VENEERS
CONTENTS
INTRODUCTION HISTORICAL ASPECT DEFINITION CLASSIFICATION INDICATIONS CONTRAINDICATIONS MATERIALS AND TECHNIQUES PROCESSED COMPOSITES ETCHED PORCELAINS CASTABLE CERAMICS VENEERS FOR METAL RESTORATION REPAIR OF VENEERS ON TOOTH STRUCTURE IN METAL RESTORATION CONCLUSION
INTRODUCTION One of the greatest assets a person can have is a smile that shows beautiful natural teeth.
When teeth are discoloured, malformed or
crooked, there are often conscious efforts to avoid smiling or causes a hand to cover the mouth or manipulation of the lips in an unnatural manner to make up for the defect.
Children are especially sensitive about unattractive teeth because of cruel remarks made by other children. Correction of these types of dental problems can produce dramatic changes in appearance, which often results in improved confidence, personality and social life.
The restoration of a smile is one of the most appreciated and gratifying services a dentist can render. The veneer is a conservative alternative to full coverage for improving the appearance of an anterior tooth. Veneers have evolved over the last several decades to become one of esthetic dentistry’s most popular restorations.
DEFENITION A veneer is a layer of tooth coloured material that is applied to a tooth for esthetically restoring localized or generalized defects or intrinsic discolouration.
CLASSIFICATION Dental veneers can be classified as follows: 1. Directly fabricated composite resin veneers. a. Direct partial veneers b. Direct full veneers 2. Indirectly fabricated veneers a. Etched porcelain veneers b. Processed composite veneers c. Castable ceramic veneers 3. Veneers for metal restorations.
INDICATIONS 1. Discolouration: Tetracycline staining, devitalization and fluorosis, teeth darkened with age can benefit by the process. 2. Enamel defects: Different types of enamel hypoplasia and malformations can be masked. 3. Diastema: Gaps and other multiple unsightly spaces can be closed. 4. Malpositioned teeth: Developing the esthetic illusion of straight teeth where teeth are actually rotated or malpositioned can be accomplished for patients who have relatively sound teeth but do not wish to undergo orthodontics.
5. Malocclusion: The configuration of lingual surface of anterior teeth can be changed to develop increased guidance or centric holding areas in malocclusion or periodontally compromised teeth. 6. Poor restorations: Teeth with numerous shallow, unaesthetic restorations on labial surfaces can be dramatically restored. 7. Aging: For discoloured teeth or attired teeth due to aging, improvement can be done by bleaching or bleaching with subsequent veneering. 8. Wear patterns: Porcelain laminates are also useful in those cases that exhibit slowly progressive wear patterns. If sufficient enamel remains and the desired increased in length is not excessive, porcelain veneers can be bonded to remaining tooth structure to change shape, color or function. 9. Agenesis of lateral incisor: When lateral incisors are missing, veneer can be used to develop better coronal form in the canine, thus simulating a lateral incisor. These may have to be combined with veneers on the central incisor to develop a more ideal ratio in the relative proportion of the teeth, because the canine is invisible too wide when positioned adjacent to the central incisor.
INDICATIONS 1. Stained / defective restoration 2. Diastema 3. Fractures 4. Attrition 5. Adolescent teeth (Large pulps) 6. Discolouration 7. Malformation 8. Malpositions (slight) 9. Root exposure 10.Erosion/abrasion
CONTRAINDICATIONS 1) Available Enamel: There should be enamel around the whole periphery of the laminate, not only for adhesion but, more importantly, to seal the veneer to the tooth surface. There should be sufficient enamel for bonding. Because bonding to dentin is generally less retentive than enamel. If tooth or teeth are composed predominantly of dentin and cementum, crowning may well be treatment of choice. 2) Ability to etch enamel: deciduous teeth and teeth that have been excessively fluoridated may not etch effectively. They may require special measures to be successful with porcelain laminator.
