During pregnancy, women’s bodies undergo complex physiological changes that can adversely affect oral health. For this reason, health professionals need to ensure that the pregnant women they serve receive needed oral health care.
Benefits of tooth brushing and prevent gum bleeding
We all must have noticed a soft sticky layer forming on our teeth everyday. This layer is called PLAQUE. It is mainly formed of food debris and bacteria. Brushing teeth removes plaque and gives us clean teeth, gums and a fresh breath. For healthy teeth and gums it is mandatory to have good oral hygiene and for that brushing should be perfect.
Most dental problems are because of improper brushing technique. One may be brushing 3to4 times a day, but if brushing technique is not proper, there will be food lodgment in between the teeth resulting in oral hygiene. That is why learning proper brushing technique is very important.
why gums bleeding during washing?
perfectly healthy gums should not bleed when we brush our teeth, says Dr. Mark Gustavson, a partner at Affiliated Dentists in Madison, Wisconsin. If they do, you need to start examining your oral hygiene habits, and if things don’t improve quickly, it’s time to book an appointment with your dentist.
Healthy gums should not bleed when you brush your teeth. When a patient’s oral hygiene is not as good as it should be, the build-up of plaque and tartar inflames the tissue. That means that when you go to brush it or remove the tartar, then your gums will bleed.
If the plaque is consistently removed with good flossing and brushing habits and the patient regularly sees his dentist, his gum tissue should not bleed.
If after regular cleaning and perfect oral hygiene bleeding still exists, then the concern becomes detecting the presence of periodontal disease. If periodontal disease is 
present, then periodontal therapy would need to be completed.
present, then periodontal therapy would need to be completed.
That could be through scaling and root cleaning, the use of antibiotics in the pockets of the gum tissue around the teeth, and more frequent periodontal maintenance visits.
With severe periodontal disease, sometimes bone grafting can be completed to regrow some bone. But in worst cases, the only option is sometimes removal of the teeth, and then hopefully replacement with a dental implant.
It is always a good idea to see your dentist if you notice any of the following problems:
- Bleeding of the gums on a regular basis, whenever you brush or floss your teeth.
- Teeth that are loose when they should not be.
- Persistent bad breath that does not go away despite proper oral hygiene habits.
- Gums that appear unduly red, swollen or tender.
Discoloration of the gums.
If your gums appear to be pulling away from your mouth or if there is pus when you brush your teeth, see your dentist immediately. Gum disease can be stopped with early intervention. Don’t wait until it’s too late.
The information in the article is not intended to substitute for the medical expertise and advice of your healthcare provider. We encourage you to discuss any decisions about treatment or care with an appropriate healthcare provider.
The information in the article is not intended to substitute for the medical expertise and advice of your healthcare provider. We encourage you to discuss any decisions about treatment or care with an appropriate healthcare provider.
7 Reasons to Brush Your Teeth Twice a Day
1) Fluoride
Most toothpaste brands include fluoride as one of the main ingredients in toothpaste. Fluoride is instrumental in preventing cavities from forming. When you brush before going to bed it’s a first line of defense against the formation of cavities while you 
sleep.
sleep.
Why? It works because the fluoride creates a layer of protection around your teeth. When you wake in the morning, one of the first things you need to do is brush your teeth in order to “touch up” that layer of protection and help protect your teeth throughout the day.
Make sure the brand of toothpaste you use provides adequate fluoride protection to safeguard your pearly whites against cavities and other signs of decay.
2) Bacteria
It’s important to brush your teeth two times a day in order to remove harmful bacteria from building up in your mouth. The bacteria, if left unchecked for a full 24-hour period will have plenty of time to do more damage to the enamel of your teeth.
A 12-hour window may not seem like a huge reduction in the amount of time for 
damage to be done but it literally cuts the amount of time in half. When you combine that with other efforts to eliminate the buildup of bacteria inside the mouth like
damage to be done but it literally cuts the amount of time in half. When you combine that with other efforts to eliminate the buildup of bacteria inside the mouth like
flossing and using an antiseptic mouthwash or rinse the results are even more profound.
In addition to brushing your teeth twice a day, consider an antibacterial mouthwash. This will not only help protect your teeth and gums from harmful bacteria but will also remove the bacteria that leads to bad breath as well.
3) Saliva Production
While you are sleeping at night you produce less saliva than you do during the day. Saliva actually works inside your mouth as an added layer of defense against bacteria 
and plaque that leads to cavities. Brushing immediately before going to bed will remove many of the little particles of food and a lot of the bacteria inside your mouth that is just looking for a way to degrade your dental health.
and plaque that leads to cavities. Brushing immediately before going to bed will remove many of the little particles of food and a lot of the bacteria inside your mouth that is just looking for a way to degrade your dental health.
Overnight the bacteria that remains behind creates acid (as it breaks down) inside your mouth. That acid can damage teeth and lead to cavities. Brushing first thing in the morning will reduce that risk as well.
If you are taking medications that dry your mouth it is in your best interest to start a habit of chewing sugar-free gum (the chewing action actually works to increase salivation) and drink plenty of water to keep your mouth hydrated.
4) Prevent Tartar Buildup
Tartar can build up above or below the gums. Unfortunately, it’s something that you 
can’t get rid of on your own. The only way to remove tartar once it gets its foot in the door is to pay a visit to your local dentist who will actually perform a thorough cleaning and literally scrape the tartar away. Failing to remove tartar buildup can lead to gum disease or even periodontal disease.
can’t get rid of on your own. The only way to remove tartar once it gets its foot in the door is to pay a visit to your local dentist who will actually perform a thorough cleaning and literally scrape the tartar away. Failing to remove tartar buildup can lead to gum disease or even periodontal disease.
This is one thing where prevention is definitely the best cure. Tartar buildup can be prevented with regular professional cleanings by your dentist, twice daily brushing with tartar control toothpaste, and regular use of mouthwashes or rinses that are designed to assist in the fight against tartar and plaque.
People who have diabetes, smoke, or who frequently suffer from dry mouth are at greater risk for heavy tartar buildup and should take extra precautions.
5) Protect Gums
Brushing your teeth does more than just remove bacteria from the teeth, keep your breath minty fresh, and create sparkling white teeth. Good dental health is about so much more than just your teeth. Your gums are an important part of the oral hygiene and dental health tradition. If you aren’t taking good care of them, your teeth will soon fall into their own states of emergency.
Poor gum health can lead to periodontal disease, tooth sensitivity, tooth shifting, 
abscessed teeth, and even tooth loss. Brushing your teeth twice daily combined with flossing, antiseptic mouth rinses, and regular dental checkups and cleaning will go a long way towards overall good gum health.
abscessed teeth, and even tooth loss. Brushing your teeth twice daily combined with flossing, antiseptic mouth rinses, and regular dental checkups and cleaning will go a long way towards overall good gum health.
