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CLINICAL CONSIDERATIONS
Cavity Designs For Composite Restorations :
Association to Sturdevant designs of cavity preparations.
1) Conventional Cavity Preparation
2) Beveled Conventional
3) Slot Preparation Designs
4) Modified Preparation
5) Box Only
Conventional :
Are those typical for amalgam restoration.
Outline form : Necessary extension of external walls at an initial, limited, uniform dentinal depth resulting in the formation of those walls in a butt joint junction (90o) with the restorative material.
Primary Indications :
Preparation located on the root surfacesModerate to large Class I / II restorations.
-This design facilitates a better seal between the composite and dentin / cementum surfaces and enhances retention of the composite.
-Like in amalgam preparation, retention grooves and coves can be placed in the dentin.
-Usually prepared with diamond stone so that it produces rough surfaces , which increases surface area for retention.
Beveled Conventional :
-It is similar to the conventional design, box like walls, but with some beveled enamel margins. -Preparations done with diamond stone.
Indications :
-When a composite resin is being used to replace existing restoration.
- Mostly for Class III, IV and V restorations.
-To facilitate better marginal seal and bonding. Some accessible enamel margins may be beveled and then acid etched.
Advantages of Enamel Bevel :
Ends of enamel rods are more effectively etched.
Due to increase in surface area – stronger bond, better retention of restoration and reduces the marginal leakage.
Enables the restoration to blend more esthetically with the surrounding tooth structure.
This design is mostly used for anterior preparation and rarely used for the posterior restorations.
Modified :
-They have neither specified wall configurations nor specified pulpal / axial depths but they are solely dictated by extent and depth of the carious lesion / defect.
-The objective in this design is to remove the fault as conservatively as possible.
- This design conserves more tooth structure
- Round burs / diamond stones are used
-These preparations appear “scooped out” rather than with definite line angles and point angels.
Indication :
- For initial restoration of smaller, cavitated, carious lesion usually surrounded by enamel and for correcting enameldefects.
Box Only :
- Indicated when only the proximal surface is faulty. - Prepared with inverted cone / round diamond stone held parallel to the tooth. - Form of box is dependent on which diamond is used More box like with inverted cone. Scooped with round diamond.
Facial / Lingual Slot :
- If the lesion is in one of the proximal surface the access can be obtained either from facial / lingual side rather than through marginal ridge from occlusal direction.
- Diamond oriented at the correct occlusal gingival height and entry is made with diamond as close to the adjacent tooth as possible thus pressuring the facial / lingual surface.
- All the cavo surface margins should be 90o or greater.
Clinical Technique :
Initial Clinical Procedures :
A thorough examination, prognosis and treatment plan be finalized before the patient is scheduled for operative treatment.
Local Anesthesia :
- May be required for many operative procedures.
- Profound anesthesia contributes to a more pleasant and uninterrupted procedure and results in reduction in
salivation.
Preparation of Operating Site :
Cleaning the operating site to remove calculus, plaque, pellicle etc.
Prophylaxis paste containing flavoring agents, glycerin or fluorides are avoided to prevent conflict with acid etch, A slurry of pumice is recommended for this procedure.
Shade Selection :
- Special attention should be given for matching the color and translucency of the tooth to be restored. - The determination of shade of the tooth to be restored is done before the teeth are subjected to any prolonged drying, because dehydrated teeth become lighter in shade as a result of decrease in translucency.
- Normally teeth are predominantly white, with varying degrees of grey, yellow or orange tints. Color also varies and translucency, thickness and distribution of enamel.
- Like at incisal third i.e. ‘ w’ (mostly enamel) is lighter and more translucent than cervical third i.e. ‘ y ’(mostly dentin), whereas the middle 3rd i.e. ‘ x’ is a blend of incisal and cervical colors.
- Other factors like fluorosis, tetracycline stain in and Endodontic treatment also effect the tooth color.
- Most of the manufactures provide shade guides for their specific materials which are not interchangeable with other manufacturers.
-Also note cross reference the shades with those of Vita shade guides which is a universally adopted shade guide.
- Most of composites are available in enamel and dentin shades as well as translucent and opaque shades.
- However if additional shades are needed they may be obtained by mixing of two or more of the available shades together by adding color modifiers.
- Good lighting, either natural or artificial is necessary when color selection is made.
- Natural light is preferred, if no source of natural light color correct operating lights or ceiling lights can be used to facilitate accurate shade selection.
Dental operating light should never be used.
-While selecting, hold the entire shade guide near the teeth to determine the general color. -Then select and hold specific shade tab beside the area of the tooth to be restored.
- Shade tab should be partially covered with patients lip / operator’s thumb to create the natural effect of shadows.
-Make selection as rapidly as possible since physiologic limitations of color receptors in the eye make it increasingly difficult to distinguish between similar colors after approximately 30 seconds.
Isolation of the Operating Site :
Isolation for tooth colored restoration can be accomplished with,
1) Rubber dam ,2) Cotton rolls and retraction cords.
Rubber dam :
Heavy rubber dam is an excellent means of acquiring superb access, visibility and moisture control.
