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Prosthodontics Laboratory 9.

Done by : Osama Yousef.

-no defined subject to talk about, the ideas are random-well continue speaking of RPD design and well also speak of some points w etalked about them earlier-Everytime you see a line separating two paragraphs that means its the start of anew subject-For demonstration purposes only the images are from a patient mouth but this

process IS NOT ON THE PATIENT its done on the cast.

As you already know , when we talk about RPD design we either classify eachcase we have according to :-1- Kennedy classif ication.**Reminder**

The basic configuration for each class of Kennedy classification for e.g. :A. Class I: default ( or mostly preferred ) is Bilateral designB.Class ll : tripodal designC.Class lll : QuadrilateralD.Class IV : it depends on the length (extenstion) of the edentulous area it can bebilateral or quadrilateral designs .**For images of this please look at laboratory 8 pages 6-8.

-2- Ti ssue suppor t: class I , ll and long span IV : tooth-tissue supported class III is: tooth-borne .But looking at the table below youll discover new concepts for the tissue support classification.

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Class Support Retention1 Tooth-tissue Tooth ( weak )ll Tooth-tissue Tooth ( weak )lll Tooth-borne Toothlll ( rare cases ) Tooth-tissue Tooth ( weak )IV ( long span ) Tooth-tissue Tooth ( weak )IV ( short span ) Tooth-borne Tooth

As we said earlier , the default design of class III is quadrilateral ( meaning 4 spots or clasps assemblies have to be present )But what if one of these points is mi ssing or I cant have support on it or I

cant have retention on it ?-Ill treat it as tooth-tissue supported and weak tooth retained . This is veryimportant during designing and it might get tricky ( well see an example aboutthis where we initially start with a class lll and we think that its tooth -bornesupported and tooth retained , but as we go further with the design we discover thatits not ) so keeping an eye in these things is crucial .

-As you already know from other subjects , Amalgam fillings need to be 2 mm minimum to prevent fractures .CASE I: If a pa tient came to me with an amalgam restoration , I dont know howdeep his amalgam is , so when placing a rest the remaining space might be 0.5 mmand this is very weak and might fracture , because as you already know amalgamis good in compression but bad in tension .SO IF I DIDNT PUT THE AMALAGAM I NEED TO BE VERY WORRY ANDCARFAUL WHILE PLACING A REST .

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CASE II: lets assume that we have a very deep amalgam restoration ( which isvery rare ) iam allowed to put a rest on it as long s the remeaing amalgam isATLEAST 2 mm thick .** Remember this one is my last choice because we REALELY put a rest on an

existing restoration .

CASE III: Worst case if I had a very bad tooth ( destroyed and very worn out ) Ican put a crown on it and then attach a rest.While doing so the crown has a metal part that is attached to porcelain and thismetal part will be attached to the rest. (rest = metal , crown = metal ) .

We talked about mobility in the theory but were going to talk abou t again in thelab :

Because its going to change a little bit from what we said in the theory.

There are several different classification for mobility in dentistry but the simple

and most used in filed is Grrace and Smoles classification .They have divided this mobility of the tooth into :

Grade 0 No apparent mobili ty , very healthy , I dont worry about it. Grade 1 there is mobility but its less than 1 mm bucco-lingually . Grade 2 there is a definitive mobility but its 1 -2 mm bucco-lingually Grade 3 severe mobility and its grater than 2 mm bucoo-lingually

AND there will be vertical component to the motion .

-Usually tooth grade 3 is HOPLESS ( ) meaning that there is noapical bone leading for the tooth to go up and down. And this tooth needsextraction.

What does this classification means for RPD design? Many of our patients have partially ednontlues mouths and the remaining teeth are not in excellent health .

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Grade 1 as weve said in the theory , I can put a :

Rest on it ( support ) Axaillary retention ( stress-releasing ) combination clasp ( wrought wire

on the buccal and cast reciprocation on the lingual ) .Or clasp (it helps in retention but doesnt provide the main retention ) . Reciprocal arm ( reciprocation ) Guide plane . Lingual plate

For example if I have two teeth with Grade1 , I can put a lingual plate on themwithout any rest or arms or anything just a lingual plate .

. , , Grade 2 :A bit more complicated , this is debatable some say you can use it others say noyou cant use it .-The doctor personal opinion is to stay away from grade 2 teeth .

So many doctors will say Nothing, except we can put on them these things:

Guide plane on ONE surface BRACING OR SPLLINTING Lingual plate BRACING OR SPLINTING SOME doctors say it can provide Auxiliary Support (well see in this lab

in some of the examples how we put a rest not to provide support but just tostop the tooth from moving ) .

NO RETENTION , NO PRIMARY SUPPORT in this grade Preventing supra-eruption from coming by putting a Rest on it as an

example.