Treatments for gum disease once it sets in include plaque removal in the dentist office, prescription mouth rinses to kill bacteria, and potential surgery for more severe cases.
6) Fresh Breath
No one wants to be the person in a crowded elevator with a not so small case of halitosis. Companies everywhere are making a fortune off products that are designed to make breath smell minty fresh. Fresh breath is associated with good dental health and will keep people from shying away from you in a crowd.
Mints, sprays, and gum have their uses but nothing is as effective at controlling bad breath as regular brushing of the teeth. Other things you can do that will help include using a tongue scraper as part of your daily oral care routine. This will remove odor causing bacteria from the tongue. Some dentists recommend brushing the tongue with your toothbrush as well as the teeth for cases of severe halitosis.
7) Improved Overall Health
There is more than a healthy smile on the line when people fail to pay proper attention to good dental health. The health of your smile reveals a good deal about your overall health and should not be overlooked.
Gum disease isn’t limited to your mouth. The bacteria from gum disease can get into your bloodstream leaving the entire body vulnerable. Some of the illnesses and diseases that can be linked to poor oral health include: cardiovascular disease, 
diabetes, osteoporosis, and premature or low birth weight babies.
diabetes, osteoporosis, and premature or low birth weight babies.
Brushing your teeth twice a day can greatly decrease the odds of developing gum disease. As a result the risks of these other diseases due to the gum disease will decrease as well. Can you imagine the difference it will make when brushing is combined with routine dental checkups and cleanings, flossing, and using an antiseptic mouth rinse?
always remember healthy starts with a healthy tooth.
Remember to replace your toothbrush every three to four months. Researchers have established that thousands of microbes grow on toothbrush bristles and handles. Most are harmless, but others can cause cold and flu viruses, the herpes virus that causes cold sores, and bacteria that can cause periodontal infections.
Tooth Brushing
Brushing your teeth is one of the most effective ways of removing plaque from the exposed surfaces of your teeth and to make your teeth healthy.
Why Healthy Teeth Are Important?
Taking care of your teeth helps prevent plaque , which is a clear film of bacteria that sticks to your teeth.After you eat, bacteria go crazy over the sugar on your 
teeth, like ants at a picnic. The bacteria break it down into acids that eat away tooth enamel, causing holes called cavities. Plaque also causes gingivitis , which is gum disease that can make your gums red, swollen, and sore. Your gums are those soft pink tissues in your mouth that hold your teeth in place.If you don't take care of your teeth, cavities and unhealthy gums will make your mouth very, very sore. Eating meals will be difficult. And you won't feel like smiling so much.
teeth, like ants at a picnic. The bacteria break it down into acids that eat away tooth enamel, causing holes called cavities. Plaque also causes gingivitis , which is gum disease that can make your gums red, swollen, and sore. Your gums are those soft pink tissues in your mouth that hold your teeth in place.If you don't take care of your teeth, cavities and unhealthy gums will make your mouth very, very sore. Eating meals will be difficult. And you won't feel like smiling so much.
If teeth are not brushed correctly and frequently, it could lead to the calcification of saliva minerals, forming tartar. Poor dental health has been associated with heart disease and shortened life expectancy.
In the past:
3000 BC ancient Egyptians constructed crude toothbrushes from twigs and leaves to clean their teeth. Similarly, other cultures such as the Greeks, Romans, and Indians cleaned their teeth with twigs. Some would fray one end of the twig so that it could penetrate between the teeth more effectively.
Long ago, as people got older, their teeth would rot away and be very painful. To get rid of a toothache, they had their teeth pulled out. Finally people learned that cleaning their teeth was important, but they didn't have toothpaste right away. While you're swishing that minty-fresh paste around your mouth, think about what people used long ago to clean teeth:
- ground-up chalk or charcoal
- lemon juice
- ashes (you know, the stuff that's left over after a fire)
- tobacco and honey mixed together
It was only about 100 years ago that someone finally created a minty cream to clean teeth. Not long after that, the toothpaste tube was invented, so people could squeeze the paste right onto the toothbrush! Tooth brushing became popular during World War II. The U.S. Army gave brushes and toothpaste to all soldiers, and they learned to brush twice a day. Back then, toothpaste tubes were made of metal; today they're made of soft plastic and are much easier to squeeze!
Today there are plenty of toothpaste and brushes choices: lots of colors and flavors to choose from, and some are made just for kids. People with great-looking teeth advertise toothpaste on TV commercials and in magazines. When you're choosing a toothpaste, make sure it contains fluoride . Fluoride makes your teeth strong and protects them from cavities.
How to brush your teeth?
1- prepare your tooth brush:
After flossing, moisten your toothbrush with water and apply a thin strip of toothpaste. Try to choose one that contains fluoride.
2- start in the back:
Start with your upper molars (back teeth) on your left side and work in a clockwise direction.
Point the bristles toward the gumline, in a 45-degree angle. Use a short circular motion for approximately 20 seconds.
3-Roll Away:
After 20 seconds, roll the brush head away from the gumline, so the bristles sweep the surface of the tooth, removing the food and plaque.
4-Work in a Clockwise Direction:
Continue working in a clockwise direction, ending with the lower molars on your left side. Repeat step two and three for the inside surface of the upper and lower molars.
5-Brushing the Back Surface of the Upper Front Teeth:
Brush the lingual (back) surface of the upper-front teeth by using the tip of the toothbrush head. Direct the bristles toward the gumline, and use a flicking motion down the surface of the tooth. Do this 2 to 3 times.
6-Brushing the Back of the Lower Front Teeth:
Point the bristles of the tip of the toothbrush toward the gumline. Flick the bristles up, away from the gumline in a sweeping motion. Do this 2 to 3 times.
7-Brush the Biting Surface:
Brush the biting surface of the upper and lower premolars and molars, using a circular motion.
8-Brush Your Tongue and the Inside of Your Cheeks:
Using a gentle circular motion, brush your tongue for 30 seconds and the inside of your cheeks for 30 seconds.
9-Finish Up With a Rinse:
Finish by rinsing with either water or your choice of mouthwash. Don't forget to smile!
Remember to replace your toothbrush every three to four months. Researchers have established that thousands of microbes grow on toothbrush bristles and handles. Most are harmless, but others can cause cold and flu viruses, the herpes virus that causes cold sores, and bacteria that can cause periodontal infections.
