Adhesive reconstruction of tooth structure has become the new standard since the ’90s. In the posterior area, many cavities are located at the proximal zone due to how challenging it is for the patient to clean the area.
Whatever the size of the occlusal defect indirectly related to the proximal decay (i.e. requiring direct or indirect restoration), it is mandatory to use what was once called “a dentin substitute” in order to simplify the clinical procedure. The advantages to this approach are the following:
• Biological protection of dentin
• Optimization of cavity design to avoid undercuts (in case of indirect restoration)
• Elevation of deep proximal margins to avoid crown lengthening
Many materials have been proposed to fulfill biological and clinical requirements. Amalgam, glass ionomer, resin modified glass monomer, compomer, flowable composite, bulk composite, syringeable dual cure or chemical cure composite. All of the above have shown different behavior with both success and failure. Of course many parameters have to be taken into account to make the right selection (hygiene, cavity volume, presence/absence of enamel at the margin, ability to isolate with the rubber dam).
Today we divide materials into two main families:
• Resin modified glass ionomer, for patients with poor hygiene and deep margins with no enamel
• Dual cure composite for most of the clinical situation
This article will highlight the use of resin modified glass ionomer in a context of deep margin restoration.
A 47-year-old male patient came complaining of gum bleeding, which was attributed to a lack of contact point.
Existing restorations on 25, 26, 27 had been performed by myself 16 years earlier using a dual cure composite as dentin substitute, and indirect composite inlay/onlay restorations. The treatment plan proposed was replacement of the three restorations with 3 pressed ceramic restorations to reinforce the contact point.
After the removal of the existing restorations, some small infiltrations were noticed around the previous dentin substitute on 25 and 26. After cavity cleaning, margins were deeply subgingival, with no residual enamel in the proximal area.
So I decided to rebuild the marginal anatomy with a glass ionomer cement instead of a dual cure composite, as had done 16 years earlier (Luxacore dual, DMG).
Why? Four main clinical factors can justify our choice:
– Marginal integrity with no enamel show better results with the aging process
– Pure resin is more sensitive to the acidic environment in the proximal area
– Lower material stress during the chemical cure phase
– Natural adhesion to dentin
On the other hand, GIC have lower mechanical properties and resistance. The goal here was to lift the margin to make clinical procedures easier, faster and safer. Then a ceramic restoration would reconstruct 90% of the defect. For smaller defects, direct composite restoration are indicated.
Rubber dam and metal matrices were placed in order to achieve a perfect isolation of the deep margin, even if GIC are less sensitive to humidity. This step is crucial, because it represents the basis of restoration biocompatibility. A plastic wedge was firmly placed to push the metal beyond the deep margin, and avoid blood infiltration.
A simplified protocol of surface treatment was applied using polyacrylic acid during 10 seconds. Then, it was removed with a strong spray and the surface dried.
A glass ionomer cement (DeltaFill, DMG) was activated, vibrated and placed into a dispenser, and injected in the proximal area to cover the lower level of the cavity only, since it would have been useless in the upper part.
A 1-minute chemical curing period is mandatory to reduce material stress. Metal matrix, plastic wedge and rubber dam were then removed.
Inlay/onlay preparations were performed in order to offer to the material the required thickness.
The deep proximal margin wasn’t there anymore. Thanks to the dentin substitute we elevated the margin to a supra-gingival level to facilitate all the upcoming clinical steps (impression, temporaries and bonding protocol).
Ceramic inlay/onlay restorations were made of lithium disilicate.
The bonding protocol always starts with isolation, using individual dam to improve visibility and to make placement of the dam is faster (10-15 seconds).
Thanks to the new proximal margin access, there was no more bleeding, no retraction cord, so the whole bonding protocol was very smoothly executed.
After sandblasting of the surface, phosphoric acid is applied for 30 seconds.
After injecting resin cement inside the restoration, excess material was removed with a brush. Then Optrasculpt PAD was applied to guarantee the perfect fitting of the onlay. The biggest risk is thinking that, after placing the restoration and removing resin excess, the fit is good. The dentist needs to be aware that the viscosity of the resin cement may make the restoration slip from the prepared cavity, so that it doesn’t sit perfectly anymore. This is why we have to use an instrument to make the fit perfect.
Final view of the integrated restorations.
Adhesive posterior restorations represent the most common treatment in everyday practice. Simplification and standardization are crucial for the dentist, especially in this kind of procedure.
Today we can say that a practitioner should standardize the bonding protocol by using dentin substitute for reconstruction. Advantages provided by this approach are:
• Immediate dentin sealing (chemical and mechanical)
• No more post operative sensitivity
• Simplifying access to deep margin
• Speeding up the bonding protocol and placement of the rubber dam
• Creating a common platform for the 2/3 depth of the cavity for both direct and indirect restorations.
1. Magne P. Immediate dentin sealing: a fundamental procedure for indirect bonded restorations. J Esthet Restor Dent. 2005;17(3):144-54; discussion 155.
2. Sarfati A, Tirlet G. Deep margin elevation versus crown lengthening: biologic width revisited.
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4. Koubi S, Raskin A, Dejou J, About I, Tassery H, Camps J, Proust JP. Effect of dual cure composite as dentin substitute on the marginal integrity of Class II open-sandwich restorations. Oper Dent. 2010 Mar-Apr;35(2):165-71.
5. Koubi GF, Koubi S, Brouillet JL. The Composite Up Technique:a simple approach to direct posterior restorations. Ad in Op Dentistry 2001