(2) cavity bases and liners

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م س ب له ل ا ن م ح ر ل ا م ي ح ر ل اCavity bases and liners:- dr. says every year I give this lecture to fourth year dental students What are the aim / purpose of this lecture? The purpose of this lecture to defined and understand the terms of liners, bases and varnishes what’s more important is to name the different materials available in the clinics and to understand the indications of each of them. When you go in and out of the clinic as a fourth year dental student you must know and learn all the procedures that are related to specific material or instruments. ا ان ي ح ا ي ح ي ب دك ي ع ض ي ر م ك ل ي ك ح ب و, ت ل م ع وه3 ش ح ن م و عد ب ما ها, لت م ع صار دي ي ع س حس, ب , او ض ي ر م ي ن ا3 ن ي حك ي ب ي ل ي ك ر ور, ت ك د ر س ح ن ي عد ب و ع, ق و ا ,اد ي ف له ك3 ش م مان ك... ض ي ر م راح د ي ع ور, ت ك د ي, ق ل و دوا ي ع وس ش, ب وا ل حط و وه3 ش ح\ ة\ ت, ق ؤ م وا ل وحكا ع ج ار دي ي ع عد ب وع ت س ا ي ف ا ي ع ح صطل م له م ع, ت س ب اء ي ط الأ ي ف طاع, ق ل ا عام ل ا وه3 ش ح دها ن, ه طان ي.. 1

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Page 1: (2) Cavity Bases and Liners

الرحيم الرحمن الله بسم

Cavity bases and liners:- dr. says every year I give this lecture to fourth year dental students

What are the aim / purpose of this lecture? The purpose of this lecture to defined and understand the terms of liners, bases and varnishes what’s more important is to name the different materials available in the clinics and to understand the indications of each of them.When you go in and out of the clinic as a fourth year dental student you must know and learn all the procedures that are related to specific material or instruments.

عملتها ما بعد ومن حشوه عملت وبحكيلك مريض عندك بيحي احيانا جسر دكتور ركبلي بيحكي ثاني مريض او, تحسس عندي صار

ولقي دكتور عند راح مريض كمان... مشكله في اذا, وقع وبعدين أسبوع بعد عندي ارجع وحكالوا مؤقتة حشوه وحطلوا تسوس عندوا

بطانة بدها حشوه العام القطاع في األطباء يستعمله مصطلح عنا في


Y3ne this filling need a lining.. 7ashwieh bdha b6anieh. this terms will be explained in this lecture why do patients feel sensitivity, why do crowns and bridges fall down and why do we need lining, what’s the difference between a liner when it a suspensions and when it a solutions? We must differentiate between these terms.

ALL you know that dentine is sensitive?! Like when you eat ice-cream you feel sensitivity “you feel a lot of cold sensation in your teeth” this mean that dentine is exposed and when the dentine is exposed you feel dentine sensitivity, know this is a disease? I don’t think this a disease but is a problem, it is a public problem?


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Yes it is many people suffer a lot of dentine sensitivity. If someone told you I have pain in cold drinks what do you advice him: some of you will say RCT; RCT is drastic measure it should be the last choice it shouldn’t be the first choice So what we can do to stop or prevent this dentine hypersensitivity. Why do some patients experience pain after filling? Today an amalgam filling was placed in your tooth and after week you will come back to the dentist you say to him I came to you to solve a problem but you didn’t solve this problem you create another problem that is I feel pain after you put the amalgam filling in my tooth, Some says there is something called:Microleakage gap between the amalgam filling and the tooth, there is shrinkage of the material and when there is a shrinkage there will be a space between the material and the tooth “cavity walls” there will be accumulation of food debris maybe sweet drinks and in this way a process of recurrent caries might be initiated.

Then postoperative dentine sensitivity will take place after you have finished a conservative treatment for the patient and this operative dentine sensitivity will come from toxic products and stains from restorations or any other toxic products from the filling materials they will be in close contact with the pulp or the pulpal tissues that may irritate the pulp and cause problems to the patient , bacteria from oral cavity might go into the cavity or in between the cavity and the walls of the cavity ,and this bacteria may cause problem and cause postoperative dentine sensitivity So to solve all of these problems we have to consider the application of liners underneath our fillings so: I’m going to cover the following topics today one of these topics is liners and what are liners, what the indications of liners and


Page 3: (2) Cavity Bases and Liners

what are the differences between solution liners and suspension liner s !!! I will talk about seven bases and I will pay particular attention to glass ionomer and how we can improve the properties of glass ionomer to bring it to the properties of composite ,how ever there are certain disadvantages of composite how I’m going to improve these disadvantages and bring them close to the good advantages of glass ionomer.

