Reconstructions by stratification
I-Introduction
Direct or indirect adhesive restorations are among the most popular because they can be performed in one session, are reliable in the medium term thanks to constantly improving enamel-dentin adhesion, and are financially accessible to the greatest number of patients.
II- Mechanism of enamel-dentin adhesion
1-At the enamel level:
- Acid etching of enamel causes microcavities and roughness on the enamel surface
- These micro wells will be filled by the adhesive resin which, once polymerized, creates micro-keying responsible for adhesion.
Scanning electron microscope micrograph of an enamel surface. In A, the surface has not undergone any acid etching. In B, the surface has undergone etching with phosphoric acid (37% for 30s) (x 2700) (Hitmi et al., 2002)
2-At the dentin level:
Acid etching of dentin causes:
- Removal of smear layer
- Opening of the dentin tubules by demineralization of the peritubular dentin
- Demineralization of the intertubular dentin and exposure of the collagen fiber network
| Fibrillar network of collagen in the SEM when it is stable thanks to the water it contains. According to DEGRANGE |
| Collapsed collagen fibrillar network after drying, using SEM. According to DEGRANGE |
The adhesive once applied to the dentin:
- It makes chemical and mechanical bonds with the collagen fibers, thus forming the hybrid layer
- It penetrates into open tubules and achieves mechanical adhesion in the form of Tags
III- Restoration on anterior tooth
3.1 Definition of the stratification technique
It is a technique initiated and developed by Lorenzo VANINI 1996 And we can retain as a definition: “stratification is a technique of placing a composite material by adding successive increments, allowing the use of different colors and consistencies, to improve the final functional and aesthetic quality of the restoration”
- Composite restoration
3.2.1. Indications
- Agenesis of the maxillary lateral incisors
- Transformation of a canine into a lateral
- Closure of a diastema
- Carious lesions or wear lesions
- Coronal fracture
3.2.2. Contraindications
- Inability to obtain a watertight operating field.
- Preparation limit beyond the enamel-cementum junction.
- Too much loss of substance.
- Patient at high risk of caries and/or insufficient oral hygiene.
- Allergies to one or more components of the composites
3.2.3. Classical stratification
3.2.3.1 Classic 2-layer stratification “Dentin composite resin + enamel/Incisal composite resin”
- This concept consists of a monochromatic reconstruction of the loss of substance using “body” composites to which “incisal” is added if necessary.
(B): The dentin mass layer (I/T): transparent incisal mass
3.2.3.2 Classic 3-layer stratification “Opaque composite resin/dentin + enamel composite resin/body + incisal/transparent composite resin”
- Opaque wall → enamel-dentin body → incisal
This technique is based on a polychromatic reconstruction using opaque dentin masses, body enamel masses, and transparent incisal.
(B): The dentin mass layer (E): enamel mass
(I/T): transparent incisal mass
3.2.4.Modern stratification:
3.2.4.1. Modern 3-layer stratification or histological stratification
- Palatal enamel → Dentin → (Effect masses) → Vestibular enamel
This concept is based on the application of three layers of resins that faithfully mimic the properties and location of natural tissues, thus allowing a spatial organization identical to the dental structure.
The natural enamel is replaced by a mass of composite enamel both vestibularly and palatal.
The dentin is reconstituted using dentin composite masses of varying saturations.
3.2.4.2. Modern 2-layer stratification or stratification without palatal enamel
- This second method uses:
-a mass of opaque dentin in the palatine region.
-an enamel mass on the vestibular surface only.
- Here, the mass of opaque dentin in the palatine region is greater, providing an effective barrier to incident light regardless of the anatomical shape of the incisors.
3.2.5. Clinical implementation ( Anatomical stratification according to VANINI)
- analysis and preliminary clinical steps
3.2.5.1.1 Tooth color map
- Definitions:
-Schematic support or diagram containing the essential guidelines for the clinical restoration to be carried out.
-Reference plan for restoring the tooth in its natural color.
- Remarks :
– Complete before any restoration procedure (especially before installing the dam).
