Caries Management - Science and Clinical Practice. Группа авторов
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Название: Caries Management - Science and Clinical Practice
Автор: Группа авторов
Издательство: Ingram
Жанр: Медицина
isbn: 9783131693815
isbn:
Fig. 1.18a–e An example of how to examine microorganisms in the groove–fossa system. Just after extraction the tooth was serial-sectioned (a,b). The hard tissue was removed leaving the plaque of which semi-thin sections were prepared (c). Ultrathin sections were prepared and examined in a transmission electron microscope (d,e). At the entrance many dividing microorganisms are seen and they are arranged perpendicular to the enamel surface (EN) (d). In the lower zone few cell divisions, no structure, and areas of mineralization (ML) are visible (e).
SUMMARY
Physiological Interaction Between the Three Systems in the Oral Cavity
Teeth consist of enamel, dentin, cementum, and the pulp tissue. Microorganisms in the mouth will adhere to the tooth surface and grow if not removed by physiological functions or by oral hygiene measures. When the teeth are clean and in direct contact with saliva with a pH around 7 (Fig. 1.19a), saliva is supersaturated with respect to the minerals found in the dental hard tissue, which is mainly hydroxyapatite. According to the Le Chatelier law, the hydroxyapatite should be precipitated; however, due to various proteins in the saliva, such as statherin, this does not take place. In the case that microorganisms accumulate, and metabolize carbohydrates, different kinds of acid are produced and consequently the pH will drop somewhat (Fig. 1.19b). The buffering systems in the saliva will initially neutralize the acids. If mature (cariogenic) plaque is developed, the microorganisms will primarily secrete lactic acid when they metabolize carbohydrates, which will lead to an undersaturation of relevant ions in the saliva and this will result in demineralization of the dental hard tissues (Fig. 1.19c). The undersaturated condition in the saliva, relative to calcium, phosphate, and the hydroxyl ions, occurs when the pH is lower than 5.5. What happens when the pH returns to normal, and how fluoride and statherin interact with these processes, will be covered in Chapters 2 and 3. Besides the electrolytes in the saliva, the clearance rate is very important in the caries process, as a high clearance rate, for example, by masticating chewing gum, will cause the pH drop to be less than if the clearance rate were suboptimal, or even compromised as seen in cases of hyposalivation (Fig. 1.20).
Fig. 1.19a–c Schematic illustration of the relation between acid (H+), pH drop, and the interaction of the buffers in the saliva.
Fig. 1.20 Schematic diagram showing the relationship between pH drop after sugar in-take (arrow) and the function of saliva with stimulation, without stimulation, and in hyposalivation. It appears that with stimulation the pH returns much faster to its normal level.
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