The document discusses several biological considerations for fixed dental restorations. It notes that teeth and surrounding tissues like dentin, pulp, gingiva and periodontium form a vital unit. Restorations must balance occlusal forces to avoid premature failure or damage to supporting tissues. Tooth preparation aims to avoid damage to adjacent teeth, soft tissues and pulp. Factors like preparation depth, patient age, use of water cooling and cleaning can impact pulpal response. Restorations must also seal well to prevent irritation from microleakage of bacteria or chemicals.

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BiologicalBiological
considerations of Fixedconsiderations of Fixed
RestorationsRestorations

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Vital tissues:Vital tissues:
 DentineDentine contains cells projecting into thecontains cells projecting into the pulppulp
so that they maybe considered asso that they maybe considered as
ONEONE vital unit.vital unit.
 GingivalGingival && periodontal tissuesperiodontal tissues are also vitalare also vital
tissues, which respond to any insult directed attissues, which respond to any insult directed at
them.them.

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Balance of Occlusal Forces:Balance of Occlusal Forces:
 Each tooth is in a state of dynamic equilibrium with itsEach tooth is in a state of dynamic equilibrium with its
neighboring and opposing teeth.neighboring and opposing teeth.
 Occlusal forces acting on a restoration may result inOcclusal forces acting on a restoration may result in
destructive forces, which might shorten its life or causedestructive forces, which might shorten its life or cause
its early failure and that of its supporting periodontiumits early failure and that of its supporting periodontium
along with the T.M.J.along with the T.M.J.

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Fixed Fixed FPD
Fixed Free P.D.

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Oral Environment:Oral Environment:
 Teeth are suspended in the maxilla and mandibleTeeth are suspended in the maxilla and mandible
surrounded by vital structures and bathed in salivasurrounded by vital structures and bathed in saliva
and oral fluids .and oral fluids .
 The oral environment :The oral environment :
1.1. contains microorganismscontains microorganisms (Bacteria)(Bacteria) && chemicalschemicals
produced by foods and its partial digestion.produced by foods and its partial digestion.
2.2. subject to extremesubject to extreme thermalthermal changes.changes.
 Thus, every effort should be done to seal restorationsThus, every effort should be done to seal restorations
in the mouth andin the mouth and minimize microleakageminimize microleakage at theat the
margins.margins.

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Irritation maybe developed fromIrritation maybe developed from
 Tooth reduction,Tooth reduction,
 Restorative materials,Restorative materials,
 Chemicals, andChemicals, and
 Bacteria.Bacteria.

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I. Effects of tooth ReductionI. Effects of tooth Reduction::
(dentine-pulp-gingiva)(dentine-pulp-gingiva)
1.1. Effect of Preparation DepthEffect of Preparation Depth
2.2. Patient agePatient age
3.3. Dry versus wet cuttingDry versus wet cutting
4.4. Cleansing of tooth preparationCleansing of tooth preparation
5.5. Dentinal pain versus pulpal painDentinal pain versus pulpal pain
6.6. Effects of clamps and rubber dam applicationEffects of clamps and rubber dam application

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1.1. Effects of tooth Reduction:Effects of tooth Reduction:
(dentine-pulp-gingiva)(dentine-pulp-gingiva)
avoid damage to
1. adjacent teeth,
2. soft tissues and
3. pulpal tissues.

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Teeth are 1.5-2mm wider occlusally than cervically .
A thin tapered diamond can be passed through the contact leaving
a thin shell of enamel without causing unnecessary injury.
1. Damage to adjacent teeth can be avoided by :
placing metal matrix bands around them when opening contacts.

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 Pulpal response is proportional to the thickness of
the remaining dentine bridge .
Avoid unnecessary tooth cutting by:
1. Use partial veneers instead of complete
veneers whenever possible.
2. Reductions should have minimum taper.
3. Follow anatomic occlusal reductions.
4. Conservative margin designs should be
chosen whenever possible.