Physiology of teeth
Mouth Divisions:
The mouth can be divided into sections:
• Arches (there are 2 arches present)- an arch will divide the mouth into top and
bottom
• Quadrants (there are 4 quadrants present)- a quadrant divides an arch into right
and left
These divisions refer to both the primary and permanent dentitions.
Maxillary Arch
• This is the top arch or jaw.
• The maxillary arch contains 16 permanent teeth.
• The maxillary arch contains 10 primary teeth.
• The maxillary arch contains 2 quadrants.
Mandibular Arch:
• Arches (there are 2 arches present)- an arch will divide the mouth into top and
bottom
• Quadrants (there are 4 quadrants present)- a quadrant divides an arch into right
and left
These divisions refer to both the primary and permanent dentitions.
Maxillary Arch
• This is the top arch or jaw.
• The maxillary arch contains 16 permanent teeth.
• The maxillary arch contains 10 primary teeth.
• The maxillary arch contains 2 quadrants.
Mandibular Arch:
• This is the bottom arch or jaw.
• The mandibular arch contains 16 permanent teeth.
• The mandibular arch contains 10 primary teeth.
• The mandibular arch contains 2 quadrants.
The mouth will have 4 Quadrants:
• The mandibular arch contains 16 permanent teeth.
• The mandibular arch contains 10 primary teeth.
• The mandibular arch contains 2 quadrants.
The mouth will have 4 Quadrants:
• MX right (quadrant 1) MX left (quadrant 2)
• MD right (quadrant 3) MD left (quadrant 4)
divided by a midline (the midline refers to an imaginary line that divides the mouth into right and left halves)
Names of Teeth:
If you look in your mouth, you will notice that the teeth in the front of the mouth
look different than the teeth in the back of the mouth. This is because there are
different types of teeth in the mouth.
1 -Anterior teeth
• These are the teeth in the front of the mouth
Names of the anterior teeth:
central incisors
lateral incisors
canines
2 - Posterior teeth
• These are the teeth in the back of the mouth
Names of the posterior teeth:
premolars
molars
If you look in your mouth, you will notice that the teeth in the front of the mouth
look different than the teeth in the back of the mouth. This is because there are
different types of teeth in the mouth.
1 -Anterior teeth
• These are the teeth in the front of the mouth
Names of the anterior teeth:
central incisors
lateral incisors
canines
2 - Posterior teeth
• These are the teeth in the back of the mouth
Names of the posterior teeth:
premolars
molars
Tooth Numbers:
tooth numbers help the patient and the dentist to diagnose the case correctly.
• Teeth are given numbers as a way to identify them
Permanent dentition- Maxillary or top arch contains tooth numbers 1 - 16
Mandibular arch contains tooth numbers 17 – 32
Primary dentition- Maxillary arch contains tooth letters A - J
Mandibular arch contains tooth letters K - T
Permanent Tooth Numbers:
• Teeth are given numbers as a way to identify them
Permanent dentition- Maxillary or top arch contains tooth numbers 1 - 16
Mandibular arch contains tooth numbers 17 – 32
Primary dentition- Maxillary arch contains tooth letters A - J
Mandibular arch contains tooth letters K - T
Permanent Tooth Numbers:
Maxillary Tooth Numbers:
• Tooth #1 MX Right 3rd Molar
• Tooth #2 MX Right 2nd Molar
• Tooth #3 MX Right 1st Molar
• Tooth #4 MX Right 2nd Premolar
• Tooth #5 MX Right 1st Premolar
• Tooth #6 MX Right Canine
• Tooth #7 MX Right Lateral Incisor
• Tooth #8 MX Right Central Incisor
• Tooth #9 MX Left Central Incisor
• Tooth #10 MX Left Lateral Incisor
• Tooth #11 MX Left Canine
• Tooth #12 MX Left 1st Premolar
• Tooth #13 MX Left 2nd Premolar
• Tooth #14 MX Left 1st Molar
• Tooth #15 MX Left 2nd Molar
• Tooth #16 MX Left 3rd Molar
• Tooth #2 MX Right 2nd Molar
• Tooth #3 MX Right 1st Molar
• Tooth #4 MX Right 2nd Premolar
• Tooth #5 MX Right 1st Premolar
• Tooth #6 MX Right Canine
• Tooth #7 MX Right Lateral Incisor
• Tooth #8 MX Right Central Incisor
• Tooth #9 MX Left Central Incisor
• Tooth #10 MX Left Lateral Incisor
• Tooth #11 MX Left Canine
• Tooth #12 MX Left 1st Premolar
• Tooth #13 MX Left 2nd Premolar
• Tooth #14 MX Left 1st Molar
• Tooth #15 MX Left 2nd Molar
• Tooth #16 MX Left 3rd Molar
Mandibular Tooth Numbers:
• Tooth #17 MD Left 3rd Molar
• Tooth #18 MD Left 2nd Molar
• Tooth #19 MD Left 1st Molar
• Tooth #20 MD Left 2nd Premolar
• Tooth #21 MD Left 1st Premolar
• Tooth #22 MD Left Canine
• Tooth #23 MD Left Lateral Incisor
• Tooth #24 MD Left Central Incisor
• Tooth #25 MD Right Central Incisor
• Tooth #26 MD Right Lateral Incisor
• Tooth #27 MD Right Canine
• Tooth #28 MD Right 1st Premolar
• Tooth #29 MD Right 2nd Premolar
• Tooth #30 MD Right 1st Molar
• Tooth #31 MD Right 2nd Molar
• Tooth #32 MD Right 3rd Molar
• Tooth #17 MD Left 3rd Molar
• Tooth #18 MD Left 2nd Molar
• Tooth #19 MD Left 1st Molar
• Tooth #20 MD Left 2nd Premolar
• Tooth #21 MD Left 1st Premolar
• Tooth #22 MD Left Canine
• Tooth #23 MD Left Lateral Incisor
• Tooth #24 MD Left Central Incisor
• Tooth #25 MD Right Central Incisor
• Tooth #26 MD Right Lateral Incisor
• Tooth #27 MD Right Canine
• Tooth #28 MD Right 1st Premolar
• Tooth #29 MD Right 2nd Premolar
• Tooth #30 MD Right 1st Molar
• Tooth #31 MD Right 2nd Molar
• Tooth #32 MD Right 3rd Molar
Primary Tooth Letters:
Maxillary Tooth Letters
• Letter A MX Right Primary 2nd Molar
• Letter B MX Right Primary 1st Molar
• Letter C MX Right Primary Canine
• Letter D MX Right Primary Lateral Incisor
• Letter E MX Right Primary Central Incisor
• Letter F MX Left Primary Central Incisor
• Letter G MX Left Primary Lateral Incisor
• Letter H MX Left Primary Canine
• Letter I MX Left Primary 1st Molar
• Letter J MX Left Primary 2nd Molar
• Letter K MD Left Primary 2nd Molar
• Letter L MD Left Primary 1st Molar
• Letter M MD Left Primary Canine
• Letter N MD Left Primary Lateral Incisor
• Letter O MD Left Primary Central Incisor
• Letter P MD Right Primary Central Incisor
• Letter Q MD Right Primary Lateral Incisor
• Letter R MD Right Primary Canine
• Letter S MD Right Primary 1st Molar
• Letter T MD Right Primary 2nd Molar
• Letter A MX Right Primary 2nd Molar
• Letter B MX Right Primary 1st Molar
• Letter C MX Right Primary Canine