For proximal restorations – Isolate several teeth mesial and distal to the operating site.
For anterior restoration bylingual approach – it is betterto isolate all the anterior teethand include the premolars to provide the lingual access.
In Class V with facial approach – necessary to apply a No.212
retainer which may stabilized with impression compound.
Cotton Rolls (with Retraction Cords) ;
It is an alternative method of obtaining a dry operating field.
Cotton roll is placed in facial vestibule directly adjacent to the tooth being restored.
When restoring mandibular tooth, a second preferably larger cotton roll should be placed adjacent to the tooth in the lingual vestibule.
• When the gingival extension of tooth preparation is to be positioned subgingivally, or near the gingiva, a retraction
cord can be used
• If hemorrhage control is needed, a cord can first be saturated with a liquid astringent material.
Other Preoperative Considerations :
When restoring posterior proximal surfaces, a pre operative wedge should be placed firmly into the gingival embrasure which causes ;
1) Separation of the tooth from the adjacent tooth. 2)Creates some space to compensate for the matrix thickness.
Also, a pre-operative assessment of occlusion should be made to identify not only the occlusal contacts of teeth to be restored but also the occlusal contacts of adjacent teeth.
Restorative Technique For Composite Restorations (In General)
Once the tooth preparation is complete, the prepared tooth is ready for the composite insertion. Treating the prepared tooth for bonding requires etching and then application of an adhesive if only enamel is prepared, or a primer and adhesive if the composite will be bonded to the dentin as well as enamel.
Preliminary Steps for Enamel and Dentin Bonding Etching :
In 1959, Bunocore reported the effect of 85% phosphoric acid application. They were of little use until 1959, when the methodology was further explored and now is an integral part of any direct tooth colored resin restorative technique.
Though number of acids have been used like 10% acetic acid etc, at present 35% to 50% aqueous solution of phosphoric acid is used.
Recent reports state that much less as low as 15% can produce the same effect.
Other etchants used are like Oxalic acid, Nitric acid, Pyruvic acid, Maleic acid, EDTA etc.
Etchants are available in liquid and gel forms
Liquid forms are primarily sued to etch large surface areas of enamel such as for veneers, sealants and commonly used with cotton pellets, sponges or brushes.
However gel forms are preferred because they help in controlled application to the prepared walls including bevels __
This is done mostly with a brush, paper points, instrument or syringe can be sued.
The acid (liquid/gel) is gently applied to the appropriate surface to be bonded, keeping the excess to a maximum of 0.5 mm past the anticipated extent of restoration.
An etching time of 15 seconds for both dentin and enamel is considered sufficient. If for only enamel preparing 30 seconds is considered optimal.
The area is then rinsed with water for 5 seconds.
The area should be dried with clean dry air from the air water syringe if only enamel is etched. Dried etched enamel should exhibit a ground glass or lightly frosted appearance. If this appearance is not evident, the enamel must be etched again.
If both enamel and dentin have been etched the area must be left slightly moistened which allows the primer and adhesive materials to more effectively penetrate the collagen fibrils to form a hybrid layer, which is the basis for micromechanical bond to dentin.
Effects of acid Conditioning on Surface Enamel and Dentin :
Etching enamel ¤ Effects both the prism core and prism periphery by dissolution. Etching transforms the smooth enamel into a very irregular surface, ¤ and also increases the surface free energy.¤ The surface area will increase upto 2000 times to that of unetched surface. Enamel surface of interprismatic enamel will have an undercut.
Both valleys and depressions will leave an irregular surface and an average depth of 25 m, which help in the formation of resin microstage formation.
Etching will expose the proteinaceous organic matrix substance of enamel, which can add to the restoration in retention if it becomes adequately embedded within restorative enamel.
Much cleaning and acid conditioning of enamel will assure removal of substances like enamel cuticles, salivary deposits, plaques and adhesives to enamel thus exposing a cleaner, less contaminated and more wettable enamel surface for adhesion with restorative material.
Etching to some extent, removes the surface enamel which has been subjected to surrounding environment thereby exposing the fresh enamel which has sufficient surface energy to facilitate a reaction with the adhesion to the restorative material to be applied.
It is suggested by this acid treatment, a newly precipitatedphase of calcium oxalate and organic torture complexes could be created which can adhere to enamel and resinous substances.
Etching dentin
Bonding Agent :
It is essential to enhance the adaptation, retention and seal of composite resins to enamel and dentin by a prior application of resin bonding agent.
Resin Bonding to Enamel : Unfilled resin bonding agent with low viscosity are used to seal
the interface between composite resins and etched enamel thus developing a focus of micromechanical retention. The resin flows into the micropore to a depth of 10-20 m.
The following factors will influence the reliability of the bond :
Type and concentration of the etchant : 37% applied for a minimum of 15 seconds.
Viscosity of the bonding resin : logically a low viscosity resin will penetrate further than a high viscosity.
Contamination of enamel after etching. Reduce the efficiency of the bond.
