Ormocers (Organically Modified Ceramics)

Question 1

What are ormocers?

Answer 1

Organically modified, non-metallic inorganic compound materials.

Question 2

Describe the ormocer backbone.

Answer 2

• inorganic network formed by polycondensation - backbone based on silicon dioxide, functionalised with polymerisable organic units to produce 3-D compound polymers - silicon dioxide backbone accounts for their relationship with ceramic

Question 3

Describe the behaviour of ormocers?

Answer 3

Hard as glass, behave like acrylic

Question 4

What are polymerisable organic groups & what do they do?

Answer 4

• They are methacrylate groups inserted inot inorganic network; regulate polarity, hardness and optical properties as well as capacity to be cured

Question 5

What are two problems traditional resin matrix (Bis-GMA & UDMA) have?

Answer 5

1. Dimethacrylates only have 2 reactive connection points (double bonds); this means incomplete polymerisation in curing, and residual monomers 2. Small molecules–> relatively high shrinkage; i.e. high tension between tooth substance, bond & composite, may lead to marginal leakage

Question 6

What are two solutions Ormocer matrix offers for the problems experienced by traditional resin matrix?

Answer 6

1. Each ormocer molecule has high number of connection points; resulting in complete polymerisation, no residual monomers 2. Large ormocer molecules guarantee lowest shrinkage due to pre-shaped network; low shrinking, excellent bonding strength, tooth-like thermal expansion behaviour- promotes long-lasting restoration even in load-bearing areas

Question 7

List the 12 features of ormocers

Answer 7

1. Low polymerisation shrinkage (~1.97%); good marginal integrity & decreased secondary caries
2. More completely polymerised–> due to high no. cnxn pts on modified SiO2 network
3. Reduced residual monomer= inc. biocompatibility
4. Good aesthetics
5. Similar Coeff. T. expansion to tooth structure
6. Organically modified ceramic; not equivalent to glass ceramic filler of conventional composites
7. Increase in dentine bond strength if used w/ Ca-complexing bond system
8. Good marginal integrity
9. Inc. flexural strength over nano-filled micro hybrid
10. Good abrasion resistance
11. Similar compressive strength to small particle hybrid
12. Less monomer involved in rxn due to cross linking and chemical structure–> less unreacted monomer resleased