Class Ii Amalgam Cavity Preparation For Amalgam 476l5z

CLASS II CAVITY PREPARATION FOR AMALGAM & DESIGN VARIATIONS

CONTENTS I) Definition . II) Tooth preparation  governing factors. 1) Outline form. 2) Resistance form. 3) Retention form. III) Instrumentation. 1) Outline form. 2) Primary resistance form. 3) Primary retention form. 4) Removal of defective E & old restorations. 5) Pulp protection. 6) Secondary resistance & retention. 7) Final procedures.

IV) Designs of cavity preparations. V) Variations of one proximal tooth surface preparations. VI) Modifications in tooth preparation. VII) Extended Cl II amlagam. VIII) Cl II perp. in primary teeth. IX) Conservative preparations. X) References .

CLASS II CAVITY PREPARATION FOR AMALGAM DEFINITION: A Class II cavity preparation is the proximo-facial (lingual), proximoocclusal (or combination there of) tooth preparation.  It is part of mechanotherapy for a smooth surface lesion, involving the proximal surfaces of molars & premolars. 

TOOTH PREPARATION

INITIAL PREPARATIONGoverning factors:  OUTLINE FORM: Following factors dictate the outline form; A) Proportional size of caries in enamel to that in dentin, their relative size to that of uncleansable prox. areas: i) Forward (pit) decay: caries cone in E < uncleansable area 

i)

Backward decay: caries cone does not undermine all enamel.

ii)

Backward decay: caries cone in dentin> uncleansable area

i)

Forward decay: more extensive E decalcification than the limit of self cleansable area.

B) Extension for convinence or access. C) Location & condition of the gingiva.

D) Condition of the marginal ridge. E) Convexity of the proximal surface.

F) Location & extent of the areas & their relation to the marginal ridges, embrasures & gingiva. G) Modifying factors influencing outline form: i) Masticatory loads. ii) Generalized plaque index. iii) Localized cariogenic factors. iv) Esthetics. v) Tooth position.

RESISTANCE FORM: A) Occlusal loading & its effects: i) A small cusp s the fossa away from the restored proximal surface at centric closure. ii) Large cusp s fossa adjacent to the restored prox. surface(centric). 

iii) Occluding cusp s  F & L tooth str. Surrounding a proximo-occlusal restor.

iv) Occluding cusp s  F & L lingual parts of the restor. Surrounded by tooth str.

v) Occluding cusps F & L parts of restor. Completely replacing F & L parts of the tooth structure.

vi) Occluding cusp s restor. Marginal ridge.

vii) Cusp occlude/ discocclude via the F / L groove of the restor.

viii) Cusps & crossing ridges are part of the restor. in centric & excursive movements.

ix) Axial portions of the restoration during centric & excursive movts.

x) Restoration not in / is in premature .

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Amalgam  least resistant to tensile stress. most resistant to compressive stress. Tooth structure when interrupted by cavity prep least resistant to shear stress. Therefore, Cl II cavity prep designed to resist cyclic loading while minimizing tensile loading in amalgam & shear loading in the remaining tooth structure.

B) Design features for protection of the mechanical integrity of the restor. 1) ISTHMUS: The junction b/n the occlusal part of a restor. & the prox. F / L parts.  Potentially deleterious tensile loading occurs.  Mathematical, mech., photoelastic analyses of these stresses reveal; i) Fulcrum of bending occurs at the axiopulpal(A-P) line angle. ii) Stresses ↑ closer to the surface of the restor., away from that of the fulcrum. iii) Tensile stresses predominate at the marginal ridge area of the proximo-occlusal restor.

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Material tends to fail, starting from the surface, near the marginal ridge & proceeding internally, toward the A-P line angle.

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A theoretical solution might be; 1)↑ amalgam bulk at the A-P line angle. 2) Bring A-P line angle closer to the surface

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3)i) Combination of above 2 solutions; a) ↑ amalgam bulk at marginal ridge. b) Bring A-P line angle away from stress conc. area. 

ii) Rounding of A-P line angle. iii) Slanting of axial wall  depth ↑ rather than width. iv) Flat pulpal & gingival floors. v) Every part of the preparation self retentive. vi) Avoid leaving surface discontinuties. vii) Check occlusion.

