Porcelain laminates/ orthodontic continuing education

PORCELAIN LAMINATES

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

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Contents

Introduction Tooth preparation Laboratory procedures Placement of veenersConclusion References


INTRODUCTION

A captivating smile showing an even row of natural gleaming white teeth is a major factor in achieving that elusive dominant characteristic known as personality. Dr.charles pincus in the early 1930 developed thin facing made of air fired porcelain which were temporally held in place with adhesive denture powder and created the Hollywood smile for actors,which was an integral part of image personality and opinion

Since then the art of veneering teeth has progressed over 30 yrs to current generation of concepts and materials www.indiandentalacademy.com


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Types of Veneers

Directly fabricated veneers

Indirectly fabricated veneers


Porcelain Laminates

They can be considered to be very much the state of art in cosmetic dentistry. They are wafer thin shells of porcelain like custom made artificial fingernails


Advantages

Color Bond strengthResistance to abrasion Periodontal health Inherent porcelain strengthResistance to fluid absorptionEsthetics


Disadvantages

TimeRepairTechnique sensitiveFragilityCost


Indications

DiscolorationEnamel defectsDiastema Malpositioned teethMalocclusionPoor restorationsAgeingWear patternsAgenesis of lateral incisor






Contraindications

Available enamel Ability to etch enamel Oral habitsPeriodontally compromised

teeth


Tooth Preparation

There are different schools of thought for tooth preparation for porcelain laminates some clinicians are of the school of thought that little or no tooth reduction is required while the opposite end of spectrum advocate a full deep chamfer preparation

If it is possible to place veneers without tooth preparation and still develop a good esthetic form, no subsequent periodontal changes then it is obviously the ideal if not some form of enamel reduction becomes essential


Biological and technical factors for tooth preparation

EstheticsRelative tooth positionMasking of tetracycline stainsMarginal placement Age Potential for periodontal changes


Rationale for Enamel Preparation

To provide for an adequate dimension of available space for porcelain material

To remove convexities and provide for a path of insertion in those situations where either the incisal or interproximal areas are to be included in the veneers

To provide space for adequate opaquing where necessary and for composite resin luting agent www.indiandentalacademy.com

To provide definite seal to help position the laminate during placement

To prepare receptive enamel for etching and bonding the laminate

To facilitate sulcular margin placement in severally discolored teeth


Enamel Reduction

Labial reduction Inter proximal extensionSulcular extensionIncisal or occlusal modificationLingual reduction


Labial Reduction

The preparation should remain within the enamel wherever possible and most certainly at all the peripheral marginal areas to ensure an adequate seal to enamel

A general rule may well be to ensure that over 50 % of preparation is on enamel

In general 0.3 to 0.6 mm or about half thickness of available enamel


Depth Guide

Is one of the method to gauge the amount of enamel removed

The LVS depth cutter diamond will create horizontal striations or depth cut grooves on the labial aspect of tooth

An alternative method for gauging the amount of enamel reduction is use of a no 1 round bur


The problem with this approach is that these depth cuts can vary depending on the angle the bur is held at and the amount of time is considerably greater


Reduction of remaining enamel

Following the creation of depth cut or striations the remaining enamel must be reduced to the depth of these initial cuts

Labial reduction should encompass 2 aspects

1) The bulk of reduction should be done with a coarse diamond to get added retention and better refraction of light

2) The marginal area it is desirable to use a fine grid diamond that will create a definitive, smooth finish line to enhance the peripheral seal








Interproximal Extension

The margin should be generally hidden within embrasure area, extension of the laminate beyond the mesiobuccal and distobuccal line angle of the tooth gives a wraparound effect with etched resin bonds at right angles to the labial surface for increased bond strength


Contact Areas

The contact points are modified by very fine one sided diamond abrasive strip through the adjacent teeth . the abrasive strip is used in an S configuration so that the abrasive side will reshape the contact areas rather than separate them



Sulcular Extension

Preparation ends right at the gingival margin. Extension is carried out with a LVS diamond. A narrow gingival chord is placed to slightly displace the tissues for about 8 to10 minutes. This system of first developing the preparation confluent with the gingival and then placing the retraction chord prior to refining and extending into the sulcus ensures a) access for diamond b) less gingival trauma c) direct vision of margins during all procedures



Sulcular Extension

Preparation ends right at the gingival margin. Extension is carried out with a LVS diamond. A narrow gingival chord is placed to slightly displace the tissues for about 8 to10 minutes. This system of first developing the preparation confluent with the gingival and then placing the retraction chord prior to refining and extending into the sulcus ensures a) access for diamond b) less gingival trauma c) direct vision of margins during all procedures www.indiandentalacademy.com

