Dental Plaque: Structural, Microbiological and Developmental Characteristics

3. Dental plaque and deposits. Mechanism of formation, structure. Methods of removal of dental deposits. Professional hygiene of oral cavity. Hygiene of oral cavity and its role in the complex prophylaxis of diseases of oral cavity organs and organism.

 

Bacteria constantly colonize the interface surfaces of our body all the time. Due to constant shedding of cells, large masses of bacteria are prevented from accumulating on these surfaces. In the mouth, teeth provide a hard, non-shedding surface where bacterial mass can build up. Dental plaque, which is a sticky, soft, colorless material adhering to the teeth, consists of bacterial cells (60-70% the volume of the plaque), salivary polymers, food residuals and bacterial by-products. Plaque is a naturally-constructed biofilm, in which bacteria may reach a thickness of 300-500 cells on the surfaces of the teeth. These accumulations subject the teeth and gum tissues to high concentrations of bacterial metabolites, which result in dental disease. It has been estimated that as many as 400 distinct bacterial species may be found in plaque.

Salivary flow, chewing of food, movement of tongue and cheeks over the teeth are self – cleansing mechanisms which remove plaque. Brushing and flossing everyday can help to remove plaque. A toothbrush can be used to remove plaque on most surfaces of the teeth except for areas between teeth. When used correctly, dental floss removes plaque from areas,which could otherwise develop proximal caries. Other adjunct hygiene aids include interdental brushes, water picks, and mouthwashes. An average daily brushing of approximately 2 minutes duration will remove only half the plaque, leaving the other half to promote rapid re-growth. Not removing plaque bacteria from the mouth regularly, can lead to tooth decay and dental cavities (caries) or periodontal problems (such as gingivitis and periodontitis).

Plaque formation is initiated by a weak attachment of the bacterial cells to salivary glycoproteins forming a coat (pellicle) on the surface of the teeth. Teeth are normally negatively charged and plaque is positively charged. Opposite charges attract and bond to each other. This is followed by a stronger attachment by means of sticky polymers of glucose, which are produced by the bacteria from dietary sugars. As plaque matures, a thick layer is formed and harbor different types of microorganisms. Plaque, which is few hours old, is much less harmful than plaque, which is few days old. If plaque is not removed, it calcifies into tartar (calculus). Once calculus is formed, it cannot be removed by brushing and requires professional removal.

The sudden increase in tooth decay is due to changes in diet like introduction of refined sugar. Foods that break down into simple sugars in the mouth are called fermentable carbohydrates. In the presence of sugar and fermentable carbohydrates, bacteria in the mouth produce acids, which can demineralize tooth struture. The more frequently teeth are exposed to this environment, the more likely dental caries are to occur.

As the amount of bacterial plaque increases, the tooth is more vulnerable to dental caries Thus for the healthy teeth, the frequency of sugar intake is more important than the quantity of sugar consumption. Therefore, minimizing snacking is recommended, since snacking creates a continual supply of nutrition for acid-creating bacteria in the mouth. The fact that wild animals have less caries than domesticated animals proves that the diet texture does play an important role. The tough and fibrous texture of natural food need prolonged chewing which remove plaque from the teeth surfaces better than as compared to soft diet. Drinks and foods that cause tooth decay are also those that contain enough acids on their own (as citrus fruits or some fruit juices),that start dissolving the minerals (demineralization) causing damage to teeth.

The risk of plaque mediated dental caries can be reduced by following strategies: 

·                Plaque acid production can be inhibited by fluoride containing products which reduce the ph fall following sugar metabolism . 

·                Avoiding foods and drinks containing fermentable sugars can also decrease dental caries. Consumption of foods and drinks with non-fermentable sugar substitutes like aspartame and xylitol also decreases the likelihood of acidic plaque.

·                Stimulation of saliva flow after main meals, e.g. by sugar free gum to buffer the acidic plaque also is beneficial.

 Dental plaque is also the cause of periodontal diseases, which are bacterial infections that affect the supporting structures of the teeth. The most common form, gingivitis, is an inflammatory condition of the gums. It is associated with accumulations of bacterial plaque in the area.  Diseases that are confined to the gum usually do not lead to loss of teeth, but there are other more serious forms of periodontal disease that affect deeper tissues including bone. Plaque bacteria in these infections are very complex populations, which can enter the gums and stimulate irreversible destruction of surrounding tissues.

