Work Instruction COMFOUR®

38 OCCLUSALLY SCREW-RETAINED PROSTHETICS ON CAMLOG ® AND CONELOG ® BAR ABUTMENTS After wax-up of the framework, a suitable agent must be used to clean the fine gold margin and the area of the implant shoulder support of separat- ing medium and wax particles (e.g. with a cotton swab soaked in alcohol). EMBEDDING AND CASTING The abutment is embedded according to the instructions for use of the muf- fle system used. We do not recommend the use of wax wetting agents. The fine film from the agent can lead to a surplus of casting alloy on the margin or on the implant shoulder support. When embedding, the correct place- ment of the wax-up in the casting muffle is of importance. Volume ratios and pin angles must be selected so that the required temperature for for- mation of a metallic connection is achieved. This is particularly important for voluminous casts. The investment material must be matched with the cast-on alloy and the casting alloy used. We recommend phosphate-bound investment materials. The manufacturer's processing instructions must be observed and the mix- ing ratios and preheating times accurately observed. We recommend you do not use any investment materials for the quick heating processes (speed investment materials). The cast delay time must be kept as brief as possible. NOTES ON THE CASTING ALLOYS The casting alloy may not exceed the liquidus temperature of 1350 °C (2462 °F) in its melting range. The melting range of the high-melting cast-on gold alloy lies between 1400 °C–1490 °C (2552 °F–2714 °F). The casting alloy must be highly gold-bearing in its components and be compatible with the high-melting cast-on gold alloy. Observe the instruc- tions of the alloy manufacturer. The use of other casting alloys is not recommended. Components of an un- suitable alloy can lead to phases with reduced corrosion resistance, less stability or a low melting range due to “diffusion processes” in the border zone “casting alloy/cast-on alloy”. DEVESTMENT After casting, the cast object must be slowly cooled to room temperature and the object gently devested. IMPORTANT NOTE Never use sandblasting to devest the cast; this would destroy the precise fit of the bar base on the bar abutment shoulder (precision fit reduced, poor margin fit)! We recommend gentle devestment in an ultrasonic bath with waterjet or stripping. CASTING QUALITY If the cast object exhibits casting defects after devestment such as incom- plete effluence or casting fins/bubbles over the margin onto the implant shoulder support, the work should be repeated. The precision of the prefab- ricated bar base is severely affected and also the long-term success of the prosthetic restoration. The framework must be seated tension-free on the bar abutments. The secondary framework, e.g. electroplating technique, is then fabricated. INSERTING THE BRIDGE OR BAR CONSTRUCTION The finished bridge or bar construction is transferred to the bar abutments and screw-retained finally with new unused light blue anodized prosthetic screws, using a screwdriver, hex, with 15 Ncm.