SP / High Precious Full Cast Crown: Pick the Grade, Know the Alloy

What "SP" and "High Precious" Mean on an Rx

"SP" (semi-precious) and "High Precious" are lab names for alloy grades, not official classes. In the US, alloys are classed by how much noble metal they contain, and that class sets the CDT code. The noble metals are gold and the platinum group: platinum, palladium, iridium, rhodium, osmium and ruthenium. Silver doesn't count, even though most people call it a precious metal.

• High noble · D2790. At least 60% noble metal, with at least 40% gold.
• Noble · D2792. At least 25% noble metal. No gold minimum.
• Predominantly base · D2791. Less than 25% noble metal. Our [link: CoCr full cast crown] belongs here.

These thresholds come from the ADA's guide to materials for indirect restorations. Here's the catch for an SP full cast crown: palladium-silver carries a lot of silver, so its class turns on how much palladium it holds. Likewise, a gold color doesn't by itself make a crown high noble.

So code from the composition, not the grade name. Ask for the alloy certificate on any case. It lists the brand, origin, batch number and exact composition, in English, so you can match the percentages against the classes above.

SP Full Cast Crown or High Precious Full Cast Crown: Which Grade?

The two grades differ only in alloy, but that changes how the crown handles at the bench and at the chair.

SP Full Cast Crown (Palladium-Silver)

• Color: silver-white.
• Handling: harder and stiffer than most gold alloys. It holds its shape in thin sections and short spans, but margins don't burnish as easily.
• Keep in mind: silver-palladium alloys can tarnish more readily than high-gold alloys, and they're more sensitive to casting conditions, as dental casting alloy references note.
• Good fit for: molars and premolars where you want a noble alloy without a high gold content.

High Precious Full Cast Crown (Gold-Based)

• Color: yellow gold.
• Handling: softer and more ductile than palladium-silver. It casts well, and margins can be burnished.
• Track record: the ADA puts the average service life of metal restorations at 18–20 years, some past 40. A retrospective study of 1,314 cast gold restorations in service from 1 to 52 years reported 95.4% survival. It mixed inlays, onlays and crowns from a single practice, so read it as history, not a promise for any one crown.
• Good fit for: second molars, patients who ask for gold, and cases where margin adaptation matters most.

Bridges in Either Grade

We cast full-metal bridges in both grades, always in one alloy from abutment to abutment. Mixing alloys in one framework creates weak joints and invites corrosion.

For bridges, the alloy's strength type matters as much as its noble content. ISO 22674 sorts dental alloys into Types 0 to 5 by mechanical performance. Type 3 is the class meant for multi-unit fixed prostheses. Five units is the usual long-span threshold. Past that, abutment count, bone support and bite habits decide how much load the connectors can take, so note them on the Rx.

When a Noble or High Noble Full Cast Crown Fits the Case

An SP / High Precious full cast crown suits posterior teeth that need full coverage where appearance isn't a priority. The case for a noble alloy over cobalt-chrome is mostly handling. Base metals are very hard, which makes chairside adjustment and polishing harder. Noble alloys are generally easier to finish.

Good cases

• Molars and premolars with large defects, cracks or heavy existing restorations
• Limited interocclusal space or short clinical crowns, where metal's thin sections help
• Teeth that need full coverage and strong retention

Choose something else when

• The tooth shows when the patient smiles. Try [link: Zirconia crown].
• You want metal strength under a tooth-colored surface. That's our [link: PFM crown].
• Part of the tooth is intact and partial coverage would do the job.
• The patient has a documented sensitivity to an alloy element (see the FAQ).

Prep, Space and Cementation

Both grades take the same prep, so you can settle on the grade after the scan. These figures are general guidance for cast metal crowns, based on the complete cast crown preparation in fixed prosthodontics texts. Your own protocol comes first.

• Occlusal clearance: at least 1.5 mm on functional cusps and about 1 mm on non-functional cusps.
• Margin: a smooth chamfer, ideally supragingival, giving about 0.5 mm of metal at the edge. A feather-edge finish line also works with gold alloys.
• Axial walls: follow the long axis of the tooth, with about 6° of taper.

If the Space Is Tight

Write "occlusal space inadequate" on the Rx with the clearance you have. Our technicians measure the space on the model before production and tell you where it falls short. From there, you can reduce the prep further, adjust the opposing tooth or switch to another material. If you'd like, we'll tuck a note in the box showing which tooth needs how many millimeters of extra reduction.

Cementation

Full cast precious crowns are usually seated with conventional cement: zinc phosphate, glass ionomer, resin-modified glass ionomer or zinc polycarboxylate. A resin cement can help on short or over-tapered preps. Check the cement maker's instructions for noble alloys first, though. Some resin systems call for a metal primer or tin plating on precious-metal surfaces.

How We Make and Check Each Crown

Every SP / High Precious full cast crown is made in-house at our four labs in Shenzhen and Huizhou, China. We've been doing this since 2012, with about 460 people on staff, and we don't outsource any step.

