Incidence and contributing factors of non-root canal treated teeth with chronic fatigue root fracture: A cross-sectional study.

BACKGROUND/PURPOSE: Chronic fatigue root fracture describes a root fracture in a non-root canal treated (non-RCT) tooth. This study aimed to report the incidence and contributing factors of non-RCT teeth with chronic fatigue root fracture in a Taiwanese population. METHODS: This cross-sectional study included teeth extracted at Taipei Veterans General Hospital in Taiwan between 2018 and 2019. The reasons for extractions were recorded and included vertical and horizontal root fractures (VRF and HRF). Comparisons of clinical factors between teeth with fatigue VRF and teeth with fatigue HRF were performed by chi-square or Fisher exact test, where appropriate. RESULTS: Of the 4207 extracted teeth examined, 263 (6.25%) had tooth fracture. Thirty-two non-RCT teeth had chronic fatigue root fracture, including 16 with VRF and 16 with HRF. The incidence was 0.76% (32/4207). The occurrence of chronic fatigue root fracture was higher in males (83.9%). The mean age of the 31 patients with chronic fatigue root fracture was 71.7 ± 13.1 years. More than half of these teeth had intact crowns with severe attrition. The fatigue VRF occurred more frequently in molars (P = 0.003), in roots with a long oval cross-section (P = 0.037), and in terminal teeth (P = 0.013) than the fatigue HRF. CONCLUSION: The incidence of chronic fatigue root fracture is 0.76%. Both VRF and HRF occur mainly in aged males, in posterior teeth with attrition, and in teeth without restoration. Tooth position, cross-section root morphology, and terminal tooth are contributing factors related to chronic fatigue root fracture.

Occlusal Trauma and Bisphosphonate-Related Osteonecrosis of the Jaw in Mice.

Osteonecrosis of the jaw (ONJ) is a serious adverse event that is associated with antiresorptive agents, and it manifests as bone exposure in the maxillofacial region. Previous clinical reports suggest that mechanical trauma would trigger ONJ in a manner that is similar to tooth extractions. To the best of our knowledge, there have been few detailed pathophysiological investigations of the mechanisms by which occlusal/mechanical trauma influences ONJ. Here, we developed a novel mouse model that exhibits ONJ following experimental hyperocclusion and nitrogen-containing bisphosphonate (N-BP) treatment. This in vivo model exhibited ONJ in alveolar bone, particularly in the mandible. Moreover, the experimental hyperocclusion induced remarkable alveolar bone resorption in both mouse mandible and maxilla, whereas N-BP treatment completely prevented alveolar bone resorption. In this study, we also modeled trauma by exposing clumps of mesenchymal stem cells (MSCs)/extracellular matrix complex to hydrostatic pressure in combination with N-BP. Hydrostatic pressure loading induced lactate dehydrogenase (LDH) release by calcified cell clumps that were differentiated from MSCs; this LDH release was enhanced by N-BP priming. These in vivo and in vitro models may contribute further insights into the effect of excessive mechanical loading on ONJ onset in patients with occlusal trauma.

Wnt4 regulates bone metabolism through IKK-NF-κB and ROCK signaling under occlusal traumatic periodontitis.

BACKGROUND AND OBJECTIVE: Occlusal trauma is one of the most important local contributing factors of periodontitis. It has been reported that Wnt4, a noncanonical Wnt ligand, can inhibit osteoclast formation and inflammation and promote bone formation in vivo. However, the prospects of Wnt4 application in occlusal trauma and periodontitis have not yet been described. This study aimed to investigate the function and the corresponding mechanism of Wnt4 to regulate bone metabolism in occlusal trauma and periodontitis. MATERIAL AND METHODS: Osteogenic-induced MC3T3-E1 cells were treated with or without Porphyromonas gingivalis lipopolysaccharide (Pg. LPS) under cyclic uniaxial compressive stress. After treatment with mouse recombinant protein Wnt4 (rWnt4), the expression of osteogenic markers and activation of the IKK-NF-κB signaling pathway were evaluated in vitro. To investigate whether Wnt4 can promote osteogenesis via the ROCK signaling pathway, the expression of RhoA was evaluated in vitro. Finally, we evaluated the change in bone quantity and the activation of the IKK-NF-κB and ROCK signaling in mice with occlusal trauma and periodontitis to demonstrate the therapeutic efficacy of rWnt4 injection. RESULTS: Stimulation of traumatic force and Pg. LPS stimulation suppressed the expression of osteoblast markers, but their expression was rescued after rWnt4 treatment in vitro. In addition, the inhibition of the ROCK signaling pathway induced by force loading was reversed when rWnt4 was applied in vitro. Micro-CT, H&E, and TRAP staining of the mandibles showed increased bone loss in the occlusal trauma-aggravated periodontitis group, whereas it was rescued after rWnt4 injection. The expression levels of IκBα and p65 were upregulated in occlusal trauma and periodontitis-bearing mice, whereas the expression levels of Runx2 and RhoA were downregulated. After rWnt4 injection, remarkably upregulation of Runx2 and RhoA expression was observed in occlusal trauma and periodontitis- bearing mice. CONCLUSION: Wnt4 not only inhibits IKK-NF-κB signaling but also activates ROCK signaling to inhibit osteoclast formation and promote bone regeneration in occlusal trauma and periodontitis-bearing mice.

