Custum tray and abutment tray

What's custum tray ?
It is a tray for obtaining an accurate impression. It is a tray that has a fixed space for the dentition and the alveolar ridge. Manufactured by a dental technician using an immediate polymerization resin.
When using a silicone impression material, the inner surface is mechanically roughened.
When using an alginate impression material, an infinite number of holes are made in the tray.
What's abutment tray ?
The monodental tray is a tray for impressing the abutment teeth in units of one tooth for the purpose of preventing deformation of the impression. The advantage is to improve the dimensional accuracy by making the thickness of the impression material a uniform thin layer. Gingival retraction can be performed simultaneously with the impression. Cut off the effect of undercutting of adjacent teeth. Etc. It is manufactured on a model with an immediate polymerization resin, and it is used after correcting the margin in the oral cavity. Materials
Paraffin wax, immediate polymerization resin, tray resin (immediate polymerization resin), gauze, technical bar (multi-pad).
Methods1. Abutment tooth formation is ideally performed on the model.
2. Make a spacer with paraffin wax.
3. Apply a separation material (Vaseline) and press-fit the immediate polymerization resin.
4. Once the resin is cured, make the shape correction with a bar.
5. The handle is made of resin and the inside is further roughened.

cast clasp made by cobalt-chromium alloy

What is a cast clasp made by cobalt-chromium alloy ? 
 It is the clasp which I cast dental cobalt-chromium alloy and produced. A clasp is a fixture to prevent dentures from working. I am if I go to the thing that is better than the clasp which the conformity for the tooth plane bends a wire and produced, the clasp tip and am thin at the thickness of the clasp arm, and, as for the cast clasp, what I can thin is an advantage.
 The dental cobalt-chromium alloy has a bigger tensile strength (strength) and hardness than a dentistry government funds alloy, and the feature is that growth is small. Because properties of matter decrease remarkably when atmospheric carbon gets mixed in the case of casting, what a thing, the segregation that I cannot use for casting repeatedly produce is matters that require attention. I can improve segregation if I perform equalization annealing, but the compatibility of the casting body might turn worse. Cobalt and the chromic ion are the elements which are easy to become the allergy to metal, but corrosion resistance is high, and the cobalt-chromium alloy is said to be it to be formed in the passivity metal surface if there is little ion elution. In Europe, cobalt-chromium alloy has begun to be used for porcelain firing use as a substitute alloy of the Ni-Cr alloy for porcelain firing from the 2000s. The Ni-Cr alloy adversely affecting the health of a dental technician processing this alloy, the price of money soars worldwide, and these backgrounds include that it becomes difficult to use a gold alloy.

 In late years the development of the 3D printer technology (addition production technique) is remarkable, and movement to apply to a dental prosthesis restoration thing in the dentistry industry is seen. 3D printer (the selective laser melting method) metal as for the cobalt-chromium alloy SLM method, direct metal laser sintering, Molding is enabled in DMLS method), and, in fundamental researches and a clinical study, a biocompatible evaluation (cell line) of the cobalt chrome molybdenum alloy powder for the compatibility evaluation for the abutment tooth model of the metal coping made by cobalt-chromium alloy for porcelain firing, 3D printers is performed. When a lot of conclusions such as the lost-wax process <CAD/CAM milling method < 3D printer method (the selective laser melting method) need the improvement of the compatibility, the compatibility is mentioned. 

Materials
 Surveyer, wax, a stock tray for single chin or individual tray, silicone rubber impression material, burying materials for fireproof model manufacture, plastic ring, vacuum kneading on fire harmony machine, phosphate system burying materials, dental cobalt-chromium alloy, high frequency casting machine, abrasion tool production method (Method of fabrication)
１．I take the double impressions of the tooth to cover with a clasp and produce a fireproof model.
２． Based on the information that I surveying and obtained, I design the clasp.
３． I upload wax on a fireproof model.
４．I perform it until sprue 植立, burying.
５．I heat to 800 degrees and cast it with a high frequency casting machine.
６．I calculate casting health and remove an oxidation film in alumina sandblast.
７． I fit and adjust it and study hard.

