Statement of problem: Although the primary use of tissue conditioners is to treat abused mucosa, these materials are also frequently used as functional impression materials. No information was identified on the effect that these materials may have on the surface of the resultant dental stone cast.
Purpose: This study evaluated the compatibility of 3 tissue conditioners with dental stones and changes in surface conditions over time.
Material and methods: Three tissue conditioners (COE-comfort, Soft-conditioner, and Visco-gel) and 4 dental stones (Capstone DF, New Plastone, Die Stone, and New Fujirock) were evaluated. One impression material (Examixfine) was used as a control. Tissue conditioner disks were made by pouring freshly mixed material into a polypropylene container, pressing the material down with a glass plate, and then removing the plate 2 hours later. The disks were then stored in distilled water for 0 or 24 hours, or 3, 7, or 14 days. Subsequently, each dental stone was mixed and poured over the top of each disk and allowed to remain for 60 minutes. Twenty-five disk-shaped specimens, 18 x 2 mm, for each tissue conditioner/stone cast combination were prepared. Mean surface roughness (Ra) values of the dental stone casts made from the tissue conditioners were determined using a profilometer. Five measurements for each specimen were made. Data were analyzed with 1- and 3-way analysis of variance and the Student-Newman-Keuls test (alpha=.05). Detail reproduction was also determined using a ruled test block, as specified in ISO specification 4823.
Results: Contribution ratios determined by 3-way analysis of variance indicated that the surface roughness values were significantly more influenced by the time of immersion in water ( P <.0005, contribution ratio rho=37%), than the type of tissue conditioner ( P <.0005, rho=19%) or dental stone used ( P <.0005, rho=1%). The best surface quality was obtained with a New Fujirock cast (0.81 +/- 0.06 microm), followed by New Plastone (0.83 +/- 0.12 microm) and Die Stone (0.85 +/- 0.05 microm) casts, in combination with Visco-gel without immersion in water, and those were nearly equivalent in surface roughness to a Die stone cast from Examixfine. The surface roughness values of all specimens, especially the COE-comfort/stone cast combinations, significantly increased with tissue conditioner immersion time ( P <.0005). Visco-gel tended to produce a better surface quality during the test periods than the other materials. All stone casts made from the tissue conditioners not immersed in water reproduced 20-microm or 50-microm lines, while the detail diminished over time with immersion.
Conclusion: The type of tissue conditioner, and especially immersion time, had a significant effect on the surface quality of dental stone casts. The type of dental stone used is less important.