CLASS II CAVITY CLASS II CAVITY PREPARATION PREPARATION

FORFOR AMALGAM AMALGAM

& DESIGN & DESIGN VARIATIONSVARIATIONS

CONTENTSCONTENTS

I) I) Definition .Definition .II) II) Tooth preparationTooth preparation governing factors. governing factors. 1) Outline form.1) Outline form. 2) Resistance form.2) Resistance form. 3) Retention form.3) Retention form.III) III) Instrumentation.Instrumentation. 1) Outline form.1) Outline form. 2) Primary resistance form.2) Primary resistance form. 3) Primary retention form.3) Primary retention form. 4) Removal of defective E & old 4) Removal of defective E & old

restorations.restorations. 5) Pulp protection.5) Pulp protection. 6) Secondary resistance & retention.6) Secondary resistance & retention. 7) Final procedures. 7) Final procedures.

IV)IV) Designs of cavity preparations.Designs of cavity preparations.

V) Variations of one proximal tooth V) Variations of one proximal tooth surface preparations.surface preparations.

VI) Modifications in tooth preparation.VI) Modifications in tooth preparation.

VII) Extended Cl II amlagam.VII) Extended Cl II amlagam.

VIII) Cl II perp. in primary teeth.VIII) Cl II perp. in primary teeth.

IX) Conservative preparations.IX) Conservative preparations.

X) ReferencesX) References . .

CLASS II CAVITY CLASS II CAVITY PREPARATION FOR PREPARATION FOR

AMALGAMAMALGAM DEFINITION:DEFINITION:

A Class II cavity preparation is the A Class II cavity preparation is the proximo-facial (lingual), proximo-proximo-facial (lingual), proximo-occlusal (or combination there of) occlusal (or combination there of) tooth preparation.tooth preparation.

It is part of mechanotherapy for a It is part of mechanotherapy for a smooth surface lesion, involving the smooth surface lesion, involving the proximal surfaces of molars & proximal surfaces of molars & premolars.premolars.

TOOTH PREPARATIONTOOTH PREPARATION INITIAL PREPARATION-INITIAL PREPARATION-

Governing factors:Governing factors: OUTLINE FORM:OUTLINE FORM:

Following factors dictate the Following factors dictate the outline form;outline form;

A)A) Proportional size of caries in Proportional size of caries in enamel to that in dentin, enamel to that in dentin, their relative size to that of their relative size to that of uncleansable prox. areas:uncleansable prox. areas:

i)i) Forward (pit) decay: caries Forward (pit) decay: caries cone in E < uncleansable cone in E < uncleansable areaarea

i)i) Backward decay: caries Backward decay: caries cone does not undermine cone does not undermine all enamel.all enamel.

ii)ii) Backward decay: caries Backward decay: caries cone in dentin> cone in dentin> uncleansable areauncleansable area

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

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

gingiva.gingiva.

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

F) Location & extent of the contact F) Location & extent of the contact areas & their relation to the areas & their relation to the marginal ridges, embrasures & marginal ridges, embrasures & gingiva.gingiva.

G) Modifying factors influencing G) Modifying factors influencing outline form:outline form:

i)i) Masticatory loads.Masticatory loads.

ii)ii) Generalized plaque index.Generalized plaque index.

iii)iii) Localized cariogenic factors.Localized cariogenic factors.

iv)iv) Esthetics.Esthetics.

v)v) Tooth position.Tooth position.

RESISTANCE FORM:RESISTANCE FORM:

A)A) Occlusal loading & its Occlusal loading & its effects:effects:

i) A small cusp contacts the i) A small cusp contacts the fossa away from the fossa away from the restored proximal surfacerestored proximal surface at centric closure.at centric closure.

ii) Large cusp contactsii) Large cusp contacts fossa fossa adjacent to the restored adjacent to the restored prox. surface(centric).prox. surface(centric).

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

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

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

vi) Occluding cuspvi) Occluding cusp contacts restor. contacts restor. Marginal ridge.Marginal ridge.

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

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

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

x) Restoration not in contact / is in x) Restoration not in contact / is in premature contact.premature contact.

Amalgam Amalgam least resistant to tensile least resistant to tensile stress.stress.

most resistant to most resistant to compressive compressive

stress.stress. Tooth structure when interrupted by Tooth structure when interrupted by

cavity prepcavity prep least resistant to shear least resistant to shear stress.stress.

Therefore, Cl II cavity prepTherefore, Cl II cavity prep designed designed to resist to resist cyclic loadingcyclic loading while minimizing while minimizing tensiletensile loadingloading in amalgam & in amalgam & shear shear loadingloading in the remaining tooth in the remaining tooth structure. structure.

B) Design features for protection of the B) Design features for protection of the mechanical integrity of the restor.mechanical integrity of the restor.

1)1) ISTHMUSISTHMUS: : The junction b/n the occlusal part of a The junction b/n the occlusal part of a

restor. & the prox. F / L parts.restor. & the prox. F / L parts. Potentially deleterious tensile loading Potentially deleterious tensile loading

occurs.occurs. Mathematical, mech., photoelastic Mathematical, mech., photoelastic

analyses of these stresses reveal;analyses of these stresses reveal;i)i) Fulcrum of bending occurs at the axio-Fulcrum of bending occurs at the axio-

pulpal(A-P) line angle.pulpal(A-P) line angle.ii)ii) Stresses Stresses ↑ closer to the surface of the ↑ closer to the surface of the

restor., away from that of the fulcrum.restor., away from that of the fulcrum.iii)iii) Tensile stresses predominate at the Tensile stresses predominate at the

marginal ridge area of the proximo-marginal ridge area of the proximo-occlusal restor.occlusal restor.

