Conventional acrylic processing has always been a challenge due to three issues that affect the fit of denture bases. The three issues are:
1. thermal expansion and contraction of acrylic
2. recovery distortion occurring in deflasking
3. adaptive accuracy
Thermal expansion and contraction occurs during the process of curing and cooling acrylic. Acrylic can be cured in a one stage process at 158°F for 8 hours, or a two stage process at 1.5 hours at 158°F and the second stage is 212°F for 30 minutes. The flask is then slowly cooled to room temperature. If the flask is cooled too rapidly it will cause stress in the acrylic resulting in the acrylic base no longer fitting flush against silicone or gypsum products.
Recovery distortion is a common technique problem. Improperly de-flasking a denture can cause distortion of the denture base. Common errors are not using a flask ejector, using a hammer on the knockout plate and outer investment, and prying the denture off the cast with a knife or pneumatic chisel. Processed acrylic is easily removed from the denture if the application of tin foil substitute is used correctly.
Adaptive accuracy is where the acrylic base fits the cast and mouth without shifting or dislodgement. The critical points of adaptive accuracy are: the alveolar ridge, flanges, anterior palate, and glandular tissue. Glandular tissue is the anatomical region where the posterior seal is placed. If the impression material is too viscous, or too much pressure is used in custom tray or denture placement it will affect the seating of the denture base in the posterior area.
The Avadent digital milled denture addresses and corrects all three processing concerns! First, there’s no human involvement so there can be no human error. Thermal expansion/contraction is eliminated because the denture base is milled at room temperature from a pre-manufactured solid acrylic puck that is created under extreme pressure to ensure density and stability.
Recovery distortion is eliminated because the gypsum products have been eliminated – there’s no flask so no de-flasking.
Adaptive accuracy is increased because Avadent provides the correct impression materials that matches the resiliency of mucosa and doesn’t compress or displace the tissue, providing the most accurate denture base ever made.