Coronal-radicular anchors: inlay core, richmond

Coronal-radicular anchors: inlay core, richmond.

Corono root anchorages: inlay core, richmond.

Summary :

1. Introduction.
2. General principles of RCR.
3. Direct CPR.
4. Indirect RCRs.

1. Inlay core
2. Richmond.

5. Coron-radicular anchoring.
6. Operating protocol.
7. Taking a fingerprint.
8. Conclusion. 
9. Introduction -1-

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Loss of anatomy and architecture resulting from carious damage is the main cause of biomechanical transformations of the dental organ, leading to its weakening. Restoring the mechanical continuity of the crown and root of the tooth by reconstitution without aggravating this weakening seems to be a priority objective. 

Coronoradicular restoration is the last resort in the treatment of major loss of substance from the dental organ; at this stage the tooth is depulped and requires restoration to good aesthetic and functional condition.   

We distinguish two types of reconstructions:

❱ Direct RCR : using materials inserted in the plastic phase, supported or not by a tutor.

❱ Indirect RCRs : which require a laboratory step. They are metallic (precious or non-precious alloys) or ceramic

Coronal-radicular anchors: inlay core, richmond.

The different coronal-radicular restorations  

2. General Principles of RCR -2-

• Imperatives and General Rules :

• Restore invalid or absent coronary morphology.
• Preserve as much residual tooth substance as possible.
• Protect the restored dental organ by replacing missing tissue.
• Distribution of functional constraints within the remaining root and coronal substance.
• Maintain the apical seal permanently.
• To allow for canal reintervention, the removal of the corono-radicular reconstructions must be possible.
• Endodontic requirements:

Coronoradicular reconstruction follows endodontic therapy, it must:

• Create a three-dimensional, waterproof and durable obturation of the canal system.
• Complete debridement and disinfection of the root canal system.
• Respect for the initial canal anatomy.
• Biomechanical imperatives:

Certain precautions must be taken with regard to loss of dentin elasticity.

The lack of pulp vitality weakens the tooth: if the hardness of the mineralized tissues is little altered, their resistance to traction is reduced.

The practitioner then has a dual objective: not to weaken the tooth further and if possible to strengthen it.

Most tenon fractures occur near the junction with the crown where stresses are most intense and most frequent.

The reconstruction material transmits the forces to the root, possibly via the tenon.

3. Direct coronal reconstructions -2-3-4

C

This technique is to be preferred when the required clinical conditions are met.

This process allows the tissue integrity of the tooth to be preserved as best as possible.

The materials used are essentially composites which offer capacities for absorbing occlusal forces (linked to the modulus of elasticity).

Coronal-radicular anchors: inlay core, richmond.

Coronal-radicular anchors: inlay core, richmond.

1. benefits

• Crowded coronal-radicular reconstructions (CRRs) preserve more residual coronal dentin.
• By using a composite reconstruction and fiber posts (carbon, quartz or glass) whose moduli of elasticity are very close to that of dentine, these stepped RCRs generate a coherent system, capable of absorbing and assimilating occlusal forces.

2. Disadvantages

The undeniable weak point of the stride RCRs lies in the mechanical and retention properties: the mechanical properties of the reconstitution composites require support by residual dentine walls in sufficient number and strength as well as reinforcement by a post in the coronal portion.

It should be noted that this type of RCR may not require root anchoring. Material retention is then achieved by bonding to the residual walls. 

The addition of a root anchor in the form of a tenon ensures the stability of the reconstruction and contributes to its retention.

3. directions

• Persistence of 3 residual walls. – Minimum thickness 1 mm.
• The cervical anatomical limit of the coronal substance loss must be supragingival in order to be able to clinically achieve a watertight seal as well as a cerclage of the healthy dentin by the prosthetic construction.
• Since these reconstructions can use bonding and photopolymerization techniques, accessibility to the preparation remains a determining factor and isolation of oral fluids is essential.

4. Contraindication

• Major coronal deterioration: insufficiency of the residual walls.
• Juxta or subgingival cervical limit not allowing for the isolation of fluids during bonding or the covering of the tooth-obturation joint by the prosthetic element to a height of at least 1 mm. Sealing cannot then be achieved.
• Difficult to access teeth making execution of the surgical protocol random. 