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

A theoretical solution might be;A theoretical solution might be; 1)1)↑ amalgam bulk at the A-P line ↑ amalgam bulk at the A-P line

angle.angle. 2) Bring A-P line angle closer to 2) Bring A-P line angle closer to

the surfacethe surface

3)i) Combination of above 2 3)i) Combination of above 2 solutions;solutions;

a) ↑ amalgam bulk at marginal ridge.a) ↑ amalgam bulk at marginal ridge.

b) Bring A-P line angle away from b) Bring A-P line angle away from stress conc. area.stress conc. area.

ii) Rounding of A-P line angle.ii) Rounding of A-P line angle.

iii) Slanting of axial wall iii) Slanting of axial wall depth depth ↑ ↑ rather than width.rather than width.

iv) Flat pulpal & gingival floors.iv) Flat pulpal & gingival floors.

v) Every part of the preparation self v) Every part of the preparation self retentive.retentive.

vi) Avoid leaving surface vi) Avoid leaving surface discontinuties.discontinuties.

vii) Check occlusion.vii) Check occlusion.

2) MARGINS2) MARGINS::

i)i) Create butt joint.Create butt joint.

ii)ii) Leave no frail enamel.Leave no frail enamel.

iii)iii) Interface b/n amalgam & tooth str. Should Interface b/n amalgam & tooth str. Should not be at the occluding contact area.not be at the occluding contact area.

3)CUSPS & AXIAL ANGLES3)CUSPS & AXIAL ANGLES::

Design features in these parts of the restor.;Design features in these parts of the restor.;

a)a) Amalgam bulk in all 3DsAmalgam bulk in all 3Ds at least 1.5mm. at least 1.5mm.

b)b) Each portion completely immobilized with Each portion completely immobilized with retention modes.retention modes.

c)c) Amalgam seated on flat floors/ table.Amalgam seated on flat floors/ table.

d)d) Amalgam replacing cusps/axial angles Amalgam replacing cusps/axial angles should have a bulky connection to the should have a bulky connection to the main part of the restor. main part of the restor.

C) Design features for th protection of the C) Design features for th protection of the physio-mechanical integrity of the remaining physio-mechanical integrity of the remaining tooth str.tooth str.

1)1) IsthmusIsthmus 1/4 – 1/5 inter cuspal distance. 1/4 – 1/5 inter cuspal distance.

2)2) Occlusal surface:Occlusal surface:

i)i) Divergence of walls toward marginal ridge.Divergence of walls toward marginal ridge.

ii)ii) Perpend. of walls toward the crossing ridge.Perpend. of walls toward the crossing ridge.

iii)iii) Preserving crossing ridges.Preserving crossing ridges.

iv)iv) Three angulation for the walls around cusps.Three angulation for the walls around cusps.

v)v) Definite royunded line & point angles.Definite royunded line & point angles.

vi)vi) Rt.angled cavo surface angles.Rt.angled cavo surface angles.

vii)vii) F & L walls at the isthmusF & L walls at the isthmus perpend. To perpend. To pulpal floorpulpal floor bulk bulk

3) Cusps & axial angles:3) Cusps & axial angles: Ideal length : width ratio of cuspal Ideal length : width ratio of cuspal

wall surrounding a Cl II wall surrounding a Cl II 1 : 1 or 1 : 1 or less M-D & B-L.less M-D & B-L.

If >2 : 1 If >2 : 1 cuspal wall shortened cuspal wall shortened until 1 :1until 1 :1

Every effort made to protect the Every effort made to protect the axial angle.axial angle.

4) Margins4) Margins : : F & L margins/wallsF & L margins/walls meet the meet the

proximal surface at a rt. angle.proximal surface at a rt. angle. Present in corresponding Present in corresponding

embrassures.embrassures. When necessary to include a broad When necessary to include a broad

contact areacontact area reverse curve given reverse curve given & rt. angled cavo surface & rt. angled cavo surface maintained.maintained.

Usually done on the F- prox.walls & Usually done on the F- prox.walls & occasionally on L- prox.walls.occasionally on L- prox.walls.

Advantage:Advantage:

i) Preserve tooth str. at critical marginal area.i) Preserve tooth str. at critical marginal area.

ii) Avoid impinging on the pulpal anatomy.ii) Avoid impinging on the pulpal anatomy.

iii) Terminate margins in a rt. angled cavo- iii) Terminate margins in a rt. angled cavo- surface.surface.

iv) Includes all uncleansable broad contacts.iv) Includes all uncleansable broad contacts.

Gingival marginsGingival margins gingival 3 gingival 3rdrd of involved of involved prox. surface.prox. surface.

Gingival floors Gingival floors 2 planed 2 planed bevel bevel 15- 15-202000

In direct access Cl II prox.cavity In direct access Cl II prox.cavity prep.prep.

Occlusal wall one planed Occlusal wall one planed divergent towards that marginal divergent towards that marginal ridge ridge direction of E rods. direction of E rods.

if retention deficient if retention deficient 2 planes. 2 planes.

RETENTION FORM:RETENTION FORM: 4 types of displacements for Cl II 4 types of displacements for Cl II

proximo-occlusal restoration.proximo-occlusal restoration.

a) Proximal displacement of the entire a) Proximal displacement of the entire restoration.restoration.

b) Proximal displacement of the b) Proximal displacement of the prox.portion.prox.portion.

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

d) Occlusal displacement.d) Occlusal displacement. Although magnitude of these 4 Although magnitude of these 4

displacements is minute, they are displacements is minute, they are repeated 1000 times/day.repeated 1000 times/day.

This will This will ↑ microleakage.↑ microleakage. Initiate mech. & bio. failure Initiate mech. & bio. failure of the of the

restor. & tooth str.restor. & tooth str. Proper locking of the restor. into the Proper locking of the restor. into the

tooth should be exercised to tooth should be exercised to minimize these hazards. minimize these hazards.

INSTRUMENTATIONINSTRUMENTATION INITIAL CLINICAL PROCEDURES:INITIAL CLINICAL PROCEDURES:1)1) Local anesthesia.Local anesthesia.2)2) Occlusal contactsOcclusal contacts3)3) Rubber dam placementRubber dam placement4)4) Tooth preparation.Tooth preparation.Initial tooth preparation:Initial tooth preparation:1)Occlusal outline form1)Occlusal outline form ( occlusal step ): ( occlusal step ): Similar to Cl I prep.Similar to Cl I prep. No 245 bur used.No 245 bur used. Long axis of the bur parallel to the long axis of Long axis of the bur parallel to the long axis of

the tooth.the tooth.

