JVD 2018 #1 A Review of Dental Cements

Question 1

What are the ideal properties of a dental cements? (10)

Answer 1

• Film thickness: low (better seating of crown, less marginal discrepancies)
• Working time: long (to properly seat the restoration)
• Setting time: short (to set as fast as possible once restoratio seated)
• Compressive strength: high (to resist occlusal strength)
• Elastic modulus: equal to dentin (13.7 MPa)
• Pulp irritation: low
• Solubility: very low (to protect marginal integrity)
• Microleakage: very low (to prevent fluid or bacterial invasion)
• Removal of excess: easy (to remove excess without pulling unset cement under restoration margin)
• Retention: high (for retention of crown by luting agent (nonadhesive), micromechanical, moledular)

Question 2

How is flexural strength determined?

Answer 2

• A 3-point bending or flexural test is performed. The flexural test defines the strength and amount of distortion expected
• Flexural strength is determined by forming the material into a simple beam.
• The beam is supported, not fixed, at each end and a load is then applied to the middle.
• The flexural strength is calculated by the maximum stress applied to materia

Question 3

What is the elastic modulus of a material?

Answer 3

• a number that measures an object or substance’s resistance to being deformed elastically (ie, nonpermanently) when a force is applied to it.
• higher values indicate a ‘stiffer’ material

Question 4

How is the hardness of a material determined?

Answer 4

The hardness of a material is determined by making a symmetrical-shaped indentation with an indenter that has a standardized force or weight.

Question 5

What are the basic composition of the principal dental cements?

• Zinc phosphate (oldest, was the gold std)
• ZOE (high biocompatibility)
• Polycarboxylate (1st to adhere to tooth)
• Glass Ionomer
• RMGI
• Compomer
• Resin-based cements (stongest, least solube, best bonding then all other)
• Self-adhesive resin-based cements

Answer 5

• Zinc phosphate: Zinc oxide + Mg oxide + phosphoric acid + water + buffers
• ZOE: Zinc oxide + eugenol +/- EBA (ethoxybenzoic acid)
• Polycarboxylate: Zinc oxide + polyacrylic acid
• Glass Ionomer: Polycarboxylate (polycarboxylic ac.) + fluoroaluminosilicate glass + water + tartaric acid
• RMGI: Glass ionomer + resin
• Compomer: Composite (resin + glass filler) + glass ionomer
• Resin-based cements: Resin + filler (glass or silica)
• Self-adhesive resin-based cements: don’t know exactly, but resin-based + phosphoric acid-modified methacrylate monomers

Question 6

What are the components of a glass ionomer cement?

Answer 6

• finely ground glass filler and fluoroaluminosilicate (FAS),
• polycarboxylic acid,
• water,
• tartaric acid
  (acts as an accelerator, aids in the extraction of ions from aluminosilicate glass and facilitates their binding to polyanion chains. Post-setting hardening is significantly increased)

Question 7

Which of the following are water-based cements?

• Zinc phosphate
• ZOE
• Polycarboxylate
• Glass Ionomer
• RMGI
• Compomer
• Resin-based cements
• Self-adhesive resin-based cements

Answer 7

• Zinc phosphate
• ZOE
• Polycarboxylate
• Glass Ionomer

are all water-based cements. They have high solubility, lower strenght, greater microleakage and lower bond strength than resin-based cements (= weaker, less durable)

Question 8

Rank the following cements from most to least soluble:

Glass Ionomer, Resin based, Zinc oxide eugenol

Answer 8

ZOE, GI, Resin based:

Water based: Zinc phosphate, polycarboxylate, glass ionomer, zinc oxide eugenol (ZOE), and ethoxybenzoic acid (EBA)-reinforced ZOE cement

Question 9

What is the mode of bond (non-adhesive, molecular, micromechanical) to the tooth for the following cements:

• Zinc Phosphate
• Polycarboxylate
• Glass Ionomer
• RMGI
• Compomer
• Resin based
• Self-adhesive resin-based

Answer 9

Zinc Phosphate - non adhesive (luting agent)

Polycarboxylate - Molercular

Glass Ionomer - Molecular

RMGI - Molecular AND micromechanical

Compomer - Molecular AND micromechanical

Resin based - Micromechanical

Self-adhesive resin-based - Micromechanical

Question 10

Rank the following cements in their bond strength to tooth material from strongest to weakest:

• Zinc Phosphate
• ZOE
• Polycarboxylate
• Glass ionomer
• RMGI
• Resin-based cement
• Self-adhesive resin-based cement

Answer 10

From strongest to weakest bond:

Resin based; Self-adhesive resin-based cement; RMGI; GI; polycarboxylate, ZOE, zinc phosphate

Resin-based cements are the strongest, least soluble, best bonding cements of any of the other choices. They are also more technique sensitive and more expensive.

Question 11

Rank the following cements on strength, durability and cost (same order for all properties):

Resin Based

ZOE

RMGI

GI

Zinc Phosphate

Self-adhesive resin based

Answer 11

From lowest to highest:

ZOE, Zinc Phosphate, GI, RMGI, Self-adhesive resin based, Resin Based