Diabetes Mellitus May Increase Bone Loss After Occlusal Trauma and Experimental Periodontitis

Inflammation alters the expression and activity of the mechanosensitive ion channels in periodontal ligament cells

BACKGROUND

Periodontal ligament cells (PDLCs) possess mechanotransduction capability, vital in orthodontic tooth movement (OTM) and maintaining periodontal homeostasis. The study aims to elucidate the expression profiles of mechanosensitive ion channel (MIC) families in PDLCs and how the inflammatory mediator alters their expression and function, advancing the understanding of the biological process of OTM.

METHODS AND METHODS

Human PDLCs were cultured and exposed to TNF-α. RNA sequencing was conducted to explore the mRNA transcriptome of both normal and TNF-α-treated PDLCs. Differentially expressed MICs were identified and analyzed. The functional expressions of TRPA1 and TRPM8 were further validated by RT-qPCR, Western blot, and calcium influx assays.

RESULTS

All 10 identified MIC families or subfamilies were expressed in PDLCs, with the TRP family being the most abundant. KCNK2, PIEZO1, TMEM87A, and PKD2 were the most expressed ion channels in PDLCs. TNF-α altered the expression of the MIC families, resulting in increased expression of PIEZO, K2P, TRP, TMEM63, and TMEM87 families and decreased expression of ENaC/ASIC, TMC/TMHS/TMIE, TMEM150, TMEM120, and L/T/N-Type calcium channel families. Furthermore, 17 DEMICs were identified (false discovery rate < 0.05), with the top five (fold change ≥ 2), including upregulated TRPA1 and TRPM8. The functional expressions of TRPA1 and TRPM8 were verified, suggesting that TNF-α significantly increased their expression and sensitized their activities.

CONCLUSIONS

The study provides comprehensive expression profiles of the MICs in PDLCs and reveals how inflammation alters the expression and activities of the MICs. Treatments targeting these MICs may offer promising strategies for improving OTM and preventing complications in inflammatory environments, ultimately leading to more effective and safer orthodontic practices.

Distribution and influencing factors on residual pockets of the teeth in patients with periodontitis following non-surgical periodontal treatment: a retrospective observational study

BACKGROUND

Periodontitis is a chronic and multi-factorial infectious disease. A notable difference exists in the prognosis of patients with severe periodontitis after non-surgical periodontal treatment. Thus, a retrospective study was conducted to identify common and specific factors that impact the prognosis of patients with periodontitis stage III-IV following non-surgical periodontal treatment at different tooth sites.

METHODS

A total of 977 teeth were included in the study, comprising 266 patients diagnosed with periodontitis stage III-IV. This sample included 330 anterior teeth, 362 maxillary posterior teeth, and 285 mandibular posterior teeth. Following treatment, the teeth were categorized into two groups based on residual pocket depth [probing depth (PD) ≥ 5 mm] at 3 months post-treatment. The prognosis of periodontitis stage III-IV was assessed through multivariate analysis employing logistic regression to determine the association of various risk factors.

RESULTS

The PD values of each site and the deepest PD values of each tooth significantly decreased at 3 months post-treatment. Residual pockets were predominantly found in the mesio/disto-buccal and mesio/disto-lingual regions. Multivariate analysis revealed that gender, PD, sulcus bleeding index (SBI) and plaque index (PLI) at baseline, and crown-root ratio in anterior teeth had a significant influence on periodontitis stage III-IV (P < 0.05). Smoking, PD, PLI and furcation involvement (FI) at baseline, PLI at 3 months post-treatment, grades of periodontitis, and crown-root ratio were prediction factors for maxillary posterior teeth. Factors such as PD, PLI and FI at baseline, PLI at 3 months post-treatment, and crown-root were significant in mandibular posterior teeth.

CONCLUSIONS

The outcome of non-surgical treatment varies depending on the tooth positions for patients with periodontitis stage III-IV. Dentists must accurately identify the affected teeth that have periodontal pockets of more than 5 mm, taking into consideration the positions of the affected teeth, as well as various local and systemic factors. This comprehensive assessment will enable dentists to develop a customized and effective treatment plan.

Occlusion Heightened by Metal Crown Cementation is Aggressive for Periodontal Tissues

PURPOSE

To investigate the effect of experimental traumatic occlusion (ETO) induced by metal crowns on alveolar bone loss.

