Replacement of defects of dentition metal prosthetic dentures. Clinical and laboratory stages of production of prostheses with oxide and without oxide materials
This invention relates to a method of making crowns, such as gold crowns, for teeth, and a method of making a form for use in making such crowns by an investment casting technique.
The conventional technique for producing crowns, such as gold crowns, utilises an impression which is made by the dentist in a hardenable resilient material such as a hardenable rubber composition. This impression will include an impression of at least the teeth surrounding the one to be crowned and will also include an impression of the decayed tooth which has been ground down by the dentist in preparation for crowning.
This impression is then utilised, usually by a dental laboratory, to produce a crown. A plaster cast of the stump remaining after the dentist has ground down the decayed tooth is produced on a brass pin and a model of the teeth in that jaw is also cast in such a way that the stump can be removably located in it by means of the brass pin.
The next stage of the process is to cast a layer of wax on the stump and to carve the wax by hand to give the external shape of the desired crown. The carved shape will generally be such as to be compatible with the other teeth. After carving, a rod of wax, generally referred to as a sprue, is attached at one end to the carved wax and at the other end to a conical wax reservoir.
This assembly can then be used to produce a mould which is achieved by casting in an investment casting ring a heat-resisting investment compound with the wax reservoir at the base of the ring. When the plaster compound is set hard it is heated in a furnace to remove all the wax and subsequently a gold crown is cast by introducing molten gold through the sprue into the mould cavity formed by the carved wax.
The specification for US-A-3,058,216 discloses a method of fabricating a porcelain veneer crown. In accordance with the method described in this specification a pre-formed crown form is fitted over a stump of a tooth and impression material is introduced into the crown form in order to make an impression of the stump.
The external surface of the crown form is then ground using a grinding stone until it matches the surrounding teeth in the mouth.
An investment casting moulding may then be produced from the crown form, from which a crown can be cast in the investment casting mould.
According to one aspect of the present invention there is provided a method of making a crown for a tooth such as a gold crown comprising;
· forming a sheet of formable material into a crown form having the desired shape of the crown;
· producing an investment casting mould from the crown form and burning out the crown form; and
· casting the crown in the investment casting mould.
According to another aspect of the present invention there is provided a method of making a crown form for a tooth such as a gold crown, for use in an investment casting technique comprising;
· (a) forming a first sheet of formable material to a shape which approximates to the desired shape of the crown;
· (b) disposing the formed shape around a layer of deformable hardenable material;
· (c) applying a compressive force to the formed shape to deform the underlying hardenable material to the desired shape of the crown;
· (d) hardening the hardenable material to produce a crown form precursor;
· (e) removing the formed shape from the hardened crown form precursor; and
· (f) utilising the hardened crown form precursor to form a second sheet of formable material into a crown form of the desired shape of the crown.
Preferably in step (b) the hardenable material is applied between a cast model of the tooth stump to which the crown is to be fixed and the formed shape.
Desirably the assembly of the cast model of the tooth stump, hardenable material and formed shape is disposed in a model of at least the teeth surrounding the tooth to be crowned and the compressive force of step (c) is applied to the assembly by means of a model of the occluding tooth or teeth in the jaw opposite to that in which the tooth to be crowned is situated to deform the underlying hardenable material to the desired shape.
Preferably the method further includes the steps of:
· (a) producing an investment casting mould from the crown form of step (f) and burning out the crown form; and
· (b) casting the crown in the investment casting mould.
Conveniently, the first sheet is formed by means of a deep-drawing technique. The second sheet may also be formed by a deep-drawing technique.
Advantageously, additional material is added to the second formed sheet in order to produce the final desired shape of the form. Preferably the additional material is wax.
In one method according to the present invention a plaster model of the teeth in one jaw and a plaster cast of the stump of the tooth to be crowned is produced in the conventional way. An artificial tooth is then chosen from a selection of stock teeth to match approximately the remaining teeth in the mouth. Supplies of such stock teeth are readily available as they are used in the preparation of dentures. When a stock tooth of the desired shape is selected it is used to make a first plastics impression in a sheet of formable plastics material. This can be effected by a process known as deep-drawing in which the sheet is heated to a temperature at which it is formable and the stock tooth pushed into it. Usually a backing of a deformable material which will control the forming of the plastics sheet is employed for this step.