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2. Soft tissue protection2. Soft tissue protection
 RetractionRetraction
3. Pulp :3. Pulp :
Causes of injuryCauses of injury
 TemperatureTemperature
 Chemical action:Chemical action:
 Bacterial actionBacterial action
Mirror protecting the tongue

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1.1. Effect of preparation depth:Effect of preparation depth:
 Superficial tooth reductionSuperficial tooth reduction as in full veneer reductionas in full veneer reduction
causescauses reversible damagereversible damage to the pulp.to the pulp.
 Reduction along the D.E.JReduction along the D.E.J. causes. causes intense painintense pain,,
which decreases in intensity once past the D.E.J.which decreases in intensity once past the D.E.J.
 ReductionsReductions within 50µm of the pulpwithin 50µm of the pulp are as harmful asare as harmful as
bloodless exposures.bloodless exposures.

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 Precautions duringPrecautions during retainer selectionretainer selection
 DeepDeep proximal preparationsproximal preparations as in inlay preparations cause moreas in inlay preparations cause more
destructions to the pulp than standard reductions.destructions to the pulp than standard reductions.
 Similarly,Similarly, metal-ceramic restorationsmetal-ceramic restorations cut deeply close to thecut deeply close to the
pulp to accommodate enough bulk.pulp to accommodate enough bulk.
Gingival margins are the most susceptible toGingival margins are the most susceptible to leakageleakage and requireand require
protection all through, during and after insertion of the finalprotection all through, during and after insertion of the final
restorations.restorations.
 Margins, which allow leakage, hinder pulp recovery.Margins, which allow leakage, hinder pulp recovery.

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2.Patient age2.Patient age Pulp recedes with age.Pulp recedes with age.
Central for Metal
ceramic reduction
Lateral for Metal ceramic
reduction
Pinledge
More
occlusocervical
recession than
mesiodistal

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3.Dry versus wet cutting:3.Dry versus wet cutting:
 HeatHeat is generated during cutting byis generated during cutting by frictionfriction between the rotarybetween the rotary
instrument and the tooth surface.instrument and the tooth surface.
 ExcessiveExcessive pressure, speed, type and shapepressure, speed, type and shape of instrument increasesof instrument increases
heat generation.heat generation.
Effect of dry cutting:Effect of dry cutting:
Dry cutting causes theDry cutting causes the odontoblastsodontoblasts to beto be aspiratedaspirated into the tubule.into the tubule.
Excessive dehydration (desiccation) results in :Excessive dehydration (desiccation) results in :
•flow of liquid from the pulpal end into the dentinal floor.flow of liquid from the pulpal end into the dentinal floor.
•pain is felt until the nucleus returns to its original position within 2-3 dayspain is felt until the nucleus returns to its original position within 2-3 days

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Pulpal temperature rise during tooth preparation
Group 1: Water cooled air turbine
Group 2: dry air turbine
Group 3: Water cooled low speed.
Group 4: Dry low speed
Water cooled air turbine

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Reduction should be done usingReduction should be done using
 high speed handpiecehigh speed handpiece
 in feather light strokesin feather light strokes
 with water coolant directed at the contact of the instrument & tooth.with water coolant directed at the contact of the instrument & tooth.
 This prevents heat generation, dentine desiccation & clogging whichThis prevents heat generation, dentine desiccation & clogging which
reduces cutting efficiency of the rotary instrument.reduces cutting efficiency of the rotary instrument.
 Intermittent cutting is better than rapid cuttingIntermittent cutting is better than rapid cutting
 Air coolant with high speed is insufficient and may damage the pulp.Air coolant with high speed is insufficient and may damage the pulp.
 To prevent heat build up retention features such as grooves, should beTo prevent heat build up retention features such as grooves, should be
prepared at low speeds.prepared at low speeds.

