Dr. lama khaled El Banna Faculty of Oral and Dental Medicine Al – Azhar University operative dentistry

2. College of DentistryCollege of Dentistry
Operative Dentistry IOperative Dentistry I
Fundamental of Cavity PreparationFundamental of Cavity Preparation
-1-1--
Dr. Hazem El AjramiDr. Hazem El Ajrami

3. • There are some fundamental principles whichThere are some fundamental principles which
must be realized in preparing cavities for themust be realized in preparing cavities for the
reception of restorative materials. Thesereception of restorative materials. These
fundamentals must be intelligently applied andfundamentals must be intelligently applied and
adhered to in all cases since failure of the wholeadhered to in all cases since failure of the whole
procedure might occur if any of theprocedure might occur if any of the
fundamentals is violated or neglected. Thesefundamentals is violated or neglected. These
fundamentals are essentially discussed underfundamentals are essentially discussed under
biologic, mechanicalbiologic, mechanical andand estheticesthetic perspectives.perspectives.

4. A.A. Biologic fundamentals:Biologic fundamentals:
These fundamentals are primarily concernedThese fundamentals are primarily concerned
with thewith the health and integrityhealth and integrity of the remainingof the remaining
tooth tissues. They dictate protection of thetooth tissues. They dictate protection of the
dentin, the pulp, the periodontium anddentin, the pulp, the periodontium and
prevention of caries recurrence together withprevention of caries recurrence together with
working with aseptic procedures.working with aseptic procedures.

5. I.I. Protection of the dentin and the pulp:Protection of the dentin and the pulp:
The pulp which is the highly specializedThe pulp which is the highly specialized
and sensitive vital structure within the toothand sensitive vital structure within the tooth
must be protected against all sorts ofmust be protected against all sorts of
irritation during cutting. The irritation mayirritation during cutting. The irritation may
be traumaticbe traumatic (mechanical), thermal, chemical(mechanical), thermal, chemical
oror bacterial.bacterial. To protect the pulp againstTo protect the pulp against
irritation, several considerations should beirritation, several considerations should be
followed during the cavity preparation.followed during the cavity preparation.

6. Mechanical irritation:Mechanical irritation:
The following points should beThe following points should be avoided:avoided:
Excessive cutting of enamel (width)Excessive cutting of enamel (width) since thissince this
will expose larger area of dentin. Increase inwill expose larger area of dentin. Increase in
cavity width causes weakening of thecavity width causes weakening of the
remaining tooth structure and subjects it toremaining tooth structure and subjects it to
more mechanical irritation.more mechanical irritation.
Overcutting of dentin (depth)Overcutting of dentin (depth) and unnecessaryand unnecessary
deepening of the cavity. The deeper the cavity,deepening of the cavity. The deeper the cavity,
the more the pulp will be irritated because thethe more the pulp will be irritated because the
remaining protective dentin bridge will beremaining protective dentin bridge will be
decreased.decreased.

7. Unnecessary application of excessive pressureUnnecessary application of excessive pressure
on the dentin forming the base of a deep cavity;on the dentin forming the base of a deep cavity;
only gentle pressure must be employed eitheronly gentle pressure must be employed either
during the use of hand or rotary instruments,during the use of hand or rotary instruments,
especially if this pressure is directed pulpwards.especially if this pressure is directed pulpwards.
Improper use of probes or instruments in theImproper use of probes or instruments in the
deep pulpal floor will transmit more mechanicaldeep pulpal floor will transmit more mechanical
pressure and might cause pulp exposure.pressure and might cause pulp exposure.
Cutting across the recessional lines of the pulp;Cutting across the recessional lines of the pulp;
the excavation of soft dentin must be carried outthe excavation of soft dentin must be carried out
parallel to the pulp in scooping action and layerparallel to the pulp in scooping action and layer
by layer.by layer.

