Bonding to new calcium silicate materials – a highway to hell?

Bonding to new calcium silicate materials – a highway to hell?

For the past 50 years, the face of restorative dentistry has totally changed. Numerous innovations have come up and modified the way dentists take care of teeth.

The first big change was the launch of light-cured acrylate composites and their related adhesives. Back in the early days of adhesive dentistry, bonding was quite a challenge. The outcome was relatively problematic and unpredictable.

To be honest, these bonding procedures were challenging for practitioners. First, the procedure itself was very complex. Many different products to use in a specific sequence (etchant, primer, mixing bonding A with bonding B), rinsing, light-curing and drying – but without dehydrating – steps in-between.

On top of that, the bonding values could be completely uneven, bonding values could vary from one dentist to another, and for the same dentist, from one tooth to another, showing that the effectiveness of the bonding was operator dependent as well.

This is when the second big change occurred: the launch of self-etch adhesives. To overcome the difficulties linked to the dentin etching, the acidic level of the primer was increased, making conventional phosphoric acid etching unnecessary for dentin. It was a more dentin-friendly approach.

Calcium silicates: a different substrate to bond to

Biodentine shows a wide range of benefits. It releases calcium ions and calcium hydroxide, which will elevate the pH to contribute to remineralisation of the adjacent dentin. At the same time, it limits bacterial development as bacteria need an acidic environment to grow.

Studies have shown that Biodentine triggers stem cell differentiation to odontoblast-like cell that create tertiary dentin. It may feature anti-inflammatory properties explaining, therefore, the clinical observation of lower pain in patients.

Since it is a water-based cement, Biodentine doesn’t show any depth of cure limitation. It can fill a very deep cavity, eg a full pulpotomy in a molar, in only one single increment. It therefore allows to work faster, deeper while maintaining the pulp vital.

Hence the Biobulkfill concept, which represent another innovative breakthrough in restorative dentistry: Biodentine is placed from the pulp to the top of the cavity, regardless how deep.

Yet, the question remains: how to bond to Biodentine? It doesn’t have any organic parts – it is 100% mineral.

So, should Biodentine be considered as enamel and be total-etched? Or in the contrary, should it be considered as dentin – which is Biodentine claim – and be self-etched? How to make sure the bonding will be effective? Should we look at the bonding strength values only? Since Biodentine features a high pH, will it interfere with the acidic pH of adhesives?

Evolution cycle

The calcium silicate-based cements have an evolution cycle in their hardening of about one month. After one month, they will reach their final hardness. They can be considered as a 100% mineral material, just like enamel – but with a different hardness and wear resistance.

Right after placement in the tooth, they are still in their hardening process and care should be taken that nothing interferes with it or inhibits it; they therefore should be considered as dentin and receive less acidic treatments.

When used as a replacement for damaged dentin in a restorative cavity, Biodentine offers the possibility to receive the final composite restoration in the same session or in a subsequent session – if, for example, the pulp needs a few weeks monitoring.

So, if the final composite is bonded in the same session, a self-etch adhesive will be preferred,. This is because it is less acidic than a total-etch adhesive, and therefore will not interfere with the proper setting of Biodentine.

Studies have shown that when doing so, the bonding strength is similar to bonding to a glass-ionomer cement.

If the final composite is bonded to Biodentine in a subsequent session, between two weeks and six months, then either a self-etch or a total-etch procedure can be carried out.

In fact, a staircase to heaven

From a clinical standpoint, in deep cavities the need for Biodentine is obvious: the closer to the pulp, the higher it needs protection.

But Biodentine is not a passive protection as other dental materials. It is highly biocompatible with the pulp to maintain its natural defences, ie tertiary dentin and dentin bridges, against bacterial attacks.

Bonding a composite in a deep cavity where Biodentine, dentin and enamel are present, will clearly become easy, comfortable, and effective: patients will be pain-free, even happier than before, about their beautiful restorations and restored smiles?

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