2) MARGINS: i) Create butt t. ii) Leave no frail enamel. iii) Interface b/n amalgam & tooth str. Should not be at the occluding area. 3)CUSPS & AXIAL ANGLES: Design features in these parts of the restor.; a) Amalgam bulk in all 3Ds at least 1.5mm. b) Each portion completely immobilized with retention modes. c) Amalgam seated on flat floors/ table. d) Amalgam replacing cusps/axial angles should have a bulky connection to the main part of the restor.

C) Design features for th protection of the physiomechanical integrity of the remaining tooth str. 1) Isthmus  1/4 – 1/5 inter cuspal distance. 2) Occlusal surface: i) Divergence of walls toward marginal ridge. ii) Perpend. of walls toward the crossing ridge. iii) Preserving crossing ridges. iv) Three angulation for the walls around cusps. v) Definite royunded line & point angles. vi) Rt.angled cavo surface angles. vii) F & L walls at the isthmus  perpend. To pulpal floor bulk

3) Cusps & axial angles:  Ideal length : width ratio of cuspal wall surrounding a Cl II  1 : 1 or less M-D & B-L.  If >2 : 1  cuspal wall shortened until 1 :1  Every effort made to protect the axial angle. 4) Margins :  F & L margins/walls  meet the proximal surface at a rt. angle.  Present in corresponding embrassures.  When necessary to include a broad area reverse curve given & rt. angled cavo surface maintained.

Usually done on the F- prox.walls & occasionally on L- prox.walls.  Advantage: i) Preserve tooth str. at critical marginal area. ii) Avoid impinging on the pulpal anatomy. iii) Terminate margins in a rt. angled cavosurface. iv) Includes all uncleansable broad s.  Gingival margins  gingival 3rd of involved prox. surface.  Gingival floors  2 planed  bevel  15-200 

In direct access Cl II prox.cavity prep.  Occlusal wall one planed  divergent towards that marginal ridge  direction of E rods.  if retention deficient  2 planes. 

RETENTION FORM:  4 types of displacements for Cl II proximo-occlusal restoration. a) Proximal displacement of the entire restoration.

b) Proximal displacement of the prox.portion.

c) Lateral rotation of the restor. around hemispherical floors.

d) Occlusal displacement.  Although magnitude of these 4 displacements is minute, they are repeated 1000 times/day.  This will ↑ microleakage.  Initiate mech. & bio. failure of the restor. & tooth str.  Proper locking of the restor. into the tooth should be exercised to minimize these hazards.

INSTRUMENTATION INITIAL CLINICAL PROCEDURES: 1) Local anesthesia. 2) Occlusal s 3) Rubber dam placement 4) Tooth preparation. Initial tooth preparation: 1)Occlusal outline form ( occlusal step ):  Similar to Cl I prep.  No 245 bur used.  Long axis of the bur parallel to the long axis of the tooth. 

Using high speed with air water spray, enter the pit near the involved prox. surface.  Initial depth 1.5mm  from the central fissure  2.0mm  from the external wall of prepared tooth. 

Pulpal depth  0.1-0.2mm into the dentin.  Pulpal floor  flat.  Isthmus width  not wider than 1/4th the ICD.  B & L walls  convergence.  Dove-tail retention form.  Enameloplasty where ever necessary. 

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Reverse curve.

Occlusal outline should end approx. 0.8mm short of marginal ridge. Proximal outline form ( Prox. Box ):  Objectives for extension; 1) Include all caries, faults or existing restor. 2) Create a 900 cavo-surface margins. 3) Establish not > 0.5mm clearance with the adj. prox. surface ( F, L, G ).  Initial step  Prox. Ditch cut. 

 2/3rd

at the expense of dentin.  1/3rd  E.  Extend the ditch G just beyond the caries or prox. which ever is greater.  Should clear the adjacent tooth by 0.5mm  PM may have prox.boxes shallower pulpally ( thinner enamel ).

 Ideal

dentinal depth of the axial wall  0.5-0.6mm.  If in cementum  0.7-0.8mm.

2)Primary resistance form:  Provided by, 1) Flat pulpal & gingival floors. 2) Restricting extension of walls & preserving strong cusps. 3) Reverse curve. 4) Slight rounding of internal line & point angles. 5) Enough thickness of restor. material. 3)Primary retention form:  Provided by, 1) Occlusal convergence of F & L walls. 2) Dove-tail design.