MATERIALS AND METHODS

Metal crowns were custom-made for the lower first molars with occlusal discrepancy of 0.4 and 0.7 mm from the maximum intercuspation. Thirty-six animals were randomly divided into three groups (n = 12 animals per group): 0.4-mm hyperocclusion group, 0.7-mm hyperocclusion group and the sham group (no metal crown). Twenty-eight days after crown cementation, the animals were euthanized and gingival tissue was collected to assess cytokine levels of IL-17, IL-6, and TNF-α using enzyme-linked immunosorbent assay (ELISA). Mandibles were stained with 1% methylene blue and alveolar bone levels were quantified. Western blotting was used to quantify the expression of receptor activator of nuclear factor κ B (RANK), and its ligand (RANKL), secreted osteoclastogenic factor of activated T cells (SOFAT) and TNF-α-converting enzyme (TACE). Also, mandibles were histologically processed and stained with hematoxylin and eosin, from which the presence of osteoclast-like cells, multinucleated cells containing ≥3 nuclei was counted at 100× magnification. The data were analyzed using one-way ANOVA and Tukey tests.

RESULTS

Experimental occlusal trauma for 28 consecutive days significantly increased alveolar bone loss and multinucleated cell counts (p < 0.05). RANK, RANKL, SOFAT, TACE, IL-6, and TNF-α were significantly higher in gingival tissues of ETO groups (p < 0.05). IL-17 titers were unchanged among the groups (p > 0.05).

CONCLUSION

Experimental traumatic occlusion activates and sustains bone resorption pathways in the periodontium inducing alveolar bone resorption. As the intensity of occlusal trauma increased, alternative osteoclastic pathways were activated, such as TACE and SOFAT.

Cystathionine gamma-lyase aggravates periodontal damage in traumatic occlusion mouse models

BACKGROUND AND OBJECTIVE

Though impacts of traumatic occlusion (TO) on periodontal tissues and roles of cystathionine γ-lyase (Cth) gene in the regulation of bone homeostasis have been studied by many, no consensus has been reached so far on whether TO deteriorates the periodontium and precise roles of Cth in occlusal trauma. Therefore, this study aims to investigate the impacts of TO on periodontal tissues and the involvement of Cth gene.

METHODS

Eighty C57BL/6 wild-type (WT) mice and Cth knockout (Cth^-/- ) mice, 8 weeks old, were used in this study. The TO model was established using composite resin bonding on the left maxillary molar for one, two, and three weeks, respectively. Morphological and histological changes in the periodontium were assessed by micro-computed tomography (micro-CT), hematoxylin and eosin (H&E) staining, and tartrate-resistant acid phosphatase (TRAP) staining. Osteoclast-related genes were analyzed by real-time polymerase chain reaction (qPCR).

RESULTS

It was found that decreased alveolar bone height, expanded bone resorption area, and increased width of periodontal ligament (PDL) occurred in TO models, accompanied by an increased number of osteoclasts in a time-dependent manner by micro-CT and histological staining. Osteoclast-related genes including Ctsk, Mmp9, Rank, Trap, and Rankl/Opg were also up-regulated after one week of modeling. The up-regulated expressions of Cth gene and its protein CTH were observed in TO mouse models. After 1, 2, or 3 weeks of modeling, WT mice showed more severe alveolar bone resorption, wider PDL, higher osteoclast count, and higher levels of osteoclast-related genes Ctsk, Rank, and Rankl/Opg than Cth^-/- mice.

CONCLUSION

TO causes a reduction in alveolar bone height and PDL morphological disorder with their severity increases in a time-dependent manner. Cth aggravates periodontal damage caused by TO.

Effects of local administration of tiludronic acid on experimental periodontitis in diabetic rats

BACKGROUND

Tiludronic acid (TIL) presents antiresorptive and anti-inflammatory properties and has not been evaluated in the periodontitis-diabetes mellitus (DM) association to date, to the best knowledge of the authors. This study evaluates effects of local administration of TIL on experimental periodontitis (EP) in rats with streptozotocin-induced DM.

METHODS

Thirty-two animals (Rattus norvegicus albinus, Wistar) were divided into groups DM/C (Control), DM/EP, DM/EP/TIL1, and DM/EP/TIL3. In EP groups, a ligature was placed around mandibular first molars. In groups DM/EP/TIL1 and DM/EP/TIL3, TIL solutions (1 and 3 mg/kg, respectively) were injected into the gingival tissue of mandibular molars every other day for 10 days, until euthanasia. Periodontal tissues were analyzed by microcomputed tomography (micro-CT), histomorphometry, immunohistochemistry (tartrate-resistant acid phosphatase [TRAP], receptor activator of nuclear factor-κB ligand [RANKL], osteoprotegerin, cleaved caspase 3), and quantitative reverse transcription-polymerase chain reaction (interleukin [IL]-1β, vascular endothelial growth factor [VEGF]).