4. Indirect coronal-radicular reconstructions: 5-6-7

1. Inlay-core  :

The use of this technique will be justified whenever the clinical conditions required for reconstitution using material inserted in the plastic phase do not 

are not met. The radiographic examination contributes to the decision. It can in no case be sufficient. The final choice is subject to the clinical assessment of the value of the residual walls.

      Inlay core on the 2nd premolar

It is a fully cast prosthetic construction allowing the reconstruction of a loss of coronal or coronoradicular substance of a devitalized tooth previously prepared to receive a total coverage element, this inlay core includes a root post or several posts and a coronal reconstruction.

After being sealed in place, these reconstructions will receive a full coverage crown type CC, CIV, CCC or CCM

 Aim 

  The main goal is the reconstruction of the stump which reinforces the bond between the root and the residual dentinal walls.

CPR allows:

• To restore loss of substance due to trauma or carious lesion.
• To preserve residual dental tissues;
• To ensure the sealing of the canal filling.
• To ensure the retention of the overlying prosthetic part;
• A balanced distribution of stresses experienced by the prosthetic restoration and transmitted to the remaining coronal and root tissues.
• To contribute to the restoration of the aesthetic aspect of the restoration.

Indications:

• The inlay-core is indicated whenever any other conventional restoration proves to be insufficient both in mechanical resistance and in support surface at the level of anterior and posterior teeth damaged by caries.
• Less than 3 residual walls (after preparation).
• Residual walls less than half of the initial height 
• Tooth difficult to access or inability to fit the dam.
• In the case of significant dental malposition to correct the non-existent parallelism of the abutment teeth intended to receive a bridge 
• Tooth located in an occlusal context that does not allow for the sustainability of a post-plastic material-posterior teeth association.

Contraindications  :

•  Root fracture or rhizalysis.
•  Root perforation.
•  Significant tooth mobility.
•  Unstabilised apical and periapical lesions.
• Insufficient height of the alveolar bone.
• Unfavorable occlusal pattern.
• Uncontrolled parafunctions (bruxism).

Advantage :

The main advantage lies in the independence that exists between the inlay-core or the false stump and the definitive prosthetic element. This presents several advantages:

• Edge adaptation and adjustment of the prosthetic reconstruction are independent of those of Inlay-core.
• In the event of significant loss of dental substance, the cervical limit will be placed on the inlay core, thus providing support for the restoration and limiting infiltration;
• The prosthetic element can be subsequently replaced if necessary without altering the sub-adjacent structure i.e. Inlay-core.

• It is an excellent bridge abutment because of its mechanical resistance.
• Provides protection and strength to severely damaged teeth.

Disadvantages:

• Tenon too rigid transmitting all occlusal constraints to the root dentine already weakened by the various preparations.
• Risk of corrosion (non-precious alloy).
• A risk of cracking and fracture that is more or less high depending on the resistance of the residual root tissue.
• Endocanal reintervention is difficult, especially in the case of metal posts assembled by bonding; removal is often time-consuming and iatrogenic for the integrity of the root.

Special cases of inlay cores : keyed inlay core 

These are one or two isolated male elements, transfixed to the inlay-core and intended to secure or immobilize the RCR in the root.

The aim of this type of reconstruction is to limit the weakening of the roots by reducing the length of the anchors (avoids crossing the root curves), without however harming the retention of the prosthetic piece since the number of anchors is increased.

This system is mainly used when the residual crown is almost non-existent.

• Benefits  : 

• Allows for long-term restoration of a multi-rooted tooth.
• Exploitation of multiple divergent channels.
• Allows to reduce the length of the root tenons.

Noticed :

In the case of parallel channels, the two tenons are attached to the same base.

In the case of non-parallel channels, one will be attached to the stump, the other will be placed secondarily, acting as a key locking the assembly onto the stump.

2.  Crown Richmond  :

Definition 

It is a replacement cap comprising a cap held by a root tenon and supporting the coronal reconstruction, also called a tenon tooth. This is the oldest technique and is referred to as a single-stage restoration (coronal and root restoration in a single block).

Coronal-radicular anchors: inlay core, richmond.

 The Richmond Crown 

Indications  :

It is limited to:

• Anatomically short or abraded tooth, very tight occlusion whose available coronal height does not allow for the integration of a two-stage restoration.
• Tooth with reduced diameter mandibular incisor not allowing a resistant aesthetic achievement on 2-story construction.

