klas ii onlay

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LECTURE 7:

Inlay and onlays

Lecture outline:

1- Cast-gold inlays and onlays

2- Esthetic inlays and onlays. (composite and ceramic).

Cast gold inlays and onlays:

Dr said that we wont be doing these in the lab but we should know about them as

we might do them later after graduation.

The definition of class II inlay: involve the occlusal and proximal surfaces of a

posterior tooth and may cap ONE or MORE but NOT all of the cusps. This was

definition given by the art and science of operative dentistry.

In the class II ONLAY we cover all the cusps, so it is an inlay but with all the CUSPS

capped.

Indications of cast gold inlays and onlays: when do we do them??

• Large restorations: as we want to control the contact and the contour of

the tooth.

• Endodontically treated teeth: in these teeth we need occlusal coverage, for

any posterior root canal treated tooth we need to protect the tooth from

future fracture by capping all of the cusps “occlusal coverage”, either by a

crown or onlay.

Some may ask: how come we do and onlay and don’t do a crown??

Because it is more conservative.

Example: we have a lower 6 with an MOD cavity preparation, in this tooth

the buccal and lingual cusps are still intact therefore, in this situation

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itsbetter to do an onlay than a crown. In the onlay you’ll preserve the tooth

structure; you don’t have to prepare the buccal and lingual walls.

• Teeth at risk of fracture

Fracture tooth syndrome: teeth with fracture lines, these fracture lines may

propagate to fracture the tooth, if we discover these fracture lines at early

stages, then we can control the problem by capping the cusps of the tooth.

And again it is better to do an onlay than a crown to conserve the tooth

structure.

• Dental rehabilitation with cast metal alloys.

If the patient wants to do dental rehabilitation, he has MOD cavity

preparations, fractured cusps so again the best is to use cast gold inalys and

onlays.

• Diastema closure and occlusal plane correction.

We have space between the teeth, and we want to close it using indirect

restorations, the best is to use inlays and onlays.

• Removable prosthodontics abutment.

We want to use this tooth as an abutment for an RPD and it needs to be

restored, the best treatment for it is to restore it with gold either an inlay

or onlay.

Contraindications of cast-gold inlays and onlays:

� high caries rate, because this type of treatment is consuming and

expensive, so we don’t want to make it a definitive restoration in

high caries risk patient until we lower the caries risk of the patient

� Young patients, fear of exposing the pulp during preparation as the

pulp chamber and pulp horns are high in these young patients

� Esthetics, “gold” and because in these esthetic areas we can do

composite, they don’t need a large more expensive restorations like

onlays or inlays.

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As student asked whether gold was better than amalgam or not? And

the dr said I we want to compare between restorations we have to

compare direct restorations with direct and indirect restorations with

indirect. But ofcorse gold is better, longevity is better.

� Small restorations.

Advantagesdisadvantages

Strength ------Gold Number of appointments and

higher chair time, as you have to

do preparations exactly like you

do for the crown, you’ll send the

patient home with the

temporary.

Biocompatible, with soft tissues temporary

Low wear facets, esp with

opposing teeth so if the patient

has bruxism the best treatment is

to use GOLD. (not like ceramic,

high wear rate of opposing

dentition.)

Cost, because we have lab work.

More chair time too.

Control of contour and contacts,

here compared to direct

restoration.

Technique sensitive because you

need to take an impression the

impression is sent to the lab,

then we have the restoration

that needs to be cemented (like

the crown)

Splitting forceesp for the inlay.

Inlays can cause wedging forces,

increase the chance of splitting

the tooth. That’s why nowadays

the use onlays more than inlays

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Basic principles of cast restorations: basics for any preparation, direct or

indirect.

� Conservation of tooth structure.

o Preparation should be as conservative as possible

o Preparation must be designed to protect the remaining tooth

structure. This means that if you have undermined cusps then

you should cut this cusp because it will fracture.

� Retention and resistance form: it is an indirect restoration so we’ll

need the retention and resistance forms just like a crown.

- Reten?on line is gained by 2 parallel walls (intra or extra coronal).

The retention comes from the buccal and lingual walls in the

crown and onlay but in the inlay the retention comes from the

buccal and lingual surfaces inside the tooth just like the class II.

- the degree of convergence (6-10). The inlay is just like the class II

but the wall in it are divergent to be able to insert the inlay and

cement it later on. Not too divergent, if it is too divergent it will

decrease the retention.

- the length of the walls: length the retention

- Twisting or rotational forces are resisted by the presence of

grooves or pins. And also when you have short wall, you place

retention grooves to increase their retention

� Finish line:

Chamfer finish line for the gold.