RESULTS

In micro-CT analyses, groups DM/EP/TIL1 and DM/EP/TIL3 presented reduced alveolar bone resorption (P < 0.05). Group DM/EP/TIL3 presented decreased attachment loss (P < 0.05). The amount of TRAP-positive multinucleated cells was decreased in TIL groups (P < 0.05). Group DM/EP/TIL3 presented a lower immunolabeling pattern for RANKL (P < 0.05). TIL treatment decreased genic expression of IL-1β, and in group DM/EP/TIL3, expression of VEGF was increased (P < 0.05).

CONCLUSION

Local administration of TIL promoted a protective effect against tissue destruction in EP in diabetic rats, and the dosage of 3 mg/kg of TIL promoted the best results regarding its antiresorptive and anti-inflammatory effects.

Occlusal trauma inhibits osteoblast differentiation and bone formation through IKK-NF-κB signaling

BACKGROUND

Occlusal trauma is an important factor promoting bone loss caused by periodontal diseases. Although there are reports of traumatic force promoting bone resorption in periodontal diseases, no studies examining the inhibition of bone formation by traumatic force and the underlying mechanism have been reported. The aim of this study was to investigate the mechanism whereby traumatic force inhibits bone formation.

METHODS

MC3T3-E1 cells were induced to undergo osteogenic differentiation and subjected to cyclic uniaxial compressive stress with or without stimulation with Pg. LPS. The expression of osteoblast markers and the activation of IKK-NF-κB signaling were evaluated in vitro. Then, MC3T3-E1 cells were induced to undergo osteogenic differentiation and subjected to cyclic uniaxial compressive stress with or without IKK-2 Inhibitor VI. The expression of osteoblast markers was determined. Then, the classic Wnt signaling pathway (β-catenin, Gsk3β, p-Gsk3β, and Dkk1) was further evaluated in vitro. Finally, occlusal trauma was induced in Wistar rats with or without the injection of IKK-2 Inhibitor VI, to evaluate changes in bone mass and IKK-NF-κB and Wnt/β-catenin signaling in vivo.

RESULTS

After stimulation with Pg. LPS and traumatic force, IKK-NF-κB signaling was significantly activated in vitro. The expression of osteoblast markers and the activity of alkaline phosphatase in MC3T3-E1 cells declined after traumatic force loading and were rescued when IKK-NF-κB signaling was blocked. Wnt/β-catenin signaling was accordingly inhibited upon force loading, but this inhibition was reversed when IKK-NF-κB was antagonized in vitro. X-ray and Micro-CT analysis of the mandibles of the rats as well as HE and TRAP staining showed that bone loss induced by occlusal trauma declined after IKK-NF-κB was inhibited. The expression of p65 and IκBα was increased when occlusal trauma was induced in Wistar rats, whereas β-catenin, OCN, and Runx2 levels were decreased. After blocking IKK-NF-κB, significant upregulation of β-catenin, OCN, and Runx2 was observed in rats suffering from occlusal trauma.

CONCLUSIONS

IKK-NF-κB signaling could be activated by traumatic force or occlusal trauma. Its activation promoted the degradation of β-catenin, ultimately inhibiting osteogenic differentiation in vitro and bone formation in vivo.

Synergistic alveolar bone resorption by diabetic advanced glycation end products and mechanical forces

BACKGROUND

The association between diabetes mellitus (DM) and bone diseases is acknowledged. However, the mechanistic pathways leading to the alveolar bone (AB) destruction remain unclear. This study aims to elucidate the mechanical forces (MF)-induced AB destruction in DM and its underlying mechanism.

METHODS

In vivo periodontal tissue responses to MF were evaluated in rats with diabetes. In vitro human periodontal ligament (PDL) cells were either treated with advanced glycation end products (AGEs) alone or with AGEs and MF.