Finish Line Configurations

Feather or knife edge is most conservative form of preparation

There is difficulty in fabricating thin porcelain margins so invariably a poor marginal fit occurs

Inevitable increased thickness subgingivaly and resultant gingival problems

Laboratory problems in delineating the exact end of the preparation line



Modified Chamfer Finish

This provides increased bulk of porcelain at margins so increased strength

Correct enamel preparation is achieved for increased bond strength

Laboratory procedures are easy with better fit of porcelain

Greater ease for dentist to obtain correct gingival finish line

A definitive stop to aid in seating the laminate to correct position

A sound marginal seal www.indiandentalacademy.com

Incisal Reduction

Fabrication of porcelain lapping the incisal edge makes the placement of restoration much easier by virtue of having a definitive stop

However when added length is needed it is necessary to actually prepare the incisal aspect




Lingual Reduction

Reduction of the incisal edge may require reduction of lingual surface so that there is no butt joint at this incisal/lingual junction but rather a rounded chamfer

This ensures increased thickness of porcelain, enamel bonds at right angles to those at incisal edge, and increased strength


Impression Technique

Tissue management tissue displacement is achieved by retraction cord

Impression

Elastomers –light material and tray material


Temporization

Direct composite veneer Direct composite resin veneer utilizing

vacuum formed matrix Indirect composite resin/acrylic resin

veneer




Laboratory Procedures

The refractory investment technique

The platinum foil technique


The refractory investment technique

Fabrication of master cast Application of die spacer Fabrication of refractory model Preparation of refractory model Degassing the refractory investment Sealant application Removal of veneers from refractory material


Platinum Foil Technique

Choosing the foilModel and die preparationPlatinum matrix placementRemoval of foil


Porcelain application First application of 0.3 to 0.4 thick is made.

Esthetic results of finished veneers are enhanced if the porcelain mix is applied in four stages-gingival third, body, incisal third, enamel shading

Finishing and contouring-microfine diamonds & sandpaper discs are used


Glazing – seals any microporosities & gives more natural luster. Stains can be applied to add chroma

Adjustment and placement on the master modelEtching – 7.5% hydrofluoric acid is etchant,10%

of baking soda is neutralizer, surface is air abraded and washed in detergent in ultra sonic bath




Placement of Veneers

Three stage porcelain veneer try inStage 1: check for individual fitStage 2: collective fit try inStage 3: color check


Procedure of Placement

Tissue management Retraction cords Local anesthesia


It is important to realize that no modification for shape is done until the final seating and curing are completed

The bonding of porcelain laminate is in fact a series of links : etched enamel- to enamel/dentin bonding agent- to luting composite resin- to unfilled resin- to hydrolyzed saline – to etched porcelain


Silanation

The etched surface is treated with silane coupling agent to enhance adhesive properties

Pre activated silane or hydrolyzed form Non hydrolyzed form


Enamel Activation

To remove all surface coatings

Slurry of fine pumice and water with a non webbed rubber cup or brush


Cheek retractors Cotton rollsSaliva ejector


Enamel Etching

30 to 37 % of phosphoric acid solution 15 to 20 seconds

30 seconds Wash with water


Application of dental bonding agent

Apply evenly on the etched enamel and on the internal aspect of the veneer

All excess bonding agent has to be removed


Seating Sequence

It is best to seat one laminate at a timeIn multi unit cases start with the distal

most toothCentrals should always be seated together


Placement

Pulsing or gentle rocking motionPrevent suck backThe matrix strip must be reinserted

between the teeth to prevent them from bonding to one another

Curing should be complete for at least 2 minutes each for various areas


Curing

TimeAngle of contactShade of the resinDistance


Finishing

Magnification and LVS kit finishing instrument

Load should be distributed over as many teeth as possible so that any one veneer extension is not responsible for withstanding the entire load


Cosmetic Contouring

Is done after several days for esthetic harmony

Fine diamonds, micro fine LVS no. 6 or 7 are used

Finishing is done with porcelain polishing wheels and/or diamond polishing paste


Cast Ceramic Laminates

2 distinct systems are present

Castable ceramic(dicor)

Castable apatite (cerapearl)


Conclusion

Dentistry has long sought for the ideal restorative material to esthetically alter unattractive smile

A major breakthrough that facilitated predictable retention of porcelain to tooth structure has added a new dimension to esthetic dentistry.The strength of porcelain laminates will continue to be assessed although relatively technique sensitive the surface texture ,color, fluorescence & overall esthetics have been regarded as exceptional.


REFERENCES

David A garber-porcelain laminate veenersKenneth J Anusavice-phillips science of

dental materialsWunder R et al in vitro effect of fluroide

on porcelain J.Prosthe.Dent 55.[385] 1986



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Porcelain laminates/ orthodontic continuing education

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