-Use a constant temperature light of 5000K.
-Rely on digital photography.
- Description :
On the front : the 5 dimensions of color according to VANINI, the different types and tones specific to each dimension, the corresponding composites.
On the back: representation of the different types associated with: Intensives. Opalescents and Characterizations.
On the front On the back
Chromaticity <BC>:
Hue and saturation of the dentin body.
Recorded in the middle third.
4 pure shades (1, 2, 3, 4) and 3 hybrid shades (1.5, 2.5, 3.5) corresponding to the shades of A VITA® to which 7 Universal Dentine composites are combined.
Animation of color by variation of saturation: the chromaticity desaturates from cervical to incisal and from palatal to vestibular.
Brightness <V>:
Related to enamel.
Recorded in the center of the tooth.
It comes in 3 shades
The intensives <I>:
Areas of hypomineralization of the enamel.
4 types:
1-in a circle: isolated spots located most often in the incisal third
2-in clouds: smaller and denser spots found in the middle and incisal third.
3-snowflakes: tiny dense spots occupying the entire surface of the crown.
4-in horizontal bands: milky bands affecting mainly the middle and incisal third.
2 shades of white: -w, cool white, -m, warm white, milky.
2 composites associated IW and IM.
The opalescents <O>:
Confined to the incisal third.
5 types:
- 1-3 nipples
- 2-3 split nipples
- 3-in-one comb
- 4-in window
- 5-in spot
3 tones: Blue, Grey, Amber.
3 associated composites OBN, OG, OA.
The <C> characterizations:
In dentin:
-type 1: nipples:
The free edge in nipples is associated with a small white or orange area between two lobes at the level of the incisal third and enhancing the brightness,
-type 2: in bands:
It appears as a wide horizontal band of white or amber color at the level of the middle and cervical thirds
In the enamel:
-type 3: on the margin: it forms a small white and/or amber line highlighting the free edge.
-type 4: stain: it represents a hypomineralization stain that can be found in all areas of the tooth,
– type 5: cleft: this is a vertical, transparent, yellow or brown crack/fissure in adult and elderly teeth.
- Tones: White, Amber, Brown, Yellow.
3.2.5.1.2 Silicone shape and key
Reproduction of the general shape of the decayed tooth can be facilitated by the use of a silicone guide.
3.2.5.1.2.1 The direct method by Mock-up:
-A reconstruction of the loss of substance is carried out using a monochrome composite resin, in the mouth, without etching or prior bonding protocol.
-This temporary reconstruction must meet the anatomical-functional criteria of the tooth in terms of aesthetics, functionality and phonetics.
-Then a medium viscosity silicone key is recorded and the temporary composite removed.
-This technique will be preferred in cases where: the loss of substances is not very significant, and if there is an old restoration that is anatomically satisfactory.
3.2.5.1.2.2 The indirect or Wax-up method:
In cases of more significant substance loss or if the change in anatomy affects several teeth in the smile
It’s necessary:
-An alginate impression from which the plaster model is obtained.
-A wax-up will then be performed following the patient’s anatomy and occlusion.
-The silicone key is then taken from the model and will serve as a guide for layering in the mouth.
3.2.5.1.3. tooth preparation
-Installation of the dike
– Beveling the enamel
-Etching of enamel and dentin
-Application of the adhesive then photopolymerization
3.2.5.1.4. Stratification
The palatal surface : a thin layer of enamel composite (not exceeding 0.4 mm) is spread on the key, then it is repositioned on the tooth
The proximal face: it is made using a 0.4mm enamel composite after the placement of a transparent matrix and interdental wedges
Dentin mass: According to VANINI, each tooth has three degrees of chromaticity:
– raised in the cervical third,
-average in the middle third
-weak at the incisal level.
Therefore, the placement of dentin must meet the need for desaturation of:
-the cervical part towards the incisal part of the tooth and,
-the palatal part towards the vestibular part
It is based on masses of different saturations: starting with a saturation two degrees higher than that of the final color or “base chromaticity” previously recorded and ending at the same saturation as that of the final hue.
