Complex tooth reconstruction
1-Introduction:
Rapidly developing caries, fractures of pulpless teeth and dental trauma lead to significant coronal decay. This results in large cavities with sometimes:
• three or more walls missing,
• weakened cusps,
• absence of half of the crown height
These cavities are called complex cavities.
These coronary dilapidations considerably reduce retention at the level of these cavities, which could compromise any possibility of coronary reconstruction. And therefore for a reliable morphological and functional reconstruction of these so-called complex cavities, the practitioner must use artifices or more precisely extrinsic and intrinsic retention elements in order to increase retention at the level of these cavities and above all increase the durability of these reconstructions which we will call complex reconstruction.
2-What is called a complex cavity?
In contrast to simple one-sided cavities and compound two-sided cavities, a complex cavity is one that includes at least three coronal walls. However, this general definition does not account for all clinical situations, and a cavity is considered to become complex when the residual parts of the dental organ alone cannot ensure the stability or retention of the filling.
3-Simple restoration:
This is a direct method restoration, carried out directly on the chair without any retention artifice.
4-Corono-radicular reconstruction:
Reconstruction which makes it possible to compensate for the tissue, mechanical and aesthetic deficit of decayed pulpless teeth. It concerns both the coronal and radicular portions of the tooth: it always involves a complex reconstruction which, to ensure its retention.
4-1-Direct coronal root reconstruction:
They are bonded corono-radicular restorations (RCR), also called corono-radicular reconstructions by material inserted in the plastic phase (RMIPP). They are carried out in a single session at the chair with a material that can be filled or injected.
4-2-Indirect coronal root reconstruction:
Also called cast coronal root reconstructions, these are reconstructions which require a laboratory step, they are metallic (precious or non-precious alloy) or ceramic.
This type of reconstruction is mainly indicated in the case of a low coronary volume or a reduced number of walls (1 wall remaining or totally absent) as well as a cervical limit in a subgingival position.
4-3-Objectives:
A corono-radicular reconstruction is necessary when the decay of the devitalized tooth is significant. Its objectives are:
-To ensure, if necessary, the retention of the coronal restoration by reconstituting the lost tissues.
– To ensure the sustainability of the tooth on the arch, on a biological and structural level.
-To reserve residual dental tissues.
-A balanced distribution of stresses transmitted to the remaining coronal and root tissue.
-To contribute to the restoration of the aesthetic appearance
5-Specificities of the depulped tooth:
5-1- Biomechanical behavior:
The reduced resistance to fracture of the pulpless tooth is multifactorial. The loss of dental substance caused by caries, the canal shaping during endodontic treatment and the resulting structural changes in the dentin tissue represent the main causes of the fragility of the pulpless tooth. Several in vitro studies have shown that coronal decay is the predominant factor in the fragility of the dental organ. The creation of occlusal, mesio-occlusal and mesio-occluso-distal cavities results in a decrease in resistance of 20%, 45% and more than 60% respectively. The development of the access cavity in order to optimize the canal preparation can lead to a thinning of the residual dental walls, particularly at the cervical level.
Complex tooth reconstruction
• When using root canal irrigation and disinfection products:
The various products used for root canal irrigation and disinfection interact with the mineral and organic content of the dentin and can therefore modify its properties:
• Calcium hydroxide, in prolonged use, significantly reduces the mechanical resistance of dentin.
• EDTA will act on the amount of calcium as well as on the properties of the non-collagenous parts of the dentin. These modifications will then lead to erosion as well as softening of the dentin.
• Sodium hypochlorite has a proteolytic action by cutting collagen molecules.
• Chlorhexidine causes a significant decrease in the hardness of root dentin.
5-2- Biological behavior:
Dyschromia-susceptible: internal and external changes will eventually cause a variation in shade. The disappearance of the pulp therefore leaves the dentino-pulp complex in an inactive state.
At the email level:
The composition of the enamel, mainly mineral, does not undergo any qualitative change. Only the quantitative reduction implies a decrease in the mechanical protection capacities of the tooth.
At the dentin level : the collagen framework persists but it will slowly degrade over time.
6-corono-radicular reconstruction:
6-1- Root anchoring:
Definition of the root tenon:
A post is defined as the restoration segment inserted into the root canal to facilitate retention of the central element. The primary purpose of root anchorage is to retain the coronal restoration in an endodontically treated tooth that has suffered significant loss of crown structure.
Tenon characteristics :
According to the dimensions :
Diameter: the rigidity of the post increases with its diameter obviously, the more rigid the post is, the more the stresses transmitted to the tooth are greater, it is therefore not recommended to increase the diameter unnecessarily, especially since this does not significantly improve its retention. The diameter of the post must be between 1 and 1.3 millimeters . The practitioner must ensure that at least 1 mm of peripheral dentine is preserved and in all cases never exceed more than 1/3 of the diameter of the root.
Length:
Theoretically, the length of the tenon should be around two thirds of the root length, in all cases the root length should be greater than the coronal length.
