Tooth structure, healthy teeth and dentures
Although they fulfill different functions, all 32 of our teeth are constructed in the same way. The milk teeth, molars or incisors – every single one of our teeth has three areas: the crown, neck and root. These consist of different layers and materials – from enamel, the hardest substance in the human body, to the bone-like dentine, all the way down to the sensitive pulp in the centre of the tooth.
In this article you will discover the structure of a human tooth, find out which areas need special protection during your daily oral hygiene routine and what medical approaches are available to restore your teeth.
Tooth structure: crown, neck and root
Looking at a tooth from top to bottom, it can be roughly divided into three areas: the crown, the neck and the root:
Crown (Corona dentis)
The visible part of the tooth is the crown. Its main function is to chew our food. The tapered crown of the incisor teeth is perfect for biting. In contrast, the masticatory surfaces of the molars grind up the food so that it can be swallowed easily.
Neck (Cervix dentis)
The neck of the tooth lies between the crown and the root. A healthy tooth neck is covered by the gums and is therefore well protected from external influences. However, when tooth necks are exposed due to receding gums, they often cause pain and react with sensitivity to cold and heat and to sweet or sour foods.
Root (Radix dentis)
The root is completely covered by the gums. As it is firmly anchored in the jawbone, it holds the teeth firmly in place. Whereas the incisors generally have one root only, the larger molars have up to four. The roots supply the tooth with nutrients, blood and lymphatic fluid to keep it healthy and alive.
Tooth structure: the visible part of the tooth
The gums cover the neck of the tooth and protect the underlying parts of the tooth and jaw from the ingress of bacteria. Healthy gums are pale pink and firm to the touch. Signs of gum inflammation (gingivitis) can be redness, swelling and bleeding of the gums.
Enamel forms the outermost layer of the tooth structure and encases the crown. Enamel is the hardest substance in the human body and is almost entirely composed of the mineral hydroxyapatite. Daily chewing and various other factors can form microscopically small defects in the enamel over time, which means the underlying layers are no longer protected properly.
The small grooves and depressions on the molars are called defects. Although these help when chewing up foods, they are also highly prone to cavities. As defects can be up to 1 mm deep and difficult to reach, plaque can easily form and remain in these areas. As a consequence, the so-called fissure cavities occur frequently.
Inner structure of the tooth
The dentine lies below the enamel. It is the second hardest substance in the human body and around two thirds of it are hydroxyapatite. Unlike enamel, which cannot be reproduced by the body, it is made continuously throughout our lives. Fine nerve fibres run through the dentine, so-called dentinal tubules or dentinal channels. If the enamel is damaged and the dentinal tubules are exposed, external irritants are transmitted into the tooth interior via this route, which often manifests as sensitive teeth.
The tooth pulp is surrounded by the hard substance of the tooth and a space known as the pulp cavity or chamber. It is a soft, gelatinous connective tissue, consisting of blood vessels, lymph fluid and nerve fibres, which is why it is often incorrectly referred to as the tooth nerve. The enamel extends as far as the root canals, where nerves and blood vessels enter and exit. Inflammation of this sensitive area (pulpitis) is usually caused by untreated cavities. The symptoms are extremely bad toothache and sensitivity to temperature and pressure.
The root cementum is part of the periodontium (the tooth's supporting structure) and surrounds the root and the neck of the tooth. Along with fibres, tissue and water, it compromises up to 65% hydroxyapatite, making the root cementum similar to bone. One of its functions is to anchor the so-called Sharpey’s fibres. These stretchy fibres ensure that the periodontium (the tissues supporting a tooth) is flexible rather than immobile. The pressure generated by chewing is cushioned by these fibres.
The upper jaw (Maxilla) is connected to the lower jaw (Mandibula) by a joint that enables the mouth to open and close and thus permits the chewing and grinding of food. The teeth are firmly anchored within a socket (alveolus) in the jawbone. A common reason for loose teeth is inflammation of the tooth socket (periodontitis). This bacterial inflammation causes the body’s own immune defence system to produce bone-destroying cells. In the worst case, periodontitis can there also lead to the loss of teeth.
Oral care and restoration
Brushing is one of the most effective methods of maintaining oral health and supporting the long life of the teeth. Daily brushing is focused primarily on the visible areas of the teeth: the enamel, fissures, the interdental spaces and gums, in particular the gum line.
The objective is to remove food remains and bacterial deposits known as plaque. This protects the teeth and gums from attacks by microorganisms and prevents the formation of cavities or gingivitis.
Bacteria easily accumulate on the surface of the teeth and along the gingival margin (edge of the gum), feeding on the remains of food and sugar and producing acids as a result. Acids demineralise the teeth and dissolve the crystalline components in the enamel. A diet which is rich in sugary and acidic foods also promotes demineralisation.
As a consequence, microscopically small defects appear in the enamel, to which bacteria can adhere more easily, favouring the development of cavities. Furthermore, other irritants can also be transmitted to the sensitive inner layers of the teeth via the tiny defects in the enamel. Very often, these defects are experienced as sensitive teeth when hot, cold, sour or sweet foods and drinks are consumed.
With daily use, toothpastes containing biomimetic hydroxyapatite, better known as artificial enamel, seal the microscopic cracks, thus repairing the enamel surface. The teeth then feel smoother and it becomes harder for bacteria to adhere to the surface. As a result:
- The formation of plaque and tartar is reduced
- Protection from cavities and gum problems
- Products containing hydroxyapatite are suitable for sensitive teeth
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Our teeth are made of as much as 97% hydroxyapatite. Brush back enamel by using Bioniq® products with artificial enamel.
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