Amalgam strength resistance to various contaminants

Purpose: The purpose of this study was to quantify the relative strength tolerance of 1-day and 30-day amalgam following saturation contamination with water, saliva, blood, and handpiece lubricant oil during condensation. Methods and Materials: Valiant PhD XT amalgam was tested with 300 shear-strength (N=15) and 120 compressive-strength (N=6) specimens, divided into 1-day and 30-day groups, each with control, water, saliva, blood, and lubricant oil contamination samples. Shear specimens were condensed in 4 3 4-mm anchor wells inundated with contaminant fluids before adding a ring mold with 3.5-mm-diameter central hole adapted immediately to the top for continued condensation under contaminant-submerged conditions. Compressive specimen samples were condensed while completely inundated by each contaminant using the American Dental Association Specification No. 1 amalgam mold apparatus. All specimens were tested with the Instron E3000 and E10000 at 0.5 mm/min, with data statistically evaluated using the Kruskal-Wallis procedure with IBM SPSS v25 and Wilcoxon signed ranks test. Results: Shear test values (mean6SD) following intracapsular and extracapsular contamination after 30 days under 100% humidity at 378C were as follows: control, 30.9765.41 MPa; water, 30.63 64.41 MPa; saliva, 27.54 64.56 MPa; blood, 24.92 63.48 MPa; lubricant oil, 26.06 64.06 MPa. Compressive strengths (6SD) of similarly contaminated samples were as follows: control, 447.7 676.3 MPa; water, 343.6 670.1 MPa; saliva, 307.7 624.0 MPa; blood, 281.6 635.2 MPa; lubricant oil, 227.8 616.9 MPa. Conclusions: Saliva, blood, and handpiece oil diminish compressive strength significantly, but water shows no statistically significant effect (p.0.05). Amalgam 30-day shear strength is significantly altered by contamination with water, blood, or handpiece lubricant oil (p,0.05). Remaining amalgam strength after extensive contamination may still be clinically functional relative to a previous ADA recommendation and when compared with resin-based direct restorative materials.