Effects of metformin on the prevention of bisphosphonate-related osteonecrosis of the jaw-like lesions in rats.

PURPOSE: In this study, we aimed to investigate the effect of glucose metabolism on bone healing after tooth extraction in an osteoporosis rat model administered zoledronic acid (ZA) and dexamethasone (DX). METHODS: In total, 24 male Wistar rats (4 weeks old) were randomly assigned to four groups: Control (subcutaneous physiological saline), ZD (subcutaneous ZA and DX twice a week), Ins+ZD (subcutaneous insulin followed by ZD treatment), and Met+ZD (oral metformin followed by ZD treatment). Blood was collected every two weeks . Two weeks after treatment initiation, the first molar tooth on the right maxilla was extracted from all rats. Four weeks later, the rats were sacrificed, and bone healing was assessed. Maxillae samples were fixed and scanned using micro-computed tomography for quantifying areas of bone defects. Hematoxylin-eosin and tartrate-resistant acid phosphatase (TRAP) staining were performed to evaluate bone apoptosis and osteoclast number. RESULTS: In all experimental groups, body weight was statistically lower than that in the Control group, with no changes observed in uncarboxylated osteocalcin concentrations. The radiological analysis revealed that insulin or metformin administration improved healing in the tooth extraction socket (p < 0.01). Histological examination revealed that the osteonecrosis area was reduced in the Ins+ZD and Met+ZD groups (p < 0.01). TRAP staining presented increased osteoclast numbers in the ZD group when compared with that observed in the Control. CONCLUSIONS: Tooth extraction with long-term ZA and DX administration inhibited bone remodeling and induced bisphosphonate-related osteonecrosis of the jaw-like lesions. Metformin exerted protective effects ag ainst osteonecrosis of the jaw.

Effect of aging on bone metabolism: the involvement of complement C1q.

Purpose Impairment of normal bone remodeling affects the successful osseointegration of dental implants. Recently, it has been reported that complement C1q level increases with age and delays wound healing by modulating Wnt signaling. As Wnt signaling is known to play an essential role in bone remodeling, we hypothesized that aging-dependent increases in C1q affect bone remodeling. In this study, we examined whether C1q affects the differentiation of bone-forming osteoblasts and bone-resorbing osteoclasts, and investigated whether C1q could modify cellular signaling, including the Wnt/ß-catenin pathway in these cells.Methods Osteogenic differentiation of MC3T3-E1 cells was assessed using alkaline phosphatase staining. Differentiation of osteoclasts from mouse bone marrow cells was assessed using tartrate-resistant acid phosphatase staining. Activation of canonical Wnt signaling and protein phosphorylation was monitored using Western blotting.Results C1q, at 5-15 µg/mL promoted osteoclast fusion, whereas it did not affect the differentiation of osteoblasts. On the other hand, a higher concentration of C1q (50 µg/mL) suppressed both bone morphogenetic protein-2-induced osteogenic differentiation and osteoclast formation. C1q did not induce an obvious activation of Wnt/ ß-catenin signaling in either pre-osteoblasts or pre-osteoclasts, contrary to previous reports using other tissues. Instead, C1q upregulated the receptor activator of nuclear factor-kappa B ligand (RANKL)-induced phosphorylation of Akt.Conclusions C1q could affect cellular signaling and modify the differentiation of osteoblasts and osteoclasts, depending on the concentration. Therefore, an increase in C1q with age could be one of the factors that determine the prognosis of treatment of elderly patients.

The effects of hyperglycaemia on peri-implant tissues after osseointegration.