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Cast gold inlay:

� Suggested burs:

� Plain straight fissure bur (0.8mm head diameter)

� Plain tapered fissure bur ( 0.5 mm head diameter)

� Flame finishing bur.

In the picture in the slide: 1st

bur is used to do cavity prepara?on. 2nd

bur used to do reten?on grooves, and the 3rd

to make the bevel for

the gold

� Occlusal preparation:

Diverging walls ( 4-5 degree) taper/wall; (8-10degree).

It is basically a class II except: 1) the buccal and lingual walls are

tapered, as it is indirect. The clearance is more ( buccallingually)

to be able to make the bevel and to be able to finish the margin

of the gold2) the bevel, we should bevel the cavosurface margin.

� Proximal preparation:

-Increased proximal extensions relative to amalgam preparations

(0.2-0.5 proximal clearance)

-Definite dovetail

-Undercuts blocked out (Glass ionomer or composite), if you

removed the caries and you have undercuts you’ll use GI to block

them out

-smoothness is critical.

� Beveling of the margins:

-proximal bevel

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-Gingival bevel

You can use the finishing diamond bur or the finishing disks,

exactly like we bevel the composite.

Why do we bevel the margins??

Gold can be burnished, so we bevel the margins to be able to

burnish the gold when we cement it, plus it will be easier to work

with it in the lab

- Occlusal bevels he gold we bevel it are usually not necessary.

(only needed when cavosurface margins are very flat and

margins of gold will be unworkable)

� Retention grooves

-0.3mm deep

-in short wall we have to put retention grooves because

retention in short walls will be jeopardized. Exactly the same as

we did in class II we put them on the buccal and lingual walls

inside the dentine

Cast-gold onlays:

The onlay is the same as the inlay but we cap the cusps. The preparation and

principles are the same. We reduce the cusps and cap them. The finish line will be

on the cusps we don’t extend it all the way done.

� In the slides there is a lower 6:

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Carbide or diamond is used for cuspal reduction.

For the functional cusps (centric cusps)here they are the buccal, we do shoulder

preparation and bevel the shoulder, 1.5-2mm reduction for the centric cusps.

For the non functional cusps (non centric cusps) we do chamferand you don’t

have to bevel the chamfer, 1-1.5 reduc?on for the non-centric cusps.We can place

retention grooves distally and mesially.

� Seating and Finishing: finishing is like the finishing we do in the

crown except here, the gold is burnished to make the onlay fit

better, no gaps between the gold and tooth structure.

� Polish and cementation, we cement it using GI.

In the other part of the lecture we will be talking about:

Esthetic inlays and onlays: composite and ceramic.

Indications:

1. Esthetic, the patient is concerned

2. Large defects or previous restorations. In the indirect you can control

the contour of the tooth and contact

3. Economic factors.Its questionable! Usually the indirect is more

expensive than the direct. But if you compare the composite indirect to

the ceramic indirect it is cheaper

Contraindications:

1. Heavy occlusal forces, especially with ceramic because it can fracture. And

wears the opposing teeth, as we mentioned before whenever we have a

wearing problem, gold is our choice

2. Inability to maintain a dry field, we are going to cement it with resin

cements.

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3. Deep subginival preparations. Because of the inability to isolate and

inability to bind to dentine as you go gingivally enamel will be less and it

binds to enamel better than it does with dentine .

Advantages compared to direct restorations:

1- Improved physical properties. Indirect composite has better properties

than direct.

2- Variety of materials and techniques, because we have more than one

option like ceramic and composite.

3- Wear resistance,

4- Reduced polymerization shrinkage, as we know that composite has

polymerization shrinkage, in the indirect restoration we make the

restoration outside the patients mouth (in the oven or they light cure it)

so the polymerization shrinkage will happen outside the mouth

5- Ability to strengthen remaining tooth structure, as we use resin cement

to adhere it.

6- More precise control of contour and contacts

7- Biocompatibility and good tissue response (ceramic)

8- Increased auxiliary support. Because we have the help of the lab in

making these restorations.

Disadvantages:

1- Increased cost and time (lab work, two visits)

2- Technique sensitivity

3- Brittleness of ceramic

4- Wear of opposing dentition and restoration (ceramic)

5- Resin to resin bonding difficulty (indirect resin). This is related to the

oxygen inhibited layer. When we do resin composite restoration

outside the patients mouth, there will be a problem in binding it to

the resin cement in the tooth, because when we do it outside the

patients mouth (the light curing and polymerization shrinkage) we

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put it in the oven for heat, in the polymerization of the composite

the double bond becomes a single bond. And it bond to other

composite because it still has double bonds to bind! So here most of

the double bonds are converted, so the ability to bind it to resin will

be difficult.