The first plastics impression, which is a female mould of the approximate shape of the desired tooth, is then cut from the sheet of plastics material filled with hardenable material and pressed on to the plaster cast of the stump. The stump is then inserted in the model of the teeth in that jaw and a model of the teeth in the other jaw impressed upon it so that the occluding tooth on the opposite jaw can depress contacting areas of the plastics impression. The hardenable material is then allowed to harden on the plaster cast of the stump.
The plastics impression is then removed and discarded and any excess of hardenable material around the margin of the stump is removed to give a smooth surface. The smooth hardened material at this stage is in the shape of the desired crown but is smaller by an amount governed by the thickness of the material of the first plastics impression, and is referred to herein as the crown form precursor.
The crown form precursor is then used to produce a second plastics impression by a method of deep-drawing as described above. The plastics impression so formed will have the desired shape of the crown to be produced as it has been derived by way of the crown form precursor from a selected stock tooth and has been adjusted for occlusion.
This impression is then cut from the sheet placed over the cast of the stump from which the hardenable material has been removed and the margins filled with wax of a type which is normally used for the investment casting process. Thus, in the region of the margin there will be a wax coating but in the remaining region of the impression there will be layer of shaped plastics material which will be spaced from the casting of the tooth at least in certain areas thereof. The plastics impression together with the wax margin is then removed from the cast of the stump and provided with a wax sprue and reservoir in the conventional manner. The sprued crown form of wax and plastics material is then used to produce a conventional investment casting mould and the gold crown cast in the normal way.
The process described above has two marked advantages over the conventional method of producing gold crowns. Firstly, the amount of time taken to produce the crown is considerably reduced particularly in view of the fact that it is not necessary to carry out any carving of a wax coating on the cast of the stump; this carving is both skillful and very time consuming.
Secondly, the thickness of the gold crown is governed only by the thickness of the plastics material which is used to form the impression. Thus, a much thinner crown can be achieved with the attendant saving in the amount of gold employed. It will be seen therefore that the process provides a much cheaper product which when cemented in position on the stump is indistinguishable from a conventional cast gold crown.
The use of the wax in the marginal portion will ensure that the crown has a very close fit in the important marginal areas of the stump.
The materials which are employed in producing the plaster cast and models may be those normally employed for this purpose by dental technicians. Suitable materials other than plaster may of course be used. Similarly any known material may be employed for the investment casting process which is carried out in a conventional manner.
The plastics material which is used for the first and second impressions should be capable of being formed to the desired shape when heated and should retain that shape when cooled to ambient temperature. A further requirement for the second impression is that the plastics material should be capable of being “burned-out” in the investment casting step. Poly unsaturated hydrocarbon sheets such as polypropylene and, preferably, polyethylene have been found to be suitable but it will be appreciated that other formable materials can be employed provided that they exhibit the desired characteristics outlined above.
The hardenable material which is used for producing the crown form precursor should be capable of being shaped whilst in a plastic state and preferably hardens to form a resilient material which can be distorted at least sufficiently to enable removal of the plastics impression and will subsequently regain substantially its original shape. Hardenable elastomeric materials may be employed for this purpose, particularly cold-curing elastomeric materials. One example of such a material is available commercially under the Trade Mark “IMPREGUM”.
The deformable material which may be used as a backing in the deep-drawing steps may be any material which has the desired resistance to deformation at the deep-drawing temperature so as to control the plastic deformation of the heated plastics sheet to the desired degree. Such a material is available commercially and known in the art as MASTIC.
Reference is now made to the accompanying drawing which is a schematic representation of the steps involved in a preferred method according to the invention for producing a crown form suitable for use in producing an investment casting mould.
Stage I shown in the drawing is an illustration of the deep-drawing of a first sheet of plastics material to the shape of a stock tooth which has been selected to match the teeth surrounding the tooth to be crowned. The plastics sheet is preferably polyethylene.
The deep-drawing technique is carried out by heating a sheet of the plastics material in a frame until it is in a formable state. The stock tooth is then pressed into the sheet over a supporting body of a “Mastic” material which serves to support the plastics sheet during the forming operation. The resulting first plastics impression is shown in step I.
