Complex reconstructions of teeth

Complex reconstructions of teeth

The creation of complex restorations involves the use of devices as well as specific materials; numerous techniques are available to the practitioner depending on the clinical indications.

It is up to him to choose the best tooth-material compromise for greater durability of the tooth on the arch

Definition :

Complex restoration is a reconstruction of the cavity in which the five

size principles cannot be ensured by the residual parts of the dental organ alone.

The cavity is said to be complex when more than two walls are destroyed. This corresponds to stages 3 and 4 of the SISTA classification.

Conditions allowing complex reconstruction:
1. On pulped teeth:

no symptoms, absence of any signs of irreversible pulpitis.
good periodontal condition.
perfect dentin treatment.
radio examination without any alteration.
On pulpless teeth:

asymptomatic tooth.
Complete and watertight root canal filling.
Good hygiene on the part of the patient.
Interest in artificial filling or covering of substance losses:

Protect the dental organ by replacing destroyed tissue.
Preserve residual tissue.
Restore aesthetics.
Restore function.
On living teeth: preservation of a healthy and vital pulp while allowing the normal function of the tooth, i.e. allowing biological and biomechanical integration of the tooth
On devitalized teeth: the restoration must allow:

Preserve the seal of the previously performed endodontic treatment
Transmit functional constraints as closely as possible to an undamaged tooth
Ensure retention of the prosthetic suprastructure

Restoration of pulped teeth:

The complex reconstructions on pulped teeth aim to:

maintain pulp vitality.
to achieve hermeticity and stability of the coronal obturation on the other hand, while preserving as much healthy tissue as possible.

Dentino-pulp protection:

Complex metallic reconstructions due to their conductivity and aesthetic restorations due to their toxicity must be considered as sources of irritation for the pulp-dentin organ especially if the thickness of the dentin is less than 2mm hence the need to use a capping product.

Mechanical principles of cavity preparation:

the preparation of the cavities will have to follow the following rules, namely:

Respect for dental structures:
The stability and support of the material in the cavity.
The mechanical resistance of the filling material
Retention of material in the cavity
Prophylaxis and extension of preparation.

Complex restorations on anterior teeth:
1. Anterior restorations by direct method:

Three strong ideas must be associated, namely:
- the reproduction of nature
- favor the circulation of light
- An operating methodology that allows for predictable and reproducible results
Stratification techniques themselves:
- Choice of shade
- Preliminary clinical steps (initial periodontal therapy; control of static and dynamic occlusion)
- establishment of a watertight operating field

Preparation of a long vestibular bevel of 1.5 to 2 mm on the fracture line
Elaboration of the palatal face using the silicone guide
Production of the proximal faces
Dentin stratification itself: assembly of the dentin masses
Laying down the vestibular enamel layer
Roughing, finishing, polishing and buffing

Anterior restoration by indirect method:

Ceramic veneers: Ceramic veneers combine the advantages of ceramics (stability, aesthetics) and composites (adhesion, preservation of healthy tissue) while avoiding the respective disadvantages (like bonded veneers)

Restoration on posterior teeth:
1. Direct restoration:
  1. Complex amalgam restoration:

In complex amalgam restorations we will use the means of

intrinsic retentions which will consist of carrying out cavity preparations with the aim of increasing retention

removal of walls with insufficient dentin support by tilting them towards the inside of the tooth, allowing better stabilization of the material
the canaliculi: cut using a fissure cutter at the walls, cylindrical in shape, relatively large → good condensation of the material
vestibular and/or lingual extension → improve retention
the wells: parallel to the external wall of the tooth, 1.5 to 2 mm deep, arranged on the periphery of the pulp area, they allow the material to be anchored (see appendices)
Extrinsic retention means such as dentin posts were

used to increase retention and optimize the durability of the tooth on the arch, but with the evolution of restorative materials and bonding techniques, their use has become obsolete.

Indirect restoration:

When faced with a complex cavity of site 1 and 2 stages 3 and 4 with cusp decay, the use of indirect techniques is more appropriate. Indirect restorations involve the placement of rigid materials in already prepared cavities. For this, the walls of the cavity must be undercut to allow the insertion and removal of the restoration. (Appendix 1)

These restorations will be bonded or sealed to ensure their retention to the dental tissues. Indirect restorations on posterior teeth can be:

An inlay, an onlay or an overlay.

