Influence of immunosuppression on the progression of experimental periodontitis and on healthy periodontal tissue: A rat in vivo study

Microbiota-immune-brain interactions: A new vision in the understanding of periodontal health and disease

This review highlights the significance of interactions between the microbiota, immune system, nervous and hormonal systems, and the brain on periodontal health and disease. Microorganisms in the microbiota, immune cells, and neurons communicate via homeostatic nervous and hormonal systems, regulating vital body functions. By modulating pro-inflammatory and anti-inflammatory adaptive immune responses, these systems control the composition and number of microorganisms in the microbiota. The strength of these brain-controlled responses is genetically determined but is sensitive to early childhood stressors, which can permanently alter their responsiveness via epigenetic mechanisms, and to adult stressors, causing temporary changes. Clinical evidence and research with humans and animal models indicate that factors linked to severe periodontitis enhance the responsiveness of these homeostatic systems, leading to persistent hyperactivation. This weakens the immune defense against invasive symbiotic microorganisms (pathobionts) while strengthening the defense against non-invasive symbionts at the gingival margin. The result is an increased gingival tissue load of pathobionts, including Gram-negative bacteria, followed by an excessive innate immune response, which prevents infection but simultaneously destroys gingival and periodontal tissues. Thus, the balance between pro-inflammatory and anti-inflammatory adaptive immunity is crucial in controlling the microbiota, and the responsiveness of brain-controlled homeostatic systems determines periodontal health.

Impact of Photobiomodulation and Melatonin on Periodontal Healing of Periodontitis in Immunosuppressed Rats

Introduction: Periodontitis is an inflammatory disease due to bacterial origin; it has a chronic course and progresses by immunosuppressive therapy. However, adjuvant therapies such as photobiomodulation (PBM) and melatonin can reduce the severity of the inflammation and inhibit the progression of periodontitis. Therefore, the present study evaluated the effects of PBM (PBM) and melatonin, as adjuvant therapies, on periodontal healing in immunosuppressed rats with periodontitis. Methods: Random allocation was performed on 36 albino Wistar rats, divided into the following groups: control, periodontitis, immunosuppressant only, immunosuppressant+PBM, immunosuppressant+melatonin, and immunosuppressant+melatonin+PBM. Periodontitis caused by ligature in all groups, except for the control group. Subcutaneous administration of dexamethasone was performed in the immunosuppressant groups for immunosuppression. All the groups except the control group received scaling and root planning (SRP). Each group was subdivided into three equal subgroups according to the evaluation period: (A), one week, (B) two weeks (C), 4 weeks. Histological examination was done with haematoxylin & eosin and Masson's Trichrome for inflammation and periodontal healing. Statistical Analysis of the data was done by using the chi-square test. The significance level was set at P≤0.05. Results: Regarding the inflammatory response and periodontal healing, histological examination revealed statistically significant difference in all treated groups in comparison with the control untreated immunosuppressed group (P<0.001). The combined application of melatonin and PBM resulted in a best histological response presented by lower inflammatory response and better periodontal healing, when compared with all other treated groups (P<0.001). Conclusion: After considering the circumstances of this research, the combination of melatonin and PBM by a 650 nm diode laser with output power of 100 mw for one minute for three sessions appeared to be a beneficial adjunct in periodontal healing in immunosuppressed rats with periodontitis.

Tamoxifen improves homeostasis in the peri-implant bone remodeling of osseointegrated titanium implants

BACKGROUND

The purpose of this preclinical study was to evaluate the influence of tamoxifen (TAM) on the peri-implant bone remodeling of osseointegrated titanium implants in ovariectomized female rats.

MATERIALS AND METHODS

Seventy-two female rats underwent bilateral ovariectomy 20 weeks before implants placement. One titanium implant was inserted in each tibia of the animals. Six weeks following the implant surgery, animals were randomly divided into two experimental groups (n = 36), which received either saline solution (SS) or tamoxifen citrate (TAM) via gavage until euthanasia. Euthanasia was performed at 30, 60, and 90 days after the first gavage. Assessments of bone to implant contact (BIC), bone ingrowth percentage (BIN), morphological description of cellular and tissue reactions, immunohistochemistry for the detection of bone morphogenetic protein 2/4 (BMP2/4), runt-related transcription factor 2 (RUNX-2), osteocalcin (OCN) and tartrate-resistant acid phosphatase (TRAP), and bone chemical composition through scanning electron microscopy with energy-dispersive x-ray spectroscopy were performed.

RESULTS

Tamoxifen group presented higher BIC, higher BIN, higher RUNX-2 and OCN, lower TRAP-positive cells/mm2 , and no differences regarding BMP-2/4 positive cells/mm2 than SS group in all periods. TAM group also showed higher Ca/P rate than SS group.

CONCLUSION

Tamoxifen enhanced the remodeling of the bone surrounding titanium implants in ovariectomized rats.