Discussion
１．Together with a model about the burying method (the fireproof model method)
 Because the cobalt-chromium alloy has high melting point, the shrinkage at the time of the casting is big. Therefore wax improves on the fireproof model which increased dimensions and manufactures a mold and I revise it and manufacture it. When direct wax improves on a working cast, a smallish casting body may be made without enough the expansion of the mold.
２． About the production of the clasp using a 3D printer technology
 Metal 3D printer (the selective laser melting method) The SLM method, the direct laser melting method, I sinter the powder of Co-Cr alloy and the Ti alloy which are DMLS method) or melt and come to be able to mold a clasp. In the study, the fatigue test of a molded clasp is carried out now. It is not evaluated the conformity precision.
 I mold a clasp pattern with 3D printer (liquid tank photopolymerization method, ink-jet method) of the resin and may produce a good casting clasp of the conformity precision by using every model together with the burying method and a lost-wax process. However, evaluations such as production precision or the surface coarseness are not accomplished.
 "270 EOSINT M dental" of EOS company began to sell it in Japan in 2015. This can mold a metal floor, a clasp, a crown, metal coping with exclusive cobalt-chromium alloy powder. The compatibility evaluation for the abutment tooth model of the metal coping made by cobalt-chromium alloy is accomplished by already in vivo in vitro and many researchers.

Conclusion
 I was able to produce a product made in good cobalt-chromium alloy cast clasp of the conformity precision by using the burying method together with a model this time.

Metal core

What is a metal core? (What's Metal core?)

It refers to the construction of a metal abutment.
If an appropriate abutment tooth form can not be obtained only by the formation of the dental crown tooth due to the tooth loss of the dental crown or endodontic treatment, etc., build up the shortage with artificial material. It is said to build a kite.
Above all, cast abutment construction is a method of recovering the abutment tooth form by asking for retention in the pulp cavity and the root canal, taking an impression of the abutment tooth, and making it using a working model. Metals for casting support construction include gold alloys, gold-silver-palladium alloys, and silver alloys.

The features of the cast-in-place construction method include the following.

1. Full cast crowns can be worn after construction of cast abutments, even for teeth with pronounced crown collapse.
2. Can protect vulnerable residual tooth quality.
3. The improvement of the shape of the abutment tooth increases the holding power of the crown.
4. The simplification of the abutment tooth configuration can improve the crown compatibility.
5. The crown axis can be improved, and it can also be applied to the adjustment of the attachment / detachment direction of the bridge abutment.
6. The procedure at the time of crown re-production can be simplified.
7. Equalization of crown thickness can be achieved.

Materials
 Model trimmer, super hard plaster, ordinary plaster, die lock tray, unity articulator, plaster split saw, vaseline, round bar, wax separating material, inlay wax soft (rod), lab silicone putty, sprue wax, truncated cone, thickness 0.7mm casting liner, stainless ring, vacuum kneader, furnace, gypsum investment material, centrifugal caster, match, gas blow pipe, low melting point flux, dental silver alloy (for metal core), cutting disc, carbide Bar, paper cone, brown silicone point.

