8/3/2019 Dent Mat Lec (Jan 31)

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ENT MAT LEC (Jan 31)

ubricant  Cocoa butter   To avoid dehydration and dryness of dental cement   Application is after setting of dental cement

o  If not, it will appear chalky in appearance  Contraindicated with mouth-breathers

elluloid Strips  Follows the contour of the convexities of the crown of natural teeth

COMPOSITE RESIN  Superior than dental cement  Copies color and appearance of natural tooth  Insoluble to oral fluids  Stronger than dental cement  Resistant to abrasion  Paste form

Acid Etching  Etchant ± acid-etching agent  50% phosphoric acid   Applied only to the walls of enamel   Application: 1 min only  Improves retention and sealing of resin into tooth structure  Less reduction of tooth structure

   Applied in the walls of enamel in the area of fracture  Wash mouth to remove acid (after 1 min)

onding Agent  Improving retention and sealing of composite

ight-Cure Filling Material  Paste  There is no hurry in application  No more base and catalyst  Catalyst ± light cure machine (LED curing light) causes hardening   Applied on fractured area  More time to apply  Less polishing, less reduction  You can do the anatomy of tooth better 

elf-Cured Composite Resin  Hardens by chemical reaction  Base + catalyst

it and Fissure Sealant  Good for growing children and young patients  Minimizes caries formation  Checked after 1-2 years for removal and reapplication  Only applied to posterior teeth (with pits and fissures)  Cannot be applied in smooth surfaces (incisors, buccal surface), occlusal

surfaces only  Without fluoride  If sealed with resin, it lasts longer   If with microleakage, clean and reapply  Part of Preventive Dentistry

AMALGAM

  Metallic restorative material  Combination of alloy and mercury  Not all amalgam are considered a restorative material  Dental Amalgam is a union of:

o  (Ag) Silver ± essential componento  (Sn) Tin ± second major constituento  (Cu) Copper ± third major constituent (15%)o  (Zn) Zinc ± can be present or absent

  (Absent) Zinc-free Alloyo  (Hg) Mercury

  Not dentally used: union of:

o  Zn, Cu, Mn, Hg (?)

Physical Properties  Contributed by the presence of Hg

1.  Dimensional Changea.  Expansionb.  Contraction

2.  Strength3.  Flow and Creep

Flow ± movement of molecules when the substance is in the soft conditionCreep ± movement of molecules when the substance is already set

Contributions to Physical PropertiesSilver Tin Copper Zin

Expansion Increase Decrease Increase P: IncA: Dec

Strength Increase Decrease Increase

Flow & Creep Decrease Increase Decrease* P = if  present  * A = if absent  

Signs of Expansion1.  Post-operative Pain 

   Amalgam ± high thermal conductivity  Needs insulator (apply non-acidic dental cement)

2.  Protrusion of amalgam from cavity   Height of amalgam is not level with tooth structure

3.  Tarnish and Corrosion T arni sh -  Discoloration of metal (change color ± green and brown)

-  Forerunner of corrosionCorrosi on -  Silvery color is changed to black-   Actual deterioration of metal-  Powdery substance; rust

 Amalg am ± hardens by chemical reaction

Factors Affecting Dimensional Change1.  Mercury/Alloy Ratio (M/A Ratio) 

  Hg ± liquid at room temperature; considered as W (as in W/P Ratio)2.  Trituration 

  Mixing procedure of alloy and mercury  Spatulation = 1 min

3.  Condensation (Cond)   Process of plugging/condensing of amalgam in the cavity   Amalgam plugger ± comes in several sizes   Always start with the smallest plugger   Carry the amalgam into the cavity by increments (little by little)  Smallest plugger ± can reach into undercut area   Amalgam ± more retention in an undercut cavity preparation  Filling ± parallelism of cavity preparation

4.  Particle Size 5.  Moisture Contamination (Moisture Cont.) 

FACTOR Expansion Strength Flow & Cr

1. M/A Ratio

HighMore Hg present

More expansion

Weak Greate

Less Less expansion Stronger Less

2. TriturationFast: not affectedSlow: not affected

UT: weakOT: weak 

No reacti

3. Condensation

Inc. Cond. Less expansion Stronger Less

Dec. Cond.Presence of HgMore expansion

Weak Greate

4. Particle Size 

Fine(microcut alloy)

Less HgLess expansion

Stronger Lesser

Big More expansion Weaker  Greate

5. Moisture Cont. 2 TYPES OF EXPANSION  Weak X 

8/3/2019 Dent Mat Lec (Jan 31)

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U T = undertr i t ur at i on (< 1 mi n) -  M ore H g  -  S oa py a ppear ance -  Dull a ppear ance 

OT = overtr i t ur at i on (> 1 mi n) -  Dull a ppear ance 

wo Types of Expansion.  Excessive Expansion 

  Too much mercury  Not condensed well  More painful; apply more insulators

.  Delayed Expansion   Caused by moisture contamination  No microleakage  a.k.a. Secondary expansion  Happens when an almost filled-up cavity of an isolated tooth is wet with

cotton

dd i t i on of H g ± c auses expansi on, greater f low & creep