Clinical crown height changes in adult patients after non-extraction, orthodontic treatment: a retrospective cohort study.

OBJECTIVE: To assess changes in clinical crown height (CCH) in adult orthodontic patients treated by fixed appliances to distalise the molars. DESIGN: Retrospective case series study. SETTING AND PATIENTS: A total of 30 adults with healthy periodontal tissues who received orthodontic treatment at the Department of Orthodontics, Yokohama, Japan and its related orthodontic clinic were assessed. METHODS: CCH was measured as the distance from the gingival margin to the crown plane perpendicular to the tooth axis. Treatment changes of CCH of each tooth were examined on the labial/buccal and lingual/palatal side. RESULTS: In the upper dentition, on the labial/buccal side, the CCH of the lateral incisors, canines, first premolars, first molars and second molars were increased significantly (P < 0.01), with a median value of 0.41 mm, 0.43 mm, 0.28 mm, 0.43 mm and 0.55 mm, respectively. In contrast on the palatal side, the CCH of the central incisors, first molars, and second molars decreased significantly (P < 0.01), with a median value of -0.41 mm, -0.30 mm and -0.20 mm, respectively. In the lower dentition on the labial/buccal side, the CCH of the first premolars, second premolars and first molars were increased significantly, with a median value of 0.39 mm (P < 0.01), 0.43 mm (P < 0.01) and 0.19 mm (P < 0.05), respectively. The second molars exhibited a significant decrease in CCH with a median value of -0.26 mm (P < 0.05). On the lingual side, the CCH of the central incisors, lateral incisors, canines, first premolars, second premolars and first molars were increased significantly (P < 0.01), with a median value of 0.28 mm, 0.22 mm, 0.31 mm, 0.37 mm, 0.26 mm and 0.28 mm, respectively. CONCLUSION: Significant differences were observed in CCH before and after treatment for many teeth, the average change was less than 0.5 mm. The impact on the long-term health of the periodontal tissue is unknown.

Prevalence of saliva immunoglobulin A antibodies reactive with severe acute respiratory syndrome coronavirus 2 among Japanese people unexposed to the virus.

While the COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses a threat to public health as the number of cases and COVID-19-related deaths are increasing worldwide, the incidence of the virus infection is extremely low in Japan compared with many other countries. To explain this uncommon phenomenon, we investigated the prevalence of naturally occurring ("natural") antibodies, focusing on those of the secretory immunoglobulin A (sIgA) form, reactive with SARS-CoV-2 among Japanese people. One hundred and eighty healthy Japanese volunteers of a wide range of age who had been considered to be unexposed to SARS-CoV-2 participated in this study. Saliva samples and blood samples were collected from all of the 180 participants and 139 adults (aged ≥ 20 years) included therein, respectively. The determination of saliva IgA antibodies, mostly comprising sIgA antibodies, as well as serum IgA and immunoglobulin G antibodies, reactive with the receptor binding domain of the SARS-CoV-2 spike-1 subunit proteins was conducted using an enzyme-linked immunosorbent assay. The major findings were that 52.78% (95% confidence interval, 45.21%-60.25%) of the individuals who had not been exposed to SARS-CoV-2 were positive for saliva IgA antibodies with a wide range of levels between 0.002 and 3.272 ng/mL, and that there may be a negative trend in positivity for the antibodies according to age. As we had expected, a frequent occurrence of assumable "natural" sIgA antibodies reactive with SARS-CoV-2 among the studied Japanese participant population was observed.

Salivary lactoferrin is transferred into the brain via the sublingual route.

Lactoferrin (LF) is produced by exocrine glands including salivary gland, and has various functions including infection defense. However, the transfer of LF from peripheral organs into the brain remains unclear. To clarify the kinetics of salivary LF (sLF), we investigated the consequences of sialoadenectomy and bovine LF (bLF) sublingual administration in rats. The salivary glands were removed from male Wistar rats, and we measured rat LF levels in the blood and brain at 1 week post-surgery. We also examined the transfer of LF into the organs of the rats after sublingual administration of bLF. Rat LF levels in the blood and brain were significantly reduced by sialoadenectomy. Sublingual bLF administration significantly increased bLF levels in the brain, which then decreased over time. These results indicate that LF is transferred from the sublingual mucosa to the brain, in which favorable effects of sLF on brain will be expected via the sublingual mucosa.

Association between saliva PSA and serum PSA in conditions with prostate adenocarcinoma.

In recent years, saliva samples have attracted attention as specimens, which may be used for cancer diagnosis. Prostate-specific antigen (PSA) is the most useful tumor marker for prostate adenocarcinoma (PA). We examined whether there is an association between saliva PSA and serum PSA in patients with PA using enzyme-linked immunosorbent assay. Human subjects were classified into two groups: a low-serum PSA concentration group (n = 20) (<2.5 ng/mL) and a high-serum PSA concentration group with high risk of recurrence or metastasis (n = 11) (≤2.5 ng/mL). There were significant differences in saliva PSA concentration between these groups (p < 0.05). Saliva PSA concentration correlated very well with serum PSA concentration in the high-serum PSA concentration group (γ = 0.910, p < 0.001) using Spearman's rank test, but no correlation in the low-serum PSA concentration group. This result suggests that saliva PSA is associated with blood PSA in patients with recurrent or metastatic PA and may, therefore, be a useful PA biomarker.