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Theyre as you already know classified according to :1- the location ( suprabulge and infrabulge or occlusally approaching andgingivally approaching )2-stress releasing and non-stress releasing :

Non-stress release : (pictures are in lecture 8 ) Cast circfumental : usually first choice if not esthetics of concern ( occlussally

approaching Akers , Gingivally approaching : Roach ) .

-We have modifications to the C-clasp : simple circlet and reverse circlet .Simple circlet it approaches from the edentulous area .Reverse circlet approaches away from the edentulous area.

Ring clasp : it might have 2 rests on either side to reduce flexibility as we said .And it provides its own bracing (because it surrounds the tooth ) . And sometimeswe put a sturt to make it stronger.

Embrasure ( double akres / compound clasps ) Reverse action C-clasp ( hairpin )

and clasp Extended clasp: very rare , one clasp extending to different teeth. Multiple clasps: opposite to embrasure, insisted of putting the rest on the middle

between two teeth . We put rest on each tooth and extend from them. Wrought wire ( combination clasp ) Onlay clasp

Stress-releasing : indicated in class I,II , long span IV and some rae cases ofclassIII.

1) RPI 2) RPA 3) Combination clasp

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- Now in this design were doing the UPPER ,

-This is Kennedy class III , mod I , And support

classification is tooth-supported ( FOR NOW ONLY ) .-I have Grade 1 mobility on right 7-Grade 2 right 8 and left 7, 8

-As always we start off by coloring our Abutments with the color yellow . ( notice we didnt color the 8,7on the left because in this course we consider grade llmobility not good as abutments . But this is only for

th exam purpose ) ( fig.1)

After that I add Rests (purple) as in the picture.(fig. 2)

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after that I need to add my MinorConnector , -since this is Maxilla ( and thedoctor didnt provide any further information) Ill go with the Meshwork . ( fig. 3)

-After that I need to add Retention , for theRight canine what clasps should I put here ?*We cant place an I -bar ( the depth ofsulcus in that area is 3 mm ) .I could use :

1-Gingivally approaching cast clasp ,2- Occlusally approaching cast clasp3-Occlusally approaching wrought wire (combination clasp ) . The doctor went with Occlusally

approaching cast clasp , although itsinferior esthetically than gingival but Ican t put the gingival due to the depth .-Choosing the wrought wire option is thesame as occlusally approaching c-clasp ,both are unesthetic so it doesnt make any

difference but the doctor went with the c-clasp. (fig. 4).- SO CIRCLET CLASP

OCALLUSALLY APPRAOCHING IN 0.25 MM MESIO-FAICALUNDERCUT .

-On the Left canine because I have 6 mm depth , Ican add an I-bar .Note to remember about the I-bar is that theretientive tip ( arrow ) of the I-bar must be on themesio-facial of the tooth . (fig. 4) .SO I-BAR IN 0.5mm in MESIO-FAICALUNDERCUT

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For the 7 th on the right : -Can we place a c-clasp on the molar ? No. so were going with the Wrought Wire-You need to stay 1 mm away from the tooth and you need to fuse it with themeshwork (fig. 4) .

SO WROUGHT WIRE 0.8 DM , IN 0.5 MM DB UNDERCUT .

Lets see if we need indirect-retention in this design ? anytime you see two orthree points clasp assemblies know that youre going to need to place indirectretention

We look for the axis of rotation away from the tissue and toward the tissue .

Lets start looking for support :

(fig. 5 ) if the other side ( where there is no pen ) triesto come out whats going to prevent it ? The directretainer on the left canine .(fig. 6 ) What if the other side ( where there is no pen )tries to come out ? both the canine and the 7 th on the rightside will prevent it from doing so .(fig. 7 ) What if the other side ( where there is no pen )tries to come up ? the 7 th on the right will prevent it .

(fig. 8) What if the other side where there is no pentries to come up ? I have nothing to prevent it ! because theyre grade ll mobility I cant put directretainters on the 8 th and 7 th on the left .HENCE this is one of the special cases where I have aclass 3 but in terms of retention its class ll ( as if the7th and 8 th dont exist ). So I need indirect retention ,luckily I have a retainer on the right canine , so Im going

to mark it green to indicate that its an indirect retainer. ( fig. 9 next page ) .

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For the major connector were going withthe mid-platatal strap .

** On the right canine and the left canine I

already have repcorcaiton provided by therest , we could draw the major connector asfig. 10 .OR I could draw it like fig. 11 in which the

strap extends to the rest , as long as thedistance in square 1 is grater than 6 mm and I dont have a minor connector blocking the way as in square 2 figure 11 , samething applies for the right canine . (fig 12 shows both of the ways ).

(fig.13 ) Now continuing putting the Mid-platal strap posteriorley , you cannotice in square 1 Ive added a reciprocating arm to make the design as simple as

possible and not to extend the palatal strap into the whole tooth. As in fig.14

The 7 th and 8 th on the left are grade 2mobility , and in the upcoming years theymight need to be extracted , so i make thestrap to cover them so that in the future I can

just remove them and add acrylic teeth ( like pieces of lego ) (fig. 15)

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**W ell do also the Lower design .- In the lower as youll see the 8 th on the right is grade lll and there is BOP , so itneed to be extracted , but Im afraid if I did this the upper 8 th might supra-erupt ,whats the solution ?

