Introduction to bonded prosthesis

Introduction to bonded prosthesis

1/ INTRODUCTION

The constant improvement of materials and techniques has made it possible to gradually extend the indications for bonding in all dental disciplines. 

This is how we saw the development of a purely prosthetic aspect with the development of the “Bonded Bridge” proposed by Rochette and the bonded veneers.

The success of these restorations results from the fact that the technique requires dental preparation that is as non-mutilating as possible, allowing other solutions in the future in the event of failure.

2/ GLUED BRIDGES

2.1/ ​​Definitions: 

Is a rigid prosthetic piece similar to a conventional bridge, but instead of completely covering the teeth bordering the gap (total peripheral anchoring), we simply glue support elements to the pillars in order to replace one or two missing teeth. 

These support elements are fins, located mainly on the palatal faces of the abutment teeth and occlusal supports located in the non-functional part of the tooth (after studying occlusal contacts).

Introduction to bonded prosthesis

2.2/ Clinical data

Before any prosthetic decision, it is essential to carry out a precise clinical observation.

This study must be imperatively completed by a study of the casts mounted on a semi-adaptable articulator in order to evaluate:

• the available crown height
• dimension of free space (edentulism)
• the value of the Huche index
• occlusal contacts of the support and guide cusps in static and dynamic states
• the proximal contact point
• the proximo-vestibular angle position

This involves carrying out a classic observation of the joint prosthesis, specifying these particular points.

2.3/ Indication:

• single tooth replacement
• periodontal or post-orthodontic retention
• mixed restorations
• favorable occlusal relationships
• when the enamel surface is of good quality for etching

2.4/ Contraindications:

• replace multiple teeth (3 or more)
• unsightly abutments: malformed or misaligned teeth cannot be aesthetically improved by bonding to the lingual surface (bonded veneers)
• insufficient healthy enamel: cases of carious lesions or large fillings which do not allow an adequate bonding surface.
• overbite
• short teeth
• bruxism and parafunctions
• very mobile teeth
• the presence of diastema.
• Unfavorable Le Huche index

2.5/ Advantages:

• minimal dental reduction: we do not weaken one element to replace another.
• supragingival limits: less aggressive for periodontal tissues.
• respect for contact points.
• absence of pulp complications.
• no anesthesia less anxiety for patients
• Improved aesthetics: by avoiding the metal collar (high smile line).
• reduced cost

2.6/ Disadvantage

• Possible detachment: in case of failure === other type of prosthesis
• Limited indications
• Visibility of the metal: previous aesthetic concerns: the etched framework in front gray can be seen by transparency at the level of the thin incisal edges, translucent reducing the shine of the tooth more opaque bonding resins.
• The number of teeth to be replaced is very limited.
• Need for teeth in good position.

2.7/ the different types of bonded bridges: According to the preparation:

• Bonded bridges without preparation 
• Bonded bridges with preparation 

2.7.1. Bridges without preparation : This is the concept of the bonded bridge imagined by Rochette which integrates the notion of reversibility linked to the absence of preparation, apart from surface treatments. 

• The many failures encountered over time explain the bad reputation of this type of rehabilitation.
• It still has indications as a waiting prosthesis, nevertheless requiring rigorous clinical monitoring because the risk of caries is significant in the areas of detachment.
• Retention is ensured only by the bonding joint; the surface area of ​​the fins must be as large as possible. 
• It is however limited: by aesthetic factors, the shape of the teeth (Le Huche mesio-distal index), occlusal requirements and the insertion axis chosen to optimize this bonding surface. 

Indication: 

• Abutment teeth free of caries

•  favorable Le Huche index. 
• Favorable anterior occlusal relationships with very slight end-to-end overlap and no associated parafunctions. 

The limits :

• Clinically, the cervical limit is located on the enamel, and at least 1 mm from the marginal gingiva (to limit the harmful effects of the inevitable cervical overcontours. In addition, this supragingival limit facilitates the placement of the dam essential for good bonding). 
• Occlusally , the limit of the fins is located on the one hand, at least 1 or 2 mm from the free edge so as not to interfere with the incisal transparency of the enamel and on the other hand, strictly below the functional paths. 
• At the proximal limits , the principle of balance of the bonding surfaces on either side of the gap must be respected. That is to say, take as many teeth as necessary to cover a given surface (e.g.: a surface ranging from 30 mm2 for the replacement of a central incisor to 1 cm2 for a maxillary molar).
•  The faces proximal to the edentulous area can be exploited to the maximum and ensure primary stabilization of the bridge by increasing the encircling effect of the wings. 

2.7.2. With preparation : This is an evolution of Rochette’s concept which tends to respond to the periodontal and biomechanical occlusal problems encountered with bridges without preparation.

– The main idea is to carry out enamel preparation of the entire bonding surface. The fins are then embedded on the abutment elements without altering the initial dental morphology. 