1. Case check. We review the Rx, scan or impression, bite record and alloy grade. If anything is unclear, we ask before we start.
2. Design. Contacts, occlusion and anatomy are set to your Rx. The design becomes a burnout pattern that's sprued and invested.
3. Casting. We melt and cast under vacuum or a protective atmosphere. The melting equipment goes through installation, operational and performance qualification, and its temperature control is rechecked on a schedule.
4. Fit. The casting is devested, seated on the die and adjusted on the mounted models.
5. Polish. Coarse and fine finishing, then polishing compounds, then ultrasonic and steam cleaning.
6. Final inspection. Checked against the list below, then disinfected, packed and shipped.

Precious Alloys Stay Separate

Gold, palladium-silver and base metals each get their own work area, tools, sandblasting units and polishing stations, and scrap is sorted by alloy. That keeps every alloy's composition stable, so the composition on the certificate matches the metal in your crown.

What We Check Before It Ships

• Margins: an even fit under magnification, with no lifting, gaps or flash
• Intaglio surface: no burrs, nodules or porosity
• Contacts: proper tightness once the crown is seated on the model
• Occlusion: centric, protrusive and lateral contacts checked, with early contacts removed

95% of our restorations pass final inspection. Our remake rate is 2–3%. That's cases clients send back, across everything we make, and it's tracked separately from the inspection pass rate. More detail is on our [link: Quality] page.

Alloy Documents and Compliance

• Manufacturer data. The alloy maker's biocompatibility (ISO 10993) and technical documents, on request.
• No silent swaps. We never change the alloy without your consent, written or verbal.
• Registrations. Istar is an FDA-registered establishment, Registration No. 3039441248. Anyone can look it up in the FDA establishment registration database, no login needed. We're also registered with the UK MHRA.
• Quality system and EU. Our labs run an ISO 13485 quality management system. For EU clients, custom-made restorations follow the MDR custom-made device procedure, with a statement for each device.

Ordering an SP / High Precious Full Cast Crown

1. Send the case. Scans from 3Shape TRIOS, Medit, iTero, CEREC, Shining3D Aoralscan or Planmeca all work. STL is enough for posterior crowns, or order through 3Shape Communicate or Medit Link. Physical cases work too: VPS or polyether impressions, cleaned and disinfected before shipping, with a VPS bite record. Skip bite wax, because it softens and distorts in transit.
2. Fill in the Rx. SP or High Precious, finish line, contact tightness, occlusal notes and available space. Add a scan of the old crown or the opposing tooth if you want its shape copied or mirrored.
3. Approve the design (optional). We'll send screenshots or an STL by email or your chat group. Approval adds 1–2 days to the lab time.
4. We make it and ship it. It goes to any address you name.
5. Seat it and tell us. If a contact is tight or the bite is high, send a photo or a new scan and we'll trace the cause with you. That could be the bite record, an over-erupted opposing tooth or the die.
6. Rush at no charge. For clients who send 10 or more cases a month, any case can go rush. We guarantee the ship date. Arrival depends on international transit and customs.
7. Shipping. You pay to send impressions or models to us. We pay to ship finished work back, remakes included.

For Dental Labs

Already designing in-house? Send editable exocad or 3Shape files and we'll cast, fit and polish your high noble full cast crown or noble-alloy work to your design. We can also take on single steps, such as finishing and polishing. Finished cases can ship straight to your client's office. The sender address on the waybill will still show Istar.

FAQ

My patient has reacted to metal before. Which grade should I use?

That's a clinical call between you and the patient. Start with the composition. Reactions to palladium and gold have been reported, though how common they are isn't clear, and adverse reactions to dental materials overall are rare. The ADA cites rates as low as 0.14% of the general population. Ask us for the certificates for both grades and compare them with the patient's patch-test results. If no alloy suits, a metal-free zirconia crown avoids alloy exposure altogether.

What should a scan case include?

The prep arch, the opposing arch and a bite scan, with the adjacent teeth captured. We'll ask for a rescan if the finish line is blurred or hidden by tissue, if the mesh has large holes, if the stitching shows steps or misalignment, or if the bite registration is off. Zip each case in its own folder (not RAR), keep a single-arch STL under 150 MB, and start every file name with the same case ID.

Can you use a specific alloy brand?

Yes. Name the brand on the Rx and we'll cast in it. If that alloy is ever out of stock, we'll contact you to agree on an alternative or a new date before going ahead.

Do D2790–D2792 cover bridge units too?

No. D2790, D2791 and D2792 are single-crown codes. A high noble full cast crown that serves as a bridge retainer, and the pontic beside it, are coded separately in the fixed prosthodontics section of CDT. Those codes follow the same high noble, noble and predominantly base classes, so the certificate works for them too.

Send Your First Case

Put your next posterior crown on an Rx as an SP full cast crown or a high precious full cast crown, and send it as a test case. A case coordinator will be your contact from the first order on.

[Send a Test Case] · [Request the Product Catalog]