Contraindications  :

• Root fractures;
• Root perforations;
•    Rhizalyses;
•    Significant mobility (periodontal disease);
•    Unstable apical or periapical lesions.

Disadvantages  :

•   Difficulty of the impression to record perfectly and in a single step the canal anatomy and the cervical limit of the coronal preparation.
•   Risk of more frequent loosening due to direct transmission of mechanical stresses to the tenon.
• This practice is however contraindicated for the coronary part because its adaptation becomes random.

5. Root anchoring:

The form:

It must meet the following objectives: 

• The tissue economy.
• The distribution of stresses along the root.
• The capacity to resist traction or bending.
• Ease of sealing or bonding.
• Allow re-intervention.

 Dimensions:

– Length  : 

It is currently considered that it should be as high as possible in order to distribute the stresses on the root axis and increase retention, but this principle is accompanied by a certain number of clinical criteria to be respected:

• A minimum of 4 to 5 mm of endodontic obturation must remain beyond the end of the post to preserve the apical seal;
• The length of the post should correspond to at least half the height of the bone tissue supporting the tooth.
• A maximum anchorage length should be sought on the maxillary anterior teeth to absorb shear stresses;
• Drilling is shortened in the case of a thin root in order to minimize its weakening;
• In the case of a curved root the tenon must stop before the start of the curvature:

Coronal-radicular anchors: inlay core, richmond.

– The diameter  :

The diameter of the post should not exceed 1/3 of the root width. A large diameter considerably weakens the root and does not increase retention.

– Materials  :

• Non-precious alloys
• Among them, we most often find Nickel Chrome (Ni-Cr) and chrome cobalt (Cr-Co). These are the most rigid. Their sensitivity to corrosion is increasingly relativized . 
• Precious alloys
• composed of Gold (Au) and Platinum (Pt). 

6. Operating protocol 

Retroalveolar radiography:

The retroalveolar radiograph of the causative tooth is mandatory because it allows us to find out about:

• the length, shape and curvature of the root.
• the presence of possible inter-radicular alveolysis or rhizalysis.
• the integrity of the periapical space.
• the quality of the root canal filling.
• the presence or absence of desmodontal enlargement  
• appreciates the bone level.

 Instrumentation:

• Turbine.
• counter angle.
• gate drills.
• Largo drills.
• kerr pin. 

The actual preparation takes place in 3 stages:

• Cameral preparation.
• External peripheral preparation.
• Canal unclogging and widening.

1. Cameral preparation :

It consists of stripping the internal walls relative to the axis of the post after removing heterogeneous coronal materials: temporary cements, composite or amalgam, curetting the carious areas and removing the filling materials up to the canal entrances.

The housing is flared at its entrance creating what is commonly referred to as the connecting cone, box or neck lock. 

This area constitutes the transition between the post and the coronal part of the restoration.

 Its aim is to avoid fractures in this region which presents a zone of mechanical weakness. The box should not be rounded (in cross-section), but rather oval or rectangular in order to guarantee an anti-rotational effect to the restoration and allow immediate placement without risk of positioning error.

2 Preparing external devices 

                                                                                                                        The cervical limit of the future crown must cover the entire coronal-radicular reconstruction and be in contact with the dental tissue everywhere.

The preparation of the external axial faces will depend on the planned restoration.

Removal of enamel and unsupported dentin. The vestibular part is cut in a gentle slope towards the gingival margin, up to a subgingival level of approximately 0.5 mm (flute beak cut).

3 Unclogging and canal widening.

1. Take a pre-operative x-ray;
2. Measure the length of the canal on the radiograph to determine the limit of the canal unobturation which should be 5 mm from the apical zone
3. Isolate the tooth.
4. Start the unclogging with a No. 1 drill bit up to the previously determined limit, gradually increasing its diameter according to the canal width.
5. Use largo drills of different diameters to complete the unobturation and widen the canal; they represent the instruments of choice, their blunt and non-cutting end allows to follow the path of least resistance. The unobturation can also be done manually using a rigid Kerr n5 pin or we combine the two methods and this is the most frequent.

