The influence of different immersion time intervals and disinfection of tissue conditioner functional impression materials on the surface roughness of stone cast

Tissue conditioners are used as a functional impression material, to re-condition the denture-bearing mucosa abused by ill-fitting dentures and as a temporary lining material for immediate dentures. The immersion of tissue conditioners in disinfectant prior to pouring the impression can significantly affect the properties of dental stone depending on the duration of immersion. The present study aims to evaluate the effect of immersion time of tissue conditioner on the surface roughness of dental stone. Thirty specimens of tissue conditioner stone casts were prepared on cylindrical split aluminum with a lower hollow ring designed to receive the tissue conditioner and an upper ring adjusted to receive the stone mix. The thirty specimens of tissue conditioner were divided into 3 equal groups of 10 specimens according to the storage period (1hr, 24hrs and 48hrs). The three groups were subdivided into two subgroups: subgroup (a) 2% chlorhexidine (CHX) solution were sprayed on the surface of tissue conditioner specimens prior to pouring with dental stone materials while the other subgroup (b) specimens were poured with dental stone but without using (CHX) disinfection. The dental stone mixture was poured into molds and stored at room temperature for 60 minutes. The stone casts were then separated from the tissue conditioner and the surface roughness values of these dental stone casts was determined. Our results revealed a significant higher means values of surface roughness of groups (IIa and IIIa) when chlorhexidine was used compared to groups (IIb and IIIb). Comparison between subgroups (a and b) showed a statistical significance between (IIa and IIb) and (IIIa and IIIb). Based on the obtained results it can be concluded that the optimum time for using tissue conditioner as functional impression is from 24 to 48 hours after immersion. The use of 2% chlorhexidine solution disinfectant had adverse effect on surface roughness of dental stone.