Inlay-onlay:

Inlay and onlay are a method of partial restoration of the dental crown.

INLAY : is a cast block restoration when the cusp tips are not affected by the preparation,
ONLAY : is a prosthetic piece designed to restore a loss of substance and which affects several sides of the tooth. (3/4 crown). It allows for large reconstructions without the need for pulp removal.
OVERLAY : with or without cavity preparation which restores the entire occlusal surface of the tooth and are mainly used during occlusal-oriented reconstructions
TABLE TOP is a term used to describe restorations that only affect the occlusal table when they affect the entire occlusal surface.

Their production includes a clinical stage and a laboratory stage.

Indications:

▣ Lesions classified 3 and 4 SI/STA

▣ Damage to one or more cusps

▣ destruction of the vestibular and lingual axial anatomies by more than one third

▣ occlusal rehabilitation (table top).

Materials used:

These elements can be made of composite resin or ceramic

Ceramics:
- Advantage :

stability of the aesthetic rendering
Biocompatibility
mechanical resistance
the ability to bond
Disadvantages :

high modulus of elasticity (important role in tooth fracture by wedge effect)
high abrasion rate

Composite resins:

Benefits :

low modulus of elasticity which gives them a shock absorber role
Lower manufacturing cost
Disadvantages:
Wear
Plaque retention

Method of preparation:
Composite resin:

▣ A layer-by-layer development of the different dentin, enamel and translucent masses followed by polymerization in a specific oven.

▣ the thickness of the composite layer reproducing the enamel must not be thicker than the natural enamel layer.

Ceramics:

Four different processes can be used, the choice of which is linked to the type of ceramic

Preparation principles:

▣ Remove all infiltrated tissue

▣ Preserve all areas of cervical enamel to ensure maximum reliable adhesion, a long-lasting dento-prosthetic seal and limit carious recurrences

▣ facilitate the insertion of the restoration by undercutting the internal and external walls with a convergence angle of 15°

▣ Ensure the stabilization of the restoration by creating stabilizing elements such as boxes and grooves.

▣ Ensure that the cavo-superficial angles of the preparation are close to 90°

▣ fill the cavity with substitute material, resume the preparation by creating a flat base and regularizing its depth

▣ respect the mechanical constraints of the materials:

for ceramics: the minimum thickness must be 1.5 to 2 mm, 2 to 3 mm at the level of a cusp, 1 to 1.5 mm for the depth of the fillet and the width of

an isthmus of at least 2 to 2.5 mm is mandatory

▣ Create a profile of the cervical limit in the form of a round fillet or a shoulder with a rounded internal angle.

▣ Eliminate all sharp corners.

▣ Assess the risk of fracture of thin walls (the minimum thickness of the remaining wall must be 2 mm).

▣ reduce the height of the weak dental walls which risk fracturing by including them in the restoration.

▣ Relocation of the cervical margin (Cervical margin relocation) by creating a layer of composite or by performing a coronal lengthening.

▣ Place substitute material, if necessary, to fill undercuts, dentin pits and reduce the depth of the cavity to move away from the pulp.

▣ carry out a final check before hybridization.

▣ modify the outline of the occlusal limits of the preparations if they are located at the level of the occlusal contacts of the antagonistic cusps.

▣ harmonize the outline of the finishing line by reducing the differences in level of the connection areas of the prepared faces.

Once the clinical preparation is completed according to the well-defined principles, the following will be carried out:

Taking impressions and recording occlusion,
Carrying out a temporary restoration
Final sealing of the restoration

Restoration of the devitalized tooth:

Indications in appendix 2

Biological and mechanical characteristics of the devitalized tooth Contrary to popular belief, the dehydration of the tooth following endodontic treatment is too low to explain on its own a greater susceptibility to fractures; the loss of dental substance is the main cause of weakening Related:

– To endodontic treatments

-To the cavity

-Preparation of the canal accommodation

Different ways of restoring a devitalized tooth:
Partial reconstructions glued:

The main parameters determining the success of CPR are :