PURPOSE: We assessed the effects of hyperglycaemia induced by streptozotocin (STZ) on peri-implantitis developing after implant osseointegration. METHODS: Thirty-six male Wistar rats (4 weeks old) were used. We placed titanium implants 4 weeks after extraction of the maxillary first molars. Healing abutments were attached 4 weeks later. After osseointegration was confirmed, the rats were divided into control, hyperglycaemia (STZ), and STZ with insulin (STZ+INS) groups. Hyperglycaemia was induced by a single injection of 50mg/kg STZ. Silk ligatures were placed on only the right sides (i.e. ligature sides), not on the left sides. Peri-implant tissues extracted at 4 weeks post-ligation were analysed both radiologically (via micro-computed tomography) and histologically (via toluidine blue staining). Total RNA was also extracted and analysed by quantitative PCR to detect TNF-α, IL-1ß and the receptor of advanced glycation end products (RAGE). Additionally, advanced glycation end products (AGEs) were measured by ELISA. RESULTS: Radiological and histological analyses showed that bone loss on the non-ligature sides was significantly greater in the STZ than the control group. However, on the ligature sides, bone loss was greater than on the non-ligature sides, and no significant difference was evident among the three groups. The levels of mRNAs encoding TNF-α, IL-1ß, RAGE, and AGEs on the ligature sides were significantly upregulated (all P<0.05) in the STZ compared to the control group. CONCLUSIONS: Although hyperglycaemia could be associated with bone loss around implants with increased AGE production and RAGE expression, hyperglycaemia does not become a triggering factor of ligature induced peri-implantitis.

Implant-supported fixed prosthesis improves nutrient intake in patients with partial edentulous posterior regions.

PURPOSE: This study investigated changes in food and nutrient intake after implant-supported fixed prosthesis treatment in patients with partial edentulous posterior regions. METHODS: This study included 30 patients who received implant treatment with fixed prostheses in the posterior region. Food and nutrient intake was evaluated using a brief self-administered diet history questionnaire at baseline and post-implant treatment, and the results were statistically analyzed. RESULTS: Treatment with implant-supported fixed prostheses in patients with posterior edentulous conditions tended to increase the amounts of soy products and vegetables consumed: in particular, intake of carrot and squash was significantly increased. The total energy, protein, lipid, and carbohydrate intakes were comparable between baseline and post-implant treatment. On the other hand, the vegetable protein, α-carotene, daidzein, and genistein intakes were significantly increased, and dietary fiber and ß-carotene intakes tended to be increased in patients with implant-supported fixed prostheses. CONCLUSIONS: Implant-supported fixed prostheses in patients with posterior edentulous conditions affected food intake, resulting in improved nutrient intake.

Efficacy of electric-powered cleaning instruments in edentulous patients with implant-supported full-arch fixed prostheses: a crossover design.

BACKGROUND: The aim of this study was to evaluate the plaque removal efficacies of electric toothbrushes and electric dental floss compared with conventional manual toothbrushing in cleaning the fitting surface of an All-on-4™ concept (Nobel Biocare, Zürich-Flughafen, Switzerland) implant-supported fixed dental prosthesis (FDP). METHODS: Nine patients with maxillary edentulous arches participated in the study. We investigated two electric-powered brushes (Sonicare Diamond Clean®, Koninklijke Philips N.V., Amsterdam, the Netherlands [SD group], and the Oral-B Professional Care Smart Series 5000®, Braun GmbH, Kronberg, Germany [OralB group]) and one electric dental floss unit (Air Floss®, Koninklijke Philips N.V. [AF group]). A manual toothbrush (Tuft24® MS, OralCare Inc., Tokyo, Japan) was used by the control group. The fitting surface of the FDP was stained to allow visualization of the entire accumulated plaque area. Both the buccal and palatal portions of the plaque area were assessed before and after brushing to evaluate each instrument's plaque removal rate using a crossover study design. Two-week washout periods were employed between each evaluation. RESULTS: The plaque removal rates were 53.5 ± 8.5%, 70.9 ± 6.5%, 75.4 ± 6.3%, and 74.4 ± 4.2% for the control, AF, OralB, and SD groups, respectively. When participants were divided into two groups based on their plaque removal rates with a manual toothbrush (poor brushing and good brushing), the poor brushing group showed significant improvement in the plaque removal rate when using electric-powered toothbrushes. The plaque removal rates for the buccal area were significantly higher for the OralB and SD groups than for the manual brushing group (control group), with rates of 52.8 ± 7.9%, 70.1 ± 7.3%, 77.7 ± 6.5%, and 79.5 ± 3.7% for the control, AF, OralB, and SD groups, respectively. The plaque removal rates in the palatal area were consistently lower than those in the buccal area for each of the three electric instruments. CONCLUSIONS: The results suggest that patients who are not adept at manual toothbrushing may potentially improve their removal of plaque from the fitting surfaces of FDPs by using electric toothbrushes.