However, the number of dentin shades required depends on the size of the substance loss. Thus, a single dentin mass will be used for small cavities, two for medium ones and three for large ones.
The lobes are made gradually
High diffusion layer
The reproduction of the protein layer is carried out with Glass Connector (viscous resin, white in color, characterized by high fluorescence and allowing the modulation of light diffusion at the level of enamel and dentin).
The Glass Connector will be placed on:
-the vestibular face of the palatal enamel
-dentin masses.
Finally, it will be polymerized
Characterizations, Intensives, Opalescents
Characterizations
The most important are those of the nipples and the free edge, which will be carried out using white (OW or IW) or amber (OA) masses.
Opalescent masses :
They are placed between the nipples, in the area between the body dentin mass and the incisal edge.
Their purpose is to create the shadow effect and reproduce the natural halo
Intensive masses:
Are placed in very thin layers according to the data collected when establishing the chromatic map.
Vestibular enamel layer
The vestibular enamel layer, thin in the cervical region, thickens towards the incisal edge
It does not exceed 0.4mm in thickness.
Once the last layer of enamel has polymerized, it is advisable to cover the surface of the restoration with a layer of glycerin gel and perform an additional cycle of photopolymerization.
Finishing, polishing and buffing :
Finishing itself:
– Finishing the vertical contour.
– Finishing the horizontal outline.
– Finishing of the surface macrotexture.
-Enamel growth curves (micro-texture).
Medium grit diamond burs, multi-blade burs, abrasive strips, greenstone point, silicone tips
Polishing:
Give shine to surfaces while retaining the texture details obtained.
Brush + 3 micron then 1 micron diamond pastes.
Abrasive belts of decreasing grain size + diamond pastes.
Polishing:
Perfect the surface condition
Aluminum oxide paste + polishing felt
Clinical case:
In the present clinical case – rare dental fusion (synodontia) at the level of the upper incisors 11/12 and 21/22, with diastema in a young patient of 15 years old
3.3 Direct composite vestibular veneers:
3.3.1 Indications:
– Transient
– Structural alteration; dyschromia, hypoplasia and severe vestibular erosion.
3.3.2 Advantages:
-Less expensive, quick, easy technique performed in a single session in the chair.
3.3.3 Disadvantages:
-Wear of the composite and change of color in the long term.
3.3.4 The therapeutic sequence:
-The choice of the appropriate shade of composite must be made before starting the enamel preparation.
– Partially strip the enamel, leaving enough space to obtain correct contours of the filling.
-The free edge must be abraded when it is necessary to enlarge the length and shape of the tooth.
-A small proximal and cervical cavity will be formed to facilitate the placement and finishing of the composite.
-The diamond bur must be held parallel to the tooth surface to ensure uniform enamel clearance.
-Application of the etching solution (with phosphoric acid), application of the bonding adhesive and photopolymerization
-Assembly of the composite lamination and finishing
– Laying of a low viscosity resin on the surface of the composite and photopolymerization
IV-Restoration techniques on posterior teeth:
- Horizontal layering technique:
4.1.1 Indications:
-Occlusal and proximal cavities of small extents.
- Technique:
The obturation method consists of the application of several horizontal layers of composite resin, each layer (approximately 1 to 1.5 mm thick) must be polymerized from the occlusal surface.
4.2 Oblique stratification technique:
- Indications:
-Medium volume occlusal cavities .
- Technique:
Applying the composite in oblique layers, followed by polymerization using a high-power lamp is recommended (>500 mW/cm²) through the walls, which significantly reduces polymerization stresses.
4.3 Composite-up technique
4.3.1 Indications
-Class I restorations.
-Class II restorations on premolars.
-Small to moderate sized Class II restorations on permanent molars.
4.3.2 Technique:
The technique requires implementation under a dam and involves 4 stages:
-Cavity preparation and dentin hybridization to effectively protect the dentino-pulp complex.