A plaster cast of the stump of the tooth which is to be crowned is produced in a conventional way. The first plastics impression is trimmed from the remainder of the plastics sheet and is filled with hardenable cold-curing elastomer such as “IMPREGUM” and pressed on to the cast model stump as shown in step II. This produces a layer of hardenable material between the model stump and plastics impression and, the excess elastomer is expelled in the region of the margin 14 as can be seen in step III.
When the dentist makes an impression of the patients mouth he makes an impression of the teeth in both the upper and lower jaw as well as a specific impression of the stump of the tooth which is to be crowned. Plaster models of the teeth in the upper and lower jaw and the stump to be crowned are then made from the impressions taken by the dentist.
The assembly of the cast model stump, the layer of hardenable elastomer and first plastics impression is inserted in the plaster model of the appropriate jaw and the model of the other jaw pressed against it so that the occluding tooth can bear upon the first plastics impression and suitably shape the underlying layer of hardenable elastomer.
After the elastomer has hardened the first plastics impression is removed and the excess hardened elastomer removed from the region of the margin in step III and then smoothed down to give a smooth marginal area. This step produces the crown form precursor 16 as shown in step lV. The crown form precursor 16 is then utilised in a second deep-drawing step similar to the one employed for producing the first plastics impression 10. Again it is preferred to use a sheet of polyethylene for this purpose.
The impression is then trimmed from the plastics sheet to produce a second plastics impression 18 which will have the shape of the crown form precursor 16 which in turn has the general shape of the original chosen stock tooth modified to suit the occluding tooth 15. Thus, the second plastics impression will correspond to the desired shape of the crown but when it is assembled on the cast model stump there will be a spacing over at least a portion thereof.
In order that the crown should fit the stump accurately further material in the form of wax is added in the marginal portions as shown in step V. The wax is smoothed down to the desired external configuration and then the second plastics impression 18 together with the wax is removed from the cast model stump to produce the crown form 20 shown in step VI.
This crown may then be provided with a conventional wax sprue and wax reservoir and utilised to produce the investment casting mould. Both the polyethylene and the wax are burned out to leave the mould cavity which is subsequently employed to mould the crown material such as gold to produce the crown.
It will be apparent from the above description, and particularly with reference to step V, that the crown which is produced is considerably thinner than the crown which would be produced by a conventional technique in which crown material would extend from the stump 13 to the outer profile of the second plastics impression 18. It has been found that the production of such thin crowns does not produce an inferior product as when the dentist applies the crown to the stump the space therebetween is filled with cement and the important marginal area is made to fit the stump precisely by virtue of addition of the wax 19 as shown in step V.
In certain circumstances the sheet formed in accordance with step (a) is sufficiently close to the desired shape of form that steps (b) to (f) can be eliminated. Also, where a thick crown is required this form can be used with the hardened material in place to produce an investment casting mould.
The sheet of formable material may be formed by using a convenient forming technique other than the deep-drawing technique described above. Vacuum forming could be used and in this case it would be possible to vacuum form a plurality of forms in a single sheet of formable material.
The method of the invention enables a high quality crown to be produced in a relatively short time and requires less skill than the conventional method involving a carving technique. The method can be employed for producing crowns of any castable material. The thickness of the crown is, of course, predetermined by the thickness of the formed sheet, unless a crown of other than constant thickness is required, in which case material such as wax, can be added in selected areas.
The first sheet of formable material may be preformed and supplied, for example, to a dental laboratory as part of a kit for making crowns. The preformed sheet may include a number of shapes of teeth from which the technician can select a suitable form for his purpose. This avoids the technician having to carry out step (a) of the method and also he does not need to carry a selection of stock teeth for this purpose.
It will be appreciated that the method described above is a particularly attractive commercial method for producing crowns of a precious metal such as gold, as the amount of precious metal used is considerably less than would be used in producing an equivalent crown by a conventional technique.
Dental-crown alloys: High noble (precious), Noble (semiprecious), Base (nonprecious).
When making plans to have a crown placed, your dentist may ask you to make a decision about what type of metal alloy is used when it is fabricated. (This is a decision that needs to be made for all-metal and porcelain-fused to metal dental crowns.)