9. Thermal irritation:Thermal irritation:
There is always an unavoidable degree ofThere is always an unavoidable degree of
frictional heat resulting during cavityfrictional heat resulting during cavity
preparation. The ultimate goal of the clinicianpreparation. The ultimate goal of the clinician
is to keep it within the physiological toleranceis to keep it within the physiological tolerance
of the dentin-pulp organ i.e. within the limitsof the dentin-pulp organ i.e. within the limits
of the TTZof the TTZ (Thermal Tolerance Zone)(Thermal Tolerance Zone) ofof
dentin which ranges between 85-132°fdentin which ranges between 85-132°f (29-(29-
56°C).56°C).

10. • Thermal irritation during cavity preparationThermal irritation during cavity preparation
could becould be controlled bycontrolled by::
Minimizing the frictional heatMinimizing the frictional heat resultingresulting
during cavity preparation via:during cavity preparation via:
Decreasing pressure,Decreasing pressure, decreasing thedecreasing the areaarea
of cutting as well as theof cutting as well as the amountamount andand timetime ofof
cutting.cutting.
Using tools withUsing tools with high cutting efficiency.high cutting efficiency.
The tool should be sharp, of proper size andThe tool should be sharp, of proper size and
appropriate for the desired function.appropriate for the desired function.

11. The use of coolants. Air-waterThe use of coolants. Air-water spray jet isspray jet is
considered to be the most appropriate since theconsidered to be the most appropriate since the
use of air drying only could desiccate theuse of air drying only could desiccate the
dentin while the use of water coolant onlydentin while the use of water coolant only
impairs the visibility during work.impairs the visibility during work.

13. • The coolant must fulfill the followingThe coolant must fulfill the following
requirements:requirements:
It must beIt must be copiouscopious in amount, within amount, with adequateadequate
rate.rate.
It should beIt should be multidirectional,multidirectional, to produce an all-to produce an all-
over cooling effect on the tooth.over cooling effect on the tooth.
It should be of theIt should be of the same temperaturesame temperature as that ofas that of
the mouth i.e.the mouth i.e. 37°C.37°C. Lower temperatures causeLower temperatures cause
fogging, alters vision and may irritate the pulp.fogging, alters vision and may irritate the pulp.
On the other hand, higher temperatures will notOn the other hand, higher temperatures will not
be that effective in cooling.be that effective in cooling.

14. Chemical irritation:Chemical irritation:
The possibility of chemical irritation to theThe possibility of chemical irritation to the
pulp during cavity preparation may be resortedpulp during cavity preparation may be resorted
to the use of chemicals during toilet of theto the use of chemicals during toilet of the
cavity. Cavity cleansers (or cavity sterilizers)cavity. Cavity cleansers (or cavity sterilizers)
like phenolic agents proved to have anlike phenolic agents proved to have an
insignificant role in preventing or decreasinginsignificant role in preventing or decreasing
secondary caries and thus their use wassecondary caries and thus their use was
discontinued.discontinued.

15. • It was hypothized thatIt was hypothized that acidic dentin conditionersacidic dentin conditioners
used with bonded restorations might cause aused with bonded restorations might cause a
degree of chemical irritation to the pulp.degree of chemical irritation to the pulp.
However, recent researches indicated thatHowever, recent researches indicated that
chemical irritation to dentin-pulp organchemical irritation to dentin-pulp organ does notdoes not
induce a harmful effect in itself, even in deepinduce a harmful effect in itself, even in deep
cavities, if bacterial contamination is eliminated.cavities, if bacterial contamination is eliminated.
The controversy about the pulpal chemicalThe controversy about the pulpal chemical
irritation is, essentially, due to the inability toirritation is, essentially, due to the inability to
correlate a cause/effect relationship and to thecorrelate a cause/effect relationship and to the
wide variations of pulpal response to irritants.wide variations of pulpal response to irritants.

