To explore the viability of used toothbrush as a source of gene expression and comparison of the same among tobacco, alcohol, diabetic and hypertensive subjects. Materials and methodsFourteen subjects with a history of type 2 diabetes mellitus (T2DM) and hypertension were allocated to Group I, 14 subjects with tobacco and alcohol habits allocated to Group II and 14 healthy subjects allocated to Group III. Genetic materials retrieved from the used toothbrush of the study subjects were assessed for genetic expression of cyclin-dependent kinase 4 (CDK4), Bcl-2-like protein 4 (BAX), cyclin-dependent kinase inhibitor 2A (CDKN2A), B-cell lymphoma 2 (BCL2), G-protein beta-3 (GNB3), and subunit gene and transcription factor 7-like 2 (TCF7L2) by polymerase chain reaction (PCR). ResultsBAX gene showed reduced expression in tobacco and alcohol users (p=0.0497). BCL2, CDK4, and GNB3 showed no significant difference in expression in both the groups and with control. CDKN2A was expressed at a lower level in Group I and II participants. TCF7L2 showed higher expression in Group 2 participants (p=0.001). ConclusionThe study concluded that used toothbrush is a reliable source for genetic expression. There was no difference in BCL2, CDK4, and GNB3 gene expression between subjects with systemic disease, adverse habits and healthy controls. There is a downregulation of BAX and upregulation of TCF7L2 gene in subjects with adverse habits.