AimThe purpose of this study was to investigate the effects of non-surgical periodontal treatment on hemoglobinA1c (HbA1c) levels, oxidative stress balance and quality of life (QOL) in patients with type 2 diabetes mellitus (T2DM) compared to no periodontal treatment (simple oral hygiene instructions only).MethodsThe design was a 6-month, single-masked, single center, randomized clinical trial. Patients had both T2DM and chronic periodontitis. Forty participants were enrolled between April 2014 and March 2016 at the Nephrology, Diabetology and Endocrinology Department of Okayama University Hospital. The periodontal treatment group (n = 20) received non-surgical periodontal therapy, including scaling and root planing plus oral hygiene instructions, and consecutive supportive periodontal therapy at 3 and 6 months. The control group (n = 17) received only oral hygiene instructions without treatment during the experimental period. The primary study outcome was the change in HbA1c levels from baseline to 3 months. Secondary outcomes included changes in oxidative stress balance (Oxidative-INDEX), the Diabetes Therapy-Related QOL and clinical periodontal parameters from baseline to 3 months and baseline to 6 months.ResultsChanges in HbA1c in the periodontal treatment group were not significantly different with those in the control group at 3 and 6 months. Systemic oxidative stress balance and QOL significantly improved in the periodontal treatment group compared to the control group at 3 months. In the subgroup analysis (moderately poor control of diabetes), the decrease in HbA1c levels in the periodontal treatment group was greater than that in the control group at 3 months but not significant.ConclusionsIn T2DM patients, non-surgical periodontal treatment improved systemic oxidative stress balance and QOL, but did not decrease HbA1c levels at 3 months follow-up.Trial registrationCurrent Controlled Trials UMIN-ICDR UMIN 000013278 (Registered April 1, 2014).

Recent studies suggest that the commensal microbiota affects not only host energy metabolism and development of immunity but also bone remodeling by positive regulation of osteoclast activity. However, the mechanism of regulation of bone cells by the commensal microbiota has not been elucidated. In this study, 8-week-old specific pathogen-free (SPF) and germ-free (GF) mice were compared in terms of alveolar bones and primary osteoblasts isolated from calvarias. Micro-CT analysis showed that SPF mice had larger body size associated with lower bone mineral density and bone volume fraction in alveolar bones compared with GF mice. Greater numbers of osteoclasts in alveolar bone and higher serum levels of tartrate-resistant acid phosphatase 5b were observed in SPF mice. Tissue extracts from SPF alveolar bone showed higher levels of cathepsin K, indicating higher osteoclast activity. SPF alveolar extracts also showed elevated levels of γ-carboxylated glutamic acid–osteocalcin as a marker of mature osteoblasts compared with GF mice. Polymerase chain reaction (PCR) array analysis of RNA directly isolated from alveolar bone showed that in SPF mice, expression of mRNA of osteocalcin, which also acts as an inhibitor of bone mineralization, was strongly enhanced compared with GF mice. Cultured calvarial osteoblasts from SPF mice showed reduced mineralization but significantly enhanced expression of mRNAs of osteocalcin, alkaline phosphatase, insulin-like growth factor-I/II, and decreased ratio of osteoprotegerin/receptor activator of nuclear factor-kappa B ligand compared with GF mice. Furthermore, PCR array analyses of transcription factors in cultured calvarial osteoblasts showed strongly upregulated expression of Forkhead box g1. In contrast, Gata-binding protein 3 was strongly downregulated in SPF osteoblasts. These results suggest that the commensal microbiota prevents excessive mineralization possibly by stimulating osteocalcin expression in osteoblasts, and enhances both osteoblast and osteoclast activity by regulating specific transcription factors.

The aim of this study was to investigate whether a Keap1-dependent oxidative stress detector-luciferase (OKD-LUC) mouse model would be useful for the visualization of oxidative stress induced by experimental periodontitis. A ligature was placed around the mandibular first molars for seven days to induce periodontitis. Luciferase activity was measured with an intraperitoneal injection of d-luciferin on days 0, 1, and 7. The luciferase activity in the periodontitis group was significantly greater than that in the control group at seven days. The expressions of heme oxygenase-1 (HO-1) and malondialdehyde in periodontal tissue were significantly higher in the periodontitis group than in the control group. Immunofluorescent analysis confirmed that the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) occurred more frequently in the periodontitis group than in the control group. This study found that under oxidative stress induced by experimental periodontitis, the Nrf2/antioxidant defense pathway was activated and could be visualized from the luciferase activity in the OKD-LUC model. Thus, the OKD-LUC mouse model may be useful for exploring the mechanism underlying the relationship between the Nrf2/antioxidant defense pathway and periodontitis by enabling the visualization of oxidative stress over time.

The purpose of this cross-sectional study was to investigate the association between sleep quality and duration, and periodontal disease among a group of young Japanese university students. First-year students (n = 1934) at Okayama University who voluntarily underwent oral health examinations were included in the analysis. Sleep quality and duration were assessed by the Japanese version of the Pittsburgh Sleep Quality Index. Dentists examined Oral Hygiene Index-Simplified (OHI-S), probing pocket depth (PPD), and percentage of sites with bleeding on probing (BOP). Periodontal disease was defined as presence of PPD ≥ 4 mm and BOP ≥ 30%. Overall, 283 (14.6%) students had periodontal disease. Poor sleep quality was observed among 372 (19.2%) students. Mean (± standard deviation) sleep duration was 7.1 ± 1.1 (hours/night). In the logistic regression analysis, periodontal disease was significantly associated with OHI-S (odds ratio [OR]: 2.30, 95% confident interval [CI]: 1.83–2.90; p < 0.001), but not sleep quality (OR: 1.09, 95% CI: 0.79–1.53; p = 0.577) or sleep duration (OR: 0.98, CI: 0.87–1.10; p = 0.717). In conclusion, sleep quality and duration were not associated with periodontal disease among this group of young Japanese university students.

Bruxism is a parafunctional activity that can seriously affect quality of life. Although bruxism induces many problems in the oral and maxillofacial area, whether it contributes to the onset of malocclusion remains unclear. The purpose of this prospective cohort study was to investigate the association between the onset of malocclusion and awareness of clenching during the daytime in young adults. Among 1,092 Okayama University students who underwent normal occlusion at baseline, we analysed 238 who had undergone a dental examination and had complete data after 3 years (2013–2016). We also performed subgroup analysis to focus on the association between awake bruxism and the onset of crowding (n = 216). Odds ratios (ORs) were calculated using multivariate logistic regression analyses. The incidences of malocclusion and crowding were 53.8% and 44.5%, respectively. In multivariate logistic regression, awareness of clenching was a risk factor for crowding (OR: 3.63; 95% confidence interval [CI]: 1.08–12.17). Moreover, underweight (body mass index < 18.5 kg/m2) was related to the onset of malocclusion (OR: 2.34; 95%CI: 1.11–4.92) and crowding (OR: 2.52, 95%CI: 1.25–5.76). These results suggest that awareness of clenching during the daytime and underweight are risk factors for the onset of crowding in young adults.