Resin Bonding to Dentin :
The goal of resin dentin bonding agent is to attach composite resin to healthy dentin and to seal the dentinal tubules against the entry of bacteria and their toxins, also prevent both inward and outward flow of fluid from either the oral environment or the pulp. Effective bonding prevents post restoration sensitivity, caries and loss of the restoration.
Principles Apply to Successful Resin – Dentin Bonding :
Dentin should be etched to remove the smear layer and dentinal tubule plugs using 37% orthophosphoric acid for 15 seconds.
Etching should be sufficient to demineralize the surface layer of both intertubular and intratubular dentin, leaving collagen fibers exposed and available for a mechanical interlock with the resin.
The surface after washing the etchant thoroughly should remain
moist but not dry or over wet which helps the hydrophilic primer to guide and facilitate penetration of resin adhesive around the exposed collagen fibres.
These bonding agents requires application of adhesive if only enamel is prepared, or a primer and adhesive if the composite will be bonded to the dentin as well as the enamel.
Components of Resin Dentin Bond :
1. Hybrid layer (Resin-Dentin Interdiffusion zone) : It is a hydrophilic primer and a adhesive bonding agent penetrate approximately 5 m around and into partly and completely demineralized intertubular dentin on the cavity wall. This layer provides a small and a little retention for the resin dentin bond.
2. Resin tags : Prime and bonding agent from tags of resin upto 100 m long in the dentinal tubules. Micro mechanical bonding to partly diminished tools of dentinal tubules and resin tags themselves combine to provide the most of the retention achieved by resin-dentine bond
Once the enamel (and dentin) is etched, rinsed and left appropriately moist, the primer is applied to both surfaces.
After it is dried for 5-10 seconds the bonding agent /adhesive is applied.
Most contemporary bonding systems combine the primer and adhesive into single bottle, requiring only one application.
Matrix Placement :
Matrix:Device which is applied to the prepared tooth in order to create / simulate a missing wall to restore the tooth.
The matrix band an d retainer should be:Rigid enough o resist deformation from insertion forces (posterior restoration)
Flexible (anterior restorations), provide appropriate proximal contact and contour.
Prevent major excess of restorative material beyond the preparation margins on the proximal wall,
especially the gingival margin.
Easy to apply and remove
Should extend just above the marginal ridge and below the gingival margin.
To held it in place wedge is used.
o To gain separation of teetho To prevent overhang at gingival margin
Wedges used : Triangular wooden wedges – mostly used
Round tooth pick - Light transmitting wedge
Numerous matrix systems are available
Tofflemaire matrix – for Class II
Bitten ring with sectional matrices – Class II
Translucent / Polyester strip Class III and IV restoration in anterior teeth.
Placement of matrix sequence depends and varies from operator to operator.
Some prefer to do it before doing any bonding or any restorative procedure.
This provides the best isolation of the tooth preparation for enamel and dentin adhesion.
Also helps in assessment of any fracture in the tooth during application of wedge.
But with this sequence, chances of pooling up of bonding materials especially the adhesive along the gingival marginal junction. Some prefer to complete the bonding procedure and then place the matrix, which helps in minimizing pooling up of adhesive material. Either sequence may be used as long as meticulous technique is followed.
Insertion of Composite :
Instruments used for Insertion :
Usually Teflon coated instrument used, stainless steel not used as the material will stick to them.
Instruments – whichever used should be dry, clean and without any scratches.
Syringes and Burs :
These are used for flowable and other viscous composites
Arms viscous composites
Syringes flowable composites
RESTORING THE ANTERIOR TEETH CLASS III AND IV
Here whether the approach is lingual / labial first increment is placed on the gingival wall.
Care should be taken to completely visualize the gingival cavosurface area (can use retraction cords and rubber dam etc)
First increment which is placed should be 1.00 mm thick and the subsequent increments 1.5 mm thick.
Each increment is cured for 20 seconds and final increment for 40 seconds to 1 minute.
Curing is preferred from labial spect if lingual approach was used and viceversa in labial approach. But finally cured from all surfaces.
Here blending of shades is more important.
It depends on Extent of lesion, Labial involvement. From cervical Incisal area; closure of composite would
be from dark to light and translucent. Darker – cervicalLess dark – Middle 3rd Lighter - Incisal Translucent – Incisal edge
Similarly restoring fracture incisal edges / horizontal fracture of tooth care to be taken to blend the colour following the basic principles.
RESTORING THE POSTERIOR TEETH :
Light cured composite resins are generally sued for posterior restoration, because they are better resistant to occlusal wear.
Chemical cured composite shrink toward the geometric centre of mass. So this leaves a small contraction gap at the gingival margin.
Composite is strongly bonded to enamel on both buccal and lingual walls preventing gaps at these walls.
Photo cured / light cured composite resins shrink toward the light sources because compression resin closest to light hardens first. This in turn pulls the softer composite resin from the gingival margin, creating a gap.
Mass of compressive resin pulled to the occlusal area is twice that found in chemically cured resins, hence contraction gap is roughly as large.
To overcome this ;1) Incremental curing reduces, but does not eliminate completely.
2) A plastic wedge, which acts as a fibre optic extension can pull the compression gingivally to minimize gap formation.