Using high speed with air water spray, Using high speed with air water spray, enter the pit near the involved prox. enter the pit near the involved prox. surface.surface.

Initial depth 1.5mm Initial depth 1.5mm from the central from the central fissurefissure

2.0mm 2.0mm from the external wall from the external wall of prepared tooth.of prepared tooth.

Pulpal depth Pulpal depth 0.1-0.2mm into the dentin. 0.1-0.2mm into the dentin. Pulpal floor Pulpal floor flat. flat. Isthmus width Isthmus width not wider than 1/4 not wider than 1/4thth the the

ICD.ICD. B & L walls B & L walls convergence. convergence. Dove-tail retention form.Dove-tail retention form. Enameloplasty where ever necessary.Enameloplasty where ever necessary.

Reverse curve.Reverse curve.

Occlusal outline should end approx. Occlusal outline should end approx. 0.8mm short of marginal ridge.0.8mm short of marginal ridge.

Proximal outline form Proximal outline form ( Prox. Box ):( Prox. Box ): Objectives for extension;Objectives for extension;1)1) Include all caries, faults or existing Include all caries, faults or existing

restor.restor.2)2) Create a 90Create a 900 0 cavo-surface margins.cavo-surface margins.3)3) Establish not > 0.5mm clearance Establish not > 0.5mm clearance

with the adj. prox. surface ( F, L, G ).with the adj. prox. surface ( F, L, G ). Initial step Initial step Prox. Ditch cut. Prox. Ditch cut.

2/32/3rdrd at the expense of at the expense of dentin.dentin.

1/31/3rdrd E. E. Extend the ditch G just Extend the ditch G just

beyond the caries or beyond the caries or prox.contact which ever is prox.contact which ever is greater.greater.

Should clear the adjacent Should clear the adjacent tooth by 0.5mmtooth by 0.5mm

PM may have prox.boxes PM may have prox.boxes shallower pulpally ( thinner shallower pulpally ( thinner enamel ).enamel ).

Ideal dentinal depth of the axial wall Ideal dentinal depth of the axial wall 0.5-0.6mm. 0.5-0.6mm.

If in cementum If in cementum 0.7-0.8mm. 0.7-0.8mm.

2)Primary resistance form:2)Primary resistance form: Provided by,Provided by,

1)1) Flat pulpal & gingival floors.Flat pulpal & gingival floors.

2)2) Restricting extension of walls & Restricting extension of walls & preserving strong cusps.preserving strong cusps.

3)3) Reverse curve.Reverse curve.

4)4) Slight rounding of internal line & point Slight rounding of internal line & point angles.angles.

5)5) Enough thickness of restor. material.Enough thickness of restor. material.

3)Primary retention form:3)Primary retention form: Provided by,Provided by,

1)1) Occlusal convergence of F & L walls.Occlusal convergence of F & L walls.

2)2) Dove-tail design.Dove-tail design.

Final tooth preparation:Final tooth preparation:4) Removal of any defective E & infected 4) Removal of any defective E & infected

carious dentin.carious dentin.5) Pulp protection.5) Pulp protection.6) Secondary retention & resistance 6) Secondary retention & resistance

forms:forms: Secondary retention by,Secondary retention by, Retention locks.Retention locks. No.169L bur used.No.169L bur used. On AF & AL line angles.On AF & AL line angles. Should be 0.2mm inside the DEJ.Should be 0.2mm inside the DEJ. Terminate at the Axio-linguo (bucco) Terminate at the Axio-linguo (bucco)

pulpal point angle, diminishing in pulpal point angle, diminishing in depth occlusally.depth occlusally.

4 characteristics of prox. locks,4 characteristics of prox. locks,

1)1) PositionPosition : refers to AF / AL line angle : refers to AF / AL line angle of the prep.tooth.of the prep.tooth.

2)2) TranslationTranslation : the direction of : the direction of movement of long axis of the bur.movement of long axis of the bur.

3)3) DepthDepth :extent of translation. :extent of translation.

4)4) Occluso-gingival orientationOccluso-gingival orientation : tilt of : tilt of No.169L bur which dictates occlusal No.169L bur which dictates occlusal height of the lock.height of the lock.

7) Procedures for finishing external walls:7) Procedures for finishing external walls: Removal of unsupported E & marginal Removal of unsupported E & marginal

irregularities.irregularities. Butt joint relationship.Butt joint relationship. Slight cavo-surface bevel at gingival Slight cavo-surface bevel at gingival

margin margin 6 centigrade / 20 6 centigrade / 2000 declination. declination. Gingival marginal trimmer is used.Gingival marginal trimmer is used. When G margin in cementumWhen G margin in cementum no bevel. no bevel.

8) Final procedures : Cleaning, inspecting,8) Final procedures : Cleaning, inspecting, bonding.bonding.

DESIGNS OF CLASS II DESIGNS OF CLASS II CAVITY PREPARATIONCAVITY PREPARATION

1) Cl II, design 1 (Conventional design ) :1) Cl II, design 1 (Conventional design ) :InvolvementInvolvement : proximal & occlusal surfaces. : proximal & occlusal surfaces.IndicationsIndications : a) moderate- large size lesion with : a) moderate- large size lesion with

similar sized occlusal lesion.similar sized occlusal lesion.b) Undermined marginal ridge.b) Undermined marginal ridge.c) Caries cone necessitate cavity width to .1/4c) Caries cone necessitate cavity width to .1/4thth

ICD.ICD. General shapeGeneral shape : :OcclusallyOcclusally similar to Cl I , design 1 or 2. dove- similar to Cl I , design 1 or 2. dove-

tail only on one side.tail only on one side.ProximallyProximally inverted truncated cone. inverted truncated cone.Location of the marginsLocation of the margins : :Occlusal portionOcclusal portion : similar to Cl I design 1 or 2. : similar to Cl I design 1 or 2.

Proximal portionProximal portion : F & L margins : F & L margins in in corresponding embrassures.corresponding embrassures.

Tips of the explorer must pass Tips of the explorer must pass freely.freely.

Gingival portionGingival portion : ideally : ideally occlusal occlusal portion of the gingival sulcus space.portion of the gingival sulcus space.