-Placement of an interdental wedge and a thin, curved metal matrix to facilitate the creation of contact points.
-Placement of a chemically polymerizable fluid composite on the base of the cavity
-Restoration of the occlusal portion using the “composite-up” technique. This technique involves a multi-layer method, each layer of which is light-cured. Once the occlusal portion is in place, the surface of the restoration is finished by applying and light-curing (40 seconds) a thin layer of flowable composite.
Composite-up technique
4.4 Effective placement technique:
4.4.1 Indications:
– Absence of opening of the carious cavity.
4.4.2 Advantages:
-Technique is efficient and effective.
-Improving quality and clinical execution.
4.4.3 Technique:
-Isolation of the tooth with rubber dam.
-Reproduction of occlusal morphology using a transparent silicone occlusal key for impression
-Application of etching acid to the prepared cavity.
-Rinse + dry
-Application of the adhesive and photopolymerization
– Oblique stratification of the composite
-Assembly of the last layer of composite using the silicone key and photopolymerization through this transparent key
-Polishing and application of the last layer in fluid resin and photopolymerization
4.5. Occlusal limit optimization technique:
This technique aims to avoid excesses at the occlusal level. This aesthetic dentistry technique allows the creation of direct reconstructions that are almost undetectable.
-Preliminary steps: recording the occlusion and removing the defective restoration
-Tissue conditioning: etching with 37% phosphoric acid, selective drying, application of the adhesive system and photopolymerization.
-Application of the composite strip using a spatula, and creation of the outline of the marginal composite applied to the palatal limit.
-Application of the composite strip on the vestibular limit, the cavity bordered, we proceed to the creation of the cusps while leaving a space for the last layer of composite.
-Filling the bottom of the cavity with injection of a fluid composite or oblique stratification
-Finishing, polishing
- Sandwich technique:
4.6.1 Closed sandwich:
4.6.1.1 Indications:
-Site 1: stage 2,3.
-Site 2: stage 2,3 (in the case where the cervical limits are supragingival).
4.6.1.2 Technique:
-Condition the cavity.
-Place the CVIMAR in sufficient quantity (dentin substitute) and let it harden completely.
-Trim the CVIMAR to expose all the enamel marginal limits.
-Apply an etchant to the CVIMAR and enamel for 15 seconds.
-Wash and dry without dehydrating the CVIMAR.
-Apply a thin layer of bonding resin with the enamel.
-Place the composite resin using a successive layer technique.
- Open sandwich :
4.6.2.1 Indications:
-Site 2: stage 2,3.
-The cervical limits are subgingival or juxta-gingival.
4.6.2.2. Advantages
-Better seal than a composite restoration when enamel is absent
-Tolerance to implementation in difficult conditions.
-A tolerance for implementation for practitioners with little experience in the field of bonding.
-A capacity to dissipate the constraints inherent in the polymerization shrinkage of the overlying composite. These characteristics are particularly interesting in the case of proximal restorations, which remain the preferred site of recurrent caries.
-Ease of implementation, given that a large layer of CVIMAR can be placed in a block, unlike composite.
- Technique:
-operative field
-dentin curettage
-formwork using a metal matrix
-surface treatment using a polyacrylic acid solution is carried out for 15 to 20 seconds.
-Set up CVI and wait for the setting time
– Oblique stratification of the composite
-Removal of the matrix and control of the occlusion using articulating paper
-Finishing + polishing
4.7. Splint technique:
Splint technique restorations are made by molding the composite using a thermoplastic splint made from the wax-up.
In cases of more significant substance loss or if the change in anatomy affects several teeth:
It’s necessary:
-An alginate impression from which the plaster model is obtained.
-A wax-up will then be performed following the patient’s anatomy and occlusion.
-The thermoplastic splint is then taken from the model.
– The thermoplastic splint is filled with the composite and placed in the mouth under pressure then photopolymerized.
