Background & objections: Changes in root surfaces in the environment of periodontal pocket hinder regeneration of the periodontal tissues. Periodontal treatment, therefore, must create a root surface compatible for the cells that mediate repair and regeneration of the periodontal tissue. To achieve this, a procedure called root biomodification is recommended as an adjunct to scaling and root planing. Various agents, namely citric acid, phosphoric acid, ethylene diamine tetraacetic acid (EDTA), tetracycline hydrochloride, hydrogen peroxide, fibronectin, enamel matrix proteins, recombinant human growth factors, dentin bonding conditioners, etc., have been tried for root biomodification. However, the role of root biomodification in regeneration of the periodontal tissues is questionable. Considering this, an in vitro study was carried out to evaluate the morphologic characteristics of the periodontitis-affected roots after biomodification using citric acid, ethylene diamine tetraacetic acid (EDTA) and tetracycline hydrochloride (HCl) solutionunder scanning electron microscope (SEM). Since first step in periodontal regeneration is the adherence of blood clot to the root surfaces, the study is also intended to evaluate the attachment behaviour of blood clot to those biomodified roots. Materials and Methods: The present study was carried out on periodontally compromised human anterior teeth (n=40) comprising of maxillary (n=20) and mandibular (n=20). They were randomly divided into four groups (comprising ten teeth in each group) based on the biomodification agent used: Group 1 (control group): treated with normal saline, Group 2: treated with citric acid, Group 3: treated with EDTA and Group 4: treated with tetracycline HCl solution. Two specimens were prepared from each tooth. One of the specimens was evaluated for the patency of dentinal tubules after treating with the allotted biomodification agent, while other was evaluated for clot adhesion following treating with blood after biomodification under SEM. Results: Numbers of the patent dentinal tubules and scores of the blood clot adhesion were found to be significantly higher in all the three test groups compared to that of the control group. Conclusions: Biomodification of root surfaces may play a significant role in accomplishment of periodontal new attachment by increasing the patency of dentinal tubules and making the root surfaces more conducive for blood clot adhesion.