title: The influence of double flask investing on tooth displacement in dentures processed by microwave irradiation.
abstract: OBJECTIVE
  This study evaluated the influence of the bimaxillary flask (BMF) and two different investing materials on first molar inclination in dentures processed by microwave irradiation.
  
  
  BACKGROUND
  The BMF may minimise tooth displacement, saving time and improving occlusion.
  
  
  METHODS
  Forty pairs of dentures were randomised into four groups: stone wall in monomaxillary flask; silicone wall in BMF; stone wall in BMF; acrylic resin retentions and silicone in BMF. Dentures were processed by microwave irradiation. Two referential points were established on tooth surface. A microscope and a digital pachymeter were used to measure the distance between these points, and the angles α (right maxillary molar), β (left maxillary molar), α' (right mandibular molar) and β' (left mandibular molar) were calculated by the law of cosines. Data were submitted to Kruskal-Wallis (5% significance).
  
  
  RESULTS
  No difference was observed among the groups (p > 0.05). In the intra-group analysis, α was significantly different for groups I, II and III; α', for groups II and IV; β, for all groups; β', for groups III and IV.
  
  
  CONCLUSIONS
  First molar inclination was similar for monomaxillary and BMFs. The use of stone or silicone as investing materials presented the same effect on tooth inclination.
authors.affiliation: Department of Prosthesis and Periodontology, Piracicaba Dental School, State University of Campinas, Piracicaba, SP, Brazil. saudeoral@fop.unicamp.br
authors.forename: Arcelino
authors.initials: A
authors.lastname: Farias Neto
authors.forename: Rodrigo L dos Santos
authors.initials: RL
authors.lastname: Sousa
authors.forename: Célia M
authors.initials: CM
authors.lastname: Rizzatti-Barbosa
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D002133:Calcium Sulfate / Q000737:chemistry; D003734:Dental Casting Investment / Q000737:chemistry; D003735:Dental Casting Technique / Q000295:instrumentation*; D003819:Denture Bases; D003779:Denture Design; D003824:Denture, Complete; D006801:Humans; D008422:Materials Testing; D008872:Microwaves; D008963:Molar; D058105:Polymerization; D011143:Polyvinyl Chloride / Q000737:chemistry; D012826:Silicone Elastomers / Q000737:chemistry; D013499:Surface Properties; D014093:Tooth, Artificial
chemical_list: D000180:Acrylic Resins; D003734:Dental Casting Investment; D012826:Silicone Elastomers; C539102:vipi wave; D011143:Polyvinyl Chloride; D002133:Calcium Sulfate