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4.Cleansing of tooth preparation4.Cleansing of tooth preparation
Cutting tooth structure results in the production of tooth debris,Cutting tooth structure results in the production of tooth debris,
which varies in particle size between 0.5-20 µm.which varies in particle size between 0.5-20 µm.
Those cling to the dentinal surface and prevent cements fromThose cling to the dentinal surface and prevent cements from
adhering to dentine.adhering to dentine.
Flushing the preparation withFlushing the preparation with warm waterwarm water && moistened cottonmoistened cotton
pellets removes particles of large size.(15-20µm).pellets removes particles of large size.(15-20µm).
Chemical agentsChemical agents maybe used but they cause pulp irritation.maybe used but they cause pulp irritation.
WhileWhile acidsacids,, may remove smaller adherent particles (2-5µm), butmay remove smaller adherent particles (2-5µm), but
softeningsoftening of dentine may result increasing itsof dentine may result increasing its permeabilitypermeability..
UsingUsing 3% peroxide3% peroxide is safer as it is compatible with living tissues andis safer as it is compatible with living tissues and
removes even the smallest particles due to its effervescent action.removes even the smallest particles due to its effervescent action.

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5.Dentinal pain versus pulpal pain5.Dentinal pain versus pulpal pain
The thickness of the remaining dentine is proportional to the pulpal response.The thickness of the remaining dentine is proportional to the pulpal response.
Dentinal Pain Pulpal pain
Nature of Pain Sharp
lancinating pain
Dull
throbbing pain
Location Easily localized Diffuse
Inducing
stimulus
Touch
Acid
Dehydration
Cold
(change in temperature
& osmotic pressure)
Pain is increased during sleep
due to increased venous return
Heat or pressure
Cold relieves pain
Origin Nerve fibers around odontoblasts Nerve fibers around arteries
Cold Induces pain Relieves pain
Trigger Acetylcholine Inflammatory exudates
Pathway of
conduction
Conducted along
small mylinated fibers in nerve trunk
Conducted along
large unmylinated fibers

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A.. deJ. No 20,000 small in
diameter
B . Midway Higher No. larger
diameter
C . Pulp Dense 50,000 Largest
diameter

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6.Effects of clamps and rubber dam6.Effects of clamps and rubber dam
applicationapplication
 Caution must be exercised during clampCaution must be exercised during clamp
application to avoid cementum injury andapplication to avoid cementum injury and
gingival laceration.gingival laceration.
AvoidAvoid
 forceful tissue retractionforceful tissue retraction
 matrix band andmatrix band and
 wedge insertion.wedge insertion.

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II. Split and Cracked teeth:II. Split and Cracked teeth:
A. Enamel Cracks:A. Enamel Cracks:
WithWith advancing ageadvancing age, enamel cracks in anterior teeth and incisal chipping are, enamel cracks in anterior teeth and incisal chipping are
common.common.
Cracks reaching the D.E.J. maybe painful before being filled out withCracks reaching the D.E.J. maybe painful before being filled out with
salivary debris.salivary debris.
Diagnosis:Diagnosis:
Cracks maybe visualized by applyingCracks maybe visualized by applying a dyea dye such assuch as toluidine blue ortoluidine blue or
erythrosine.erythrosine.
Cause:Cause:
They areThey are caused by blowscaused by blows,,
biting on nuts andbiting on nuts and
extreme temperatures.extreme temperatures.
Treatment:Treatment:
4-8% topical stannous fluoride hastens crack filling in young teeth.4-8% topical stannous fluoride hastens crack filling in young teeth.

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Biting on hard objects ex nut cracking
Enamel cracks and incisal chipping with age

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B. Dentine crazing :B. Dentine crazing :
 Dentine isDentine is more elastic than enamel due to its highermore elastic than enamel due to its higher
organic content (35%).organic content (35%).
 Dentine crazing is the occurrence ofDentine crazing is the occurrence of
fine hair like multiple separationsfine hair like multiple separations ..
Cause:Cause:
a result of excessive internal strains exa result of excessive internal strains ex
 exaggerated use ofexaggerated use of pins,pins, oror
 excessive use of force duringexcessive use of force during postpost placement.placement.

