Background: The aim of this study was to analyze the relationship between extent, severity (stage), and rate of progression (grade) of periodontitis with systemic diseases as well as smoking using a large database. Methods: Patients’ records identified in the BigMouth Dental Data Repository with a periodontal diagnosis based on the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions were evaluated. Patients were further categorized based on extent, severity, and rate of progression. Data were extracted from patients’ electronic health records including demographic characteristics, dental procedural codes, and self-reported medical conditions, as well as the number of missing teeth. Results: A total of 2069 complete records were ultimately included in the analysis. Males were more likely to have generalized periodontitis and stage III or IV periodontitis. Older individuals were more likely diagnosed with grade B and stage III or IV periodontitis. Individuals with generalized disease, grade C, and stage IV demonstrated a significantly higher number of missing teeth. Higher numbers of tooth loss reported during supportive periodontal treatment were noted in generalized disease and stage IV periodontitis. Multiple sclerosis and smoking were significantly associated with grade C periodontitis. Conclusions: Within the limitations of this retrospective study that utilized the BigMouth dental data repository, smokers were significantly associated with rapid progression of periodontitis (grade C). Gender, age, number of missing teeth, and number of tooth loss during supportive periodontal treatment were associated with disease characteristics.