Isthmus portionIsthmus portion : F & L margins : F & L margins on on the inclined planes of corresponding the inclined planes of corresponding cusps & remaining portion of cusps & remaining portion of marginal ridge.marginal ridge.

Separated not more than 1/3Separated not more than 1/3rdrd ICD. ICD.

Internal anatomyInternal anatomy::

OcclusallyOcclusally : similar to Cl I design 1 or 2. : similar to Cl I design 1 or 2.

ProximallyProximally : :

M-D cross sectionM-D cross section : :

If gingival margin on cementum If gingival margin on cementum flat. flat.

in G 1/3in G 1/3rdrd 2 planed. 2 planed.

in the middle 3in the middle 3rd rd as in young as in young & incompletely erupted teeth, 1 & incompletely erupted teeth, 1 plane.plane.

Axial wall Axial wall slanted toward pulpal slanted toward pulpal floor, making an obtuse angle with floor, making an obtuse angle with gingival floor.gingival floor.

rounded.rounded.

retention locks. retention locks.

2) Cl II, design 2 ( Modern design ):2) Cl II, design 2 ( Modern design ):

Involvement Involvement : proximal & occlusal surfaces.: proximal & occlusal surfaces.

IndicationsIndications : a) moderate – small sized : a) moderate – small sized prox.lesion ( not extending the area of prox.lesion ( not extending the area of near approach ).near approach ).

b) Occlusal lesion b) Occlusal lesion not exceeding 1/4 not exceeding 1/4thth ICD.ICD.

General shapeGeneral shape : :

Occlusal portionOcclusal portion : similar to Cl I design 1 & : similar to Cl I design 1 &

sometimes 2.sometimes 2. Very little if any dove-tail shape.Very little if any dove-tail shape.

Proximal portion:Proximal portion:

Unilateral inverted truncated cone.Unilateral inverted truncated cone.

In upper teeth In upper teeth lingual inverted lingual inverted truncated cone only.truncated cone only.

Lower teeth Lower teeth buccal inverted buccal inverted truncated cone only.truncated cone only.

This feature done on functional side This feature done on functional side only.only.

Location of the marginsLocation of the margins::Occlusal portionOcclusal portion : similar to Cl I design : similar to Cl I design

11Proximal portionProximal portion : gingival to contact : gingival to contact

area.area. Isthmus portionIsthmus portion : F & L margins : F & L margins

separated not > 1/4separated not > 1/4thth ICD. ICD. Reverse curve.Reverse curve.

Internal anatomyInternal anatomy : :

Occlusal portionOcclusal portion : similar to Cl I, : similar to Cl I, Design 1.Design 1.

Proximal portionProximal portion : :

M – D cross sectionM – D cross section : : Similar to conventional design.Similar to conventional design. all line angles rounded, with all line angles rounded, with

exception of G-A line angleexception of G-A line angle kept kept sharp sharp stabilization of restor. stabilization of restor.

Preparation modificationsPreparation modifications : :

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

3) Cl II, design 3 ( Conservative design ) :3) Cl II, design 3 ( Conservative design ) :InvolvementInvolvement : Primarily proximal, very little occlusal : Primarily proximal, very little occlusal

not beyond the adj. triangular fossa.not beyond the adj. triangular fossa.IndicationsIndications : a) Decay in prox.surface only & : a) Decay in prox.surface only &

occlusally sound.occlusally sound.b) Restor. subjected to minimal loading.b) Restor. subjected to minimal loading.General shapeGeneral shape : :Inverted truncated cone located totally proximally.Inverted truncated cone located totally proximally.The tip involves part of adj. occlusal triangular The tip involves part of adj. occlusal triangular

fossa.fossa.Location of marginsLocation of margins : :OcclusallyOcclusally : occlusal inclined plane of the involved : occlusal inclined plane of the involved

marginal ridge.marginal ridge. F & L margins F & L margins very limited. very limited.ProximallyProximally : similar to modern design. : similar to modern design.

Internal anatomyInternal anatomy : :M – D cross sectionM – D cross section : :Gingival floorGingival floor::i)i) If in G 3If in G 3rdrd 3 planes. 3 planes.ii)ii) In middle 3In middle 3rdrd 2 planes. 2 planes.Axial wall Axial wall slanted ( > than in slanted ( > than in

modern design).modern design).F – L cross sectionF – L cross section : : Axial wall Axial wall convex. convex. Prox.surface Prox.surface 3 planes 3 planesif if

margins are at F / L 3margins are at F / L 3rdrd of of prox.surface.prox.surface.

2 planes 2 planes if at middle 3 if at middle 3rdrd..

4) Cl II, design 4 ( Simple design ):4) Cl II, design 4 ( Simple design ):

Involvement Involvement : proximal surface only.: proximal surface only.

IndicationsIndications : a) Decay restricted to : a) Decay restricted to contact areas.contact areas.

b) There is diastema/ adj. tooth is b) There is diastema/ adj. tooth is missing.missing.

c) Rotated /inclined teeth.c) Rotated /inclined teeth.

d) Prox. lesion located very G at / d) Prox. lesion located very G at / apical to CEJ, gingival recession apical to CEJ, gingival recession ( senile decay).( senile decay).

e) Tapered tooth with wide gingival e) Tapered tooth with wide gingival embrassure.embrassure.

f) Occlusal embrasures pronounced in f) Occlusal embrasures pronounced in dimensions.dimensions.

General shapeGeneral shape : : No specific shape.No specific shape. Assumes a trapezoidal/ rhomboidal shape.Assumes a trapezoidal/ rhomboidal shape.Location of the marginLocation of the margin : : If diastema pr. If diastema pr. no specific location of no specific location of

margin.margin. If apical to contact( senile decay)If apical to contact( senile decay) O & G O & G

marginsmargins G embrasures. G embrasures. F & L margins F & L margins in F & L embrasures. in F & L embrasures. If at contact area ( clinical/ anatomical) If at contact area ( clinical/ anatomical)

O margin O margin O embrasure. O embrasure. G margin G margin G embrasure just clearing the G embrasure just clearing the

contact area.contact area. F & L margins F & L margins corres. embr. With more corres. embr. With more

extension on the access side.extension on the access side.

