Dental Cements Flashcards
What is a dental cement?
A dental cement is a substance that hardens to act as a liner, base, restorative material, or luting agent to bind devices and prostheses to tooth structure or to each other.
What characteristics do we want a dental cement to have?
-Needs to be Biocompatible
-Needs to be inert and non-corrosive
-Insoluble to acid attack
-Dimensionally stable (minimal shrink or expansion upon setting)
-Needs to set up quickly
-Has low surface tension (Flows well and handles well)
-Adapts and adheres to anatomy
-Insensitive to moisture during procedure
-Fluoride release
-Anti-microbial
-Radiopaque (can be seen on an x-ray)
-Cost effective
-Low film thickness (<25 micrometers) (an average human hair is 75 micrometers)
-Adequate strength (70 Mpa or above)
-Low Solubility (0.2% maximum at 24hrs)
-Reasonable Setting time (2.5 – 8.0 minutes)
-Adequate working time
-Cariostatic
-Adhesion to tooth structure AND restorative material
What should the film thickness be for a dental cement?
low (<25 micrometers)
What should the strength be of a dental cement?
adequate strength (70 Mpa or above)
What should the solubility be of a dental cement?
low (0.2% maximum at 24 hours)
What should the setting time be of a dental cement?
2.5-8.0 minutes
What is cyclic fatigue?
- the stress, strain, and deformation induced in a material by cyclic loading
- Cyclic fatigue life is the number of loading cycles which produce a rupture or breakage in the material.
You want _____ values for cyclic fatigue for a dental cement
high
You want _____ values for thermal cycling for a dental cement
high
What is a thermal cycle?
- any repetitive thermal test in which the temperature is regularly altered, touching a high-temperature peak and a low-temperature peak
A dental cement in should have a high value of strength in what ways?
-Tensile
-Compressive
-Flexural Strength
-Shear
Where do we use dental cement materials in cements?
- Permanent and Provisional indirect restorations
- Orthodontic brackets
- Cementing Post and Core Build Ups
Where do we use dental cements in restorative materials?
Permanent and Provisional direct restorations
Where do we use dental cements in liners and bases?
Pulp protection in deep cavity excavation
What is adhesive bonding?
This is accomplished through substituting inorganic tooth materials with resin monomers; essentially, minerals in the enamel and/or dentin are replaced by resin monomers. Through polymerization, these become micromechanically interlocked into the resulting porosities. These adhesive bonding procedures can be completed through 2 different approaches: etch-and-rinse and self-etch.
What is cementation?
Cementation uses good prep design and resistance to connect underlying tooth structure with a restoration. Essentially, the cement creates a hard cement layer to adhere to the 2 surfaces. With cementation, no matter how good the cement, it’s critical that there is adequate preparation, including good retention form and resistance.
When choosing a cement, it is important to consider the numerous factors such as…
bond strength, preparation design, restorative material, ability to isolate, and importance of esthetic
Are adhesive bonding and dental cementation the same thing?
NO
What is the bond stength of adhesive bonding?
20-30 MPa
What is the bond stength of dental cement?
1-5 MPa
What does adhesive bonding lock into?
- Etched enamel leaves open the ability for resin to flow in and around the enamel rods creating resin tags
- This also creates a micromechanical interlocking of resin with demineralized collagen of inter-tubular dentin as well
What does the dental cement lock into?
- Locking of cement into microscopic irregularities in prepared tooth surface and irregularities in the internal of the crown
What type of bonds do cements have?
- physical bond
- chemical bond
- mechanical bond
What do physical bonds do in dental cement?
Very weak interactions with Secondary Bonds (ex - Van Der Waals Forces and Hydrogen Bonds)
What do chemical bonds do in dental cement?
Strongest bond with Primary Bonds
(ex – Composite Bond to Adhesive Bond Agent)
What do mechanical bonds do in dental cement?
- Interlocking undercuts, surface irregularities
- Micromechanical retention
What are the six categories of dental cements?
-Zinc Oxide (At UMKC = IRM and TempBond)
-Zinc Phosphate
-Zinc Polycarboxylate (At UMKC = Durelon and UltraTemp)
-Glass Ionomer
-Resin-Modified Glass Ionomer (At UMKC = Rely-X Luting)
-Resin Cements (At UMKC = Variolink or SpeedCem
What is zinc oxide called at UMKC?
IRM and Tempbond
What is zinc polycarboxylate called at UMKC?
Durelon and Ultratemp
What is resin-modified glass ionomer called at UMKC?
