Crown And Bridge 5

‫بسم ال الرحمن الرحيم‬ ‫)اللهم إني اسالك علما نافعا ورزقا طيبا وعمل متقبل‬

) First of all, I will like to say that I put in slide no (15) in the last lecture (inversely) please change it to proportional. Back to last lecture, the last few slides I did not talk about them, last lecture we talk about preservation Of tooth structure, resistance and retention and structural durability.

{Please refer to lecture slides} Today, we will talk about marginal integrity and there will be separate lecture for the last principle (preservation of periodontium). •

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Finish line: is the line where the restoration meets the preparation. I told you about cavosurface line angle, when you prepare class1 or 2 there will be cavosurface line where the restoration meets with the tooth structure and this is called finish line. The restoration must closely adapt to the cavosurface finish line of the preparation. The configuration of the finish line will affect the bulk of material, adaptation, seating, and aesthetic.

Back to physics and maths, when you prepare your preparation ,your tooth and you want to seat your crown ,the crown wont seat perfectly 100%(‫مش رح ينزل‬ ‫ تماما على‬preparation), the reason is when you prepare the tooth , you make an impression ,send it to the lab , pour it in stone , fabricate the restoration . All these steps have 1

its own inaccuracies (‫ يعني كل وحدة عندها‬inaccuracy ‫)تبعها‬ eventually, your restoration won’t seat perfectly in your preparation. This imperfection in your work will express itself as space between the restoration and the tooth structure, which is called (D) and this (D) : is the vertical discrepancy between the preparation seat and the restoration margin , this D isn’t the closest distance between the preparation and nearest point of restoration ‫ ) يعني هاي مش اقرب نقطة بين‬tooth structure and restoration ) There is closer point which is (d) {‫ } تذكروا الرياضيات‬if you have restoration with a sharp angle , this sharp angle let says (m) , if you draw a line downward from the sharp angle of restoration down to the finish line at point (p). ‫ هاي الزاوية الها تناظر بالرياضيات‬then m= m (down) Then the sharper the restoration margin, it will be the less the angle. )‫ يعني كل ما كانت‬restoration margin(‫انحف‬ ‫بتقل الزاوية‬ Then less the angle, the less sin ‫)) بقل جيب الزاوية‬ Sin (m) = d/D (‫)الوتر‬. If you want to calculate (d) then d = D * Sin (m), so the sharper the restoration, the less d. In this scenario, the sharper margin , you have better fitting of your restoration , theoretically , because (d) is less than D(distance ) , every time you prepare sharp margin , you have (d) smaller . Then, if you go to your margin, less flat your margin you prepare, it will be less fitting.) ‫ كل ما كان عندك‬Margin closer 2

to zero like in picture (b) then D = d because m=0 so Sin (0) = 1 All this talk about the configuration of your finish line:The sharper the finish line, the better seating of your restoration. If you go back to shillingburg, there is another problem it isn’t only the geometry of the finish line which determines the final seating of your restoration, there is another factor, what we place inside restoration before you place it? Cement, the hydrostatic pressure of your cement, do you know what is hydrostatic pressure? ‫) يعني لو بدك تضغط اشي لتحت على‬fluid it has resistance to push it upward. ( and it is called hydrolytic pressure incase of water. - The hydrostatic pressure will prevent the seating of your restoratation, then to make it easy (cement ‫)انها تنزل بوجود‬, you need something called venting (vent means ‫( تهوية‬, you need something to let the cement to go down. Why does hydrostatic pressure happen? Because you put extra cement inside the restoration and when you seat it, this extra cement, how it will express itself? Hydrostatic pressure ‫عشان تخلص من‬ ‫ يطلع لبره‬cement ‫ بخلو‬Vents ‫ يعني‬leakage area ‫بدك‬ Do you remember when you take removable prosthodontics, you took vents in investment for wax up, and when you make vents to let the air go out when you make casting, the air will leak out.

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This vent is better in flatter preparation because when you have flat prereration, the cement will be easier to flush out than if you have sharp preparation. If you lute restoration on C imagine distance of escape that the cement will go out, this exit area is more horizontal and big. It is easier to seat the restoration, when the margin is flat, and it is better seating for the restoration when the margin is sharp provided, you don’t have cement. There is no significant difference actually in accuracy of restoration fitting because of geometry of finish line , the reason is the finish line geometry , sharper better ,but the sharper , the less the seating of cement . From now on, if you have been asked by somebody, what is the best margin for the restoration? There is two things, before cementation the sharper, the better / but after cementation, there is almost the same. There are other factors later on; we will talk about them and this which tells you what to choose. Other than fitting of restoration .now, when you prepare your tooth, you end up with finish line and this finish line is the area where the restoration meets the tooth structure .