                                      Gates forest

                                                                                   Long forest                   

6. Place a Kerr pin in the canal, the stop is slid to the entrance, remove the pin and check the extent of the unobturation using an endodontic ruler.

                  The clinical stages of the inlay core

Coronal-radicular anchors: inlay core, richmond.

7. Taking Fingerprints:

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The impression of a corono-radicular preparation poses a particular technical problem: that of recording the canal accommodation, the problem consists of making the impression material penetrate it homogeneously and completely.

There are two techniques for taking impressions of corono-radicular preparations.

 Direct technique :

A simple, very popular technique that offers great precision because it limits the deformations inherent in the impression materials and the setting of the plaster. It consists of the practitioner mounting the inlay-core model in calcinable resin or blue inlay wax directly in the mouth. This model will then be cast in metal alloy in the prosthesis laboratory. 

This technique is indicated for single reconstructions and small area reconstructions and cannot be used in the case of large area multiple preparations (large bridge or numerous solidified crowns) for reasons of parallelism management.

    Steps :                                                                                                                                                       The canal must be cleaned with alcohol and then dried.

1. Testing the calcinable tenon 
2. light moistening of the canal (to prevent the resin from adhering to the canal walls).
3. Applying the calcinable resin (liquid and powder) to the plastic tenon with a brush
4. Placing the post in the canal space 

Coronal-radicular anchors: inlay core, richmond.

 As soon as the resin starts to set, small back and forth movements are made to ensure easy removal of the post (non-adherence 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.

After the calcinable resin has completely set, the preparation is carried out according to the classic principles of a preparation for a metal-ceramic crown or ceramic-ceramic crown. At the cervical level, excess resin is removed until contact with the previously established cervical limit.

The model is filed (rebasing may be necessary to address any gaps).

Coronal-radicular anchors: inlay core, richmond.

6. The corono-radicular reconstruction thus obtained 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.

7. the casting can be glued or sealed with minimal retouching (possibly reducing excessive friction during installation).

8. the final impression for the crown can be made

Indirect technique:

– the low viscosity fluid material is injected directly into the root canal, a tutor is introduced before the material sets, so that it supports it. We can even use a lentulo to optimize wettability and adaptation to the canal walls.

-the standard impression tray chosen beforehand is loaded with a high viscosity elastomer and relined with a low viscosity elastomer in a single step – double mixing -, then inserted in the mouth until the material has completely set.

– The impression tray must be removed along a single axis and with a sharp blow to avoid any deformation.

Fingerprint control

The absence of bubbles, gaps and drafts must be checked at the level of:

The cervical limit.

Connecting cone.

From the walls of the preparation.

8. Conclusion

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Restoration using coronoradicular anchors remains the last therapeutic possibility before moving on to tooth extraction.

Knowledge of dental anatomy (particularly root and endodontic), occlusal constraints and the biomechanical behaviour of the depulped tooth is essential for each practitioner so that they can establish the appropriate indication for RCR, ensure the medium-term sustainability of the dento-prosthetic system, as well as understand potential RCR failures.

Coronal-radicular anchors: inlay core, richmond.

Bibliography:

1. dental information published 07-06-2017.
2. Report on the use of preprosthetic coronal reconstructions, root anchoring. National Academy of Dental Surgery 07-21-2003
3. Preprosthetic coronal-radicular reconstruction of depulped teeth. Marc Bolla, Vincent Bennani. CDP edition.
4. Corono-radicular reconstruction using quartz fiber and composite resin posts. Prosthetics notebooks n-116. December 2001.
5. Herbert Shillingburg: The Fundamentals of Fixed Prosthesis.1998
6. Shillingburg-jacobi-brackett: fixed prosthesis preparations, principles and clinical applications.
7. E.d’incau, M.bartala, A.dos-santos: treatment strategy for depulped teeth. Clinical realities 2011, vol 22 n1:273-280 

Coronal-radicular anchors: inlay core, richmond.

  Wisdom teeth can be painful if they are misplaced.
Composite fillings are aesthetic and durable.
Bleeding gums can be a sign of gingivitis.
Orthodontic treatments correct misaligned teeth.
Dental implants provide a permanent solution for missing teeth.
Scaling removes tartar and prevents gum disease.
Good dental hygiene starts with brushing twice a day.
 

Coronal-radicular anchors: inlay core, richmond