Rely-X Luting
What is resin cements called at UMKC?
Variolink and SpeedCem
What is the setting mechanism for zinc oxide, zinc polycarboxylate, zinc phosphate, and glass ionomer?
acid-base
What is the setting mechanism for resin-modified GI?
acid-base
and
polymerization
What is the setting mechanism for resin cement (RC)?
polymerization
Many of the cements we use and have used in the past are _____________ reactions
Acid-Base Reactions
New cements have added ______________ as an aspect of setting to remove the risks and negatives of an acid base cement system.
Polymerization
What are acid-base cements?
- utilize a powder and liquid combination
-mix the powder and liquid into a mixture with desired characteristics
What are the liquid (acid) components of an acid-base cement?
- Eugenol/Non-Eugenol oils
- Polycarboxylic Acid
- Phosphoric Acid
What are the powder (base) components of an acid-base cement?
- Zinc Oxide
- Fluoroaluminasilicate glass (FAS)
What are the types of polycarboxylic acid cements?
- Zinc Polycarboxylate cement
- Glass Ionomer Cement
- Resin-Modified Glass Ionomer cement
What are the types of resin based cements?
- Resin-Modified Class Ionomer cement
- Unfilled Resin cement
- Filled Resin – Composite Resin Cement
What are the different types of zinc oxide eugenol cement?
- Regular ZOE
- Reinforced ZOE
—IRM - ZOE with Ethoxy Benzoic Acid
— increased compressive strength
What are the indications for zinc oxide eugenol cements?
- Temporary
- Cement Intermediate
- provisional cement
What is the powder part of zinc eugenol cement?
zinc oxide
What is the liquid part of zinc eugenol cement?
eugenol
What is the strength of a typical zinc eugenol cement?
compressive = 2-15
tensile = 1-2
What is the strength of a modified zinc eugenol cement?
compressive = 40-50
tensile = 3-5
ZO powder is __% ZO and __% radiopaque filler
99%
1%
ZOE liquid is Oil of _________
Cloves (85% eugenol)
What is the reaction of zinc eugenol cement?
Zinc Oxide + Eugenol = Zinc Eugenolate
Eugenol acts as a _________. Therefore is not a pulpal irritant.
sedative
ZOE is marketed as…
TempBond
What are the uses of ZOE reinforced IRM?
- Intermediate Restorative Material
- Temporary cement /restoration if there is decreased retention or if you need more time in a temporary situation. Used as a provisional or intermediate restoration
*The Eugenol in ZOE can inhibit the ______________ of resin products.
polymerization
- Therefore, forethought is needed if using resin cement after provisionalization.
What are the disadvantages of zinc eugenol cements?
-Slow setting time
-Excess Eugenol can be an irritant
-Cement does shrink as it sets
-Low Strength
-High Solubility
What are the features of zinc oxide non-eugenol cement?
- Temporary cement
- Eugenol is replaced with other oils
- Used prior to permanent Resin-Based cement
What are the disadvantages of zinc oxide non-eugenol cements (Tempbond NE)
Slow set still
Low retention
What is the oldest cement in dentistry?
zinc phosphate cement
What is the reaction for zinc phosphate cement?
Zinc Oxide (Powder) + Phosphoric Acid (Liquid) = Zinc Phosphate
What are the benefits of zinc phosphate cement?
- Easy to manipulate
- Working time is 3 – 6 minutes
- Setting time is up to 14 minutes
- Indicated for Fixed Prosthodontics
- High compressive strength
- Low Film Thickness
How does zinc phosphate cement to the tooth?
Creates micromechanical bond to preparation surface and crown internal surface.
What is the compressive strength of zinc phosphate cement?
4.5 Mpa
Is zinc phosphate still a major cement today?
No longer a major cement in the market as others have
improved on the characteristics of this cement.
What is critical when using zinc phosphate?
Preparation retention and resistance form critical
What is zinc phosphate considered for?
implant crowns due to radiographic visibility, ease of removal
What is the gold standard cement?
zinc phosphate cement
The powder of zinc phosphate cement is made of…
> 75% Zinc Oxide and <13% Magnesium Oxide with radiopaque fillers
The liquid of zinc phosphate cement is made of…
solution of 59% H3PO4, 23% Al Phosphate and Zn Phosphate
What should you know about zinc phosphate when mixing/cementing?
-When mixed, cement becomes exothermic.
-Must mix it on a chilled glass slab to allow for working time
-Create a stringy consistency
-Remove excess cement once set
-Mixed cement is acidic and can cause pulpal irritation
-Once set, the cement can act as a thermal insulator
What is zinc polycarboxylate?
-Zn Oxide – Polyacrylic acid and Carboxylic Acid = ZN Polycarboxylate
Although zinc polycarboxylate has low strength what does it do instead?
form a chemical bond to tooth structure (cement liquid and calcium in the hydroxyapatite bond)
Polyacrylic acid is less acidic than phosphoric acid, so pulpal irritation is…
reduced with zinc polycarboxylate cement
What is the compressive strength of zinc polycarboxylate?
6.3 MPa
What is zinc polycarboxylate marketed as?
UltraTemp
What is the powder for glass ionomer?
Fluoroaluminosilicate Glass (FAS)
What is the liquid for glass ionomer?
Polycarboxylic Acid
What is glass ionomer?
Combination of Ca, F, Al Silicates with Polycarboxylate/acrylic reactions
What is the compressive strength of glass ionomer?
3-5MPA
What are the features of glass ionomer?
- Low Solubility
- Can chemically bond to metal restorations
- Releases Fluoride over time
- Requires strict isolation during setting
- Needs a chilled glass slab
- Do not let liquid component stand for long or it will evaporate and change your cement mixture
There are some cases of delayed _________________ with glass ionomer cements
hypersensitivity
Where are glass ionomer cements used?
Not used commonly. Mostly used for Ortho bands now due to fluoride release.
What are the steps for using glass ionomer?
- Do not let liquid component stand for long or it will evaporate
and change your cement mixture - Remove smear layer left by burs first
- Cement needs tooth to not be dry but not be wet
- Cement excess should be removed immediately
What can happen if you dehydrate a tooth and use glass ionomer?
A dry tooth combined with the initial low pH of GI cements can lead to hypersensitivity
What are the liquid (acid) components of acid-base cements?
- Eugenol / Non-Eugenol oils
- Polycarboxylate Acid
- Phosphoric Acid
What are the powder (base) components of acid-base cements?
- Zinc Oxide
- Fluoroaluminasilicate (FAS) Glass
What is the powder of resin-modified glass ionomer?
Fluoroaluminasilicate glass (same as GI)
What is the liquid of resin-modified glass ionomer?
Polycarboxylate acid with resin monomers (Bis GMA or HEMA)
What does resin-modified glass ionomer cement need besides the powder/liquid?
photo activator
What are the features of resin-modified glass ionomer?
-Strong Cement
-Compressive Strength 24 Mpa
-Fluoride release
-Low Solubility = so ideal for difficult to isolate cases
-Low Micro Leakage = Cement swells slightly upon setting to seal margins
What is the compressive strength of resin-modified glass ionomer?
24 Mpa
Resin-modified glass ionomer cement is ideal for all restorations except…
-Highly esthetic cases. Cement is bright white. IF margin is visible, you might see the cement.
-All Ceramic crowns with margins less than 1mm thick. Swelling of cement on setting can cause marginal fracture.
-Inlays and Onlays are contraindicated for this cement.
How do you use resin-modified glass ionomer?
-Shake powder bottle
-Dispense Powder before liquid. Equal number of scoops to liquid drops
-Hold liquid bottle vertically when dispensing
-Mix powder INTO liquid within 30 seconds of dispensing
-Load Crown with cement
-Working time once mixed is 2.5 m
-Seat the Crown
-Maintain Pressure on the restoration while cement is setting
-Maintain dry field during setting
-Wait 3 minutes
-After cement has set, remove excess
Resin cements require a very _________ sensitive protocol
technique
What does resin cement require?
bonding agent and an etchant
These are either separate or combined.
-Self-Etch
-Total-Etch
Why does resin cement have a high incidence of post op sensitivity?
due to etching process and the failure to seal the dentinal tubules
What does incomplete mixing of a dental cement cause?
either leads to weaker cement, or thicker harder to seat cement which can also lead to hyper occlusion
What does incomplete seating of a dental cement cause?
hard to tell if restoration is down all the way with cement excess
What does excess drying of a tooth before cementing cause?
Leads to post-op sensitivity. Use Gluma (2 x 60 second coats) prior to crown seat to decrease sensitivity.
What does incomplete removal of excess after cementing cause?
gingival bleeding, irritation, bone loss, and possible gingival surgery to remove excess if access is not available
What are the general characteristics of non-adhesive cements?
What are the general characteristics of adhesive cements?
