This study investigated the effect of the immersion of alginate impressions in 0.5% sodium hypochlorite solution for 15 min on the dimensional changes of stone models designed to simulate a sectional form of a residual ridge. Five brands of alginate impression materials, which underwent various dimensional changes in water, were used. A stone model made with an impression that had not been immersed was prepared as a control. The immersion of two brands of alginate impressions that underwent small dimensional changes in water did not lead to serious deformation of the stone models, and the differences in the dimensional changes between the stone models produced with disinfected impressions and those of the control were less than 15 µm. In contrast, the immersions of three brands of alginate impressions that underwent comparatively large dimensional changes in water caused deformation of the stone models.

There is a concern that long-term immersion of impressions in disinfectant solutions may cause changes in the dimensions of the resulting stone casts. This study investigated the dimensional changes in stone casts resulting from immersion of five brands of addition-type silicone rubber impressions in disinfectant solutions for 30 min and 24 h. Impressions of a master cast designed to simulate an abutment tooth were immersed in 2% glutaraldehyde and 0.55% ortho-phthalaldehyde. The diameter of the stone cast was measured using a laser scan micrometer. For four brands of impression materials, 30-min immersion in disinfectant solutions produced no dimensional changes in the stone casts. For four brands of impression materials, 24-h immersion caused a significant decrease in the stone cast dimensions.

This study investigated the effects of storing impressions for 3 hours after spraying them with a disinfectant solution on dimensional change and deformation of maxillary edentulous stone models. Three brands of alginate impression materials, characterized by a small degree of contraction in 100% relative humidity, were used. The spray disinfectants used were 1% sodium hypochlorite solution and 2% glutaraldehyde solution. A stone model taken from an impression that had not been sprayed or stored was prepared as a control. The results indicated that the differences in dimensional change between the control and disinfected stone models were less than 24 µm, and that no deformation was observed in the stone models.

High-strength denture teeth (HS teeth) were developed in order to improve the hardness and wear resistance of conventional plastic denture teeth (PL teeth), while retaining their feature of easy occlusal adjustment.The objective of this study was to evaluate the abrasive wear resistance of HS teeth. We conducted wear tests and measured surface roughness using six types of anterior artificial teeth, i.e., three types of HS teeth and three types of PL teeth, the latter serving as the control.The results of the toothbrush abrasion test revealed that the HS teeth had about 5 times greater wear resistance than the PL teeth. It was also found that the type of artificial teeth and the number of abrasive wear-testing strokes had a significant (P<0.05) influence on the surface roughness of artificial teeth.

This study investigated the effects of disinfection of combined agar/alginate impressions on the dimensional accuracy of resultant stone casts. Impressions of a master cast designed to simulate an abutment tooth were prepared by combining each of two brands of cartridge-form agar impression materials with an alginate impression material. The impressions were immersed in 1％ sodium hypochlorite for 10 minutes or 2％ glutaraldehyde for 30 minutes. The remaining impressions were sprayed with these two disinfectants and then stored in sealed bags for 10, 30, 60, and 120 minutes. Stone casts obtained from the non-disinfected impressions were also prepared as control. Changes in diameter of the stone casts were then measured. Results indicated that storage for 10 minutes after spraying with 1％ sodium hypochlorite was an appropriate disinfection method for combined agar/alginate impressions, as well as immersion in 1％ sodium hypochlorite for 10 minutes.