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C. Cusp Fracture:C. Cusp Fracture:
Cusps adjacent to wide metallic fillings may suddenly crack and splitCusps adjacent to wide metallic fillings may suddenly crack and split
during chewing.during chewing.
Cause:Cause:
filling expansion, caries or undermining. Inlays may act as wedgesfilling expansion, caries or undermining. Inlays may act as wedges
during cementation especially if the tooth is weak or undermined.during cementation especially if the tooth is weak or undermined.
Weak undermined cusps are better crowned or treated with onlays.Weak undermined cusps are better crowned or treated with onlays.

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D. Split crown and Root:D. Split crown and Root:
WhenWhen deep narrowdeep narrow metallic fillings are placed close to the pulp inmetallic fillings are placed close to the pulp in
premolar teeth withpremolar teeth with high cuspshigh cusps,, excessive forces, such as cracking a nut,excessive forces, such as cracking a nut,
may force the cusps apart and split the crown. The pulp maybe injuredmay force the cusps apart and split the crown. The pulp maybe injured
but the tooth appears intact.but the tooth appears intact.

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DiagnosisDiagnosis::
Sharp intermitant lancinatingSharp intermitant lancinating painpain is felt at the instant of cracking and
later,
on biting and chewing but disappears when elastic dentin closes the crack.
Diagnosis is difficult if the fracture is vertical and therefore not visible
clinically or by x ray.
Detection:
on having the patient bite on a wooden
prop to push the tooth segments
further apart.
Split roots are even more difficult to detect and maybe caused by forceful
insertion of large screw pins.
Sharp pain is experienced upon initiating or releasing chewing pressure.
Pulp tests are normal.

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Treatment:
Split crowns and roots maybe tied together by crowns or onlays ..
 However, reduction may result in further splitting of tooth parts.
Root canal treatment is contraindicated
as it may
 increase splitting and pushing
 the tooth fragments further apart.
 Patients suffering from undiagnosed split roots
 over a long period of time often seek their
 extraction to relieve pain.

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Parallel post in a tapered canal may
cause root fracture
Too short Too longShort post increases possibility of root fracture

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III. Effects of Various Restorations:III. Effects of Various Restorations:
1. Amalgam:1. Amalgam:
 Initially there isInitially there is marginal leakagemarginal leakage, which is later, which is later
decreased due to production of corrosion products indecreased due to production of corrosion products in
the oral environment.the oral environment.
 SignificantSignificant thermal conductivity.thermal conductivity.
 HighHigh galvanic actiongalvanic action in the presence of other metals in the oral cavity.in the presence of other metals in the oral cavity.
 CausesCauses staining of tooth substancesstaining of tooth substances due to penetration of tin and Hgdue to penetration of tin and Hg
ions into the tubules.ions into the tubules.
 Amalgam fillings allowAmalgam fillings allow marginal percolationmarginal percolation due to difference indue to difference in
coefficient of thermal expansion between it and the tooth structure.coefficient of thermal expansion between it and the tooth structure.

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Treatment:Treatment:
These effects maybe minimized by using bases and varnishesThese effects maybe minimized by using bases and varnishes
on the walls of cavities.on the walls of cavities.
New alloys reduce corrosion and provide better marginalNew alloys reduce corrosion and provide better marginal
integrity of the restoration.integrity of the restoration.

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2.2. Bases and Liners:Bases and Liners:
 ThoseThose insulate dentine and pulpinsulate dentine and pulp under large metallicunder large metallic
fillings thus minimizing thermal and galvanic shocks.fillings thus minimizing thermal and galvanic shocks.
 They alsoThey also minimize dentinal discolorationminimize dentinal discoloration due to ionicdue to ionic
penetration.penetration.
 InIn shallow cavitiesshallow cavities varnish maybe usedvarnish maybe used
 Deep cavitiesDeep cavities use modified Zinc oxide as it providesuse modified Zinc oxide as it provides
comfort and pulp protection.comfort and pulp protection.
3.Flourides:3.Flourides:
 Provide anticariogenic effect .Provide anticariogenic effect .
 They maybe added to certain restorative materials such asThey maybe added to certain restorative materials such as
Glass Ionomer and resin cements to decrease cariesGlass Ionomer and resin cements to decrease caries
incidence.incidence.