3) Incremental technique although not ideal, should reduce the gingival contraction gap and stresses compare dot a
2 increment technique involving only occlusal curing, as might be done clinically.
- First layer – Placed and photo cured via the plastic wedge. - Second layer – Placed and cured occlusally.
Two improvements could be made in the most gingival increment.
1st regardless of tooth colour – a lighter coloured resin should be sued to ensure additional curing depth. 2nd before adding the final increment, a second, a occlusal
cure of the first increment to ensure complete hardening of mass.
4. This technique takes advantage of compressive resin contraction and uses only one 11-p3 mm. curve light. 1st increment : can be pulled lingually and gingivally
(via the light reflecting wedge at 90o angle to the light tip) before an addition occlusal cure.
2nd increment : Pulled buccally and gingivally before it receives an additional occlusal cure.
3rd increment : Hardened occlusally after placing a ball of pre polymerized composite to act as an internal wedge.
Additional occlusal increments may be necessary in large teeth. This design also minimizes pulling together of cusps.
5) An additional insurance – A small egg shaped ball of pre polymerized composite resin (shaped and cured on the finger) is wedge into unpolymerised composite resin at increment 3 against the
axial wall and band.
The composite resin ball acts as an additional wedge, placing pressure from within on the axial wall and mylar matrix.
Use plugger to kresist active downward pressure and expose increment 3 to the curing light.
Polymerization / curingFor chemically cured : No need of additional curing. For light cured – Each increment placed is cured for
20 seconds before placing the next over it.
Recently few authors suggest : “Soft start polymerization” in which initial increments are
cured of 10 seconds before placing the next over the previous one.
Which ever design is used, care should be taken to compress the increments so as not to have any voids between 2 increments.
Establishing Proximal Contact :
One of problems with compressive restoration is establishing proximal contact, since composites shrink after setting, coupled with the gap created by matrix – problem increases 2 folds.
Proximal contacts restored in 2 ways:
a) After curing the gingival increment upto the contact area, wedge and matrix remove and rest of restoration is carried out without matrix but in increments.
b) Duokodakis : Devised a technique which the proximal contact can be established at proximal areas. According to him width of contact area from contact area to opposing cavity wall is measured and area which is to be restored is also measured.
A small tube, containing compressive of measured width and length taken and cured and placed in the cavity and then restored in a normal way. This technique helps in maintaining proper size and shape of contact.
CAVITY PREPARATIONS :
Class I : Any of the designs – conventional or beveled or modified can be done. When there is a need to – provide increased resistance from and
For large preparations / restoration subjected to heavy occlusal forces – Conventional design.
Small to moderate restorations which no characteristic resistance form – Modified design.
Conventional Design : - Include the fissures from distal to mesial.
Depth of 1.5 mm/ 0.2 mm into dentin.
Facial and lingual extensions - Dictated by canine / old restoration material fault
Flat pulpal floor
Flat pulpal floor
• If any groove (facial / lingual extension) necessary have to bevel it resulting in 0.25 – 0.5 mm width level at a 45o angle to prepared wall (conventional bevel design).
Modified Design :
Minimally involved Class I lesions / faults.
Preparation – Less specific, scooped out appearance.
Prepared with round bur – initial depth – 1.5 mm and pulpal floor – not necessarily flat.
Class II Cavity Preparation :
To restore with tooth with Class II composite – Several factors should be emphasized. 1) Extensions of tooth preparations – Decision is made
whether or not an enamel periphery will exist or not. If enamel present – It strengthens the restoration.
2) Assessment of pre operative occlusal relationship of the
tooth to be restored. If any heavy occlusal contacts present Its contraindicated.
3) Preoperative wedging in the gingival embrasure
of the proximal surfaces to be restored should occur.
Two Designs Can Be Made :
-Conventional Design
-Modified Design
Conventional Design :
Used for moderate to very large Class II cavity Design is uniform with flat pulpal floor and axial
depth and preparation walls perpendicular to the occlusal load. No secondary retention features required and instead
cavity is left roughened rather than smooth margins. An initial depth of upto 1.5 mm/0.2 mm inside the DEJ. Facio lingual width as narrow as possible, cuspal
areas preserved as much as possible.
Same as conventional Class II amalgam preparation except for no secondary retention features.
Axial wall depth should be 0.2 mm into DEJ. Gingival wall should be flat with 90o cavosurface margin. No bevel is given on the cavosurface margins. Buccal and lingual walls of proximal box should be
extended into self cleaning areas. If the preparation extends to the root surface, it should have
o 90o cavo surface margin o Axial depth of 0.75 – 1 mm
o No secondary retention form
Modified Class II Tooth Preparation :
1) For Small Initial Restorations :
More conservative design may be used.
Small round / inverted cone diamond used for preparation to scoop on the carious / faulty material.
Scooped appearance appears both on occlusal and proximal portions.
Pulpal and axial depths – dictated only by depth of lesion and are not of uniform depth.
Objectives are conservatively remove the fault, create 90o cavo surface margin/ greater and remove friable tooth structure.