• Letter D MX Right Primary Lateral Incisor
• Letter E MX Right Primary Central Incisor
• Letter F MX Left Primary Central Incisor
• Letter G MX Left Primary Lateral Incisor
• Letter H MX Left Primary Canine
• Letter I MX Left Primary 1st Molar
• Letter J MX Left Primary 2nd Molar
• Letter K MD Left Primary 2nd Molar
• Letter L MD Left Primary 1st Molar
• Letter M MD Left Primary Canine
• Letter N MD Left Primary Lateral Incisor
• Letter O MD Left Primary Central Incisor
• Letter P MD Right Primary Central Incisor
• Letter Q MD Right Primary Lateral Incisor
• Letter R MD Right Primary Canine
• Letter S MD Right Primary 1st Molar
• Letter T MD Right Primary 2nd Molar
Tooth Surfaces:
• the crown or portion of the tooth that you can see when the mouth is open, are
divided into surfaces
• these surfaces are named according to the direction in which they face
Mesial
• this surface is closest to the midline
Distal
• this surface is farthest from the midline
Facial
• designates the outer surface of an anterior tooth
• is also called Labial
Buccal
• designates the outer surface of a posterior tooth
Lingual
• the surface of the tooth that is towards the tongue or roof of the mouth
• Palatal- term used for maxillary teeth
Occlusal
• biting or occluding surfaces of posterior teeth
Incisal
• “biting” surface of anterior teeth
• the crown or portion of the tooth that you can see when the mouth is open, are
divided into surfaces
• these surfaces are named according to the direction in which they face
Mesial
• this surface is closest to the midline
Distal
• this surface is farthest from the midline
Facial
• designates the outer surface of an anterior tooth
• is also called Labial
Buccal
• designates the outer surface of a posterior tooth
Lingual
• the surface of the tooth that is towards the tongue or roof of the mouth
• Palatal- term used for maxillary teeth
Occlusal
• biting or occluding surfaces of posterior teeth
Incisal
• “biting” surface of anterior teeth
kinds of Teeth “permanent teeth”
The teeth have the most important role and the hardest structure in human's jaws and many other spinescent animals. The main function of the teeth is cutting and grinding the food pieces. Further more, they help us in speaking properly.
Two kinds of teeth grow during every human's life cycle:
1-primary teeth.
2-permanent teeth .
The number of primary teeth is 20 which are distributed equally in the two jaws.
After a while, the 32 permanent teeth are replaced the primary ones gradually.
As the primary teeth are the base of the permanent teeth, having good oral hygiene is necessary.
Around the 8th week after conception, oval-shaped tooth buds start to form and harden in the embryo's mouth. Although the baby teeth aren't visible when a child is born, both the primary and permanent teeth are partially formed below the gums. The tooth crown develops first and after it is fully grown, the root begins to develop.
Then between about six months and 1 year old, the deciduous teeth begin to push through the gums. This process is called baby teeth eruption . A child gets his first complete set of primary teeth by the age of 3. The baby teeth chart shows the average age that each primary tooth is expected to erupt. But not all baby teeth follow these rules. Some infants may have their first primary tooth (usually one of the bottom middle teeth) erupted as early as 3 months.Others may reach their first birthday or more without getting their first deciduous tooth. If there is no sign of teething by this age you should ask for a pediatrician's advise. That kind of late development of primary teeth is more common in premature babies. In some rare cases (1 every 2.000) infants are born with one or more teeth (called natal teeth) or may have teeth emerge within the first month (called neonatal teeth). A dentist should evaluate the teeth's condition, as they could be loose, interfere with feeding or irritate the baby's tongue.
2- permanent (adult) teeth:
Adult teeth or permanent teeth replace the primary teeth. They aid in digestion, speech and general appearance. There are 32 permanent teeth, with the main difference from primary teeth is that there are 4 premolars and 6 molars in each arch. Permanent teeth begin erupting at 6yrs of age and end at 21yrs of age. Some people may not have some if not all their 3rd molars due to evolutionary changes leading to the lack of development of these teeth. 3rd molars may not erupt due to becoming embedded in jaw. The tooth consists of a crown and root, and the tooth is composed of different materials that aid in strengthening, preserving and maintaining its function.
Adult teeth begin to replace the front milk teeth from the age of about six. For the next six to eight years there is a gradual replacement of milk teeth by adult teeth. This stage is called mixed dentition, as both milk and adult teeth will be from the mouth at the same time. By the age of about 12-14 all adult teeth should have appeared using the exception of wisdom teeth (third molars). At this stage the mouth will contain twenty-eight teeth. These teeth have to last for life as we only get one set.
The permanent tooth begins to grow under the baby tooth.
- The root of the baby tooth begins to dissolve (reabsorb), and the baby tooth becomes loose.
- It takes three and a half years for the baby tooth to lose its roots, and for it to be replaced by the permanent tooth.
- The crown of the permanent tooth is the first part of the tooth to develop.
- It grows into the space left by the root of the baby tooth.
- The root of the permanent tooth then continues to form.
- When the crown erupts, it is covered by a cuticle or covering that protects the enamel. The cuticle is slowly worn away by chewing and tooth brushing.
During 7 years, 20 baby teeth are lost and are replaced by 28 permanent teeth.
The mixed dentition stage is the period when some baby and permanent teeth are visible in the mouth at the same time. 
In addition, 4 wisdom teeth will erupt by the age of 21 years, taking the total number of permanent teeth to 32.
The eruption of the 32 permanent teeth starts at age 6, and is completed between the ages of 20 and 23, after the wisdom teeth (3rd molars) have arrived.
