DIET AND NUTRITION RELATED TO DENTAL CARIES

INTRODUCTION The relation between diet and nutrition and oral health and disease can best be described as a synergistic 2-way street. Diet has a local effect on oral health, primarily on the integrity of the teeth, pH, and composition of the saliva and plaque. Nutrition, however,has a systemic effect on the integrity of the oral cavity, including teeth, periodontium (supporting structure of the teeth), oral mucosa, and alveolar bone. Alterations in nutrient intake secondary to changes in diet intake, absorption, metabolism, or excretion can affect the integrity of the teeth, surrounding tissues, and bone as well as the response to wound healing. The interaction between diet and tooth is of great importance in relation to caries. Although, it is true that microorganisms are chiefly responsible for caries but the importance of substrate cannot be undermined because microorganisms cannot cause caries without a suitable substrate. The occurrence of caries is dependent on two factors – pre-eruptive (blood, saliva) and post-eruptive factors (maturation, mineralization, chelation, plaque, bacteria).

RATIONALE Oral health has often been viewed in isolation from the rest of the body and from general health. In the past dental health professionals have focused largely on local reparative treatment of oral disease. However, modern-day dentistry places increased emphasis on disease prevention and recognises the importance of the interrelationship between health of the teeth and oral tissues and the general health of the body. It is well established that a good diet is essential for the development and maintenance of healthy teeth, but healthy teeth are important in enabling the consumption ofa varied and healthy diet throughout the life cycle.

In modern society, the most important role of teeth is to enhance appearance; facial appearance is very important in determining an individual’s integration into society. Teeth also play an important role in speech and communication. In addition to being costly to treat, dental diseases cause considerable pain and anxiety, and eventually may lead to loss of teeth. Tooth loss, in turn, impairs chewing function and may result in the consumption of a limited diet of poor nutritional quality and may impact on diet-related quality of life. It is, therefore, clear that dental diseases have a detrimental effect on quality of life both in childhood and older age. Nutrition and diet impact on oral health in many ways. Diet is a major aetiological factor for dental caries and enamel erosion, and nutritional status impacts on the development of the teeth and the host’s resistance to many oral conditions, including periodontal diseases and oral cancer.

THE BURDEN OF DENTAL DISEASESDental diseases are a costly burden to health care services.The treatment of dental caries is expensive for governments of both developed and developing countries and costs between 5 and 10% of total health care expenditures in industrialised countries exceeding the cost of treating cardiovascular disease, cancer and osteoporosis. The level of caries is higher for the primary dentition than the permanent dentition for children of several developing countries. Available data show that the mean DMFT at age 12 years of low-income countries is 1.9 compared with 3.3 DMFT for middleincome countries and 2.1 DMFT for high-income countries.

FOODFood is a complex chemical mixture of organic and inorganic materials containing both diet and nutrients.

DIETDiet is the total intake of substances that provide nutrition and energy. It may be dairy or milk group, meat or poultry group, vegetable or fruit group and bread or cereal group.Balanced diet: is defined as one which contains different types of food in such quantities and proportion that need for energy, amino acids, vitamins, minerals, fats, carbohydrates, and other nutrients is adequately met for maintaining health, vitality and general well being and also makes small provisions for extra nutrients to withstand short duration of illness.

NUTRITIONNutrition is defined as the science of how the body utilizes food to meet requirements for development, growth, repair, and maintenance. COMPONENTS OF FOODS There are six classes of nutrients found in foods: carbohydrates, fats, proteins, vitamins, minerals, and water. The first three are energy-producing nutrients; that is, they provide calories and enable the body to generate energy for carrying on its many functions. Although the latter three do not provide energy, they facilitate a variety of activities in the body.

THE NUTRIENTS Carbohydrates

Carbohydrates are most commonly classified as simple (sugars) or complex (starches, fibers). Simple sugars (monosaccharides) represent single carbohydrate units such as glucose, fructose, and galactose. Disaccharides are formed by the bonding of two monosaccharides. For example, sucrose, the sugar most commonly associated with dental caries, is composed of glucose and fructose. Polysaccharides such as starch and fiber are composed of many monosaccharide units. Starches are derived from plant foods— mainly grains, legumes, and some vegetables and fruits. Ultimately, the digestive process breaks down the long chains of starch to

glucose. Fiber is similar to starch in that it is composed of long strands of simple sugars; however, unlike starch, fiber cannot be degraded by human digestive enzymes. Sugar, legally defined as sucrose, has been accused of causing hyperactivity, criminal behavior, obesity, and a host of other maladies. Although research has not proven such accusations, an abundance of refined sugars in the diet can contribute to dental caries and nutrient displacement. This can deplete the body’s reserves of nutrients and result in nutrient imbalances that may affect proper development, wound healing, and immune response. Processed, cooked starchy foods, especially when combined with refined sugars (eg, donut, pastry, snack/potato chips, crackers) also can contribute to dental caries and plaque formation, thereby contributing to the development of periodontal disease. It is recommended that when highly processed simple sugars and starchy foods are consumed, they should be consumed sparingly and with meals to decrease caries and periodontal disease risk. Today, many processed foods utilize various forms of sugar such as sucrose, fructose, high-fructose corn syrup, honey, molasses, maltose, and others. Interestingly, honey is currently being investigated for use in dentistry as an antibacterial agent. Although considered as cariogenic as sucrose, the beneficial properties of certain honeys (antioxidant, antiinflammatory, antimicrobial) may outweigh the risks. Alternative sweeteners such as sugar alcohols (eg, sorbitol, xylitol), aspartame, saccharin, sucralose, and acesulfame K are also available in food products; they do not contribute to dental caries and may be useful as sugar substitutes in various food items. Xylitol in chewing-gum form was shown to inhibit Streptotcoccus mutans activity and has been applied as part of a caries control regimen. In addition, xylitol stimulates saliva production and the bicarbonate ions generated help neutralize plaque acids. Aspartame should not be consumed by persons with phenylketonuria because their bodies cannot metabolize excess phenylalanine, a component of the sweetener.