3) Oral habits: Patients with certain tooth habit patterns, such as bruxism, or tooth to foreign objects habits may not be ideal candidates of veneers. 4) High caries rate: in patients with high caries rate laminate veneers are contraindicated.
HISTORY: In 1930’s Dr. Charles Pincus used this porcelain veneers to improve the esthetics of movie stars teeth. Unfortunately he had to use denture adhesive to hold the veneers in place. In mid 1970’s and early 1980’s composite resin laminate veneers, wit or without a facing evolved.
At first, composite resin was added directly to facial surface of a tooth to restore fracture, discoloured or malformed incisors in a procedure known as bonding.
The early composites presented with problems like monochromatic appearance, with staining and a loss of lusture over time.
Early
composite veneers did not need any tooth preparation and a bulk of material was needed for pleasing appearance. contoured restoration lead to gingival inflammation.
Unfortunately over
Second evolution of veneers involved development of preformed veneers that were joined to etched tooth structure. Constructing a veneer and bonding it to etched tooth structure is referred to as laminating disadvantages of this was – color instability, surface staining, low abrasion resistance, poor bond. These problems led to diminished use of acrylic resins or composite resins. Glazed porcelain is nonporous, resists abrasion, and possesses esthetic stability, well tolerated by gingiva. In early 1980’s method of bonding porcelain to acid etched enamel was developed. Etching porcelain using hydrofluoric acid (9-10%).
The application of silane coupling agent also increases bond strength, the silane-coupling agent initiates a weak chemical bond between the SiO2 of porcelain and bis-GMA polymer of composite resin. The improved strength of etched porcelain permits an expanded use of veneers and popularity has increased over the following years.
ADVANTAGES OF DIRECT COMPOSITE VENEERS 1) Only one appointment. 2) The dentist directly controls form and colour. 3) Cost to the patient is reduced. 4) Composite veneers are repairable.
ADVANTAGES OF INDIRECT PORCELAIN TECHNIQUE 1) The dentist may use the time saving and esthetic skill of a ceramist. 2) Multiple units can be placed with less chair time. 3) Porcelain is the optimum material for color stability, esthetics, wear resistance and tissue compatibility.
PROCESSED MATERIALS OTHER THAN PORCELAIN Resins and composites processed at elevated pressures and/or temperatures, castable hydroxyapatite and injectable ceramics (Dicor, Convertone). Indirect resins have better physical properties than direct light cure composites but decreased bond strength. Cast ceramics have advantages of waxing stage, excellent translucency, and possible decrease plaque adherence.
PORCELAIN LAMINATES Are thin facings of ceramic porcelain affixed directly to teeth using a composite resin as bonding cement. Unlike composite veneers, which are directly fabricated on the patient’s teeth, porcelain veneers are constructed on refractory dies made from elastomeric impressions,
The inner surface of the porcelain veneer is treated with hydrofluoric acid, etching it frosty white and increased interface area wit
retentive irregularities for mechanical bond to composites.
Albers
indicated that a tooth to be bonded should have atleast 50% of its surface composed of etch able enamel. Preferably, the peripheral margins are of enamel to conform to the “one millimeter circumferential principle� for long-term marginal integrity of the enamel resin bond.
TWO TYPES OF VENEERS 1) Partial veneers: Indicated for the restoration of localized defects or areas of intrinsic discoluration. 2) Full veneers: Indicated for the restoration of generalized defects or areas of intrinsic staining involving the majority of the facial surface of the tooth.
Important factors like patients age, occlusion, tissue health, position and alignment of teeth and oral hygiene.
ADVANTAGES OF INDIRECT VENEERS 1. Indirectly fabricated veneers are much less technique sensitive to operator ability. Considerable artistic expertise and attention to detail are required to consistently achieve esthetic and physiologically sound direct veneers. Indirect veneers are made by a lab technician and are typically more esthetic.