Internal anatomyInternal anatomy : :

F – L cross sectionF – L cross section::

Axial wallAxial wall flat – slight covex flat – slight covex F-L.F-L.

If at furcation area If at furcation area concave F-L, paralleling concave F-L, paralleling the surface concavity.the surface concavity.

O – G cross section:O – G cross section:

Gingival floorGingival floor : :

i)i) On cementum On cementum 2 planes. 2 planes.

ii)ii) On E On E 3 planes. 3 planes.

5) Cl II, design 55) Cl II, design 5 : :

InvolvementInvolvement : part of the prox. surface : part of the prox. surface with a very little access area on the with a very little access area on the F & L surface.F & L surface.

IndicationsIndications : 2 shapes : 2 shapes

In Shape AIn Shape A: F & L access will not have : F & L access will not have dove-tail.dove-tail.

a)a) Small – medium sized prox.lesion.Small – medium sized prox.lesion.

b)b) Marginal ridge intact.Marginal ridge intact.

c)c) Does not involve contact area.Does not involve contact area.

d)d) Gingival embrasure not accessible.Gingival embrasure not accessible.

Cavity Cavity 4 definite walls, with 4 definite walls, with opposing retentive grooves in at opposing retentive grooves in at least 2 of them.least 2 of them.

Shape BShape B: F & L access will have a locking : F & L access will have a locking feature in the form of dove-tail, feature in the form of dove-tail, unilaterally cut in occlusal direction.unilaterally cut in occlusal direction.

a)a) Medium – large sized prox.lesion.Medium – large sized prox.lesion.Cavity Cavity will not have 4 walls, either one will not have 4 walls, either one

wall / no wall bulky enough to wall / no wall bulky enough to accommodate a groove.accommodate a groove.

General shapeGeneral shape : : No specific shape.No specific shape. May appear trapezoidal/elliptical.May appear trapezoidal/elliptical. F & L part F & L part Shape A Shape A box/ box/

rectangular.rectangular. Shape B Shape B one sided dove- one sided dove-

tail. tail.

Location of marginsLocation of margins : :G margins G margins G embr. G embr.O margins O margins G embr. Just apical to contact area. G embr. Just apical to contact area.F & L margins F & L margins on the non access side on the non access side in in

corres. Embr. Short of axial angle of the tooth.corres. Embr. Short of axial angle of the tooth. On access side On access side far enough onto F/L surface to far enough onto F/L surface to

include axial angle (max. 1/4include axial angle (max. 1/4thth F/L surface). F/L surface).Internal anatomy:Internal anatomy:O – G cross sectionO – G cross section:: Axial wall Axial wall flat / concave. flat / concave. O& G walls O& G walls if on C & D if on C & D 2 planes. 2 planes. if on E if on E one plane. one plane.F – L cross sectionF – L cross section::2 axial walls 2 axial walls one prox. & another F / L . one prox. & another F / L .Rounded axio- axial line angle.Rounded axio- axial line angle.Proximal axial wall Proximal axial wall slightly slanted towards the slightly slanted towards the

access side. access side.

6) Cl II , design 66) Cl II , design 6 : :

InvolvementInvolvement : the O, P & part of the F & L : the O, P & part of the F & L surfaces.surfaces.

IndicationsIndications: a) the cusp length is double or : a) the cusp length is double or more its width.more its width.

b) Cusp completely missing or undermined.b) Cusp completely missing or undermined.

c) Foundation for cast restor. required.c) Foundation for cast restor. required.

d) Doubtful prognosis endodontically & d) Doubtful prognosis endodontically & peridontically.peridontically.

e) Badly broken down teeth that need to be e) Badly broken down teeth that need to be prepared prior prepared prior to endo/ortho tr.to endo/ortho tr.

General shapeGeneral shape : :

O & P parts O & P parts similar to design 1 or 2. similar to design 1 or 2.

F & L parts F & L parts rectangular in outline. rectangular in outline.

Location of marginLocation of margin : :O & P portionO & P portion similar to design 1 or 2. similar to design 1 or 2.F & L portions F & L portions in areas at / occlusal to in areas at / occlusal to

the ht. of contour of the F & L surfaces.the ht. of contour of the F & L surfaces. Do not place margin in grooves.Do not place margin in grooves. If margin comes near a grooveIf margin comes near a groove

include in cavity prep.include in cavity prep. In areas apical to the ht.of contour F & In areas apical to the ht.of contour F &

L L same as G 3 same as G 3rdrd of prox.surfaces. of prox.surfaces.Internal anatomyInternal anatomy::O & P O & P similar to design 1 or 2. similar to design 1 or 2.

Rules to prep.a cuspRules to prep.a cusp::1)1) Cusp to be replacedCusp to be replaced reduce 1.5- reduce 1.5-

2.0mm from opposing cuspal 2.0mm from opposing cuspal elements.more on functional cusp.elements.more on functional cusp.

2)2) Cusp Cusp cut flat in the form of table, cut flat in the form of table, with rt.angled cavo-surface margins.with rt.angled cavo-surface margins.

3)3) Mini length : width Mini length : width 1:1 1:14)4) If cusp undermined If cusp undermined tabled until tabled until

there is intact E supported by sound there is intact E supported by sound D.D.

5)5) Remaining part of cavity should have Remaining part of cavity should have sufficient retention.sufficient retention.

6)6) Never place pins on tables which will Never place pins on tables which will accommodate amalgam cusps/part of accommodate amalgam cusps/part of cusps.cusps.

7)7) In multiple tables In multiple tables junction rounded. junction rounded.

7) Cl II , design 77) Cl II , design 7 : :

InvolvementInvolvement : : Shape AShape A junction b/w junction b/w the Cl II & Cl V via proximal, the Cl II & Cl V via proximal, crossing the axial angle.crossing the axial angle.

General shapeGeneral shape : :

O portion O portion similar to design 1 or 2. similar to design 1 or 2.

P-F & P- F portion P-F & P- F portion if unilateral if unilateral extension F/L extension F/L L shaped. L shaped.

