The effect of disinfectant agents on dimensional stability and surface roughness of a tissue conditioner material.

Purpose: The aim of this study was to determine the effect of disinfectant procedures on the dimensional stability and surface quality of a tissue conditioner used as a functional impression material. Materials and Methods: A tissue conditioner (Visco-gel) used as a functional impression material was disinfected by immersion in 5.25% sodium hypochlorite or 2% glutaraldehyde solutions for 10 or 20 minutes, respectively. The control group consisted of specimens (n=10) that were not treated by disinfectants. For testing the dimensional stability, impressions of an aluminum edentulous arch with three reference points were made. After 24 hours of storage in distilled water, the specimens were treated by one of the disinfection procedures. Impressions were poured and, subsequently, 50 stone casts were measured with a Nikon profile projector. For surface roughness evaluation, disks that contained Visco-gel were pressed against glass slides. The disks were then stored in distilled water for 24 hours. After disinfection, 50 disk-shaped dental stone casts were prepared. Surface roughness values were determined using a profilometer. For each test, data were subjected to two-way analysis of variance (ANOVA) followed by Tukey's test (α = 0.05). Results: The results of the dimensional stability test showed that immersion of Visco-gel impressions in 5.25% sodium hypochlorite solution or 2% glutaraldehyde solution did not significantly change the anteroposterior (AP) and cross-arch (CA) distances of the resultant stone casts when compared to the control group (P>0.05). The surface quality of dental stone casts formed by Visco-gel did not change significantly when impressions were immersed in the disinfectant solutions for either 10 or 20 minutes, or when stored in distilled water (P>0.05). Conclusion: The results showed that the disinfectant solutions used in this study did not have a significant effect on the surface quality and dimensional accuracy of Visco-gel as a functional impression material.

Effect of chemical surface treatments and repair material on transverse strength of repaired acrylic denture resin.

PURPOSE: This study was performed to evaluate the transverse strength of a denture base resin (H), repaired with an autopolymerizing acrylic resin (A) or a visible light-curing (VLC) resin (T) following the use of three chemical solvents: methyl methacrylate monomer, aceton or chloroform. MATERIALS AND METHODS: Eighty specimens (65.0 x 10.0 x 3.3 mm) of H were fabricated and stored in distilled water at 37 degrees C for seven days. Specimens were divided into eight equal groups of 10. In each group, specimens were sectioned in the middle to create a 10 mm gap. Two groups served as controls and had no surface treatment. They were repaired with A or T materials. In the remaining six experimental groups, specimen surfaces were treated with ac for 30 sec or mma for 180 sec or ch for 5 sec. Then A or T material was placed on the treated surfaces, using the same preparation molds. After seven days' storage at 37 degrees C, the transverse bond strength (MPa) of the specimens was measured using a three-point bending test. A two-way ANOVA and a Tukey HSD were performed to identify significant differences ( P < 0.05). The nature of the failures was noted as adhesive, cohesive or mixed. RESULTS: Significant differences were found between the controls and experimental groups ( P < 0.05). In the control groups, repair with A showed significantly higher strength (60.3 MPa) than those repaired with T (51.3 MPa). Mean transverse strength of experimental specimens repaired with A was (75.06 MPa) which was significantly greater than those repaired with T (67.9 MPa). Although surface treatment increased repair strength, no significant differences were detected between the effects of the chemical etchants. CONCLUSIONS: The autopolymerizing resin exhibited significantly higher repair strength than VLC resin. The transverse strength of the repaired specimens was increased significantly after chemical treatments.