Final tooth preparation: 4) Removal of any defective E & infected carious dentin. 5) Pulp protection. 6) Secondary retention & resistance forms:  Secondary retention by,  Retention locks.  No.169L bur used.  On AF & AL line angles.  Should be 0.2mm inside the DEJ.  Terminate at the Axio-linguo (bucco) pulpal point angle, diminishing in depth occlusally.

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characteristics of prox. locks, 1) Position : refers to AF / AL line angle of the prep.tooth. 2) Translation : the direction of movement of long axis of the bur. 3) Depth :extent of translation. 4) Occluso-gingival orientation : tilt of No.169L bur which dictates occlusal height of the lock.

7) Procedures for finishing external walls:  Removal of uned E & marginal irregularities.  Butt t relationship.  Slight cavo-surface bevel at gingival margin  6 centigrade / 200 declination.  Gingival marginal trimmer is used.  When G margin in cementum  no bevel. 8) Final procedures : Cleaning, inspecting, bonding.

DESIGNS OF CLASS II CAVITY PREPARATION 1) Cl II, design 1 (Conventional design ) : Involvement : proximal & occlusal surfaces. Indications : a) moderate- large size lesion with similar sized occlusal lesion. b) Undermined marginal ridge. c) Caries cone necessitate cavity width to .1/4 th ICD. General shape : Occlusally  similar to Cl I , design 1 or 2. dove-tail only on one side. Proximally  inverted truncated cone. Location of the margins : Occlusal portion : similar to Cl I design 1 or 2.

Proximal portion : F & L margins  in corresponding embrassures.  Tips of the explorer must freely. Gingival portion : ideally  occlusal portion of the gingival sulcus space. Isthmus portion : F & L margins  on the inclined planes of corresponding cusps & remaining portion of marginal ridge.  Separated not more than 1/3rd ICD.

Internal anatomy: Occlusally : similar to Cl I design 1 or 2. Proximally : M-D cross section : If gingival margin on cementum  flat. in G 1/3rd  2 planed. in the middle 3rd  as in young & incompletely erupted teeth, 1 plane. Axial wall  slanted toward pulpal floor, making an obtuse angle with gingival floor.  rounded.  retention locks.

2) Cl II, design 2 ( Modern design ): Involvement : proximal & occlusal surfaces. Indications : a) moderate – small sized prox.lesion ( not extending the area of near approach ). b) Occlusal lesion  not exceeding 1/4th ICD. General shape : Occlusal portion : similar to Cl I design 1 & sometimes 2.  Very little if any dove-tail shape. Proximal portion:  Unilateral inverted truncated cone.

In upper teeth  lingual inverted truncated cone only.  Lower teeth  buccal inverted truncated cone only.  This feature done on functional side only. 

Location of the margins: Occlusal portion : similar to Cl I design 1 Proximal portion : gingival to area. Isthmus portion : F & L margins  separated not > 1/4th ICD.  Reverse curve.

Internal anatomy : Occlusal portion : similar to Cl I, Design 1. Proximal portion : M – D cross section :  Similar to conventional design.  all line angles rounded, with exception of G-A line angle kept sharp  stabilization of restor.

Preparation modifications : In Tapered teeth (bell shaped ) : grooves having maximal dimension at the pulpal floor level ( reverse that of conventional design ).

3) Cl II, design 3 ( Conservative design ) : Involvement : Primarily proximal, very little occlusal not beyond the adj. triangular fossa. Indications : a) Decay in prox.surface only & occlusally sound. b) Restor. subjected to minimal loading. General shape : Inverted truncated cone located totally proximally. The tip involves part of adj. occlusal triangular fossa. Location of margins : Occlusally : occlusal inclined plane of the involved marginal ridge.  F & L margins  very limited. Proximally : similar to modern design.

Internal anatomy : M – D cross section : Gingival floor: i) If in G 3rd  3 planes. ii) In middle 3rd  2 planes. Axial wall  slanted ( > than in modern design). F – L cross section :  Axial wall  convex.  Prox.surface  3 planesif margins are at F / L 3rd of prox.surface.  2 planes  if at middle 3rd.

4) Cl II, design 4 ( Simple design ): Involvement : proximal surface only. Indications : a) Decay restricted to areas. b) There is diastema/ adj. tooth is missing. c) Rotated /inclined teeth. d) Prox. lesion located very G at / apical to CEJ, gingival recession ( senile decay). e) Tapered tooth with wide gingival embrassure. f) Occlusal embrasures pronounced in dimensions.