Salivary glands as the source of plasma brain-derived neurotrophic factor in stressed rats engaged in biting behavior.

Brain-derived neurotrophic factor (BDNF) is crucial for the survival and differentiation of the central and peripheral nervous systems. Recently, BDNF has been reported to exert broader biological activity on non-neural cells. A previous study examined the effect of immobilization stress on BDNF and its receptor tyrosine receptor kinase B in male rat submandibular glands. In the present study, we found that the rat submandibular gland is the major source of plasma BDNF during acute immobilization stress. Biting modulates the mRNA and protein levels of BDNF in the rat hippocampus, so we also investigated whether the plasma BDNF concentration is influenced by biting. Two hours of acute immobilization stress significantly increased the amount of BDNF mRNA within the rat submandibular glands. Moreover, allowing biting behavior for the second half of the 2-h stress exposure significantly increased the amount of salivary gland BDNF mRNA relative to stress alone. Similar results were found with plasma BDNF concentrations under the same conditions. We confirmed that biting during stress attenuates the increases in plasma adrenocorticotropic hormone and corticosterone concentrations, but this was not dependent on the submandibular glands. Increased BDNF, mRNA and protein expressions were observed in salivary duct cells as a result of immobilization stress and biting behavior, as demonstrated by real-time polymerase chain reaction, immunohistochemistry, western blotting, and enzyme-linked immunosorbent assay. Taken together, the findings indicate that the submandibular glands evidently contribute to the increase in plasma BDNF upon biting.

Expression and Role of the BDNF Receptor-TrkB in Rat Adrenal Gland under Acute Immobilization Stress.

We reported that plasma brain-derived neurotrophic factor (BDNF) was maximally elevated following a 60-min period of acute immobilization stress and that salivary glands were the main source of plasma BDNF under this stress condition. However, the expression pattern of the BDNF receptor, Tyrosine receptor kinase B (TrkB), under this condition has yet to be determined. We therefore investigated the effect of this stress on the expression level of TrkB in various rat organs using real-time PCR. No significant differences were found between controls and 60 min-stressed rats with respect to TrkB level in various organs. Only adrenal glands showed significantly increased TrkB mRNA levels after 60 min of stress. TrkB mRNA and protein were observed to localize in chromaffin cells. In addition, we investigated whether BDNF-TrkB interaction influences the release of stress hormones from PC12 cells, derived from chromaffin cells. Truncated receptor, TrkB-T1, was identified in PC12 cells using RT-PCR. Exposure of PC12 cells to BDNF induced the release of catecholamine. This BDNF-evoked release was totally blocked by administration of the K252a in which an inhibitor of Trk receptors. Thus, BDNF-TrkB interactions may modulate catecholamine release from adrenal chromaffin cells under acute stress conditions.

Chronic stress affects the expression of brain-derived neurotrophic factor in rat salivary glands.

Plasma brain-derived neurotrophic factor (BDNF) levels are associated with several neural disorders. Previously, we reported that BDNF is produced from salivary glands under acute immobilization stress. Additionally, salivary glands are the origin of plasma BDNF during stress; however, the association between the expression of BDNF by the salivary glands under chronic stress conditions is not known. In the present study, we investigated whether plasma BDNF levels in chronic stress depend on the salivary glands. Expression of BDNF mRNA and protein were identified in the submandibular glands when male rats were exposed to chronic restraint stress (12 h daily for 22 days). Chronic stress significantly increased plasma BDNF concentration, as well as adrenocorticotropic hormone and corticosterone levels, but was not altered under chronic stress in bilaterally sialoadenectomized rats. Since chronic stress increases plasma BDNF levels in the sialoadenectomized rat model, the plasma BDNF level was not dependent on BDNF from the salivary glands. Although the salivary glands were the source of plasma BDNF in acute stress conditions in our previous study, it seems that that the increased BDNF expression in the salivary glands in chronic stress does not contribute importantly to the increased circulating BDNF level. The increased plasma BDNF levels may play important roles in homeostasis under stress conditions.

Bruxism affects stress responses in stressed rats.

It has been proposed that suppression of stress-related emotional responses leads to the simultaneous activation of both sympathetic and parasympathetic divisions of the autonomic nervous system (ANS) and that the expression of these emotional states has a protective effect against ulcerogenesis. In the present study, we investigated whether stress-induced bruxism activity (SBA) has a physiological effect of on the stress-induced changes of the stomach, thymus, and spleen as well as blood leukocytes, cortisol, and adrenaline. This study demonstrated that SBA attenuated the stress-induced ulcer genesis as well as degenerative changes of thymus and spleen. SBA also attenuated increases of adrenaline, cortisol, and neutrophils in the blood. In conclusion, expression of aggression through SBA during stress exposure attenuates both stress-induced ANS response, including gastric ulcer formation.