A few bacterial species, especially streptococci, can bind directly to the pellicle. On the one hand this happens via positively charged calcium ions that mediate between the negatively charged surfaces of the pellicle and the bacteria.
On the other hand, there is also direct, specific binding of bacterial proteins lectins to the pellicle structure. Already five minutes after the tooth surface has been cleaned, the first bacteria start attaching to the newly formed pellicle. They then proliferate by cell division to form a biofilm. After two to three hours, a plaque visible to the naked eye is established. In protected areas of the mouth, bacterial colonies over the next days grow into thick, complex three-dimensional structures known as mature plaque.
If the plaque is undisturbed by tooth brush or floss, it can grow as thick as one millimetre or bacteria. To be able to continue extracting energy from food, these bacteria need to switch to fermentation, a process that yields organic acids instead of carbon dioxide and water. The resulting acidic microclimate dissolves the hydroxyapatite crystal and caries ensues. After about a week, the plaque begins to mineralise: calcium and phosphate from saliva are deposited in the bacterial colony and harden it, leading to dental calculus.
Plaque as thick and firm as this can only form in places in the mouth where bacteria can proliferate undisturbed over many days. The constant flow of saliva prevents this on most dental surfaces simply by washing away loosely attached bacterial layers.
Even in people who neglect brushing their teeth over a prolonged period of time, dental plaque and calculus do not form on exposed surfaces. However, niches such as the interdental space and gum pockets provide sufficient protection against the mechanical rinsing function of saliva.
But saliva can do even more: the proteins that form the pellicle on the tooth surface and to which bacteria can hold on, are also still present in a soluble form in saliva. Bacteria cannot actively discern whether the mucin they bound to is fixed to the tooth surface or free floating in saliva and washed into the stomach with the next swallowing process.
Many bacteria are thus entrapped and swallowed. In addition, saliva contains the enzyme lysozyme that attacks and perforates the cell walls of certain bacteria, eventually making them burst. Then there are antibodies immunoglobulin A secreted into saliva that prevent pathogens from settling in the oral cavity. Our saliva promotes bacteria that do not produce acids, and it helps kill undesirable and excess bacteria with the use of nitrate.
Nitrate is an important nitrogen source for plants and is therefore used as fertiliser. Many plants, especially salads and vegetables, store nitrate as a reserve in times of need.
Our cells do not have much use for nitrate, which is why dietary nitrate floats unused in our blood until we excrete it via urine. Some bacteria, however, can use nitrate NO 3 - instead of oxygen for respiration, turning it into nitrite NO 2 -. When nitrite gets in contact with acid it becomes a strong poison that can kill bacteria in close vicinity. Our salivary glands actively accumulate nitrate from the blood and secrete it with the saliva into the mouth.
There it has several functions: it helps those bacteria that can breathe nitrate instead of oxygen denitrifying bacteria. When oxygen is scarce they produce nitrite, but not acids, so they do not cause caries.
If a denitrifying bacterium lives next to an acid-producing bacterium, the latter will be killed through the reaction of its own acid with nitrite, resulting in reduced acid production. Less acid means better tooth protection.
So what if it was really only water accumulating in our mouth when salivating? We would choke much more often on food, because the cohesive bolus would not form.
Macromolecular nutrients such as protein and starch, but probably also fat, would have a neutral taste. We would only be able to taste pre-digested food that already contains individual amino acids and sugars. The calcium and phosphate ions leached from hydroxyapatite through the action of water and unbuffered acids would not be replaced. The dental enamel would be demineralised and become porous. Bacteria could spread undisturbed and would cause caries through increased production of acids.
Mitteilungen , H. Last Updated : 30 December Our saliva is ninety-nine per cent water. Food and saliva Preventing us from choking on food An important role of saliva during eating is based in its sliminess. The amount of saliva secreted by the major and minor glands is referred to as whole saliva.
In the resting unstimulated state, approximately two-thirds of the total volume of the whole saliva is produced by submandibular glands.
Sublingual glands contribute to a small percentage, both in the unstimulated or stimulated states of the salivary glands. Minor salivary glands contribute significantly to the lubrication of the oral mucosa because of their high protein content. Unlike some other minor salivary glands which are composed exclusively of mucous cells, parotid glands are serous and produce water like secretions. Submandibular and sublingual glands are mixed. In general, acinar secretory cells are responsible for the production of the primary saliva.