2. By multiple teeth are to be veneered, indirect veneers usually an be placed much more expeditiously. 3. Indirect veneers will last much longer than direct veneers, especially of porcelain or cast ceramic.
To achieve esthetic and physiologically sound results an interenamel preparation is almost always indicated.
The only exception is in cases where the facial aspect of tooth is significantly under contoured due to severe abrasion or erosion. In these cases, more roughening of the involved enamel and defining of the peripheral margins are indicated.
Intra-enamel preparation (or the roughening of the surface in under contoured areas) before placing veneer is strongly recommended for the following reasons. 1) To provide for opaque, tinting, bonding and/or veneering materials for maximal esthetics without over contouring. 2) To remove the outer fluoride rich layer of enamel which may be more resistant to acid etching. 3) To create a rough surface for improved bonding. 4) To establish a definite finish line.
MATERILAS AND TECHNIQUES It is necessary that a complete examination, diagnosis not treatment plan be finalized before the patient is scheduled for operative appointments. At the beginning of the each appointment also carefully examine the operating site and assess the occlusion, particularly of the tooth scheduled for treatment.
LOCAL ANESTHESIA Generally veneering of teeth does not require local anesthesia as most of preparation are in the enamel. If the defect is extending into the dentin then use of local anesthesia is advised. It also contributes to a pleasant and uninterrupted operation and usually results in a marked reduction in salivation.
PREPARATION OF OPERATING SITE Clean the operating site to remove calculus, plaque, pellicle and superficial stains.
Prophylactic pastes containing fluording agents,
glycerine, or fluorides act as contaminants and should be avoided to prevent a possible conflict with the acid etch technique. Slurry of pumice is recommended for this procedure.
TECHNIQUES 1) Direct Veneer Technique: a. Direct partial veneers b. Direct full veneers
DIRECT PARTIAL VENEERS Small localized intrinsic discolouration or defects that are surrounded by healthy enamel are ideally treated with direct partial veneers. The outline form is dictated solely by the extent of the defect and should include all of the discoloured area. Use a coarse elliptical or round diamond instrument with air water coolant to prepare the cavity to depth of 0.5 to 0.75 mm.
Usually it is not necessary to remove all of the discoloured enamel in a pulpal direction.
However the preparation must be extended
peripherally to sound, unaffected enamel. For the masking of dark stains opaquing agents (e.g. Nuva Seal P.A. sealant in which is dispersed an opacifying agent, titanium-dioxide) is used if necessary.
The entire
defect or stain is removed, and then a microfill composite is recommended for restoring the cavity.
Most composites filled primarily with radiopaque fillers, such as barium glass, in addition to being radiopaque are also more optically opaque with intrinsic marking qualities. Use of these types of composites for the restoration of cavities with light residual stains is most effective and conserves tooth structure.
SHADE SELECTION Special attention should be given to matching the color of the natural tooth. Determine the shade of tooth before the teeth are subjected to any prolonged drying, because dehydrated teeth become lighter in shade as a result of a decrease in translucency. Normally color of teeth varies from degrees of gray, yellow, orange tints. The color also varies with translucency, thickness and distribution of enamel and dentin as well as age of the patient.
Many manufactures provide shade guide for their specific materials, which usually are not interchangeable with materials from other manufactures. Most composite materials are available in enamel and dentin as well as translucent and opaque shades. Good lighting, either natural or artificial is necessary when the color selection is done.
Natural light is preferred for selection of shades.
If dental
operating light is used, it should be moved away to decrease the intensity, thus allowing the effect of shades to be seen.
In choosing the appropriate shade, hold the entire shade guide near the teeth to determine general color. Then select and hold a specific shade tab alongside the area of a tooth to be restored. The shade tab should be partially covered with the patients lip or operators thumb to create the natural effects of shades. The cervical area is usually darker than the incisal area.
ISOLATING THE OPERATING SITE Isolation of tooth colored restoration can be accomplished with (1) Rubber dam, or (2) Cotton rolls and retraction cords. Contamination of etched enamel by saliva results in a decreased bond, contamination of composite, results in degradation of physical properties.