LipidsDietary lipids are divided into fats and oils; fats are generally solids atroom temperature, whereas oils are liquids. Dietary lipids are often classified by their chemical structures as triglycerides, phospholipids, and sterols. Saturation refers to the number of hydrogen atoms attached to the carbon skeleton of the fatty acid. If a fatty acid can acquire bonds with more hydrogen atoms, then it is termed unsaturated. Double bonds connect the unsaturated carbons. Saturated fats have no double bonds, monounsaturated fats have one double bond, and polyunsaturated fats have two or more double bonds. In recent years, fat substitutes have come on the market. For example, Simplesse (CP Kelco US Inc., Wilmington, DE) is a fat substitute made from milk protein and egg whites. Olestra (Proctor and Gamble), a sucrose-based synthetic fat, is frequently used in fat-free foods. Because it is not digested or absorbed, it does not contribute calories. Fats are important to oral health from the standpoint that phospholipids are a structural component of cell membranes, tooth enamel, and dentin. Fats are involved in the initiation of calcification and mineralization of teeth and bones. In addition, research indicates that high-fat foods tend to be inhibitory towards dental caries. Small quantities of nuts and cheeses, for example, can be good between-meal snack foods or even as ‘‘dessert’’ substitutes for patients concerned with dental caries. The oral health care provider should be aware that some patients concerned about fat content of their diet may drastically reduce fat intake, with potential consequences. These patients may present with sensitivity to cold, dry skin, dull hair, and gaunt appearance. The dentist should inquire about the diet of such patients and suggest referral to a physician if severe fat restriction is suspected. Infants and children in the first 2 years of life should not have dietary fat restrictions because this may contribute to failure to thrive.

ProteinsDietary proteins are composed of amino acids, all of which have the same basic structure that includes a central carbon atom with hydrogen, an amino group, an acid group, and a side group. The uniqueness of the side group gives each amino acid different characteristics. The body can synthesize most amino acids, but there are some that the body cannot manufacture and these are termed essential amino acids. The essential aminio acids are histidine, leucine, isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. These essential amino acids must be obtained through dietary means. One of the main functions of proteins is in the building, repair, and replacement of body tissues. Proteins also function as enzymes, hormones, regulators of fluid and acid-base balance, transport molecules (eg, hemoglobin), and antibodies. Like carbohydrates, proteins provide 4 kcal/g; however, this is not their primary function. Protein foods generally are not cariogenic, although they may be high in fat. Excessive consumption should be avoided; however, small amounts of nuts, seeds, dried beans and peas, boiled eggs, or hard cheeses, for example, make for nutritious snacks with low cariogenicity. Patients, especially older adults, may be unable to consume enough protein in their diet if they have ill-fitting dentures, are edentulous, experience gustatory changes associated with aging and/or medications, or have limited funds or inaccessibility to a grocery. Inadequate dietary protein may predispose such persons to decreased immune function, impaired wound healing, and oral infections.

Water Water is an essential nutrient for life through which all body processes occur. Nutrients and waste products are transported throughout the body by water. Water serves the body as a solvent, lubricant, shock absorber, temperature regulator, blood volume regulator, and structural component of numerous molecules, and

participates in a variety of chemical reactions within the body. About 60% of an adult human body and an even greater percentage of a child’s is composed of water. Water within the body is basically intracellular or extracellular. Intracellular fluid accounts for two thirds of body water and is high in phosphate and potassium. The remainder is extracellular fluid that includes interstitial fluid (high in sodium and chloride), plasma, and structural water such as in bones and skin. The average adult requires 2000 ml to 3000 ml of water daily (7–12 cups). The oral mucosa is very sensitive to fluid volume. Xerostomia, dry, shrunken, fissured tongue or mucous membranes, and dry skin may be noted in patients presenting with fluid volume deficit. In addition, a patient who has experienced rapid weight loss or whose denture suddenly feels loose be experiencing a fluid volume deficit. The dentist should inquire about medications being taken and dietary and fluid intake in such patients. Patients experiencing edema may note their denture fits tightly and may present with mucosal irritations related to changes in fit of the prosthesis. Patients should be encouraged to consume adequate daily water. Water should be recommended over other beverages like coffee or tea because caffeine is a diuretic. Sodas, juices, and concentrated sports drinks that contain salt, sugars, and other chemicals must be diluted as they enter the bloodstream, which causes fluid to be removed from the cells (furthering dehydration) and also triggers the thirst mechanism. Patients on high-protein diets require a much higher daily water intake to eliminate the waste products associated with protein metabolism.

