When doing daily dentistry, we get lost in time management or in trying to create a nice anatomy, sometimes jeopardizing the outcome of other crucial aspects of a successful restoration. In fact, the reconstruction of peripheral walls has to be done sealing all external margins correctly, based on contouring anatomical markers to ensure correct anatomy of the cusps/marginal walls and ridges. It’s only as a last step that we can focus on the occlusal anatomy, based upon all the hard work that was put in sealing the deep margins, rebuilding a correct marginal ridge and a smooth internal cavity. For this last point the Essential Lines protocol is applied. The first two points may seem complex and are often overlooked, thus creating a very large grey zone on how to perform them.
This patient had lost already other teeth due to cracks under large amalgam fillings. Upon her own wish we scheduled to remove the fillings on these two premolars, assess cracks, and restore the teeth accordingly.
Observing the bitewing X-ray, margins seem very accessible and don’t need any special attention. Only on the second premolar a deeper margin can be suspected.
After removal of the amalgam restorations, it is clear that a lot of unsupported enamel, which needs to be removed during the refinement of the preparation, is still present. The C-shaped cavity has a high susceptibility to leakage. Furthermore, margins are not located in the cleansable area.
The cavities are further cleaned and the margins are further crispened. Cervical margins are all in the wedge area. Buccal and palatal margins are in the cleansable areas. The cavities are sandblasted to thin out the smear layer on the dentin since a Self-etch adhesive will be used.
A thin liner of flowable composite (Filtek Bulk Flow U) is applied in the cavity and spread over the dentin to protect the hybrid layer. The thin tip allows to produce less air inclusions and to directly spread the flowable material over the surface without the use of a secondary instrument risking to include more bubbles.
After having completed the adhesive steps, a sectional matrix is placed on each cavity to get the tightest contacts possible. Stacking rings could result into weaker contact points and is therefore not recommended. In this case we want to be sure to create strong contact points. This has proven to minimize the chance of infiltration and food impaction. Therefore a wooden wedge and strong separation ring are employed (My Ring Forte, Polydentia). The matrix is not a thin one, because these are too flimsy to ensure a good fit and positioning. The black contrasting matrix (Lumicontrast 6,5mm x 0,04mm, Polydentia) ensures a good view on the margin and enhances the placement and general fit of the matrix to the interdental defect.
Without removing the wedge, only the matrix is removed and the next one is placed in the adjacent interproximal lesion. The same ring is employed for this interdental lesion.
Interdental walls are filled using the snow plough technique. A drop of flowable composite is disposed at the intersection of the margin and the matrix. The drop is dispersed over the whole length of the interproximal margin and not cured. It will serve as a lube for the paste composite to be guided into the narrowest parts. Also it will fill up the gaps that would include air without having it there.
With the second marginal wall built up, the first tooth is now turned into a simple class I and the matrix can be placed in the last interdental defect. Placing the matrices from mesial to distal ensures that on the last placement, less teeth have to be pushed away (5 separated form 6 and 7 vs. 3 separated from 4,5,6 and 7).
Another view of the fitting of the Lumicontrast matrix on the margin of the interdental defect of the second premolar.
Let’s recap from the distal marginal wall of the first premolar. After injecting the paste composite on top of the flowable composite, we find ourselves in this situation.
To further ensure the adaptation of the composite and it flowing into every small space, a condensing instrument is used to compress the paste (LM Arte Condensa Dark Diamond, LM Dental). It’s anti-sticking coating works wonders when packing composite, and ensures to keep the condensed composite in place without pulling it back when removing the instrument.
After condensing the excess paste composite is pushed coronally, above the matrix.
After condensing the paste composite an excess is created on the occlusal of the matrix.
When possible, the excess is shaped in the exact same height as the neighboring tooth, using the LM Posterior Misura. The fork-like end is placed with one side on the neighbors’ marginal ridge whilst the other is shaping the composite. Using a scoring motion, the instrument is moved from buccal to palatal sides.
Not all of the excess is removed and still needs some refinement, but the important thing is to not change the height of the ridge from this point on.
The sharp edges can be rounded off and final adaptation in the bottom of the cavity can be done with a small microbrush.
All Marginal ridges have been constructed. Having copied the height of the neighboring teeth, looking from the buccal, the restorations already look finished.
The deepest parts of the boxes were filled with a dentine shade composite, leaving us with two simple class I cavities to fill up using the Essential Lines Technique.
The same protocol is applied to the second premolar and the fissures were filled with a mixture of stain (GC Optiglaze Red Brown) and flowable composite (Filtek Bulk Flow Universal, 3M). Since the build up and layering was done precisely, only simple finishing steps will prelude the polishing, saving time on the total restorations.
Just as for anterior restorations the finishing is done with discs on the outside, refining the interproximal margins and marginal walls.
Followed by a slow, diamond coated bur on the inside of the occlusal plane, smoothing out any defects that might have been incorporated during shaping.
The final polishing spiral is used to enhance gloss.
The occlusal view of the finished restorations can be appreciated.
Palatally inclined view of the final restorations.
Final view palatally inclined.
Having put time and effort on every part of the restoration, checking the occlusion in the end should be quite rewarding. Marginal walls were created following the neighboring teeth in occlusion, whereas the essential lines protocol relies on the remainder of the tooth to shape a proper occlusal table. Occasional high points will therefore always be located on the cusp ridges or marginal walls which are easy to adjust without destroying the occlusal anatomy.
A posterior restoration stands or falls on three large pillars:
- The proper preparation of the cavity and proper allocation and refinement of the margins;
- Simplifying the difficult cavities into easy ones. Meaning that first cusps should be rebuilt, followed by marginal walls, thus completely recontouring the tooth;
- Filling the occlusal using a simple, predictable and repeatable protocol. Essential lines follows predominant anatomical markers still present on the tooth or created during the build-up process, therefore, rebuilding the tooth in a natural way ensuring its shape and function.
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- Akhundov M. Working with LM Arte Posterior Misura. 2017. www.styleitaliano.org
- Cho VY, King NM, Anthonappa RP. Role of Marginal Ridge Shape and Contact Extent in Proximal Caries Between Primary Molars. J Clin Pediatr Dent. 2021 Apr 1;45(2):98-103.
- Peumans M, Venuti P, Politano G, Van Meerbeek B. Effective Protocol for Daily High-quality Direct Posterior Composite Restorations. The Interdental Anatomy of the Class-2 Composite Restoration. J Adhes Dent. 2021;23(1):21-34.
- Hardan L, Sidawi L, Akhundov M, Bourgi R, Ghaleb M, Dabbagh S, Sokolowski K, Cuevas-Suárez CE, Lukomska-Szymanska M. One-Year Clinical Performance of the Fast-Modelling Bulk Technique and Composite-Up Layering Technique in Class I Cavities. Polymers (Basel). 2021 Jun 4;13(11):1873