Posterior resin infiltration and direct vision
The infiltration technique we’ve been talking about might actually be a great way to stop interproximal incipient caries in a non invasive way. Posterior resin infiltration requires direct vision of the proximal lesions of the enamel. These kind of lesions before cavitation, the initiation of the caries process, is characterized by a subsurface white spot formation, with a overlying almost intact surface.
Once a tooth is cavitated because of a caries, the lesion tends to progress. (5)(6) So ideally before having a cavitated lesion some kind of intervention should be done: to invert the process of demineralization to a remineralization, or, at least, to stop the demineralization process.
Remineralization of white spot lesions with an intact surface is possible. The lesion can be stopped and we can rely on calcium and phosphate ions. The use of topical fluorides to enhance remineralization of demineralized proximal enamel has been advocated (7). For example one of the protocols that demonstrated some benefits is the application of fluoride varnish every third months. It significantly reduces the progression of proximal caries lesions in premolars and molars. The most obvious reduction of caries progression is observed among children with moderate caries risk, while children with high caries activity (more than 9 new proximal lesions) do not benefit from proximal caries reduction. (8)
Cavity preparation is nowadays considered destructive and outmoded in incipient proximal lesions because another less invasive techniques are possible.
A considerable number of professionals still tend to practice invasive techniques with lesions confined to enamel ranged from 19% to Norway (Tveit et al) to nearly 50% in Mexico and Brazil (Traebert et al).
The resin infiltration technique in interproximal caries lesions is a less invasive technique compared to a cavity preparation and fits in the concept of minimal intervention dentistry.
THE INFILTRATION TECHNIQUE
The infiltration technique should be an alternative to cavity preparation, thus at least postponing (if not avoiding) sacrifice of sound structures.
Resin Infiltration technique is contraindicated in cavitated lesions but instead is a treatment option in non cavitated incipient (interproximal) enamel lesions.
The problem in posterior teeth is the bitewing radiograph does not give any direct information on the surface integrity of proximal lesions.
Clinical studies (Bille et al) found comparably few cavitations in R3 lesions (radiolucency reaching the outer dentin on bitewings) lesions (22% to 52%), while several laboratory studies confirmed a considerably earlier cavitation with breaking of surfaces in up to 100% of R3 lesions (Kielbassa et al).
The best condition should be to have direct vision to the tooth to be able to verify the presence/absence of cavitation and to be able to check the activity/inactivity of the lesion.
In this article we explain a tip that we use in our daily practice to achieve the direct vision to the lesions in the case of interproximal lesions.
The incipient caries lesion mesial to the first inferior molar has easy access because the second premolar is not completely erupted. The white and brown spot means that we have demineralization in that area. Fluor and casein approach is useful in very superficial incipient caries which is not the case. In case remineralization with fluorides is not considered a viable approach the resin infiltration technique is an alternative. The resin infiltration is well accepted technique because it is less invasive than the conventional approach with a bur cavity preparation.
The retraction cord (Ultrapack number 3 by Ultradent) inside the sulcus helps to completely expose the lesion.
The lesion is now fully visible and ready to place the dental dam
In that particular mixed dentition situation the single tooth isolation with the dental dam is the best solution.
Usually we use the 27N clamp for molars.
After cleaning the surface from any possible debris or dental plaque we apply the hydrochloric acid (HCL) according to the Icon instructions for the resin infiltration, for 120 sec.
We rinse with water spray to remove the etching for 30 seconds.
The first mineralized layer is destroyed by means of the etching and now the demineralized area is accessible. We place the alcohol (alcohol included in the Icon kit) and let it set for 1minute at least, which is considerably more than the manufacturer suggest. This procedure has the solely purpose of giving a preview of how the infiltration would look like at that point.
As the lesion was still visible after alcohol application we repeated the steps (etch and alcohol) for 4 times. The aim of repeating 4 times the procedure is going deep into the lesion. If after repetition of these steps you see that the lesion is still visible you can think of combining Icon with some micro or/and macroabrasion. The microabrasion was done with the Oxide Aluminum 50 micrometers a 2 bar pressure for 10 seconds 1 cm away from the tooth.
Most of the demineralized tissue disappeared fast thanks to the abrasion. Two small white spots are still present.
When applying the Icon alcohol we can appreciate the small white spots still present disappear completely.
Resin infiltrant was applied. We let it set for 2 minutes and then we light cure.
In the cases where there is a depression usually due to micro or macroabrasion or too much structure loss, a small amount of composite enamel should be applied. Resin infiltrants can be combined with conventional resin restorations in case needed.
Finishing and polishing steps are mandatory in the resin infiltration technique with or without adjunctive composite.
The case just after cord and dental dam removal
Control appointment 2 weeks after.
Unfortunately the posterior caries are not usually accessible. Posterior caries are usually in the contact point area and not visible. Resin infiltration technique is contraindicated in cavitated lesions. The problem is that with bite-wing radiography we are not able to establish if the lesion is cavitated. That´s why in our protocol we find convenient to place an orthodontic elastic (Ormco elastics) in the interproximal area, 5 days before the appointment with the main goal of opening the space and in this way be able to perform the right treatment.
Space created with the orthodontic elastic is enough to have direct vision to the lesion.
Dental dam in place. Buccal and vestibular demineralization.
We removed dental plaque from the surface of the lesion with a small brush and prophylactic paste.
We can also clean with dental floss (Superfloss)
The wedge squeezes the papilla and pushes down the rubber dam and gives the extra separation space.
This appliance (approximal tip) inserted in the syringe (Icon etching) lets the etchant to be applied in the proximal area that we want thanks to a permeable membrane only in one side while the other side is protecting the wall that we don´t want to etch.
We rinse with water spray for 30 seconds.
With the icon dry syringe we applied a good amount of material onto the lesion and let set for a minute at least.
We plan to repeat the icon etch and Icon dry steps as we were not satisfied with the preview with the alcohol
HCl application following the instructions
After three applications of Icon etch and icon dry we decided to infiltrate.
Resin infiltration with the proximal tip. The material will dispense only on the green side of the proximal tip
Using infiltrants with high penetration coefficients as it is Icon etch (penetration depth 60 micrometers) facilitated inhibition of lesion progression, thus showing that resin infiltration sufficiently occludes the acids’ pathways and hampers demineralization.(Meyer-Lueckel et al)
The physical barrier is expected to give a protective function against exposure of acids from bacterial origin, and cutting off possibly remaining bacteria (within an advanced lesion) from a nutritional supply of fermentable carbohydrates. (Gomez et al)
Check ups of the lesions should be performed. We expect reduced or inhibited caries progression.
Resin infiltration technique with Icon is a treatment option in incipient interproximal enamel caries. One limitation of the resin infiltration concept is that in interproximal posterior enamel lesions with a bitewing radiography is not possible to evaluate the presence of a cavitation. In cavitated lesions Icon is contraindicated. Neither another method like photoillumination lets you determine the integrity of the outer part of the lesion. Thats why in our protocol in interproximal caries with a contact point we open the space with an orthodontic elastic 5 days before the appointment. With the direct view we reevaluate the lesion and take the decision how to proceed to treat the caries lesion.
Note: All the cases from this article were performed together with Dr. Elisa Oneto, Chiavari, Italy