General shape :  No specific shape.  Assumes a trapezoidal/ rhomboidal shape. Location of the margin :  If diastema pr.  no specific location of margin.  If apical to ( senile decay) O & G margins G embrasures. F & L margins  in F & L embrasures.  If at area ( clinical/ anatomical)  O margin  O embrasure. G margin  G embrasure just clearing the area. F & L margins  corres. embr. With more extension on the access side.

Internal anatomy : F – L cross section: Axial wall flat – slight covex F-L. If at furcation area  concave F-L, paralleling the surface concavity. O – G cross section: Gingival floor : i) On cementum  2 planes. ii) On E  3 planes.

5) Cl II, design 5 : Involvement : part of the prox. surface with a very little access area on the F & L surface. Indications : 2 shapes In Shape A: F & L access will not have dove-tail. a) Small – medium sized prox.lesion. b) Marginal ridge intact. c) Does not involve area. d) Gingival embrasure not accessible. Cavity  4 definite walls, with opposing retentive grooves in at least 2 of them.

Shape B: F & L access will have a locking feature in the form of dove-tail, unilaterally cut in occlusal direction. a) Medium – large sized prox.lesion. Cavity  will not have 4 walls, either one wall / no wall bulky enough to accommodate a groove. General shape :  No specific shape.  May appear trapezoidal/elliptical.  F & L part  Shape A  box/ rectangular. Shape B  one sided dovetail.

Location of margins : G margins  G embr. O margins  G embr. Just apical to area. F & L margins  on the non access side  in corres. Embr. Short of axial angle of the tooth. On access side  far enough onto F/L surface to include axial angle (max. 1/4th F/L surface). Internal anatomy: O – G cross section:  Axial wall  flat / concave.  O& G walls  if on C & D  2 planes. if on E  one plane. F – L cross section: 2 axial walls  one prox. & another F / L . Rounded axio- axial line angle. Proximal axial wall  slightly slanted towards the access side.

6) Cl II , design 6 : Involvement : the O, P & part of the F & L surfaces. Indications: a) the cusp length is double or more its width. b) Cusp completely missing or undermined. c) Foundation for cast restor. required. d) Doubtful prognosis endodontically & peridontically. e) Badly broken down teeth that need to be prepared prior to endo/ortho tr. General shape : O & P parts  similar to design 1 or 2. F & L parts  rectangular in outline.

Location of margin : O & P portion similar to design 1 or 2. F & L portions  in areas at / occlusal to the ht. of contour of the F & L surfaces.  Do not place margin in grooves.  If margin comes near a groove  include in cavity prep.  In areas apical to the ht.of contour F & L  same as G 3rd of prox.surfaces. Internal anatomy: O & P  similar to design 1 or 2.

Rules to prep.a cusp: 1) Cusp to be replaced reduce 1.52.0mm from opposing cuspal elements.more on functional cusp. 2) Cusp  cut flat in the form of table, with rt.angled cavo-surface margins. 3) Mini length : width  1:1 4) If cusp undermined  tabled until there is intact E ed by sound D. 5) Remaining part of cavity should have sufficient retention. 6) Never place pins on tables which will accommodate amalgam cusps/part of cusps. 7) In multiple tables  junction rounded.

7) Cl II , design 7 : Involvement : Shape A junction b/w the Cl II & Cl V via proximal, crossing the axial angle. General shape : O portion  similar to design 1 or 2. P-F & P- F portion  if unilateral extension F/L  L shaped. Bilateral  inverted T shaped.

Shape B : junction b/w the Cl II & Cl V is through the occlusal via the B &/ L groove. General shape: O & P portions  design 1 or 2. F & L portions  inverted T shaped.

8) Cl II , design 8 : Involvement : 2 or more surfaces of an endo. tr. tooth that does not requirec post retention. Indications: a) tooth has sufficient pulp chamber to accommodate retaining, self resisting amalgam bulk ( mini.2mm in 3Ds) b) Post endo. Pulp chamber has atleast 2 opposing intact walls. c) Tooth contains sufficient large root canals to accommodate amalgam at its O 1/3rd (mini.1.5mm) d) A foundation is needed for reinforcing restor. General shape : similar to design 6.

