Glass ionomer cement -most frequently asked viva question along with answers

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                GLASS IONOMER CEMENT :

MOST FRQUENTLY ASKED VIVA QUESTIONS:

1)DEFINE GLASS IONOMER CEMENT?

A cement that consists of basic glass and acid polymer which sets by an acid -base reaction between these components .

2)Who discovered glass ionomer cement?

Wilson and Kent in 1972 

3) Other name of glass ionomer cement ?

ASPA -Alumino silicate polyacryate 




4)Composition:

Powder :

Silica-35-40%

Alumina-20-30%

Calcium fluoride-15-20%

Aluminum fluoride-1.5-2.5%

Aluminium phosphate-9-8%

Sodium fluoride-5%

liquid:

Polyacrylic acid-40-50%

Itaconic acid, malic acid and tartaric acid -5%

Water-45-50%

5)Classification:

A)according to Wilson and Kent:

Type 1- luting cement

Type 2 -restorative 

Type 2 a -Restorative aesthetics

Type 2b- Restorative reinforced

B)According to application:

Type 1 -Luting

Type 2 -Restorative 

Type 2 a -Restorative aesthetics

Type 2b- Restorative reinforced

Type 3-Lining cement

Type4- Fissure cement 

Type 5- Orthodontic  cement

Type 6-Core build cement

Type 7 - Intermediate restoration

Type8- Atraumatic restorative treatment (anterior restoration)

Type 9 - atraumatic restorative treatment (posterior restoration)





General types : 

1.Reinforced

2.Resin modified - 

Improved handling and character 
Less technique sensitive 

3.Compomer

4.Atraumatic restorative treatment 
5.Giomer 


6) Setting Reaction:

Sets via- acid-base reaction

Steps :

1)Decomposition:

The acidic liquid solution (pH=1) dissolve periphery of silicate glass particle releasing calcium, aluminum ,fluoride ,silicon and other ion.

2)MIGRATION:

Calcium ions are chelated quickly by the carboxyl side groups on polyacrylic acid polymer chain 

3)GELATION:

Cross linking by polyacrylic acid chain takes place proceeding as amorphous gel matrix 

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During next 24-72 hours ,the calcium ions are replaced by more slowly reacting aluminium ion to produce a more highly cross linked mechanical stronger 

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During this time ,silicon ion and unbound water produce inorganic co-matrix -hydrated silicate 

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Same carboxyl acid side group are also capable of chelating this 

This process generate true chemical bond at intrinsic and extrinsic interface when reaction condition is correct .

Bonding :

  • Bond to enamel and dentin through ionic interaction 
  • Polyacrylic acid(hydroxyl group)- enamel, dentin 







7)MIXING TIME ,WORKING TIME,SETTING TIME ?

MIXING TIME :45-60SEC

WORKING TIME-2 MINUTE

SETTING TIME - 5-7 MINUTE -TYPE 1

                             10 MINUTE - TYPE 2 

8)COMPRESSIVE STRENGTH,TENSILE STRENGTH ?

COPRESSIVE STRENGTH -60-300MPA

TENSILE STRENGTH GIC TYPE 9 - 12.61MPA

9)Role of water in setting reaction :

  • Reaction medium into which the cement forming cations are leached and transported to react with polyacid to form a matrix 
  • Hydrates siliceous hydrogel and metal polyacrylate salts are formed 
  • loosely bond water - readily removed by desiccation
  • tightly bond water-cannot be removed and is associated with hydration shell of cation (alumina ,silica gel ,water )
  • With aging ,tightly bound water increases ,increases strength where as  modulus of elasticity and plasticity decreases
  • high humidity -absorb water -hygroscopic expansion
  • dry humidity-loss water-shrinking ,crazing 




10)Anhydrous glass ionomer cement?

  • liquid is delivered in freeze dried ,which is incorporated into the powder ,liquid used in clean water 

11)FACTORS affecting setting reaction ?

  1. Glass composition -Increased alumina -silica ratio-increased setting time time
  2. Particle size-fine powder increased setting time
  3. Addition of tartaric acid 
  4. Relative proportion of constituent
  5. Temperature 

12)Sandwich technique?

  • Developed by Mclean ,to combine beneficial property of glass ionomer cement and composite 

Steps:

Step1- Conservative cavity preparation 

Step 2- Dentin conditioning

Step 3- Type 3 glass ionomer cement base 

Step4- After setting etch enamel ,glass ionomer cement with orthophosphoric acid for 15 seconds 

Step5- Micromechanical strength enhances ,then thin layer of low viscosity dentin bonding agent and place composite resin  over glass ionomer cement and light cure it .



13)Dentin conditioning :

  • Done to remove smear layer 
  • GIC has better ability to wet dentin surface 
  • Promotes ion exchange
  • Chemically clean dentin 
  • Increased surface energy 


14)contra-indication of glass ionomer cement :

  • Class4 caries lesion
  • Class 2 caries lesion where conventional cavities are prepared 
  • Lost cusp areas

15)RMGIC INDICATION:

  • Luting cement especially in orthodontics
  • liners,base
  • Pit and fissure sealant 
  • For amalgam repair 


Conclusion:

vanakam my dear stencildent family members hope you liked this post on glass ionomer cement ,as per a dear subscribers request we have started to post dental cements starting with 1st post on zinc-phosphate cement followed by post on zinc polycarboxylate cement if it helped you learn then do let me know in the comment section below .

                                         THANK YOU 

CONTAT DETAILS :

EMAIL : stencildent@gmail.com

Instagram: stencildent 




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