Long-term dexamethasone treatment diminishes store-operated Ca2+ entry in salivary acinar cells.

Corticosteroids are used in the treatment of many diseases; however, they also induce various side effects. Dexamethasone is one of the most potent corticosteroids, and it has been reported to induce the side effect of impaired salivary gland function. This study aimed to evaluate the effects of dexamethasone on mouse submandibular gland function to gain insight into the mechanism of dexamethasone-induced salivary hypofunction. The muscarinic agonist carbachol (CCh) induced salivary secretion and was not affected by short-term dexamethasone treatment but was decreased following long-term dexamethasone administration. The expression levels of the membrane proteins Na+-K+-2Cl- cotransporter, transmembrane member 16A, and aquaporin 5 were comparable between the control and long-term dexamethasone treatment groups. The CCh-induced increase in calcium concentration was significantly lower in the presence of extracellular Ca2+ in the long-term dexamethasone treatment group compared to that in the control group. Furthermore, CCh-induced salivation in the absence of extracellular Ca2+ and Ca2+ ionophore A23187-induced salivation was comparable between the control and long-term dexamethasone treatment groups. Moreover, salivation induced by the Ca2+-ATPase inhibitor thapsigargin was diminished in the long-term dexamethasone treatment group. In summary, these results demonstrate that short-term dexamethasone treatment did not impair salivary gland function, whereas long-term dexamethasone treatment diminished store-operated Ca2+ entry, resulting in hyposalivation in mouse submandibular glands.

The effectiveness of an occlusal disclosure sheet to diagnose sleep bruxism: A pilot study.

OBJECTIVE: To evaluate the utility of vacuum-pressed, BruxChecker® sheets for the diagnosis of sleep bruxism. METHODS: Twenty subjects participated in this study. Tooth contact during sleep was recorded using a 0.1 mm-thick polyvinyl chloride sheet called BruxChecker®. The area of the BruxChecker® in which the red dye was removed was measured. In addition, the EMG activity of the masseter muscle during sleep was recorded. The numbers of bruxism bursts and episodes were counted, and their correlations with the peeled area of the red dye on the BruxChecker® were evaluated. RESULTS: The number of bruxism bursts and episodes/hr significantly correlated with the peeled area at all cut-off values. The peeled area significantly correlated with the number of phasic type bruxism episodes but not with tonic or mixed type bruxism episodes. DISCUSSION: Since the BruxChecker® peeled area reflected phasic type sleep bruxism, the sheets may be useful in sleep bruxism screening.

Ten-year survival of immediate-loading implants in fully edentulous mandibles in the Japanese population: a multilevel analysis.

PURPOSE: To evaluate the long-term clinical results of and risk factors for immediate-loading implant treatment of completely edentulous mandibles. METHODS: We retrospectively studied 220 implants in 52 patients who received immediate-loading implants in fully edentulous mandibles. Kaplan-Meier survival analyses, log-rank tests, and multilevel mixed-effects parametric survival analysis was used for statistical analyses. RESULTS: Thirteen of implants in seven patients failed, and the 10-year cumulative implant survival rate was 93.9 % and significantly (p=0.049) higher in women than in men. None of the predictor variables were significantly associated with implant survival, although sex tended to be associated with implant survival. CONCLUSIONS: Immediate-loading implant treatment for completely edentulous mandibles had acceptable clinical results in the long term. Although we could not identify significant risk factors, we established a multilevel mixed-effects parametric survival analysis with the immediate-loading implant survival data.