Bilateral Bilateral inverted T shaped. inverted T shaped.

Shape BShape B : junction b/w the Cl II & Cl V : junction b/w the Cl II & Cl V is through the occlusal via the B &/ L is through the occlusal via the B &/ L groove.groove.

General shapeGeneral shape::

O & P portions O & P portions design 1 or 2. design 1 or 2.

F & L portions F & L portions inverted T shaped. inverted T shaped.

8) Cl II , design 88) Cl II , design 8 : :

IInvolvementnvolvement : 2 or more surfaces of an : 2 or more surfaces of an endo. tr. tooth that does not requirec endo. tr. tooth that does not requirec post retention.post retention.

IndicationsIndications: a) tooth has sufficient pulp : a) tooth has sufficient pulp chamber to accommodate retaining, self chamber to accommodate retaining, self resisting amalgam bulk ( mini.2mm in resisting amalgam bulk ( mini.2mm in 3Ds)3Ds)

b) Post endo. Pulp chamber has atleast 2 b) Post endo. Pulp chamber has atleast 2 opposing intact walls.opposing intact walls.

c) Tooth contains sufficient large root c) Tooth contains sufficient large root canalscanals to accommodate amalgam at its to accommodate amalgam at its O 1/3O 1/3rdrd (mini.1.5mm) (mini.1.5mm)

d) A foundation is needed for reinforcing d) A foundation is needed for reinforcing restor.restor.

General shapeGeneral shape : similar to design 6. : similar to design 6.

Internal anatomyInternal anatomy::

RulesRules to arrive to the finished to arrive to the finished product;product;

1)1) Excavate Excavate residual RC filling residual RC filling from pulp chamber. Bare from pulp chamber. Bare dentin exposed.dentin exposed.

2)2) Large RC that can Large RC that can accommodate an amalgam accommodate an amalgam 1.5mm1.5mm RC filling removed RC filling removed to 3-4mm depth.to 3-4mm depth.

3) If possible “square up” surrounding 3) If possible “square up” surrounding walls.walls.

4) In bulky portions of the surrounding 4) In bulky portions of the surrounding wallswalls cut flat ledges cut flat ledges receive most receive most of the occlusal loading.of the occlusal loading.

5) Try to make every part self retentive.5) Try to make every part self retentive.

6) Each flat portion of the prep. 6) Each flat portion of the prep. reciprocated reciprocated to immobilize the to immobilize the restor. & evenly distribute the stress.restor. & evenly distribute the stress.

VARIATIONS OF ONE VARIATIONS OF ONE PROXIMAL SURFACE PROXIMAL SURFACE

TOOTH PREPARATIONSTOOTH PREPARATIONS1)1) MANDIBULAR 1MANDIBULAR 1STST PREMOLAR PREMOLAR:: Relatively small size of lingual Relatively small size of lingual

cusp.cusp. Excessive extension in facial Excessive extension in facial

directiondirection approach/ expose approach/ expose the facial pulp horn.the facial pulp horn.

Variety of occlusal patterns Variety of occlusal patterns exhibit a large transverse ridge exhibit a large transverse ridge of enamel.of enamel.

22) MAXILLARY 1) MAXILLARY 1STST MOLAR MOLAR:: When unaffected oblique ridge presentWhen unaffected oblique ridge present

separate 2 surface tooth prep. are separate 2 surface tooth prep. are indicated.indicated.

3) MAXILLARY 13) MAXILLARY 1STST PREMOLAR: PREMOLAR: Cl II involving mesial surfaceCl II involving mesial surface special special

attentionattention M – F embr. M – F embr. esthetically esthetically prominent.prominent.

If M-P involvement;If M-P involvement;1)1) Is limited to a fissure in the marginal ridge,Is limited to a fissure in the marginal ridge,2)2) Not treatable by enameloplasty,Not treatable by enameloplasty,3)3) Does not involve the prox.contact, Does not involve the prox.contact, Then, prepare prox. portion with marginsThen, prepare prox. portion with margins

lingual to the contact.lingual to the contact.Distal surface involvementDistal surface involvement prep. in prep. in

conventional modes.conventional modes.

MODIFICATIONS IN MODIFICATIONS IN TOOTH PREPARATIONSTOOTH PREPARATIONS

1) SLOT PREPARATION/BOX-ONLY 1) SLOT PREPARATION/BOX-ONLY PREPARATION:PREPARATION:

Outline formOutline form:: Access to the prox.lesion Access to the prox.lesion

throughthrough marginal ridge. marginal ridge. Create a slot cut with a small bur, Create a slot cut with a small bur,

in the center of the crest of the in the center of the crest of the ridge.ridge.

Slot deepened gingivally.Slot deepened gingivally. 1-2mm below the contact point.1-2mm below the contact point. Total distance b/w marginal ridge Total distance b/w marginal ridge

& the gingival floor& the gingival floor 3-4mm. 3-4mm.

Retention & resistance formsRetention & resistance forms::

occlusal convergence.occlusal convergence. M-D dimensionM-D dimension1.5mm or more.1.5mm or more. G floorG floor flat. flat. F – L dimensionF – L dimension 1/4 1/4thth ICD. ICD. If extension into occlusal surface If extension into occlusal surface

narrower, or if there is no extension narrower, or if there is no extension into occlusal groovesinto occlusal grooves retentive retentive under cuts( grooves/points).under cuts( grooves/points).

Retentive under cutsRetentive under cuts oppose each oppose each other to form a dove-tail effect in the other to form a dove-tail effect in the dentin.dentin.

0.25-0.5mm of dentin b/w groove & 0.25-0.5mm of dentin b/w groove & DEJ.DEJ.

Groove 0.5mm deep & 0.5mm wide.Groove 0.5mm deep & 0.5mm wide.

Mechanical retentionMechanical retention::

If prox.box/slotIf prox.box/slot wide wide amalgam amalgam bonding / self threading pins placed bonding / self threading pins placed horizontally/vertically.horizontally/vertically.

