Effect of flasking and polymerization techniques on tooth movement in complete denture processing.
OBJECTIVE
The purpose of this study was to compare the artificial tooth positional changes following the flasking and polymerization of complete dentures by a combination of two flasking methods and two polymerization techniques using computer graphic measurements.


METHODS
Four groups of waxed complete dentures (n = 10) were invested and polymerized using the following techniques: (1) adding a second investment layer of gypsum and conventional water bath polymerization (Control), (2) adding a second investment layer of gypsum and polymerization with microwave energy (Gypmicro), (3) adding a second investment layer of silicone (Zetalabor) and conventional polymerization (Silwater), and (4) adding a second investment layer of silicone and polymerization with microwave energy (Silmicro). For each specimen, six segments of interdental distances (A to F) were measured to determine the artificial tooth positions in the waxed and polymerized stages using software program AutoCad R14. The mean values of the changes were statistically compared by univariate ANOVA with Tukey post-hoc test at 5% significance.


RESULTS
There were no significant differences among the four groups, except for segment D of the Silmicro group (-0.004 +/- 0.032 cm) in relation to the Gypwater group (0.044 +/- 0.031 cm) (p < 0.05), which presented, respectively, expansion and shrinkage after polymerization.


CONCLUSIONS
Within the limitations of this study, it was concluded that although the differences were not statistically significant, the use of a silicone investment layer when flasking complete dentures resulted in the least positional changes of the artificial teeth regardless of the polymerization technique.
Shibayama
Ricardo
R
Dental Prostheses and Occlusion, Department of Restorative Dentistry, Londrina State University, Brazil.
Gennari Filho
Humberto
H
Mazaro
José Vitor Quinelli
JV
Vedovatto
Eduardo
E
Assunção
Wirley Gonçalves
WG
D000180:Acrylic Resins / Q000737:chemistry; D002133:Calcium Sulfate / Q000737:chemistry; D003196:Computer Graphics; D003722:Dental Alloys / Q000737:chemistry; D003734:Dental Casting Investment / Q000737:chemistry; D003735:Dental Casting Technique / Q000295:instrumentation; D003764:Dental Materials / Q000737:chemistry; D003819:Denture Bases; D003779:Denture Design; D003827:Denture, Complete, Upper; D004867:Equipment Design; D005898:Glass / Q000737:chemistry; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008872:Microwaves; D011108:Polymers / Q000737:chemistry; D012826:Silicone Elastomers / Q000737:chemistry; D014093:Tooth, Artificial; D014867:Water
D000180:Acrylic Resins; D003722:Dental Alloys; D003734:Dental Casting Investment; D003764:Dental Materials; D011108:Polymers; C488492:QC 20 (denture base resin); D012826:Silicone Elastomers; C009753:fiberglass; C539103:onda cryl; D014867:Water; D002133:Calcium Sulfate