BONDED RESTORATIONS: INLAY, ONLAY, OVERLAY

BONDED RESTORATIONS: INLAY, ONLAY, OVERLAY

Nowadays, with the contribution of adhesive dentistry, the dental surgeon has access to numerous therapies. Indeed, over time, and thanks to the significant development of adhesion, multiple restorative techniques have evolved in order to best satisfy the principle of therapeutic preservation among the most conservative in the therapeutic tissue gradient. The progress of adhesive dentistry has then allowed microdentistry to extend to the field of

fixed prosthesis, whereas until now it remained confined to conservative dentistry.

2. Definitions:
   • Dental restorations: direct/indirect, coronal/coronoradicular:

Direct dental restoration is a coronal or coronal-radicular reconstruction performed directly on the patient (whether in one or more sessions). It is the OCE which is concerned with direct dental care: coronal fillings, (canal fillings (+/- screw post) / fiber posts) + coronal reconstructions.

Indirect dental restoration involves a clinical phase (patient in chair) and a laboratory phase. These two phases can be performed in one session or in separate sessions. It is the dental prosthesis that goes through the laboratory stages to ensure the fixed tooth-supported reconstructions.

The choice between direct or indirect reconstruction depends on several factors: tissue loss will guide the practitioner, then he can choose (according to his experience) the technique that he masters and judges more adapted to the clinical situation and the financial capacities of the patient.

• Dental restoration materials: direct/indirect

For direct restorations: After passing through the temporary fillings: 🡪coronary fillings are made with different definitive materials: amalgam, composite, glass ionomers 🡪 Canal fillings can be made with gutta percha sealed with a sealing cement (there are several cements according to different techniques).

After passing through a temporary resin prosthesis, we move on to partial coronal reconstruction (alloys, composites, ceramics), full coverage crown (alloys, ceramics), or coronal-radicular reconstruction (alloy inlay-core + ceramic or metallic coronal reconstruction).

• Assemblies of dental restorations:

Direct restorations are placed and polymerized on the treated dental tissues to ensure the sealing of the filling. Indirect restorations are

parts already polymerized, so they require an intermediate material to ensure the bond to the dental tissue by mechanical anchoring (assembly by sealing without dental or prosthetic surface treatment), or by mechanical anchoring and chemical adhesion (assembly by adhesion with dental surface treatment and prosthetic intrados)

Conservative treatment no longer simply acts as an inert filling, but, through bonding, mechanically contributes to the tooth’s strength. The adhesive layer provides protection against bacterial contamination of the pulp and limits the risk of postoperative sensitivity. The adhesion compensates for the relative fragility of pure ceramic elements and gives them a longevity as significant as that of sealed restorations.

• Dentin Substitutes:

Dentin substitutes are those that replace the volume of destroyed dentin and seek to imitate its functions.

Restoring a tooth isn’t just about filling it with a material. Today, the goal is to restore the damaged organ to its most natural capabilities, normally ensured by the architecture of the enamel, dentin, and living pulp.

• Biomimicry:

Biomimicry is a concept proposed in the 1950s and recently adopted in the dental field by Pascal Magne. In restorative dentistry, it is defined as “the study of the structure, function, and biology of the dental organ as a model for the design and manufacture of materials to reconstruct or replace teeth.”

A biomimetic restoration aims to maintain biological balance, recreate appropriate mechanical behavior, and restore the anatomical appearance. Currently, no single material is capable of meeting all of these needs, but it is possible to split the roles to better approach the result. The most “biomimetic” restoration, seeking to copy nature, using dentin and then enamel substitute materials: This is what we do by filling a deep cavity with cement before covering it with an onlay or overlay. This is what we do by creating a coronal-radicular restoration (internal core) before covering it with a crown (external superstructure).

• Biomimicry and enamel restoration materials (enamel substitutes):

Ceramic and composite materials integrate perfectly into the dental and gingival environment. Modern materials and adhesive techniques available today allow us to provide treatments that closely mimic natural teeth.

Composite resins:

Ceramics:

Composites or ceramics?

• Loss of dental tissue:

Enamel is a rigid structure that serves as a protective “shell” for dentin, which in turn represents the shock-absorbing “core.” This pair of structures is biomechanically opposed but works together perfectly to withstand the functional oral environment.

Dentin constitutes the bulk of the dental crown. It physically protects the pulp and ensures its biological defense. It is also primarily responsible for regulating the tooth’s capacity for plastic and elastic deformation and its ability to absorb chewing stress.

Finally, it is this which supports the very rigid, but more fragile, shell which constitutes the enamel.

