Why do teeth continue to decay even when brushed both in the morning and the evening?

Decay (caries) is dependant on 3 factors: The marker bacteria, carbohydrates and time. The longer plaque (bacterial colonies) is left on the tooth, the more complex the colony becomes. As bacterial colonies become more complex, the 'cariogenicity' of the plaque increases. The function of brushing is to interupt this process and prevent the decrease in pH (below 5.5 results in breakdown of the hydroxyapatite crystals of which the inorganic aspect of teeth is composed) of the area localised to the plaque. Although it is recommended that we brush 2-3 times a day, the fact is that plaque disturbance is highly dependant on more than just 'tooth brushing'. Brushing technique (Modified Bass technique being the most commonly advised method currently), brushing duration and dentifrice used all affect the degree of plaque removal.

Caries can develop on many sites of the tooth, with pits and fissures on the 'occlusal' surface of teeth being the most common in adults, and 'interproximal' (between the teeth) surfaces being most common in children. Unfortunately, brushing on its own is completely insufficient to effectively inhibit caries. Flossing is crucial to disturbance of interproximal plaque, as well as mouth washes such as Listerine being used as a adjunct to these. EVEN STILL, these processes are not entirely effective. There is only so many areas that we can physically reach and clean with what is available (for example, although fissures on the occlusal appear shallow, their depths are usually around 1mm of which tooth brush bristles are too thick to access. Too make the whole process seem more pointless, concavities and anatomical features between teeth and below the gumline make it essentially impossible to reach and remove all plaque.

The key in preventing tooth decay is to reduce the complexity and quantity of bacteria in the mouth, which is achieved by practicing regular/numerous prophylactic measures (e.g. brushing, flossing, mouth washes). An example of this is in the use of Chlorhexidine mouth washes. Generally percieved as the future of dental prophylaxis, Chlorhexidine mouth washes (e.g. Savacol) reduce the amount of bacteria of the oral environment by 45-61% (figures vary in different studies). Unfortunately, Savacol increases the rate of calculus formation, as well as staining teeth with regular use. However, with research into this product still underway, the regular use of Chlorhexidine will extend beyond its use in post-extraction cases (among others). The oral cavity contains ~800 species of bacteria (with new species being found on a continual basis), all of which co-exist in a delicate balance. While some bacteria are fairly innocuous (can even be protective), others are pathogenic and will cause decay (among other oral diseases). The regular use of prophylactic measures strongly favors the proliferation of the more innocuous bacteria, and in turn act to prevent growth of more pathogenic colonies.

In summary, brushing on its own is inadequate to effectively prevent decay. Multiple prophylactic measures are required to reduce the amount of bacteria in the mouth, with the appropriate techniques for each being key to successful decay prevention.

comments

Corinne Mirkazemi: Wow - great answer! What is the Modified Bass technique?
1 year ago

Fred Penn: Great answer. It's wrong how Colgate makes it sound like their tooth paste takes care of all the points you mention in your answer.
1 year ago

Tooth decay occurs when foods containing carbohydrates (especially sugars but also starches) are left on the teeth. Bacteria that live in the mouth digest these foods, turning them into acids which in turn decays the tooth. The key to this answer is realising that regular brushing of teeth *reduces* the chances/onset of tooth decay, but is certinaly not a guarantee.

There are four issues. First, it is the quality of brushing your teeth that counts. Not only does this include the quality of your tooth brush and your brushing, but also the fact that brushing your teeth is not as good as brushing your teeth and flossing and mouth rinsing. Over 80% of cavities occur inside pits and fissures on chewing surfaces where brushing cannot reach food left trapped after every meal or snack and saliva or fluoride have no access to neutralise acid and remineralise demineralised tooth.

Secondly, it depends on when you eat compared to when you brush. Brushing every twelve hours, means that some remnants of food can be on your teeth for upto twelve hours -- even assuming you brush your teeth perfectly.
Thirdly, it depends on how acidic your food and drink is. Anything acids with a pH value lower than 5.5 may cause tooth decay.
- mineral water pH 7.6
- milk pH 6.9
- cheese pH 5.9
- beer pH 4.4
- orange juice pH 3.8
- grapefruit pH 3.3
- pickles pH 3.2
- coka cola pH 2.5
- red wine pH 2.5

Fourthly, note that it is the *time* that your teeth are exposed to these drinks that counts more than the *amount* you drink.

So, in conlcusion, having a can of coca-cola at your desk and drinking it over a space of a morning, will expose your teeth to regular high concentrations of both sugar and acid, which given all the points above, means that ths is about the worst thing you can do to your teeth!

comments

Arman Mirkazemi: Good response thanks Martin.
1 year ago

Yes. Brushing your teeth helps to remove foodstuff and bacteria buildup in your mouth -thereby preventing tooth decay. If you only brush your teeth in the morning and evening, you still have ~12 hours during the day when you are eating and drinking, and therefore time for the damage to occur.

If you would like to be particularly careful against tooth decay, brush & floss your teeth after each meal and as soon as you wake up. Brushing when you wake up helps to get rid of bacteria build up overnight that can create tooth-damaging acid with your breakfast.