ADVANTAGES OF DIRECT VENEER Can be done in one appointment. It is less expensive. Can also be used in cases where patient doesn’t have much time for repeated appointments.
DISADVANTAGES It is very time consuming. Labour intensive.
DIRECT FULL VENEERS Indicated in extensive enamel hypoplasia involving anterior teeth. Also indicated in distema closure. Several important factors like patients age, occlusion, tissue health, position and adjustment of teeth and oral hygiene must be evaluated prior to processing full veneers. If full veneers are done, care must be taken to provide proper physiological contours, particularly in the gingival area, to favour good gingival health. Over contoured or properly contoured veneers leads to severe gingival irritation. There is controversy involving the location of the gingival margin of veneer. Should it terminate short of the free gingival crest and the answer depends on individual situation. If defect of discolouration does not extend subgingivally then the margin of the veneer should not be extended subgingivally. The only logical reason for extending the margin subgingivally is if the area if the area is carious or defective, warranting restoration, or if it involves significantly.
ď ś Dark discoloration that prevents a difficult esthetic problem. No restorative material is as good as normal tooth structure and the gingival tissue is never as healthy when it is in contact with artificial material.
Two basic preparation designs exist for full veneers. 1) A window preparation 2) An incisal lapping preparation.
A WINDOW PREPARATION This is recommended for most direct and indirect composite veneers. This intra-enamel design preserves the functional lingual and incisal surfaces of the maxillary anterior teeth, protecting the veneers from significant occlusal stress.
A window preparation design also is recommended for indirectly fabricated porcelain veneers if the patient exhibits significant occlusal function and evidenced by wear facets on lingual and incisal surfaces. By using a window preparation the functional surfaces are better preserved in enamel. The design decreases the potential for accelerated wear of the opposing teeth that could result if the functional path involves porcelain on lingual and incisal surfaces.
AN INCISAL LAPPING PREPARATION Indicates when the tooth being veneered needs lengthening or when an incisal defect warrants restoration. Additionally, incisal-lapping design is
frequently used with porcelain veneers, because it not only
facilitates accurate seating of veneers upon cementation, but allows for improved esthetics along the incisal edge.
PROCEDURE This procedure can be indicated when there is enamel hypoplasia involving all maxillary anterior teeth, when diastema is present in between the teeth. After teeth are cleaned and a shade selection done, isolate the area with cotton rolls and retraction cords. Prepare the cavity preparation on both central incisor with a coarse, rounded end diamond instrument.
The window preparation is typically made to a depth roughly equivalent to half the thickness of facial enamel ranging from approximately 0.5 to 0.75 mm mid facially and tapering down to a depth of about 0.2 to 0.5 mm along the gingival margin depending on the thickness of enamel.
A heavy chamfer at the level of the gingival crest provides a definite cavity margin for subsequent finishing procedures. Margins are not extended subgingivally, these areas not defective.
The preparation for a direct veneer normally is terminated just facial to the proximal contact except in areas of diastema. To correct the diastema, preparations are extended from the facial onto the mesial surfaces, terminating at the mesio-lingual line angles.
The teeth should be restored one at a time. After etching, rinsing, drying, procedures apply and polymerize the resin-bonding agent. Place composite on tooth in increments, especially along the gingival margin, to reduce the effects to allow some freedom in contouring.
Sometimes, if the teeth have tetracycline stains they are much more difficult to veneer especially if dark banding occurs in the gingival third of the tooth, for much cases the veneer margins are placed sub-gingivally.
After cleansing and shade determination, mark the gingival tissue level prior to tooth isolation on the facial surfaces of the teeth to be veneered by preparing a shallow groove with a Âź round carbide bur.
Because the cervical areas are badly discoloured and the gingival tissue covers much of the clinical crown isolation and tissue retraction is accomplished with heavy rubber dam and no. 12 cervical retainer only one tooth is prepared and restored at a time.
