Background. For a long time, the impact of severe periodontitis on the pulp has been the focus of periodontal clinical research. Whether the teeth with severe periodontitis should be treated with pulp has also become the focus of clinical research. Aims. To explore the effect of periodontal endodontic therapy combined with DL therapy on severe periodontitis. Materials and Methods. The clinical data of 100 patients with severe periodontitis from January 2020 to July 2022 were selected and included in the retrospective study. According to the different retrieval treatment methods, they were divided into the control group and the treatment group with 50 cases in each group. The control group received periodontal endodontic treatment, and the treatment group received DL treatment on the basis of the control group. The differences in periodontal probing depth (PD), toothache degree, bleeding index (BI), inflammatory factors, plaque index (PLI), and attachment loss (AL) between the two groups were compared and analyzed. Results. After 3 months of treatment, the bleeding index (BI), plaque index (PLI), and periodontal probing depth (PD) of the treatment group were significantly lower than those of the control group, and the difference was statistically significant ( P < 0.05 ). The attachment loss (AL) of the group was not significantly different from that of the control group ( P > 0.05 ). Before treatment, there was no significant difference in the levels of inflammatory factors between the two groups ( P > 0.05 ). After 3 months of treatment, the levels of IL-6 and CRP in the treatment group were significantly lower than those in the control group, and the difference was statistically significant ( P < 0.05 ). Before treatment, there was no significant difference in the levels of inflammatory factors between the two groups ( P > 0.05 ). After 3 days of treatment, the VAS score of the treatment group was significantly lower than that of the control group, and the difference was statistically significant ( P < 0.05 ).After treatment, there were no complications during follow-up in the two groups. Conclusion. The application of DL treatment has a significant effect, which can promote the healing of periodontal tissue, reduce the depth of periodontal pockets, and reduce the degree of toothache, thereby providing a reference for clinical treatment.