“Restorations Microleakage”: a concept that should be vanished from dentistry

“Restorations Microleakage”: a concept that should be vanished from dentistry

Carefully considering what has been published on the durability of dental restorations in the past 20 years, and observing the different behaviors of dentists towards the evaluation of old restorations, there is one certain thought: our patients would be much better if we could get rid of concepts such as “restorations microleakeage” or “marginal microleakage”, that are usually associated with the development of secondary caries lesions (caries lesions adjacent to the margins of the restorations). These concepts are as harmful for the durability of restorations as the sharp explorers, used to verify the adaptation of old restorations by “catch”. Below, I will provide the bases for these assertions.

1. What you see is not a secondary caries lesion:

When we ask dentists what is the main cause of failure of restorations, secondary caries lesions are always the most cited, along with fractures. This is very interesting, considering that year after year the prevalence of caries drops worldwide, but nor the prevalence of secondary caries. Along with that, when we ask dentists to refer to us patients with secondary caries lesions, or to show us pictures of these lesions, nine in ten cases represent non active caries lesions or stained margins. Based on that, we can say that there is a great difficulty in diagnosing the actual secondary caries lesions. Starting from the beginning: what are the characteristics of an active caries lesion? An active caries lesion is the one that is progressing, the one that we have to worry about to avoid pain or pulpal damage, and the one which, if not treated, may cause tooth loss to the patient. These lesions are the ones, that when in enamel, are associated with a plaque retentive regions, that present porosity, usually presenting a rough, not shiny and whitish surface. When the dentin is involved, an active caries lesion is a humid, soft and brownish tissue, not resistant to mechanical removal with non rotatory instruments. Now some news to you: the characteristics from an active lesion do not change for the secondary caries lesions (adjacent to restorations); these are simple the same characteristics that should be observed for primary caries lesions. So look again and tell me: the lesion that you are seeing and diagnosing as secondary caries, is it really a secondary caries lesion? And if it is, is it active (is it progressing)?? And if it is, and it is restricted to enamel, do you think you need to intervene??

Now that we discussed the relevance of the activity of the lesion, let’s define what IS NOT Secondary caries:

1.1. Staining on the interface:

It has been more than two decades that clinical researchers showed that there is no relationship between the staining on the interface, or “marginal microleakage” and the presence of caries lesions. This staining may be due to several reasons, like the degradation of the adhesive layer, food staining, tobacco staining, among others. None of these factors is associated with secondary caries.


1.2. Small defects on the margins of the restorations:

Small defects along the margin of the restorations are a result of the time, specially on the occlusal surface of posterior teeth. The literature is not clear on what would be the dimensions of the defect so that it would result on a caries lesion, but there is a consensus that, for a lesion to happen in the interface, there should be a marginal gap of at least 100 μm, that allows the plaque to accumulate and the consecutive events necessary for the establishment of a caries lesion. The presence of gaps between the tooth and the restoration, with no signs of caries, does not characterize the presence of a secondary caries lesion.

1.3. Radiolucent images along the interface tooth/restoration:

A radiolucent image may indicate the presence of a residual non active caries lesions, or the presence of dental materials that are not radiopaque as, for example, adhesive systems. For that reason, it is of great importance to know the history of the patient. The right diagnose should be based on a thorough clinical examination, considering all the characteristics of an active lesion.

1.4.Residual caries lesions:

The secondary caries lesion can be confounded with residual caries lesions, that are just carious tissue that was left behind on propose when removing the caries lesion, aiming to avoid the pulp exposure. The differential diagnosis between secondary caries and residual caries lesion underneath restorations can only be made if the dentist knows the history of that patient. It is important to point out that partial caries removal procedures are very frequently performed nowadays and that we are able to detect clinically some shadow/darken areas around composite restorations due to the affected dentin tissue left behind during cavity preparation. This optical effect is an expected event, and means that the affected tissue left behind was re-mineralized and no longer presents itself as a soft caries affected tissue, so, biologically speaking, there is no need to intervene in these cases.

2. What we see clinically is not marginal leakage, but interface staining.

Marginal leakage is defined by the passage of ions, fluids and bacteria through the interface tooth/restoration. These tiny molecules and ions are always passing through the restorations’ margins, and it is virtually impossible to be able to achieve a restoration with no marginal leakage. Even with the aid of a clinical microscopy, it is impossible to visualize the ions and molecules, so there is no way to truly verify the marginal leakage clinically. Even if we were able to see the leakage, there is no way to prevent it to happen, even using the “best” materials and techniques. What is normally seen as a leakage is actually marginal or interface staining, that results from the degradation of the bonding agents or restorative materials. It can also be extrinsic pigmentation that attaches to the micropores of the restoration. One can think that these stains “leaked” into the margins of the restorations, but this is not actually something that we can avoid and is due to the aging of the materials that this phenomenon happens in the intraoral environment. The passage of organic acids through the interface tooth/restoration was detected in in vitro studies, and in extreme situations, as in cases of misplaced restorations, for example. Considering this, we could conclude that this acidic flow could end up causing caries lesions. But this theory still needs to be further investigated with clinical studies, and, as said before, it is probably associated with extreme situations.

