Periodontal tissue is composed of epithelial-derived and mesenchymal-derived tissues, including alveolar bone, periodontal ligament, cementum, and gingival epithelium. Due to the complex structure composed of epithelial and mesenchymal tissues, a deep understanding of the characteristics of this tissue is necessary for elucidating the pathophysiological mechanisms underlying the development of periodontal diseases and for developing effective methods for preventing and treating periodontal diseases.

Using laser microdissection and microarray analysis, we identified factors that are specifically expressed in the junctional epithelium. For example, peptides were specifically expressed in the junctional epithelium. Furthermore, neutrophils were present only in the junctional epithelium and were continuously prepared to respond to infection. On the other hand, the gingival epithelium also showed expression of factors such as tumor necrosis factor (TNF)-α, which are involved in periodontal tissue destruction, suggesting a dual role of the gingival epithelium of 'defense' and 'destruction.'

Periodontal ligament stem cells present in the periodontal ligament possess multipotent differentiation capability and are expected to be a useful starting material for periodontal tissue regeneration. We cultured periodontal ligament stem cells in spheroid culture (3D culture) and investigated their application in tissue regeneration. As compared to monolayer-cultured periodontal ligament stem cells, periodontal ligament stem cell spheroids showed significantly increased expressions of stem cell markers such as OCT4 and NANOG. Furthermore, when the culture was carried out under osteoblast differentiation-inducing conditions, enhanced calcification was also observed. When periodontal ligament stem cell spheroids were transplanted into cranial bone or periodontal tissue defect models, the amount of tissue regeneration was significantly greater than that noted after transplantation of cells from the monolayer culture group. These findings suggest that periodontal ligament stem cells and spheroid culture technology are useful for tissue regeneration.

Dental treatments frequently involve pain, tension, and vibration, which can impose mental and physical burdens on the patients, thereby triggering stress responses. The purpose of this study was to compare the effects of scaling and root planing (SRP) and subgingival scaling with a Er:YAG laser on the biological stress responses.

Thirty-two patients with periodontitis were randomly assigned to two groups (the scaler group and the laser group). For three teeth with periodontal pockets of 5 mm or more, SRP using a hand scaler or subgingival scaling with an Er:YAG laser was performed under local anesthesia. Vital signs were measured immediately before treatment, immediately after induction of local anesthesia, and immediately after treatment. Blood samples were collected before treatment and immediately after treatment, and periodontal examinations were conducted before treatment and 12 weeks after treatment.

Immediately after local anesthesia, significant increases of the body temperature, blood pressure, and pulse rate were observed in both groups (p<0.05), along with a significant decrease of the oxygen saturation (p<0.01). Similar values were obtained immediately after treatment. Improvement of the periodontal parameters was observed in both groups at 12 weeks after treatment. The maximum clinical attachment level was significantly reduced only in the laser group. No significant differences were observed between the two groups in any other parameters.

These results indicate that local anesthesia markedly alters the vital signs. In addition, no stress responses were observed to either SRP or subgingival scaling with a Er:YAG laser under anesthesia, indicating the absence of any differences between the two groups.