The following increase the risk of plaque-associated gum disease.

 Inadequate brushing and flossing allowing a lot of plaque build up

·                Smoking cigarettes make you more prone to gum diseases.

·                Uncontrolled diabetes or other diseases where immune system is compromised.

 

Dental plaque is a natural biofilm (Fig. 4.2). The number of different bacterial species in dental plaque is not known, but sophisticated molecular biology studies have shown that over 700 different species may be identified; many more have yet to be characterised. The majority of these species have not been cultured in the laboratory using the current methods for bacterial isolation. It is also worthwhile noting that these molecular approaches have demonstrated that, for example, Streptococcus mutans, previously reported only to be isolated from the oral cavity after the eruption of the lateral incisors, is actually present in the mouth, colonising the tongue, within a few months of birth. A biofilm is a community of microorganisms attached to a solid surface, with the bacteria encapsulated in polymers derived from the bacteria and exhibiting specific biofilm characteristics, including increased resistance  to antimicrobials and biocides (chemicals used to kill bacteria) and the production of novel proteins. An appreciation of this type of growth has led to attempts to develop novel anti-plaque strategies, which target the inhibition of function of novel biofilm-specific proteins. Dental plaque is present on virtually all tooth surfaces and has a general structure whereby salivary and some bacterial proteins are initially deposited on the enamel surface to form the pellicle and the pellicle then absorbs further bacteria. The first bacteria to bind to the tooth surface, the pioneer organisms, include Streptococcus oralis, Streptococcus sanguinius, Neisseria and Haemophilus species and Actinomyces naeslundii. These bacteria are isolated from cleaned tooth surfaces within 60 minutes of cleaning. Following the binding of these bacteria, other organisms bind and eventually plaque of full thickness develops, partly because of bacterial binding but primarily because of bacterial growth. The binding of bacteria to the pellicle and to other bacteria is mediated by specific interactions in which only certain bacteria bind to components of the pellicle and only certain bacteria interact. One of the major and most interactive of all the bacteria in dental plaque is Fusobacterium nucleatum which binds to many other bacteria; it acts almost as a nucleus for plaque formation, cross-linking otherwise non-interacting bacterial species (Fig. 4.3). The composition of dental plaque varies over time. In supragingival plaque the flora becomes more anaerobic, with pigmented anaerobic rods such as Prevotella  and Fusobacterium  species becoming increasingly abundant as the plaque accumulates and ages, as it becomes a climax community. However, in the sites where caries is initiated, in the stagnation sites (in the pits and fissures on the occlusal surfaces and at approximal sites on the enamel and at the gingival margin on exposed root surfaces) the composition of the plaque reflects the acidic environment of these sites. The organisms most likely to be isolated from these stagnation sites are Streptococcus mutans and  Streptococcus sobrinus (mutans streptococci), other streptococci (S. oralis, S. intermedius and S. anginosus), lactobacilli, Actinomyces and Bifidobacterium species. These organisms are Gram-positive, acidogenic (producing acid from sugars) and each includes strains which are aciduric (able to survive in acidic environments). At these stagnation sites yeasts, such as Candida albicans, may also be present as they are also acidogenic and aciduric.  Veillonella species, which are Gram-negative cocci, are also isolated, as this genus has the ability to use lactic acid produced from these other species to generate energy for growth.

 

Figure 4.2 Dental plaque is a natural biofilm covering virtually all exposed surfaces of the dentition.

 

The development of dental plaque

The oral bacterial flora attaches itself to tooth surfaces in an organised and recognisable way. A film of glycoproteins known as the tooth pellicle covers the tooth surface within minutes of being cleaned. It is colonised by a layer of so-called pioneer species, forming first a thin layer, and later palisades (piles) of cells perpendicular to the tooth surface. By 24 hours a wide variety of bacteria (mainly Gram-positive facultative streptococci) can be identified and more new bacteria join the plaque over the next 24–36 hours until a fully mature plaque, known as a climax community, has developed. Further investigation has identified specific microorganisms that are associated with periodontal health and disease states. Socransky et al. (1988) have grouped them into colour complexes (Fig. 5.13). The red (particularly) and orange complexes of bacteria are thought to be the most influential in causing periodontitis. Complexes to the left of the diagram, green and yellow especially, are thought to be compatible with gingival health. The composition of plaque is influenced by diet. A high-protein diet produces a more alkaline plaque, associated with an increase in Gram-negative organisms and the presence of peptides, which may have an offensive odour. A high-carbohydrate diet will tend to be associated with a more acidic plaque favouring a reduction in Gram-negative organisms. The bacteria, suspended in a matrix of water and various other substances, stick to the tooth surface to form a biofilm. This increases in thickness primarily due to bacterial cell division. The matrix fluids provide nutrients for the bacteria and enable the plaque to resist toxic substances, and this is why antibiotics have difficulty penetrating the biofilm to kill the organisms. In order for periodontal therapy to be successful, the plaque biofilm must be mechanically disrupted. Some form of root surface instrumentation is essential.