- Ill add a Rest ( preventing supra-eruption) and extend the Strap just in case theright 8 th needs to be extracted .(figure 16 and 15).

SO AT THE END OF THE DEISGN WE DISCOVERED THAT THISDEISGN IS TOOTH-TISSUE SUPPORTED.

Now well discuss the lower for this case.

-We start as always , coloring ourAbutments with the color yellow (fig.17).

After that I add Support (fig. 18).

After that Ill add Minor connector , forthe left side Ill put a Lattice , but thelattiace Im going to add is called

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Modified lattice in which each tooth has its preserved location so that when thetechnician add the acrylic he knows whereto add them exactly .(fig. 19).

For the right side Ive added a metal base since I only have one tooth missing( fig. 19).

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Looking at figure 20 ( previous page ) , we needto add retention now:**Left side :-For the molar we added a normal occlusally

approaching simple circlet C-clasp .- For the left canine weve added an I-bar/RPIsystem ( because the depth allows us to do so ) and on the**Right side :-For the Premolar weve added a simple cast clasp( We cant add an I-bar here due to the depth which is

3 mm ) .

-For the Molar weve ad ded a ring clasp with a distalRest to enhance retention .

-Notice in fig. 20 also that the reciprocation arms aredrawn for the clasps ( for the left canine we didnt

provide a reciprocation arm because the function ofreciprocation can be done through the rest on thecingulum or through the major connector like plate ) .on the right molar there is a Ring and the ring provide its ownreciprocation as you already know .

-Fig. 21 , its tim e to make a Lingual bar .If we dont have distal rest we can draw it like this (figure 22).

-Now for the Anterior teeth theyre grade 1 , ll mobility soits best to plate them with the major connector , but whatabout the left premolar ? should I plate it or leave it ?Looking at figure 23 its not a good idea to not plate it andleave this space below the premolar , its not good forhygienic and health ; its not self -cleansing.

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Now what about the right side ? from 3,4 and 5 ? should I plate them or not ? youhave the freedom to either do figure 24 or plate it as figure 25 ; next page.

figure 26 shows the final design for both theupper and lower for case 1.

26 A.

26 B.

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-THIS FOR THE UPPER CAST

Figure 27 Kennedy class lll . its Tooth -supported ( FOR NOW ).

We start always as usual by coloring theabutments with the color yellow . (figure 28).

To be honest with you if we have this patient inreal life well do him either bride or implants whenwe have UNILATERAL WITH ONE OR TWOTEETH MISSING WE TEND TO MAKEFIXED TREATMETNS .-Ideally class III design is quadrilateral so Ineed to mark 2 more abutments ALTHOUGHthere is no edntoulues area on the other side wheream marking the 2 extra abutments .-I like the design to be symmetrical so Ill markthe same teeth on the right side. As in figure 29.

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Next were going to draw a Meshwork as in fig.30 .But just a side-note : **IF YOU HAVE A ROOM LATTICE**IF YOU HAVE LIMTED ROOM MESHWORK

.

-After that were going to add Rests as in fig.31.

-After that were going to add Retention as in fig. 32.

-Notice in fig. 32 all of them are OccllusallyApproaching C-clasps .

-Finally for the Major Connector were going to use

Mid-palatal strap as in fig. 33.

-Now looking at the design and all these clasps , I askmyself can I make the design more simpler ? well I canas in fig. 34 and fig.35.

-In fig. 34 , I could place a Clasp on the 6 .- In fig. 35 I could make a Double Embrasure with the 6 and 5 .

-But the most correct design is figure 32 the firstone .

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333435

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-Now lets solve the Lower for case 2.

-What class is this ? 1 or 2 ? well to

determine so you have to look for theopposing arch ,

looking at figure 33 you can see that 8 th and 7 th on the right side are there .A. If Im not replacing the 7 th and 8 th and If Ihad a rest on the 8 th to prevent it from supra-eruption than this is class 2 ! But:B. Since I have teeth and the 8 th might supra-

erupt its class 1. So its good idea to replacethe lower right 7 th and 8 th .

-So we start as always by coloring theAbutments yellow . as in fig. 37.

-After that Im going to add the MinorConnector as in fig. 38 , notice that theminor connector on the right side behind that

6th

is a Modified Lattice Work .

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-Af ter that lets add Retention , we need aStress-Releasing design ( RPI, RPA ,CC ) .fig39

-After that Im going to add the Major Connector as in fig. 40.-Remember when we did wax pattern inthe lab ?**Those of you who worked with lowermodels had to make triangles in the 5thand 6 th these triangles are to help connectthe plate ( major connector ) with thelattice ( figure 40).

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Done by : Osama Yousef.

CORRECTED BY:Gewanna Ghazal

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