Q&A

We received many excellent questions regarding the functionality of the furnaces and improvement of the restorations which we want to share with you. This short guide categorizes the symptoms in three main areas: Metals, Conventional ceramics, Pressable ceramics.

Symptoms	Cause	Solutions
Conventional materials	(Can also apply to Pressables)
METALS
Porosities, cavities, fractures of the metal framework	Sprueing recommendation by manufacturers or recommendations on Pre-heating and casting temperatures were overlooked	Check manufacturer request for casing metal and investment
Ceramic Shades ares too bright and too Opaque	Preheating temperature set too high	Decrease Preheating Temperature
CERAMIC
Ceramic Material is too Porous	Firing temperature too low	Increase firing Temperature
	Vacuum Pump actuated too late	Decrease Preheating or VacuumTemperature
	Attained Vacuum value too Low	Check vacuum Pump / or leaks
Ceramic surface too rough	Firing temperature too low	Increase firing Temperature
Ceramic surface has too little lustre	Holding time too short	Extend Holding time
Ceramic surface has too much lustre	Firing temperature is too high	Decrease firing Temperature
Edges and contours are not clearly defined but round	Holding time too long	Shorten Holding time
Cracks caused by compression:Horizontal cracks in the incisal region or in the bridge pontic	Extend cooling required by manufaturer of ceramic and metal but not complied	Check CTE of the Alloy/use 3 minutes at 850 degrees c. cooling required if CTE > 14.2 (standard)
	Cooling temperature too low	Increase Cooling Time
	Cooling temperature too short	Extend cooling duration/phase
Cracks cause by tension	Incorrect Alloy	Check alloy compatibilitty( CTE)
Crack ceramic surface	Ceramic CTE is too high due to extend cooling or low heat rate or too thin framework wall	Respect wall thikness/ check CTE of CERAMIC and cooling instruction per manufacturer
Bubbles	Metal or ceramic inpurities caused by improper grinding instruments	Use only tools specifically design for metals and ceramics use only stagger toothed tungsten- carbide cutlers
	Paste opaques did not dry correctly	Extend predrying phase according to manufacturer's instruction
	Entrapped Air	Extend predrying phase according to manufacturer's instruction
	Too much opaque thinner	Extend predrying phase according to manufacturer's instruction
	Paste opaque apply too thickly	Will require ceramic rework
Pressables
Object not completely pressed	Insufficient material quantity	Calculate weight of Wax including sprues to determine number ofceramic ingots
	Wax layer was too thin	Minimum wax layer should be 0.5 mm
	Press Temperature too low	Increase slowly temp. to find melting point of the ingot (vary between different furnaces need to be adjusted by trial and error). Contact us for specific
	Press time too short	Increase Pressing time
	Press pressure too low	4.5 Bar For 1 X and up to 5.5 BAR for 2X
Press streaks on the margins of crown	Incorrect sprueing	Inlays with margin should be facing to the outside and at the same height also minimum of 3 mm sprue and short as possible
Press steaks on wax objects and the press sprues	Crack in the investment materials	Adhere to the working instructions, observe setting time and right ratio of water and liquid
Burst investment ring after Pressing	Ring is not parallel to the plunger. Pressure or temperature too high or/insufficient wall of the investment	Check parallelism of the cylinder. Check Program Parameters and keep 10 mm from the border of the cylinder
Crack in the Press Ceramics	Incorrect procedure with ZR	use suitable tool for work on ZR
Crack in the Press Ceramics	oveheating some area of the press ceramic during processing	Decrease temperature and increase preheat
Crack in the Press Ceramics	Excessive blasting during devestment	Sandblast, 50 micron at max 2 Bar
Crack in the Press Ceramics	Wax did not burn totally	Use Wax adapted to pressing system
Crack in the Press Ceramics	Incorrect sprueing	ensure correct sprueing
Bubbles in the press Ceramics	Press temperature too H=high	Reduce Press Temperature
Bubbles in the press Ceramics	Wax didn't burn totally	Change Wax to one adapted to pressable
Bubbles in the press Ceramics	ZR was not clean correctly before waxing	Clean ZR before any Waxing
Inclusion of investment into the Press element	Sprues are not wax properly	Ensure smooth transition short and big sprue
Inclusion of investment into the Press element	Edges are too sharp	Ensure smooth transition short and big sprue
Discoloration and white spot	Press Temperature too high	Try with lower temperature for a longer time
Discoloration and white spot	Check wax bonder or liner	Use only products adapted top Press systems