The Effect Of Three Different Investing Maetrials On Complete Dentuer Flasking Deformation

Objective:To evaluate the influence of different investing materials on completedenture flasking deformation.Methods:The model casts were prepared from the standard silicone impressions, trialcomplete mandibular dentures were made by placing the wax and artificial teeth onthe model casts, then the crossing lines over the4reference points were drawn,among them3points were on the artificial teeth,1point on the modal base. The4reference points were located at the distal lingual cusp of the left second molar (A),the distal lingual cusp of the right second molar (B), the midpoint of incisal edge onright mandibular central incisor(C),and the midpoint of the posterior line of gypsummodal(O),respectively.The each distance of OA,OC,AC,AB were measured threetimes by vernier caliper(accuracy of0.01mm).The denture wax casts were investedby a plaster, a dental stone, and a dental stone together with a silicone, respectively.8trial dentures were randomly chosen from above each group. For Group1onlyplaster was used and for Group2only dental stone was used during processing. ForGroup3a silicone layer around the wax was placed before a dental stone was pouredfully. Packing and polymerization were performed under the same conditions. Thedistances between marked points were measured after flasking process, assigned asOA’,OC’,AC’,AB’.The change of the distances between reference points before andpost processing was calculated. F test and Kruskal-Wallis H test were applied todetect statistical significance.Results: The distance between A and B (F=3.768,P=0.040)and the mean of total distance among O,A,B and C(F=4.830,P=0.019) were statistically significantamong the three groups. The deformation variance of Group1is maximum. Group2is slightly smaller than Group3. Smoothness (χ~2=17.575,P<0.001)was statisticallysignificant among the three groups.Conclusions: The plaster caused the maximum movement. Dental stone showed theminimal tooth movement, the dental stone along with the silicone made a similarmovement as with single dental stone but resulted in a smoother surface.