3. Marginal leakage has no clinical significance

Following this line of thinking, we can not see nor prevent the marginal leakage. But we do not need to worry about that, since some studies showed that the marginal leakage per se has no clinical significance when considering the development of secondary caries lesions, or even to predict how strong the bond strength between the restorative material and the tooth actually is. What calls our attention is that there are still some researchers and professors that study the marginal leakage and even have their articles published, but that would be a topic for another post.

4. Interface staining matters only if it is in as esthetic region and if it is a concern of the patient

Obviously there are situations were the dentists should be concerned about the interface staining. When it happens in anterior teeth, staining usually are a major complaint of the patient because it compromises esthetics, and we always have to listen to what our patients say on what is bothering them. Our treatment should be focused on our patients’ concerns. However, we must be prepared to explain to our patients when they have illogical complaints, that should not be treated. For example, small stains on molars. The dentist must educate their patients about the lack of need on treating this kind of situations, explaining that they are inherent of the restorative materials and techniques, and that, even if the restoration is replaced, within the years, chances are that the new restoration present the same kind of staining.

5. We need to redefine our esthetic parameters when dealing with posterior restorations

There is no doubt that one of the aspects that are most important when considering the longevity of restorations on posterior teeth is the opinion of the dentist about it, and the decision on what to do with an old restoration. It is important to point that any restoration, but specially the ones done using the direct technique, present signs of degradation with aging, like wear, marginal staining, among others. This way, it is expected that even composite restorations do not present the best esthetic features with time. Based on that, two thoughts can come to our minds: is it really necessary for our patients to have posterior restorations with perfect esthetic anatomic features? And if we decide to change an old restoration “for esthetic reasons”, as good as one could be on reproducing the anatomic features of a posterior tooth, for how long will this features really be present considering the intraoral environment as being as adverse as it can be for these restorations? This way, the more rigorous we are when judging the clinical aspects of an old restoration, probably the more unnecessary interventions we will make. We will end up replacing more restorations that actually would need to be changed, and as a result we will cause more damage to the remaining structure of the teeth. Restorations on posterior teeth must be functional. Apart from that, we should only intervene when real problems exist and considering the patients’ complaints. This way we will be promoting the best evidence based treatments.

6. If only we would be as kind when evaluating other dentists’ work as we are when evaluating our own, our patients would not be so over treated 

Still following the same line of thinking, we can note that we, dentists, have a tendency of performing really positive self-evaluations whereas being really critical when evaluating other dentists’ work (even when we do not realize that). This is normal and is part of our nature, and the feeling that we could have done better is always present. But again, in a rational point of view, even if we can do it better, we should always consider if it is really necessary. The more restorative procedures we indicate to our patients, the more unnecessary teeth wear we are causing and the more unnecessary treatments we are performing. An example of over treatment related to what was discussed above is to exchange esthetic restorations” on posterior teeth because of marginal leakage. This is very common in dentistry. But because of the lack of evidence of the benefits of this “treatment” to our patients, this kind of intervention is considered an over treatment.

Considering all the topics discussed above, we could say that concepts such as “restorations’ microleakage” and “marginal microleakage”, even though are present in dentistry, have no real clinical significance, and should be banned of our clinical practice. Certainly our patients will be less exposed to unnecessary interventions if we stop mistaking the concepts of interface staining and marginal leakage, and if we are able to define the clinical situations when the staining could really mean a problem to our patients. There is a lot to be studied about the development of secondary caries lesions, but the recent literature shows that these lesions are usually more prevalent in patients with active caries lesions or in patients considered to be at high caries risk. However, only in some specific cases the local factors as the presence of marginal gaps are associated with the development of secondary caries. Finally, we should always remember that based on the evidences presented by the literature today, the aspects that can influence the longevity of the restorations, apart from the decisions made by the dentists, are patient related aspects. Specially the social-economic level, the risk of developing new lesions, or the presence of bruxism or teeth grinding, that can negatively influence the longevity of restorations  . This highlights the need to perform really accurate and whole evaluations of our patients, and the fact that the interventions we make should be focused on our patients’ complaints and their needs, instead of on the technique or restorative material that we are going to use.


Maximiliano Sérgio Cenci, Ms, DDs

Federal University of Pelotas | Brazil


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van de Sande FH, Collares K, Correa MB, Cenci MS, Demarco FF, Opdam NJ Restorations’ survival: revisiting patients’ risk factors through a systematic literature review. Operative Dentistry 2016 in press

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My purpose is to help you gain autonomy through knowledge, facilitating the dentistry and communication. AND how do I do this?

I put myself in your shoed, I identify what is preventing you from being happy with your results and untie the knots by means of a simple and accessible language! I graduated from UNESP | Araçatuba; did my Master and PhD in Operative Dentistry at UNESP Araraquara | I am a Professor of Operative Dentistry at the Federal University of Pelotas | RS.


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