The ductal cells are responsible for further modifications of saliva until it is secreted in the mouth. The normal daily production of saliva varies between 0. The whole unstimulated saliva flow rate is approximately 0. This rate decreases to 0. Saliva is always hypotonic to plasma. As the whole saliva flow rate will increase, the tonicity of the saliva will increase too. Salivary glands secretion is mainly controlled by the autonomous nervous system.
Parasympathetic stimulation produces abundant quantities of watery saliva, whereas sympathetic stimulation produces more viscous saliva Bardow, Nauntofte and Pedersen, Saliva plays a significant role in the protection of the intraoral structures against injuries caused by various pathogenic microbes, mechanical or chemical irritants.
Saliva contains three buffer systems bicarbonate, phosphate and protein and helps in maintaining acceptable pH range of 6. When a substance is placed in the oral cavity, the flow of saliva will increase depending on its taste, consistency and concentration. When the volume of saliva is approximately 1.
Salivary stimulation, dilution of tasting and swallowing will continue until the concentration of the tastings reaches a point where it ceases to stimulate salivary flow. The oral clearance of various substances will be prolonged in the absence of saliva, resulting in possible harm to intraoral hard and soft tissues.
Under normal physiologic conditions the saliva is oversaturated with calcium hydroxyapatite, which prevents dental demineralization. In addition, the salivary protein pellicle protects the teeth against irritants. Salivary mucins play a significant role in lubricating the intraoral structures and help forming a barrier against microbial invasion.
Lysozyme and lactoferrin are examples of proteins with antimicrobial properties. Lactoferrin is believed to have antibacterial, antifungal, and antiviral properties.
Salivary peroxidase has antibacterial properties, whereas histatins have been associated with antibacterial and antifungal properties. Salivary epidermal growth factor enhances the speed of the oral mucosal healing and protects the esophageal mucosa.
In addition to these proteins with specific functions, other enzymes could serve as indicators in diagnosis, such as pseudo cholinesterase for mental disorders Giddon and Lisanti, Saliva quantity and quality can be affected by multiple diseases and medical treatments. Salivary cortisol level is increased as a response of the adrenal cortex to stressors such as chronic dental anxiety, stressful activities in front of computer, viewing anxiety-inducing videos and masticator muscle activity caused by clenching teeth.
Relaxation methods such as viewing soothing videos, listening to music Music Therapy , Iamandescu, IB, , may lower the saliva cortisol and amylase levels.
As noted earlier, the feeling of dry mouth may have a psychological cause. Psychological processes are often accompanied by disturbed oral sensations, and, in fact, most individuals have experienced a sensation of dry mouth during a period of acute stress.
Along with depression, mental stress is sometimes associated with a dry mouth condition, either as a result of the disease itself or as an adverse effect of drugs used in management of the psychological state Bergdahl and others, ; Bolwig and Rafaelsen, ; Daviessi Gurland, These issues were highlighted in the Burning Mouth Syndrome - BMS; a condition regarded, along with bruxism, as psychosomatic condition of the oral area, its symptoms matching the differential diagnosis of salivary gland dysfunction.
The burning mouth syndrome is a set of painful and burning sensations in the mouth experienced even when clinical investigation of the mucosa proves to be normal. It is assumed that a large number of agents can be responsible for this condition:. Studies of cortisol levels in depressed patients have led to interesting results provided that the technical aspects of the steroid sampling are controlled.
There seems to be differences in salivary cortisol between patients with endogenous and nonendogenous depression Iorgulescu, generally, there is a correlation between plasma ACTH levels and salivary cortisol, but this relationship is not present in patients with endogenous depression, suggesting either an effect of medication or a disorder of regulation of cortisol secretion Galard and others, Self-induced vomiting and binge eating are features of the bulimia nervosa.
Some studies have shown that parotid function is reduced in bulimics, meaning that resting and stimulated salivary flow rates are reduced in patients with sialadenosis, and the total protein and amylase levels are increased. It's made up mostly of water, with a few other chemicals. The slippery stuff is produced by the salivary say: SAL-uh-vair-ee glands.
These glands are found on the inside of each cheek, on the bottom of the mouth, and under the jaw at the very front of the mouth. They secrete say: sih-KREET , or ooze, about 2 to 4 pints or about 1 to 2 liters of spit into your mouth every day! Spit is super for lots of reasons. Saliva wets food and makes it easier to swallow. Without saliva, a grilled cheese sandwich would be dry and difficult to gulp down.
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