Decoupling with Time (DWT) in Biomimetic Dentistry, Explained

The problem: shrinkage stress versus a maturing bond

When a composite restoration is light-cured it shrinks. If the cavity walls restrain that shrinkage, stress is transferred to the adhesive interface. Davidson and colleagues described this as a competition between the developing bond strength to dentin and the contraction stress of the composite: if the stress wins, gaps form, which can lead to sensitivity, leakage and recurrent caries.

The stress is highest in cavities with a large bonded-to-unbonded surface ratio (a high configuration factor, or C-factor), as Feilzer and colleagues showed.

The hierarchy of bondability

Not all tooth surfaces bond equally well. Enamel provides the most reliable adhesion; superficial dentin bonds less well; deep dentin, near the pulp, has more and larger tubules and a wetter surface and is the most difficult substrate. Biomimetic protocols describe this ranking as a hierarchy of bondability and use it to decide the order in which surfaces are bonded and restored.

The DWT principle

Decoupling with time applies the hierarchy to the clinical sequence. The deepest, weakest bonds are made first and protected: the dentin is sealed, then covered with low-stress increments. Placement of the bulk of the restoration, and especially the layers that connect opposing enamel walls and generate the most stress, is delayed until the dentin bond has had time to develop. The result is that the stress arrives after the interface is better able to resist it.

In indirect restorations, immediate dentin sealing achieves a similar decoupling: the dentin is bonded at the preparation appointment, days or weeks before the restoration is luted.

Applying DWT in a direct restoration

1. Complete caries removal according to the peripheral seal zone concept.
2. Seal the dentin with the adhesive system and light-cure.
3. Place thin, low-stress increments over the deep dentin first, avoiding contact between opposing walls.
4. Allow time for the dentin bond to mature before placing the high-C-factor layers.
5. Build the enamel-bonded layers last, typically one cusp at a time.

Clinical considerations

• DWT adds chair time; it is most valuable in deep, high-C-factor cavities where the dentin bond is most at risk.
• Isolation must be maintained throughout the waiting period, since contamination of an uncovered adhesive layer defeats the purpose.
• Low-stress increments over deep dentin should be thin and bonded to as few walls as possible.
• Combine DWT with correct caries-removal end points and a well-executed adhesive protocol; sequencing cannot compensate for a poor bond.

Frequently asked questions

References

1. Davidson CL, de Gee AJ, Feilzer A. The competition between the composite-dentin bond strength and the polymerization contraction stress. J Dent Res. 1984;63(12):1396-1399. Find on PubMed (opens in a new tab)
2. Feilzer AJ, De Gee AJ, Davidson CL. Setting stress in composite resin in relation to configuration of the restoration. J Dent Res. 1987;66(11):1636-1639. Find on PubMed (opens in a new tab)
3. Alleman DS, Nejad MA, Alleman CDS. The protocols of biomimetic restorative dentistry: 2002 to 2017. Inside Dentistry. 2017;13(6):64-73. Find on PubMed (opens in a new tab)
4. Magne P. Immediate dentin sealing: a fundamental procedure for indirect bonded restorations. J Esthet Restor Dent. 2005;17(3):144-154. Find on PubMed (opens in a new tab)
5. Van Meerbeek B, De Munck J, Yoshida Y, et al. Buonocore memorial lecture. Adhesion to enamel and dentin: current status and future challenges. Oper Dent. 2003;28(3):215-235. Find on PubMed (opens in a new tab)