Vitamins Vitamins are generally classified as water soluble or fat soluble. Watersoluble vitamins include vitamin C and the B vitamins (thiamin, riboflavin, niacin, folate, vitamin B6, vitamin B12, biotin, and pantothenic acid). The fat-soluble vitamins include vitamins A, D, E, and K. In general, watersoluble vitamins are easily absorbed into the bloodstream at the intestinal level and freely move about the cells.

They are not stored to any large degree and need to be obtained from the diet on a regular basis. Fat-soluble vitamins first enter the lymph and then the blood where their transport is often dependent on protein carriers. They are stored in the liver and fatty tissues of the body, so depletion takes much longer than with the watersoluble vitamins. Toxicity, however, is more likely with fat-soluble vitamins, especially if the source is vitamin supplements rather than foodstuffs.

VITAMINSVitamins Actions Sources Deficiency

Fat solubleA

Responsible for vision and growth;

maintenance of mucous

membranes, epithelium

Retinol in milk, fortified

margarine, butter, cheese, egg yolk, liver, fatty fish.

Beta-carotenes in milk, carrots,

tomatoes, dark green vegetables

Reduced night vision; blindness through corneal

damage; reduced

resistance to infection

D Promotes calcium and phosphate

absorption

Sunlight, fortified margarine, egg yolk, fortified

cereals

Failure of bone calcification;

rickets in children,

osteomalacia in adults

E Antioxidant Vegetables and their oils; seeds,

nuts, whole grains

May occur in premature

infants or in malabsorption

syndromesK Essential to the

formation of blood-clotting proteins

Synthesized by gut microorganisms; dark green leafy

vegetables

Increased clotting time

Water soluble C (ascorbic acid)

Essential to collagen production—used in

the structure of bone and

Fresh fruit/citrus fruits, red and green peppers, broccoli, snow

Scurvy; poor wound healing and bleeding

gums

connective tissues; aids wound healing and iron absorption

peas, Brussels sprouts

B1 (thiamin). Coenzyme in carbohydrate metabolism

Lean pork, enriched

breads/cereals, legumes, seeds,

nuts

Beri-beri; Wernicke Korsakoff

syndrome in alcoholism

B2 (riboflavin) Coenzyme in fat and protein, metabolism

Enriched and whole grains;

meats, liver, eggs, dairy products,

fish, poultry, dark leafy vegetables

Ariboflavinosis with glossitis, cheilitis, and seborrheic dermatitis

B3 (niacin) Cofactor to enzymes involved in energy

metabolism; glycolysis and TCA

cycle

Meats, poultry, fish, whole and enriched breads and cereals, milk

Pellagra; toxicity leads to

vasodilation, liver damage,

gout and arthritic

symptomsB6 (pyridoxine) Coenzyme in energy

metabolism; antibody and haemoglobin

formation

Meat, poultry, fish, whole grains, fortified cereals,

eggs

Altered nerve function

B12 (cobalamin) Transport/storage of folate; energy

metabolism; blood cell and nerve

formation

Animal foods; fortified cereals

Pernicious anemia

Folic acid (folate)

Coenzyme metabolism; fetal

neural tube formation

Green leafy vegetables,

legumes, citrus fruits

Megaloblastic anemia

MineralsMinerals provide structural components for the body (eg, in the form of bones and teeth). They allow for nerve and muscle function, blood

clotting, tissue growth and repair, and acid-base balance of body fluids, and act as cofactors for enzymes in chemical reactions within the body. Minerals are classified as major or trace minerals. Major minerals are needed from dietary sources in amounts greater than 100 mg/day. These include calcium, magnesium, phosphorus, potassium, sodium, chloride, and sulfur. Trace minerals (elements) are needed in lesser amounts and include fluoride, iron, zinc, selenium, chromium, copper, iodine, molybdenum, and manganese. Main dietary mineral sources include both plant-based and animal-based foods. Some plant foods contain binders such as oxalates, tannins, or phytates that bind the minerals within them, rendering these minerals unavailable for digestion and absorption. This is not a problem with minerals from animal-based foods. For example, beans are a good source of calcium, but calcium in milk is better absorbed.

MINERALSMineral Actions Sources DeficiencyCalcium Bone/tooth

formation; blood clotting;

nerve/muscle function; CNS; blood pressure

Milk-based foods, sardines

with bones, green leafy vegetables,

legumes

Reduced bone density

Phosphorus Bone/tooth formation;

metabolism; acid-base balance

Dairy foods, eggs, meat, fish,

poultry, legumes, whole grains

Rare

Magnesium Bone/tooth formation; nerve

and muscle function; blood

clotting; cofactor in metabolism

Whole grains, green leafy

vegetables, hard water, meats,

dairy products, fish

Associated with FVD: weakness,

muscle twitching, convulsions

Potassium Fluid/electrolyte balance; muscle

and nerve function; hormone

Whole grains, vegetables,

meats, legumes, dairy foods,

Associated with FVD: weakness,

confusion, arrhythmias

release fruits, unprocessed

foodsChloride Fluid/electrolyte

balance; gastric digestive acid

Table salt, processed foods

Associated with FVD

Sulfur Component of body proteins (eg,

hair, cartilage, nails)