The final four adult teeth should come through during late teens totaling 32 adult teeth. The descriptions below explain the functions of each of the teeth. To view a model showing all the milk and adult teeth erupting, take a look at the timeline showing the lifetime of teeth.
third molars often are not needed for chewing and are difficult to keep clean. Your dentist may recommend their removal to prevent potential complications when third molars are erupted partially or are impacted. The chart and photograph identify the names of the permanent teeth and provide the approximate ages at which you can expect the teeth to erupt. Heredity and other factors may influence the approximate ages at which children’s primary teeth shed and their permanent teeth emerge. Thorough brushing and flossing help remove food particles and plaque (a sticky film of bacteria) from the smooth surfaces of teeth. But toothbrush bristles cannot reach into the pits and fissures (depressions and grooves) of the chewing surfaces to remove food and plaque. Dental sealants protect these vulnerable areas by sealing out debris and plaque bacteria. A sealant is a plastic material that usually is applied to the
chewing surfaces of the back teeth—premolars and molars—where decay occurs most often. The plastic resin bonds into the pits and fissures of the chewing surfaces of back teeth. The sealant acts as a barrier, protecting enamel from plaque and acids.
chewing surfaces of the back teeth—premolars and molars—where decay occurs most often. The plastic resin bonds into the pits and fissures of the chewing surfaces of back teeth. The sealant acts as a barrier, protecting enamel from plaque and acids.
Eruption Sequence of Permanent Dentition:
- Central incisors= 6-8 yrs
- Lateral incisors= 6.5-8.5yrs
- Canine = 9-13 yrs
- 1st Premolars= 9.5-11.5yrs
- 2nd Premolars= 10-13yrs
- 1st Molars =5.5-7yrs
- 2nd Molars= 11-13yrs
- 3rd Molars= 17-21yrs
The 32 fit into the jaw space for 20 baby teeth
The bones of the face grow during the period of tooth development.
- The jawbone normally grows in size to accommodate the extra teeth.
- The jaws grow at a faster rate than the rest of the face, and eventually measure up to 1/3 of the size of the face. This is a dramatic increase from the proportion at birth.
- If the jaws do not grow sufficiently, crowding or impacted teeth will result.
Permanent incisors: These are the front teeth, and there are 8 of them altogether (four at the top and four at the bottom). They are usually the first permanent teeth to come through, and are good for cutting into food (for example biting into an apple). You can tell which are the incisors by their flat edge at the top, and because they each have only one root.
Permanent canines: These front teeth are also known as 'eye teeth', and are more pointed in shape than the incisors, but like the incisors they each have a single root. There are 4 altogether, and in animals such as dogs and cats the canines are much longer, and are used for tearing off chunks of food. In humans they are smaller in size, and are good for cutting into food similar to incisors.
Premolars: These are the new, adult back teeth which replace the first and second deciduous molars. There are eight altogether, four first premolars and four second ones. Deciduous teeth don't have premolars as back teeth, just molars.
Permanent molars: These are the larger back teeth, which are good for crushing food into smaller pieces before being swallowed. This is known as chewing. Molars usually have more than one root each, and have irregular, or 'bumpy' surfaces with grooves called 'fissures'. There are first, second and third permanent molars, which come through in that order.
First permanent molars: The four first permanent molars are similar in size to the second molars and come through at around age 6 to 8 years.
Second permanent molars: The four second permanent molars are similar in size to the first permanent molars and come through at around age 12 years.
Third permanent molars: These are the very last of the adult teeth to appear between age 18 and 21 years, and are also called 'wisdom teeth'. There are four, and they come through at the very back and sometimes cause problems if there isn't enough room for them.
Kinds of teeth “primary teeth or milky teeth ”
The teeth have the most important role and the hardest structure in human's jaws and many other spinescent animals. The main function of the teeth is cutting and grinding the food pieces. Further more, they help us in speaking properly.
Two kinds of teeth grow during every human's life cycle:
1-primary teeth.
2-permanent teeth .
The number of primary teeth is 20 which are distributed equally in the two jaws.
After a while, the 32 permanent teeth are replaced the primary ones gradually.
As the primary teeth are the base of the permanent teeth, having good oral hygiene is necessary.
Around the 8th week after conception, oval-shaped tooth buds start to form and harden in the embryo's mouth. Although the baby teeth aren't visible when a child is born, both the primary and permanent teeth are partially formed below the gums. The tooth crown develops first and after it is fully grown, the root begins to develop.
Then between about six months and 1 year old, the deciduous teeth begin to push through the gums. This process is called baby teeth eruption . A child gets his first complete set of primary teeth by the age of 3. The baby teeth chart shows the average age that each primary tooth is expected to erupt. But not all baby teeth follow these rules. Some infants may have their first primary tooth (usually one of the bottom middle teeth) erupted as early as 3 months.Others may reach their first birthday or more without getting their first deciduous tooth. If there is no sign of teething by this age you should ask for a pediatrician's advise. That kind of late development of primary teeth is more common in premature babies. In some rare cases (1 every 2.000) infants are born with one or more teeth (called natal teeth) or may have teeth emerge within the first month (called neonatal teeth). A dentist should evaluate the teeth's condition, as they could be loose, interfere with feeding or irritate the baby's tongue.
Then between about six months and 1 year old, the deciduous teeth begin to push through the gums. This process is called baby teeth eruption . A child gets his first complete set of primary teeth by the age of 3. The baby teeth chart shows the average age that each primary tooth is expected to erupt. But not all baby teeth follow these rules. Some infants may have their first primary tooth (usually one of the bottom middle teeth) erupted as early as 3 months.Others may reach their first birthday or more without getting their first deciduous tooth. If there is no sign of teething by this age you should ask for a pediatrician's advise. That kind of late development of primary teeth is more common in premature babies. In some rare cases (1 every 2.000) infants are born with one or more teeth (called natal teeth) or may have teeth emerge within the first month (called neonatal teeth). A dentist should evaluate the teeth's condition, as they could be loose, interfere with feeding or irritate the baby's tongue.
1-primary teeth (baby or Milky teeth):
The first teeth which are shed and replaced by permanent teeth.the first teeth begin to break through the gums at about 6 months of age. Usually, the first two teeth to erupt are the two bottom central incisors (the two bottom front teeth). Next, the top four front teeth emerge. After that, other teeth slowly begin to fill in, usually in pairs - one each side of the upper or lower jaw - until all 20 teeth (10 in the upper jaw and 10 in the lower jaw) have come in by the time the child is 2 ½ to 3 years old. The complete set of primary teeth is in the mouth from the age of 2 ½ to 3 years of age to 6 to 7 years of age.
Other primary tooth eruption facts:
- A general rule of thumb is that for every 6 months of life, approximately 4 teeth will erupt.
- Girls generally precede boys in tooth eruption
- Lower teeth usually erupt before upper teeth.