Slot prep. for root caries: Slot prep. for root caries: (KEY-(KEY-HOLE PREPARATION/ HOLE PREPARATION/ FACIAL/LINGUAL SLOT FACIAL/LINGUAL SLOT PREPARATION)PREPARATION)

Usually approached from F Usually approached from F form of slot.form of slot.

Depth axiallyDepth axially0.75-1mm at G 0.75-1mm at G aspect if no E pr.aspect if no E pr.

1-1.25mm at O wall, if margin in E.1-1.25mm at O wall, if margin in E. If O margin in EIf O margin in E axial depth axial depth

0.5mm inside the DEJ.0.5mm inside the DEJ. Retention groovesRetention grooves O-A & G-A O-A & G-A

line angles.line angles. 0.2mm inside the DEJ or 0.3-0.2mm inside the DEJ or 0.3-

0.5mm inside the cemental cavo-0.5mm inside the cemental cavo-surface margin.surface margin.

Depth of the grooveDepth of the groove1/2 the 1/2 the diameter of the bur head(0.25mm)diameter of the bur head(0.25mm)

2) 2) ROTATED TEETHROTATED TEETH::Outline form for M-O tooth prep.Outline form for M-O tooth prep. on on

rotated teethrotated teeth differs. differs. prox.box displacedprox.box displaced F / L. F / L. When rotated 90When rotated 9000 prox.prep on F/L prox.prep on F/L

surface.surface.3) 3) ADJOINING RESTORATIONADJOINING RESTORATION:: It is permissible to repair /replace a It is permissible to repair /replace a

defective portion of an existing AgF defective portion of an existing AgF restor.restor. if remaining portion of the if remaining portion of the original restor.original restor. adequate rete. & adequate rete. & resist. Form.resist. Form.

Intersecting margins of the 2 restor. Intersecting margins of the 2 restor. at rt.angles as much as possible. at rt.angles as much as possible.

4) 4) ABUTMENT TEETH FOR RPDABUTMENT TEETH FOR RPD:: If rest seat is planned in restor.If rest seat is planned in restor.

need additional extension.need additional extension. 0.5mm (mini) of AgF b/w rest seat & 0.5mm (mini) of AgF b/w rest seat &

margins.margins. Pulpal wall apical to planned rest Pulpal wall apical to planned rest

seatseat 0.5mm deepened. 0.5mm deepened. Total depth of A-P line angle Total depth of A-P line angle

measured on F & L wallmeasured on F & L wall 2.5mm. 2.5mm.

EXTENDED CL II EXTENDED CL II AMALGAMAMALGAM

Unlike incipient cavity prep.Unlike incipient cavity prep. F-G & L-G F-G & L-G angles angles sharp. sharp.

Depth of the axial wall Depth of the axial wall 1.2mm wide 1.2mm wide PM PM

1.8mm wide 1.8mm wide M M

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

Retentive grooves Retentive grooves deeper at their deeper at their gingival ends, diminish occlusally.gingival ends, diminish occlusally.

If extends up the cuspal inclines If extends up the cuspal inclines pulpal depth pulpal depth 1.5mm. & slight tilt 1.5mm. & slight tilt of the bur.of the bur.

When O outlineWhen O outline within 2/3 within 2/3rdrd dist. dist. to cusp tip to cusp tip capping considered. capping considered.

>2/3>2/3rdrd capping mandatory. capping mandatory.

CL II PREARATION IN CL II PREARATION IN PRIMARY TEETHPRIMARY TEETH

MORPHOLOGIC VARIATIONSMORPHOLOGIC VARIATIONS::1)1) E & DE & D thickness less. thickness less.2)2) Prominent pulp horns.Prominent pulp horns.3)3) Large pulp chambers.Large pulp chambers.4)4) Wider contact areaWider contact area placed more placed more

cervically.cervically.5)5) Bulbous buccal contour & cervical Bulbous buccal contour & cervical

constriction.constriction.6)6) E rod direction E rod direction in cervical region facing in cervical region facing

occlusally.occlusally.7)7) Narrow occlusal table.Narrow occlusal table.

Outline formOutline form::OcclusalOcclusal : : restrict the size as small as restrict the size as small as

possible.possible. Depth Depth 1.5mm(0.5mm from DEJ)1.5mm(0.5mm from DEJ) B-L wallB-L wall covergence. covergence. Cavity Cavity 1/4 1/4thth B-L width of the tooth. B-L width of the tooth. Isthmus widthIsthmus width 1/3 1/3rdrd – ½ of the ICD – ½ of the ICD

(<1.5mm)(<1.5mm) Pulpal floorPulpal floor mortise form, should follow the mortise form, should follow the

pulpal contour.pulpal contour. Line & pt. anglesLine & pt. angles rounded. rounded. If possibility of pulpal exposureIf possibility of pulpal exposure “stepwise “stepwise

pulpal floor” prepared.pulpal floor” prepared.

If lot of cuspal destruction pr.If lot of cuspal destruction pr. grind off the grind off the cusps.cusps.

No reverse S curve ( unless indicated due to No reverse S curve ( unless indicated due to very tight & wide contact).very tight & wide contact).

Proximal boxProximal box:: Should follow the outer contour of the Should follow the outer contour of the

tooth.tooth. WidthWidth more due to wider contact more due to wider contact

areas.areas. Flaring done, too much avoided.Flaring done, too much avoided. B & L walls B & L walls convergence.convergence. Cavo-surfaceCavo-surface 90 9000 Axial wallAxial wall parallel to outer surface. parallel to outer surface. WidthWidth at the floor of the box at the floor of the box

1mm.1mm. A-P line angle A-P line angle rounded. rounded. Axial wall Axial wall 1mm.1mm.

Gingival floorGingival floor:: Contact areaContact area near the constriction near the constriction

area.area. Should not be placed too ginivally.Should not be placed too ginivally. Just beneath the contact point.Just beneath the contact point. Depth not more than 1mm.or elseDepth not more than 1mm.or else

pulpal exposure.pulpal exposure. Floor inclination inwardsFloor inclination inwards “Bronner “Bronner

inclination”5-10inclination”5-100 0 for R & R form. for R & R form. G floorG floor not more than 1mm not more than 1mm 1 1stst M. M. not more than 1.5mmnot more than 1.5mm 2 2ndnd

M.M. Angle b/w axial wall &G floor Angle b/w axial wall &G floor

rounded.rounded. Bevelling Bevelling not required. not required. Retention groovesRetention grooves not required, if not required, if

placed B-A/L-A only.placed B-A/L-A only.

