Diet and dental caries
Dental caries (decay): Is an oral infectious disease of the teeth in which organic acid metabolites produced by oral microorganisms lead to demineralization and destruction of the tooth structure.Diet
Diet: Is the sum of the food consumed by an organism. An extensive number of studies show that diet plays a central role in the development of dental caries. Nutrition is related to a balance between the supply and physiological expenditure of energy of nutrient of all the cells of the body. Thus nutrition is concerned with the systemic, metabolic effects of eating habits and nutrients in food. Prolonged periods of malnutrition will affect tissues and organs in relation to their energy and nutrient requirements. During childhood, malnutrition may restricts organ development, ex. of the brain and salivary glands, leading to a diminished metabolic capacity.During adulthood, when organ formation is complete, the effect of malnutrition mainly related to cell function.
Pre-eruptive
The enamel is non-vital tissue in the sense that after eruption into oral cavity it does not metabolize energy or nutrients or regenerate subsequent to injury. However, the enamel, dentin and cementum are highly dynamic tissue. They are exposed to a contact supply of ions of both external (oral) and internal (plaque) origin. This may for example lead to reprecipitation of minerals after PH induced mineral loss.The tooth development includes the formation an organic protein matrix, followed by mineralization and maturation. The process which follows a well-defined chronological pattern involves several critical stages.
Nutritional insults to protein synthesis or mineralization may disturb the tooth structure as well as the form and position of the teeth, and delay eruption into the mouth. Nutritional disturbance, such as deficiencies, of calcium, phosphate, vitamin D, A and C and protein energy, affected tooth tissue formation according to their general biological role, impair enamel and dentin quality and increase caries process (hypoplasia caused by vit. D, calcium deficiency).
Poor nutrition is only one of many causes of enamel developmental defects. An enamel defect that is common in undernourished communities is linear enamel hypoplasia (LEH). This occurs in primary incisors and is characterized by a horizontal groove usually found on the labial surface that becomes stained post-eruptively. Enamel hypoplasia is related to disorders in calcium homoeostatic hypocalcaemia which is common in under nutrition. Enamel hypoplasia increase caries susceptibility.
Vitamin D deficiency has marked effect on the development of teeth. It causes delayed development of teeth and that were poorly calcified and poorly aligned, cause hypoplastic teeth which have more frequently caries than non hypoplastic teeth. Mellanby and Carr reported that hypoplastic teeth, thought to be a result of vitamin D deficiency, were more frequently carious than non hypoplastic teeth.
Deficiency of protein-energy, vitamin A, zinc and iron during pre-eruptive period are reported to cause increase caries development which is claimed to be related to impaired tooth tissue. Under nutrition may exacerbate the development of dental caries in three ways:
Development of hypoplasia which in turn increase caries susceptibility.
Salivary gland atrophy which result in reduced salivary flow and altering its composition, this reduce the buffering capacity of the saliva and increase the acidogenic load of the diet.
Delays eruption and shedding of the teeth which affect the caries experience at a given age. Poorly nourished children have been shown to have 2-5 less teeth erupted compared to well- nourished children of the same age, also delayed exfoliation of primary teeth and delayed eruption of permanent teeth, this may influence the caries prevalence at given age.
Post- eruptive
Dental caries may develop in an individual if the three pre requisites, cariogenic microorganisms, fermentable carbohydrates and susceptible teeth, are present for a significant time. However, the disease development depends on factors related to enamel de- and re-mineralization and to colonization and metabolism of plaque microorganisms.
The progress is affected in a complex way but important determinants are saliva secretion and composition as well as availability of calcium, phosphate and fluoride while solubility in saliva and plaque fluid increase or decrease as PH is lowered or, normalized respectively. This can be illustrated in a schematic model on caries risk in the individual.
The salivary glands and saliva composition respond to changes in diet. Malnourished cause salivary secretion rate, the activity of salivary antimicrobial protein and the degree of protein glycosylation impaired. These impairment may increase plaque formation which leads to increase in caries prevalence.