16. • It is now widely accepted that the use ofIt is now widely accepted that the use of
certified conditioners, primers and adhesives,certified conditioners, primers and adhesives,
with full respect to its instructions, will notwith full respect to its instructions, will not
produce damaging effects to the pulp. Thisproduce damaging effects to the pulp. This
could be due tocould be due to proper sealingproper sealing of dentin andof dentin and
significant improvement ofsignificant improvement of marginal adaptationmarginal adaptation
of restorations, which are farof restorations, which are far more importantmore important inin
preventing pulpal irritation.preventing pulpal irritation.

17. Bacterial irritation:Bacterial irritation:
To avoid cross infection during cavityTo avoid cross infection during cavity
preparation,preparation, sterilizationsterilization of instruments, bursof instruments, burs
and armamentarium is essential. In case of veryand armamentarium is essential. In case of very
deep cavities with very thin remaining dentindeep cavities with very thin remaining dentin
bridge barrier, the use of rubber dam tobridge barrier, the use of rubber dam to isolateisolate
the field of operation becomes mandatory tothe field of operation becomes mandatory to
prevent bacterial contamination from saliva orprevent bacterial contamination from saliva or
neighboring teeth if accidental pulp exposureneighboring teeth if accidental pulp exposure
occurs.occurs.

18. II.II. Control of caries:Control of caries:
Secondary or recurrent caries may occur atSecondary or recurrent caries may occur at
the margins of any restoration or may spreadthe margins of any restoration or may spread
underneath it and escape notice for a longunderneath it and escape notice for a long
time until it may become too complicated ortime until it may become too complicated or
too late to save the tooth vitality and pulptoo late to save the tooth vitality and pulp
exposure with bacterial contaminationexposure with bacterial contamination
becomes evident.becomes evident.

19. Caries Recurrence

20. • Control of caries recurrence requires:Control of caries recurrence requires:
Removal of allRemoval of all primary cariousprimary carious enamel andenamel and
dentin.dentin.
Extension of the cavity margins should notExtension of the cavity margins should not
end at anyend at any defected areasdefected areas including pits andincluding pits and
fissures and angular grooves.fissures and angular grooves.
Removal of allRemoval of all week undermined enamelweek undermined enamel andand
short, loose or friable enamel rods.short, loose or friable enamel rods.
Giving theGiving the cavo-surface anglecavo-surface angle thethe correctcorrect
angulationangulation that is compatible with physicalthat is compatible with physical
characteristics of the particular restorativecharacteristics of the particular restorative
material used.material used.

21. Undermined EnamelUndermined Enamel

22. • All other knownAll other known preventive measurespreventive measures
including, potentincluding, potent oral hygiene motivation,oral hygiene motivation,
topical application oftopical application of fluorides, antibacterialfluorides, antibacterial
andand remineralizing agentsremineralizing agents should be alsoshould be also
maintained.maintained.

23. III.III. Protection of investing tissues and adjacentProtection of investing tissues and adjacent
tooth:tooth:
This is achieved by:This is achieved by:
 Rounding andRounding and smootheningsmoothening ragged cavityragged cavity
margins, especially those adjacent to themargins, especially those adjacent to the
gingiva.gingiva.
 Excision of the infectious lesions, andExcision of the infectious lesions, and
elimination of defectselimination of defects which encouragewhich encourage
plaque retention.plaque retention.

24.  Avoid injudiciousAvoid injudicious subgingival extensionssubgingival extensions
whenever possible.whenever possible.
 Protect adjacent toothProtect adjacent tooth surface duringsurface during
proximal tooth preparation by insertion ofproximal tooth preparation by insertion of
steel bands.steel bands.
 ProperProper guide and supportguide and support for hand and rotaryfor hand and rotary
instruments to avoid slippage of instrumentsinstruments to avoid slippage of instruments
and injury to the gingiva and periodontium.and injury to the gingiva and periodontium.

