Coronal-root restorations

1.  Definition and description:
   • Reconstruction by inlay-core or cast false stump is intended for devitalized teeth on which the placement of a fixed prosthesis is essential.
   • The inlay-core or inlay-onlay with a root post is composed of a core at the coronal part and a root part (the post).
2.  Indications:
   • Restoration of teeth with extensive decay, having a juxta or slightly subgingival limit and/or whose residual walls are insufficient to consider a crowded restoration.
   • Restoration of a tooth whose root canal anatomy is incompatible with a prefabricated post.
   • Restoration of a tooth with reduced volume.
3.  Contraindication :
   • when its implementation significantly aggravates the deterioration of the tooth compared to its initial state and goes against the principle of tissue economy, it is necessary to abstain.
   • The available crown height is insufficient to ensure the retention of a two-story construction.
4. Preparation of coronal-radicular anchors:

• Root canal preparation:
• The housing is flared at its entrance creating what is commonly called the connecting cone between the tenon and the coronal supra structure, this for a double purpose:
  • Strengthen the mechanical resistance of the post in an area sensitive to fracture.
  • Increase resistance to rational forces.
• The form:

The shape of the tenon must meet the following objectives:

-Tissue economy.

• The distribution of stresses along the root.
• The capacity to resist tensile or flexural stress.
• Ease of sealing or gluing.
• Allow re-intervention.
• Length:

It will be determined based on a certain number of references:

• The enamel-cementum junction.
• The bone level.
• The coronal height.
• Root length.
• Tensile strength increases with length.
• It is now accepted that the end of the post should be located approximately 5-6 mm below the anatomical apex, in order to preserve the apical seal of the endodontic obturation.

• The diameter:
  • Must be in agreement with the values ​​of dentin thicknesses encountered at the root level.
  • It should be surrounded by at least 1mm of dentin for mechanical safety reasons, it should not exceed 1/3 of the root width.
  • A large diameter considerably weakens the root and does not increase retention.

5-CLINICAL STEPS OF PREPARATION:

1.  Coronary reduction:

– Instrumentation:

-Cylindrical or cylindro-conical diamond tips mounted on turbines.

• Reduction of coronal height:

A clearance of the internal walls in relation to the axis of the post does not save dental tissue because to allow the insertion and good adaptation of the inlay-core, there must be no overhangs or concavities.

• External peripheral preparation:

• The cervical limit of the future crown must cover the entire RCR and be in contact with the dental tissue everywhere.
  • Decortication of the external axial faces:
• Will depend on the type of crown planned (metal or cosmetic); Once the preparation is complete, the thickness of the walls is checked: all areas less than 1mm are removed. SIZE OF THE VESTIBULAR BRIDGE.

Starting from a mesio-distal line passing through the center of the root canal, the vestibular part is cut in a gentle slope towards the gingival margin, down to a subgingival level of approximately 0.5 mm (flute beak cut).

2. Canal bore:

Canal widening can be done:

• Either using manual instruments (pins or rasps)
• Either using rotating instruments (drills)
• The two methods are most frequently combined

6-Taking the impression:

This involves first taking the impression of the root housing to receive the root post; then taking the location impression of the entire arch which includes the stump and finally the impression of the opposing arch.

A. Canal footprint:

The canal must be cleaned with alcohol and then dried, lubricate it with Vaseline, the material used for taking an impression of the canal space is either by the direct method: calcinable resin; blue inlay wax, or by the indirect method

:silicone type elastomers.

•  Direct technique:

1. the peripheral preparation is carried out, as well as the canal accommodation (fig. 2)
2. calcinable tenons and plastic preforms are suitable (fig. 3 and 4)

3. slight moistening of the canal (to prevent the resin from adhering to the canal walls).
4. impression of the canal accommodation (fig. 5a and 5b):
   • Applying the calcinable resin (liquid and powder) to the plastic post with a brush (fig. 5a)
   • Inserting the plastic post into the canal (fig. 5b)
   • As soon as the resin starts to set, make a small back and forth movement to ensure easy removal of the post (no adhesion to the canal walls, against possible undercuts).
5. shaping of the coronal part with a preform adapted in the occluso-cervical direction. This matrix is ​​filled with calcinable resin using a brush or a spatula, by its occlusal face (fig. 6).
6. After the calcinable resin has completely set, the preparation is carried out according to the classic principles of a preparation for a metal-ceramic or ceramic-ceramic crown. At the cervical level, the excess resin is removed until it comes into contact with the previously established cervical limit (fig. 7).
7. The resulting coronal-radicular reconstruction in calcinable material is ready to be cast in the laboratory. It is preferable to keep it in a humid environment until then, to avoid any dimensional variation.

Note: rebasing may be necessary (adding powder + liquid resin with a brush to the defects).

8. Upon return from the laboratory, the cast part can be glued or sealed with minimal retouching (possibly reducing excessive friction during its installation).
9. The final impression for the crown can be made. This technique offers certain advantages in respecting the canal and coronal shape, dictated solely by the practitioner. On the other hand, it is contraindicated when the cervical limit is subgingival, the precision of the joint then being uncertain (lack of visibility and accessibility). It is not recommended in the case of multiple elements, requiring long clinical sessions.

• Indirect technique:
• The canal cavity is dried with paper points and the impression is taken with Vinylpolysiloxane elastomers in one step and two viscosities. The low viscosity material is injected into the canal, either with a short lentulo of large diameter, or with a syringe with a very fine end; the impression tray is loaded with the high viscosity material, modeled in the form of a gutter on which low viscosity material is deposited; it is thus inserted into the mouth. The removal of the impression tray must be done along a single axis and with a sharp blow to avoid any deformation.
• Inlay-core: Laboratory step:

• Clinical fitting of the false stump and radiological control then sealing or bonding of the latter
• Imprint of the false stump using the wash technique or double blend.
• PLACEMENT OF A TEMPORARY CROWN
• CHOICE OF SHADE
• Fitting of the final crown and final sealing.

1. Definition :

It is a single-piece prosthetic assembly consisting of:

1. Lingual heel
2. Cervico-root cap
3. Root tenon
4. Cosmetic veneer
5. Indication:

– Available crown height not allowing two-stage reconstruction: Short tooth + tight occlusion.

3. Contraindications:
   1. Deep coronal destruction preventing the tooth from being cerclaged.
   2. Short, curved crown.
   3. Root problems: fracture, perforation, mobility, rhysalis.
4. Principle:

It is a crown in which the coronal root reconstruction and the underlying prosthetic restoration are one = one-level restoration.

5. Protocol:

The preparation consists of reducing the coronal part of the tooth to an occlusal plateau perpendicular to its long axis.

The vestibular part is reduced to a bowl shape and the lingual part is prepared to be tapered in relation to the long axis of the tenon. The finishing line is in the form of a very fine fillet.

6. At the Laboratory:

It is the casting of the whole thing in one go (tenon, coping, and heel), once the casting is done, it goes to the clinic for fitting and adjustment. If the result is good, the aesthetic veneer is made according to the chosen shade and according to the CIV method and then it is tried in the mouth if the adaptation is perfect, the sealing will be definitive.

Coronal-root restorations

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Untreated cavities can cause painful abscesses.
Dental veneers camouflage imperfections such as stains or spaces.
Misaligned teeth can cause digestive problems.
Dental implants restore chewing function and smile aesthetics.
Fluoride mouthwashes strengthen enamel and prevent cavities.
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A soft-bristled toothbrush protects enamel and sensitive gums.
 

Coronal-root restorations