2) Another Modified Design Is Only Tooth Preparation
Indicated only when proximal surface is faulty, with no lesion on occlusal surface.
Cavity is made by directly penetrating the marginal ridge with an axial depth of 0.2 mm into dentin.
Facial, lingual and gingival extensions are dictated by the fault / caries.
No beveling / 2o retention is indicated.
3) Another Modified Design
Facial / lingual slot preparation
Here lesion is present on proximal surface and can gain access either from facial / lingual direction rather than through marginal ridge in a gingival direction.
Preparation extended occlusally, facially and gingivally enough to remove the lesion.
Axial wall depth is 0.2 mm in side DEJ
Occlusal, facial and gingival cavosurface margins are 90 degrees or greater.
Class III Preparations And Cavity Designs :
Definition : Located on the proximal surfaces of anterior teeth. It can be by facial approach/ lingual approach
Indications for Facial Approach include ;
Carious lesions is positioned facially such that facial access would significantly conserve tooth structure.
Teeth are irregularly aligned, making lingual access undesirable.
Extensive caries extend onto the facial surface.
Faulty restoration that was originally placed from facial approach which needs to be replaced.
Indications for Lingual Approach and Its Advantages :
Facial enamel is conserved for enhanced esthetics.
Some unsupported, but not friable, enamel may be left on the facial wall of a Class III or Class IV preparation.
Color matching of the composite is not as critical.
Discoloration / deterioration of the restoration is less visible.
And finally when both facial and lingual surfaces are involved use the approach that provides the best access for instrumentation.
Cavity Designs For Class III Cavity :
• Conventional • Beveled Conventional• Modified Preparation
Conventional Class III Preparation
The primary indication for this type of preparation is for the restoration of root surfaces, so it would be measured to have an entire Class III preparation of the conventional type. So only part of preparation i.e. the portion of the root surface that has no enamel margin, would be prepared like this.
Design of the preparation then would be a combination of a modified or a beveled conventional with a conventionally prepared root surface area.
The preparation wall is same s that for an amalgam preparation i.e. cavosurface margins exhibit 90o cavosurface angle and provide butt joints.
External walls are prepared perpendicular to root surface
and they are entirely dentin and cementum. Walls (Prepared) must have sufficient depth pulpally to provide ;
1. Adequate removal of caries / old restorative material / faults. 2. Placement of grooves if necessary
Pulpal depth should be 0.75 mm into dentin
Walls should be perpendicular to the root surfaceGrooves – retention form is necessary in non enamel,
root surface preparation to both increase the retention of the material in the tooth.
Preparation :
Outline Form : - with No. 1/2 , 1 or 2 round bur outline form, extending the external walls to sound tooth structure while preparing to limited depth of 0.75 mm.
External walls perpendicular to root surface 90o cavosurface angle.
Box like design – considered 1o retention form
Depending on approach – if facially extend the facial wall for access and visibility and if approach is from lingual then lingual wall be extended.
Remaining infected dentin / old restorative material is removed, pulp protected with Ca(OH)2 liner.
Grooves inform of 2o retention form may be used for
more retention and which minimizes the potential (-) ve effects of polymerization shrinkage, thereby giving proper marginal seal. Done by preparing continuous retention groove in the interoral portion of external wall (Depth of Groove) 0.25 mm.
Beveled Conventional Class III Cavity Preparation :
Indications :
1) Primarily for replacing an existing defective restoration.
2) When restoring a large carious lesion where there is need for increased retention.
Characterized by ;
External walls perpendicular to the enamel surface with enamel margin beveled. Axial line angles may / may not be of uniform pulpal depth. Retention is obtained only by acid etching the enamel walls with its bevel, but no retention groove necessary.
Lingual Access : Preparation :
With a clean mirror in place (indirect vision) use a round carbide bur ½. Prepare the out line form extending as minimal as possible, dictated by the cries / old restorative materials.
Axial wall depth is limited to 0.75 mm – 1.25 mm, with the axial wall outwardly convex, following normal external tooth contour.
Axial line angle should be at an initial depth of 0.2 mm into dentin.
Removal of remaining infected dentin / old restorative material removed with excavators / round burs and adequate pulp protection given.
If any 2o retention is necessary, prepare them along gingivo axialline angle with No.1/4 bur 0.25 mm depth directed gingivally and pulpally.
The additional feature in this design is the cavo surface
bevel which increases surface area for etching of enamel rods. Prepared with coarse shaped diamond instrument oriented at 45o
to external tooth surface. Bevel width is 0.25 mm to 0.5 mm.
Facial Access :
Same steps with few exceptions as that for lingual access. Procedure is simplified due to direct access.
Modified Class III Preparation :
One mostly used for class III caries
Designed for small to moderate caries lesions and is designed to be as conservative as possible.
Usually no efforts is made to produce cavity walls that have specific shapes / forms.
Preparation do not routinely extend into dentin, the entire cavity may be in enamel.
Extension of axial walls also is dictated by the extent of fault of carious lesion and usually will not be of uniform in depth.
Weakened / friable enamel is removed while preparing cavosurface margins in a beveled or flared configuration with a round diamond.
