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Inside Dental Technology

April 2014, Volume 5, Issue 4
Published by AEGIS Communications


Yesterday’s Materials Create Tomorrow’s Products

The versatility of Renfert’s polishing and finishing tools

By Guido Testa, CDT

For years, the author of this article and his colleagues have used products and equipment from Renfert ( www.renfertusa.com) to polish and finish single units and bridges fabricated with all-ceramic and metal materials. When the purchase of a Sirona CAD/CAM unit (Sirona, www.sirona.com) extended the author’s laboratory’s range of materials to include lithium disilicate, zirconia, and laser-sintered chrome cobalt, it gave rise to some questions: Which processes and materials could the laboratory use to provide the perfect finish for these new high-quality restorations? Would the previously tried and tested materials still meet this challenge? The following details the author’s experience.

Lithium Disilicate

There are three Renfert products used by the author’s laboratory to finish lithium disilicate: Dynex Brillant diamond discs for separating the milled restoration from the block (Figure 1), Occlutec articulating spray to check high spots, and Polisoft A polishers to polish the restoration.

The author’s laboratory uses the following procedure:

1. The tooth is separated from the lithium disilicate block using a Dynex Brillant disc and a moist sponge.

2. With the aid of contact spray, the tooth is adapted to the die using a water-cooled turbine and a fine-cut diamond cutter.

3. After polishing the larger surfaces, the occlusion is checked using the pear-shaped diamond cutter for ceramic Italcos PD 10 E.

4. Polisoft A polishers are extremely versatile. Trimming a Polisoft A polisher to a lens shape enables precise polishing of surfaces and material-friendly creation of the macrotexture of cusps or other distinctively polished surfaces.

This technique provides the lithium disilicate with a homogeneous surface, positively affecting the restoration’s esthetics post-sintering. A perfect end result is achieved with the application of stains and shades.

IPS e.max® and Zirconia

Shifting focus to the porcelain currently used in his laboratory, the author veneers zirconia frameworks using IPS e.max® porcelain (Ivoclar Vivadent, www.ivoclarvivadent.com). This material is very popular with clients due to its esthetic quality, as it gives restorations a natural, vital, and translucent appearance similar to that of natural teeth. IPS e.max has been an important factor in the success of the author’s laboratory over the past three years.

The author and his colleagues like the precise, fine cut of Renfert’s Turbo-Flex S diamond disc (Figure 2 and Figure 3) when applied to zirconia units, which are separated from the blocks before sintering. Multi-unit bridges milled from 85/40 zirconia blocks are only separated from the block after sintering using the Dynex Brillant diamond disc. These discs are used in conjunction with the moist sponge “wet” technique (Figure 4), and their flexibility and strength make them ideal for preparing interdental spaces. The wet technique is necessary in this instance as it helps to avoid overheating the material. When using the wet technique, the technician must guide the cut-off discs simultaneously over the connection that requires separating and a wet sponge.

Zirconia in Visible Positions

When preparing zirconia for visible areas (occlusal or palatal surfaces, strengthening margins, connector areas) the author polishes the material in the following steps:

1. Finely prepare the occlusal grooves and strengthen margins and connectors using a water-cooled turbine and flame-shaped diamond cutter.

2. Smooth the extensive surfaces, such as the palatal surfaces, using a pear-shaped, aluminum-oxide rotary instrument.

3. Polish all visible areas using the Polisoft polisher. The polisher is first trimmed to a lens shape, then Kohinoor L diamond paste is applied for polishing all surfaces at a low motor speed (Figure 5).

The end result is smooth, high-luster surfaces.

CrCo

When working with laser-sintered and milled CrCo, smooth surfaces may be obtained when polishing the margins with Polisoft A. This is both a time- and cost-saving measure. The author suggests that laboratory technicians pre-polish their CrCo restorations with Bison brushes and Saphir polishing paste, followed by a high-luster polishing with Saphir paste and a mounted cotton buff.

Contact Detection

While the author has tried many articulating sprays, a direct comparison with Occlutec-Spray shows that the latter offers the following advantages:

1. After adjusting the restoration,
the spray can be easily removed without leaving colored marks on the dental stone model.

2. It is very easy to use and the powder film is so thin that the dimensions of the die are not distorted.

3. The Occlutec container’s high gas pressure enables an optimal spray technique, making it unnecessary to spray the die several times. Repeated sprayings may result in the die having an onion layer effect, which can detrimentally affect precision and result in impairment of the final fit.

4. Occlutec is also ideal for adjusting the proximal contacts, preparing pontics with tissue-supported porcelain contact surfaces, and for adapting the tissue section of implant-borne crowns to obtain an optimal emergence profile.

Conclusion

In conclusion, the author will continue to use Renfert products for future cases. In his experience, the products are both reliable and highly developed technically with regard to application with new materials. The author’s laboratory has used Polisoft A for Empress, metal, and now for lithium disilicate, zirconia, and milled and laser-sintered CrCo. Kohinoor polishing paste, which was ideal for polishing porcelain, is now optimal for use with zirconia. There are also newer products such as Dynex Brillant, which performs optimally with the new ceramics, and the silicone disc Art. No. 860000, which can be used to polish zirconia, disilicate, and IPS e.max porcelain.

The author’s experience with Renfert’s product line demonstrates how a modern company can cater to the latest market demands and customer requirements without completely upending their product line. By revising existing products and adding new ones as needed, Renfert enables optimal processing of new materials, thus helping customers fabricate excellent final restorations.

This article was first published in a 2013 issue of the Renfert Report.

Guido Testa, CDT is a dental technician, laboratory owner, lecturer, and course instructor from Italy.

Disclaimer: The preceding material was provided by the manufacturer. The statements and opinions contained therein are solely those of the manufacturer and not of the editors, publisher, or the Editorial Board of Inside Dental Technology.

For more information, contact:

Renfert GmbH
P 630-762-1803
W www.renfert.com


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Image Gallery

The esthetic result on the model.

Figure 1

Using a Turbo-Flex S diamond disc to separate zirconia units from their blocks before sintering.

Figure 2

Using a Turbo-Flex S diamond disc to separate zirconia units from their blocks before sintering.

Figure 3

Using a Dynex Brillant disc in conjunction with a moist sponge for the “wet” technique.

Figure 4

Using a lens-shaped polisher and Kohinoor paste to polish a surface.

Figure 5