An experimental study on particular physical properties of several interocclusal recording media. Part II: Linear dimensional change and accompanying weight change.
OBJECTIVE
The purpose of this study was to evaluate the linear dimensional change and accompanying weight change of several elastomeric interocclusal recording media.


METHODS
Ten 50 mm long, 8 mm wide, 3 mm deep Teflon molds and a stainless steel die were constructed for the purposes of this study. The die was made in order to produce standardized reference lines, which were used for the measurement of the linear change. After homogeneous mixing, each material was carried from the mixing pad or directly from the mixing tip to the Teflon mold. The mold was inverted onto the stainless steel die. The materials were allowed to set for the manufacturers' suggested setting time plus an additional 3 minutes to ensure polymerization of the material. An electronic scale (Galaxy 110, Ohaus, Pine Brook, NJ) was used for the measurement of the weight change of the specimens and a traveling micrometer microscope (Griffin Ltd., London, England) was used to measure the linear changes at 5 time intervals: 0, 1 hour, 24, 48, and 72 hours.


RESULTS
Analysis of variance for a significance level of 5% revealed that there was a statistically significant effect of the "material" factor on the weight changes (F= 2,229.98, p < 0.0005). There was also a statistically significant effect of the "time" factor on the weight changes (F= 2,332.04, p < 0.0005). Descriptive statistics and Tukey's Honest Significant Difference Test revealed that the elastomeric material with the greatest weight changes is polyether (Ramitec). Analysis of variance for a significance level of 5% revealed that there is a statistically significant effect of the "material" factor on the linear changes (F= 215.54, p < 0.0005). There is also a statistically significant effect of the "time" factor on the linear changes (F= 1,996.01, p < 0.0005). Descriptive statistics and Tukey's Honest Significant Difference test revealed that the elastomeric material with the smallest linear changes is polyether (Ramitec).


CONCLUSIONS
Of all materials tested, Ramitec (polyether) presented the smallest linear change at all time intervals. Addition reaction silicones presented statistically significant differences in recordings of linear changes among them only at the 1st and the 24th hour. Linear changes did not seem to be associated with weight changes.
Michalakis
Konstantinos X
KX
Division of Graduate and Postgraduate Prosthodontics, Tufts University School of Dental Medicine, Boston, MA, USA. kmichalakis@the.forthnet.gr
Pissiotis
Argiris
A
Anastasiadou
Vassiliki
V
Kapari
Danai
D
D000704:Analysis of Variance; D003760:Dental Impression Materials; D007574:Jaw Relation Record / Q000379:methods; D008422:Materials Testing; D012828:Silicones; D013997:Time Factors
D003760:Dental Impression Materials; D012828:Silicones; C056844:Ramitec