Efficacy of tooth splinting and occlusal adjustment in patients with periodontitis exhibiting masticatory dysfunction: A systematic review.

OBJECTIVE: To evaluate the efficacy of tooth splinting (TS) and occlusal adjustment (OA) compared to no TS or OA in patients with periodontitis exhibiting masticatory dysfunction. MATERIAL: The primary outcome criterion was tooth loss (TL), and the secondary outcome parameters were change in probing pocket depth (PPD), change in clinical attachment level (CAL), tooth mobility (TM), and patient-reported outcome measures (PROMs). Literature search was performed on three electronic databases (from 01/1965 to 04/2021) and focused on clinical studies with at least 12 months follow-up. RESULTS: From a total of 1515 publications, 51 articles were identified for full-text reading, of which 2 retrospective case series on TS with low risk of bias and 1 randomized and 2 prospective studies on OA with unclear risk of bias were included. For TS, synthesis of data showed that in 72 patients, 26 out of 311 teeth (weighted mean incidence of TL 8.4%) and 156 out of 1541 teeth with no TS (weighted mean incidence of TL 10.1%) were lost over 2 years following non-surgical periodontal therapy. The randomized controlled clinical trial (RCT) indicated CAL gain for teeth with OA compared to no OA. For the effect of OA on TL, PPD, and TM, heterogeneous data were retrieved from the included studies. CONCLUSIONS: Within the limitations of this review and based on a low level of evidence, it is concluded that TS does not improve survival of mobile teeth in patients with advanced periodontitis. OA on teeth with mobility and/or premature contacts may lead to improved CAL, while the effect of OA on the remaining periodontal parameters remains unclear.

Apical periodontitis after intense bruxism.

BACKGROUND: Bruxism is known to cause masticatory muscle pain, temporomandibular joint pain, headaches, mechanical tooth wear, prosthodontic complications and cracked teeth. Less known to the practitioner, and described only experimentally in literature, is that bruxism can also damage the pulp. To our knowledge, this is the first known clinical case of a patient developing apical periodontitis due to bruxism. CASE PRESENTATION: This article presents the case and successful treatment of a 28-year-old healthy male patient with apical periodontitis on teeth 36 and 46 requiring root canal treatment after an intense phase of bruxism. Due to an unclear diagnosis, treatment had been delayed. CONCLUSIONS: Incomprehensible tooth pain can be the result of bruxism. Practitioners need to be informed that intense bruxism can possibly lead to apical periodontitis. It is important, therefore, that a thorough anamnesis is collected and taken into account during diagnostics.

Correlation between occlusal trauma and oral microbiota: a microbiological investigation.

The occlusal trauma has been defined as an injury to the periodontium resulting from occlusal forces that exceeds the reparative capacity of the attachment apparatus. Currently, the effects of occlusal trauma on tooth support tissues, the onset and the progression of periodontal disease are still debated. In fact, researchers started evaluating the possible effects of occlusal discrepancies on incidence, progression, and treatment outcomes of periodontitis, but all the results underlined the more significant role played by microbiological flora. The results of this study show that after 60 days of treating the occlusal trauma, a significant reduction was achieved in the periodontal bacterial flora.

Expression of substance P, calcitonin gene-related peptide and vascular endothelial growth factor in human dental pulp under different clinical stimuli.