Internal anatomy: Rules to arrive to the finished product; 1) Excavate  residual RC filling from pulp chamber. Bare dentin exposed. 2) Large RC that can accommodate an amalgam 1.5mm RC filling removed to 3-4mm depth.

3) If possible “square up” surrounding walls. 4) In bulky portions of the surrounding walls cut flat ledges receive most of the occlusal loading.

5) Try to make every part self retentive. 6) Each flat portion of the prep.  reciprocated  to immobilize the restor. & evenly distribute the stress.

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VARIATIONS OF ONE PROXIMAL SURFACE TOOTH PREPARATIONS

MANDIBULAR 1ST PREMOLAR: Relatively small size of lingual cusp. Excessive extension in facial direction approach/ expose the facial pulp horn. Variety of occlusal patterns  exhibit a large transverse ridge of enamel.

2) MAXILLARY 1ST MOLAR:  When unaffected oblique ridge present separate 2 surface tooth prep. are indicated. 3) MAXILLARY 1ST PREMOLAR:  Cl II involving mesial surface special attention M – F embr. esthetically prominent.  If M-P involvement; 1) Is limited to a fissure in the marginal ridge, 2) Not treatable by enameloplasty, 3) Does not involve the prox., Then, prepare prox. portion with margins lingual to the . Distal surface involvement prep. in conventional modes.

MODIFICATIONS IN TOOTH PREPARATIONS 1) SLOT PREPARATION/BOX-ONLY PREPARATION: Outline form:  Access to the prox.lesion through  marginal ridge.  Create a slot cut with a small bur, in the center of the crest of the ridge.  Slot deepened gingivally.  1-2mm below the point.  Total distance b/w marginal ridge & the gingival floor 3-4mm.

Retention & resistance forms:  occlusal convergence.  M-D dimension1.5mm or more.  G floor flat.  F – L dimension 1/4th ICD.  If extension into occlusal surface narrower, or if there is no extension into occlusal grooves retentive under cuts( grooves/points).

 Retentive

under cuts oppose each other to form a dove-tail effect in the dentin.  0.25-0.5mm of dentin b/w groove & DEJ.  Groove 0.5mm deep & 0.5mm wide. Mechanical retention:  If prox.box/slot wide amalgam bonding / self threading pins placed horizontally/vertically.

Slot prep. for root caries: (KEY-HOLE PREPARATION/ FACIAL/LINGUAL SLOT PREPARATION)  Usually approached from F  form of slot.  Depth axially0.75-1mm at G aspect if no E pr.  1-1.25mm at O wall, if margin in E.  If O margin in E axial depth 0.5mm inside the DEJ.  Retention grooves O-A & G-A line angles.  0.2mm inside the DEJ or 0.3-0.5mm inside the cemental cavo-surface margin.  Depth of the groove1/2 the diameter of the bur head(0.25mm)

2) ROTATED TEETH: Outline form for M-O tooth prep. on rotated teeth differs.  prox.box displaced F / L.  When rotated 900  prox.prep on F/L surface. 3) ADING RESTORATION:  It is permissible to repair /replace a defective portion of an existing AgF restor. if remaining portion of the original restor. adequate rete. & resist. Form.  Intersecting margins of the 2 restor.  at rt.angles as much as possible.

4) ABUTMENT TEETH FOR RPD:  If rest seat is planned in restor. need additional extension.  0.5mm (mini) of AgF b/w rest seat & margins.  Pulpal wall apical to planned rest seat 0.5mm deepened.  Total depth of A-P line angle measured on F & L wall 2.5mm.

EXTENDED CL II AMALGAM 

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Unlike incipient cavity prep. F-G & L-G angles  sharp. Depth of the axial wall  1.2mm wide  PM 1.8mm wide  M

Depth of the decay  does not influence the width of the gingival floor.

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Retentive grooves  deeper at their gingival ends, diminish occlusally. If extends up the cuspal inclines  pulpal depth  1.5mm. & slight tilt of the bur. When O outline within 2/3rd dist. to cusp tip  capping considered.  >2/3rd  capping mandatory.

CL II PREARATION IN PRIMARY TEETH MORPHOLOGIC VARIATIONS: 1) E & D thickness less. 2) Prominent pulp horns. 3) Large pulp chambers. 4) Wider area placed more cervically. 5) Bulbous buccal contour & cervical constriction. 6) E rod direction  in cervical region facing occlusally. 7) Narrow occlusal table.

