Friday, January 18th 2019 9:34PM EST

Guide for Digitally Fabricated Crowns

Posted on by Bicon

The fabrication of a digital crown for a Bicon implant begins by achieving a digital image of a virtual or tangible prosthetic model with a Bicon Implant Analog or Universal Abutment Transfer Die. The model can be achieved digitally by the preferred method of intraorally scanning a 2.0mm, 2.5 mm, or 3.0mm white Scan Post seated in the well of an implant. The following link provides a video with an explanation of the clinical techniques for intraoral scanning using a Scan Post, as well as making implant-level and abutment-level conventional transfer impressions: VIDEO » Immediate Placement and Restoration of a Maxillary First Molar with an Extra-Orally Cemented Lithium Disilicate Crown

[1-9] Once the digital scan file has been secured and entered into either the 3Shape or exocad design software, the appropriate Universal Abutment file can be selected from the CAD software’s digital abutment library to commence the designing of the crown.

[10-13] When designing, be cognizant of the minimum dimensions indicated by the intended material’s manufacturer, as well as their recommended post-milling treatment of their material. The designed STL file can then be sent to a milling machine for fabrication.

[14-17] Commonly used materials for digital crowns are Hybrid Ceramics, such as Enamic by Vita, Shofu Block HC Hard by Shofu, IPS e.max (a lithium disilicate ceramic), and Zirconia. Although a crown may be fabricated without a physical model, it may be more practical for those unfamiliar with digital dentistry to have a physical model to facilitate their confirming or adjusting the crown’s interproximal and occlusal contacts.

[18-19] Our preference is to use the Shofu Block HC Hard, since it can be readily modified chairside, either by reduction or addition, on the day of its insertion or any day, even years into the future. Additionally, it can withstand forces of shear, whereas the other materials do not provide for these clinical capabilities. The Shofu Block HC Hard is currently available in three shades (A2LT, A3.5LT, A4LT) and the following three sizes: Small (10.0mm x 12.0mm x 16.0mm), Medium (12.0mm x 14.0mm x 18.0mm), and Large (14.5mm x 14.5mm x 18.0mm).

[20-28] Additionally, our preference is to bond and to extraorally cement a CAD/CAM crown to a modified or unmodified Universal Abutment with resin cement for insertion as a single unit.

[29-39] After removing the extraneous resin cement from the Universal Abutment and removing the Temporary Abutment from the well of the implant, the Universal Abutment with the extraorally cemented CAD/CAM crown is placed into the well of the implant. Once the restoration is initially positioned, the patient may seat it by applying occlusal pressure with a cotton swab. Alternatively, the crown could be seated with a gentle tap. After confirming the appropriateness of the interproximal and occlusal contacts, a radiograph should be taken to complete the treatment.

[40-45] Rather than intraoral scanning, an implant-level conventional transfer impression may be made with a titanium Impression Post and a plastic Impression Sleeve.

[46-51] A third way to intraorally record an impression is to make an abutment-level conventional transfer impression, which utilizes a Universal Abutment and plastic Abutment-level Impression Sleeve. A fourth way is to scan the actual abutment intraorally.

Subsequently, physical impressions can be poured into stone with a titanium Implant Analog or a Universal Abutment Transfer Die, or digitally scanned for the printing of an actual physical model. The poured or printed model with an Implant Analog or a Universal Abutment Transfer Die may be digitally scanned to achieve a digital image of the abutment and prosthetic model. The digital scanning of an actual abutment, preferably a modified or unmodified Universal Abutment, is less desirable but still a feasible option. The abutment should have the widest diameter to fill the mesiodistal edentulous space without encroaching upon the adjacent interdental papillae.

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