Usually no retention groove is indicated because retention
of material in tooth will result from the bond created between the compressive material and etched peripheral enamel.
Thus preparation design appears to be “scooped’ or concave.
Class IV Cavity Preparation :
These Class IV restoration have provided with a conservative treatment to restorative fracture, defective or cariously involved anterior teeth when previous porcelain crown has been the treatment of choice.
But pre operative conditions like, occlusion, shade selection are important in these restorations.
Conventional Class IV Tooth Preparation :
Typical conventional design with 90o cavosurface has minimalclinical Class IV application except in those areas that have margins locate don root surface.
Any portion of Class IV restoration that extends onto the root requires a 90o cavosurface margin and possible groove retention form, regarding less of whether beveled conventional or modified preparation design is used for the portion of the preparation in the crown of tooth.
Beveled Conventional Class IV Preparation
Is indicated for restoring large proximal areas that also include the incisal surface area of an anterior teeth.
Retention of composite restorative material in this design can be obtained by groove or other shaped undercuts, dove tail extensions, threaded pins or a combination of these other than from the etched enamel surface.
Gingival and incisal retentive undercuts may be indicated in large Class IV preparation.
Sometimes an arbitrary dove tail extension onto the lingual surface may enhance strength and retention of restoration.
Although pins are used for retention – sometimes they are discouraged and may cause perforation either into the pulp / external surface.
Do not enhance the strength of restorative material.
Some pins may corrode because of microleakge of restorative material resulting in discoloration of tooth and restoration.
Outline form characteristics by making the walls
perpendicular /parallel to the long axis of tooth so that it provides greater resistance to biting force that couldcause fracture of tooth or restorative material.
Remove all weakened enamel and establish the initial
axial wall depth at 0.5 mm into dentin.
After removing the infected dentin and adequate pulp protection, bevel all the cavosurface margins of all accessible enamel margins. Bevel is prepared at 45o angle to the external tooth surface. Width of bevel is 0.25 – 2 mm depending on the amount of tooth structure missing and the retention perceived necessary.
Addition retention is obtained by either increasing the width of enamel bevel or placing retention undercuts like grooves, cones, dove tails etc.
No retentive undercut is usually needed at the incisal area, where mostly enamel exists.
Modified Class IV Preparation :
Indicated for small / moderate size Class IV lesions/ traumatic defects.
The objective of cavity preparation is to remove as little tooth structure as possible while providing for appropriate retention
and resistance forms.
Usually no groove / core retention form is indicated but retention is obtained primarily from the bonding strength of composite to enamel.
Class V Preparation :
Due to esthetic considerations, composite are used for the restoration of Class V lesions in anterior teeth.
Here shade selection, isolation are important.
Shade – Generally dark in cervical 1/3rd and isolation with rubber dam and 212 retainer.
Conventional Class V Cavity Preparation :
Indicated for that portion of a carious lesion / defect entirely or partially on the facial / lingual root surface of a tooth.
The features of the preparation include
-A 90o cavosurface angle -Uniform depth of axial line angels
Decreased microleakge due to enhanced bond between the composite and the tooth.
Decreased need for groove retention form
When are large carious lesion / faulty restoration extends onto the root surface, the gingival wall is prepared same as conventional preparation with 90o cavosurface margin and the depth being 0.75 mm and only the enamel margins are beveled.
Modified Class V Preparation :
Indicated for small and moderate Class V lesions / defects.
No efforts to be made to prepare butt joints and no groove retention forms incorporated.
Lesions / defect is “scooped out” resulting in a preparation form that may have a diverging wall configuration and an axial surface that usually is not uniform in depth.
Class V modified preparations are ideal for small enamel defects/ small but cavitated lesions that are largely/ entirely in enamel.
These include decalcified and hypoplastic areas located in the cervical /13 of the teeth.
Class V Preparation for Abrasion / Erosion Lesions :
Class V preparation (Modified) also are used to restore abraded or eroded cervical areas.
It only requires – roughening of the internal walls with a diamond instrument
Beveling / flaring all enamel margins
Placing a retention groove in non-enamel areas
If necessary prepare the root surfaces cavo surface margins to approximately 90 degrees and sometimes retention grooves
If any enamel margins are present, they should be prepared using either a beveled conventional / modified preparations.
Preparation :
Instrument :
Tapered fissured carbide bur (No.700, 70/ 271). orNo.1 / No.2 round bur – If access interproximally/ gingivally is limited.
Outline form should result in 90o cavosurface margins. Pulpal depth – 0.75 mm and if any remaining caries should be removed in the finals stage of cavity preparation.
This 0.75 mm of depth provides-Strength of the cavity wall
-Strength of the composite -Placement of retention groove, if necessary
Final Cavity Preparation Consist of
Removing the remaining infected dentin / old restoration material
Pulp protection – Applying Ca(OH)2 timer
Preparation of retention groove if necessary
Beveled Conventional Class V Cavity Preparation :
Indicated For 1) Replacing an existing, defective Class V restoration which
initially had Class V conventional preparation.