Protein foods: eggs, meats, fish, poultry, legumes

Associated with protein deficiency

Sodium Electrolyte/fluid balance; nerve function; blood

pressure; acid/base balance

Table salt, processed foods

Associated with FVD: headache,

cramps, weakness, confusion,

decreased appetiteFluoride Bone/tooth

formation; increases

resistance to caries

Fluoridated water, tea,

seafood, seaweed

Increased dental caries

Zinc Required for digestion,

metabolism, wound healing,

tissue growth and repair,

reproduction

Protein foods; meats, fish,

poultry, eggs, legumes

Retarded growth; taste/smell alterations;

decreased immune function and

wound healing; slow physical/

sexual maturityIron Growth; immune

system health; haemoglobin and

myoglobin formation energy

production

Liver and other meats, fish, eggs,

poultry, green vegetables,

legumes, enriched breads

and cereals

Microcytic anemia (women and

children at risk)

Copper Coenzyme in antioxidant

reactions and energy

metabolism; iron

Organ meats, seafood, green

leafy vegetables, nuts, seeds, water from

Bone demineralization

and anemia

use; wound healing; blood and

nerve fiber production

copper pipes

Iodine Thyroxin synthesis; regulates

metabolism, growth, and

development

Iodized salt, seafood

Goiter, tiredness, weight gain

Selenium Antioxidant; may be helpful in periodontal

disease

Meats, fish, eggs, whole grains

Predisposition to heart disease

Chromium Carbohydrate metabolism

Whole grains, cheese, meats, brewer’s yeast

Possible cardiovascular disorders and

insulin dysfunctionMolybdenum Coenzyme Whole grains,

legumes, milkUnknown

Manganese Metabolic reaction participant

Whole grains, green leafy vegetables,

legumes

Unknown

Nutrition-related pediatric disorders:MalnutritionThe World Health Organization defines malnutrition as the cellular imbalance between supply of nutrients and energy and the body's demand for them to ensure growth, maintenance, and specific functions. Malnutrition can either be over-nutrition or undernutrition. Nutrients generally refer to both micronutrients and macronutrients. Nutrition is an integral component of oral health. There is a continuous synergy between nutrition and the integrity of the oral cavity in health and disease. Malnutrition may affect the development of the oral cavity and the progression of oral diseases through altered tissue homeostasis, reduced resistance to microbial biofilms and reduced tissue repair capacity.

Malnutrition is also defined as a bad diet or nutritional state due to excessive (eg, toxicity), inadequate (eg, deficiency), or an unbalanced intake.

Early childhood caries (ECC) has been defined as ‘‘the presence of one or more decayed (noncavitated or cavitated lesions), missing (due to caries), or filled tooth surfaces in any primary tooth’’ in children from birth through 71 months of age. Age-specific definitions have been proposed to distinguish severe ECC from ECC. Severe ECC is characterized by the presence of (1) one or more decayed, missing, or filled smooth surfaces in children less than 36 months; (2) cavitated, filled, or missing (due to caries) smooth surfaces in the primary maxillary anterior teeth; or (3) multiple decayed, missing, or filled surfaces in children aged 36 to 71 months. The etiology of ECC is multifactorial; the presence of oral bacteria and fermentable carbohydrates are necessary, yet proper oral hygiene and regular fluoride exposure reduce the risk of caries. Several species of bacteria found in the oral cavity have been associated with the caries process; however, the presence of Streptococcus mutans is most commonly associated with ECC. Colonization typically occurs after tooth eruption when S mutans can attach to the hard surface.

Protein energy malnutrition: Protein deficiency in the form of protein energy malnutrition (PEM) is more commonly seen in developing countries but can be found in lower socioeconomic groups in industrialized countries, in substance/alcohol abusers, and in those with eating disorders or chronic illness. Poor bone calcification, retarded centers of ossification, small teeth, delayed tooth eruption, retarded jaw growth, and crowded dentition have been related to protein deficiency during the critical growth periods. Postnatal weight gain has been found to correlate positively with the age of first tooth eruption. In addition, a study of premature infants who required prolonged care involving oral intubation and nutrition

experienced delayed tooth eruption compared with healthy premature infants.

Calcium, vitamin D, and phosphorus: are essential for the formation of bones and teeth. Deficiencies of these nutrients during critical periods of growth have been shown to have dental implications such as retarded jaw, tooth, and condyle development, and reduced quality of tooth enamel and dentin. Vitamin D and calcium deficiencies have also been found to result in generalized jaw bone resorption and loss of the periodontal ligament.

Vitamin C deficiency: has been related to loss of connective tissue, gingival hemorrhage, and tooth mobility. These effects, however, are resultant to the infectious process and highly variable depending on the bacterial plaque present. Nonetheless, vitamin C deficiency has been found to increase the risk of periodontal disease among certain populations, including smokers and persons with diabetes. Vitamin C is vital to collagen production for the formation of teeth and bone and also has antioxidant properties. As such, vitamin C is important in the healing of oral soft-tissue and hard-tissue wounds.

Vitamin A deficiency: Animal studies have shown vitamin A and beta-carotene to be indispensable to the proper growth and development of periodontium, teeth, salivary glands, and oral epithelium. Retinol deficiency can reduce mucin (Secretory protein found within saliva, provide an effective barrier against desiccation, penetration, physical and chemical irritants, and bacteria) production, leading to compromised salivary flow, weakened tooth integrity, and a marked increase in risk for caries. Vitamin A is also vital to the wound-healing process, for example, as it contributes to epithelialization, collagen formation, and immune response during the inflammatory stage of healing.