25. B.B. Mechanical fundamentals:Mechanical fundamentals:
These principles areThese principles are primarily concernedprimarily concerned
with:with:
 Preservation of thePreservation of the structural integritystructural integrity of bothof both
the tooth and restoration (Provision ofthe tooth and restoration (Provision of correctcorrect
resistanceresistance form against fracture).form against fracture).
 Retaining the restorationRetaining the restoration inside itsinside its
corresponding preparation (Provision ofcorresponding preparation (Provision of
adequate retentionadequate retention against dislodgement).against dislodgement).
This can be achieved through a correctThis can be achieved through a correct
mechanical cavity design andmechanical cavity design and maximummaximum
conservation of tooth structure.conservation of tooth structure.

26. C.C. Esthetic fundamentals:Esthetic fundamentals:
This includes:This includes:
 Provision ofProvision of symmetrical cavity outlinessymmetrical cavity outlines withwith
refined margins, and smooth sweeping curves.refined margins, and smooth sweeping curves.
The margins must be eitherThe margins must be either concealedconcealed or placedor placed
parallelparallel to respective tooth contours andto respective tooth contours and
anatomic landmarks. Margins must be free ofanatomic landmarks. Margins must be free of
opaque, discolored or pitted enamel.opaque, discolored or pitted enamel.

27.  Limiting area-displayLimiting area-display of restorations throughof restorations through
using conservative designs with minimum lateralusing conservative designs with minimum lateral
extensions.extensions.
 Elimination ofElimination of discolored enamel or dentin.discolored enamel or dentin.
When using esthetic tooth-colored restorations,When using esthetic tooth-colored restorations,
hard discolored dentin may preferably behard discolored dentin may preferably be
masked with opaquers.masked with opaquers.

28. • Conservative approach in operative dentistry:Conservative approach in operative dentistry:
G.V. Black,G.V. Black, in 1891, proposed his pioneerin 1891, proposed his pioneer
work for an organized and systematized cavitywork for an organized and systematized cavity
preparation procedure according to soundpreparation procedure according to sound
biological, mechanical and esthetic fundamentalsbiological, mechanical and esthetic fundamentals
based on the information and technologicalbased on the information and technological
capabilities available at the end of the 19thcapabilities available at the end of the 19th
century. Since that time, acceleratingcentury. Since that time, accelerating
technological advances and changes in treatmenttechnological advances and changes in treatment
concepts demanded a mandatory evolution of theconcepts demanded a mandatory evolution of the
basic fundamentals of the traditional concepts ofbasic fundamentals of the traditional concepts of
cavity preparation.cavity preparation.

29. • The concept of conservation in dentistry refersThe concept of conservation in dentistry refers
toto all procedures carried out to preserve theall procedures carried out to preserve the
integrity of teeth and the masticatory system.integrity of teeth and the masticatory system.
Conservative operative dentistry involves allConservative operative dentistry involves all
the measures of prevention, diagnosis,the measures of prevention, diagnosis,
treatment and follow-up methods which aretreatment and follow-up methods which are
performed to preserve the teeth integrity andperformed to preserve the teeth integrity and
functions.functions.

30. • Historical review of the conservativeHistorical review of the conservative
approach:approach:
In 1891,In 1891, BlackBlack believed that there are areas inbelieved that there are areas in
the tooth structure that are less susceptible tothe tooth structure that are less susceptible to
decay. These areas include the outer 2/3 of cuspdecay. These areas include the outer 2/3 of cusp
slopes, tooth axial line angles, above the buccalslopes, tooth axial line angles, above the buccal
and lingual height of contour and the embrasures.and lingual height of contour and the embrasures.
He advocated that all cavity margins should beHe advocated that all cavity margins should be
extended to these self-immune areas. Thisextended to these self-immune areas. This
concept was known asconcept was known as "Extension for prevention""Extension for prevention"
oror "Cutting for immunity" ."Cutting for immunity" .

31. • However, in contrast to what is thought by mostHowever, in contrast to what is thought by most
clinicians, the concept of conservation of theclinicians, the concept of conservation of the
tooth structure during cavity preparation goestooth structure during cavity preparation goes
back a long way. In 1901,back a long way. In 1901, OttolenguiOttolengui stated thatstated that
"the tooth had no immune areas and since the"the tooth had no immune areas and since the
patient could not be guaranteed that decay wouldpatient could not be guaranteed that decay would
never attack any part of the filled surfaces of thenever attack any part of the filled surfaces of the
tooth, the dentist had no right to remove toothtooth, the dentist had no right to remove tooth
structure and to replace it with a foreignstructure and to replace it with a foreign
material".material".