Calculus     

Calculus is a hard deposit of calcium salts found on the surface of the teeth. Initially this consists of octocalcium phosphate (brushier) but after about 6 months this matures to hydroxyapatite. It tends to form more rapidly close to the parotid (buccal to the upper first and second molars) and sublingual salivary ducts (lingual to the lower anterior teeth) where saliva enters the mouth.

Two main types of calculus are recognised based on its location:

■ Supragingival calculus forms at and above the gingival margin. It is usually yellow in colour and clearly visible.

■ Subgingival calculus forms below the gingival margin and is therefore invisible on superficial examination. It is frequently dark brown or green in colour due to the inclusion of haem, a blood breakdown product. A highly alkaline saliva favours the production of calculus and when saliva flow rates are high, a high proportion of bicarbonate is found, raising the pH. It forms more readily within plaque and is often thought of as mineralised plaque.

Calculus is a local environmental factor for periodontal disease because:

■ It has a rough surface always covered with pathogenic bacteria.

■ It increases plaque retention.

■ The contour changes produce overhangs and increase plaque retention.

■ It is almost impossible to control periodontal disease in the presence of calculus.

There are two sorts of calculus :- Sub-gingival calculus (along the roots)- Supra-gingival calculus (visible on the teeth)Tartar mostly forms in areas near salivary glands, which are on the lingual side of the inferior incisors and on the labial side of the superior molars.It is calcified form of dental plaque, originating from minerals contained in saliva (calcium ions). Calculus is porous and rough. It enables a new dental plaque retention, that will calcify and add to the existing coating. Calculus is in fact made of small empty cells, not of living bacteria. It is not in itself harmful but its accumulation creates gingival lesions, promoting inflammation, and so on gum bleeding. If the bleeding becomes serious, there could be osseous lesions leading to tooth mobility and halitosis (bad breath).

Teeth cleaning

Calculus primarily forms on the lower incisors’ lingual face (on the side of the tongue). It can also be found on the first superior molars on the vestibular face (on the side of the cheek). Other areas of the mouth are less prone to tartar but still accessible in extreme cases.

Depending on the person, calculus can built either fast or slowly.

Different factors come into consideration :

 

Brushing efficiency: the better the dental plaque is removed, the less tarter will form.

·                Saliva: it can be a tartar building factor considering pH variations, the buffering capacity, quantity…

·                Tobacco: it is a harmful substance for the periodontium.

Teeth cleaning

·               

Calculus is the result of dental plaque calcification. Keeping it for too long can lead to an inevitable premature tooth loosening and thus to teeth loss.

·                A teeth cleaning consists in removing all the calculus coating fixed on the dental surfaces and especially in between the teeth.

·                The cleaning is performed with high frequency vibrations using ultrasound and water irrigation, enabling the dislocation of calculus and other debris fixed on the teeth without causing any harm to the tooth enamel. Most of the time, a teeth cleaning will be painless, but it is possible for patients with loose teeth to feel a minor discomfort during the treatment. Some patients showing very specific pathologies will be required to follow a preliminary antibiotic treatment and/or a one month program using the “Mons paste” prior to the teeth cleaning. Indeed, this simple procedure can lead to microorganisms passing through the blood circulation and thus causing health difficulties.

Frequency

The necessity of a teeth cleaning varies among people, considering calculus growth speed, the patient’s sensitivity to periodontal diseases, the quality of his tooth brushing or other personal factors (tobacco consumption, his saliva’s quality…). The frequency can go from once every 3 months to once every few years.

It is for this reason that most practitioners recommend a teeth cleaning once a year, at the same time of an annual medical visit. A teeth cleaning is not a teeth-whitening treatment, even though it does whiten the teeth as tartar has a yellowish colour.