Is Anterior Guidance a Key Factor on Planning Implant Treatment for Free-End Missing in the Posterior Mandible?

To perform safe implant treatment, the anatomical structure and bone quality at implant placement sites are evaluated based on a patient's computerized tomography (CT) data, but there is no definite method to determine placement sites and the appropriate number of implants. The objective of this study was to investigate the influence of the number and arrangement of implants on the stress distribution in 3-unit posterior fixed partial dentures for the posterior mandible by mechanical analysis using the finite element method. Three-dimensional finite element analysis models were constructed from the CT data of a patient with missing mandibular teeth (Nos. 35, 36, 37). Implant placement was simulated under various conditions. Superstructures were connected and fixed with a titanium frame. As the loading conditions, 400 N vertical and lateral loads (45° on the lingual side and 45° on the buccal side) were applied to the upper areas of Nos. 35, 36, and 37, and the stress distribution and frame displacement were evaluated. When a vertical force was applied, no difference of the von Mises stress was noted among the 5 experimental conditions. When lateral force was applied from the lingual and buccal sides at 45°, the stress was higher than that induced by vertical force under all conditions, and it was especially high under mesial and distal cantilever conditions. When displacement of the titanium frame was measured, the displacement caused by lateral force was greater than that due to vertical force. In addition, comparison between long and short distal cantilever bridges revealed that displacement of the titanium frame tended to be smaller when the short cantilever was used. These findings suggested that the stress on peri-implant tissues and displacement of the titanium frame vary depending on the configuration and number of implants, with greater stress and more marked displacement of the titanium frame being induced by lateral force when the number of implants is reduced and a cantilever bridge is selected.

The effects of Lactobacillus reuteri probiotics combined with azithromycin on peri-implantitis: A randomized placebo-controlled study.

PURPOSE: The aim of this randomized placebo-controlled clinical study was to investigate the effects of a probiotic tablet containing Lactobacillus reuteri in peri-implantitis patients. METHODS: Subjects comprised 30 patients with mild to moderate peri-implantitis. A baseline clinical examination and microbiological assessment were conducted, followed by an antibiotics treatment (azithromycin, 500mg, once a day for 3 days). Subjects were divided into probiotic and placebo groups. The clinical examination and bacterial sampling were performed 0, 4, 12 and 24 weeks after the intake of probiotics. The clinical examination included probing pocket depth (PPD), bleeding on probing (BOP), the modified plaque index (mPI), and modified bleeding index (mBI). The number of bacteria was assessed using the PCR-invader method. The Wilcoxon rank-sum test and Wilcoxon signed-rank test with Bonferroni corrections were used for data analyses. RESULTS: Although the number of bacteria decreased after the administration of azithromycin in both groups, they increased again thereafter. No significant difference was observed in bacterial numbers between the two groups. Although PPD in the probiotics group was significantly lower at 4 and 24 weeks than at 0 weeks (p<0.05), a significant decrease did not occur in the placebo group. The mBI score at 24 weeks was significantly lower in the probiotics group than in the placebo group (p<0.05). No significant difference was observed in BOP or mPI between the two groups. CONCLUSION: These results suggested that probiotics prevent inflammation by affecting host responses rather than improving microbial flora in peri-implant sulci in peri-implantitis patients.

Salivary gland hypofunction in KK-Ay type 2 diabetic mice.