Malnutrition also causes increased caries susceptibility as a result of systemic effect due to protein- energy deficiency in the early post eruptive period.
Salley et al reported that dental caries was increased in hamsters when they were fed a vitamin A-deficient diet. This was later confirmed in the rat by Lynch et al.
Vitamin A deficiency is known to impair enamel and dentin formation, impair immune function, reduce synthesis of specific glycoproteins, such as a salivary bacteria – agglutinating glycoprotein (BAGP) and in case of sever deficiency, to reduce salivary secretion rate.
There is a wealth of evidence to show the role of dietary sugar in the etiology of dental caries, sugar are undoubtedly the most significant factor in the etiology of caries.
There is evidence to show that many groups of people with habitually high consumption of sugar also have level of caries higher than the population average, ex. include confectionary industry workers and children with chronic diseases require long term -sugar containing -medicines. Some medical conditions such as phenyl keton urea require diet that are high in refined sugars.
Low dental caries experience has been reported in groups of people who have a habitually low intake of dietary sugars, ex. children in institutions where strict dietary regimens are followed and children with hereditary fructose intolerance (HFI) which is a congenital deficiency of fructose phosphate aldolase and consumption of fructose result in nausea and, and children of dentists.
Despite reports by parent dentists of restricted intake of sugar by their children, the low dental caries experience of these children cannot be assumed to be due to low sugar intake alone as oral hygiene and other preventive care are likely to be greater in these children.
Frequency of sugar intake
Dental caries experience increases with increasing frequency of intake of sugars. Some human studies show that the frequency of sugar intake is a more important etiological factor for caries development than the total consumption of sugar, as Holbrook et al (1995): 5 years old children in Iceland reported 4 or more times intakes of sugar/ day or 3 or more intakes of sugar between meals/ day have more caries than other population.
Type of sugars (cariogenicity of sugars)
Monosaccharide include glucose and fructose which are found naturally in fruit, vegetables and honey while galactose occur only as a result of the breakdown during digestion of lactose.Disaccharide: three main disaccharides are found if food include:
Sucrose (refined from sugar cane or sugar beets, it is a major part of dietary sugar) formed when one molecule of glucose combine with one molecule of fructose.
Lactose (milk sugar) is formed when a molecule of glucose combine in a molecule of galactose. Lactose is the sugar found in milk which is of animal rather from plant origin, and is the only disaccharide obtained primarily from animal-based food.
Maltose is formed from a combination of two molecules of glucose, it is mainly derived from hydrolysis of starch.
Polysaccharide. Unlike the monosaccharide and disaccharide, it is not sugar. Polysaccharide are known as the complex carbohydrates because their molecules are much larger and more complex than those of mono and disaccharides. All polysaccharides are made up of many individual sugar molecules, usually glucose, joined together. Four types of polysaccharides are nutritionally significant: starch, glycogen, dextrin and fiber. The digestible form includes starch which is composed of glucose found in rice, potatoes, peas, about half of dietary carbohydrates are composed of starch.
The cariogenicity of all are similar except for the lactose which has lower.
The sweetness of sugars
All sugar contribute sweetness to food, but the relative sweetness power varies among sugars. In general, the more easily the sugar dissolves in water the greater is sweetness power. For example, fructose is 75% sweeter than any other sugars. It is soluble in water, difficult to crystallize, as a result it is expensive it is useful in syrup. At the other extreme, the least sweet, least soluble sugar is lactose. Lactose is seldom if ever used as sweetener because it almost impossible to dissolve in food to be sweetened.Factors affecting food cariogenicity
Type of carbohydrateoral bacteria metabolize all mono and disaccharide sugars to produce acid. Physical location of sugars in foods affect their cariogenicity, sugars have been classified into intrinsic and extrinsic sugars.