Liners: liners classified under two categories:- Solution liners (varnishes) - Suspension liners

Solution Liners: is another word that goes to varnishes, if you say varnishes it’s mean solution liners but if you say suspension liner it does not mean it is a varnish, suspension liner is different category but varnishes and solution liners are the same, So what are solution liners ??

They are made of natural gum e.g: Copal or from synthetic resin e.g : Nitrated cellulose. solution Liners they can be natural gum or synthetic resin and when it natural or a synthetic resin when it dissolved in organic solvent such as Chloroform, Acetone or Ether it become solution Liner . Basically what is solution liner it natural gum or a resin, Now natural gum isn’t good as a liner I wanted to be like a thin film what I do to it?? I dissolve it in chloroform , acetone , ether it leaves behind a thin semi permeable membrane which can protect the dental pulp from toxic products of restorative materials as well as from microleakage of newly placed amalgam.


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So it protect from the toxic material come from restoration or microleakage and oral fluid and bacteria .when it dissolve it become a liner the I applied it to the cavity in the tooth .

The” Ether, chloroform, acetone “will evaporate to leaving behind a thin film of liner on the surface of the cavity, this thin film will protect the cavity “the open dentinal tubules “

What is the wrong in newly Amalgam? When you place amalgam today in the next 48 hours amalgam will be subjected to a process of setting “chemical setting, chemical reaction “this may result in shrinkage of Amalgam and after 48 hours Amalgam will expand and the shrinkage will be compensated by means of corrosion so the space that resulted from shrinkage of amalgam will be filled by the process of corrosion, but the first 48 hours are critical, what do I do to them?? I need something to protect my cavity at least for the first 48 hours until corrosion process take placed and the space between the cavity walls and the amalgam is filled which can protect the dental pulp from toxic products of restorative material. What is the thickness of this liner?Thin films usually not exceeding a thickness of 0.5mm, can you name a commercial products used as liner? Its copalite, copalite is a commercial product that available in our clinics. And it also Example of varnish: copalite

The proper way to apply it: Take some of this material by using cotton pellet then swab the cleaned cavity after you have done this you need to air dry, then reapply varnish again so first layer of varnish then air dry, second layer then air dry the indication that you do this in a proper way


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you will receive a shiny hard surface which is ready to receive the filling.

What the function to varnish? To protect the pulp from a toxic product from the restorative material. Now I want you to appreciate that the thickness of this material is about 0.5mm, you have to know that the minimum depth of the amalgam restorative material about 2mm.If I don’t use Varnishes what I can use:

Dycal Cement bases

What that means if I put Dycal in minimal cavity? It will take part of thickness left for amalgam; it means that I have to deepen my cavity so that will accommodate the Dycal and the Amalgam (you gutted this is important piece of information) so when you a cavity that already 2mm only you can’t apply cement or Dycal. What you advice to do you want something very thin that doesn’t take away anything from the depth of the cavity and that is what?? For sure it Varnish, varnish here save your purposes into two points:

1- Protect your pulp2- It will keep the depth of cavity preserved.

Know the second category: Suspension liners: Ca(OH)2 or Dycal.These liners contain suspensions such as calcium hydroxide and zinc oxide in a synthetic resin .”in varnish sho kan ? gum dissolve in acetone , Ether , chloroform “ but here it contain suspension liners “m7alil mo3lqaa “ instead using gum we use as calcium hydroxide and zinc oxide in a synthetic resin in the


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top of the synthetic resin we have seated what ? Calcium hydroxide, zinc resin and that seated in synthetic resin.• They are applied to provide a barrier against irritating compounds of most restorative materials .this feature of suspension different from varnishes but the purpose of applying both the same, both provide a barrier against irritating compounds the pulp.

• Examples about suspension liners:1- Pulpdent 2- Dycal 3- Life

the main one in your clinic is dycal.