– Finishing and controlling occlusion
4.8. “Fast Track” filling technique:
It uses a new composite technology called <Bulk Fill>
- Clinical stages
-Operating field
-Etching and application of the adhesive
-Installation of the low viscosity Bulk Fill composite and photopolymerization
-Installation of high viscosity Bulk Fill composite and photopolymerization
-Occlusion control and polishing
4.9. Indirect technique for layering composites <inlay, onlay and overlay in composite>
4.9.1 Definitions:
Inlays:
According to the French-speaking dictionary of conservative dentistry terms:
An inlay: is an intra-coronary prosthetic piece assembled by gluing or sealing, intended to restore a loss of dental substance not requiring cusp coverage.
Onlays :
The term onlay is used when the prosthetic piece provides cusp coverage.
Overlays:
Cast restoration covering the entire occlusal surface, the two proximal faces as well as the tops of the cusps which are covered
4.9.2 Indications:
-Restoration of posterior teeth with medium to large cavities.
-A failed dental restoration.
-Restore occlusion to increase the vertical dimension of occlusion.
-Use as a bridge anchor in joint prosthesis, to protect abutment teeth or hook supports.
-Allergy to Ag, Pb or other constituent(s) of silver amalgams whose vitality would be compromised when creating a retentive cavity.
4.9.3 Contraindications:
– Insufficient oral hygiene.
-Cast alloy (gold) inlays are contraindicated when the height, volume of the tooth and size of the cavity are insufficient.
-Parafunctional habits (bruxism) and excessive wear of the teeth.
-Movable tooth.
– Large breast.
-Hypersensitivity.
4.9.4 Advantages:
-A valuable saving of dental tissue.
-Precise functional anatomical restoration.
-Perfect biological tolerance.
-A watertight seal, particularly at the cervical level.
4.9.5 Disadvantages:
-The clinical stages are long.
-The cost of treatment is more expensive.
-Difficulty of execution: risk of over-contouring or under-contouring the restoration.
-Thermal conductivity especially in deep cases.
-The need to have a good emergence profile: the most difficult criterion to respect in the direct method.
4.9.6 General principles of cavity preparation for inlay-onlay:
-Axial walls with a draft of approximately 10°.
-A wide isthmus (not less than 2mm).
-Rounded internal angles.
-The bottom of the main cavity must be flat.
-The occlusal edges do not coincide with the occlusal contact points
– Edges forming a 90° cavosuperficial angle.
-The covering requires an occlusal space of at least 1.5mm (for onlays).
-The depth of the cavity must be at least 2 mm
-Cervical limits, must be juxta or supragingival.
4.9.7 Description of the technique:
4.9.7.1 Direct technique:
-Local anesthesia.
-Removal of old restorations.
-Laying the surgical field: dam.
-The preparation must meet the general principles described previously
-The cavity having retention zones, the undercuts are filled by the dentin bonding of a fluid composite
-The cavity is then isolated with a gel compatible with the composite material.
-The cavity is restored using the composite resin layering technique.
-Using a thin, rigid instrument, the inlay is freed from the cavity.
-Finishing, polishing and buffing of the inlay is carried out outside the oral cavity.
-Trying and adjustment of the prosthetic part
-Etching of the tooth and the intra-back of the prosthetic part
-Application of the adhesive on the tooth and the intra-back of the prosthesis
-The prepared glue is placed in the cavity and the inlay is immediately placed.
-The inlay is then light-cured while being held firmly in place using an instrument.
-Finishing and control of occlusion.
4.9.7.2 Indirect technique:
This technique includes 2 clinical sessions and one laboratory session.
1st Clinical Session :
-Preparation of the cavity.
-A protective base on the dentin .
-Impression taking with polyether silicones.
-Choose the shade.
-The whole thing is sent to the laboratory.
-The cavity is sealed with temporary cement
In the laboratory:
-Realization of the unitary positive model.
– Making the inlay – onlay: after applying an insulating gel
-The material is pressed and shaped into the model cavity after photopolymerization.
– Touch-ups and finishing are done.
2nd clinical session:
-Trying in the inlay.
-Collage.
Reconstructions by stratification
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