Method of fabrication
1. The model base is removed with a model trimmer so that the base of the dentition model is parallel to the occlusal plane and the thickness is 7 to 10 cm.
2. Form maintenance holes in the base surface.
3. Add super hard gypsum to a large lock tray with appropriate mixing ratio, pour, and set a dentition model on it.
4. Once the super hard gypsum hardens, attach the working model to the articulator.
5. Divide each abutment tooth with a plaster split saw.
6. Perform margin trimming.
7. Apply wax separation material to the abutment teeth.
8. The post portion is formed by a soft pressure welding method.
The tip of pressing the wax to the back of the root canal is to first make a wax block larger than the external shape of the abutment teeth. Next, a portion about 2-3 mm hard from the outside is made, and the central portion of the wax block is heated with a heated wax instrument. Then, the softened wax is pressed in at the timing when the surface of the heating part turns dark and cloudy.
9. Once the post is complete, make the crown profile wax-up.
10. A core of the contour is made of silicone putty to record the crown contour.
11. Referring to the putty, the crown wax is removed so that the thickness of the crown is uniform and the axial taper is 2 to 8 °. And it forms in the simplest possible abutment tooth form.
12. Once waxing up is complete, plant thick and short sprue wax on the occlusal surface of the wax core.
13. Put a wax pattern on the frustum and wrap a casting liner inside the stainless steel ring.
14. Buried with gypsum-based investment material (standard mixing ratio)
15. Make mold according to manufacturer's specification (lost wax method)
16. Cast the specified metal.
17. Once the mold has cooled, index the cast.
18. After sprue cut, after mobile correction with a straight bar, it is finished by grinding to the roughness of the brown silicon point.

Discussion
1. About working model
 In case of manufacturing only the abutment construction, the accuracy of the positional relationship of the dentition model is not required so much. Therefore, this time, a divided tooth row model using a die lock tray was manufactured. Super-hard gypsum was used in the tray because it is desirable to produce a working model that is as accurate as possible in positional relationship. In addition, if dust such as gypsum scraps and wax adheres to the inner surface of the tray, the accuracy of the positional relationship significantly deteriorates.

The split dentition model using the die lock tray can have a slightly shorter working time than producing a split dentition model using the dowel pins. In addition, it is an advantage that there is no concern of penetrating the post when drilling holes for dowel pin planting.

2. About wax up
There are several conceivable ways to wax up the post section. One is the softening pressure welding method used this time. This method requires sense and skill, and it is presumed that few dental technicians can use this method at present. Another method is to pour the wax into the post and heat the wax into a liquid state, and immediately insert a resin or metal rod so that the wax in the post can be removed. This method is simpler as a method, but has the disadvantages that it is difficult to pour the wax to the back of the post, that bubbles are mixed in, and the wax in the post part is difficult to remove. As another method, there is a method of pouring a pattern resin into a post portion, etc., but when an undercut exists in the post portion, removal of the pattern is difficult, so it can not be used so much.

Abutment tooth part is considered to be able to produce the abutment construction which considered the clearance of the front crown, if the silicon core is produced after waxing up the crown external shape once and the clearance is confirmed and manufactured. . Without the silicon core, it is surmised that technical errors such as non-uniform thickness of the crown formed on the abutment construction and misalignment of the tooth axis are likely to occur. Of these errors, the tooth axis misalignment is likely to occur as well when the working model is not a parallel model.

3. About casting
This time, dental low melting point silver alloy was used. This differs from the gold-silver-palladium alloy in the casting process because the melting point is about 600 ° C. When casting a gold-silver-palladium alloy, the mold heated to 700 ° C is cast when it is in the red state, whereas when casting a low melting point silver alloy for dental use, the mold heated to 700 ° C is cast as a match It is necessary to cool the metal to a temperature that does not ignite and then melt and cast the metal. Also, it is necessary to use a special low melting point type flux. Even when heating and melting the low melting point silver alloy, it is necessary to stop the heating for about 3 to 4 seconds after the alloy is rounded after adding the flux and then centrifugally cast it.
About the production of metal core using 4.3D printer

If a resin-made base construction model with excellent heat dissipation is formed using liquid tank photopolymerization method and inkjet 3D printer technology, existing dental alloy products can be made by using the lost wax casting method in combination Abutment construction of the can be produced. It is necessary to verify the adaptation accuracy to the model in the future.

Conclusion
  A high-precision, high-quality metal core could be manufactured by making full use of the ideal abutment construction by the silicon core method, the formation of the post by the soft welding method, and the special casting technology of the low melting point alloy.