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4.Composite:4.Composite:
Composites are irritant due to theirComposites are irritant due to their residual monomerresidual monomer contentcontent
especially if they are incompletely cured.especially if they are incompletely cured.
IncorrectIncorrect dentine conditioningdentine conditioning andand microleakagmicroleakagee are theare the primeprime
cause of pulpal irritation.cause of pulpal irritation.
5.Castings:5.Castings:
 Au Alloy castingsAu Alloy castings::
Transmit cold and heat rapidly but are ionically neutral.Transmit cold and heat rapidly but are ionically neutral.
CementCement is used to retain these castings.is used to retain these castings.
Initially it seals the margins butInitially it seals the margins but eventually washes outeventually washes out allowingallowing
space, which harbors bacteria and plaque especially in patients withspace, which harbors bacteria and plaque especially in patients with
low oral hygiene measures.low oral hygiene measures.
 However, highly polished Au does not irritate the gingival and allowsHowever, highly polished Au does not irritate the gingival and allows
less plaque retention.less plaque retention.
 Ni-based alloys:Ni-based alloys: May cause allergy in 10-20% of patients.May cause allergy in 10-20% of patients.

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Ni allergyNi allergy

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6. Porcelain:6. Porcelain:
 Glazed porcelain results in the least amount of plaque retention.Glazed porcelain results in the least amount of plaque retention.
However,However, gingival margin openingsgingival margin openings in Jacket crowns are widerin Jacket crowns are wider
than those of Au metal castings and eventually most cements,than those of Au metal castings and eventually most cements,
being soluble, wash out allowing plaque formation.being soluble, wash out allowing plaque formation.
 Also, any intraoral final grinding of porcelain should be followedAlso, any intraoral final grinding of porcelain should be followed
by reglazing if possible or polishing to maintain tissue tolerance.by reglazing if possible or polishing to maintain tissue tolerance.
7.Gold Foil:7.Gold Foil:
 Can be placed in small cavities.Can be placed in small cavities.
 Does not corrode.Does not corrode.
 Retains its high polish in the oral environment.Retains its high polish in the oral environment.
 Au foil restorations allowAu foil restorations allow least microleakageleast microleakage around their margins.around their margins.
Disadvantage:Disadvantage:
 The pulp reacts strongly to the forces of malleting .The pulp reacts strongly to the forces of malleting .

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8.Titanium:8.Titanium:
Most biocompatible, corrosion resistant metalMost biocompatible, corrosion resistant metal
used in fixed prosthodontics due to aused in fixed prosthodontics due to a thin,thin,
tenacious, protective passive surface oxide layertenacious, protective passive surface oxide layer..
This layer maybe affected by excessive use ofThis layer maybe affected by excessive use of
preventive agents in dentistry, prophylacticpreventive agents in dentistry, prophylactic
polishing and topical fluoride.polishing and topical fluoride.

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IV. Effects of Temporary Crowns and Bridges:IV. Effects of Temporary Crowns and Bridges:
Freshly reduced abutments should be protected byFreshly reduced abutments should be protected by
temporary restorations till the delivery of the finaltemporary restorations till the delivery of the final
restorations to protect them against chemical, thermal andrestorations to protect them against chemical, thermal and
mechanical insults. Provisionals are made of chemical ormechanical insults. Provisionals are made of chemical or
laboratory processed methacrylate resins.laboratory processed methacrylate resins.
Direct provisionals resinsDirect provisionals resins are moreare more
harmful than Indirect orharmful than Indirect or
(Laboratory processed resins(Laboratory processed resins)) as they have :as they have :
greater polymerization shrinkage andgreater polymerization shrinkage and
possess free monomers.possess free monomers.
Gingival margins of provisionals lack adaptation allowingGingival margins of provisionals lack adaptation allowing
leakageleakage, which is not reduced by cements., which is not reduced by cements.