Not harmful to teeth
Not harmful to teeth Harmful to teethNon-milk sugars: all sugars added by manufacturer, cook or consumer plus sugars present in fruits juices, honey and syrups
Intrinsic sugar: sugars physically located within the cellular structure of fruits, vegetables and cereals
Total sugars
Extrinsic sugars: sugars physically located outside the cellular structure of the food
Milk sugar: sugars naturally present in milk and milk products
Not harmful to teeth
Not harmful to teeth Harmful to teeth
Non-milk sugars: all sugars added by manufacturer, cook or consumer plus sugars present in fruits juices, honey and syrups
Intrinsic sugar: sugars physically located within the cellular structure of fruits, vegetables and cereals
Total sugars
Extrinsic sugars: sugars physically located outside the cellular structure of the food
Milk sugar: sugars naturally present in milk and milk products
Classification of sugars for health purposes: Classification of the Department of Health COMA UK, (1989), (Committee on Medical Aspect of Food Policy)
Intrinsic sugars are located within the cellular structure of the food and are not thought to be harmful to the teeth.
Extrinsic sugars are located outside the cellular structure of the food and include milk sugars and non-milk sugars (free sugars).
Milk sugars, when naturally present in milk or milk products, are not harmful to teeth (as lactose).
Non-milk extrinsic sugars (free sugars) are harmful to teeth.
In term of dental caries, the intake and frequency of intake of non-milk extrinsic sugar (free sugars) are need to be reduced.
Sucrose
Dietary sugars all diffuse into plaque rapidly and are fermented to lactic and other acids or can be stored as intracellular polysaccharides by the bacteria, but sucrose has more cariogenicity than other sugar types. It has been called the arch - criminal in dental caries.
The epidemiological evidence for sucrose as the cause of dental caries
Low caries prevalence in population with low sucrose intake
The decline in caries prevalence during wartime with sucrose shortage
The rise in caries prevalence with increasing availability of sucrose
Archeological evidence of low caries prevalence in areas before sucrose became freely available
Low caries prevalence in disorders of sucrose metabolism (hereditary fructose intolerance).
Sucrose refined from sugar canes or sugar beets is the most common dietary sugar and is largely responsible for the effect of sugar which favor colonization by oral microorganisms and increase the stickiness of the plaque, allowing it to adhere in large quantities to the teeth.
Starch and dental caries
Starch constitutes a heterogeneous food group, it varies in botanical origin, it may be highly refined or consumed in its natural state, it may be consumed raw or in a cooked form. All these factors should be considered when assessing the cariogenicity of starches.
Starch foods such as rice, potatoes and bread are of low carioganicity in human. Uncooked starch has very low cariogenicity.
The starch granules in plants are only slowly attached by salivary amylase because the starch is in an insoluble form and protected by cellulose membranes. Heating at temperatures used in cooking and backing, however, causes a partial degradation to a soluble form, which can be further broken down by salivary and bacterial amylase to maltose, malt triose, dextrin and small amounts of glucose.
Addition of sugar to cooked starch lead to increase of the cariogenicity of foods, such as sweetened breakfast cereals, sweet biscuits, cakes and cookies.
Physical form of food and clearance time
In addition to the chemical composition of food, physical and organoleptic properties (particle size, solubility, adhesiveness, texture and taste) are important for cariogenicity, since they influence eating pattern and oral retention of foods. Diet that results in the greater retention of refined carbohydrate over the longest period are the most cariogenic.The carbohydrate in various drinks are eliminated within 5 minutes while sweets such as sugar containing chewing gum, toffees and lozenges generally give high oral sucrose concentration and clearance time from 40 minutes for chewing gum to 15-20 minutes for other sweets.
The texture of the diet is also important, for both salivary secretion and elimination of fermentable carbohydrate from the oral cavity. A diet that require thorough chewing will result in the secretion of high amount of saliva with a high pH and strong buffering capacity, in contrast to finely textured diet that require little mastication tend to be retained in the oral cavity and eliminated slowly.
