The direct Class II composite restoration is one of the most common restorative procedures in dentistry. Unfortunately, it continues to be a complicated, frustrating, and often unsuccessful procedure for many clinicians.
The placement of a successful Class II composite resin restoration can be compared to the construction of a three legged stool. To function, all three legs have to be made correctly, that is, be exactly the same length, located in the right position and strongly attached to the stool. In the case of an economical and successfully placed Class II composite resin restoration, the three challenges (legs of the stool) are: 1) achievement of a predictable contact; 2) no or minor post-operative sensitivity of short duration; and 3) access to a simplified, faster and easier placement technique that delivers a consistent high quality result.
Building up a tooth the biomimetic way resolves all these problems.
Reduce the C factor in such deep Class IIs.
Make use of thin layers of composite
A thin layer of composite (e.g. a layer of composite <1 mm in depth) should be placed over the Immediate Dentin Sealing (IDS) and Resin Coating (RC) layers. This thin layer of composite has a lower C-Factor as the ratio of bonded to unbonded surfaces is reduced.
The type of layering technique used
The 2004 paper by Nikolaenko et al. shows that the placement of composite in thin horizontal increments results in greater bond strengths than vertical or oblique increments.
By ensuring that different substrates are not connected too early while the dentin bond is maturing, the hybrid layer is able to form in a stress-free environment. This relates to the concepts of Hierarchy of Bondability (HOB) and Decoupling With Time (DWT).
Research by Bicalho et al. in 2014 confirmed that placing composite in increments, compared to bulk-filling, increases bond strengths between 100-300% depending on the thickness of the increments. The resulting residual stress produced during polymerization is transferred to the residual tooth structure and results in less stress being placed on the maturing dentin bond.
Stress-Reduced Placement of DME Layers
A Resin Coating (RC) layer should be placed over the Immediate Dentin Sealing (IDS) layer.
The second thin layer of composite is commonly placed using AP-X composite. A layering technique is used, with either thin horizontal increments or a peripheral layer which is deliberately not connected to the axial wall over the pulp, in order to allow time for the dentin bond over the pulp to mature.
After allowing time for the hybrid layer to mature, the peripheral wall is then connected to the axial wall.
At this point, the Biobase (BB) is formed. The Biobase is made up of the following layers:
The placement techniques above allow Decoupling With Time (DWT).
Ultimately, building a Class II restoration this way ensures longevity of the restoration and minimising post operative sensitivity. These are the major concerns a patient has while getting a restoration done which can be solved by doing it the right way.
Jackson, R. Class II composite resin restorations: faster, easier, predictable. Br Dent J221, 623–631 (2016). https://doi.org/10.1038/sj.bdj.2016.856