RESULTS

In vivo, the transcription of VEGF-A, colony stimulating factor-1 (CSF-1), and Ager was upregulated in diabetes, whereas changes in DDOST and Glo1 mRNAs were negligible. DM induced VEGF-A protein in the vascular cells of the PDL and subsequent angiogenesis, but DM itself did not induce osteoclastogenesis. MF-induced AB resorption was augmented in DM, and such augmentation was morphologically substantiated by the occasional undermining resorption as well as the frontal resorption of the AB by osteoclasts. The mRNA levels of CSF-1 and vascular endothelial growth factor (VEGF) during MF application were highly elevated in diabetes, compared with those of the normal counterparts. In vitro, AGEs treatment elevated Glut-1 and CSF-1 mRNA levels via the p38 and JNK pathways, whereas OGT and VEGF levels remained unchanged. Compressive MF especially caused upregulation of VEGF, CSF-1, and Glut-1 levels, and such upregulation was further enhanced by AGEs treatment.

CONCLUSIONS

Overloaded MF and AGEs metabolites may synergistically aggravate AB destruction by upregulating CSF-1 and VEGF. Therefore, regulating the compressive overloading of teeth, as well as the levels of diabetic AGEs, may prove to be an effective therapeutic modality for managing DM-induced AB destruction.

Resveratrol suppresses the alveolar bone resorption induced by artificial trauma from occlusion in mice

OBJECTIVE

Besides inflammatory bone loss, trauma from occlusion (TO)-induced alveolar bone loss increases the risk of future tooth loss. We have shown that resveratrol, a polyphenol, possesses anti-inflammatory characteristics and a suppressive effect on osteoclastogenesis. Therefore, we investigated the effects of resveratrol on TO-induced bone loss in mice.

MATERIAL AND METHODS

Trauma from occlusion was induced by overlaying composite resin onto the maxillary first molar of C57BL/6 mice. TO-induced mice were administered either resveratrol or vehicle for 15 days from 5 days before TO induction. The mice administered vehicle only served as controls. The effect of resveratrol on bone resorption was assessed histologically. Gene expression in gingival and periodontal ligament tissues was analyzed. In vitro effect of resveratrol on the differentiation of RAW 264.7 cells and bone marrow-derived macrophages into osteoclastic cells was analyzed.

RESULTS

Resveratrol administration significantly decreased the bone loss and suppressed the elevated expression of osteoclastogenesis-related gene in periodontal ligament tissue by TO. Resveratrol treatment also suppressed the differentiation of both RAW 264.7 cells and bone marrow-derived macrophages into osteoclastic cells.

CONCLUSION

Resveratrol administration suppressed the TO-induced alveolar bone loss by suppressing osteoclast differentiation, suggesting that resveratrol is effective in preventing both inflammation and mechanical stress-induced alveolar bone resorption.

Programmed cell death in periodontitis: recent advances and future perspectives

Periodontitis is a highly prevalent infectious disease, characterized by destruction of the periodontium, and is the main cause of tooth loss. Periodontitis is initiated by periodontal pathogens, while other risk factors including smoking, stress, and systemic diseases aggravate its progression. Periodontitis affects many people worldwide, but the molecular mechanisms by which pathogens and risk factors destroy the periodontium are unclear. Programmed cell death (PCD), different from necrosis, is an active cell death mediated by a cascade of gene expression events and can be mainly classified into apoptosis, autophagy, necroptosis, and pyroptosis. Although PCD is involved in many inflammatory diseases, its correlation with periodontitis is unclear. After reviewing the relevant published articles, we found that apoptosis has indeed been reported to play a role in periodontitis. However, the role of autophagy in periodontitis needs further verification. Additionally, implication of necroptosis or pyroptosis in periodontitis remains unknown. Therefore, we recommend future studies, which will unravel the pivotal role of PCD in periodontitis, allowing us to prevent, diagnose, and treat the disease, as well as predict its outcomes.

Evaluation of bone loss due to primary occlusal trauma in two experimental models of occlusal overload

Abstract Introduction Primary occlusal trauma (OT) is an injury of the periodontium with normal height as a result of occlusal forces which exceed their adaptive capacity. Objective To evaluate, histometrically, the alveolar bone loss in the furcation region of rats experimentally submitted to 2 models of occlusal overload. Material and method 45 animals randomly divided into 3 groups: Occlusal Interference (OI, n = 15) - fixing an orthodontic wire segment on the occlusal surface of the first lower molar; Occlusal Overload (OO, n = 15) - wearing of the cusps of the lower contralateral molars, the second and third molars next to the first molar that had its dimensions maintained; Negative Control (NC, n = 15) - evaluation of the initial dimensions of the periodontal ligament (PL). Five animals / group were sacrificed after 14, 21 and 28 days. Result Intergroup evaluation showed significant bone loss in OI (p<0.001) and OO (p<0.01) compared to NC. OI had significantly higher bone loss compared to OO at 14 (p<0.01), 21 (p <0.01) and 28 days (p<0.01). The intragroup evaluation showed no significant influence of time on bone loss in OI and OO, regardless of the technique used (p>0.05). The thickness of the PL remained stable in NC (p>0.05). Conclusion OI and OO were effective in the experimental reproduction of OT, and OI promoted greater alveolar bone loss compared to OO, showing that the impact of occlusal overload in OI increased the extent of the OT injury.