32. • In 1928,In 1928, PrimePrime proposed a very conservativeproposed a very conservative
and retentive cavity preparation of Class IIand retentive cavity preparation of Class II
restorations. Since that time, scientists andrestorations. Since that time, scientists and
researchers paid considerable attention to theresearchers paid considerable attention to the
conservative approach in repairing damagedconservative approach in repairing damaged
tooth structure even with the limited tools andtooth structure even with the limited tools and
equipments at that time.equipments at that time.

33. • In 1951,In 1951, MarkleyMarkley presented severalpresented several
modifications for Class II cavity preparationsmodifications for Class II cavity preparations
of amalgam restorations which includedof amalgam restorations which included
constricted occlusal outline, proximal retentiveconstricted occlusal outline, proximal retentive
grooves just within the dentin, proximal wallsgrooves just within the dentin, proximal walls
extending only far enough for access, beveledextending only far enough for access, beveled
axio-pulpal line angle to reduce the stresses ataxio-pulpal line angle to reduce the stresses at
the isthmus portion and rounded internal linethe isthmus portion and rounded internal line
angles.angles. MarkleyMarkley advocated the “advocated the “extension forextension for
convenience”convenience” concept rather than “extensionconcept rather than “extension
for prevention” .for prevention” .

34. Extension for AccessExtension for Access

35. • The evolutionary breakthroughs associated withThe evolutionary breakthroughs associated with
clinician's understanding of the caries process,clinician's understanding of the caries process,
rate of speed at which the caries processrate of speed at which the caries process
progresses, remineralization-demineralizationprogresses, remineralization-demineralization
cycles, enamel etching techniquecycles, enamel etching technique (Buonocore,(Buonocore,
1955),1955), development of tooth colored and bondeddevelopment of tooth colored and bonded
restorations; these developments had led to therestorations; these developments had led to the
creation of tooth conservation orcreation of tooth conservation or minimallyminimally
invasive dentistry.invasive dentistry.

36. • In light of this,In light of this, preventionprevention is the theme appliedis the theme applied
nowadays in operative dentistry rather thannowadays in operative dentistry rather than
extension.extension. The concept ofThe concept of "Sealing for"Sealing for
prevention";prevention"; e.g. using pit and fissure sealants,e.g. using pit and fissure sealants,
have arisen. In addition, preventive measureshave arisen. In addition, preventive measures
became more emphasized in operative treatmentbecame more emphasized in operative treatment
and Black's concept has thus evolved toand Black's concept has thus evolved to
“Extension of prevention”“Extension of prevention” (Loeche,(Loeche, 1982).1982).
However, this coincides withHowever, this coincides with Black'sBlack's
statement: "The day is surely coming when westatement: "The day is surely coming when we
will be engaged in practicing preventive, ratherwill be engaged in practicing preventive, rather
than reparative dentistry".than reparative dentistry".

37. • Advantages of conservative cavity design:Advantages of conservative cavity design:
Preservation of valuable intact healthy toothPreservation of valuable intact healthy tooth
structure.structure.
Decreased irritation of dentin-pulp complexDecreased irritation of dentin-pulp complex
and investing tissues.and investing tissues.
Decreased fractured liability of the tooth and/orDecreased fractured liability of the tooth and/or
the restorations.the restorations.
Decreased displayed area of the restorations.Decreased displayed area of the restorations.
Easier, quicker and standardized operative andEasier, quicker and standardized operative and
restorative procedures.restorative procedures.