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 Mucosa in edentulous areas is also affected by resin pontics due toMucosa in edentulous areas is also affected by resin pontics due to
plaque retention .plaque retention .
 Acrylic temporaries should beAcrylic temporaries should be smoothenedsmoothened as much as possible and onlyas much as possible and only
kept forkept for short periodsshort periods of time.of time.
Irregular rough margins lead to
plaque accumulation
Provisionals oftenProvisionals often havehave
• overhanging rough marginsoverhanging rough margins
• lack adaptationlack adaptation
inducing plaque retention and gingivalinducing plaque retention and gingival
inflammation within a few days.inflammation within a few days.

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Mechanical and bacterial irritation induce further gingival irritationMechanical and bacterial irritation induce further gingival irritation
Inflammation disappears only when the provisionals are finally removed.Inflammation disappears only when the provisionals are finally removed.

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Temporary cements:Temporary cements:
 Temporary cements ( non eugenol) should be used asTemporary cements ( non eugenol) should be used as
Conventional cements such as Zinc Phosphate cannot beConventional cements such as Zinc Phosphate cannot be
usedused
 Zinc oxide eugenol also cannot be used as it contains freeZinc oxide eugenol also cannot be used as it contains free
eugenol whicheugenol which
a)a) inhibits polymerization,inhibits polymerization,
b)b) dissolves anddissolves and
c)c) discolors acrylic resins.discolors acrylic resins.
 Sealing freshly cut dentinal tubules with varnish or CaOHSealing freshly cut dentinal tubules with varnish or CaOH22
prior to cementationprior to cementation reduces the damage caused byreduces the damage caused by
leakage.leakage.

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V. Effect of Luting Cements :V. Effect of Luting Cements :
Pain after cementation maybe caused by :Pain after cementation maybe caused by :
 Acidity ex zinc phosphateAcidity ex zinc phosphate
 Over-reductionOver-reduction
 Dry cuttingDry cutting
 Minute exposure.Minute exposure.
1. Zinc Phosphate:1. Zinc Phosphate:
 It is irritant to the pulp as it is acidic at the time of placement. (Ph 2-It is irritant to the pulp as it is acidic at the time of placement. (Ph 2-
3). Gradual rise in Ph occurs within 24 hours.3). Gradual rise in Ph occurs within 24 hours.
 Application of several layers of varnish or bonding agent minimizesApplication of several layers of varnish or bonding agent minimizes
pulpal irritation.pulpal irritation.
 Frozen slab technique accelerates its ph rise.Frozen slab technique accelerates its ph rise.

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2. Zinc Oxide Eugenol2. Zinc Oxide Eugenol ::
 Type 1Type 1 (unmodified) for temporary cementation.(unmodified) for temporary cementation.
 Type 2Type 2 Cement for final cementation or long-termCement for final cementation or long-term
provisional cementation.provisional cementation.
 EBA is added to the liquid-EBA is added to the liquid-
 Alumina is added to the powderAlumina is added to the powder
 Polymer modified ZO & E to increase its hardness.Polymer modified ZO & E to increase its hardness.
Uses:Uses:
 BasesBases
 Provisional restorationsProvisional restorations
 Temporary & permanent retention of restorationsTemporary & permanent retention of restorations

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 It is biocompatible and provides aIt is biocompatible and provides a palliative andpalliative and
sedative effectsedative effect on the pulp.on the pulp.
 It also has anIt also has an excellent initial sealing effectexcellent initial sealing effect, which is, which is
reduced in the long term due to its solubility.reduced in the long term due to its solubility.
 Eugenol hasEugenol has an obtundant and bacteriostatic action.an obtundant and bacteriostatic action.
 Non-eugenol formulasNon-eugenol formulas:: were introduced as Eugenolwere introduced as Eugenol
inhibits polymerization, these formulas are used wheninhibits polymerization, these formulas are used when
bonding is anticipated. They contain an aromatic oilbonding is anticipated. They contain an aromatic oil
and zinc oxide.and zinc oxide.