Factors in the diet that protect against dental caries
Food and food components that have anticariogenic properties are sometimes referred to as “cariostatic factors”. Fluoride is the most effective of these factors. However, dairy products, plants foods, tea and even chocolate contain factors that protect against caries. Other factors are:
Phosphate
The possible caries inhibiting effect of various phosphate, which are found naturally in many foods. The most promising of the organic phosphate was phytate, identified as the most active substance in unrefined cereals. The effectiveness of phytate appears to be due to its ability to adsorb readily and firmly to enamel surfaces and so prevent the dissolution of enamel by acids. Phosphates are anticariogenic and appear to be most effective. Phosphate exhibit their anticariogenic action via local factors like:
Reduction of enamel solubility
Buffering effect in neutralizing salivary plaque
Rendering fats, carbohydrates and proteins which are less cariogenic
Interference with enzymatic process on enamel surface to increase host resistance
Decrease in bacterial adhesion
Interference with synthesis of extracellular polysaccharide formation
Maintenance or increase of plaque calcium and phosphorous level.
Other inhibitors like pyridoxine, fat, tannic acid, constituents of coca, butter are believed to have caries protective factors.
Fat
Fat seems to reduce cariogenicity of food through different ways:
They may act merely by replacing carbohydrate in the diet.
Fat may also form a protective barrier on the enamel, or surround the carbohydrates, making them less available and speeding up their removal from the mouth.
Bacterial surface properties involved in plaque formation could also be altered by fats.
Certain fatty acids have antimicrobial effect and have been shown to inhibit glycolysis in human dental plaque.
Fruit and dental caries
Fruit and vegetable contain more non-starch polysaccharides and plant cell wall materials that benefit health. It is preferable to consume whole fresh fruit as opposed to juice, because their mastication provide a good stimulus to salivary flow. In addition, fresh juices contain non-milk extrinsic sugars since liquidation release the fruit sugar from the cellular structure of the fruit. There is little evidence from epidemiological studies in humans that consumption of fruit is associated with the development of caries and induced negative correlation between fruit consumption and dental caries have been reported.Milk
Human breast milk: which one of the main sources of sugar in the diet of small children, normal milk consumption does not cause dental caries. It contains higher lactose (7%) and lower phosphorous (15 mg/100 g) and calcium (34 mg/100 g) than cow’s milk.Cow’s milk: contain lactose (4-5%), which is less acidogenic than other sugar, and also contain calcium (125 mg/100 g), phosphorous (96 mg/ 100 g) and casein, all of which are cariostatic (prevent enamel demineralization).
Milk rich with calcium and phosphate which act by:
Reducing the rate of dissociation of hydroxyl apatite
Reducing the fall in pH by buffering acids produced. by fermentation.
Enhancing remineralization.
Modifying formation and composition of pellicle and plaque.
Cheese
Numerous animal and experimental studies have indicated that cheese is anticariogenic because it stimulates salivary secretion and increase plaque calcium concentration which strongly influences the balance between de- and remineralization of enamel.Plant foods
It contains organic phosphate, inorganic phosphate and phytate. The organic phosphate protect the teeth by adsorbing onto the enamel, forming a protective coat, also inorganic phosphate have been found to be effective cariostatic and prevent demineralization of enamel. Phytate is anticariogenic and act by adsorbing onto the enamel surface to form a physical barrier that protects against plaque acids. Also plant foods (fibrous foods) stimulate salivary flow. Saliva not only help to clear food debris from the mouth, but also buffer plaque acid, and therefore, favor remineralization of tooth enamel. (on animal studies only but human studies have not produced convincing results).
Chocolate
It contain theobromide which is able to increase crystal size in enamel, thus increasing the resistance to demineralizing acids. However, the high sugar content of chocolate outweighs these potential effects.
Tea and apple
Apples contain polyphenol (which have antibacterial action) and are good stimulus to salivary flow.Tea contain polyphenol in addition to fluoride and flavonoid.
Black tea extracts have been shown to inhibit salivary amylase activity and reduce dental caries.