Dycal:- Dycals had a problem in the past which is the radiolucency, but now its radiopaque this means when you take a radio graph it will appear that is the purpose of Ca to being radiopaque.Radiopaque calcium hydroxide is a rigid, self – setting material useful in pulp capping sometimes you have two situation either you very close to pulp or you already you expose the pulp and there is pin point evident by appearance of blood, So it a protective base / liner under dental filling materials. Dycal makes protection against any heat any sensitivity and prevent he toxic product which come from the restorative material or from the Bacteria and promote the formation of secondary dentine, anyone can tell how? That’s because dycal have Alkaline PH and bacteria doesn’t grow in this alkaline media so it bacteriostatic .so bacteria are not like to grow in alkaline media and doesn’t grow that what I mean by bacteriostatic action . Some researcher thought that due to Ca which is ingredient of Dycal, ca might release from it and used for the formation of secondary dentine, as you know hydroxy


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apatite Ca10 PO 4(OH2)6 so we have in the mineral of the tooth which is calcium if calcium lost through pulp exposure calcium might be promote form Dycal and used for the formation of new dentine some thought that but it FALSE because calcium not released from Dycal its can’t released because is not a free ion . So if there is Formation of newly dentine is come from odontoblast not from Dycal and because the growth of bacteria has been stopped the tooth and the odontoblast will take their time successfully to fill the gap by producing some dentine this is a process by which the pulp exposure has been healed so its promote secondary dentine formation.

Dycal is easy to place with ability to follow where needed while it stays in place when necessary. it is alkaline and has antibacterial activity. it’s neutralizes the acids form restorative material .

Dycal disadvantages: Tensile strength is low. Exhibit plastic deformation, deform under pressure. Undergo hydrolytic breakdown and dissolve under acidic

conditions. Bacteria may decompose it .Hence it may disappear under

restoration when there is microleakage. Dycal come in Single –paste system or in Visible light-cured .It utilizes the polymerization of dimethacrylate by means of light, so they are actually chemical setting or visible light cure setting, by curing or by chemical setting 2 tubesone is the base: main or supporting ingredient in material.And the other catalyst: substance that initiates a chemical reaction.


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We mix them together until setting happened by chemical reaction.

Now we moved to another which cement bases: these bases

May be placed in thick layers on pulpal floors of deep cavities to provide thermal, chemical and electrical insulation for dental pulp.

It serves a protective, therapeutic or structural function.

One example of these bases is glass ionomer which serves as dentine substitute.

So varnishes we finish with them “khliko mrkzen m3e “, suspension liners we finished with them no we come to the base, the difference between them: solution it is used when we need very thin layer, if we can afford to make more than layer thicker we use suspension liner and it has its own indication like in pulp capping, now if we have a deep cavity you allowed to use bases Why Bases??Because we want to protect the pulp against thermal, hot and cold, chemical, toxic products and electrical insulation. Are there electrical current in the oral cavity? The answer is yes.

Now I want you to remember that the saliva has in it minerals it like electrolyte if you have a filling in the upper jaw and another filling in the lower jaw one of them will act as cathode and the other one will act as anode, So if you have anode and cathode and you place them in the solution “ electrolyte solution” there will be some currents propagated between the two cathode and anode, this process in the oral cavity is called


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galvanism, so if I want to stop galvanism I will need insulator which is the base, so it serves as a protector ,protect the pulp like if we use zinc oxide eugenol ,its provide tranquilizer effect ‘’mohade2 LL A3sab ‘’ .

Examples of these bases is:

1- Zinc phosphate cement:

It s very important material in dentistry but it has disadvantage a very bad one that is acidic in nature especially in 24 hours ,when you mix the base “powder and solution “ you create a very acidic cement , it irritate the pulp it has low PH = 1.6 which found after two minutes of mixing , PH below 4 within the first hours and the PH rises again to 6-7 after 24 hours .so after 24 hours Zinc phosphate cement is ok but the problem in the first when you mix it and placed especially when you very close to the pulp you get a mixture which has a PH = 1.6 .PH of 1.6 is very low found after 2 minutes of mixing, when you place it on the tooth and if you are near the pulp the tooth will demineralize, next day the patient come to you with a very high sensitivity due to the PH.

The zinc phosphate cement is used to cement crowns and fixed partial dentures it’s used as a temporary restoration, it’s used insulating base.

The characteristic feature of Zinc phosphate cement that is produce heat when it mixed. Disadvantages of Zinc phosphate cement:

Its PH=1.6 after 2 minutes.


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It is soluble in oral fluids. It has no anti-bacterial properties It very soluble in organic acids

2- Phenolate: Zinc oxide eugenol cement:Basically it Powder “Zinc oxide “and Liquid “eugenol” mixed together to form a mixture that’s used to provide a good marginal sell, it has antibacterial effects, it has anodyne (tranquilizer) effect.

