BEGO USA | eTechTip


	May 2011 \| Courtesy of BEGO USA Controlling expansion during seasonal changes
	^{BEGO and other manufactures use expansion measuring instruments to measure the different percentages of mixing liquid and the effects of expansion.} Investment liquid has an important impact on the setting expansion of crowns & bridges. The greater the concentration of mixing liquid the more the investment will expand. Thus, 100% liquid usage results in maximum setting expansion. Other factors can also effect and influence the expansion — therefore it is extremely important to achieve a consistent working environment in the laboratory. Storage: investment should be under consistent conditions keeping in mind temperature as well as humidity levels — 72°F is an optimal temperature. If the material has a temperature far below 72°F when being used, the castings may have small bubbles all over the surface and the copings may not fit. Mixing: procedures should be identical for mixing each type of investment with special attention to the mixing speed, bowls and spatula geometry. Volume: different volumes of material may influence the final fit. Rings: when using the ringless system — remove the ring after 12-20 minutes to maximize expansion (depending on the ring size). Pressure: to achieve a clean casting, take advantage of using a pressure vessel with 25-55psi. Preheating: keep preheating temperatures consistent for either conventional or rapid burnout. Hold: the final temperature should be held for at least 45 minutes — depending on mould size and capacity of oven. BEGO hopes these helpful tips and reminders assist the laboratory conquer consistent expansion.

	For more information, call your local dealer or BEGO USA, 1.800.342.2346 \| www.begousa.com