38. • Steps of Cavity Preparation:Steps of Cavity Preparation:
According toAccording to Black,Black, the procedure of cavitythe procedure of cavity
preparation is outlined inpreparation is outlined in six steps based onsix steps based on
biological, mechanical and estheticbiological, mechanical and esthetic
fundamentals.fundamentals. This enables systematization andThis enables systematization and
standardization of these procedures so that eachstandardization of these procedures so that each
step will be completed perfectly and consistently,step will be completed perfectly and consistently,
thus successful results will be obtained. Thesethus successful results will be obtained. These
steps will be discussed in light of thesteps will be discussed in light of the
evolutionary concepts and current materials andevolutionary concepts and current materials and
techniques.techniques.

39. • These six cardinal steps are:These six cardinal steps are:
1.1. Obtaining of the outline form.Obtaining of the outline form.
2.2. Obtaining of the resistance and retentionObtaining of the resistance and retention
forms.forms.
3.3. Obtaining of the required convenience form.Obtaining of the required convenience form.
4.4. Removal of the remaining carious dentin.Removal of the remaining carious dentin.
5.5. Finishing of the cavity walls and margins.Finishing of the cavity walls and margins.
6.6. Performing the toilet of the cavity.Performing the toilet of the cavity.

40. • There are occasions, however, where it mayThere are occasions, however, where it may
become necessary to overlap some of these steps,become necessary to overlap some of these steps,
as in case of deep carious lesions, where step 4as in case of deep carious lesions, where step 4
mustmust precedeprecede step 2. There is no particularlystep 2. There is no particularly
more important step over the others, however, themore important step over the others, however, the
removal of caries per se is considered a sort ofremoval of caries per se is considered a sort of
arrest to spread of the carious lesion and is thus aarrest to spread of the carious lesion and is thus a
cornerstone for successful restorations.cornerstone for successful restorations.

41. 1.1. Obtaining of the Outline Form:Obtaining of the Outline Form:
 An outline form refers toAn outline form refers to the shape ofthe shape of
boundaries of the completed cavity.boundaries of the completed cavity.
 TheThe externalexternal outline form of the cavityoutline form of the cavity
describesdescribes the marginal boundariesthe marginal boundaries whilewhile
thethe internalinternal outline describes theoutline describes the shape of theshape of the
internal forminternal form of the preparation. Inof the preparation. In
general, thegeneral, the aimaim is to place the margins ofis to place the margins of
cavities in sound enamel at areas whichcavities in sound enamel at areas which
are not carious or defected and less stress-are not carious or defected and less stress-
bearing.bearing.

43. • General Factors affecting the outline form:General Factors affecting the outline form:
The following are factors which should beThe following are factors which should be
considered in deciding on the correct outlineconsidered in deciding on the correct outline
form for different cavity preparations. However,form for different cavity preparations. However,
conditions may arise where it may be necessaryconditions may arise where it may be necessary
to violate some of these cardinal principals.to violate some of these cardinal principals.
These factors are:These factors are:

44. 1)1) Extension of the carious defect in enamel andExtension of the carious defect in enamel and
its lateral spread in dentin:its lateral spread in dentin: Some principalsSome principals
should be considered during caries removal.should be considered during caries removal.
TheThe accessaccess or starting point of the preparationor starting point of the preparation
must be initiated at area nearest to themust be initiated at area nearest to the
pathology.pathology. All carious enamel and dentin mustAll carious enamel and dentin must
be includedbe included in the outline, with consideration toin the outline, with consideration to
the lateral spread of decay at the dentin-enamelthe lateral spread of decay at the dentin-enamel
junction.junction.

45. 2)2) Defective, non remineralizable and retentiveDefective, non remineralizable and retentive
enamel,enamel, such as pits, fissures and angularsuch as pits, fissures and angular
grooves which aregrooves which are deeper than one thirddeeper than one third thethe
enamel thickness and areenamel thickness and are continuouscontinuous with cavitywith cavity
outline should be included in the outline sinceoutline should be included in the outline since
they are retentive for food and therefore, arethey are retentive for food and therefore, are
quite liable to caries when the restoration-toothquite liable to caries when the restoration-tooth
interface is located there. Furthermore, theinterface is located there. Furthermore, the
enamel at these locations is not smooth and thusenamel at these locations is not smooth and thus
will prevent securing of adequate adaptationwill prevent securing of adequate adaptation
with restoration at the critical interface.with restoration at the critical interface.