In general, there are 3 basic types of dental alloys that can be used. They are: high noble, semiprecious, and nonprecious (this classification system based upon the metal’s composition). Each type has its own advantages and disadvantages, including: cost, insurance plan coverage, color (gold or “white”), as well as general physical properties.
Related Page
· Selling scrap
dental crowns.
This page discusses each of the above considerations. However, if cost is not a factor, the alloy having the highest precious metal content typically makes the best choice.
What types of metals are used to make crowns?
Crowns (all-metal and porcelain-fused-to-metal) are made using specific types of dental alloys. No pure metals are used for crowns, not even gold. This is because the physical properties of dental alloys are superior.
The classification of dental alloys.
Here’s the formal classification system that is used to categorize dental alloys.
1) High noble alloys (Precious metals)
This group of alloys has a composition that is over 60% noble metal (gold, palladium and/or platinum), of which more than 40% must be gold.
These metals constitute the “gold standard” of dental alloys; all others are compared to them. High noble alloys are the easiest type of metal to work with (for both the dentist and dental laboratory) and create the most predictable bond with porcelain.
2) Noble alloys (Semiprecious metals)
These alloys have a noble metal content that is, at minimum, over 25%.
3) Non-noble (Nonprecious metals)
These alloys are also referred to as base metals. Their noble metal content is less than 25%. They often contain large percentages of nickel, chromium or beryllium.
Why should I care what metal is used to create my dental crown?
There are several reasons why the type of dental alloy that is used to fabricate your dental crown should be important to you. Some of these reasons will affect you directly. Others will be more of a concern to your dentist, or the dental laboratory that makes it.
A) Color – Dental alloys can be white or yellow.
In those cases where an all-metal dental crown is being placed, you might have a preference as to whether it should have a yellow (like gold) or silver (“white”) coloration. The alloy’s composition determines its color.
B) Costs – High noble metal alloys cost more.
The “noble” dental metals are gold, platinum and palladium. These metals are pricey. And the greater the percentage of them found in the composition of an alloy, the greater its cost will be. With some applications, the overall cost between using a high noble or base metal alloy might be small. But in the case of an all-metal crown for a large molar, it might be a consideration.
C) Dental plan and insurance policy limitations.
If some type of dental plan is paying a part of your bill, you might check to see if there are any limitations as to the type of metal that can be used for crowns. The policy might state that they do not cover the cost of high noble alloys. Or the level of coverage might change based on the type of alloy that is used.
D) Some people have metal allergies.
Studies report that about 10% of the female population and 5% of the male have an allergic response to nickel, chrome and/or beryllium alloys. These metals are often found in the composition of nonprecious dental alloys.
E) The physical properties of the alloy are an important consideration.
Dentists and dental laboratories often have a set opinion about which types of dental alloys they will consider working with. This is because their goal is getting the job done right, the first time. They know that any difficulties or problems experienced will just end up costing them money. So, if choosing a certain type of alloy makes getting a positive result more likely, then that’s the one they are probably going to want to work with.
Advantages of precious dental alloys.
In general, dentists and dental labs prefer to work with high noble alloys. These metals are easiest to cast, provide the most accurate fit on the tooth, offer some degree of malleability (so the fit of the metal can be adjusted, if needed), and offer the most predictable bond with porcelain.
Finishing lines:
Is the final margin that separate between the prepared axial tooth surface and the remaining unprepared tooth surface.
Requirements of finishing line:
1. It must be clear, well defined and smooth, so it can be reproduced on working model.
2. It must be continuous from one surface to another.
3. Whenever possible the finishing line should be placed on sound tooth structure.
Position of finishing line:
