Management of Short Clinical Crown

---

A rare clinical situation is when a patient needs a crown and there is not enough height or tooth structure for the crown to stay in place.

For this reason, SCC (Short Clinical Crown) is not always managed properly by the dentist.

SCC is described as any tooth with less than 3 mm of sound, opposing, parallel walls after occlusal and axial reduction.

Some common causes of SCC include caries, erosion, dental malformation, trauma, iatrogenic factors (excessive tooth preparation), and insufficient passive eruption, among others.

These cases are not easy to treat; a simple clinical examination is insufficient. A radiographic examination and analysis of the case on a study model are necessary.

These are some important considerations that we, as restorative dentists, must take into account before intervening, and upon which a series of decisions and tools we must implement will depend.

- Consider the tooth's position in the arch.

- Strategic value of the tooth.

- Periodontal considerations.

- Crown-to-root ratio.

- Interocclusal space with the antagonist.

- Feasibility for root canal treatment.

- Esthetics.

When faced with cases that deviate from the norm, we must think outside the box and use tools that allow us to ensure the success of a treatment. Here I detail a list of 8 points in chronological order that I use in my practice when I encounter cases of SCC:

1- Modify the tooth preparation design:

The retention and strength of fixed prostheses are primarily related to the crown length, degree of occlusal convergence, and axial surface area—in other words, the abutment height and the degree of inclination of the preparation walls.

Secondary retention and resistance to dislodgement are achieved by creating grooves and recesses in healthy tooth structure. These grooves, 1 mm deep x 1 mm wide, allow the prosthesis to remain in place longer.

It is crucial to be very clear about which surfaces of the preparation should have these grooves or recesses.

In the case of single crowns, the grooves or recesses should be made on the proximal surfaces (mesial and/or distal) of the preparation. This is because the rotational/dislodgement force in single crowns is typically directed palatally/buccally or lingually/buccally.

In the case of a bridge, the grooves or drawers should be made on the lingual and/or vestibular surfaces of the preparations since the “tipping force” that causes the prosthesis to become dislodged is directed along the proximal areas.

2-Placement of Reconstruction Materials:

Primary retention must be provided by healthy, solid tooth structure. Reconstructions or "core build-ups" should not be relied upon for this purpose because there is no guarantee of the material's retention quality.

Although this option is not always feasible, for example, in cases where interocclusal space is extremely limited, it is still a helpful tool and, as such, should be considered.

3- CAD/CAM-Designed Restorations

Remember that traditional "handmade" restorations use a spacer on the plaster model. The metal coping is waxed onto this spacer and then cast. This spacer is brushed by hand, resulting in an irregular thickness. Furthermore, it penetrates the grooves created for secondary retention and "blocks" them, eliminating much of the groove's anatomy and depth. Thus, when the metal coping reaches us, it doesn't extend sufficiently into the grooves, negating the purpose of creating them.

CAD/CAM-designed crowns produce perfectly regular spacing because they are computer-controlled and can more accurately replicate the modifications made to the preparation.

4- Monolithic Restorations

Regardless of whether the chosen material is metal or zirconia, monolithic restorations require more conservative preparations to achieve the necessary strength to withstand masticatory forces. In contrast, porcelain-fused-to-metal crowns, for example, require more extensive abutment preparation to obtain the ideal thickness since they are fabricated in several layers.

Typically, 0.5 mm of occlusal reduction is sufficient, thus preserving as much tooth structure as possible.

5- Subgingival Margin

Although it remains an option for obtaining a larger retention surface for the prosthesis, great care must be taken with this type of preparation.

I believe the advantages of a slightly subgingival preparation are obvious, so I want to focus on the risks of this option.

Invading the biological width during preparation can result in chronic inflammation that will compromise aesthetics, as well as alveolar bone loss, gingival recession, and periodontal pocket formation.

Furthermore, subgingival margins make it difficult to position the preparation, compromise the maintenance of the provisional restoration, make taking the impression difficult, make it difficult to evaluate the fit of the definitive restoration and, as if that were not enough, the isolation at the time of cementation, in addition, by extending the margin very subgingivally it is prone to retaining excess cement at the margin.

6- Cement to Use

Choice of cement is ALWAYS very important in all cases, and this is no exception in the case of short crowns.

Resin cements provide better bond strength, so when I have a short crown, I immediately set aside glass ionomer cements and focus on resin-modified ionomers or, ideally, dual-cure resin cements. These cements not only provide greater retention strength but also offer greater predictability.

7- Orthodontic Eruption

This treatment is a tool that is rarely used by dentists, and in most cases, it's for one simple reason: time.

This valuable tool is currently used in implantology cases, where tooth traction will produce more bone and soft tissue. Even so, as restorative dentists, we must realistically plan what is best for the patient, regardless of the time it takes.

The objectives of this treatment include bone conservation, preservation of the biological width, exposure of healthy tooth structure for the new restoration margins, and maintaining esthetics.

8- Clinical Crown Lengthening Surgery

If the restorative dentist determines that there is insufficient healthy tooth structure available for the restoration and decides to use this technique, it is important that they understand the concept of biological width, as well as its indications, techniques, and other principles, such as the crown-to-root ratio.

When the biological width is violated, a defense mechanism is triggered, and an inflammatory response leads to alveolar bone resorption in order to provide space for new junctional epithelium, resulting in a deep periodontal pocket.

I hope you find this information useful, best regards!

Dr. Marvin