A pivot tooth is a dental prosthesis designed jointly by the dental surgeon and the dental technician. It replaces a tooth whose root is sufficiently in good condition to accommodate a rod, usually metal, itself supporting a high part called the crown.
This pivot tooth can be made in two ways:
– In a single block stuck in the hollows of the root.
– In two parts: the stem, then the ceramic crown. This technique is more recommended as the system better dampens the mechanical stresses of chewing.
Why pivots tooth?
A pivot tooth is possible when the natural tooth is so damaged that its visible part, the crown, is no longer buildable with a simple inlay or a metal closure. It is therefore necessary to add an anchor on which will rest the crown. The main indications of a pivot tooth and a crown in general, are:
- Trauma or fracture too important for any other reconstitution
- Advanced caries
- Significant wear of the tooth
- Severe dyschromia
- Severe malposition of the tooth.
What is a crown?
The crowns are fixed prostheses that will cover the upper part of the tooth to restore their original morphology. They can be made on the remaining dental tissue (thanks to a preparation) or attached to a metal or ceramic “prosthetic stump”: the pivot, also called the tenon. In the latter case, the crown is not glued, but sealed to a pivot slipped into the root of the tooth.
There are several types of crowns depending on the indication, but also according to the aesthetic and economic gradient offered to the person requiring the installation of a crown.
Cast crowns (CC). Made by castings of a molten alloy, they are certainly the least aesthetic and the least expensive.
Mixed crowns. These crowns combine two materials: an alloy and a ceramic. In vestibular crowns (VIC), the buccal surface is covered with ceramic. In ceramic-metal crowns, the ceramic completely covers the tooth surface. They are more aesthetic and obviously more expensive.
Ceramic-ceramic crowns. As their name suggests, these crowns are entirely ceramic, otherwise very resistant. They are the most aesthetic and the most expensive.
The aesthetic criterion, however, is not the only criterion: the crown must meet the needs of the oral cavity. Metallic reconstitutions are still widely used despite their unsightly side: the mechanical properties and simplicity of realization in the laboratory speak for themselves! In the case of the pivot tooth, this crown necessarily associates with a false prosthetic stump fixed, screwed or placed in the root.
How it works?
When a tooth is damaged too much, as a result of a strong decay or a powerful shock, it is often devitalized to stop the progression of the infection and remove any sensitivity of the tooth. This essentially involves removing the nerves and blood vessels from the infected tooth and closing the channels.
If the tooth is only partially damaged, it is limeed to obtain a regular shape; it takes its imprint and sinks prosthesis metal or metal-ceramic.
But if the tooth is too structurally damaged, it is necessary to anchor in the root one or two pivots to stabilize the future crown. We speak of “inlay-core” to designate this false stump sealed with cement.
Two sessions are required to complete the operation.
The risks of the pivot tooth
To avoid when possible. The decision to crown the tooth by associating a root anchor is to be taken after careful consideration. The realization of the anchors is not without risks and causes a loss of substance which weakens the tooth. Indeed, contrary to a tenacious belief, it is not the devitalization of the tooth that would make it more fragile, but the loss of substance induced by caries or by surgical mutilation. When possible, the practitioner should therefore turn to a reconstruction of the tooth devitalized by a less mutilating crown and tend towards a maximum tissue economy.
The stall of the pivot tooth. Tissue loss due to anchorage of the pivots may result in less resistance to occlusion-related stress, increasing the risk of fracture. When this happens, the tooth comes off. While waiting for the appointment at the dentist (imperative!), It is advisable to replace it carefully after taking care to clean the root (a mouthwash and a dental jet are adequate) and the stem of the pivot. It must nevertheless be removed during meals to avoid swallowing: it is unlikely to withstand the tensions of chewing.
If your root has remained intact, a new pivot will be assigned to you.
On the other hand, if your root is infected or fractured, it will be necessary to consider the dental implant or the bridge.