Lithotripsy

It consists in removing bacteria and calculus deep into the periodontal pockets using specific instruments (infrasound, optical fiber, air stream).
• This procedure does not need any gum detachment or stitches.

• Multiple sessions are required.

 

BRUSHING TECHNIQUE

a) Brush at least twice a day

b) Brush no more than 3 times a day      

c) Brush lightly

d) Brush for at least two minutes

e) Have a standard routine for brushing

 f) Always use a toothbrush with “soft” or “extra soft” bristles

g) Change your toothbrush regularly

h) Choose a brush that has a seal of approval by the American Dental Association

 i) Electric is fine, but not always necessary

 

ORAL HYGIENE

The time spent on brushing your teeth doesn’t necessarily mean it is effective. The technique in this case is the most important factor. The best way not to forget to brush an area of your mouth is to always follow a methodic order. It must ideally be accomplished after every meal taken.

·                it should be done 2-3 times per day;

·                The brushing must be done with the mouth half open;

·                If it is a manual brush, always brush from the red (gums) to the white (teeth).

·                The tongue mustn’t be forgotten, as it serves an important role with oral hygiene (bacteria from dental plaque are also found on the tongue).

Both jaws must be treated separately. The brushing must begin from the last tooth of one side and end at the opposite side. For efficiency reasons (in order to attain a brushing automatism), the brushing must always be done the same way:

Upper jaw, occlusal face brushing (masticating side): The brush must be set on the last right molars, progressing towards the last left molars by making a back to front movement (repeat it three to four times every two teeth). Upper jaw, lateral face brushing (cheek side): The brush must be laid on the gum with a 45-degree angle in order not to damage it.

 

 

·                Then create a rolling action from the back to the top of the teeth with your wrist and repeat it three or four times. It is very important to always start from the gum (red) to the tooth (white) to chase any dental plaque depot from the neck of the tooth and between the teeth (the opposite movement would bring it back). This gesture must be performed from one side to another. At last, repeat the same rolling action from the palate to the tooth, from one side to another. The palatine or lingual face cleaning of the incisors must be done tooth by tooth, holding the brush in a vertical position (indeed, the arch’s curve enables an efficient gesture with the brush horizontally held).

·                Repeat the same operation for the lower jaw

·                The toothpastes

·                Favor gels to abrasive toothpastes. To identify an abrasive toothpaste, put some in between your molars. If you can feel small grains, it is no good!

·                To-do yourself: “Mons paste” (hydrogen peroxide + sodium bicarbonate). Hydrogen peroxide: it is an antiseptic and helps with the white blood cells’ activity. Sodium bicarbonate: it is non-abrasive and regulates the oral pH.

·                The mixture must be coated all over the mouth with an interdental cleaner and rinsed out with a non-alcoholic mouthwash.

·                This treatment needs to be done mid-day and night, one week a month.

 

 

 

FLOOSING TECHNIQUE

TIPS

Ways to prevent tartar buildup

Eat hard fruits and vegetables

Hard foods like carrots make the gum line firmer hence reducing the risk of bleeding in gums. These foods also promote healthy teeth because they do not stick on after consumption; in fact they aid in scraping off some of the soft carbohydrates that might have accumulated on teeth. So eating a hard fruit after a main meal is advisable.

Eat sour/acidic fruits

Acidic juices from fruits like lime and lemons are natural bleaching agents, so they keep teeth whiter when consumed regularly but not excessively. The acid also reacts with some of the foods that buildup on teeth hence preventing plaque or tartar buildup. Eat acidic fruits sparingly because when consumed in excess they can corrode the enamel.

Floss teeth at least twice a week.

Tartar buildup is prevalent in some individuals who brush their teeth everyday because the toothbrush does not always reach the gaps in between the teeth. Frequent flossing gets rid of food particles between the teeth hence reducing tartar buildup in teeth. When flossing, avoid abrading the gum because it might lead to bleeding.

Have your teeth checked at least twice in a year

Many people don’t pay visits to the dentist’s due to lack of health insurance; dental checkups can be expensive. Saving some money for dental checkups at least twice a year is worthwhile because you do not want to lose all your teeth by age 50. Teeth weaken and fall off the gum line after excessive tartar accumulation

Cut down on smoking cigarettes

The tar from cigarettes accumulates on teeth leading to yellowing and tartar buildup. This could be your motivation to quit smoking.

