Conical tooth preparations, sharp edges, undercut areas and divergent friction grooves should be avoided when preparing. Ensure an anatomical preparation in the palatal and lingual regions, as the crowns will be full-coverage porcelain. Then smooth the preparation surfaces with appropriately shaped diamond finishers. The crowns should be cemented with a fine-grained, 5 – 10 µm grit size zinc-phosphate cement because of the highly precise fit. HELIOFORM^® crowns are not fully stable until they have been cemented. HELIOFORM^® crowns should not be fitted as temporaries.

HELIOFORM^®-Inlays

Always use box preparations without a bevel for HELIOFORM^® inlays. The angle of the cavity should be 6 degrees.

Approximal cavities should also be prepared with a box and without a slice, ensuring the inner edges are rounded. The size of the cavity should take into account the space required for the porcelain. The cavity should have a minimum depth and width of 2 mm. Finally the preparation surfaces should be smoothed with the appropriate diamond finishers.

Avoid occlusal contact at the margins. The ductile fine-gold margin of HELIOFORM^® inlays can be adapted with a suitable instrument when the cement is setting.

HELIOFORM^®-Onlays

Onlay preparation combines crown and inlay preparations and follows the same guidelines. Onlay preparation begins with an occlusal box preparation and a cavity angle of about 6 degrees. The size of the cavity should take into account the space required for the porcelain. The cavity should have a minimum depth and width of 2 mm. Approximal cavities should also be prepared with a box and without a slice, ensuring the inner edges are rounded. The load-bearing cusps are covered by removing 1.2 mm of tooth structure. A deep chamfer is placed along the length of the clinical half of the crown as a marginal seal. 1.2 mm of tooth structure is also removed from the non-supporting cusps. Cusp coverage is completed with a deep chamfer in the upper quarter of the crown. Sharp edges, undercuts, slices and knife-edge preparations should be avoided. The shade for HELIOFORM^® inlays and onlays should be taken at a separate appointment for trying in the framework, as the opacity of the fine-gold framework alters the shade of the rest of the tooth.

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