Background: Pulpitis, apical periodontitis, and chronic periodontitis are the most common dental diseases and being the leading cause of tooth loss in adults. Aims: To unravel the changes and the interrelation of the biochemical and immunohistochemical levels of matrix metalloproteinase-1 (MMP-1) in the gingival crevicular fluid (GCF) and teeth specimens of patients with different dental diseases. To test the influence of these changes on disease severity. Materials and methods: The GCF and tooth specimens were collected from 20 patients with chronic irreversible pulpitis (CIP), and similar number of patients with chronic periapical lesion (CPL), and chronic periodontitis (CP) in addition to 20 healthy controls. Results: Statistically significant increase were found in the mean concentration of GCF-MMP1 of the patients within the CP and CIP groups over those of CIP and CPL groups (P<0.001). Highly significant elevation (P<0.001) in the means of cell with positive expression of the MMP-1 in all patient groups compared with the mean of the control group. The highest percentages of the MMP-1 expression (P=0.000) above the median values were seen in CPL (13.3% vs 86.7%) followed by both CIP and CP groups (9.1% vs 90.9%). Using Receiver Operating Characteristic (ROC) curve analysis, the GCF MMP-1 was found to be an effective test in CP group at reading ≥ 0.83 pg/ml and in CPL at cut off value of ≥ 2.24 ng/ml. Conclusion: The MMP1 plays a crucial role in the demolition of periodontal tissue and the GCF analyses can be used as noninvasive method to unravel these changes.