46. 3)3) To achieve conservative approach:To achieve conservative approach:
Supplementary fissuresSupplementary fissures are preferablyare preferably
considered forconsidered for enameloplasty, slantingenameloplasty, slanting oror
fissure sealingfissure sealing if they are non-carious or ifif they are non-carious or if
they are carious but the caries does notthey are carious but the caries does not
extend more than of theextend more than of the outer two thirdouter two third ofof
enamel thickness.enamel thickness.

47. • Enameloplasty:Enameloplasty: The procedure is simplyThe procedure is simply
reshapingreshaping of the fissures and angular grooves toof the fissures and angular grooves to
make them non-retentive and less prone tomake them non-retentive and less prone to
caries. It is indicated as acaries. It is indicated as a preventive method,preventive method, forfor
treatment oftreatment of early carious lesionsearly carious lesions involving theinvolving the
outer third of enamelouter third of enamel and forand for supplementarysupplementary
fissuresfissures which approximates the outline of awhich approximates the outline of a
cavity preparation. The technique is performedcavity preparation. The technique is performed
using with the side of flame shape diamondusing with the side of flame shape diamond
stone, leaving a smooth surface.stone, leaving a smooth surface.

49. • Note that the cavosurface angle should notNote that the cavosurface angle should not
exceed 100 degrees and that the restorativeexceed 100 degrees and that the restorative
angle should not be less than 80 degrees. Duringangle should not be less than 80 degrees. During
carving, brittle restorative materials should becarving, brittle restorative materials should be
removed from areas of enameloplasty otherwise;removed from areas of enameloplasty otherwise;
thin edged restorations left at this areas will bethin edged restorations left at this areas will be
prone to fracture.prone to fracture.

50. • Slanting bur techniqueSlanting bur technique is done to includeis done to include
supplementary or defective fissures thatsupplementary or defective fissures that
approximate the outline of the cavityapproximate the outline of the cavity
preparation in a conservative way. The fissurepreparation in a conservative way. The fissure
bur is placed on the wall of the preparation andbur is placed on the wall of the preparation and
slanted or tilted to 110° to include the fissure.slanted or tilted to 110° to include the fissure.
The prepared area is usually included in theThe prepared area is usually included in the
restoration.restoration.

51. • PitPit && Fissure sealing:Fissure sealing: It is primarily indicated inIt is primarily indicated in
case of deep angular grooves liable to stagnationcase of deep angular grooves liable to stagnation
and difficult to clean as in recently eruptedand difficult to clean as in recently erupted
permanent molars. In cavity preparations, it ispermanent molars. In cavity preparations, it is
used in conjunction with restorations whereused in conjunction with restorations where
sealing of the fissures provides a conservativesealing of the fissures provides a conservative
choice instead of including them into thechoice instead of including them into the
preparation. The latter procedure is termedpreparation. The latter procedure is termed
Preventive Resin Restoration (PRR)Preventive Resin Restoration (PRR) and is usedand is used
with resin composite restorations where thewith resin composite restorations where the
resinous sealer will chemically bond to theresinous sealer will chemically bond to the
restoration.restoration.

53. 4)4) All enamel which is weak or undermined byAll enamel which is weak or undermined by
caries must be eliminated.caries must be eliminated. If such enamel is leftIf such enamel is left
at a cavity margin, it will break easily underat a cavity margin, it will break easily under
mastication forces leaving amastication forces leaving a "marginal ditch""marginal ditch"
since it is brittle and depends on the relativesince it is brittle and depends on the relative
elasticity of the sound dentin for support.elasticity of the sound dentin for support.