The outline form includes all of the facial surfaces, extending approximately 0.1 to 1 mm cervical to mark indicating the gingival tissue level, and into the facial embrasures but not including contact areas. As much well supported enamel as possible should always remain at the incisal ridge to preserve strength, wear resistance and functional occlusion or enamel.
Prepare the tooth i.e., concave, rounded and diamond instrument by removing approximately half of the enamel thickness (0.3 mm in the gingival region to 0.7 mm in the mid facial and incisal regions). After etching, rinsing and drying, apply thin layer of bonding agent and cure. Opaquing layer can be applied after this procedure. Apply a gingival shade of composite to cover gingival third of the tooth. Blend the incisal shade over the middle third and onto the incisal area for proper contour or colour.
DIRECT VENEER THECHNIQUE Many dentists find that the preparation, insertion and finishing of several direct veneers at one time is too difficult, fatiguing and time consuming. Some patients become uncomfortable and restless during long appointments. The veneer shades and contour can be better controlled when made outside the mouth on the cast. For these reasons indirect veneers are preferred.
In direct veneers include those made by: 1. Processed composite. 2. Etched porcelains (Feldspathic) 3. Castable ceramics. ď ś Because of superior strength, durability and esthetics, feldspathic porcelain is by far the most popular material for in-direct veneering. ď ś Cast ceramic veneers offer comparable qualities but require exacting lab support and the superb marginal fit of these veneers can minimize or eliminate this disadvantage. ď ś Indirect veneers are attached to enamel by acid etching and bonding with either a self-cured, light or dual cured resin bonding material.
ETCHED PORCELAIN VENEERS Most frequently used is etched porcelain (feldspathic) veneer. Porcelain veneers etched with 7.5% hydrofluoric acid (7-10 minutes). Etched porcelain veneer are highly aesthetic, have high bond with etched enamel via resin bonding medium, stain resistant, periodontally compatible. The incidence of cohesive fracture for etched porcelain veneer is less than composite veneer. ADVANTAGES 1) Colour-better natural look with good stability 2) Bond strength 3) Periodontal health 4) Resistance to abrasion 5) Strength 6) Resistance to fluid absorption 7) Esthetics. DISADVANTAGES 1) Time 2) Repair-not easily once luted to enamel 3) Technique sensitive 4) Colour 5) Tooth preparation 6) Cast 7) Fragility.
PROCEDURE Porcelain laminate veneers require preparation of tooth. It is minimal and within enamel (0.5 mm). Ideally finish line should be a slight chamfer placed within enamel at level of gingival crest or slightly subgingival.
STEPS a) Labial/facial reduction. b) Interproximal extension. c) Incisal or occlusal modification. d) Lingual reduction.
LABIAL/FACIAL REDUCTION 1. Extended reduction is 0.3 mm, reduction for the incisal half of labial surface and incisal edge is 0.5 mm. 2. LVS depth diamond cutter is used.
This stone creates horizontal
striations or depth cut grooves on labial surface. 3. This diamond comes in 2 sizes LVS No.1 (0.3mm), LUS NO.2 (0.5mm). 4. Select appropriate diamond cuter 5. Gently draw diamond across the labial surface of the tooth in a depth cuts as horizontal grooves, leaving a raised strip of enamel between.
6. Then remaining enamel must be reduced to these cuts. 7. Bulk of reduction should be done wit with a coarse round end tapered diamond bur. This completes gingival portion of facial reduction while the tip of diamond establishes a slight chamfer finish line at level of gingiva. (Finish line should be at right angle to the gingival margin).