A recent pulping.
A loss of substance of low to moderate volume extending to the mesio-occluso-distal cavity of the juxta or supragingival cervical limits.
A favorable occlusal context. We have two methods of RPC, namely:

Direct methods (composite restorations) especially on traumatized anterior teeth
Indirect methods (inlay, onlay with composites) Adhesive restorations

Coronal-radicular restorations (CRR):

The coronal-radicular reconstruction is the intermediate piece between the residual substance and the usual restoration, it is schematically composed of:

A root anchor or post fixed in the root.
A coronal stump on which the crown will rest.
Sealing or assembly material. There are 2 types of RCR:

Direct RCR : performed in the mouth by the practitioner, also known as “striding” RCR, they combine a prefabricated post with a material inserted in the plastic phase which reconstructs the coronal stump.
Indirect RCRs also called “cast”: produced in the prosthesis lab; It is a single piece

Direct or “stride” CPR:

A coronal-radicular reconstruction with a tread Includes

The prefabricated tenon
The false stump
The sealing or gluing assembly system

Tenon characteristics:
1. Tenon dimensions (length and diameter)

The length of the tenon : it must be around two thirds of the root length, however the latter is limited by two parameters:
- Root curvatures ; it is recommended not to exceed the curvature when preparing the root housing
- The length of residual gutta percha : a minimum of 4 to 5 mm of endodontic obturation at the apex. (see appendix)

Tenon diameter:

The diameter of the tenon does not increase its retention and only affects its rigidity; a diameter between 1 and 1.3 mm is considered satisfactory.

Anatomical parameters:

It is important that the practitioner knows and keeps in mind the anatomical particularities to distinguish the so-called at-risk roots and adapt his therapy accordingly.

Tenon shape:

The tenon shapes are divided into two groups

Anatomical tenons are only conceivable in the case of cast RCRs
Standardized systems of various shapes and materials usually three forms are described;
- cylindrical : they are retentive but also very dangerous risk of cracks and root fractures
- Conical : They are less retentive requiring mutilating preparation at the cervical area of the tooth
- Cylindro-conical : the most suitable because they are better suited to root morphology
Surface condition of the tenon:

We consider here that the metal tenons whatever their nature we distinguish:

Dentin threaded posts: designed to be screwed into the root, also called screw posts; very iatrogenic with regard to the longevity of the tooth and should therefore be avoided
Tenons without dentin tapping, they are smooth in most cases or with grooves

These grooves are intended to increase the retention of the assembly material

Nature of the tenon:

The nature of the post will influence both its own mechanical resistance as well as the transmission and distribution of stresses to the root dentine. We distinguish

Stainless steel tenons:

They are very rigid and concentrate forces at the apical level, the risk of root fractures is high, they also expose the tooth to a risk of corrosion

Titanium tenons:
- they have good biocompatibility
- the risk of root fracture is lower due to their lower rigidity,
- they can be difficult to remove
- their radio opacity close to that of the gutte percha complicates radiological control somewhat.
Ceramic tenons:

No longer recommended because they are rigid and brittle, often oversized

Fibered tenons (quartz glass or carbon fibers):
Properties of fiber tenons :
- Elasticity modulus which is closest to dentin, allowing them a better distribution of occlusal stresses.
- They are biocompatible
- Their composition includes a significant portion of resin which binds more

easily to the composite of reconstruction and bonding which allows to obtain a good structural homogeneity of the final RCR

They are aesthetic (apart from the carbon fiber posts) allowing aesthetic restorations on anterior teeth.
The composite fiber post association is to be favored when the indication of RCR is posed: As much for aesthetic, biological, as mechanical reasons (modulus of elasticity close to that of dentin, adhesion between composite and post and composite and dentin)
In fact, the concept of this association is based on the idea of homogeneity of the anchoring material and reconstructions allowing a harmony of mechanical behavior with the natural tooth.
It has been shown that a tooth restored with multiple bonded fiber posts has a

mechanical behavior closer to that of a healthy tooth than a tooth restored with an inlay core or with a single post

For restorations of posterior teeth and for reasons of economy, bonded titanium posts can constitute a satisfactory compromise.

