Post on 21-Mar-2020
transcript
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