Different criteria can define it:
– Be 5-7 mm from the enamel-cementum junction.
– Be superior to the clinical crown.
– Have half the height of the alveolar bone.
– Preserve at least 4 mm of gutta percha in the apical portion in order to respect apical hermeticity.
Furthermore, studies show that an increase in length results in an increase in retention and better distribution of stresses.
According to the form:
Prefabricated tenons:
The tenons can be conical, cylindrical or cylindro-conical.
Cylindrical-conical tenons:
Therefore seem to be the best choice. The cylindro-conical shape ensures a favorable distribution of stress along the post, allows less mutilation of the apical root dentine and offers sufficient retention
Anatomical tenon:
Anatomical posts reproduce the anatomy of the canal lumen cleared of endodontic filling materials. This time, it is the post that is shaped in a way to adapt to the canal system
According to the composition:
Ceramic tenons:
They are more aesthetic than metal posts, white and opaque, based on zirconium oxide, they have high hardness and biocompatibility.
Regarding its rigidity, ceramic posts are more likely to cause root fractures than fiber posts. In addition, the surface of ceramic posts does not adhere to resin composite materials. More importantly, the ceramic post does not meet the requirement of being
Easily removable in case endodontic retreatment is necessary
METAL TENONS: in steel and titanium
Stainless steel tenons:
They are very rigid and concentrate forces at the apical level instead of distributing them evenly over the dentin. The risk of root fractures is high
Titanium tenons:
They have good biocompatibility. The risk of root fracture is lower due to their lower rigidity. However, they can be difficult to remove (risk of fracture of the post),
Fiber Tenons:
Carbon fiber tenons:
Advantage :
• Dentin-like rigidity.
• Stronger resistance.
• They are easier to remove than other fiber posts.
Disadvantages
The main disadvantage is their dark brown color which may compromise the aesthetic appearance in the case of a wide canal or thin periodontium.
Quarter fiber tenons:
These are white and transparent tenons, or opaque They have a higher fracture resistance
and an elastic modulus very close to that of dentin as well as very satisfactory aesthetics and perfect biocompatibility
Fiberglass tenons:
They are white and transparent, or opaque, and have high resistance and elasticity characteristics similar to those of dentin. They are able to conduct light, facilitating the obtaining of high quality aesthetic restorations.
6-2-Assembly materials:
The assembly between the tooth and the RCR can be done either by:
Sealing (mechanical retention), or by bonding (adhesion retention).
There are 3 categories of assembly materials:
– conventional sealing cements (zinc phosphate or oxyphosphate cements)
– hybrid materials (CVI MAR)
– adhesive glues (also called bonding composites or resin cements).
6-3-The coronal stump:
The purpose of coronal reconstruction biomaterials is therefore to replace the loss of enamel-dentin substances caused by the different modes of degradation undergone by a tooth, caries being the main one. Composite, silver amalgam, compomer, CVI MAR…..metal or metal ceramic crown
7-direct coronal root reconstruction:
Indications:
The number of remaining walls must not be less than 2 or 3
Thickness greater than or equal to 1mm
Height greater than or equal to 2/3 of the initial height
Cervical limit in supragingival position
the possibility of installing an operating field
Contraindications:
The number of remaining walls is less than 2
Height less than 2/3 of the initial height
The impossibility of placing an operating field
Intra-sulcular limit
8-The surgical protocol for performing a direct coronal-radicular reconstruction with a fiber post and a composite coronal restoration:
1-Preoperative X-ray:
It provides information on the canal morphology and allows us to determine the length of the post housing and its diameter, as well as the quality of the canal obturation.
2- The operating field:
Complex tooth reconstruction
3-Preparation of the intra-radicular housing:
The coronal portion having been cleared of altered tissues and obturation residues, the passage of a series of Largo drills, of increasing diameter, eliminates the majority of the endodontic obturation material, and prepares a draft of root housing
4-Trying out the tenon:
The diameter of the post is chosen so as to occupy the maximum space in the canal housing, without rubbing against the root walls.
5-Conditioning the tenon:
6- Conditioning of dental tissues:
7- Application of the adhesive:
8- The bonding composite is injected into the canal housing, the post is also coated with glue and inserted into its canal housing , then everything is photopolymerized
9-Placing the tenon and photopolymerization:
10-After final photopolymerization of the restoration, the peripheral coronal preparation is completed before the placement of a temporary crown .
Complex tooth reconstruction
9-Conclusion:
Performing a coronal-radicular reconstruction is a common but far from trivial procedure. The numerous biological and mechanical imperatives that govern its performance must be the subject of analysis and reflection that leave little room for clinical habits or improvisation.
Sensitive teeth react to hot, cold or sweet.
Sensitive teeth react to hot, cold or sweet.
Ceramic crowns perfectly imitate the appearance of natural teeth.
Regular dental care reduces the risk of serious problems.
Impacted teeth can cause pain and require intervention.
Antiseptic mouthwashes help reduce plaque.
Fractured teeth can be repaired with modern techniques.
A balanced diet promotes healthy teeth and gums.