Means of assembly, sealing or bonding:

The practitioner has 3 assembly modes:

Conventional sealing
The so-called adhesive sealing because it uses conventional CVI or CVIMAR or bonding with resin cements or annex3 bonding composites

The choice is guided by:

CPR itself: direct or indirect
From the type of tenon used
Coronary reconstruction material
From the affected tooth
Patient-related conditions

The coronary stump:

The coronal stump has the function of replacing the missing coronal stump; for this purpose it must offer a perfect connection to the dental structure and a mechanical resistance adapted to the constraints; different materials can be used

– Favor the use of micro or nano-filled hybrid composite to increase compressive strength

-Using the same type of composite for restoration and bonding allows for mechanical consistency within the reconstruction

-The choice of setting method : chemically cured, light cured or dual cured, providing sufficient working time and a guarantee of complete setting throughout the entire depth of the filling.

Indications and operating protocols for CPR :
1. CPR strides
  1. -Indications:

Minor coronal decay, three residual walls are required.
Remaining walls equal to half the total coronal height of the healthy tooth.
cervical limits of supragingival decay
2 mm between the edge of the reconstruction and the dento-prosthetic limit.
Strength of the restoration compatible with the functional constraints that a tooth must undergo

Establishment of a rigorous operating field
Patient cooperation

Clinical sequences for implementing stride CPR:

Preoperative X-ray : to visualize the future post, in length and diameter
Peripheral preparation: depending on the material of the future prosthesis
Internal cameral preparation : the coronal part of the tooth is cleared of

remains of endodontic filling materials and the entrance of the canal is thus chosen for anchoring and marked

Preparation of the canal space : the canal path is cleared of a large part of the filling material by passing a Largo drill with a non-working end of diameter 1, 2 or possibly 3 in the case of a strong cylindrical root.
The length of the post in relation to the length and root volume having been previously determined on a retro-alveolar image.

A retro alveolar radiograph with the last drill in place is recommended to validate the chosen length.

Passage of ultrasonic or manual instruments to eliminate all residues attached to the undercut areas
Choosing and adjusting the tenon :

its diameter is chosen so that it floats in the canal.
The end is cut so that it is located 1mm from the occlusal surface of the reconstruction.
Bonding procedure and placement of the coronal restoration:
- Cleaning and disinfection of the canal space using a chlorhexidine solution.
- Collage itself:
  - Etching by application of a 37.5% orthophosphoric acid gel reduced to 15 seconds maximum
  - -Rinse thoroughly for 20 seconds
  - Air syringe drying supplemented by the use of paper cones
  - dentin surfaces must not be dried out.
  - applying the adhesive using a microbrush by gently rubbing the walls of the prepared canal
  - Any excess is absorbed using a paper point. The adhesive used must be chemo-polymerizable or Dual.
  - Applying the adhesive to the tenon
  - Drying
  - The post is then stored on a sterile compress away from light or photo-polymerized.
  - Intra-radicular injection of the composite using a very fine tip brought to the bottom of the housing, the injection progresses at the same time as the tip rises
    - Lentulo Passage.
    - Slow insertion of the tenon
    - Photopolymerization for 40 seconds.

Injection of the composite at the coronal level and at the level of the preselected mold.
Photopolymerization for 40 seconds.
Removal of the preform and reshaping of the stump.

RCR CASTINGS: Inlay core
1. Directions:

Insufficient number of walls or walls of too low height
Juxta-gingival coronal decay less than 2 mm between the restorative material and the cervical margin
Root anatomy incompatible with the use of a prefabricated post
All cases where strenuous CPR is contraindicated

Operating protocol:

Peripheral preparation : depending on the future cuff, leaving sufficient space between the cervical limit and the edge of the RCR
Preparation of the canal accommodation the phase of unobturation and identification of the lengths remains identical to that of the stride CPR.
Internal preparation : consists of eliminating undercuts as well as flaring the canal entrances to increase retention.
Taking impressions by direct or indirect method
Laboratory sequences intended for the creation of the future aesthetic restoration.
Sealing the inlay core and creating the prosthetic part Conclusion

Complex restorations pose a challenge for the practitioner. The development of adhesive technologies and restorative materials has led to the abandonment of certain retention devices and a much more conservative approach to dental tissues.

Annexes: