Dental Materials 3rd BDS Cement

8/2/2019 Dental Materials 3rd BDS Cement

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Adhesion and Cements

Objective- GDC

DENTAL BIOMATERIALS SCIENCEInstruction in the properties, correct manipulation and the science underpinning the

use of dental materials is needed to equip the student with the knowledge to

select and handle those materials safely and effectively. Dental students need to

understand how such materials, and the biological responses to them, are

evaluated. This equips them to cope with future developments in this area. The

GDC considers it is essential that staff teaching this part of the programme work in

close collaboration with clinical colleagues.

have knowledge of the science that underpins the use of

dental biomaterials

have knowledge of the limitations of dental materials

be familiar with those aspects of biomaterial safety that relate

to dentistry



Before Adhesive Dentistry-

How do you stick on a crown or inlay? Answer-

Classic Acid-Base Dental Cements

EGZinc Phosphate cement (introduced in1879)

Zinc Oxide /Eugenol (introduced in1894)

These are still in use- there used to be manymore



How do they work?- To cement things in place

they are referred to as Luting Cements

Just like the mortar that holds bricks together

in a wall (Lutum= potters clay (latin))

Cement takes up the space between theprosthesis and tooth, and on setting provides

mechanical retentiveness (effectiveness

conditional on the geometry of the tooth

preparation



Caution!

Luting is a term that relates to role not to

chemistry

Acid/Base Cements like Zinc Phosphate / Zincoxide / eugenol also used to be used as linings

and temporary dressings

For dressings etc. they are mixed to a

rather thicker consistency



Zinc Phosphate- Classic luting Cement



Recap

Classic Luting Cements are part of the

dental armamentarium that has been around

for ages

They tend to set by acid / base reactions

They tend to be multi-role materials that

when mixed thick can be used for linings

They are not strictly adhesive to tooth tissue

or to restorations (but may cling tenaciously to

clothing and instruments)



Developments in Luting Cements

Since the arrival of composites and glass

ionomers this picture has become more

complex

Some Luting cements around that are

actually adhesives in the strict sense

Two sorts-

± Ionomer cements

± Resin Cements



Developments in Luting Cements

Remember

± Micromechanical Adhesion comes from the

wetting and permeation of the microscopic

roughnesses of a material adherend(The

surface to which an adhesive adheres) by the

adhesive

±Chemical (specific) adhesion is a result of both theintimate wetting and permeation described above

AND attractive interaction between adherend

and adhesive



Ionomer cements

Sticky because of the polyacid present butotherwise handles as a traditional Acid /

Base cement



Ionomer cements

Poly-F (Zinc Polycarboxylate) cement

lacks the Glass bit of Glass ionomersIt is an acid base cement with some real stickiness



Resin Cements

In essence these are runny composites (DONT

confuse with flowable composites)

Resin cements are used in conjunction with dentine

bonding agents and are capable of micro-mechanicalattachment to tooth structures and to surfaces of

restorations. This bonding is micro-mechanical in

nature and depends on surface microroughness.

Some resin cements are formulated to possess anadditional chemical agent claimed to enable them to

bond to restorations and may display some chemical

adhesion



Resin Cements

Key Role-

± Cementation of Ceramics

±Porcelain is brittle

± If it is not BONDED in place by an adhesive it will

fracture

± An all porcelain restoration cannot be

successfully cemented with traditional luting

cements



Resin Cements

Resin cements often claim clever means of getting chemical

adhesion but a resin cement has many characteristics in

common with Resins in general- it will flow into microscopic

features and adhere by wetting and permeation. Any real

chemical adhesiveness is in some ways still controversial



Resin Cements

Panavia 21

Anerobic curing resin

cement

Opaque

Claims chemical adhesion

through phosphate esters in

resin

Often used to cement

metals to tooth-

± Resin retained bridges

± Metal/ceramic Crowns

Nexus 2

Dual Curing Resin Cement

Comes in a variety of shadesand opacities

Comes with try in pastes

so that aesthetics can be

fine tuned prior to

cementation

Often used to cement

translucent optically

linked restorations to tooth





Rely X Luting Cement



The Rely X Unicem on Clinic



The Rely X Unicem on Clinic

What do you make of these claims?



Dentine Bonding Agents Vs Resin

Cements Dentine bonding agents are resin materials

used to make a dental composite material

adhere to bond to both dentine and enamel

Resin Cements are resin materials used to

cement a restoration (usually made by indirect

means) to tooth tissue and/or restorations

already present



Dentine Bonding Agents

Further Details Are available in the DVD

lectures to be found on VITAL- 2nd Year



Documents

Dental Materials 3rd BDS Cement