Dimensional accuracy of upper complete denture bases: the effect of metallic flask closure methods

Abstract

Flask closure methods should be considered when the denture base stability and comfort of the patient are being assessed during clinical use of the dentures.

Effect of double flasking and investing methods on artificial teeth movement in complete dentures processing

“…In routine laboratory conditions, thermal polymerisation shrinkage owing to flask cooling and the distortion resulting from the stress released after denture base removal from the stone cast are associated events, which decrease the accuracy of the denture adaptation and stability 3 that can result in increased VDO 3,14,15 , and changes in the position of artificial teeth 14 .…”

“…The flasking method during the prostheses processing can significantly influence the ability to prevent alterations in artificial teeth positioning during prostheses manufacturing 3,5 . Prostheses packed in PVC monomaxillary flasks were more distorted than those packed in PVC‐DF 9 .…”

“…These results can be explained considering that maxillary prostheses require a greater content of acrylic resin to be processed. Thus, it is expected that maxillary prostheses would be more affected by the combination of polymerisation shrinkage, different thermal contraction during flask cooling methods and the strain accompanying stress release during deflasking, and therefore present higher linear alterations 3 .…”

“…However, dimensional changes and distortions are inherent to laboratory procedures 2 . In the acrylic resin flasking procedure, the combination of polymerisation shrinkage, different thermal contraction during flask cooling methods and strain accompanying stress release during deflasking can cause linear alterations 3 . These changes allow artificial teeth to move, leading to alterations in vertical dimension of occlusion (VDO) 4,5,6,7 .…”

Teeth movement in denture and implant-supported prosthesis influenced by microwave flask systems

“…However, this prosthetic rehabilitation was also manufactured with acrylic resin that shows dimensional change inherent to the polymeric material. In addition, the changes that occur on the denture base due to factors as polymerization cycle, 12 base thickness and amount of residual monomer, 13 closure flask method, 14,15 and commercial types of acrylic resin, 16 as well as those that occur on teeth displacement as inclusion and polymerization, 17 and closure and flask cooling, 18 can, by analogy, interfere on the teeth displacement in implantsupported prostheses. Associated to dimensional acrylic resin changes, the other factor that must be considered significant, in relation to implant-supported prosthesis, is the passive fit of the metal bar on the implants.…”