1. With the level of free gingival margin.
2. Supra gingival finishing line,: its better to place the finishing line supragingivally for the following reasons:
A. Easily to be prepared without trauma to the soft tissues.
B. Easy to be prepared and finished by dentist.
C. Patient can keep it clean easily.
D. Impression is easily made and can be removed without tearing or deficiency.
3. Subgingival finishing line: indicated in
A. Esthetic.
B. Caries or filling at the area of finishing line.
C. To increase retention of short teeth.
Types of finishing line:
1. Feather edge (knife edge).
2. Chamfer.
3. Shoulder.
4. Bevel shoulder.
The selection of certain type of finishing line depends on:
1. The materials used to construct the restoration.
2. The position of the tooth.
3. The tooth aspect to be prepared.
Feather edge (knife edge):
In this type all convexities coronal to the margin are removed only, its mostly unacceptable but it was advocated already before the development of high speed cutting instruments and improvement of impression materials and techniques, this type of margins lack strength, difficult to locate on the cast and difficult to fabricate the wax pattern, however it provide the best marginal seal and it’s the most conservative type.
Chamfer finishing line:
This type is prepared with a tapered round ended fissure diamond bur, its regarded as the line of choice for most veneer cast metal restorations and lingual margins of porcelain fused to metal restoration. It has been shown to exhibit the least stress.
Shoulder finishing line:
This is the best choice for jacket crowns; the wide ledge provides resistance to occlusal forces and minimizes stresses that might lead to fracture of the restoration, and its less conservative. This finishing line is prepared with flattened end tapered diamond fissure bur. Its very well defined finishing line so it’s easily detected on the cast.
Shoulder with bevel:
In this type we create a bevel on the end margin of unprepared tooth structure, this lies between the prepared and unprepared tooth structure and is very critical area. This type of finishing line is recommended for extremely short walls, since the axial walls of this type is nearly parallel to each other so enhances retention. This type of finishing lines is used for porcelain fused to metal and full cast veneer with acrylic facing.
Types of crowns:
1. Full metal (veneer) crown:
This provides better retention and resistance because all the axial surfaces of the teeth are included in the preparation.
Indication:
1. Posterior abutment teeth with excessive caries.
2. As retainer on tooth receive clasp (posterior teeth).
3. High caries index.
4. Necessity of maximum retention and strength.
Contraindication:
1. Teeth located in the appearance zone.
2. Low caries index.
Advantage:
1. Strong.
2. More conservative and easy to prepared.
3. Provide more retention and resistance compared to partial veneer crowns.
Disadvantage:
1. Poor esthetic.
2. Tarnish and corrosion, so it needs prophylactic measures.
3. Difficulty to test the vitality of the abutment teeth.
Steps of preparation:
Depth orientation grooves must be prepared on the surface of the tooth to act as guide or reference to determine when sufficient amount of tooth structure is removed, without these grooves we may remove much or less tooth structure or we loss time in repeated checking.
1. The preparation for a full veneer crown is begun with the occlusal reduction. By accomplishing this step first, the occlusso gingival length of the preparation can be determined. The potential retention of the preparation can then be assessed, and auxiliary features can be added if necessary there should be
The tooth structure remaining between the orientation grooves is removed to accomplish the occlusal reduction then smooth any roughness left by the grooves. Keeping the occlusal surface in the configuration of the geometric inclines that make up the occlusal surface of any posterior tooth after that a wide bevel is placed on the functional cusp again using the No. 170 buy or rounded tapered diamond. The functional cusp bevel placed on the buccal inclines of mandibular buccal cusps and the lingual inclines of maxillary lingual cusps after completion of occlusal surface preparation we should check the occlusion of the patient in centric and eccentric positions of jaw relationship.
2. Buccal surface: because of the anatomy of the buccal surface of the lower posterior teeth, this surface should be divided into two parts: gingival two thirds and occlusal one third for the gingival two thirds we should place a (DOG) in the center of this surface parallel to the long axis of the tooth and by moving the bur mesially and distally following the inclination of the surface so this surface prepared. For the occlusal one third a (DOG) is placed in the center of this area by placing the bur 45 degree with the long axis of the tooth and by moving the bur with the curvature of the surface to be prepared. This type of preparation is called two plane preparation or two steps
preparation The two plane preparation is done on the buccal surface of the lower molar and the palatal surface of the upper molar.
3. Lingual surface :the (DOG) is placed in the middle parallel to the long axis of the tooth and by moving the bur mesially and distally so we complete the reduction, this type of preparation is done in one plane as it is indicated for the lingual lower and buccal upper molar and premolar teeth.