2) New large carious lesion
This preparation will exhibit 90o cavosurface margins which are subsequently beveled enamel margins.
Axial depth is 0.2 mm into dentin when retention grooves are not necessary and 0.5 mm into dentin when they are necessary.
Advantages of Beveled Cone : Increased retention due to greater surface area of etched
enamel (afforded by level).
Common Problems – Causes and Solutions :
1. Poor isolation of the operating areaCauses :
No rubber dam/ leaking rubber damInadequate cotton roll isolationCareless techniquePreparation so deep gingivally that it cannot be isolated.
Solutions :
Better techniqueUse of matrix to help isolationUse of non bonded restorative materialRepeat bonding procedures If its contaminated
2. White line / Halo around the enamel margin
Causes :
Traumatic contouring / finishing techniquesInadequate etching and bonding of that areaHigh intensity light curing, resulting in excessive polymerization stresses
Solutions :
Reetch, primer and bond the areaConservatively remove the fault and rerestore Use atraumatic finihign techniquesUse slow start polymerization techniques
3. Voids
Causes
Mixing of self-cured compositesSpaces left between increments during insertion Tacky composite pulling away from preparation during insertion.
Solutions :
More careful techniqueRepair of marginal voids by preparing the area and re restoring.
4. Weak / Missing Proximal Contacts
Causes :
Improperly contoured matrix bandsInadequate wedgingMost of matrix band during composite insertion Using circumferential matrix when restoring one contact.
Solutions :
Properly contour the matrix band. Use proper and firm wedging techniqueUse matrix system that places matrix around only the proximal surface to be restored. Careful insertion techniquesProper placement of matrix band with firm pressure and holding the adjacent tooth.
5) Incorrect Shade
Causes :
Inappropriate operator lighting while selecting the shade. Selecting the shade after the tooth is dried. Shade tab not matching the actual composite shade. Wrong shade selected.
Solutions :
Select the shade before isolating / drying the tooth. Use natural light if possible for shade selectionPreoperative place some of the selected shade on the tooth and cure. Do not shine operating light directly on the area during shade selection. Understand the typical zone of different shades for natural teeth.
6) Poor Retention
Causes :
Inadequate preparation form Contamination of operating areaPoor bonding techniqueIntermingling of bonding systems
Solutions :
Prepare tooth with appropriate bevels and 2o retention features. Keep the area isolated while bonding. Following manufacturers directions properlyDo not intermingle bonding materials
7) Contouring and Finishing Problems
Causes :
Injuring the adjacent unprepared tooth structureOver contouring / under contouring the restoration Ditching the cementumCreating inadequate anatomic form Dealing with difficult to see margins
Solutions :
Careful use of rotary instrumentsHave proper matrix system with appropriate axial and time angel contoursView the restoration from all angels as it is contouredUse properly shaped contouring instruments for the area being contoured.
Failures In Composite Restorations :
Composite restorations are very technique sensitive – so utmost care is necessary before, during and after manipulation.
The visible modes of failures1) Discoloration- especially at margins2) Marginal fracture3) Recurrent caries4) Post operative sensitivity5) Cross fracture of restoration6) Lack of maintaining contact7) Accumulation of plaque around the restoration
Following Features : Which lead to failures
1) Incomplete excavation of caries : - Incomplete removal of caries – Hinders bonding mechanism. 2) Incomplete etching / failure to remove residual acid from enamel tags. Proper concentration of acid along with proper etching
time is mandatory to achieve resin tags. -Repeated touching after etching, blowing with compressed air under pressure and/sweeping the etched surface with cotton can lead to failure (no proper resin tags).
3) Double / non uniform coat of bonding agentBonding agent applied should be uniform and gently all around the cavity walls. Double layer / non uniform coat – may hinder the union of material with bonding agent.
4) Lack of Isolation Important tip : If improper leads to failure in bonding of restoration.
5) Touch of composite and with fingers
6) Bulk placement of composites Avoid bulk placement and always incremental placement
is done. If bulk placement done – leads to improper polymerization.
Marginal gap, post operative sensitivity and 2o caries.
Composite Laminates And Veneers :
Veneer : Layer of tooth colored material that is applied to restore localized / generalized defects, intrinsic discoloration.
- Typically veneers made of o Chair side compositeo Processed compositeso Porcelaino Pressed ceramic material
- Types of veneerso Partial veneers – Localized defecto Full veneers – Generalized defects
Direct techniqueIndirect technique
Direct Partial Veneers : Small localized intrinsic discolorations and defects. Finished in one appointmentSteps
o Cleaningo Shade selectiono Isolation
Preparation :
Outline form dictated by the defect / lesion / discoloration Initial depth 0.5 – 0.75 mm
If still discoloration present Left it and can be measured by opaque etching and rinsing.
Bonding.
Restoration :
- If entire defect / stain is removed then restored with microfilled composite
- If still lightly stained area / white spot remains intrinsically less translucent composite is used.
Finishing and polishing.
Direct Full Veneers :
Extrusive enamel hypoplasia involving all of maxillary anterior teeth. Tetracycline stained teethProcedure completed in one step saves patients visitBut takes long chair side time – tiring.
