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Oral Environment, Saliva and the Biofilm

It is not about the tooth, the whole tooth and nothing but the tooth; in-fact decay has very little to do with the actual tooth, it is all about the oral environment.

There are some medical/genetic conditions that weaken the enamel, but these conditions are extremely rare and are usually diagnosed early. However patients often report  “I’ve got weak teeth” “we all have weak teeth in our family” etc. This is certainly more often about shared lifestyle habits than a fault of nature.

Teeth are standard; enamel is standard, the teeth of someone who has no fillings are exactly the same as someone with extensive decay. It is the ORAL ENVIRONMENT that is different.

Dental Caries (decay) is a bacterial infection, the bacteria that cause the decay are commensal (normal) bacteria and are  present in every mouth. Dental Caries is a multifactorial disease; that means several things play a part in causing decay to develop in the mouth. The main causes are DIET, the presence and frequency of sugar intake, and SALIVA,

The presence of decay reflects a change in one or more significant factors in the oral environment. Diagnosing dental caries at Crescent Dental Health includes helping you to identify these changes and developing a customised treatment plan for each patient in which ways you can tackle these changes are included. The disease affects each patient differently and we like to help patients accept responsibility for their status and commit to rectifying the changes in the oral environment, so they can move from decay prone to decay resistant. THIS CANNOT BE DONE BY PLACING FILLINGS OR CROWNS; We are dependant on your participation in maintaining your oral health.

Saliva is undoubtedly a factor in some cases as a healthy saliva flow and quality is  vital for a healthy mouth.The quality of saliva is affected by many factors. A large proportion of the population has undiagnosed salivary problems making their teeth prone to decay and sensitivity. These problems are usually easy to solve or compensate for to help protect oral health.

The good news therefore is that a reasonable diet (with a limited amount of sugars not taken too often), reasonable hygiene, effective use of fluoride toothpaste in partnership with attending the dentist for routine screens and advise  should go a long way to keeping your mouth decay free. It is worth noting a  reasonable diet that is good for the mouth will keep you in good general health, too many sugars taken too often, will leave you short of energy, decrease your concentration and in the long term leads to heart disease, diabetes and  has been implicated in various forms of cancer.  (page 1)

SALIVA and the BIOFILM (what is that?)

As soon as a tooth erupts into the mouth, it is bathed in saliva; proteins from the saliva adhere to the tooth (and any hard surface in the mouth) to form a pellicle, this is a natural structure,it is very hard to remove, and cannot be removed by tooth brushing.

Normal, necessary bacteria, present in the mouth colonising this pellicle, the total complex of the pellicle, bacteria and their by-products are called the BIOFILM.  If we brush our teeth very thoroughly the biofilm will be removed but then it will start to re-form within just 2 minutes. The Biofilm is created from the oral environment. When decay occurs adverse changes within the oral environment change the Biofilm from protecting the tooth to damaging the tooth. We cannot remove the Biofilm and we cannot yet dictate how any given Biofilm works  we can however  make changes to the oral environment which will have a knock on effect on the oral environment.

The Primary Risk Factors that directly affect the Biofilm are the Saliva, Diet and Fluoride. These factors can be modified by lifestyle changes, socioeconomic factors, past dental history and compliance.

Dentist can diagnose the level of the dental caries activity; caries is a slowly progressing disease that is affected by many, interacting factors, the final consequence is a cavity in a tooth. If we can identify the contributing factors and manage them, either by changing them or compensating for them we can convert an individual prone to caries and resultant cavities to caries resistant and healthy teeth.

The causes of decay cannot be diagnosed by looking at the teeth or counting cavities,; decay cannot be treated by placing fillings, these only repair the damage caused by decay.

Treatment of decay requires modification of that patient’s behaviour and/or the use of chemical agents to compensate for the changes on the oral environment. The most important question for any patient suffering decay is “Are you prepared to make the necessary changes?”  Unless the answer is yes, any treatment will be of limited success as the decay process will remain and continue to damage the teeth.


Saliva plays a major role in oral health.  Changes in salivary function can have detrimental effects on both the hard and soft tissues in the mouth. Besides lubricating the mouth saliva has three functions:

  1. To clear dietary acids and sugars from the mouth.
  2. To buffer acids produced in the biofilm.
  3. To provide a reservoir of ions/minerals to allow teeth to remineralise.

The saliva consists of unstimulated and stimulated saliva, the production, composition and function are different and we assess them separately.

Unstimulated saliva is provided by the minor salivary glands. It provides oral comfort, lubrication and protection of the hard and soft tissues. It should thinly coat all surfaces and be neutral or slightly alkaline in pH.

If there is underproduction, or the saliva is too thick it will not coat the surfaces.  One of the main functions of the unstimulated saliva is to dilute and clear debris from the mouth. The saliva coats all surfaces and so the pH of the saliva will have an effect on the teeth and the biofilm. The pH of the unstimulated saliva is a good indicator of the general conditions in the oral cavity. The critical level is a pH of 5.5; lower than this the teeth will demineralise;  the closer the unstimulated pH is to 5.5 the less protection it offers and a greater chance that the teeth are being damaged.

When assessing the stimulated saliva, again we want to assess the flow rate and the buffering ability of the saliva. As with unstimulated saliva, volume is important to dilute and clear debris.  As we chew,  the saliva mixes with the food and enzymes within the saliva start the digestive process while in the mouth. The buffering capacity, is the ability of the saliva to neutralise acids and depends on the concentration of bicarbonates in the saliva, these levels increase with flow rates of saliva.