4. Proximal surfaces: we start with a fine tapered diamond fissure bur (needle type) to open and remove the contact area carefully without touching the adjacent tooth because caries will be developed in the damaged surface later on, because we are going to create a rough surface in addition to removing the outer layer of enamel which is saturated with fluoride. The bur should be rested on the prepared tooth itself and by moving the bar up and down the contact will be removed, finally any sharp angle should be removed to prevent fracture due to stress concentration, sometimes seating groove is placed in the buccal surface of the lower and the palatal surface of the upper molar teeth which act as a guide during placement of the crown, to prevent the rotation of the restoration, increase the surface area of preparation so it enhance the retention and the resistance, finally it improves the seating of crown as it let the escape of the excess cement during cementation.
2-Full metal crown with facing
It is a full metal crown having the labial or buccal surface covered by a tooth colored materials (acrylic, Porcelain), it combines the strength of full metal crown and the cosmetic effect of the tooth colored material, and it is not a conservative type of crown since it includes excessive tooth preparation to provide enough space for the metal and the facing material in addition to that there is excessive contact with the gingival tissue when the margin of the crown is placed close or below the gingival margin ,it can be used on anterior and posterior teeth
Indication:
1. Improvement of esthetics (carious teeth, malposed teeth, peg shaped lateral incisor, discolored teeth).
2. Fracture of tooth without pulp exposure.
3. Teeth with large filling.
4. As a bridge retainer especially in long span bridge.
5. Endodontically treated teeth with sufficient remaining tooth structure.
Contraindications:
1. Teeth with large pulp.
2. Teeth with short crown.
3. Patient with poor oral hygiene.
Advantage:
1. It combines the strength of full metal crown and the cosmetic effect of the tooth colored material.
2. Natural appearance can be closely matched by good technique and if desired through characterization of the restoration with internally or externally applied stains.
Disadvantages:
1. Requires significant tooth reduction to provide sufficient space for the restorative materials.
2. Increases the potential for periodontal disease.
3. Because of the glasslike nature of the veneering material, a metal-ceramic crown is subject to brittle fracture (although such failure can usually be attributed to poor design or fabrication of the restoration).
Preparation
1. Preparation for posterior teeth
We should follow the same principles as in full metal crown as in the full metal crown with one exception only, by doing a deep reduction on the buccal surface to provide enough space for the metal and the facing material and also to gain bulk for proper shade of the final crown The finishing line is shoulder on the buccal surface and chamfer all around the remaining tooth aspects.
2. Preparation for anterior teeth
A. Incisal edge reduction:
We started by basing a depth orientation groove of
B. Preparation of the labial surface:
This surface should be divided into two parts, gingival and incisal, for the gingival part a DOG of
C. Lingual surface preparation:
For the cingulum area a DOG of
Why we do the two steps preparation on the lower buccal, upper palatal surfaces of the posterior and labial surfaces of anterior teeth:
1. To follow the anatomy and the inclination of the tooth and not to disturb the surface geometry.
2. To increase the surface area this will give increase in retention and resistance of the final restoration.
3. To avoid hitting of the pulp chamber during preparation.
4. To give enough space for the restorative material so this will enhance the structural durability other vise we will have bulky restoration, bulky facing or poor shade of the tooth.
Dental Bridge or Pontic or Fixed Bridge or Fixed Partial Denture is a custom-made fake tooth or false teeth or prosthetic device used to replace missing teeth, that is permanently placed between your natural healthy teeth or dental implants. Usually two tooth crowns (tooth caps, “caps”) are holding it in place that are cemented onto your teeth on each side of the false teeth. These two anchoring teeth are called abutment teeth.
Fixed bridges or pontics or prosthetic devices used to replace missing teeth cannot be taken out of your mouth compare with removable partial dentures.
The teeth to be crowned (abutment teeth) are prepared in a very specific way (filing down the tooth to make room for crowns and bridge) by a dentist. Records are given to a dental technician to fabricate the dental bridge, which can then be inserted at another dental appointment.