Disadvantages: - Low compressive strength - It is not adhesive to cavity walls so the cavity walls have to have mechanical retention. - Long time setting - Stain the composite restoration, it should not used under composite.So we can’t put composite over it or over the gutta percha which made from eugenol that’s why we have “AH 26 gutta percha” that doesn’t contain eugenol ‘eugenol Free’.

I told you it’s has long setting time and low compressive strength we tried “m3shar a6ba2 el Asnan” to improve the properties of this, now they are to component of this base cement one of the powder and the other is the solution, if you add some fortified inside the powders component or any ingredient to the solution you may aimed to improve it by adding Silica, Alumina or Resin to powder or by adding Orthoethoxybenzoic (EBA) to liquid.

By this the resultant is not the usual Zinc oxide eugenol which has some disadvantages but the resultant is fortified zinc oxide eugenol which has better properties than the conventional


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cement , one example is called : IRM ‘’ IRM intermediate restorative ‘’So IRM is Reinforced zinc oxide eugenol cement that contains natural or synthetic resin to increase the compressive strength.

3-IRM (intermediate restorative material):Uses and characteristics:

1- Temporary restoration up to 1 year 2- Base or a temporary cement 3- Not used under composite restoration..Why? Because it

contain eugenol.

EBA “EthoxyBenzoic Acid” cements:- Contains ALmina and polymeric reinforcing agent, Stailine which is a commercial example.But the fortification has been added to what in EBA ? to the Liquid or to powder .

4- Glass Ionomer cement: comes in powder and liquid Powder is finely ground calcium aluminosilicate glass.Liquid is polyacrylic-itaconic acid Or other poly-carboxylate acid copolymer.

- Glass ionomer has poor esthetic- Prolong setting reaction - Poor wear resistance- Handling difficulties - Sensitive to moisture and desiccation- Low flexure strength- Low fracture toughness

Now we have to improve the characteristics of glass ionomer we made Refined Formulation by adding Tartaric Acid.


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And by adding Sliver they make it Radiopaque and stronger . ”also silver included in amalgam” but by this we create one disadvantage which is no more become tooth color material ,the color of the material is metallic now .The main advantage of glass ionomer is will releases fluoride and the coefficient of thermal expansion similar to the tooth structure.Biocompatible and inherent “chemical” adhesion to tooth structure. Uses and characteristics:

Cementing crowns and fixed partial dentures Temporary Filling Base material The main characteristics feature of this and advantage is

that Resist Recurrent Decay, Simply because of release fluoride.

Advantages Again: It bonds chemically to Enamel and Dentine It has high compressive strength It is able to release fluoride It has good marginal Seal Why? For simple reason

because it chemically bond to enamel and dentine.

Indications:1- Direct restorative Class 5 Root caries Pediatric dentistry

2- Resin-modified version

Tunnel preparations


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Basic Glass Ionomer Types:-

1- Conventional glass ionomer: Traditional Acid-Base reaction.

2- Resin modified glass ionomer (RMGI): Light and/or chemical cure.

Resin modified glass ionomer: please refer to slide # 36 Dr. said here we have glass ionomer and in the opposite side we have composite and between them there is resin modifies glass ionomer and compomers . So composite is very strength material and it has good esthetic ,what comes next to it is compomers it is strong it has least esthetics than composite but it more esthetics than Resin modified glass ionomer . and when you look to glass ionomer you see it fluoride release and adhesion it adheres to tooth structure and release fluoride but RMGI is less fluoride releasing and composite no release.


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# Attempt to combine benefits: # Attempt to reduce disadvantages :

Glass ionomer

fluoride release * hydration sensitivities adhesion * Delayed Set * poor early strength

Composite resin

Strength * polymerization shrinkage Esthetics * Microleakage * Recurrent caries

Again please refer to # 37.. Here is a table that show you, Glass ionomer, RMGI, compomers, and composite let’s take the flexural strength that measure by mega pascal here GI 15-25, RMGI 53-25, compomer 60-94, composite 85-97. Look to fluoride Release in GI and RMGI are High and minimal or none.

Pascal:- It is measure of force per unit Area, defined as one Newton per square meter.(megapascal = N/mm2)

Dr. Said I will live the clinical applications for you to read at home but I want to talk about Vitrabond:Is resin modified glass ionomer “RMGI” synthesis by 3M ESPE dental company, So we I ask you in viva questions give example about RMGI you will answer Vitrabond.