54. 5)5) Adjacent cavities, closely approaching to eachAdjacent cavities, closely approaching to each
other, should not be joined into a single cavityother, should not be joined into a single cavity
unless if the intervening enamel isunless if the intervening enamel is carious,carious,
underminedundermined oror weakweak (less than 0.5mm).(less than 0.5mm).
Separate spot preparations are preferableSeparate spot preparations are preferable
because this preserves the structural continuitybecause this preserves the structural continuity
and strength of the tooth. This should beand strength of the tooth. This should be
especially considered withespecially considered with oblique andoblique and
transverse ridgestransverse ridges because they effectivelybecause they effectively
reinforce the tooth against splitting byreinforce the tooth against splitting by
excursive lateral forces of mastication.excursive lateral forces of mastication.

55. • They strongly cross-tie the two halves of theThey strongly cross-tie the two halves of the
crown. The same concept applies ifcrown. The same concept applies if two surfacestwo surfaces
of the same toothof the same tooth are involved, e.g. cariesare involved, e.g. caries
occurring in occlusal fissures and in buccal pit inoccurring in occlusal fissures and in buccal pit in
lower molars. In such case, each lesion shouldlower molars. In such case, each lesion should
be treated in a separate simple cavitybe treated in a separate simple cavity
preparation. They are not connected into onepreparation. They are not connected into one
compound OB cavity, unless the interveningcompound OB cavity, unless the intervening
tooth structure istooth structure is carious, undermined, weakcarious, undermined, weak oror
crossed by a deep fissurecrossed by a deep fissure (more than 2/3 the(more than 2/3 the
thickness of enamel).thickness of enamel).

56. 6)6) Cusps and ridges that areCusps and ridges that are severely weakenedseverely weakened
and subjected to occlusal forces must beand subjected to occlusal forces must be
reduced and restored with appropriatereduced and restored with appropriate
restorationrestoration (cusp capping)(cusp capping). Extension from. Extension from
the primary groove 1/2 or more of cuspthe primary groove 1/2 or more of cusp
incline indicates cusp capping.incline indicates cusp capping.

58. 7)7) The outline form must be in the form ofThe outline form must be in the form of
harmoniousharmonious sweeping curvessweeping curves in order toin order to
avoid stress concentration and provide betteravoid stress concentration and provide better
esthetic.esthetic.

60. 8)8) The pulp should be protected against,The pulp should be protected against,
inadvertent cutting of dentin, thermo-genesis,inadvertent cutting of dentin, thermo-genesis,
pressure and desiccation.pressure and desiccation. DepthDepth penetrationpenetration
into dentin should be kept to a minimum (0.2 tointo dentin should be kept to a minimum (0.2 to
0.8mm) dictated by the strength requirements,0.8mm) dictated by the strength requirements,
establishment of retention or removal ofestablishment of retention or removal of
carious tissues.carious tissues.
9)9) TheThe cave-surface anglecave-surface angle should be givenshould be given correctcorrect
angulationangulation according to physical properties ofaccording to physical properties of
the restorative material. Moreover, it should bethe restorative material. Moreover, it should be
located in sound dentin areas that are less liablelocated in sound dentin areas that are less liable
to caries recurrence and less stress bearing.to caries recurrence and less stress bearing.

61. 10)10) Age considerations;Age considerations; old patients havingold patients having
occlusal attrition with shallow grooves andocclusal attrition with shallow grooves and
broader proximal contacts are expected tobroader proximal contacts are expected to
have different outline forms.have different outline forms.
11)11) Other factors generally influence the outlineOther factors generally influence the outline
form includingform including oral hygieneoral hygiene andand cariescaries
susceptibilitysusceptibility as well as theas well as the esthetic versusesthetic versus
mechanical demands.mechanical demands.

62. • It is important to note that some modificationIt is important to note that some modification
could be applied to the classical outline ofcould be applied to the classical outline of
different cavity designs for sake of conservation,different cavity designs for sake of conservation,
esthetics and convenience approaches.esthetics and convenience approaches.

63. Thank YouThank You