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3. Zinc Polycarboxylate :3. Zinc Polycarboxylate :
 Shows bond to enamel of 9 Mpa and 3.3 toShows bond to enamel of 9 Mpa and 3.3 to
dentine.dentine.
 Excellent biocompatibility due to:Excellent biocompatibility due to:
 Rapid riseRapid rise in ph. Initially 4.8in ph. Initially 4.8
 Large molecular size of polyacrylic acidLarge molecular size of polyacrylic acid prevents itsprevents its
diffusion through the dentinal tubules.diffusion through the dentinal tubules.

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4.Glass Ionomer Cement :4.Glass Ionomer Cement :
A.A. Conventional :Conventional :
 PowderPowder is calcium fluoroaluminosilicate glass.is calcium fluoroaluminosilicate glass.
 LiquidLiquid is polyacrylic or polymalic acid.is polyacrylic or polymalic acid.
 Non irritantNon irritant due to presence of polyacrylic acid.due to presence of polyacrylic acid.
 BondsBonds chemically to enamel and dentine through an ionicchemically to enamel and dentine through an ionic
exchange with calcium.exchange with calcium.
 Bonding is more effective to a clean surface as the cleansingBonding is more effective to a clean surface as the cleansing
agent removes the smear layer.agent removes the smear layer.
 It isIt is bacteriostaticbacteriostatic during its setting.during its setting.
 Least soluble cement.Least soluble cement.
 Clinical success depends on itsClinical success depends on its early protectionearly protection againstagainst
dehydration and desiccation.dehydration and desiccation.

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B. Resin Modified:Hybrid Ionomer Cements:B. Resin Modified:Hybrid Ionomer Cements:
 Resin component is added such as HEMA or BIS-GMA.Resin component is added such as HEMA or BIS-GMA.
 Insoluble , strong and release fluorides.Insoluble , strong and release fluorides.
 Used for permanent cementation.Used for permanent cementation.
 Differ from composites in that glass particles react with theDiffer from composites in that glass particles react with the
liquid during setting.liquid during setting.
 Cause reduced post cementation sensitivity.Cause reduced post cementation sensitivity.

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5.Resin Luting Cement:5.Resin Luting Cement:
 They maybe chemically cured for use with metallic restorations,They maybe chemically cured for use with metallic restorations,
photocured or dual cured for use under translucent veneers and inlays.photocured or dual cured for use under translucent veneers and inlays.
 Resin cements are insoluble and much stronger than conventionalResin cements are insoluble and much stronger than conventional
cements.cements.

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Conventional Composite resins;Conventional Composite resins;
 Mechanical retention only.Mechanical retention only.
 DoDo not form any chemical bondnot form any chemical bond with the tooth structurewith the tooth structure
and restoration.and restoration.
Adhesive composite resins:Adhesive composite resins:
 Micro-mechanical & Chemical retention through groups thatMicro-mechanical & Chemical retention through groups that
bond to tooth structure, silanated porcelain, composites andbond to tooth structure, silanated porcelain, composites and
oxide layer in metals .oxide layer in metals .
 Both are irritant to the pulp. This irritation may arise fromBoth are irritant to the pulp. This irritation may arise from
marginal leakagemarginal leakage due to polymerization shrinkage.due to polymerization shrinkage.
 Leakage results in bacterial infiltration which causes irritationLeakage results in bacterial infiltration which causes irritation
rather than chemicals.rather than chemicals.

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VI.VI. Gingival Reaction to RestorativeGingival Reaction to Restorative
Procedures:Procedures:
Gingival changes with age:Gingival changes with age:
 On eruption the epithelium is attached to enamel andOn eruption the epithelium is attached to enamel and
gradually with advancing age the epithelial attachmentgradually with advancing age the epithelial attachment
migrates apically deepening the crevice. The area is cleansedmigrates apically deepening the crevice. The area is cleansed
by crevicular fluid.by crevicular fluid.