Finish line configuration

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If you look to a the white material is porcelain, the gray one is metal. We have 5-6 finish lines:1. knife edge (d in the picture) :Least common restorations marginal finish line we do. In knife edge pattern we have narrow margin compare to other finish lines so we need strong material because if you don’t use strong material this material will be weak so it will break up. This finish line goes with metal because it’s strong.  The knife edge problem is you can’t pick it up easily in your impression. If you take impression for knife edge and you pour it you can’t determine your finish line, so knife edge it is difficult to pick it up easily in your impression and it is difficult to make technician see it probably so the technician won’t be able to fabricate a restoration in the knife edge finish line. Now the more the material you have the better strength you have the better structural durability. 2. Chamfer (e in the picture): Better thickness which is about .5 - .7 mm more than knife edge so it’s excellent finish line for metal restoration.  Gives you excellent structural durability if you use metal.  More destructive than knife edge. 5

 Easy to pick it up in your impression. SO if you have full metal crown restoration your finish line should be chamfer by default. 3. shoulder (a In the picture) :Now we start talking about two materials together metal and ceramic, there is no problem about cross section if you fabricate metal round cross section or sharp cross section, the structural durability wont be affected but in porcelain the best resistance is given by compression so your porcelain should not be ended at knife edge if its end at knife edge there will be shear stress, there will be tensile stress and porcelain will chipped out or chipped off the restoration. Now if you have porcelain you need to think about the geometry which let you have an even floor for the restoration which is called shoulder.  in shoulder its about 90ْ cut shoulder preparation so your porcelain is not ended like a sharp edge like the metal in the knife edge , in the knife edge there is NO problem for metal because it wont break up but it is difficult to fabricate it in the master cast BUT in shoulder if you have sharp edge the porcelain once you cement it after a couple of days it will be broken, the reason porcelain need compressive force to resist if there shear or tensile force the porcelain will be broken . IF I tell you, you have metal-ceramic crown your default margin is Shoulder.

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 Cross section must be flat otherwise porcelain will break. Until now we talked about knife edge, chamfer, shoulder, we don’t talk about one more thing which is the internal angle of your restoration. The internal angle of the finish line you see where the arrow is (the arrow in a), this is the internal angle. Now if you have sharp edge if your internal angle is perfectly 90ْ then you will have a sharp edge at the cavosurface angle. In picture a internal angle not absolutely sharp it’s slightly rounded not 90ْ. now if you have 90ْ cut that means your shoulder at one margin of your internal angel will be sharp , this sharp pit will break up because this is stress point ,so all shoulders if you create shoulder we round the internal angle then this more or less conventional shoulder ,the angel not 90ْ but very close . If you look to the right side this is called radial shoulder. RADIAL SHOULDER: it is shoulder finish line but its internal angel is very rounded to avoid stressing porcelain. METAL we can make it at any finish line but we avoid knife edge because it is difficult to create it in the lab.

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PORCELAIN we cant make it at any finish line you need flat top to seat at it , if its not flat top porcelain cant seat, its become stress point, stress point will fracture this is applied into two things :1- Finish line must be flat. 2- Internal angle should be rounded. In porcelain we can do radial shoulder, conventional shoulder, heavy chamfer (we can use it in metal ceramic crowns as well) which is close to radial shoulder. AGAIN , metal could be ended at any finish line. Porcelain ended up as shoulder, radial shoulder, heavy chamfer, or any modification for shoulder but we need shoulder with rounded internal angel. For full metal crown we make CHAMFER. For metal-ceramic crowns the side which has metalceramic SHOULDER, the side which hasn’t ceramic we use CHAMFER. All-ceramic crowns we make SHOULDER , in all-ceramic all sides surrounded by ceramic so we need flat top all the way around with round internal angel ,also we can use heavy chamfer or any modification any finish line accept porcelain we can make all-ceramic on it. Where we use metal-ceramic crown? We use in an aesthetic area then your shoulder should be in a visible area so your shoulder should be labially and slightly interproximally. When we use metal-ceramic crown in molar (like 7) I end up only in labial shoulder the rest will be chamfer (the rest I cover with metal). 8