– The mobilization constraints undergone by the bonded bridge are prevented by specific preparations aimed at creating stabilizing and supporting surfaces; the notion of reversibility has then disappeared. 

– These preparations are however not very mutilating because they are of the film type , allowing significant savings to be made on dental tissue.

2.7.2.1/ Preparation of abutment teeth:

Bonded bridges allow us to solidify or replace teeth with  truly minimal supragingival dental modification ; all other treatment options are still possible after failure.

2.7.2.1.1/ general principles of preparation: bonded bridges must meet the requirements of:

* Retention: which is ensured by the parallelism of the walls of the modified tooth, the surface of the tooth covered by the fins, and by the bonding material.

*Sustentation : which is obtained by the dental supports prepared on the teeth (occlusal support)

*stabilization : which is obtained by wrapping the fin around the tooth (preparation of the proximal faces) this stabilization is maximum as soon as the fin envelops the tooth over more than 180°.

2.7.2.1.2/ dental preparations: before any preparation it is necessary that:

*The anatomy of the abutment teeth is analyzed and the optimal insertion axis is chosen based on respect for the enamel and aesthetics (bonding is four times greater than the enamel/dentine level).

*Mark occlusal contacts

*Delimit the bonding area that can be attributed to the fin of each pillar.

*Perform occlusal corrections.

Introduction to bonded prosthesis

A/choice of the insertion axis of the bonded bridge

B/Enamel preparation:

It is achieved using the controlled penetration technique and allows for a uniform reduction of the prepared surface of approximately 0.6 mm.

This reduction which localizes the prosthetic limits is necessary to design sufficiently rigid prosthetic fins.

B.1/preparation of the proximal face:

• On the side of the edentulousness at the level of the thinnest pillar: For aesthetic reasons, the preparation stops behind the point of contact, but as close as possible to this (without crossing the point of contact), to promote the pillar surround (stabilization)
• On the occlusal side, the proximal limit emerges behind the incisal edge of the anteriors or in the lingual slope of the vestibular cusps (occlusal covering) for the posteriors.
• On the cervical side, the proximal limit leaves the area of ​​the contact point forming an arc that approaches the gingiva where it becomes the LC

B.2/ preparation of the finishing line:

• The finishing line defines the extent of the bonding and conditions the importance of the retention that can be obtained by adhesion.
• It will always encompass a maximum of enamel while taking into account aesthetic and occlusal imperatives.

B.2.1) preparation of the cervical finishing line:

Fillet-shaped: to allow the framework to end in sufficient thickness without over-contouring (harmful to periodontal health).

B.2.2) preparation of the occlusal finishing line:

Anterior teeth :

– It must interfere as little as possible with areas of high transparency and therefore remain at a distance from the free edge. 

– Is a light fillet similar to that of the cervical LF using a small 1.5 mm O diamond ball bur which allows to easily join the proximal finishing lines by passing at a distance (1-2 mm) from the free edge of the abutment tooth without touching it. It follows parallel to the free edge and approximately 2 mm offset for the upper teeth and 1 mm for the lower teeth.

The posterior teeth

• is always located on the vestibular side of the lingual cusp with overlap of the cusp tip.

C/Specific preparation:

• They concern all the complementary devices aimed at providing geometric surfaces opposing the destabilizing forces of biomechanical origin.
• This preparation is divided into three clinical stages:

• preparation of axial walls; (retention)
• preparation of the sinking stops; (suspension)
• preparation of locking systems (stabilization)

C.1) Preparation of the axial walls:

– It is carried out using a cylindrical diamond instrument with a quarter-round fillet which removes the axial walls ( parallel to the chosen insertion axis).

C.2) Preparation of the driving stops

– These stops provide support , their production principles differ depending on the anatomical shape of the teeth concerned:

C.2.1/anterior teeth:

 The cingulum is not very extensive and, due to its slope, leads to the creation on the lingual surface, using a cylindrical diamond instrument with a shoulder, of half-moon-shaped flats with a mesio-distal orientation (or V-shaped cingulate notch)

Introduction to bonded prosthesis

C.2.2/posterior teeth:

– On the other hand, they offer occlusal surfaces whose orientation is close to the desired support planes.

–  The preparation including the lingual cusps provides a first plane of support, the capacity of which is however insufficient.

– It is increased by the creation in the enamel of proximal support lodges or occlusal trenches made to the detriment of the marginal pits bordering the edentulism (affecting the main grooves); these supports will be spoon-shaped;

C.3 ) Preparation of locking systems

– These systems, based on the creation of grooves or dentinal tenons , have a stabilizing component and oppose rotational movements.

Introduction to bonded prosthesis

2.8/The impression: it appears deceptively simple, since it involves partial supra-gingival preparations, or even absent, for bridges without preparation; in fact, there are undercuts and sometimes highly retentive embrasures which can be detrimental to obtaining a good registration.

• To prevent tears, the embrasures are filled with temporary cement.