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Young age
Old age with gingival recession

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2.Termination of gingival margins:2.Termination of gingival margins:
 Various opinions regarding the correct gingival termination ofVarious opinions regarding the correct gingival termination of
restorations exist.restorations exist.
..Supragingival (above the gingival crest)Supragingival (above the gingival crest)
 Is the optimum position of the finish line for the health of the gingiva.Is the optimum position of the finish line for the health of the gingiva.

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SubgingivalSubgingival::
In the past subgingival areas were considered asIn the past subgingival areas were considered as self cleansing areasself cleansing areas andand
called for extension for prevention.called for extension for prevention.
HoweverHowever,, some conditions necessitate subgingival location such as:some conditions necessitate subgingival location such as:
1.1. Caries,Erosion or subgingival restorations.Caries,Erosion or subgingival restorations.
2.2. Esthetics.Esthetics.
3.3. Insufficient retention caused by short occlusogingival height.Insufficient retention caused by short occlusogingival height.
4.4. Root sensitivity.Root sensitivity.
5.5. Cervical position of contact.Cervical position of contact.
However, care must be taken to position theHowever, care must be taken to position the
margin midway in the sulcus between the gingivamargin midway in the sulcus between the gingiva
crest and the depth of the sulcus.crest and the depth of the sulcus.
Iatrogenic tearing of the epithelial attachmenIatrogenic tearing of the epithelial attachment
results in its apical migration and pocketresults in its apical migration and pocket
formation.formation.

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C. At the Crest:C. At the Crest:
Finish lines should never be located at that position as margins areFinish lines should never be located at that position as margins are
always rough :always rough :
inviting food debris and plaque accumulation thus causing decay orinviting food debris and plaque accumulation thus causing decay or
periodontal involvement.periodontal involvement.
Margins should beMargins should be
1.1. smooth,smooth,
2.2. blunt,blunt,
3.3. round andround and
4.4. polishedpolished..
Rough, sharp, porous margins harbor bacteria and plaque thus causingRough, sharp, porous margins harbor bacteria and plaque thus causing
irritation, which paves the way to gingivitis.irritation, which paves the way to gingivitis.

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 3.Gingival Retraction:3.Gingival Retraction:
 Retraction should beRetraction should be as atraumaticas atraumatic as possibleas possible
to expect gingival recovery. Use blunt instrument.to expect gingival recovery. Use blunt instrument.
 However, age also plays a role:However, age also plays a role:
 Young patientsYoung patients:: Recovery from retraction is fast and there is rapid totalRecovery from retraction is fast and there is rapid total
covering of the restoration margins.covering of the restoration margins.
Middle Age:Middle Age: Ischemic gingiva may delay healing with exposure of theIschemic gingiva may delay healing with exposure of the
restoration margins or even the cementum causing cervicalrestoration margins or even the cementum causing cervical
hypersensitivity.hypersensitivity.

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4.Effect of Restorative Materials on the gingival and4.Effect of Restorative Materials on the gingival and
mucosa:mucosa:
Many restorative materials contact the gingiva. They should minimizeMany restorative materials contact the gingiva. They should minimize
plaque retention.plaque retention.
Glazed porcelainGlazed porcelain andand polished gold marginspolished gold margins areare WellWell tolerated by the gingivatolerated by the gingiva
Base metal alloysBase metal alloys containing Ni may provoke allergic reactions in certaincontaining Ni may provoke allergic reactions in certain
patients.patients.
ResinsResins are the least tolerated due to their roughness and plaque retention.are the least tolerated due to their roughness and plaque retention.
This also applies to pontic materials but in that particular case, design alsoThis also applies to pontic materials but in that particular case, design also
plays a significant role.plays a significant role.

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Proper use of dental floss

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Gingival margins should follow the contour of the gingival margins.
Flat Apical margins of the preparation do not follow the gingival contour