Any loss of coronal substance weakens the dental organ. It causes a wound to the dentino-pulp complex by exposing the permeable tubular network, and a reduction in the thickness of the tissue barrier that insulates the pulp. It results in a reduction in the physicochemical cohesion of the initial dentin core.

mechanical characteristics are modified by the change in anatomy, leaving dissociated and unsupported walls of lesser resistance.

The fragility of the devitalized tooth is linked to the loss of architectural reinforcements (palatal surface of the anterior teeth, marginal ridges and occlusal surface of the posterior teeth) linked to pathological or therapeutic decay.

And no to pulping. In addition, the biomechanical behavior of the dentin of a pulped tooth and a pulpless tooth are very similar, pulpless dentin does not

lose only 9% of water

Let us consider that the treatment of the dental organ is first and foremost a biological act, which aims to protect the tooth and guarantee its vital prognosis. The pulp status and the level of damage to the dentino-pulp complex constitute the first basis of reasoning in decision-making. In a second step, the biomechanical properties will intervene according to the needs of compensation for tissue loss.

The choice of the form of restoration (partial or peripheral) and its constituent material depends on the tooth, the location of the loss of substance, its volume and the risks of deformation (and therefore fracture) of the remaining walls.

The choice of dentin substitute material constituting the base of internal cohesion depends on the characteristics of the dentin tissue and the level and type of constraints received by the tooth.

• Required criteria for a dentin substitute material:
  • ensure a seal of the dentino-pulp complex to preserve the pulp in the case of a pulped tooth; or of the endodontic network to prevent bacterial and derivative penetration in the case of a pulpless tooth;
• compensate for the destroyed dentin volume by adding a mass with characteristics close to dentin: 🡪the modulus of elasticity corresponds to the rigidity of the material, affecting the damping of occlusal stresses in the dental organ. That of dentin is evaluated at 18 Gpa; 🡪the compressive strength represents the capacity of the material to undergo occlusal forces and to deform before rupture. Dentin has a compressive strength of 297 Mpa;

🡪 Flexural strength is especially relevant for teeth in the anterior sector. It defines the material’s resistance to plastic deformation. Dentin has a value of 80 to 250 MPa.

• obtain a core that can adapt durably to the persistent dental tissue and other materials likely to complete the anatomical restoration.

•  Dentin substitute materials: 

🡪 Glass ionomer/GIC cements: 

 They come either in powder and liquid form to mix, or in the form 

 of capsules for automixer. They can be photopolymerizable or 

 chemopolymerizable, and we distinguish: 

• CVIMARs made of glass ionomer cement to which a resin based on 

 hydroxyethylmethacrylate (HEMA) allowing adhesion to dentin. 

Ex: Ketac Universal 3M® (chemopol./powder and liquid); Ketac Universal Applicap 

 3M® (chemopol./capsule); Fuji II LC Improved®, GC (photopol./photo) (fig. 2 to 4); 

• high viscosity CVIs [5], which are distinguished by the absence of resin and by the 

 presence of polyacrylic acid in their formula, increasing their capacities 

 adhesion to dental tissues. The absence of resin improves the properties 

 biological properties of the material. 

 Ex: Equia Forte®, GC (chemopol./capsule) (fig. 5). 

🡪 Composites: 

 The most common on the market are microhybrid composites (e.g. G- 

 ænial®, GC; Quixfil Dentsply Sirona®; Herculite XRV®, Kerr) and nanofilled (Filtek®, 

 Bulk Fill 3M; Grandio®, Voco; SDR®, Dentsply Sirona (fluid); Tetric EvoCeram 

 Bulk Fill®, Ivoclar Vivadent) (fig. 6 to 9) . 

🡪 Tricalcium silicate, bioceramic 

 Tricalcium silicates are derivatives of Portland cements. 

 Two have a thick consistency that makes them suitable as substitutes 

 dentin. 

 Biodentine® ( Septodont ): is a high purity cement 

 (fig. 10) . It consists of a powder composed of tricalcium silicate, oxide 

 zirconium, calcium carbonate and a liquid containing water 

 modified with calcium chloride and a water-soluble polymer. 

 Biodentine® produces calcium hydroxide, which induces the formation of 

 reaction dentin and hydroxyapatite crystals. 

 This material is also bioactive and ensures biomineralization and induction of 

 differentiation of pulp cells. 

 TotalFill® Bioceramic (FKG) is a bioceramic containing silicates of 

 calcium (di- and tricalcium), monobasic calcium phosphate, calcium oxide 

 zirconium, tanatal oxide and thickening agents (fig. 11 and 12) . 

