Purpose: The purpose of this study was to compare the chemical and physical properties of eight contemporary direct pulp capping materials. Methods: Materials included: calcium hydroxide-based (Dycal®, Lime-LiteTM, and Ultra-BlendTM plus), bioceramic-based (MTA Angelus®, Biodentine®, TheraCal LC®, Ceramir® Protect LC), and resin ionomer-based materials (Bio-Cap®). Calcium release and pH changes were measured after one, seven, 28, and 90 days in 36.8 degrees Celsius of deionized water. Water sorption and solubility were calculated with weight loss after 90 days. Results: Biodentine® (965.5 ppm) and MTA Angelus® (921.2 ppm) released significantly more cumulative calcium ions (P<0.05), followed by Ceramir® Protect LC (450.8 ppm) and Dycal® (268.1 ppm); Lime-LiteTM had the least amount of calcium ions. After 90 days, Biodentine® and MTA Angelus® showed significantly higher pH (P<0.05), while Bio-Cap® and Lime-LiteTM had limited effects in raising the pH to alkaline. Dycal® presented the most weight loss (26 percent, P<0.05) after 90 days. Conclusions: Biodentine® and MTA Angelus® demonstrated more favorable in vitro characteristics for clinical pulp capping purposes, while Lime-LiteTM had no effect in releasing calcium ions and limited influence in raising pH value.