Dr. samer.d.azrai : BDS(j.u.s.t),JB( cons)

Introduction to restorative

dentistry

Operative dentistry

Its that branch of dentistry concerned with restoration of part of the teeth that are defective through

diseases (caries),trauma, developmental anomalies into the state of normal function and esthetic

Including prevention

Dental caries

• It’s disease characterized by dissolution of non organic component of the tooth and subsequent disintegration of organic component.

• Dynamic process.. Episodes of de-mineralization and re-mineralization occur depending on plaque ph.

Etiology of caries

Stephan curve

Dynamic of caries

Dynamic of caries

Re-min……Re-min

Prevention not restoration

How can we prevent caries

• Bacteria???

• What can we do….

• It’s always there

bacteria

• Tooth brushing

• Regular use of mouth wash containing CHX.

• By Disturbing dental plaque…non pathogenic bacteria faster in occupying tooth surface than pathogenic bacteria (m.striptococcus)

Bacteria….tooth it self

Key word…increase the tooth resistance to caries

• Fluoridation of drinking water…reduced smooth surface caries.

• Tooth brushing and local fluoride application …..re -min by fluoroappitite (more resistant to acid)

Bacteria …. Tooth it self…

• Increasing resistance

• Fissure sealants

Dramatic reduction in caries affecting fissures

Bacteria..tooth…sugar and time

• Frequency more important than quantity

• Brush immediately after eating ..isn’t totally true…acid challenge

• Never gargle after brushing????

Diagnosis of caries

• Rule of thumb…Use a sharp eye not a sharp probe

• Destroying the intact surface by a probe opens the lesion and prevent re-min.

(1) Sharp eye dry tooth

• Incipient (white spot ) lesion disappear if the tooth is wet

(2) Fiber optic

(3) Dye

(4) Radiographs

Classification of dental caries G.V.Black 1908

Restoration when caries win the battle

Restorative material

• Amalgam

• Composite resin

• G.I

• Polyacid modified composite resin (dyract)

• Resin modified G.I (RMGI)

• Giomer

Amalgam

• Dental amalgam is a mixture of mercury with an alloy powder containing (silver (ag) –tin ( sn))

• Following mixing The reaction between mercury and alloy is called amalgamation

Amalgam

• Also contains a small amount of zinc (zn) almost 1% ..works as a scavenger

Zn + H2O → ZnO + H2

• Responsible for delayed expansion of amalgam..(3%-

5%) • Moisture control is mandatory

Crack due to expansion

Contains copper Cu

Low Copper Amalgam

• Ag3Sn + Hg Ag3Sn + Ag2Hg3 + Sn7-8Hg

• Gamma + Mercury Gamma + Gamma-1 + Gamma-2

• -2 also effects strength, creep

and marginal durability

High copper amalgam:

• Second reaction takes place:

• -2 + Ag-Cu Cu6Sn5 + -1

• This improvement has resulted in: – Higher compressive strength

– More rapid set to full strength

– Reduction in creep

– Reduced susceptibility to corrosion

Mechanical properties

• Dimensional change (%) −0.1 to +0.2

• Compressive strength (MPa)

at 1 hour 50 (minimum)

at 24 hours 300 (minimum)

• Creep (%) 3.0 (maximum)

Lath cut (filing)..spherical…mixed

Cavity preparation

- Conservative.. Not to exceed ¼ of the inter cuspal distance.

-Butt joint .. 90° cavo -surface angle.

Rounded pulpo-axial wall

Flat pulpal floor

Pulpal protection..linear and bases

Calcium hydroxide liner

Rules for ca(oH)2 …

• Use applicator

• As small as needed

• Only over pulp

Ca(OH)2…..

Matrix band mandatory for missing walls

Wejdes …mandatory

Advantages of amalgam for restoring posterior teeth

• Less technique sensitive.

• More durable.

• Less costly.

• Time for placement is less.

• Cheaper.

• Excellent wear resistance.

• Self sealing against leakage.

• Surface not as adherent with bacteria.

Composite

• Dental composite is a physical blend between a resin and an inorganic filler

• Resin usually is BIS-GMA or UDMA

• TEGMA… a co-monomer used to reduce the viscosity of resin.

• Filler usually quartz or alumino silicate glass

In organic filler

• Filler content

• Reduces

• polymerization shrinkage

• Reduced LCOE

• Increases strength

Filler size

Classification according to filler content

Bonding to enamel and dentine

• Bonding is the key of success

• Acid etching , primer , adhesive

Wet Vs Dry bonding

Total acid etching

• Etching for 10 – 20 second .. Then washing

Application of primer & bond

Then incremental composite placement

Reducing stress in Composite Restorations

In Three Decades Ago Composite was

•Poor In wear resistance.

•Lacks appropriate proximal contact.

•Exhibited micro leakage & secondary caries.

In the past 10 years

Significant improvement in wear

resistance.

Good proximal contact & contour.

Still……. Polymerization shrinkage ?

Polymerization (curing) shrinkage: Is the formation of a gap between composite &

cavity walls.

Shrinkage values range between 1.2% - 4.5% by volume. ( 0.2% - 1.9% by linear measures)

Effect of shrinkage

Microleakage.. Recurrent caries. Marginal staining

Post operative sensitivity

Methods to reduce polymerization shrinkage

(1) Soft start curing.

when stresses Composite exhibits less shrinkage cured at a low intensity and slow rate of

polymerization.

(2) Incremental Technique

(3) Directional curing

Composite shrinks towards light

•Multiple curing sources . ?

•Through tooth structure.

•Utilizing clear matrix bands & reflective wedges.

(4) Elastic wall concept

Thick adhesive Flowable composite

(5) Configuration factor ( C- factor)

•Ratio between bound – to – un bound surfaces of the restoration.

•As c factor polymerization stresses .

Disadvantages of composite

• Poor In wear resistance.

• Lacks appropriate proximal contact.

• Exhibited micro leakage & secondary caries.

• Post operative sensitivity

• Technique sensitive compared to amalgam

Glass ionomer (G.i)

• In none load areas

• Releases fluoride

• Chemically bond to enamel and dentine

• The closest in COE to tooth structure

• Can be etched and bonded to receive composite ….sandwich technique

Sandwich technique G.I

• Resin modified glass ionomer

80% G.I

Releases fluoride

Light cured

• Polyacid modified composite

• 80% composite

• Claimed to release fluoride

• Light cured

• Used mostly with deciduous teeth

•

Thank you

Dr.Samer.D. Azrai