Do Mobility and Occlusal Trauma Impact Periodontal Longevity?

The impact of tooth mobility and occlusal trauma (OT) on periodontal bone loss and need for therapy has been debated for many years. This paper summarizes the relevant literature reported in three Dental Clinics of North America articles in the late 1990s, and adds newer information from the 2000s. Principle findings indicate that strong evidence of mobility and OT impacting tooth longevity is lacking, but reducing inflammation in the surrounding periodontium remains a critical treatment. Occlusal therapy when mobility is increasing, comfort or function are compromised, or periodontal regeneration procedures are planned should be considered.

Periodontal Inflammatory Conditions Among Smokers and Never-Smokers With and Without Type 2 Diabetes Mellitus

BACKGROUND

There is a dearth of studies regarding the influence of cigarette smoking on periodontal inflammatory conditions among patients with type 2 diabetes mellitus (T2DM). The aim of the present study is to assess periodontal inflammatory conditions among smokers and never-smokers with and without T2DM.

METHODS

One hundred individuals (50 patients with T2DM [25 smokers and 25 never-smokers] and 50 controls [25 smokers and 25 never-smokers]) were included. Information regarding age, sex, duration and daily frequency of smoking, duration and treatment of diabetes, and oral hygiene was recorded using a questionnaire. Periodontal parameters (plaque index [PI], bleeding on probing [BOP], probing depth [PD], clinical attachment loss [AL], and marginal bone loss [MBL]) were measured. Hemoglobin A1c (HbA1c) levels were also recorded.

RESULTS

Mean age, monthly income status, and education levels were comparable among smokers and never-smokers with and without T2DM. Mean HbA1c levels were significantly higher among patients with T2DM (8.2% ± 0.1%) compared with controls (4.4% ± 0.3%) (P <0.05). Smokers in the control group were smoking significantly greater numbers of cigarettes (15.5 ± 2.5 cigarettes daily) compared with smokers with T2DM (6.2 ± 2.1 cigarettes daily) (P <0.05). Periodontal parameters were comparable among smokers and never-smokers with T2DM. Among controls, periodontal parameters (PI [P <0.05], AL [P <0.05], PD ≥4 mm [P <0.05], and MBL [P <0.05]) were significantly higher in smokers than never-smokers. Never-smokers with T2DM had worse periodontal status than smokers and never-smokers in the control group (P <0.05).

CONCLUSIONS

Periodontal inflammatory conditions are comparable among smokers and never-smokers with T2DM. Among controls, periodontal inflammation is worse among smokers than never-smokers.

Fibroblast growth factor-2 promotes healing of surgically created periodontal defects in rats with early, streptozotocin-induced diabetes via increasing cell proliferation and regulating angiogenesis

AIM

To evaluate the effects of fibroblast growth factor (FGF)-2 on the healing of surgical periodontal defects in rats with early, streptozotocin-induced diabetes.

MATERIALS AND METHODS

Fifty Wistar rats were assigned to streptozotocin-induced diabetes or non-diabetes group. Periodontal defects were surgically created at maxillary first molars. Defects were treated with hydroxypropyl cellulose (HPC) or FGF-2 with HPC. Defect fill was evaluated by microcomputed tomography. Histological and immunohistochemical analyses were performed.

RESULTS

Compared to vehicle alone, FGF-2 treatment yielded significantly greater bone volume and trabecular thickness in diabetes group. Diabetes group displayed reduced new bone formation and significantly longer epithelial down-growth compared to non-diabetes group. In diabetes group, FGF-2 treatment increased PCNA-positive cells and new bone formation after 2 weeks and suppressed epithelial down-growth, but new cementum formation was minimal even after 4 weeks. In diabetes group, overexpression of vascular endothelial growth factor was evident in cells within connective tissue, and no significant enhancement was observed by FGF-2 treatment. FGF-2 increased the expression of α-smooth muscle actin in diabetes group.

CONCLUSIONS

Treatment of surgical periodontal defects in diabetic rats with the single application of FGF-2 provided beneficial effects primarily on new bone formation via increasing cell proliferation and regulating angiogenesis.