Drug – bio-affecting and body treating compositions – Dentifrices – Fluorine or fluorine compound containing
Reexamination Certificate
2000-11-13
2002-04-23
Rose, Shep K. (Department: 1614)
Drug, bio-affecting and body treating compositions
Dentifrices
Fluorine or fluorine compound containing
C433S217100, C433S228100
Reexamination Certificate
active
06375934
ABSTRACT:
Persons who are prone to dental caries are inadequately served by today's preventive dental care. Lack of educational awareness in dental care and lack of odontological awareness in education has meant that there are insufficient aids and working methods to help these persons effectively.
The invention relates to a system that solves the problem according to the pre-characterising part of claim
1
.
Dental caries is the world's most common multifactoral disease but also one that it is possible to avoid by means of personal care measures for those who have adequate knowledge of the disease process and their own susceptibility to disease at a given time. This is because the risk of caries varies between individuals and in the individual over time. There is therefore no single method of prevention that will help all individuals every time.
If dental care personnel had the knowledge, capability and incentive to teach the patient how to proceed at any given time in order to counteract caries, the need for dentists would be drastically reduced. A corresponding effect would be achieved if skilled teachers had the odontological training that is required. So the aids which the dental hygienist needs in order to train patients are not developed for this. The lack of educationally sound aids and working methods is a problem in dental care.
It is well known that fluoride prevents dental caries and that the most important mechanism is the formation of fluorapatite on the tooth surface in connection with a reduction of the pH level to a given interval. It is also known that fluoride does not have an adequate protective effect in persons highly susceptible to caries, despite the fact that a large number of studies have been carried out with systems of fluoride administration currently in use. The most important source of fluoride is reckoned to be toothpaste.
That fluoride treatments fail is due to the fact that the dental hygienist does not take into consideration that dental caries is a multifactoral disease. It is not sufficient, as at present, to try to solve the problem of caries simply with large doses of fluoride. A factor of at least equal importance is the pH-value in the films on the tooth surface.
After eating carbohydrates the caries process causes a reduction of the pH value of the tooth films from a normal value of approximately 7.0-7.5. After a time that varies according to the individual the pH value rises again to the normal value. The curve described by the pH value during this time is known as Stephan's curve. Important factors that affect its appearance are partly the concentration of acid-producing microorganisms in the tooth films, including streptococci mutans, which end to reduce the pH value. Buffer substances, which are present in normal saliva. endeavour to counteract the reduction and to increase the pH value after a reduction. The most important buffering systems are founded on the presence of bicarbonates and phosphates in the saliva, but proteins, urea and mucoid substances have buffering characteristics.
An individual may have a number of combinations of bacteria content and buffering capacity and many Stephan curves with different appearance therefore exist. Extreme variants include, on the one hand, a pH reduction from the normal value of 7.0, by about one pH unit for a few minutes, and on the other a large reduction to values of less than 4.0 for up to two hours. Owing to a number of circumstances all these variants can, in theory, occur in each individual from time to time.
Despite the great significance of buffering for the appearance of the Stephan curve, clinical studies have only been able to show a slightly negative correlation between the buffering capacity of the saliva and caries in a normal population. The reason is that there are many other factors that affect the development of caries, among other things the presence of fluoride, good oral hygiene and good discipline with regard to sugar, all of which reduce the strength of the connection. In clinical studies the connection was so weak that simply measuring the strength of the buffering is not regarded as adequate for assessing the risk of caries in an individual. In persons with a high bacteria content on the tooth surface the correlation is greater and is due to the fact that many of these persons have a large pH reduction after eating, which increases the prophylactic importance of the pH-increasing buffering.
It is generally assumed that the correlation is linear and that persons with the highest buffering capacity should run the least risk of caries. In one (unpublished) clinical study of 96 teenagers with high acid-producing content of streptococci mutans in the saliva we found, however, that persons with medium buffering had least caries of all, including those who had better buffering (Table 1).
TABLE 1
Number of tooth surfaces with caries in 96 14-year olds with more
than 1 million CFU Streptococci mutans per ml saliva. The buffering
capacity (final pH) is registered with Dentobuff.
Final pH
DS
SD
<4.5
6.6
4.9
***
4.5-5.5
2.9
2.8
*
>5.5
4.6
3.1
*indicates P < 0.05
***P < 0.001
The high standard deviations indicate that a few individuals had developed great caries attack in each group. Note that this is a cross-sectional study and the result shows the accumulated quantity of caries attack over several years. It is highly probable that the buffering capacity of many participants has changed during the period (Table 2), which explains why certain persons with high buffering values at present (>5.5) have a large amount of caries damage. All those taking part have been exposed to fluoride rinses every 14th day from the age of 7 and have used fluoride toothpaste regularly.
These observations indicate that the intermediate group run a lower risk of caries than the group with an inferior or superior buffering capacity in a material that is exposed to fluoride.
TABLE 2
Percentage distribution of high and low buffering values on three
occasions over 18 months in 255 school children with high bacteria
values in the saliva (unpublished)
Test intervals
Start
6 months
18 months
Buffering capacity
%
%
%
Low (<5)
69.7
34.5
62.0
High
30.3
65.5
38.0
Table 2 shows that the proportion of persons who had low buffering capacity was halved during the first six months. After a further year the proportion was the same at the start.
In the light of this there are good reasons to assume that it is a combination of fluoride and exactly the right buffering capacity which gave the intermediate group in Table 1 less caries than the high-buffering group.
From a practical point of view the result in Table 1 indicates that the risk of caries should be reduced if the content of buffering substances in the low buffering group could be increased, whilst a lowering of this in the high-buffering group should reduce caries in that group.
Fluoride Reduces the Critical pH Level
If there is fluoride deficiency in the mouth, the tooth enamel looses minerals when the pH value has dropped to less than 5.5 after eating. A low-buffering person very often has a lower pH value after eating than a person with higher buffering. If fluoride is present the critical limit is reduced to 4.5. In the pH interval 4.5-5.5 the enamel is certainly demineralised first, but afterwards a precipitation of fluorapatite occurs, which compensates for the mineral loss and forms a surface that has high resistance to the low pH values.
Moderate pH Fall Promotes Formation of Fluoranatite
Above pH 5.5 the formation of fluorapatite is a slow process. pH is often at this level in persons who belong to the high buffering group. If the pH on their tooth surfaces is reduced from 7.0 to 5.0, the rate of formation of fluorapatite rises 20 times (ref. 2).
Large pH Fall Prevents Formation of Fluorapatite
If the pH falls below 4.5 a constant mineral loss occurs and fluorapatite is not formed without the presence of a very high fluoride concentration and the longer this low pH value exists, the greater the mineral loss becomes. Person
Eklund Bengt
Wikner Sune
Care Aid 2000 AB
Merchant & Gould P.C.
Rose Shep K.
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