Comparative Evaluation of Elastic Strain, Permanent Strain and Shore A Hardness in Conventional Tissue Conditioners

Tissue conditioners are used to provide time for healing of the irritated soft tissues under an old or ill fitting denture or as a diagnostic tool to assess patient's tolerance of new occlusal vertical dimension (VDO). The objective of this study was comparative evaluation of elastic strain, permanent strain and shore A hardness of 3 conventional tissue conditioners in Iran, namely Akrosoft, Softliner and Viscogel. In this experimental study, elastic strain, permanent strain and shore A hardness tests were accomplished for evaluation of physical properties of 3 conventional tissue conditioners in Iran, namely Akrosoft (Marlic Medical Ind. Co, Iran), softliner (GC company, Japan) and Viscogel (Densply Ltd, U.S.A). All of the specimens were mixed according to the manufacturer's instructions and exactly with the right powder to liquid ratio. Twenty-eight Specimens of each brand of mentioned tissue conditioners were mixed to add up to 84 specimens and restored in artificial saliva for 24 hours in room temperature for simulation of mouth conditions. Then 42 specimens (n=14), that is 14 specimens of each brand, were tested with durometer shore A hardness machine and the according numbers were recorded. The other 42 specimens (n=14) after restoring in artificial saliva for 24 hours in room temperature, were used for measuring elastic and permanent strain tests with Zwick machine. Finally, the data were analyzed by Kruskal-Wallis and Mann-Whitney tests. Statistical results from Kruskal-Wallis test showed that permanent strain in these three different groups was not different (P=0.463); however, elastic Strain and shore A hardness were statistically different (P<0.001 and P=0.007, respectively). Elastic strain and shore A hardness of the specimens also compared with two-by-two Mann-Whitney test were not statistically different. Shore A hardness of Viscogel specimens was significantly lower than Akrosoft and softliner specimens, but elastic strain of Viscogel was greater than both of them. It could be concluded that Viscogel is better from clinical standpoint.