The main advantages of dental procedures and solve dental problems with the indirect method of teeth restoration:
· you do not need to be in the dental chair
· use of materials that require intense heat to be processed with superior mechanical properties, such as gold and natural looking porcelain
· produce a restoration of much higher quality
Indication to Restore with a Dental Bridge
Re-establish your smile
· Bring back your ability to properly chew
· Help improve speech
· Preserve the shape of your face
· Distribute the forces in your bite properly by replacing missing teeth
· Limit remaining teeth from drifting out of position
· Correct some bite problems
· Reduce the risk of gum disease
Before
After
CLINICAL TECHNIQUE
The clinical techniques for using this class of metal-ceramic materials are the same as conventional metal-ceramic systems, which can be a benefit over many of the all-ceramic systems on the market. Teeth can be prepared with any traditional margin design, but for truly esthetic metal-ceramic restorations, a shoulder preparation that allows for the creation of a 1-mm porcelain margin is preferred. Ideally, a minimum of a 270° or 360° shoulder preparation on teeth in the anterior region facilitates optimal esthetics. Facial reduction can be slightly less than conventional metalceramics as the granular gold surface of Captek gives a light scattering effect that improves the perception of depth in the restoration. Generally, an overall facial thickness of
Diagram of ideal preparation for maximum esthetics for metal-ceramic restorations.
Production of metal skeleton is very hard process, its better to see one time, that ten times read.
Any construction starts with the model. This time with sectional model.
The working surface is covered by the compensation varnish, which serves to compensate for the space under the cement and partial shrinkage of the metal after casting. The varnish is covered to the whole teeth but leave
The gypsum stamps is covered with isolated fluid.
We are doing the cap with submersible wax, the thickness is
For fixing the intermediate part of the prosthesis we put on sticky wax (
There are different companies that produce the standart wax form for the composition.
We put the intermediate part of the prosthesis on the model
Composition elements are connected.
The superfluous wax removed from the stamp. The material easily remove under preparation line.
We put wax on the thin parts of the stamp. We need to do that on the model, especially if we are doing the correction of the shape.
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On the next step we are forming the garland and put some wax on the neck part of the cap.
We correct the form of . Its width varies between ±
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A view of the finished element. The wax composition is collected.
The casting system (3-
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We stick the casting system to the compositoin. We connect the interdental spaces.
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On our days there are different types of waxes, the main condition for all are small contraction, certain hardness and stickiness.
From the correct placement the composition in the casting form depends the density of the metal.
The carcass after the casting cuts from the casting system. We mark and remove places which trouble putting on and out the carcass.
We polish the places where casting system was. We finish the neck part of the crown.
We control the thickness of the carcass. The construction should not be thinner
2 laboratory step
The finished carcass. The surface should not have sharp edges or wedges
Before putting ceramics on it, we wash with oxide aluminum oxide with 150-250 microns, and with pressure 4-6 Bar.
On this slide we see the first layer of putting opaque (powder).
The layer should be the minimum thin and thoroughly rub into the surface of metal.
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The second layer of opaque. Its much more thicker than first. Its better to use glass cane with the round end.
The view of burned model.Its important that opaque have a smooth and straight surface. If there are any defects on the surface we need to polish it, but very carefully with the diamond and cover that parts with opaque again.
The first step in the production process is putting the matherial that allow to get the necessary saturation of color
in the thin parts of the construction. That’s why we put it near the neck of the teeth and in the area of fissures on the occlusual surface, also on the oral surface of the incisors.
Then with the dentine color we form the midle platen. He helps to see the height of the teeth and direction of the teeth. The prosthesis controls in the articulator in the position of central and lateral oclusion.
Now we model the messial and distal platen of buccal surface ot the teeth with the same dentine color.
The construction controls in the articulator
The view of ceramics after burning.
The steps of putting enamel is the same like dentine.
The view after the burniong.
We fit the work on the model.
The tracing paper must easily pass over the teeth and leave the mark, as you can see on the picture.
We polish the surface with backed diamond boron.
We do the first separation with rough disc
We do the finished separation with disc (
It is necessary to provide the smooth surface, that contact with gums.
we polish the chewing surface with balls from baked diamond and carbide boron.
We control the bridge in the articulator.
3 laboratory step
The we do the work with glazing . We need to put the glaze with the thin layer on the teeth.
The view of the work after glazing.
The oven for burning ceramics.