6- Short clinical track record, doesn’t have long clinical studies to tell if

these restorations can live long. (longevity)

7- Low potential for repair (ceramic). Fractures are difficult to repair

inside the patient’s mouth. In resin you can acid etch and add to it

and sometimes we even do sand blasting intra orally.

8- Difficult intraoral polishing, this applies to ceramics.

Types of esthetic inlays and onlays:

� Resin composite inlays and onlays

� Posterior bonded porcelain restorations

� CAD/CAM ceramic restorations. ( the new technique)

Resin composite inlays and onlays

Specific indications:

� Maximum wear resistance is desired from composite

restoration

� Achievement of proper contour and contacts. ( again

comparing direct from indirect)

� A ceramic restoration is not indicated because of cost or

concern about wear of the opposing dentition. We need

esthetics but at the same time we can’t use ceramics because

it is expensive and it wears the opposing teeth so we use

composite.

1-Preliminary consideration:

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a- Discuss cost with the patient. More expensive than direct restorations.

b- Identify occlusal contacts ( marks with articulating paper) and degree of

wear. This is when we examine the patient and discuss the treatment

options with the patient, if the patient has wear facts and heavy occlusal

forces we can’t do ceramic restoration.

c- Identify shape desired (vita guide), because we are working with esthetic

restorations.

d- Plan for type of temporary restoration; make alginate impression of

restored quadrant if necessary.

2-isolation: rubber dam isolation is highly recommended

3-preparation:

-recommend brassler esthetic inlay and onlay kit. If you don’t have it you can use

the straight fissure bur or tapered fissure bur or diamond bur that we use for

crown and bridge work.

Basic principles of tooth preparation:

1-all margins should have 90 degree cavosurface. Here on the contrary to gold.

Why should they be 90 degree? In the gold onlays and inlays, the margins should

be beveled in order to polishable margins. But here we need the cavosurface to

be 90 degrees because you need good thickness of ceramic/composite to avoid

fracture.

A student asked why we bevel the tooth surface when we do a class IV?

Because we want to bond more tooth structure, but here in this case we have a

gap and we use the cement , you don’t bind to the whole tooth structure there.

And in the class IV you will bind it using adhesive but here you will be using

cement.

2-all the external and internal angles should be should rounded, to reduce

stresses.

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3-buccal and lingual walls should be occlusaly divergent.

4-the occlusal step should be 1.5-2mm in depth

“The resin composites and ceramic thickness should be at least 1.5mm”

5-isthmus and groove extensions should be at least 1.5mm wide.

6-smooth and relatively flat pulpal floor.

7-proximal clearance should be at least 0.5mm, buccal and lingual clearance in

order to be able to finish the margins. When we cement it in order to remove the

excess cement.

8-gingival margin should be extended as minimum as possible. As we said for

isolation, and bonding to enamel is better than bonding to dentine

9-capped cusps should be reduced 1.5-2mm and have a 90 degree cavosurface

angle.

The dr just zoomed thru the slides quickly and said: this is just preparation read it!

Then again she read on and said:

Page 10 slides: dual cured lu?ng resin and dual cured den?n bonding agent (

followmanufracturer instructions) dual cure: starts with dual cure cement then

you have to light cure at the margins.

Rebond margins with unfilled resin: in finishing and polishing we can remove from

the margins, so we can do acid itching then use the unfilled resin (adhesive) and

light cure it.

CAD/CAM ceramic restoration:

Computer-aided design/computer-assisted manufacture.

The difference between this technique and the conventional way is that the

impression here is digital, then you enter the image into the computer, the

computer will do the design for the restoration then we will have the milling

device.

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It is inbetween the lab and chairside.

Slide page 10 this is the machine (like a computer) that is connected to the milling

machine which has burs. Then we have the blocks; resin composite blocks or

ceramic blocks. These blocks are inserted in the machine, then we take a digital

image of our preparation which will be sent to the milling machine which will

make the restoration and then we cement it.

Its use is limited to inlays, onlays and ¾ crowns.

The dr just read the case seletion and contraindications.

(Follow the pictures in slide page 11)

Again a tooth is prepared, we have to spray special powder for the computer to

be able to take the optical image. We also have aintra oral camera. In the

computer there will ba a 3D image designed, then in the milling machine which

has burs ( two diamond burs) it will carve the external surface of the restoration

and internal surface, then we cement the restoration by DUAL CURED CEMENT.

SO IT IS A SEMI-DIRECT RESTORATION.

End of lecture

We’re almost there….DENTISTS.

You don’t have to be great to start…but you have to start to be great.

BANAN AL-NATOUR