BACKGROUND: Hypofunction of different organs in the body is associated with diabetes, including in the oral cavity. Diabetes is often associated with xerostomia, but the underlying mechanism is not well characterized. Thus, the mechanisms underlying diabetes-induced xerostomia were investigated in this study in KK-A y mice as an experimental model of type 2 diabetes. METHODS: The mechanisms involved in diabetes-induced xerostomia were investigated using the ex vivo glandular perfusion technique, histological analysis, and immunohistochemical and intracellular signaling analyses. RESULTS: Ex vivo submandibular gland secretions from KK-Ay mice decreased by 30% following stimulation with 0.3 µmol/L carbachol (CCh), a cholinergic agonist. Acinar cell weight was comparable between KK-Ay and control mice, whereas duct cell weight was significantly greater in KK-Ay mice. Concentrations of Na+ and Cl- in the secreted saliva decreased significantly in KK-Ay mice, supporting the finding of increased ductal tissue in KK-Ay mice. Immunohistochemistry revealed no significant differences between KK-Ay and control mice in terms of the expression of Cl- and water channels, Na+ -K+ -2Cl- cotransporters, and membrane proteins critical for fluid secretion. Cellular signaling analysis revealed that the increase in [Ca2+ ]i in response to 0.3 µmol/L CCh was reduced by 30% in KK-Ay mice, although there was no significant difference in the thapsigargin (1.0 µmol/L)-induced increase in store-depleted calcium between KK-Ay and control mice. CONCLUSIONS: These results demonstrate that submandibular fluid secretion is diminished in KK-Ay mice because of a diminished increase in [Ca2+ ]i . Duct cell weight increased in KK-Ay mice, possibly leading to increased ion reabsorption and thus decreased Na+ and Cl- concentrations in the secreted saliva.

The effect of low-intensity pulsed ultrasound on wound healing using scratch assay in epithelial cells.

PURPOSE: Low-intensity pulsed ultrasound (LIPUS) is widely used in medical fields because it shortens the time required for biologic wound healing in fracture treatment. Also, in dental fields, LIPUS should be effectively employed for implant treatment. However, most of the relevant reports have been published on its effects on bone formation around implants, and the effects of LIPUS on soft tissue healing remain unclear. In the present study, we examined the effects of LIPUS on soft tissue healing using gingival epithelial cells. METHODS: Gingival epithelial cells were cultured on a dish, followed by LIPUS exposure at a frequency of 3MHz for 15min. The cells were counted with a hemocytometer, and a scratch assay was conducted by measuring the closing area of the scratch wound using a microscope. Following LIPUS exposure, total RNA was collected for microarray analysis. In addition, real-time PCR was performed to examine the mRNA expression level of integrin α6ß4. Furthermore, total protein was collected to examine the protein expression level of integrin α6ß4 by western blotting. RESULTS: The cell count and scratch assay demonstrated that LIPUS exposure promoted cell proliferation and scratch-wound closure. Microarray analysis demonstrated the increased expression levels of adhesion-related genes, including integrin. Real-time PCR analysis demonstrated that LIPUS exposure significantly up-regulated the mRNA expression level of integrin α6ß4. Western blotting showed intense staining of integrin α6ß4. CONCLUSION: LIPUS exposure promotes wound closure in the scratch assay and up-regulates the expression level of integrin α6ß4 as compared with the control.

Promotion of insulin-induced glucose uptake in C2C12 myotubes by osteocalcin.

A close relationship between the bone and systemic glucose metabolism has recently been the center of attention, since the uncarboxylated form of osteocalcin (GluOC), a bone-derived protein, but not the γ-carboxylated form, is involved in glucose metabolism. However, the analysis of GluOC effect using isolated organs and related cell lines are required to understand its roles in a whole systemic metabolic status. In the present study, we examined the effect of GluOC on cell lines derived from skeletal muscle to explore the mechanisms by which GluOC regulates glucose uptake. In the differentiated C2C12 myotubes, GluOC dose-dependently induced the phosphorylation of ERK without affecting intracellular cAMP and Ca(2+) levels. This effect was inhibited by U0126, an inhibitor of ERK kinase (MEK). Additionally, U73122, an inhibitor of phospholipase C tended to inhibit it as well. Furthermore, cell treatment with GluOC for a long period promoted insulin-induced Akt phosphorylation and glucose uptake in the myotubes, which was abolished by ERK signaling inhibition. These results indicate that GluOC does not triggered Akt phosphorylation and glucose uptake by itself but promotes insulin-induced glucose uptake in myotubes, probably by up-regulating Akt signaling through ERK activation.