Doctor doesn’t want to use the way of shillingburg, shillingburg talk about finish line in complex way. Q:-WHAT IS THE DIFFERENCE BETWEEN SHOULDER AND HEAVY CHAMFER? A:-in shoulder the cavosurface angle is perfectly 90ْ in picture a not the internal angle. The contact between porcelain and tooth structure nearly 90ْ. If you look to chamfer cavosurface angel not 90ْ it’s slightly obtuse. In picture b or c the metal also visible although you put porcelain then there will be a ring of metal around the tooth, if you look to heavy chamfer there is metal substructure at the finish line and above it porcelain . Then if you imagine a crown all around the tooth it will be a little ring of metal like in picture b that means I can’t use it in aesthetics area .SO when I told you I have heavy chamfer so I can’t use it in central incisor. But you can use heavy chamfer in lower incisors if it allows you. Metal shown or porcelain shown here we have to talk about aesthetics. Preservation of periodontium it will be in a separate lecture. Where do you think its better adaptation without cement with knife edge or shoulder? Of course knife edge because it’s very sharp. BUT when you use cement they are almost the same ,there is multiple studies but they almost the same . 9

BEVELIED SHOULDER:-it is standard shoulder with 45 ْbevel like what we make in composite we use it somewhere(not important we don’t make them) ,its problem like deep chamfer there is metal band beneath it ,so not accepted aesthetically. Mid exam questions will come from lectures and shillingburg . ‫موسى حكى انه بحط أسئلة المتحان بعد كل محاضرة وبيكون متذكر شو‬.‫د‬ ‫حكى بالمحاضرة بس المحاضرات مش كافيه فيه أسئلة من الكتاب‬.

Full veneer crowns(FVCs):Do you know what FVCs is? What’s the meaning of full? Full means surround the whole tooth structure. Doctor gives this topic because :It is very common to prepare full metal crown and it’s the only retainers we use in fifth year . Background: FVCs • They have a high success rate and the reason because they are surrounding the whole tooth structure, when we talked about treatment planning when I make plastic restoration or inlays or onlays or extracoronal (crown) we choose according to tooth structure. Now FVCs is surrounding the whole tooth structure then the success rate definitely is higher than the rest. 10

Second thing if someone calculates the finish line mesiodistal, buccolingul then finish line distance less than I make MOD onlay. Finish line shorter ,the shorter the finish line the less the chance of complication. High retention and resistance than 3\4 crown the reason the more the surface area, the good geometry , more parallism. • A must in small teeth if you deal with small teeth like lower incisors you don’t fabricate 3\4 crown because they are very small teeth or for bridge retainers. What’s the best thing for retainers? FVCs • They could be metal ,metal ceramic ,or all-ceramic crowns. •

Full metal crowns (FMCs) o Used in posterior teeth. o Less destructive preparation than other FVCs o More conservative than other FVCs. For FMCs what is your finish line ?it is chamfer thickness .5 - .7mm , if I make shoulder 1.2mm then which more conservative of course chamfer, the occlusal reduction 1 -1.5 mm then its less than metal-ceramic which is 1.5 -2 mm so FMCs is more conservative preparation . o the same indication as other FVCs(these indication from lecture 2) 11

• • • • • • • • •

Heavily restored teeth. Primary trauma. Tooth wear. Hypoplastic condition. To alter shape, size, or tooth inclination. To alter occlusion. Appearance. Non vital teeth. Combined and others.

o Contraindication can’t be used anteriorly, not used in aesthetic area. Metal crowns actually they are rarely used because it is cheap but in our centre Dr.mousa make it he don’t have any problem in it ,it is good for whom want to work correctly and it is very conservative, structural durability very high. Finish line is chamfer which give: I. Good geometry for adaptation. II. Good vent for cement. So chamfer is very good finish line.

Preparation for FMCs:I. The same principles of last lecture apply. a. Preservation of tooth structure. b. Resistance and retention. c. Structural durability. d. Marginal integrity. e. Preservation of periodontium.

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{ last lecture please read it carefully} II. 1.0-1.5 mm occlusal reduction. III. .5-.7 mm axial reduction. *in shillingburg there is another interim how to create these but you don’t have to read it. IV. Chamfer finish line is the regular finish line which we use. V. Auxiliary feature (grooves, boxes, pin holes) could be added when you require it. This is a diagram or a picture about preparation of upper and lower FMCs 0.5 finish line,0.5-0.7mm is acceptable, occlusal reduction 1mm at non functional cusps, 1.5 mm at functional cusps, if you look to the right side the occlusal bevel. the morphology of the occlusal surface is the exact copy of the original morphology to create equal distance for the fissure, for the pits, for the cusps.