•  Bonding and adhesion: 

 With the help of bonding, saving dental tissue is now possible and must 

 be a constant concern. Of course, bonded bridges see their 

 increasingly limited indications thanks to progress in implantology, but 

 Adherence is more than ever at the heart of our therapeutic arsenal. A treatment 

 preservative no longer plays a simple role of inert sealing but, by gluing, 

 mechanically contributes to the resistance of the tooth. The adhesive layer allows for a 

 protection against bacterial contamination of the pulp and limits the risks of 

 postoperative sensitivity. 

 Different glues: 

 Resins: Resins, which result from the polymerization of methacrylic molecules, 

 are now used daily in dentistry. They are found in 

 glues and in composite materials. We distinguish the adhesive which is a very strong resin 

 fluid that infiltrates the roughness of the treated dental surfaces and thus forms a 

 mechanical keying, and glues that are loaded with particles and create the bond 

 mechanical between the adhesive layer and the prosthesis. In adhesive systems, the 

 resins are generally associated with “primer” type agents which modify the 

 surface to be bonded. The initiation of polymerization can be obtained by a source 

 luminous in the case of photopolymerizable glues, which allows a time of 

 important handling. Polymerization can also be chemical, by mixing 

 of the “base-catalyst” type, which allows for complete polymerization 

 under opaque fillings. There are also glues whose 

 polymerization is mixed “photo-chemo”. 

🡪“4 META” resins Very quickly, the so-called 4-META resins established themselves as 

 a product of choice for bonding metal alloys 

🡪 Resin-modified glass ionomer cements: Adhesion of modified IGCs 

 could be improved by applying an adhesive system before the installation of the 

 CVI. 

🡪 “Methyl diphosphate” resins “MDP” resin not only improves 

 adhesion to enamel and dentin, but provides very effective bonding to alloys 

 metallic. Panavia® is the trade name for this “MDP” resin 

Bonding to dental tissues: 

 The two tissues that make up the tooth, enamel and dentin, are quite different in 

 their chemical composition and physical properties. Enamel is a hard tissue and 

 brittle, whereas dentin is flexible and softer. This tissue duality gives 

 to the tooth a very important mechanical resistance, however it complicates the 

 membership process. 

 It was Dr. Michael Buonocore who first demonstrated that an acid could 

 alter the surface of the tooth enamel and allow bonding by a resin. 

 greater dissolution of the core of the prisms will in fact create a microrelief at the 

 surface of the enamel. A resin can then infiltrate these crevices created 

 and ensure adhesion by mechanical keying. The adhesion mechanism is 

 unchanged since its discovery in the 1950s. The ideal protocol is 

 the application of 37% orthophosphoric acid for 15 seconds. 

 Dentin bonding remains a challenge today because of many elements 

 come to oppose effective adhesion. Much less mineralized than enamel 

 and differently organized, the dentin does not allow to create a relief on its surface 

 by an acid attack. In addition, the presence of water, particularly in the 

 cellular extensions is not favorable to good contact between the resin and the 

 dentine. 

 The key to dentin adhesion lies in the ability to penetrate the tubules 

 dentin by the adhesive . These intratubular extensions (tags) will anchor 

 mechanically the resin to the dentin. Another important part of retention is 

 obtained by infiltration by the adhesive of the collagen fibers of the prepared surface 

 dentin. What is called the hybrid layer is created . When the tubules 

 are rare, adhesion is mainly ensured by the hybrid layer. 

 This “dentin hybridization”: 

Bonding protocol: 

 Regardless of the generation of adhesive used, it is first necessary to 

 clean the surfaces to be bonded. Ultrasonic descaling and the use of a paste 

 fluoride-free abrasives allow for effective cleaning of dental surfaces. 

 Fluoride applications should be deferred until bonding sessions, as the 

 fluorides decrease adhesion values. 

 It is then necessary to protect against oral humidity and the risk of contamination 

 salivary. Using a dam is the best way to obtain a field 

 clean and dry operating room. 

 Membership is obtained in two stages: 

 The first application is that of the etching agent, classically acid 

 37% orthophosphoric acid. This product performs an acid attack on the enamel and 

 dentin. An application time of approximately 15 seconds must be respected in order to 

 to remove the smear layer without demineralizing the dentin in depth. 

 The etching gel is rinsed thoroughly, for a time at least equal to that 

 of its application The dental surfaces are then gently dried. A 

 Intensive drying prevents the formation of the hybrid layer and increases the risk of 

 postoperative pain. The product containing the primer and adhesive is then 

 applied. It helps rehydrate surface proteins to ensure the 

 formation of the hybrid layer. This adhesive agent is polymerized. 