Nutrients such as vitamins A, C, and E and selenium have antioxidant properties, that is, the ability to scavenge free radicals and reactive oxygen molecules. These reactive species can cause cell damage by reacting with their membrane lipids, denaturing proteins, and altering nucleic acids. The antioxidant roles of these nutrients could provide health benefits to oral tissues; for example, recent studies suggest beta-carotene may have a role as a chemotherapeutic agent in oral cancer.

B-complex vitamin deficiency may manifest as a magenta, raw, fissured, smooth, or swollen tongue. Angular cheilitis, itchy eyes, and scaly dermatitis may also be evident.

Patients with iron deficiency may present with tissue pallor, spoon shape nails, pale, atrophic tongue, pale conjunctivae, and sensitivity to cold.

The nutritional state of a person is often manifested in oral tissues due to the rapid turnover of cells in this area and the bacterial onslaught the area receives. Healthy oral epithelium, for example, experiences a 3-day to 7-day cell turnover and acts as an effective barrier to toxins. Inadequate nutrition may cause the tissues to breakdown, become infected, and/or develop lesions.

Table I: ORAL MANIFESTATION OF NUTRITIONAL DEFICIENCIES

NUTRIENT DEFICIENCY CLINICAL MANIFESTATIONSVitamin A Gingivitis, Periodontitis, Hyperplasia of

the gingiva.Thiamine/ Vitamin B1 Cracked lips, A satin looking gingiva and

tongue, Angular cheilosis.Vitamin B2/Riboflavin Inflammation of the tongue.Niacin Fiery red inflammation of the tongue,

Angular cheilosis, Ulcerative gingivitis.Vitamin B6 Teeth or bone decay, Periodontal

disease, Anemia, Sore tongue, Burning sensation in the oral cavity.

Vitamin B12 Angular cheilosis, Halitosis, Bone loss, Hemorrhagic gingivitis, Detachment of

periodontal fibers, Painful ulcers in the mouth.

Vitamin C Bleeding gums, Mobile teeth, Delayed wound healing.

Vitamin D Enamel hypoplasia, Absence of lamina dura, Abnormal alveolar bone patterns.

Iron Very red, painful tongue with a burning sensation, Dysphagia, Angular cheilosis.

EVIDENCE LINKING DIET AND DENTAL CARIES – LANDMARK STUDIES

Historical EvidenceIt was found that caries was present since 5 million years in South Africa in hominids in Neolithics. Interestingly dietary pattern was not known. Eskimos’ skulls were free from caries.

Epidemiological EvidenceTristan da Cunha study. Tristan da Cunha is a remote rocky island in south Atlantic region. Before 1930 and 1940 onwards study showed no evidence of dental caries in this region because of consumption of raw diet. But after volcanic eruption in 1964, people living in this area moved to other areas where they developed dental caries because of change in dietary habits.

During World War II. Due to sugar restriction (rationing) in World War II (1939 – 1944), dental caries reduced among civilians. At the same time, dental caries experience among army personnel was increased due to increase in sugar consumption as more quantity of ready-made food items were supplied during war time. DIETARY STUDIES ON CONTROLLED HUMAN POPULATIONS:

1. VIPEHOLM STUDY (GUSTAFSSON et al-1954):It was a five year investigation of 436 adult inmates in a mental institution at the Vipeholm hospital near Lund, Sweden. The institutional diet was nutritious, but contained little sugar, with no provisions for between meal snacks. The dental caries

rate in the inmates was relatively low. The experimental design divided the inmates into 7 groups;1. A control group.2. A sucrose group (300gms of sucrose given in solution, but reduced to

75gms during the last 2 years).3. A bread group (345gms of sweet bread containing 50gms of sugar

daily). 4. A chocolate group (65gms of milk chocolate daily between meals

during last 2 years).5. A caramel group (22 caramels = 70gms of sugar in 4 portions between

meals). 6. An 8 toffee group (8 sticky toffees = 60gms of sugar daily for 3 years).7. A 24 toffee group (24 sticky toffees = 120gms o sugar for 18 months).

The main conclusions of the Vipeholm study were;1. An increase in carbohydrate (mainly sugar) definitely increases the caries

activity.2. The risk of caries is greater if the sugar is consumed in a form that will be

retained on the surface of the teeth.3. The risk of sugar increasing caries activity, is greatest, if the sugar is

consumed between meals.4. The increase in caries activity varies widely between individuals.5. Upon withdrawal of the sugar rich foods, the increased caries activity

rapidly disappears.6. Caries lesions may continue to appear despite the avoidance of refined

sugars and maximum restrictions of natural sugars dietary carbohydrates.

7. A high concentration of sugar in solution and its prolonged retention on tooth surfaces leads to increased caries activity.

8. The clearance time of the sugar correlates closely with caries activity.This study showed that the physical form of carbohydrates is much more important in cariogenicity than the total amount of sugar ingested.

