Premolar approximal anatomy

The reconstruction of the original anatomical structures is very important, also in the approximal region. Direct composite restorations are a well established treatment option for the restoration of posterior teeth. With todays modern materials, the size of the defect is less of a limiting factor, longevity and good marginal seal can be achieved.
To be able to do this, some must control a few crucial factors.
The proper knowledge about anatomy and function is indispensable.
Modern tools help to predictably reconstruct approximal walls. The configuration and also the position of the approximal contact is important for functional reasons and to avoid and damage to the gingival papillae.
Finally, we need proper materials and incremental layering techniques to have a good marginal seal and proper occlusal anatomy.

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Fig.1
Initial situation of failing amalgam fillings in teeth 14 and 15. You can notice some typical anatomical features of premolar teeth.
1. The approximal contact point is located on the vestibular side.
2. The approximal surfaces palatal from the contact points are rather flat and divergent.
3. Thick marginal ridge areas.
All these features are not a coincidence, they all have a functional importance.
As a result of approximal wear, the contact area gets bigger and the position of it more palatal.

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Fig.2
Rubber dam isolation is placed right after anesthesia. It is important to check the approximal areas with floss, to make sure the dam can be passed through contacts easily.

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Fig.3
The necessary tools to restore approximal surfaces. It is really important to use them properly.

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Fig.4
The role of the ring is to push the matrix against the tooth on the axial walls, and also very importantly, to separate teeth. This separation allows for the creation of a tight approximal contact point. There are several types of rings available. There is no clear winner however, all types of rings have their respective advantages and disadvantages. Sometimes, even the pre-formed or anatomical rings are not able to shape the approximal surface, and also, they can make gingival adaptation of the matrix difficult.

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Fig.5
A custom ring is created before removal of the old restorations, as described by J. Manauta. This toll helps us to recreate the original approximal anatomy, especially on the palatal side.

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Fig.6
After this, the old restorations are removed, and the cavities are cleaned. It is important to properly finish the margins for a perfect adhesion. In this case, the cavity borders are completely in enamel. The bonding procedures are performed next.

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Fig.7
To ensure a tight approximal contact between the premolars, it would be an option to create the restorations separately, finishing the first, and start the bonding procedures for the second only afterwards. This however takes significant amount of time.
The custom ring, proper matrix and wedge selection enables me to create perfect approximal anatomy and start to layer both restorations at the same time.
On the buccal side, the custom part is not used. The leg of the ring is on the mesial side of the wedge, pushing the wedge further distally and ensuring a perfect gingival seal at the second premolar.
The mesial side of the second premolar is then built up with enamel-like material, transforming the cavity to a Class I.
It is important to build the marginal ridge to the right height. Observation of adjacent structures and proper matrix choice can help in this.

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Fig.8
After this, the distal matrix is removed, and the end of the ring is repositioned to the distal side of the wedge, creating a good marginal seal at the gingival box of the first premolar. This tooth is also transformed to a Class I, and I can create the approximal contact with only a single thickness of matrix in place.

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Fig.9
Ring and matrix are removed and I can finish the sculpting and layering procedures in a relaxed environment.

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Fig.10
The finished restorations before the finishing procedures. I did not use any stains in the fissures, for a more youthful appearance.

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Fig.11
After finishing and rough polishing of the restorations. If you can create proper anatomy, only minimal adjustments will be needed.

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Fig.12
Immediately after removal of the rubber dam, polishing and occlusal check.

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Fig.13
1 month recall. Teeth 24 (OD), 25 (MOD) and 26 (MO) were restored with the same method. 16 will be restored next along with the anterior sextant.

Conclusions

When restoring Class II cavities, the aim is not to simply create an approximal contact, but to restore the contact to the original anatomical location and shape. With modern materials and smart techniques, all these requirements can be fulfilled easily and repeatable.

Bibliography

1. The centripetal build-up for composite resin posterior restorations. Bichacho N. Pract Periodontics Aesthet Dent. 1994 Apr;6(3):17-23; quiz 24.
2. Longevity of restorations in posterior teeth and reasons for failure. Hickel R, Manhart J. J Adhes Dent. 2001 Spring;3(1):45-64.
3. Fabianelli A, Sgarra A, Goracci C, Cantoro A, Pollington S, Ferrari M. Microleakage in class II restorations: open vs closed centripetal build-up technique. Oper Dent. 2010 May-Jun;35(3):308-13. doi: 10.2341/09-128-L. Erratum in: Oper Dent. 2010 Jul-Aug;35(4):487

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