Outline form: Occlusal :  restrict the size as small as possible.  Depth 1.5mm(0.5mm from DEJ)  B-L wall covergence.  Cavity  1/4th B-L width of the tooth.  Isthmus width 1/3rd – ½ of the ICD (<1.5mm)  Pulpal floor mortise form, should follow the pulpal contour.  Line & pt. angles rounded.  If possibility of pulpal exposure  “stepwise pulpal floor” prepared.

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If lot of cuspal destruction pr. grind off the cusps. No reverse S curve ( unless indicated due to very tight & wide ).

Proximal box:  Should follow the outer contour of the tooth.  Width more due to wider areas.  Flaring done, too much avoided.  B & L walls convergence.  Cavo-surface 900  Axial wall parallel to outer surface.  Width at the floor of the box  1mm.  A-P line angle  rounded.  Axial wall 1mm.

Gingival floor:  area near the constriction area.  Should not be placed too ginivally.  Just beneath the point.  Depth not more than 1mm.or else pulpal exposure.  Floor inclination inwards “Bronner inclination”5-100  for R & R form.  G floor not more than 1mm 1st M. not more than 1.5mm 2nd M.  Angle b/w axial wall &G floor rounded.  Bevelling  not required.  Retention grooves not required, if placed B-A/L-A only.

Main differences: 1) Flaring of the prox. Box. 2) Placement of gingival seat. 3) Bevel.

CONSERVATIVE CAVITY PREPARATIONS TUNNEL PREPARATION: Advantages : 1) Preserves marginal ridge. 2) area not disturbed. 3) Risk of over hang  minimal. Disadvantages : 1) Complete excavation of caries not feasible. 2) Marginal adaptability of restor.  poor. 3) Difficulty in insertion & finishing of restor. 

BONDED AMALGAM RESTORATIONS : Advocated by Varga, Matsumura & Masuhara (1986) & Staninec & Holt (1988). ( Operative dentistry -2005, 30-2, 231)  Indications : 1) Auxillary retention, reinforcement, conservative prep. & improvement of marginal seal. 2) Extensive involvement & cast restor. not affordable. 3) As temporary resotr. which later reduced to core under cast restor. 4) As amalgam sealant. 

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1) 2) 3) 4)

Disadvantages of unbonded technique: Microleakage. Recurrent caries. Post operative sensitivity. Tooth #.

 1) 2) 3) 4) 5) 6)

Advantages of bonded technique : Tooth reinforcement. ↓ post operative sensitivity. Better marginal adaptation. ↓ microleakage. ↓ possibility of secondary caries. More conservative prep. ( Operative dentistry -2005, 30-2, 231).

Disadvantages: 1) Technique sensitive. 2) Long term clinical studies  success rate less. 3) Hydrolytic stability of bond  ? 4) ↑ cost of amalgam restor. 

 1) 2) 3) 4) 5)

Materials used : Amalgam bond plus ( Parkwell ). Panavia EX ( Kuraray ). Rely X ARC ( 3 M ). Barrier . All Bond 2 & liner F ( Bisco ).

REFERENCES OPERATIVE DENTISTRY– Modern theory & practice ( 1st edition )  M.A.Marzouk. 2) ART & SCIENCE OF OPERATIVE DENTISTRY. (5th edition)  Sturdevant. 3) FUNDAMENTALS OF OPERATIVE DENTISTRY ( 2nd edition )  Summit. 4) TEXT BOOK OF OPERATIVE DENTISTRY. ( 3rd edition )  Baum & Phillips. 5) TEXT BOOK OF OPERATIVE DENTISTRY. 1)

( 4th edition )  Mc Gehee. 6) TEXT BOOK OF OPERATIVE DENTISTRY. ( 1st edition )  Vimal K Sikri.

7) G.V.BLACK’S OPERATIVE DENTISTRY. ( 9th edition )  Arthur. D .Black 8) CLINICAL PEDODONTICS. ( 4th edition )  Finn. 9) OPERATIVE DENTISTRY 2000, 25, 121-128. 10) OPERATIVE DENTISTRY 2000, 25,177-178 11) OPERATIVE DENTISTRY 2001, 26, 81. 12) OPERATIVE DENTISTRY 2001, 26, 239-243. 13) OPERATIVE DENTISTRY 2005, 30, 228-233 .