2. HOPEWOOD HOUSE STUDY (SULLIVAN-1958, HARRIS-1963):The dental status of children between 3 & 14 years of age residing at Hopewood House, Bowral, New South Wales, was studied longitudinally for 10 years. Almost all these children had lived from infancy at Hopewood House. All lived on a

strictly institutional diet, that, with the exception of an occasional serving of egg yolk, was entirely vegetable in nature and largely raw. The absence of meat and a rigid restriction of refined carbohydrate were the two principal features of the Hopewood House diet. The meals were supplemented by vitamin concentrates and an occasional serving of nuts and a sweetening agent such as honey. The Fluoride content of water and food was insignificant and no tea was consumed.At the end of a ten year period, the 13 year old children had a mean DMFT per child of 1.6. (The corresponding figure for the general child population was 10.7%).53% of the children at the Hopewood House were caries free whereas only 0.4% of the 13 years old, state school children were free from caries. The children’s oral hygiene was poor, calculus uncommon, but gingivitis was prevalent in 75% of children. This work shows that, in institutionalized children, at least, dental caries can be reduced by a Spartan diet, without the beneficial effects of fluoride and in the presence of unfavourable oral hygiene.

3. TURKU SUGAR STUDIES (SCHEINN, MAKINEN et al 1975):These studies were a series of collaborative studies carried out in Turku, Finland, to test the effects of the chronic consumption of Sucrose, Fructose, and Xylitol on dental caries. In a 2 year feeding study, 125 young adults, divided into 3 groups, consumed the entire dietary intake using these sugars exclusively; Sucrose group-35 people, Fructose group-38 people, and Xylitol group-52 people. A dramatic reduction in the incidence of dental caries was found after 2 years of Xylitol consumption. Fructose was as cariogenic as Sucrose for the first 12 months but became less so at the end of 24 months. It was also found that frequent between meal chewing of a Xylitol gum produced an anticariogenic effect.

4. HEREDITARY FRUCTOSE INTOLERANCE (HFI):It is caused by the remarkably reduced levels of hepatic, fructose-1-phosphate aldolase into 2, 3 carbon fragments to be further metabolized.Persons affected with this rare metabolic disorder have learned to avoid any food that contains fructose or sucrose, because the ingestion of these foods causes symptoms of nausea, vomiting, malaise, tremor, excessive sweating, and even coma due to fructosemia.NEWBURN in 1969 tabulated the caries prevalence of 31 persons with HFI and found that the dental caries prevalence was extremely low.

ANIMAL STUDIESOrland et al (1954) did a study on rats. He showed that germ-free rats fed on carbohydrates produced no caries. And also when rats were fed through stomach tube in the presence of cariogenic bacteria in the oral cavity, no dental caries found.

CARIOGENICITY OF SUCROSESucrose induces the smooth surface lesion more than any other carbohydrates, especially when treated with Streptococcus mutans. Sucrose is the only carbohydrate diet degraded to glucans. Cariogenicity of sucrose does not relate to the ability to increase plaque, but ability of Streptococcus mutans to colonise smooth surface in the presence of sucrose. Glucans limit the diffusion of acids away from tooth surface.

STEPHEN CURVE (1940)Stephan, by using antimony microelectrodes, recorded the pH values of dental plaques in situ before, during, and after a glucose rinse. A typical pH response to plaque following exposure to a glucose rinse is obtained. These curves are often referred to as Stephan curves, and they have 3 main characteristics. Under resting conditions, pH of plaque is reasonably constant, 6.9-7.2. Following exposure to sugars

the pH drops very rapidly (in few minutes) to its lowest level (5.5 to 5.2 – critical pH) and at this pH, the tooth surface is at risk. During this critical period, the tooth mineral dissolves to buffer further acid at lower pH in the plaque-enamel interface and also results in mineral loss. Repeated fall of pH over a period of time leads to more and more mineral loss from the tooth surface and ultimately it presents in unfavorable way resulting in initiation of dental caries. Later slowly it returns to its original value over a period of 30-60minutes, approximately. The Stephan Curve

DIETARY SUGARS AND DENTAL CARIES

The evidence shows that sugars are undoubtedly the most important dietary factor—and the factor studied most often—in the development of dental caries.

Frequency of sugars consumption and the amount consumed

The importance of frequency versus the total amount of sugars is difficult to evaluate as the two variables are hard to distinguish from each other. An increase of either parameter often automatically gives an increase in the other and likewise a reduction in frequency in intake of sugars in the diet should result in a reduction in the totalsugars consumed. Worldwide studies on human populations show an association between sugar consumption and level of dental caries. Isolated communities that consume a small amount of sugar have a very low level of this disease. Groups of people with a high exposure to sugars have a higher level. A strong correlation exists between both the amount and frequency of sugar consumption and the development of caries, even in countries that use preventative measures such as water fluoridation. In addition to solid foods, consumption of sugary drinks also increases the risk of developing dental cavities. The link between dietary sugars and dental caries is supported by a large body of evidence. However, the limitations of the different types of studies should be considered when interpreting results : Caries develop over time and therefore the dietary factors, several

years previous to the appearance of caries, should be considered.• Animals have different teeth than humans and therefore the results of animal studies are not always transferable to human cases.• Studies sometimes measure the amount of acid produced from a food when bacteria in the mouth ferment it, in order to estimate the risk of caries, but such studies do not consider protective properties, such as effects on the flow of saliva.