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Vitrabond is light cure glass ionomer is recommended to be used as a liner, Remember as a liner is not used for pulp capping, if you want to use pulp capping material what material of your choice?? Calcium hydroxide which Dycal and you may cover the dycal by Vitrabond and then put your filling material in the top.

Clinical Applications:-

Cavity Extending 0.5mm in Dentine:1- Coat the cavity with two layers of resin varnish

using brush. 2- No insulating cement base is required.3- DON’T deepen a cavity by removing dentine in

order to place an insulating base.

Cavity penetrating Further:- 1- Place GIC over the pulpal floor or axial wall

“before it set the floor of the cavity and the axial wall just to the floor here but in the solution liners we put it on the walls because it’s thin material “

So here we only cover the wall of the pulp " floor and axial wall" so if you cover the buccal wall or lingual one in class 1 cavity you are wrong because there is no pulp there.

2- Apply varnish after GIC Advantages :- 1- Reduce the amount of required amalgam for cavity

filling2- Insulator3- Reduce microleakage4- Substitute dentin


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Very deep cavities 0.5mm from the pulp:- 1- Pink dentine and Exposure2- line with calcium hydroxide cement3- Place cement base GIC4- apply varnish before amalgam5- Place filling

Composite Resin Restorations

1- Calcium hydroxide or Vitrabond 2- Shallow cavities: no need for lining or use dentine

bonding agent instead3- Recurrent caries: use light activated glass ionomer


ج كّل' هم' ومنقض كّل' كرب مذهب كّل'أّنتاللهم' اّن'ك مفر'غم' ومخل'ص كّل' عبد ومنقذ كّل' ّنفس خل'صني الل'هم' برحمتك واجعلني من عبادك المنقذين ...سبحاّنك ال اله

بسكوّني لديك اللهم ال وأكرمني إليك فارفعني أّنت إالتخيب لنا رجاء وال ترد لنا دعاء اللهم حقق رجائنا واستجب دعاءّنا ... اللهم ال تردّنا خائبين وال محرومين ..برحمتك يا أرحم الراحمينال إله إال الله الحليم الكريم سبحان الله رب العرش العظيم ّنستغفر الله العظيم الذي ال إله إال هو الحي

إليهّنتوب والقيوم

Mwfken w In Sha2 ALLah mn A3La EL3alamat jme3an

Hanan Majed Mhamid


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Some questions may help you:

What is the ingredient that is added to the fluid of the zinc oxideEugenol to make it fortified?- Water- EBA- Eugenol- Pepsi

One of the following is adding to the powder?- EBA- Silica, alumina, resin- Zinc oxide

Vitrabond is example about? RMGI What is the example for fortified zinc oxide eugenol? IRM


-Glass ionomer is probably the most popular base because of its specialized functions:

It releases fluoride ions. It bonds to enamel and dentin.

It is radiopaque (blocking radiation, such as from X-rays).

It is compatible with all dental restorative materials “ALL of the above true “


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-Zinc oxide eugenol is one of the most popular dental bases for the following reasons:

It is sedative (soothing) to the pulp. It insulates the pulp from thermal forces.

It protects the pulp.

Oil of cloves in the eugenol produces a calming effect on the pulp.

It is not compatible under resin-based restorations because the oil of cloves interferes with the bonding of the resin “ all of the above true “

-What is the purpose of a base?

a. to stimulate secondary dentin growth

b. to insulate the pulp from hot and cold

c. to release fluoride

d. to seal the dentinal tubules

e. none of the above

Answer: b. A base is placed on the floor of a tooth preparation to soothe and insulates the pulp from hot and cold temperatures.

-Which of the following best describes cavity varnishes?

a. seal the dentinal tubules


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b. flow easily but evaporate quickly

c. should not be used under a glass ionomer or resin restoration

d. both a and b

e. all of the above

Answer: e. Cavity varnishes seal the dentinal tubules, are liquid so they flow easily, evaporate quickly, and should not be placed under a glass ionomer or a resin restoration because they inhibit the bond strength of the material.

- Which medication stimulates secondary dentin?

a. amalgam

b. composite

c. calcium hydroxide

d. zinc oxide eugenol

e. both c and d

Answer: c. Calcium hydroxide is known in dentistry as a liner that stimulates secondary dentin. It is placed on the floor of the cavity preparation just above the pulp.