The powdering is a very important step with the Cerec procedure. Only the powdered tooth-surface is readable by the 3D camera. The powder serves as an anti reflection surface. Different opacities of enamel dentin and root cementum would cause reflections, which are not correctly interpreted by the camera. The tooth surface should possibly have an even and thin powder coating. Therefore a very soft pressure in the powder container is necessary. The powder application should be applied on the tooth-surface in a 45° angle. This is very critical with the prevailing systems in the posterior of the upper jaw. Hard to reach are the vertical walls of the distal boxes and on the bottom of the distal boxes easily develops a slightly thick powder layer - a “puddle”. A marginal space is possible, since the system can only identify the powdered surface with the photographic impression. The titanium oxide is hydrophilic, which absorbs water and tends to form clumps. The powder offered by VITA and Ivoclar already contains clumps from the production side. During powdering it should be possible to vary the air pressure. Even the best and most dry Titanoxidpowder tends to build up structures in the powder container under air pressure, like powder snow in a winter storm. The powder even builds vertical pillars on the glass surface. Therefore the air pressure must be increased in order to generate an even powder flow. Occasional tapping on the powder container is unavoidable to subside the internal ‘snow drifts’ in the powder container.

The dentist notices more deficiencies with the prevailing powder systems. The investment in Cerec and the progressive system of the Cerec-restoration is in contrast to the offered powder aids. Demonstrations with the spray can in vitro do not demonstrate the difficulties with the patient.

• Flammable gas, irritating for the patient and the user
• Clumping of the powder especially with the necessary tilting in the distal area through escape of liquid gas, air moisture-precipitation through cooling down of the powder bottle and the canula and through contact of the canula with saliva.
• Insufficient sterilization of the tubes
• Fragile plastic tubes and insufficient hold in the spray can and powder container
• Powder application is uneven since the powder tends to build up on the sides of the powder container. The powder application stops.
• Constant knocking of the powder container.
• Constant powder probes on the gloves of the user.
• High costs and effort for supplies of the gas cans.
• Annoying delays and insecurity on the patient.

Alternative spray cans are extremely expensive and quickly used. The powder layer is unfortunately the same colour as the teeth and therefore difficult to control. The removal is utmost difficult.

Other makeshifts, which are set on the spray hand-piece, are situated so that the powder gets clogged in the exit of the bottle. The spray hand-piece is blocked and not usable for its purpose.

Other aids are offered for the connection to the turbine hose, which uses air pressure as a propellant for the powder. The devices come from the US, where dental units have a foot pedal for air pressure control. European dental units are usually constructed, so that the complete air pressure can be regulated (approx 3bar) or the practice installation (approx 6bar).

The dosage of the air pressure must be different. For this purpose little screw valves are offered on powder containers. These are difficult to control. The aids offered from the US require separate air outlets to be installed in all rooms where the use of CEREC is planned. This means costs through a service technician and unappealing air outlets from the floor connection of the unit. Experience has shown that this displeases the dentists.