In summary, there is evidence to show that both the frequency of intake of sugars and sugars-rich foods and drinks and the total amount of sugars consumed are both related to dental caries. There is also evidence to show that these two variables are strongly associated. In addition, oral hygiene standard, socio-economic status and fluoride exposure all influence the sugars-caries relationship.

Different types of sugarsMany of the earlier animal studies investigating the relationship between sugars and dental caries focused on sucrose, which was at that time the main dietary sugar that was added to the diet. However, modern diets of industrialised countries contain a mix of sugars and other carbohydrates including sucrose, glucose, lactose, fructose, glucose syrups, high fructose corn syrups and other synthetic oligosaccharides and highly processed starches that are fermentable in the mouth. Oral bacteria metabolise all mono and di-saccharides to produce acid and animal studies have shown no clear evidence that, with the exception of lactose, the cariogenicity of mono and disaccharide differs. However, early plaque pH studies have shown plaque bacteria produce less acid from lactose compared with other sugars. Some animal studies have reported an increased cariogenicity of sucrose but in these studies the rats were super infected with S. mutans which utilises sucrose in preference to other sugars. Studies in humans have also investigated the difference in the cariogenicity of some sugars for example the aforementioned Turku study showed no difference between the caries development between subjects on diets sweetened with sucrose compared with fructose. The Malmo study which investigated the effect of substitution of sucrose with invert sugar (50% fructose + 50% glucose) on caries development in preschool children in Sweden showed the cariogenicity of invert sugar to be 20–25% less that that of sucrose.

The form of sugarIt is sometimes stated that the cariogenicity of sugary food is related to its stickiness. The longer it takes a food to clear the mouth the longer the drop in pH will remain. The adhesiveness or ‘stickiness’ of a food is not necessarily related to either oral retention time or cariogenic potential. There is evidence to show that the amount and

frequency of consumption of high sugar drinks (with low

stickiness/oral retention) are associated with increased risk of dental caries.

The influence of fluoride on the sugars–caries relationshipFluoride undoubtedly protects against dental caries. The inverse relationship between fluoride in drinking-water and dental caries is well established. Fluoride reduces caries in children by between 20 and 40%, but does not eliminate dental caries. Over 800 controlled trials of the effect of fluoride on dental caries have been conducted and show that fluoride is the most effective preventive agent against caries. Widespread use of fluoride largely accounts for the decline in dental caries that has been observed in developed countries over the past three decades. Marthaler reviewed the changes in the prevalence of dental caries and concluded that, even when preventive measures such as use of fluoride are employed, a relationship between sugars intake and caries still exits. A recent systematic review that investigated the importance of sugars intake in caries etiology in populations exposed to fluoride concluded (1) where there is good exposure to fluoride, sugars consumption is a moderate risk factor for caries in most people; (2) sugars consumption is likely to be a more powerful indicator for risk of caries in persons who do not have regular exposure to fluoride; (3) with widespread use of fluoride, sugars consumption still has a role to play in the prevention of caries but this role is not as strong as it iswithout exposure to fluoride.

Fluoride intake and fluorosis Ingested fluoride affects the teeth preeruptively. An excess fluoride ingestion during enamel formation can lead to dental fluorosis and this condition is observed particularly in countries that have high levels of fluoride in water supplies. Reports indicate that the prevalence of dental fluorosis ranges from 3 to 42% in low fluoride areas and between 45 and 81% in areas with around 1mg fluoride/L water. Enamel fluorosis as well as skeletal fluorosis are found in large

areas of India, Thailand, in the Rift Valley of East Africa and many Arab States.

Starches and dental caries Studies have shown that starches are generally a much lower risk factor in developing dental caries than sugars. However, when starches are cooked or combined with sugars, the risk is greater. Rugg-Gunn extensively reviewed the evidence on the relationship between starches and dental caries and concluded that:

Cooked staple starchy foods such as rice, potatoes and bread are of low cariogenicity in humans.

The cariogenicity of uncooked starch is very low. Finely ground and heat-treated starch can induce dental caries

but the amount of caries is less than that caused by sugars. The addition of sugar increases the cariogenicity of cooked

starchy foods. Foods containing cooked starch and substantial amounts of sucrose appear to be as cariogenic as similar quantities of sucrose.

Starches have become more processed and frequencies of eating may have increased in some countries. Many highly processed starchy foods are also relatively high in fats and or free sugars and salt (e.g. corn snacks, sweetened breakfast cereals, cakes and biscuits). It is not the intake of these but the increased intake of starchy staple foods (e.g. bread, potatoes and wholegrain foods) that is being encouraged.

Fruit and dental cariesAs part of a normal mixed diet there is little evidence that fruit causes caries . Animal studies have shown that when fruit is consumed in very high frequencies (e.g. 17 times a day) it may induce caries. Dried fruit may potentially be more cariogenic since the drying process breaks down the cellular structure of the fruit, releasing free sugars and dried fruits tend to have a longer oral clearance. Having

extensively reviewed the evidence linking fruit consumption to dental caries, Rugg-Gunn concludes ‘as eaten by humans, fresh fruitappears to be of low cariogenicity and citrus fruits have not been associated with dental caries’. He also concluded that, on present evidence, increasing consumption of fresh fruit in order to replace ‘non-milk extrinsic sugars’ (free sugars) in the diet is likely to decrease the level of dental caries in a population.