Main differencesMain differences::

1)1) Flaring of the prox. Box.Flaring of the prox. Box.

2)2) Placement of gingival seat.Placement of gingival seat.

3)3) Bevel.Bevel.

CONSERVATIVE CAVITY CONSERVATIVE CAVITY PREPARATIONSPREPARATIONS

TUNNEL PREPARATIONTUNNEL PREPARATION::

Advantages Advantages ::

1) Preserves marginal ridge.1) Preserves marginal ridge.

2) Contact area not disturbed.2) Contact area not disturbed.

3) Risk of over hang 3) Risk of over hang minimal. minimal.

Disadvantages Disadvantages ::

1)1) Complete excavation of caries not Complete excavation of caries not feasible.feasible.

2)2) Marginal adaptability of restor.Marginal adaptability of restor. poor. poor.

3)3) Difficulty in insertion & finishing of Difficulty in insertion & finishing of restor.restor.

BONDED AMALGAM RESTORATIONSBONDED AMALGAM RESTORATIONS : :Advocated by Varga, Matsumura & Advocated by Varga, Matsumura &

Masuhara (1986) & Staninec & Holt Masuhara (1986) & Staninec & Holt (1988).(1988).

( Operative dentistry -2005, 30-( Operative dentistry -2005, 30-2, 231)2, 231)

IndicationsIndications : :1)1) Auxillary retention, reinforcement, Auxillary retention, reinforcement,

conservative prep. & improvement of conservative prep. & improvement of marginal seal.marginal seal.

2)2) Extensive involvement & cast restor. not Extensive involvement & cast restor. not affordable.affordable.

3)3) As temporary resotr. which later reduced As temporary resotr. which later reduced to core under cast restor.to core under cast restor.

4)4) As amalgam sealant.As amalgam sealant.

Disadvantages of unbonded Disadvantages of unbonded techniquetechnique::

1)1) Microleakage.Microleakage.

2)2) Recurrent caries.Recurrent caries.

3)3) Post operative sensitivity.Post operative sensitivity.

4)4) Tooth #.Tooth #.

Advantages of bonded techniqueAdvantages of bonded technique : :

1)1) Tooth reinforcement.Tooth reinforcement.

2)2) ↓ ↓ post operative sensitivity.post operative sensitivity.

3)3) Better marginal adaptation.Better marginal adaptation.

4)4) ↓ ↓ microleakage.microleakage.

5)5) ↓ ↓ possibility of secondary caries.possibility of secondary caries.

6)6) More conservative prep.More conservative prep.

( Operative dentistry -2005, ( Operative dentistry -2005, 30-2, 231).30-2, 231).

DisadvantagesDisadvantages::

1) Technique sensitive.1) Technique sensitive.

2) Long term clinical studies 2) Long term clinical studies success rate less.success rate less.

3) Hydrolytic stability of bond 3) Hydrolytic stability of bond ? ?

4) ↑ cost of amalgam restor.4) ↑ cost of amalgam restor.

Materials usedMaterials used : :

1)1) Amalgam bond plus ( Parkwell ).Amalgam bond plus ( Parkwell ).

2)2) Panavia EX ( Kuraray ).Panavia EX ( Kuraray ).

3)3) Rely X ARC ( 3 M ).Rely X ARC ( 3 M ).

4)4) Barrier .Barrier .

5)5) All Bond 2 & liner F ( Bisco ).All Bond 2 & liner F ( Bisco ).

REFERENCESREFERENCES

1)1) OPERATIVE DENTISTRY– Modern theory & OPERATIVE DENTISTRY– Modern theory & practice practice

( 1( 1stst edition ) edition ) M.A.Marzouk.M.A.Marzouk.2) ART & SCIENCE OF OPERATIVE DENTISTRY. 2) ART & SCIENCE OF OPERATIVE DENTISTRY. (5(5thth edition) edition) Sturdevant. Sturdevant.3) FUNDAMENTALS OF OPERATIVE DENTISTRY 3) FUNDAMENTALS OF OPERATIVE DENTISTRY ( 2( 2ndnd edition ) edition ) Summit.Summit.4) TEXT BOOK OF OPERATIVE DENTISTRY. 4) TEXT BOOK OF OPERATIVE DENTISTRY. ( 3( 3rdrd edition ) edition ) Baum & Phillips.Baum & Phillips.5) TEXT BOOK OF OPERATIVE DENTISTRY. 5) TEXT BOOK OF OPERATIVE DENTISTRY.

( 4( 4thth edition ) edition ) Mc Gehee.Mc Gehee.6) TEXT BOOK OF OPERATIVE DENTISTRY. 6) TEXT BOOK OF OPERATIVE DENTISTRY. ( 1( 1stst edition ) edition ) Vimal K Sikri.Vimal K Sikri.

7) G.V.BLACK’S OPERATIVE DENTISTRY.7) G.V.BLACK’S OPERATIVE DENTISTRY. ( 9( 9thth edition ) edition ) Arthur. D .BlackArthur. D .Black8) CLINICAL PEDODONTICS.8) CLINICAL PEDODONTICS. ( 4( 4thth edition ) edition ) Finn.Finn.9) OPERATIVE DENTISTRY 2000, 25, 121-128.9) OPERATIVE DENTISTRY 2000, 25, 121-128.10) OPERATIVE DENTISTRY 2000, 25,177-17810) OPERATIVE DENTISTRY 2000, 25,177-17811) OPERATIVE DENTISTRY 2001, 26, 81.11) OPERATIVE DENTISTRY 2001, 26, 81.12) OPERATIVE DENTISTRY 2001, 26, 239-243.12) OPERATIVE DENTISTRY 2001, 26, 239-243.13) OPERATIVE DENTISTRY 2005, 30, 228-23313) OPERATIVE DENTISTRY 2005, 30, 228-233..