the oral hygiene at this stage, the irritation will persist and will penetrate deeper. Waste materials will enter the gap between the root and the bone and they will destroy the fibrous tissue which connects the root to the bone. If this process continues eventually so many fibres will get damaged that the tooth will become mobile and in the end the tooth will fall out. It is therefore important to realise that fibres once lost will never be replaced

Symptoms of gingivitis

-gums which bleed on touching with brush or dental probe

-sore gums which may look swollen or red

-teeth or tooth more mobile than normal

-bad smell

CALCULUS

A complicating factor in gingivitis is the formation of calculus. CALCULUS is the hard, stony layer which will grow on the teeth if

specific conditions are present.

Causes

If we do not brush our teeth, plaque forms. In the saliva produced by the major salivary glands we find chemical components

which we call CALCIUM SALTS. These calcium salts are dissolved in the saliva and enter the mouth together with the saliva. The

calcium salts enter the plaque and start to harden it. This process we call calcification of the plaque. The calcified plaque

we call CALCULUS. Calculus may arise anywhere in the mouth, but will grow mainly where the salivary glands eject the saliva.

which is on the inner side of the lower incisors and on the outside of the upper molars.

Progress

Calculus is a substance with a rough surface. Plaque attaches easily to rough surfaces. Once calculus is present it will grow

rapidly. The plaque on calculus will irritate the gums. calculus on the teeth, therefore will make the existing gingivitis much

worse. Gingivitis and calculus will lead to a loss of fibres and eventually to a loss of the tooth.

Treatment of gingivitis and calculus

The cause of gingivitis and calculus is the PLAQUE. Treatment of gingivitis is therefore aimed at PLAQUE REMOVAL. The patient has

to be instructed on proper oral hygiene. He should know how to brush the gums and teeth. In the beginning gingivitis will be

cured completely when plaque is removed thoroughly and regularly. The patient treats the gingivitis himself by good oral hygiene.

Calculus is so hard a layer that it will not be removed by brushing. A dental worker has to scrape it off with an

instrument. This scraping we call SCALING. Oral hygiene instruction and scaling will cure the gingivitis. However, the fibres which are lost will not come back. Prevention of gingivitis and calculus is therefore most important. Prevention is better than cure!