 Membership is obtained in 1 step: 

 Thanks to the 7th generation of adhesives, it is possible to carry out etching 

 dentin enamel, dentin treatment and adhesive placement in one 

 single step. Following the manufacturer’s recommendations, the product is put in place 

 and polymerizes it. The adhesive layer is created in a single step. Every time 

 that we are led to use self-etching products on preparations where 

 the enamel surface is large, it is advisable to carry out preliminary etching of 

 enamel with orthophosphoric acid (Fig. 1-8).9 

• Bonded inlays/onlays/overlays:

Inlay: It restores one to five surfaces of the crown of a tooth, without ever covering the cusps. The occlusal surface is always involved with one or two proximal surfaces, and with a possible extension into the vestibular or lingual groove for molars.

Onlay: An onlay is an extension of the inlay when partial cusp coverage is required. It replaces one to three cusps. The tissue loss is more extensive, so the prosthetic volume will be greater.

The overlay (table top): The overlay is an extension of the onlay when total coverage of the cusps is necessary. They give the practitioner control of the DVO.

It is also called a “partial crown” because of its peripheral limits, which are clearly supragingival compared to the limits of conventional crowns.

Four types of overlays are possible, from the most basic form (table-top) to the most elaborate form (type IV) in the case of devitalized teeth.

Medium bridge anchor inlays/onlays/overlays:

Combining tissue economy, preserved aesthetics and clinical perspective, medium bridge anchorage inlays/onlays allow missing teeth to be replaced when the implant solution is ruled out, while avoiding the much more mutilating total peripheral preparations of conventional bridges.

1. indications:
   • Pulped teeth to maintain aesthetics.
   • Means of single anchoring or a low-load bridge.
   • the presence of corrosion and cracks; – unfavorable occlusal anatomy (closed cusp angle); – parafunctional occlusion.

Teeth prone to decay have a low amount of enamel, which contraindicates bonding.

Mechanical retention is low compared to partial and total crown preparations, therefore a short crown is unfavorable for bonding inlays-onlays-overlays.

Post-operative hypersensitivity is one of the disadvantages of dentin adhesion, so bonding should be avoided on teeth from the outset.

hypersensitive or with large pulp (the creation of grooves for the bonded bridge anchoring onlay reaches the pulp).

Benefits :

• Limited dental mutilation and preservation of aesthetics.
• Easy access to edges and for finishing.
• Easy hygiene and protection of the marginal gum.

4. Principles of preparation of bonded inlays-onlays-overlays:

For medium bridge anchor inlays/onlays/overlays:

What will differ is the fact that for MABs it is imperative to obtain parallel insertion axes, which may require modifying the usual geometry of the preparations and thus requires greater demands in the design and production of these preparations.

That it is intact, or at least that the losses of substance or the restorations present can be of a sufficiently small size to be able to serve as an additional retention

 That it is in normal position on the arch

 That the pulp chamber is sufficiently far from the preparation to avoid the risk of pulp damage

 That its Le Huche index is low

Le Huche Index: This is the difference in millimeters between the largest mesiodistal diameter of the tooth (at the anatomical contact points) and the mesiodistal diameter at the cervical level of the preparation. When the difference is large (i.e., greater than 2.7 mm), the preparation presents a risk to the pulp, and often overflows into the visible proximo-vestibular regions.

5. Chronology of practical implementation: 
   1. Isolation of the affected tooth 
   2. Treatment of the prosthesis according to the material (can be carried out in the laboratory or at 

 time of insertion in the mouth): 

1.  

2. =
3. Bonding to metal alloys was first achieved by: macroretention 

 (perforated fins of Rochette bridges); then microretention by alumina sandblasting. And 

 4-META (Superbond®) or MDP (Panavia®) type adhesives, 

 Precious alloy: surface treatments: deposit silica on the surface of the metal. 

 coupled to the bonding resin by the application of a silane., mechanical fatigue and 

 thermal seems to degrade the adhesive layer quite quickly. The recommended protocol 

 is therefore to sand the prosthetic arch with 50 lm alumina, then use a resin of 

 type 4-META or Panavia®. 

3. Tooth surface treatment (etching, adhesive and primer) 
4. Applying the glue 
5. Insertion of the prosthesis on the preparation 
6. CAD/CAM: 

7. The pulpless tooth:

For preparation:

For restoration:

8. Conclusion :

Given the significant progress in adhesion, traditional dentistry is increasingly moving towards micro-invasive adhesive dentistry, the various techniques presented of which were only a prelude to contemporary “micro-dentistry”.

Adhesive dentistry offers solutions that meet aesthetic , functional and biological requirements, while presenting a very good survival rate and a high degree of patient satisfaction .

BONDED RESTORATIONS: INLAY, ONLAY, OVERLAY

  Untreated cavities can cause painful abscesses.
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.
Decayed baby teeth can affect the health of permanent teeth.
A soft-bristled toothbrush protects enamel and sensitive gums.
 

BONDED RESTORATIONS: INLAY, ONLAY, OVERLAY