Effects of Disinfecting Alginate Impressions on the Scratch Hardness of Stone Models

Abstract

INTRODUCTIONDisinfection of impressions is required in order to prevent the transmission of infectious diseases in dentistry 1-3） . The disinfection method and the brand of alginate impression material have been reported to have varying effects on the resultant stone model in terms of surface roughness, reproduction of detail, dimensional stability, and deformation 4-9） . Stone models are expected to be sufficiently hard in order to resist marginal fracture and abrasion during curving. However, disinfection of impressions may reduce the surface hardness of stone models due to effects arising from water absorption, impression dissolution, or disinfectant solution remaining on the impression surface. Therefore, a hardness evaluation study is required to establish a suitable disinfection method whereby the reproducibility of stone models will not be adversely affected by disinfected impressions. The measurement conditions for a scratch hardness test for stone models were investigated in a previous study 10） . Based on the results of the previous study, we conducted the hardness test for stone models and investigated the effects of disinfecting alginate impressions on the scratch depth of resultant stone models. MATERIALS AND METHODSThe materials listed in Table 1 were used according to the instructions of the respective manufacturers.Eleven brands of alginate impression material （de-tails in Table 1） were mixed for 15 seconds using an automatic alginate impression material mixer （Rakuneru, GC, Tokyo, Japan） . A type V dental stone （New Plastone, GC, Tokyo, Japan） was first mixed by hand for 45 seconds and then vibrated for 30 seconds.Disinfectants were 1％ sodium hypochlorite solution （SH） and 2％ glutaraldehyde solution （GA） . The disinfectant products, Purelox （Oyalox, Tokyo, Japan） and Sterihyde （Maruishi Pharmaceutical, Osaka, Japan） , were diluted with distilled water to concentrations of 1％ and 2％ respectively.Stone specimens were produced using the equipment shown in Fig. 1 This study investigated the effects of disinfecting alginate impressions on the scratch depth of resultant stone models. Eleven brands of alginate impression material and two disinfectants, 1％ sodium hypochlorite and 2％ glutaraldehyde, were used. Impressions were immersed in disinfectant solutions or stored in sealed bags after spraying with disinfectants, and then poured with a type V dental stone. The scratch depth of the stone model obtained from disinfected impression was measured. The storage of alginate impressions after spraying with disinfectants did not increase the scratch depth of resultant stone models. However, the effect of immersion in disinfectants on scratch depth varied with the brand of the alginate impression material.

Surface detail reproduction and dimensional accuracy of stone models: influence of disinfectant solutions and alginate impression materials

“…The cast surfaces of impressions that were rinsed with water and stored in sealed plastic containers at 100% humidity were better than those that were poured immediately after rinsing (14,21). According to Tan et al (14), this is due to a decrease in exudates from syneresis (which retard the setting of dental plaster and affect the cast surface) during storage.…”

Influence of water/powder ratio in the mineral and synthetic casts

“…25, type IV casts, 1 h after mixing, must have a compressive strength of 5000 psi, equivalent to 351.53 kgf/cm 2 (ADA 25) 11 . The compressive strength of the casts is directly associated with their surface hardness and resistance to abrasion during handling in a clinic or laboratory, or during die casting, articulation, cutting, and duplication of the model [12][13] . The highest resistance to diametral traction of these casts occurs 120 min after setting 14 .…”

The Effect of disinfection of Extended-Pour alginate impressions on the surface roughness of stone casts

“…This may due to the lower amount of exudates results from syneresis during impression storage which was reported to decrease the surface roughness of the casts (36) . Hiraguchi et al (36) studied the Influence of two disinfectants, 1% sodium hypochlorite & 2% glutaraldehyde on the resultant models as regards the scratch depth from eleven brands of alginate.…”