Metal-ceramic crowns (MCCs):This is very important, this is the most common restoration you will used, this is the most retainers you will use, the metal ceramic restoration became commercially available by the late 1950s. MCCs combine the natural aesthetics of a brittle material such as porcelain with the durability and marginal characteristics of a cast metal restoration. Now why we do MCCs? 13

A.Aesthetics very important because you have ceramics. B.We use metal for strength. If you use full ceramic you will scarify more tooth structure. Full metal crown the least preparation you need, the most conservative one. metal-ceramic crown a little bit more destructive than full metal crowns ,it become more destructive in the area where you need ceramic over metal ,if you have central incisor you place your porcelain labially , in the incisal edge, and slightly go into interproximal area all these areas need shoulder, heavy chamfer ,or any modification could carry porcelain . The preparation usually about 1.2 mm then we start rising up our destruction. 0.5-0.7 mm for metal. 1.2 For metal-ceramic crowns. MCCs were the most frequently prescribed extracoronal restoration under the general dental services in England and wales. More than 1million units per year are usually fitted at a total cost of more than 1million to patient and provider. You can imagine in one year 1 million metal ceramic crowns are made, the total cost of 100 million ‫إسترليني‬this number to imagine how common this restoration is.

Advantages of MCCs: Strength because of metal. 14

 Durability because of metal.  Used as retainers (because its full coverage, it covered with metal) for anterior (because of porcelain) and posterior FPD.  Cheaper than all ceramic restoration. More expensive than full metal crowns, cheaper than all ceramic crowns, more cosmetic than FMCs.

Disadvantages of MCCs:• Destructive compare to FMCs (in porcelain areas to avoid overcontouring). • Less satisfactory in aesthetic point of view than all ceramic crowns. • Subgingival margin anteriorly. What ever the skills you have, finish line when you have metal and ceramic the porcelain wont reflect light probably as porcelain by itself, porcelain is glass ,if you put glass and put behind it curtain black it wont reflect light as if glass by itself (matt glass ‫) عملته حتى لو‬ Porcelain while metal behind it won’t reflect light probably, so it won’t match the aesthetic perfectly. The most obvious area you can see this is the margin (cavosurface angle where crown meet tooth structure, porcelain wont reflect light well) so it gives artificial look. To overcome this problem we need to place our margin subgingivally. We need subgingival finish line in metal-ceramic crown although we have porcelain top on the metal. 15

We don’t need that at all ceramic crown. • More expensive than FMCs. Indication of MCCs:-as other types of crowns (as mentioned before)

Contraindication:Active caries: we don’t place fixed prosthesis in active carious tooth. b) Untreated periodontal diseases. c) Highly aesthetic demand. The first two contradictions applicable for all FVCs. a)

If you have 25 years old lady unmarried, journalist I don’t think metal-ceramic crowns is appropriate choice we need more aesthetic which is all ceramic crown. d) Age. Fixed prosthodontics is contraindicated in young child why? Why we can’t put metal ceramic crown for a 10 years old child? 1. Because he still growing. 2. Encroach the pulp because pulp is quit big. So we have two problem growth and pulp so we can’t make fixed prosthesis for grower child. How the metal bond to ceramic this is very important. You have:-

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 Mechanical interlocking.  Van der waals forces: initial bonds.  Compressive forces: due to difference in the coefficient of thermal expansion.  Chemical bonding: oxide layer, the most important. Now, the most important is the Chemical bond, the bond between metal and porcelain occur by something called oxide layer, this oxide layer incorporate from the porcelain and from the metal this is important, this is very strong bond. You can imagine if you try to fracture metal ceramic crown, the porcelain will fracture at the middle before the bond broken between metal and porcelain, in other word in metal ceramic bonding the Chemical bonding is stronger than the cohesive bond. Compressive forces: - we have physical properties, the linear coefficients of thermal expansion. Every material if you heat it 100 ْor cold it. When heating material will expand according to the properties of the material. Now when you fabricate your metal-ceramic crown ,the technician fabricate the metal core first of all then he start applying porcelain and then he fire it up in oven .now if you have a big discrepancy between the coefficients of thermal expansion of ceramic (aC) and metal (a M). Let say your heating temperature is about 900ْ for porcelain then 900ْ will expand the metal a little bit if the metal expands more than the porcelain then what will happen? it will fracture. Then we need close difference of coefficient of 17

