CAD/CAM in Restorative Dentistry is introduced in this series by Dr. Alessandro Devigus, Switzerland. In part 4 he demonstrates the Computer added manufacturing (CAM) with a CEREC milling unit and the adhesive cementation as an important step by taking the example of a ceramic inlay for a first left molar in the lower jaw. The final Computer added design (CAD) presents a virtual 3D ceramic block proving the inner position of the restoration on the computer.
A ceramic block is chosen with the CEREC software version 3.6 and is positioned and fixed in a stand of a CEREC-unit initiating the milling procedure. The milling machine first calibrates before the milling process of 9 min is started and the work piece is produced with a pin that has to be removed very carefully with a fine rotating diamond and smoothened with a Soflex disc. A rubber dam is applied in the patient’s mouth for absolute dryness and a good overview. In an initial fitting marginal adaptation and proximal contact is proven matching the work piece with minimal adjustments to the adjacent teeth. Two additional matrix bands in combination with wooden wedges are inserted in the approximal area.
The inner surface of the CAD/CAM-inlay is conditioned for 60 s with 6 % hydrofluoric acid to promote a morphological change to a rough surface enabling penetrating silanization due to a successful wetting with the luting agent. The cavity is cleaned with 2 % chlorhexidine using a cotton pellet. An enamel etch is performed with phosphoric acid for 30 s according to a multistep adhesive system. Primer is applied in a light scrubbing motion and has to stay in the cavity for 15 s removing the smear layer and creating a transition between the hydrophilic substrate and the planned restoration via tag formation. The cavity is dried out thoroughly with an air syringe before the applied adhesive agent creates a hydrophobic layer bridging the gap between the hydrophilic dentin and the hydrophobic light curing composite material in a contact time of at least 10 s.
After slightly drying of the adhesive hydrophobic bonding is applied in the cavity and on the inner surface of the CEREC-inlay and blown to a thin layer. The cementation of the CAD/CAM-inlay is carried out with light curing composite ensuring high quality margins due to the high filler content. The composite is applied in the inner surface of the preparation and the placement of the inlay is performed manually by gently and evenly occlusal pressing. The excess material is removed easily before the final insertion is finished with more pressure. All surfaces are light cured using a high power LED device. The occlusal finishing after the bite control is performed with fine cone shaped or round diamonds reconturing the anatomy without pressure remodelling the original occlusal situation. Final smoothing and high-gloss polishing is accomplished with fine Soflex discs and a nylon brush with polishing agent.
See more basic information with Dr. Devigus in module 1 to 3 of this series presenting step by step the procedure for an all-ceramic restoration with CAD/CAM.