- Teeth in both jaws usually erupt in pairs ? one on the right and one on the left
- Primary teeth are smaller in size and whiter in color than the permanent teeth that will follow
- By the time a child is 2 to 3 years of age, all primary teeth should have erupted
Shortly after age 4, the jaw and facial bones of the child begin to grow, creating spaces between the primary teeth. This is a perfectly natural growth process that provides the necessary space for the larger permanent teeth to emerge. Between the ages of 6 and 12, a mixture of both primary teeth and permanent teeth reside in the mouth.
When tooth falls out
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When tooth emerges
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Upper Teeth
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6 to 7 years
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8 to 12 months
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Central incisor
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7 to 8 years
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9 to 13 months
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Lateral incisor
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10 to 12 years
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16 to 22 months
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Canine (cuspid)
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9 to 11 years
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13 to 19 months
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First molar
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10 to 12 years
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25 to 33 months
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Second molar
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Lower Teeth
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10 to 12 years
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23 to 31 months
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Second molar
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9 to 11 years
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14 to 18 months
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First molar
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9 to 12 years
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17 to 23 months
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Canine (cuspid)
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7 to 8 years
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10 to 16 months
|
Lateral incisor
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6 to 7 years
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6 to 10 months
|
Central incisor
|
The table shows when the primary teeth emerges.
Tooth Anatomy” part 3 ”structure supported tooth
Gingiva:
is tough connective tissue which lines the base of the teeth, holding them in place 
and protecting the jaw and teeth roots from infections. Known informally as the gums, the gingiva are a very important part of the oral anatomy, and caring for them is critical to maintaining oral health. Problems with the gingiva can be identified during routine oral examinations, or noted by patients who experience changes in their mouths.
and protecting the jaw and teeth roots from infections. Known informally as the gums, the gingiva are a very important part of the oral anatomy, and caring for them is critical to maintaining oral health. Problems with the gingiva can be identified during routine oral examinations, or noted by patients who experience changes in their mouths.
connective tissue has a strong fibrous underlayer, covered in a layer of mucous membranes. The gingiva are very tough, designed to resist trauma from chewing and hard foods which enter the mouth. The base of this tissue is firmly anchored to the bone, while the upper portion is free, allowing the gingiva to run between the teeth to help stabilize them and keep them in place. In addition to anchoring the teeth, the gingiva also create a seal which prevents bacteria, plaque, and other foreign material from entering the roots of the teeth, where it could cause trauma or infection.
When a patient's gingiva become chronically inflamed, the condition is known as 
gingivitis. Classic symptoms of gingivitis can include changes in the color of the gingiva, along with swelling and bleeding. Patients may find that their gums are very tender after brushing their teeth, or that the gums bleed freely after oral care or eating. Gingivitis can lead to complications which include serious infections, and it is an issue which needs to be addressed.
gingivitis. Classic symptoms of gingivitis can include changes in the color of the gingiva, along with swelling and bleeding. Patients may find that their gums are very tender after brushing their teeth, or that the gums bleed freely after oral care or eating. Gingivitis can lead to complications which include serious infections, and it is an issue which needs to be addressed.
Over time, the gingiva can recede. Sometimes gum recession is caused by gingivitis, but it can also be associated with other oral problems, or occur on its own. Receding gums are a cause for concern because they can expose a patient to the risk of infections and destabilize the teeth. Other gingival diseases can include gingival cancer, in which the cells in the gums become malignant, and gingival hyperplasia, in which the gums grow grossly enlarged.
The gingiva is that portion of the gums that surrounds the teeth and lies above the level of the bone. The diagram to the right is a detail which shows the microscopic structure of this vital attachment of the gums to the tooth. The soft tissue is covered by an epithelial layer (red) called the oral epithelium. This attaches to the surface of the tooth on the dentin between one and three millimeters below the level of the crest of the gingiva. The part of the gingiva below the crest but above the attachment is called the free gingival margin. The potential space between the free gingival margin and the tooth (collapsed in life) is called the gingival sulcus. Just below the epithelial attachment lies a large number of connective tissue fibers (blue) called the gingivo-dental fibers. Some, which are not visible here actually circle the entire tooth and are called circular fibers. These fibers are responsible for securely attaching the gingiva to the tooth.
In light-skinned individuals the gingiva can be readily distinguished from the adjacent dark red alveolar mucosa by its lighter pink color.
In dark-skinned people the gingiva may contain melanin pigment to a greater extent than the nearby alveolar mucosa. This melanin pigment is synthesized in specialized cells and is produced as granules that are stored within the cells that produce melanin. If pigmented gingiva is surgically inspected it will often heal with little or no pigmentation. Therefore surgical procedures should be designed so as to preserve the pigmented tissues. Clinicians sometime use the terms free and attached gingiva. Attached gingiva refers to the portion of the gingiva towards the top of the tooth. Free gingiva is firmly bound to the underlying tooth and alveolar bone.
The area of the gingiva near the crown of the tooth (Gingival margin) in young people is more likely to become exposed as a result of tooth eruption.
he gingiva occupies the spaces between teeth. It is composed of a pyramidal papilla in the incisor region. The gingiva is attached to the tooth by an epithelium and by connective tissue fibers at the top.
The attachment (between the gingiva and the teeth) is responsible for separating the dirty oral environment from the totally clean environment inside the body. The gingival attachment is doubly important because it protects the underlying bone (alveolar crest) from becoming infected. Nature is especially protective of the bone because it is not highly vascularized and an infection in bone, especially in pre modern man's environment would have been a death-dealing event. An infection in bone is called osteomyelitis, and even today, with modern antibiotics, it is still quite a dangerous condition. Thus nature built in a simple mechanism to protect mammals from getting osteomyelitis as they aged and became more susceptible to oral infection. She programmed the bone to reabsorb (to be absorbed); to "get out of the way" before the infection reached it. This is the basis of periodontal disease---The loss of bone as a protective mechanism against a dangerous bone infection. Better the loss of the teeth than the premature loss of life!
Problems with the gingiva include the following medical conditions:
Gingivitis Periodontitis Acute Necrotizing Ulcerative Gingivitis Primary Herpetic Gingivostomatitis Gingival Hyperplasia or Enlargement Epulis (Localized gingival enlargement) Gingival Erosions.
It is the soft tissue that lies between the tooth and its bony socket. As you can see, 
it is really just a continuation of the connective tissue associated with the gingivo-dental fibers. In a healthy situation, there is never a direct attachment between the bone and the tooth itself. Such a direct attachment, when it occurs in pathological situations, is called ankylosis.
it is really just a continuation of the connective tissue associated with the gingivo-dental fibers. In a healthy situation, there is never a direct attachment between the bone and the tooth itself. Such a direct attachment, when it occurs in pathological situations, is called ankylosis.
