Untreated periodontally‐involved extracted human teeth were cleaned of plaque and calculus and then treated with chemicals having the potential to dissociate or degrade endotoxin. The count of attached gingival fibroblast cells after 48‐hours of culturing was used as a measure of the biocompatibility of the diseased root surface. Paired specimens compared to their phosphate‐buffered saline controls demonstrated no significant differences for the use of sodium lauryl sulfate and EDTA, plasma protein fraction, immune serum globulin, citric acid, or sodium deoxycholate followed by immune serum globulin.