We can test for flow rates, viscosity, pH of resting saliva and the buffering capacity of stimulated saliva easily and accurately in the surgery. The constitution of the saliva can be altered by systemic disease, dehydration, hormonal imbalance, damage to the salivary glands and as a side effect from a range of medications.

As the biofilm on a tooth consists of proteins from the saliva, and is colonised by bacteria from the saliva we consider it part of the saliva. Within the normal cycle of a healthy biofilm a tooth will demineralise/remineralise but in a healthy mouth the balance lies towards remineralisation. As the biofilm is allowed to mature it thickens and becomes impervious to the buffering action of the saliva. If conditions are such and the mouth is mainly acidic the bacterial composition changes to contain a greater number of bacteria that like and produce acids. And so as part of the testing it is simple to test the thickness of the biofilm (how impervious it is to diffusion) and it’s base acidity, these are good indicators of how healthy or otherwise the mouth is in general.


There is a clear and undisputed link between refined carbohydrates (sugars) and the total amount of fermentable sugars,the food of bacteria, that powers bacteria to cause decay. But it isn’t just the amount of sugar taken, just as important is the frequency of intake, this is more important than the amount.

Ideally the pH (acidity) of the mouth is neutral (pH 6.8-7.2)  whenever we take sugars the ph of the mouth will lower becoming more acidic and generally takes about 20 minutes to recover, but this can take up to 60 minutes in some cases, we depend on the saliva to buffer the acid and clear the sugars. The magic pH number is  5.5, below this value the teeth are dissolving in the mouth.

If I take a large family size bar of chocolate and eat it all in one go my mouth is plunged into acidity for say 30 minutes before the saliva has the opportunity to do it’s work and allow my teeth to start repairing.

In contrast if I buy a packet of mints, the overall sugar content will be less, but, by taking a mint regularly throughout the day my teeth will be under attack for 20 minutes after each mint, a pack of 10 mints could lead to nearly 4 hours of attack, much more damage from less sugar. Frequency if a very important factor.

The other part of the equation is how a high sugar diet affects the bacteria colonies in the mouth. As stated the mouth contain a range of bacteria, we are still unaware of about 50% of the bacteria species in the mouth, what they do and what other species they do it with, but in general good bacteria like neutral conditions, the bacteria that cause decay prefer acidic conditions.

If over a period of time you are taking excess sugars your mouth will be acidic more of the time. This shifts the balance of bacteria numbers, conditions are less favourable for good bacteria and the acid liking, acid producing, bacteria take over. This has two effects every time sugar is taken more damage occurs as there are more bacteria and secondly as some of these bacteria produce acid, the ph of your mouth will already be low, the effect of the sugar plunges the mouth acidity even lower and takes much longer to recover.

The final part of this perfect fire storm lies with the saliva, stimulated saliva that buffers the acid is produced by chewing as often a chocolate bar or sugary snack is quickly eaten, we produce less saliva than when eating a proper meal, so less buffering and more decay.

My final pet hate are fizzy drinks and the useless isotonic sports drinks, or as I tell my kids “battery acid with added sugar” These drinks are already very acidic and attack teeth directly, this is followed up with added sugar as a double whammy. Diet drinks have no sugar but are even more acidic and so will still attack the teeth. In years to come we will look back at the food industry and wonder how they were allowed to do so much damage, it is truly depressing what they are allowed to sell as food!


To end on a high FLUORIDE, we have further information sheets on fluoride and it’s use, but to be brief Fluoride offers protection at three levels

  1. It increases the resistance of enamel and dentine to demineralisation
  2. it enhances the reservoir of ions present in the mouth for remineralisation
  3. it interferes with the metabolism os bacteria and so slows their growth and decreases their effects

Concerns have been raised about the safety of Fluoride, like any element if it is taken at too high a concentration it is toxic. Fluoride was discovered as it is naturally present in water in many areas. An american dentist noticed that some isolated groups of his patients had mottled teeth but no decay, their diet was the same as everyone else in the area. Curiosity aroused he realised the group got their water from a well and the only difference was the presence of fluoride. No study has ever found differences in disease incidence with  populations that consume naturally fluoridated water. The levels in tooth paste are much lower.

Modern toothpastes contain a range of ingredients to optimise oral health, most people after they brush rinse with water, this dilutes and washes away many of these ingredients. the effectiveness of toothpastes is massively enhanced if after brushing you swish the foam around your mouth spit it out but do not rinse with water. This coats your teeth and saturates your saliva with minerals, during the day it takes about 20 minutes for the saliva to clear the toothpaste. At night, your saliva production stops and so this method will leave your teeth bathed in minerals overnight.

This is especially effective with young children, when teeth first erupt into the mouth they are incomplete and mature over 12-18 months The surface of newly erupted teeth are permeable,  viewed under a microscope there are millions of holes in the surface. If exposed to fluoride the tooth absorbs this and make the surface very hard, the flip side is, if the tooth is exposed to sugars and bacteria the holes already exist for invasion, these teeth will decay rapidly. The ages 6-16 are  golden years for kids and in some way set the pattern for their dental future, brushing/swishing and refraining from rinsing afterwards has a massively beneficial effect.

For further information see our article on  “ A Guide To Good Brushing Habits Throughout Life”