thermal expansion of ceramic and metal and that could be adjusted for METAL usually we use BASE METAL ALLOYS. PORCELAIN adjusted by FILLERS, increase filler change the coefficient of thermal expansion. Generally the ideal difference is 1.0 factor of coefficient of thermal expansion 1-1.5 is acceptable. Typically aM value range from 13.5-14.5 *10^-6/C; a C value range from 13.014.0*10^-6/C. PORCELAIN must be LESS than METAL. If you have metal and porcelain, temperature 900ْC, if you cool it down to zero, what is going to happen? The metal will shrink, if your porcelain shrinks more, what is going to happen? If your porcelain shrinks more, means that porcelain will slide more in metal and make compressive force with metal; this is what is called the compressive bonding. - Chemical bonding and compressive bonding are obvious, intermechenical locking is very easy, van der Waals forces between any 2 bodies, there is van der Waals force. The preparation for MCCs, the same principle applies , it is a combination between metal and porcelain , if it is a combination between metal and porcelain , then you are imagining one of the margin will be chamfer because it is metal and one of the margin will be the one which could carry porcelain , which is heavy chamfer , shoulder, beveled shoulder .

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So it is combination between metal and porcelain, the metal covers all around the preparation, but the porcelain covers the metal substructure in the visible areas. (When you make MCCs, all the preparation will be covered by metal, but esthetic or visible areas will be covered by porcelain).

Anterior MCCs features:• 2mm incisal reduction, but how much for FMCs? No, we don’t use it in anterior teeth. • 1.2 mm axial reduction labialy, the finish line of FMCs was 0.5- 0.7 mm, and this is 1.2 mm, so it is more reduction. • The line should pass lingually to the contact point. When you prepare shoulder, you need to pass it 1mm lingually. You prepare the whole labial, then you go interproximally, you should pass the contact point 1mm lingually. ( ‫ وبتوقف للخلف‬mm1 ‫ بتعديها‬Contact area ‫ بس تصل ل‬shoulder ‫) لما بتحضر‬ Where is the contact area anteriorly (I mean where is the contact area between central and central)? Cervicoocclusal more incisally (between mid 1/3 – incisal 1/3), but buccolingually, it will be more labially.

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As you go posteriorly, the contact area will be more lingually, that’s why you need to cross (pass) the contact area anteriorly; while in posterior teeth, you don’t cross contact point 1mm, but you have to stop; because it is already away lingually.

Posterior MCCs features • Why do you have 2mm incisal reduction (we cut 2mm symmetrically from the whole incisal edge) while in posterior teeth, you have to cut 1.5- 2mm? Because of functional cusp. The whole incisal edge in excursions is stop, means that the whole incisal edge has load; so it is functional cusp. ‫ لما يحرك أسنانه‬contact ‫يمكن يجي عليها‬, load ‫ عليها‬incisal ‫كل‬ ‫)معناه‬ In posterior teeth, the non – functional cusp get less load than the functional cusp; that’s why we prepare functional cusp about 1.5 mm. • 1.2mm labial reduction is the same in posterior and anterior teeth, just lingually to the contact area, we prepare shoulder just lingually, but in anterior teeth we prepare to 1mm lingually. 0.7mm reduction with chamfer finish line again and this applicable in anterior and posterior for the non- visible areas. ( 0.7mm) metal)‫ الي ما بتبين بنحط فيها بس‬area ‫يعني‬ ( If you look at anterior teeth , you have your shoulder finish line about 1.2mm and this 1.2mm is combination 20

(roughly 0.5 mm for metal and 0.7mm for porcelain) ,so the total 1.2mm , incisal reduction roughly 1.5 mm or more about 2mm . - Lingually less 0.5 – 0.7mm, the area of 1mm, you will take details about it in (labs), this area is called centric stop. ( ‫ بعض عليها فبنزيدها اكثر‬, ‫) لما المريض بعض‬ If you look at posterior, we cover mainly the buccal surface, we don’t need to cover the occlusal surface always, but we do need it sometimes. For example:-If you have first premolar, you will cover the occlusal surface; because it is visible. - If you have lower 7, you don’t need to place occlusal porcelain; because it is invisible. If you look at the labial surface, the preparation is shoulder with reduction 1.2mm, but the lingual is chamfer, the junction between them is shoulder –stepchamfer and this is called wing junction. • The left hand sided, the top one is the labial side is prepared by shoulder bur, so you have 1.2mm reduction with flat finish line (shoulder finish line). •

the lingual in the right hand sided , it is metal , so the finish line is chamfer ,with reduction about 0.7mm the junction between them , one will be 0.7mm and the other will be 1.2mm then there will be step and this step is called wing .