• pulling effects are reduced by using low viscosity impression materials that perfectly wet tooth surfaces
• The preferred choice is reversible hydrocolloids and hydroalginates. 
• It is also possible to make the impression with polyethers used with an individual impression tray in single-phase technique, and finally with polyvinyl-siloxanes of the “hydrophilic” type used in double mixture.
• The impression of the dentinal post housings is facilitated by the use of preforms.

2.9/The bonding protocol:

1. Treatment of the prosthetic intra-back :

• for non-precious metals: 50 µm or 250 µm alumina sandblasting followed by chemical etching.
• for precious alloys based on gold or palladium: the sandblasting described above is followed by oxidation. 

2. Treatment of dental surfaces : The surfaces to be bonded must first be isolated by an operating field. “The reference technique is the placement of a rubber dam on the prepared teeth and the first adjacent teeth” . 

• The tooth surfaces are carefully cleaned using a brush and a mixture of water and pumice powder.
•  rinsing and drying 
•  Etching of dental surfaces using orthophosphoric acid gel applied for 30 seconds per element
•  careful rinsing of equal duration. 
• In case of dentin exposure, the dentin is locally treated by acid attack of a mixture of 10% citric acid and 3% ferric chloride in order to be able to create a hybrid layer with the adhesive.
• Drying is carried out using clean, dry air without dehydrating the dentin surfaces.

3. For bonded bridges, 4META resin is unanimously recognized as the best bonding material, it is marketed under the name Super Bond.

• The preparation of the bonding resin is carried out in a ceramic block hollowed out with three wells, refrigerated at 12°C and used according to the protocol.
• Using a brush, etch the prosthetic intrados and dental surfaces.  

• The mixture is immediately spatulated and immediately deposited on the prosthetic intrados.

4.  The bridge is then put in place and held under pressure. 

Introduction to bonded prosthesis

5. As soon as the excess becomes pasty, it is removed using an instrument
6. The end of polymerization is carried out if possible under pressure.
7.  The product requires 15 minutes to reach a polymerization rate of 80 to 90%.
8. After removal of the dam, the finishing of the peripheral limits is completed using a very fine-grained diamond instrument, followed by polishing. 

3/ Ceramic veneers:

3.1/Definition:

3.2/Indications:

• Color anomalies or irregularities:
• Shape anomalies: microdontia, atypical teeth, conoid incisors 
• Structural or textural abnormalities: dysplasia, dystrophy, erosion or abrasion
• Diastemas

3.3/Contraindications:

• Insufficient enamel surface.
• Devitalized teeth
• Unfavorable inter-arch relationship: overbite
• Parafunctions 
• Inadequate coronary morphology: too short
• Unit facets
• Cavities and fillings
• Poor and ineffective hygiene.

3.4/Preparation:

1/ Type I : Preparation without lingual return

• Reduction of 0.6mm, limited to the enamel of the FV,
• limited mesially and discally by a thin enamel edge, without crossing the proximal contacts. The LC is a thin fillet, the preparation ends at the free edge. 

2/ Modified Type I: recessed preparation without lingual return “in recessed window” is intended for very stocky teeth and cuspidate teeth.

more significant reduction: 0.5 and 0.8 to 1mm can be located at the level of the dentin.

• The LC is a real holiday
• At the free edge, we stop the reduction by leaving a border of enamel of a few tenths of a mm
• Preparation without interference with FP or occlusal.
• Indications: very massive canines / PM and 1st mol. >.

3/ Type II : Preparation with return on the free edge.

• The preparation is extended on the free edge and is accompanied by a return on the lingual face.
• For mechanical reasons the reduction of the free edge must be > 0.6mm -1mm) always without crossing the proximal contacts.

4/ Type III : preparation in half-jacket

• Final stage of facet before jacket preparation
• thick from 0.8 to 1.2 mm, the limits ( cervical , proximal, lingual) are marked edges.
• The proximal contacts are crossed and the proximal faces are parallelized (this is the equivalent of a preparation for a supragingival jacket)

3.5/The bonding protocol:

1. Tooth cleaning: pumice + water (mercryl)
2. Cleaning the facet 
3. Clinical trial
4. Etching the veneer: hydrofluoric acid
5. Neutralization: 2mm in sodium bicarbonate gel
6. Adhesive on the tooth and the veneer: leave for 30s and dry 
7. Installation of the photo-polymerizable composite 
8. Elimination of unpolymerized excess 
9. Photopolymerization 
10. finishing 

4/ other types of bonded prostheses:

• Inlays onlays 
• Corono-radicular restorations (with fiberglass post)
• The ceramic-ceramic peripheral crown.

Introduction to bonded prosthesis

Deep cavities may require root canal treatment.
Interdental brushes effectively clean between teeth.
Misaligned teeth can cause chewing problems.
Untreated dental infections can spread to other parts of the body.
Whitening trays are used for gradual results.
Cracked teeth can be repaired with composite resins.
Proper hydration helps maintain a healthy mouth.
 

Introduction to bonded prosthesis