Minimal intervention Dentistry

The Site 2 lesion is the result of plaque accumulation at or just below the area of contact between two teeth.
Like the depths of fissures this is a logical area for the accumulation of plaque and it is difficult to clean.
A tooth brush alone will never be fully efficient so the emphasis over recent years has been on the use of dental floss to at least disturb the plaque and prevent it from maturing.

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		Because teeth are constantly moving against each other during mastication or clenching and grinding there will be little or no plaque at the actual contact area but it is the semi-circle immediately gingival to the contact that is most susceptible. This is a quiet area not subject to disturbance and, once the pH of the mature plaque drops below 5.5, demineralisation will commence and a white spot lesion will form. As discussed elsewhere this begins as a sub-surface lesion and is likely to progress into both teeth at a steady pace until, or unless, the disease is eliminated. It is generally not possible to see the lesion and there will be some degree of penetration before it is clearly visible on a radiograph.
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However, as it is not subject to masticatory load or disturbance to the surface it may well be possible to remineralise and heal the lesion even after the demineralisation has reached the dentine.



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However, there will come a time when the surface is so demineralised that it will begin to collapse and a surface cavity will form.
From this point bacteria can accumulate directly in the cavity and it will no longer be possible to clean the teeth and arrest progress.
It will now be necessary to invoke some form of surgical procedure to eliminate the cavity and make the surface smooth again.

This does not mean that it is necessary to remove all tooth structure that shows signs of demineralisation.

Providing the original framework of either the enamel or the dentine is still present it is possible to remineralise those areas and, if the surface is smooth, then bacterial plaque will not be able to accumulate again and, providing the disease has been controlled, further demineralisation is unlikely.

As discussed elsewhere, control of the disease with elimination of the bacteria is of paramount importance before making decisions on the need for, and the extent of, surgical intervention. It is apparent that proximal lesions, under normal circumstances, progress (Ref. Pitts NB) reasonably slowly.
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It may take up to four years to traverse the full depth of the enamel and a further four years to reach the pulp through the dentine.
This suggests that the early lesion that has not penetrated through the enamel probably has no surface cavitation and is therefore susceptible to healing through remineralisation.
However, any progress beyond that should be examined carefully for evidence of cavitation before surgical intervention is warranted.
For the younger patient it is often possible to obtain separation between the teeth through the placement of an orthodontic rubber band for 48 hours.


figure7	Then take a rubber base impression of the interproximal space and evidence of cavitation will be apparent. Having determined the presence of surface cavitation it is then necessary to decide the best approach to carry out repair. When dealing with a new lesion one of the primary
	objectives should be preservation of the integrity of the tooth crown. The great weakness of the GV Black system was that the preparation of a cavity to deal

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with a proximal lesion leads inevitably to the divisionof the tooth crown in to two parts through removal of the marginal ridge. This leadsto cusps splitting (Ref. #4, Chapt 10, p154) at the base and a continuum of restorations up to the stage of full crown.


		Careful attention to detail suggests that this is not entirely necessary and cavity designs can be modified to avoid wholesale destruction. This classification is designed to identify lesions and it is not intended to prescribe cavity designs.
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However, it would seem desirable at this point to suggest possible variations in the approach to the repair of proximal lesions and to offer some key indicators that may assist in decision making.

It is suggested that there are at least three primary variations in dealing with a proximal lesion as follows:

Tunnel	Slot or Box	Proximal
> 2.5mm below crest of marginal ridge	< 2.5mm below crest of marginal ridge	Through adjacent large cavity


figure11		Tunnel – In this situation the lesion is more than 2.5mm. from the crest of the marginal ridge. It is possible that the remaining proximal enamel is sufficiently strong that it can be retained and a tunnel cavity designed with safety. Retention of the marginal ridge is desirable to maintain the intrinsic strength of the circle of enamel that is the crown.

figure12		Slot – In this case the lesion was closer to the crest of the marginal ridge than 2.5 mm. So if a tunnel had been designed the marginal ridge will almost certainly fail. A slot design is therefore the best choice. However, there is no need to extend the cavity laterally beyond the enamel that is too broken down to be remineralised.

figure13		Proximal approach – This is a rather unusual design because access is dependent upon the presence of a rather large Size 3 lesion in the adjacent tooth. Though unusual it is very conservative of tooth structure and will lead to preservation of the marginal ridge.

As suggested above this is not meant to be exclusive because there are many variations possible and these will often depend upon the relative position of teeth to each other and therefore the position of the contact area.

It is acknowledged that about 75% of restorative dentistry carried out on a daily basis is “replacement dentistry” and the above discussion does not apply in any way to that.
Once a cavity has been cut in a tooth there is no way of going back so the ultra-conservative designs discussed above no longer apply.
However, it is still possible to apply some of the principles of minimal intervention dentistry to replacement dentistry.

The primary principle of course is elimination of the disease before undertaking definitive replacement. Then, in designing the cavity, recognise that “extension for prevention” is no longer required. Preserve as much natural tooth structure as possible but be prepared to offer protection from occlusal load to weakened cusps to avoid the developments of splits at the base.

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