Novel carbohydrates and dental caries riskGlucose polymers (glucose syrups and maltodextrins) comprise a mixture of short chain saccharides and alphalimit dextrins and are increasingly being added to foods in industrialised countries. Evidence on the cariogenicity of these carbohydrates is sparse and comes from animal studies, plaque pH studies and studies in vitro which suggest that maltodextrins and glucose syrups are cariogenic. The use of synthetic non-digestible oligosaccharides (prebiotics) is also increasing. Plaque pH studies and experiments in vitro suggest that isomaltooligosaccharides and glucooligosaccharides may be less acidogenic compared with sucrose. However, there is evidence that fructooligosaccharides, which are more widely available in foods, are as acidogenic as sucrose.

Summary of the strengths and weaknesses for the evidence linking diet to dental caries

Increased caries No relationship Decreased cariesConvincing Frequency of

intake of free sugars

Starch intake (cooked and raw

starch foods, such as rice, potatoes

and bread. Excludes cakes,

biscuits and snacks with added

mono and/or disaccharides)

–

Fluoride exposure

Amount of free sugars

Probable – Whole fresh fruit Hard cheese, Sugar-free

chewing gumPossible Undernutrition – Xylitol, Milk,

Dietary fibreInsufficient Dried fruits – Whole fresh fruit

SAFE LEVELS OF CONSUMPTION OF FREE SUGARSWhen consumption of sugars is less than 10 kg/person/year the level of dental caries is low. Research has consistently shown that when consumption of sugars exceeds 15 kg/person/year dental caries increases and intensifies (i.e. occurs earlier post-eruptively and progresses more rapidly), although exposure to fluoride may increase the safe level of consumption of sugars to approximately 20 kg/year. WHO has recommended that countries with a low intake of free sugars do not increase intake and those with higher intakes (>15–20 kg/year) aim to reduce intake of free sugars to less than 10% of energy intake (which equates to < 15–20 kg/year). It is also recommended that the frequency of intake of free sugars is limited to four times or less per day, because above this frequency the amounts of sugars consumed tends to exceed 15 kg/year and higher levels of caries occur.

DIETARY FACTORS IN CARIES PREVENTIONThe caries-preventive action of cheese has been reported in experimental, human observational, and intervention studies. Cow’s milk contains calcium, phosphorus and casein, all of which inhibit caries, and plaque pH and animal studies have indicated its caries-preventive nature. Recent epidemiological studies have indicated a positive or neutral effect of consumption of cow’s milk on caries. Breastfeeding is associated with low levels of dental caries: only a few specific case-studies have linked prolonged ad libitum and nocturnal breastfeeding to dental caries. Foods that stimulate salivary flow, including wholegrain foods, peanuts, hard cheese and

chewing gum protect against decay. Black tea contains fluoride, polyphenols and flavanoids. Both animal studies and experimental investigations in humans show that black tea extract increases plaque fluoride concentration and reduces the cariogenicity of a sugars-rich diet.

Diet recommendations for oral health are as follows:1) Eat a balanced diet rich in whole grains, fruit, and vegetables and practice good oral hygiene—particularly the use of fluoridated toothpastes—to maximize oral and systemic health and reduce caries risk. 2) Eat a combination of foods to reduce the risk of caries and erosion; include dairy products with fermentable carbohydrates and other sugars and consume these foods with, instead of, between meals; add raw fruit or vegetables to meals to increase salivary flow; drink sweetened and acidic beverages with meals, including foods that can buffer the acidogenic effects. 3) Rinse mouth with water, chew sugarless gum (particularly those containing sugar alcohols, which stimulates remineralization), and eat dairy product such as cheese after the consumption of fermentable carbohydrates. 4) Chew sugarless gum between meals and snacks to increase salivary flow. 5) Drink, rather than sip, sweetened and acidic beverages. 6) Moderate eating frequency to reduce repeated exposure to sugars, other fermentable carbohydrates, and acids. 7) Avoid putting an infant or child to bed with a bottle of milk, juice, or other sugar-containing beverage.

CONCLUSIONSIt is important that there is a recommended maximum level for consumption of free sugars because when consumption of free sugars by a population is less than 15–20 kg/person/year levels of dental caries are low. Population goals enable the health risks of

populations to be assessed and progress in achieving health-promotion goals to be monitored. Many countries that are currently undergoing nutrition transition do not have adequate exposure to fluoride and increasing intake of free sugars by these populations could have a severe impact upon the burden of disease. Promotion of adequate exposure to fluoride is important. To minimize dental erosion, the intake of acidic soft drinks should be limited. The elimination of malnutrition will help to prevent and control developmental defects of the enamel, oral infectious diseases and periodontal disease and may delay the manifestation of the oral symptoms of HIV. In line with the dietary goals for the prevention of all major diet-related chronic diseases, a diet that is high in fruits, vegetables and wholegrain starchy foods and low in free sugars and fat is likely to benefit many aspects of oral health including prevention of caries, periodontal conditions, oral infectious diseases and oral cancer.

BIBLIOGRAPHY

• Dental Clinics of North America; Introduction to Nutrition and Oral Health; Romito LM; April2003, vol 47, 3.

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• Diet, Nutrition, and Prevention of Dental Diseases- WHO Technical Report Series;916.

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Moynihan; Nutrition Society,2005,64,571-580.• Sugar and dental caries- Riva Touger-Decker and Cor van

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