INTERPROXIMAL REDUCTION 1. Proximal reduction is an extension of facial reduction. 2. Using round end tapered diamond, continue reduction into proximal area. 3. As the bur is a carried interproximal embrasure, it is easy to lift instrument slightly towards the incisal, creating a step at gingival. This step should be eliminated since this can create a dark shadow. 4. To correct an uneven finish line, make sure the diamond is parallel wit long axis of tooth. These will guarantee that the gingival extension in the interproximal area is equal to reduction of proximal surface at incisal. The proximal reduction should extend into contact area but it should stop just short of breaking the contact when multiple adjacent teeth are prepared for veneers. The contacts should be opened to facilitate separation of the dies without damaging the interproximal finish line.
INCISAL REDUCTION 1. The fabrication of a porcelain veneer capping the incisal edge makes placement of restoration that much easier by virtue of having a definitive step during seating. 2. The reduction should be at least 1 mm if it is desired to restore original length. 3. Porcelain is stronger in compression than tension.
Wrapping the
porcelain over the incisal edge and terminating it on the lingual surface places veneer in compression during function. A slight incisal overlap provides a vertical stop that aids in proper seating of veneer. 4. Multiple wheel diamond bur makes 0.5 mm depth orientation grooves in incisal edge. Remove tooth structure between grooves with round end tapered diamond.
LINGUAL REDUCTION 1. Create the lingual finish line with the round end tapered diamond. Hold instrument parallel to lingual surface, with its end forming slight chamfer 0.5 mm deep. 2. Finish line should be =1/4th the way down the lingual surface, 1.0 mm from centric contacts and connecting the tow proximal finish lines. 3. Increase strength, increase thickness of porcelain.
IMPRESSING MAKING First retract with cord or cotton impregnated with astringent like aluminum sulfate.
Keep coard for 5 minutes.
Important material –
elastomeric-light and heavy.
PROCESSED COMPOSITE VENEERS In recent years, lab processed composites resins have been developed as indirect veneer material suing light, heat, vacuum, microfilled resin materials can be processed with better physical and mechanical properties. They are technique sensitive, operators skill.
ADVANTAGE Superior shading capabilities and control of facial contours, because of microfiled resin, can be polished to a lustrous finish.
DISADVANTAGES Limited bond strength.
Al newly developed processed composite of the hybrid type, filled with barium glass and colloidal slice, offers increased bond strength. Because it contains barium glass, a soft radiopaque filler, it can be sandblasted and etched in the lab with a mild concentration (9% to 10%)
of hydrofluoric acid to produce numerous microscopic undercuts (etched composites). This can help in bonding with enamel.
Processed composite can be placed easily, finished and polished also replaced and repaired easily. Therefore mostly placed in children and adolescents in interior restoration until teeth have erupted and achieved full crown length. Etched composite are indicated for patients who exhibit wear of interior teeth due to occlusal steers. A window preparation design is recommended due to limited bond strength. With bond end tapered designs at depth of 0.5 m to 0.75 mm then impressions are made.
A light cured resin bonding agent is used for bonding. Etch, rinse and dry the tooth, this layer of resin bonding agent is applied to etched enamel, lightly blown with air but not cured until placement of veneers. Premature curing may preclude full seating of veneers. Veneers are carefully placed on tooth and lightly jiggled, remove excess bonding medium, cur for 40 to 60 seconds. Then finishing and flossing is done.
CASTABLE CERAMIC VENEERS 1. Castable ceramic-Dicor. 2. Unlike etched porcelain veneers, which are fabricated by stacking and fixing feldspathic porcelain, castable ceramics veneers are cast using lost wax technique. 3. The material is grayish in colour and very translucent. 4. Low fusing feldspathic shading porcelains fired onto surface of veneer provides final coloration. 5. Procedures are same as etched porcelain veneers. Except that margins of castable ceramic veneers cannot be contoured and finished with rotary instrumentation (it will lead to loss of coloration).
ADVANTAGES ď ś It has excellent marginal fit.
VENEERS FOR METAL RESTORATIONS 1. Esthetic inserts (partial or full veneers) of a tooth coloured material can be placed on facial surface of a tooth previously restored with a metal restoration. 2. For new castings, plans are made at time of cavity preparation and during lab development of wax pattern to incorporate a veneers into the cast restoration.