Preparation :
Teeth cleaned, isolated and shade selected. Preparation varies – depends whether it envelopes the marginal ridges and incisal edges. Outline depends on the extent of lesion in incisal and gingival direction Ideally – it should be 0.5 mm supra gingivally Tooth prepared – Routine fissure lines – depth of 0.5 -0.75 mm
In case deeply stained – further cutting depth – 1.0 mm – 1.25 mm – to accommodate the opaque to mask the dark colour.
Some authors suggest use of cross cut lines to preparation in order to achieve under cuts and larger surface area for etching – by which retention is increased.
A heavy chamfer at the gingival wall is given to get a definite preparation margin.
Etching, rinsing, drying and bonding is done. If opaque is necessary – its placed in thin layers and cured. While restoring the tooth – bleeding of colour from one shade
to another is very important. First apply – gingival shade of composite with a hand instrument, starting with enough material to cover gingival 3rd of tooth.
Gingival shade of composite feathered out at the middle 3rd, smoothened and cured.
Next blend incisal shade over the middle third and onto the incisal area to obtain good contour and colour.
In the incisal edge – special translucent shades of composites are placed and restored to proper contour and cured.
Finally contouring – both cervico incisally and mesiodistally checked with from mesial and distal and incisal direction.
In case only one tooth is laminated – checked with adjacent teeth. If more teeth are laminated – overall patients smile, esthetics
and requirements – should be kept in mind.
Indirect Veneers :
Processed outside the oral cavity to achieve better colour matching and proper contouring. Two step procedure and less fatigue to the patient. Made of
o Processed compositeo Fled spattic porcelain – superior strength and durability and esthetics so better preferredo Cost pressed ceramic
Composite veneer : Cured under intense light, that, vaccum, pressure or combination of these – produces improved physical and mechanical props compared to chair side veneers.
Preparation :
Similar to that of direct full veneer except for incisal enveloping cannot be done.
A window preparation design is used mostly because of limited bond strength of composite veneers. Done with tapered round end diamond instrument to a depth of 0.5 – 0.75 mid facially and diminishing to a depth of 0.3 – 0.5 mm along the gingival margin.
There should not be any undercuts interproximally or into proximal contacts.
An incisal lapping design is sued if teeth require lengthening / if defects warrants involvement of incisal edge.
Temporary :
No temporary restoration placed – if restricted to enamel, but if in dentin – a coat of bonding agent is placed.
Impression :
Teeth isolated, gingival restoration done with cord and electrometric impression taken.
Cast is made and veneer is fabricated and contoured appropriately.
Fabricated in increments with blending of shades and curing each increment for 20 seconds and final curing of 40 seconds.
Some authors advocate placing of veneer in boiling water for 20 minutes for better curing and subsequently the strength.
Fixing :
Prepared tooth surface cleaned and isolated with retraction cords and cotton rolls.
Enamel surface etched, rinsed and dried bonding agent is applied.
Tooth surface of veneer is also extent with weak acid like HF acid.
A selected shade of light cured resin bonding medium added to tooth side of veneer and also to the surface of tooth.
Veneer placed carefully and vibrated lightly into place with blunt instrument and then cured for 40-60 seconds from facial and lingual directions.
Once it is placed only minor amount of finishing is done.
Composite Inlays :
Definition : Defined as restoration which is cemented into dental cavity as a solid mass that has been fabricated from composite resin with a four established either by direct / indirect procedure.
Indications :
1) Regular patients requiring tooth colorued resins.
2) Moderate – large sized lesion for sufficient tooth tissue for bonding
3) No evidence of excessive tooth wear
4) Restoration not overloaded occlusally
5) Better control over contacts and contour is desired.
Contra Indications :
1) Patients with no good oral hygiene
2) Teeth with excessive wear
3) Teeth with heavy occlusal forces
4) Teeth in which deep gingival margins
5) Teeth where the moisture control is difficult to achieve
Advantages :
1. Control of polymerization shrinkage
2. Enhanced physical properties a)Due to proper curing – improved visco elastic stability, decreased internal flow, and increased resistance to occlusal forcesb)Better mechanical props – compressive strength, diametrile tensile strength, hardness. c)Due to secondary curing – better props of wear and color stability.
3. Contacts and contours better created
4. Less technique sensitive
5. Saves patients and doctors time
Disadvantages :
1) Requires 2 appointments
2) Cost is increase
3) Temporary restoration is required
4) Preparation of cavity may necessitate removal of sound tooth structure
5) Success of restoration depends largely upon bond between inlay and tooth.
Classification : I. Method of construction
1) Direct technique2) Indirect technique
II. Method of curing 1) Superficial inlays2) Conventional cured inlays3) Secondary cured inlays
III. Material of composite inlay 1) SR Isosit inlay system2) Collective brilliant3) Kulzer inlay4) Visio Gem5) Art glass6) Bell glass HP
IV. Type of Composite1) Microfilled composite Eg. SR Lsosit
2) Fine hybrid composite Eg. Coltene brilliant3) Coarse hybrid Eg. Kulzer inlay