The PDL is composed of fibrous connective tissue in which the fibers run approximately perpendicularly from the tooth surface to the bony socket. In any given area, a cross section looks like a tangled mass of nearly parallel fibers that attach at one end into the cementum overlying the root of the tooth, and at the other end, into the aveolar bone inside the socket.
The bone that supports the teeth is called alveolar bone. It's only purpose in life is to support the teeth, and if a tooth is extracted, the alveolar bone that originally 
supported it will eventually be reabsorbed by the body. The part of the alveolar bone that lines the socket is a thin layer of dense cortical bone called the lamina dura. The bone that underlies the lamina dura is cancellous bone (sometimes called medulary bone). Cancellous bone looks spongy and contains blood producing "organ" called bone marrow. In fact, all three of the features discussed in this section, the lamina dura, the periodontal ligament and the cancellous bone can be seen on any intraoral dental x-ray. In the x-ray seen on the left, follow the edge of any of the three teeth present from the top of the crown down into the bone. The dark line that separates the tooth from the bone represents the space where the periodontal ligament lives. The thin bright strip of bone directly beside the periodontal ligament space is the lamina dura. Under the lamina dura is the less bright cancellous bone. If you look carefully you can see the trabeculii --the tiny spicules of bone crisscrossing the cancellous bone that make it look spongy. These trabeculii separate the cancellous bone into tiny compartments which contain the blood producing marrow. These marrow spaces are seen in the colored image of the PDL above as bright "blobs".
supported it will eventually be reabsorbed by the body. The part of the alveolar bone that lines the socket is a thin layer of dense cortical bone called the lamina dura. The bone that underlies the lamina dura is cancellous bone (sometimes called medulary bone). Cancellous bone looks spongy and contains blood producing "organ" called bone marrow. In fact, all three of the features discussed in this section, the lamina dura, the periodontal ligament and the cancellous bone can be seen on any intraoral dental x-ray. In the x-ray seen on the left, follow the edge of any of the three teeth present from the top of the crown down into the bone. The dark line that separates the tooth from the bone represents the space where the periodontal ligament lives. The thin bright strip of bone directly beside the periodontal ligament space is the lamina dura. Under the lamina dura is the less bright cancellous bone. If you look carefully you can see the trabeculii --the tiny spicules of bone crisscrossing the cancellous bone that make it look spongy. These trabeculii separate the cancellous bone into tiny compartments which contain the blood producing marrow. These marrow spaces are seen in the colored image of the PDL above as bright "blobs".
he PDL acts like a shock absorber and transmits chewing forces from the tooth to the bone. It gives a little, like a water bed, so that the tooth can move in its socket. When alveolar bone is lost from gum disease, the total amount of PDL tissue holding the tooth is reduced and the tooth become increasingly loose. Loose teeth are a bad sign.
The periodontal ligament feels and sends pressure information to the brain when you bite. The PDL also feels pain. It tells the brain when you are biting down and the information is used to coordinate chewing. A tight ligament around the tooth also prevents bacterial invasion. A healthy PDL also protects the nerves and blood vessels contained in the area.
Tooth Anatomy “ part 2” Tooth roots
The tooth roots:
the part of the tooth that is embedded in bone. The root makes up about two-thirds of the tooth and holds the tooth in place.
The roots are embedded in the tooth socket in the jaw bone.
The roots are embedded in the tooth socket in the jaw bone.
the anchor to a human tooth, the root extends into the bone of the 
jaw and houses the nerves and blood vessels that carry nutrients to the tooth. A tough, yellowish bone-like tissue, cementum, covers the root and helps hold the tooth in its socket. The cementum contains the periodontal membrane and is in contact with the gum tissue that separates the tooth from the underlying bone. Fibers of the periodontal membrane are embedded in the cementum. The root end openings allow passage of the neural and circulatory elements out of the tooth. Each human tooth has from one to four root canals that carry veins, arteries, lymph vessels, and nerves to the living pulp of the tooth.
jaw and houses the nerves and blood vessels that carry nutrients to the tooth. A tough, yellowish bone-like tissue, cementum, covers the root and helps hold the tooth in its socket. The cementum contains the periodontal membrane and is in contact with the gum tissue that separates the tooth from the underlying bone. Fibers of the periodontal membrane are embedded in the cementum. The root end openings allow passage of the neural and circulatory elements out of the tooth. Each human tooth has from one to four root canals that carry veins, arteries, lymph vessels, and nerves to the living pulp of the tooth.For those suffering severe tooth pain and decay and facing the dreaded root canal surgery, there is no doubt that human teeth, including the roots, contain nerves. When the pulp in the root canal becomes infected due to a deep cavity or fracture, bacteria seep in and the root can die. With the damaged or dead pulp in the root, there is increased blood flow and cellular activity for attempted repairs, creating a pressure within the tooth that cannot be relieved. Severe pain in the tooth is sensed when biting down, chewing with the diseased tooth, or applying heat or cold, such as by drinking hot coffee or eating a frozen dessert. Root canal work involves severing the neural and circulatory elements, cleaning out the infected canal, and sealing it off from further infections. Without the endodontic surgery, the infection will spread, the jawbone will begin to degenerate, and the tooth will fall out. Infections in root canals of teeth are common and sometimes they become toxic, requiring tooth extraction. New research is exploring replacing decayed tooth pulp above the root as an alternative to root canal surgery.
Molecular biologists and geneticists are exploring how the tooth root is laid down and are trying to harness the natural processes to aid in reconstructive surgery and to treat genetic disorders such as cleft palate. The ultimate goal for dentists will be the ability to regenerate lost or diseased teeth instead of replacement with dentures and dental implants. As part of the Human Genome Project, the genes controlling cementum and root development have been elucidated and now researchers are exploring what mechanisms turn on and off these genes.
Comparative morphological studies of the tooth root structures in primates including humans provide clues to dietary adaptations of ancestral and extant primates. Using biomechanics, tooth roots must resist the loads applied to the tooth crown, and their various forms appear to be adapted to the varying loads experienced by different teeth within the mouth of a primate. Variation among primate species suggests different dietary histories over evolutionary time. Inferences from this work have been used to discern ancestral feeding patterns based on fossil hominid skulls. Forensic scientists are exploring the use of root coloration as a method of aging a victim with a high correlation found between increasing chronological age and increased root coloration.