3. After such a casting has been cemented, the veneer can be inserted as described later, except that the portion of mechanical retention of veneer into casting is provided in wax pattern stage.
VENEERS FOR EXISTING METAL RESTORATIONS 1. Occasionally the facial portion of an existing metal restoration (amalgam or gold) is judged to be distracting. 2. Radiograph is required, to determine if restoration is sound. 3. Size of offensive area determines extent of preparation. 4. Anesthesia is not required because most of preparation is in metal or enamel. 5. Clean areas with pumice, select shade, isolated site with cotton rolls. 6. When offensive metal extends subgingivally, the level of gingival tissue is marked on restoration with a sharp explorer and retraction cord is placed in gingival crevice (sometimes rubber dam). 7. A NO.2 carbide bur rotating at high speed with an air water spray is used to remove metal, starting at a point midway between gingival and occlusal margins. 8. Preparation is make perpendicular to surface approximately 1 mm deep at minimum leaving a butt joint at cavosurfaces margins.
9. All of metal along facial enamel is removed and preparation is extended into facial and occlusal embrasures just enough for metal to hide the metal. 10.The contact area on the proximal or occlusal surfaces must not be included in the preparation. 11.To complete outline form, preparation is extended gingivally approximately 1 mm past the mark indicating clinical level of gingival tissue. 12.Mechanical retention is placed in gingival area with a No.1/4 carbide bur 0.25 mm deep along the gingivoaxial and linguoaxial angels. 13.Retention and esthetics are enhanced by beveling enamel cavosurfaces margin 0.5 mm wide wit a concise, flame shaped diamond instrument oriented at 45 degrees to external tooth surface. 14.After etching rinsing and drying, cavity preparation is completed. New adhesive resin liners containing a chemical called 4-META capable of bonding composite to metal may be used. 15.Composite materials inserted and finished in usual manner.
REPAIR OF VENEERS Failure may be because of breakage, discoloration or wear. Not necessary to remove the whole old restoration, light cured composite is used. Veneers on tooth structure:
1. Small chipped areas on veneers can be corrected by recontouring and polishing. 2. For direct composite veneers should be done with same material used before. 3. After cleaning the area and selecting the shade, roughen the damaged surface of veneer and/or tooth with concise, round end diamond instrument to form a chamfered cavosurfaces margin. Or mechanical locks can be placed in material with small round bur, etch, rinse, dry, bonding agent, cure add composite cure finish.
INDIRECT PROCESSED COMPOSITES, IN THE SAME MANNER 1. For porcelain veneers, a mild hydrofluoric (10%) acid preparation suitable for internal sue must be used to etch fracture porcelain apply rubber dam for gingival protection frosted appearance on porcelain apply silicone coupling agent to etched porcelain before boding agent, then add composite and finish.
If large replace entire porcelain
veneer.
FAULTY VENEERS IN METAL RESTORATION 1. Clean teeth with pumice, select shade, isolate, retract. 2. Remove old restoration wit carbide metal cutting bur. 3. Place retention with a No.33 ½ carbide bur=0.25 mm deep.
4. Polyester strips between teeth proximal surfaces. 5. Clean metal with acid. 6. Apply 4-META place directly in prepared surface apply composite. 7. Evaluation of width of teeth achieved by boley gauge or other caliper. Add composite and finish.
CONCLUSION There is a definite need for an esthetically acceptable conservative treatment to correct the disfiguring appearance of malformed and discoloured teeth. This type of dental disturbance can introduce a grave psychologic effect on the patient. With the use of a specially shaded resin material, a thin plastic veneer and an acid etched technique and also other laminate veneers like porcelain and ceramic veneers, an esthetic and functional restoration can be produced that will give the dentist and the patient consistently acceptable clinical results.
The greatest advantage of this technique is it gives maximum esthetic effects and requires minimum or no tooth preparation.