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Back to structural durability, we talked about something called offset which connects 2 structures together; do you think this area strengthening point or weakening point? Strengthening point; because it is the junction between thick and thin, so this one is going to be strong, stronger than lingual, but weaker than labial, but it is strong point, it is a reinforcing struts (trusses) ) 2 grooves ( ‫رح تعمل كأنو رابطين‬ The end of shoulder should be 1mm lingual to the contact area because the contact area is very labially placed in anterior teeth, if you finish your shoulder at the contact area, the metal will be visible when the patient smile. So, you need to cross contact area 1mm lingually to end up your shoulder. In posterior teeth, the contact area already going lingually, so you don’t need to cross the contact area 1mm and stop your shoulder finish line, you should stop it just lingually, just at the contact area; because it is less esthetics and the contact area is already lingually. Why we don’t do the whole restoration (preparation) with shoulder? Because it is destructive.

All Ceramic Crowns

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When we talked about tooth preparation, we focus that we prepare teeth for 2 reasons, First, preservation; we don’t need to cut unnecessarily. Second, we need structural durability. If you have metal posterioly, and 0.5mm is enough for it, why to prepare 1.2mm? • For this reason MCCs are more conservative than all CCs; because all CCs, we prepare full shoulder all the way through. • All CCs are the best cosmetic effect of all FVCs, why? Because there is no metal, it is mainly for anterior teeth, we could use them for posterior teeth, but mainly for anterior teeth. • -It is weaker than other FVCs, why weak? Because, they are porcelain, porcelain is brittle material by nature, but reinforced by resin cements and all ceramic crown restorations we cement them with resin cement, all FVCs and MCCs are cemented with conventional cement or resin modified glass inomer cements. Now, if you have resin cements, if you bond the crown to the tooth by resin, do you enhance resistance, retention and stability? Yes, you do. Do you enhance the strength of material? Yes you do. The reason is with resin cement , you are working in micromechanical spaces , the restoration more or less becomes part of tooth structure , because bonding area that we use resin cement is very strong and this is to 23

justify why resin cement enhance the strength of your porcelain . It will be more conservative labially than MCC, why? Because we don’t need metal, just porcelain, but more destructive because you prepare full shoulder (lingually shoulder). • More destructive than other restoration except the labial margin or esthetic area in MCCs because you prepare it 1.2mm. • They cause tooth wear more than other FVCs, why? Do remember when you take dental material that porcelain is very abrasive material, so if it is very abrasive, it will cause more teeth destruction, more than other material. • With all advances in ceramics, all – ceramic bridges are still limited to certain scenarios. (When you prepare bridge from ceramic, there is a limitation but it isn’t important to know them.) • Occasionally, used in molar teeth, you can do all ceramic crown restorations or FVCs in posterior teeth, but usually, we do them in anterior teeth. The preparation is full shoulder , thickness about 1mm , incisal reduction 1.5- 2mm , labialy 1mm ,MCCs are destructive labially 1.2mm , lingually 1mm , but MCCs 0.5 mm (because it is chamfer ) are more destructive lingually or palataly .

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The last thing is porcelain laminate veneers (PLVs) (Indications ‫( الدكتور حكى ما بدنا ندخل بالتفاصيل المهم تعرفوا‬ • A thin layer of porcelain used in the anterior region to correct :(indications ):A-Colour. B- Mild mal- alignment. C- Small teeth. D-Chipped or traumatized teeth. • Very conservative, thickness about 0.5mm labial reduction, so, you don’t do anesthesia, because we prepare them in enamel. If you don’t go into dentine, you don’t need anesthesia, but in cons clinic, never do class 1 or 2 without anesthesia. • No jags or temporaries because one of the advantages to make temporary restoration for tooth is to prevent pain and for esthetic, because this is 0.5mm don’t affect. • Usually over contoured and expensive. The preparation, if you look at left hand sided, very thin margin, very conservative and esthetic demand very high. Please remember that all figures given in regard to tooth reduction for different restoration types could have slight differences between one reference and another.

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Dr. Saied that there is a range differs between one book to another; there is no significant difference between them.

Done by : ‫دعاء العودات‬ ‫ايسر طشطوش‬

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If you have you cool it d The metal w what is goin means that 27

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