Root canals:
A "root canal" is actually only a part of the dental pulp. It has all the same characteristics and functions as the rest of the dental pulp, except that it is located inside the root portion of the tooth and is thus rather thin and spindly. When we tell a patient that they need a "root canal", we are not talking about the anatomical structure itself. We are talking about a procedure. We really mean that the nerve is sick and must be removed in its entirety from the tooth, the empty space where it used to live cleaned and sterilized and finally sealed with a form of rubber called gutta percha or one of the newer materials designed for this purpose. The technical name for this procedure is "endodontic treatment". The root canal(s) in any given tooth start out just like the rest of the nerve, as a solid piece of soft tissue. Blood vessels and nerves enter through a hole at the tip of each root. The tip of the root is called the "apex", and the hole that allows the nerve tissue, with its accompanying blood vessels to enter the tooth is called the apical foramen. Of course, blood must traverse through the root canals in order to infuse the nerve. As we age, the root canals too replace themselves with more and more dentin until they become less tube like and more like a network of blood vessels and nerves running down approximately the center of the root. The image to the right shows some of the complex anatomy that the dentist is presented with when he must perform a root canal procedure to relieve pain and infection. In fact, the nerve anatomy can become even more complex as we age. As the canal becomes thinner and thinner, we say that it has become sclerosed. One can see that it could be quite difficult to remove ALL the dead tissue in the root canals if its internal anatomy has become more and more sclerosed and difficult to negotiate as the tooth ages or becomes sick. While it is important for the endodontist to remove as much dead nerve tissue as possible from the pulp chamber and root canals, the final line of defense against endodontic failure is to make sure that any remaining dead nerve tissue inside the tooth is properly sealed off at the apical foramen and any other openings in the root by properly fitted and placed sealing materials.
The Cementum:
Cementum is to the root of a tooth as enamel is to the crown. Cementum is a relatively soft bony tissue that covers the root surface in a thin layer. Its main function is to act as an attachment layer for the periodontal ligament which is a soft tissue sheath that acts as a cushion between the bony socket and the tooth itself. It is relatively soft and does not wear well against environmental assaults, so it abrades away rapidly whenever it is exposed to the oral environment because of recession. The image to the right shows the relationship of the enamel that covers the crown of a tooth, to the cementum that covers the root. Unless there is wear of the cementum due to recession, or attrition of the enamel due tobruxing or mechanical abrasion, the dentin is never exposed. The cementum meets the enamel in a line that surrounds the tooth. This line is called the cemento-enamel junction.
Tooth Anatomy “part 1”
Crown:
the top part of the tooth, and the only part you can normally see. The shape of the crown determines the tooth's function. For example, front teeth are sharp and chisel-shaped for cutting, while molars have flat surfaces for grinding.
Root:
the part of the tooth that is embedded in bone. The root makes up about two-thirds of the tooth and holds the tooth in place.
Enamel
the outermost layer of the tooth. Enamel is the hardest, most mineralized tissue in the body.yet it can be damaged by decay if teeth are not cared for properly.
Enamel is the substance that covers the crown of the tooth. It is very hard and quite resistant to mechanical and chemical attack. Its purpose, of course, is to protect the tooth from the dangers posed to the teeth by the oral environment. In general, it is vulnerable only to acid attack from excess sugar decay, generalized trauma such as a blow from a hard object, and serious bruxing with associated attrition. It is white, but somewhat translucent and allows the color of the underlying dentin to shine through to a certain extent which is why teeth look yellow. In the diagram to the left, the enamel is represented by the top layer on the tooth. Here it looks a bit like a neat haircut. The reason it is drawn that way is because the enamel is made up of microscopic enamel rods all of which run about parallel to each other and which
project perpendicularly from the surface of the underlying dentin. When you are looking at a tooth in the mouth, you are seeing millions of these little enamel rods packed side by side, but you are seeing them end-on, as in the illustration on the right which is a reasonable representation of their cross section.They are packed together a bit like an Escher drawing.
project perpendicularly from the surface of the underlying dentin. When you are looking at a tooth in the mouth, you are seeing millions of these little enamel rods packed side by side, but you are seeing them end-on, as in the illustration on the right which is a reasonable representation of their cross section.They are packed together a bit like an Escher drawing.
Dentin
the layer of the tooth under the enamel. If decay is able to progress its way through the enamel, it next attacks the dentin . where millions of tiny tubes lead directly to the dental pulp.
Dentin is the hard, yellow bone-like material that underlies the enamel and surrounds the entire nerve. It composes the bulk of the tooth, and is sensitive to touch and other stimuli. In the image at the top of this page, the illustration shows thousands of tiny little lines that run approximately parallel to each other and perpendicular to the surface of the nerve space. These lines represent tiny tubes that run parallel to one another throughout the structure of the dentin. These are called dentinal tubules, and they originate from the inner surface of the nerve space and travel perpendicularly from their point of origin to the surface of the tooth terminating at the undersurface of the enamel, or the surface of the root itself in areas where it is not covered with enamel.
The tubules contain tiny projections of cells that line the inside of the nerve space. These cells are called odontoblasts, and they are actually the covering layer of the nerve itself. The projections of the odontoblasts into the dentinal tubules are not nerves. However, the odontoblasts connect with nerve axons in the dental pulp (nerve). Exposed dentin is sensitive to touch, air and other stimuli because these stimuli cause movement of the fluid in the odontoblast projections inside the tubules. This movement of fluid can be sensed by nerve endings in the dental pulp which anastomose (connect) with the odontoblasts. The image on the right above is an electron micrograph of actual dentinal tubules seen end-on.
pulp:
the soft tissue found in the center of all teeth, where the nerve tissue and blood vessels are. If tooth decay reaches the pulp, you usually feel pain.
hat the lay public calls the nerve of a tooth is called the dental pulp by dentists. It is a complex organ composed of connective tissue, blood vessels, and nerve axons. It is pink and soft, and looks just like the lining of the mouth when it is removed during root canal procedures. Its original purpose during development is the formation the teeth themselves. In other words, the nerve of a tooth is a "generative" organ. The nerve starts out as a clump of specialized cells, and as we begin to grow, it slowly takes the shape of a tooth. The cells on the outside of the pulp begin to form the various hard structures , enamel and dentin, that we associate with the tooth itself. The tooth is formed from the outside toward the inside, with the dental pulp slowly replacing itself with tooth structure. While we are still young, the nerves in our teeth are relatively large, but they slowly shrink becoming more and more narrow throughout our lives. Once the tooth is fully formed, the nerve slows its formative functions, but it keeps building dentin in a process called dentinogenesis. During this slow growth phase of its life, the nerve serves mostly to keep the teeth hydrated and allows the dentin to retain a certain amount of elasticity. Thus, living dentin acts something like a shock absorber, preventing the teeth from fracturing. Whenever a nerve in a tooth dies, the tooth looses this shock absorber effect and is more prone to fracture. This is the reason that a tooth that has been endodentically treated needs to be protected with a crown.