Brush teeth frequently and consistently

I had bleeding gums in my teenage years. I realized that the bleeding would surge whenever I didn’t brush my teeth on time; even thirty minutes late. Frequent and consistent brushing is recommended to stop bleeding of gums; hence preventing tartar buildup from blood accumulation. The type of toothbrush one uses can also injure the gums leading to bleeding. You may want to invest in a quality toothbrush, and replace it every 3 months to reduce risks of gum diseases like gingivitis.

Chew food properly to reduce tartar build up on teeth

Tartar buildup in gums at the back of the mouth is common because of improper chewing of food. The food that’s hard to swallow accumulates in hard-to-rich places in the mouth; hence leading to tooth decay and tartar buildup.

After you’ve had calculus removed from your teeth; it is much easier to prevent further buildup of tartar on the teeth because there will be no rough surface for the food particles and minerals to hold onto.

 

HYGIENIC INDICES

 

1-st group of Hygienic indices are used to estimate S of tooth crown that is covered by plaque. ( Fedorov – Volodkina index, Green-Vermillion index, Ramfiord index, Navy-Quigley-Hein index, Turecky index)

 

Fedorov – Volodkina index (oral hygiene index (OHI))

 

For  this index solution of Shiller-Pisarev (with iodine) is applied to 6 frontal mandible teeth    for few minutes.

Scores:

1 – surface is not colored

2 – ¼ of tooth surface is colored

3 – ½ of tooth surface is colored

4 – ¾ of tooth surface is colored

5 – all tooth surface is colored

 

Total results we will get with the formula:

HI =

∑ – sum of scores of every tooth

 

Results

1,1 – 1,5 points – oral hygiene index is good

1,6 – 2,0 points – satisfactory

2,1 – 2,5 points– poor

2,6 – 3,4 points– bad

3,5 -5,0 points – very bad

 

Oral hygiene index – simplified (OHI S), Green-Vermillion(1964)

To define this index buccal surfaces of    and lingual surfaces of   are colored using iodine solution. On examined teeth surfaces at first Debris-index is estimated, and after Calculus – index is determined.

Debris index (DI). For this index, debris is defined as soft, foreign matter consisting of bacterial plaque and food debris. The criteria include 0, no debris or stain present; 1, debris covering not more than one-third of the tooth surface or extrinsic stain without debris; 2, debris covering between one- and two-thirds of the tooth surface; and 3, debris covering more than two-thirds of the tooth surface.

Calculus index (CI). Calculus, a hard calcified deposit of inorganic salts, is scored for this index with four criteria. They are 0, no calculus present; 1, supragingival calculus present covering not more than one third of the tooth surface; 2, supragingival calculus covering between one- and two-thirds of the tooth surface, or scattered subgingival calculus; and 3, supragingival calculus covering more than two-thirds of the tooth surface, or a continuous heavy band of subgingival calculus around the tooth.

To arrive at an OHI score, one first calculates the DI and CI scores.

 

Formula:

OHI-S = ( ;

∑ – sum of scores;  DI – debris index; CI – calculus index; n- number of examined teeth ( usually 6).

Results:

The value of  OHI-S	State of oral hygiene
0 -0,6 points	good
0,7 -1,6 points	satisfactory
1,7 -2,5 points	poor
more than 2,6 points	bad

 

Second group of hygienic indices

Plaque index (PI) or  Silness – Loe index is used to estimate thickness of plaque in the cervical part of the tooth crown. During defining this index there is no colouring of tooth plaque. Thickness of plaque is determined by checking with probe 4 surfaces of tooth (buccal(facial), lingual/palatal, and proximal (mesial and distal) surfaces).

 

 

Each tooth is dried and examined visually using a mirror, an explorer, and adequate light. The explorer is passed over the cervical third to test for the presence of plaque. A disclosing agent may be used to assist evaluation. Four different scores are possible:

0- indicates no plaque present;

1 – indicates a film of plaque present on the tooth;

2 – represents moderate accumulation of soft deposits in the gingival pocket or on the tooth that can be seen by the naked eye;

3 – represents an abundance of soft matter within the pocket or on the tooth.

Each area of each tooth is assigned a score from 0 to3. Scores for each tooth are totaled and divided by the four surfaces scored. To determine a total PI for an individual, the scores for each tooth are totaled and divided by the number of teeth examined. Four ratings may then be assigned: 0 = excellent, 0.1-0.9 = good, 1.0-1.9 = fair, 2.0-3.0 = poor.

 

Information was prepared by Levkiv M.O.