BACKGROUND: The aim of this study was to measure the dental pulp inflammatory response through neuropeptides (SP and CGRP) as a response to occlusal trauma, orthodontic movements and a combination of both, as well as the angiogenic defense mechanism through VEGF expression, which could be the initial step to mineralized tissue formation. METHODS: Forty human dental pulp samples were collected from healthy first premolars with extraction indicated due to orthodontic reasons from a sample of 20 patients. Patients were divided into four groups with 10 premolars each (1 mandibular and 1 maxillary premolar from each patient): healthy pulp control group, occlusal trauma group, moderate orthodontic forces group; and occlusal trauma plus moderate orthodontic forces group. Stimuli were applied for 24 h before tooth extraction in all experimental groups. All samples were processed, and SP, CGRP, and VEGF were measured by radioimmunoassay. The Kruskal-Wallis test was performed to assess significant differences among groups and Mann-Whitney's U post hoc pairwise comparisons were also performed. RESULTS: The highest increase in SP, CGRP, and VEGF expressions was found in the occlusal trauma plus orthodontic forces group, followed by the moderate orthodontic forces, the occlusal trauma and the control groups, with statistically significant differences between all groups for each of the 3 peptides analyzed (Kruskal-Wallis p < 0.001). All possible pairwise post-hoc comparisons were also significant for each peptide analyzed (Mann-Whitney's U p < 0.001). CONCLUSION: SP, CGRP, and VEGF expressions significantly increase in human dental pulps when stimulated by occlusal trauma combined with moderate orthodontic forces, as compared with these two stimuli applied independently. Name of the registry: Importance of Neurogenic Inflammation in the Angiogenic Response of the Dental Pulp as a Defensive Response. TRIAL REGISTRATION NUMBER: NCT03804034. Date of registration: 01/15/2019 Retrospectively registered. URL of trial registry record: https://clinicaltrials.gov/ct2/show/NCT03804034?term=NCT03804034&draw=2&rank=1 .

Incidence of Malocclusion among Young Patients with Gingival Recessions-A Cross-Sectional Observational Pilot Study.

Background and Objectives: Dental occlusion and gingival recession have been studied over the past years especially because of the increasing incidence of occlusal interferences in young patients. The purpose of this pilot study is to investigate any association between occlusal dysfunctions and gingival recessions. Data on gingival phenotype and previous orthodontic treatment were also collected to assess any correlation with the presence of gingival recession. Materials and Methods: Forty systemically healthy subjects, without signs of periodontitis and with gingival recessions, were included in the study. The following parameters were determined: location and extent of the gingival recession, gingival phenotype and functional occlusion by means of observing and registering the occlusal contacts in maximum intercuspation position, protrusive and lateral guidance. Results: Premolars were mostly affected in cases of working-side interferences during lateral guidance (71.19% of the affected teeth during left and 75% during right mandibular movements). The chi-squared exact test applied for the analysis of contingency tables revealed statistically significant associations between excursive interferences during lateral guidance and anterior guidance and the presence of gingival recession on the involved group of teeth. Conclusions: The results suggest that most gingival recessions might be associated with working-side interferences, the highest number of gingival recessions being associated with active interferences during lateral guidance.

OCCLUSAL TRAUMA OF IMPLANT-SUPPORTED METAL-CERAMIC CROWN: A CASE REPORT.

In this article there is a clinical case of occlusion trauma of implant-supported metal-ceramic crown for prosthetics of central incisor. Its uniqueness is the possibility to save dental implant after acute occlusion impact, which was strong enough to break ceramic facing of fixed denture, but not able to destroy bone and implant components. The occlusion force located at the incisal edge of the crown induced a reverse torque to the implant and did not result in its failure or bone resorption. In a year after repeated fixed prosthetics, the results of clinical examination proved absence of any problem with osseointegration. Literature analysis lets us to suggest, that the phenomenon was caused by protective action of cortical bone around of dental implant. Besides, in the case of natural tooth, the bone is suddenly compressed against the conical root; it transfers occlusal breaking to the supporting periodontal ligament. A dental implant has no periodontal ligament but can have a rough surface that may preclude implant failure.

Glyburide inhibits the bone resorption induced by traumatic occlusion in rats.

OBJECTIVE: To examine whether glyburide inhibits bone destruction caused by traumatic occlusion in a rat occlusal trauma model. BACKGROUND: Excessive mechanical stress, such as traumatic occlusion, induces expression of IL-1ß and may be involved in bone resorption. NLRP3 inflammasomes have been linked to IL-1ß expression, but it is currently unclear whether glyburide, the inhibiter of NLRP3 inflammasome, suppresses occlusal trauma in rats. METHODS: Male SD rats aged 7 weeks were used. In the trauma group, the occlusal surface of the maxillary first right molar was raised by attaching a metal wire to apply occlusal trauma to the mandibular first right molar. In the trauma + glyburide group, the NLRP3 inhibitor glyburide was administered orally every 24 hours from 1 day before induction of occlusal trauma. Rats were euthanized after 5 or 10 days, and the maxillary first molars were harvested with the adjacent tissues for histopathological investigation. Immunohistochemical expression of IL-1ß, NLRP3, and RANKL was also assessed. RESULTS: On day 5, bone resorption was significantly greater in the trauma group compared with the control group or the trauma + glyburide group, and there were significantly higher numbers of osteoclasts and cells positive for IL-1ß, NLRP3, and RANKL in the trauma group. CONCLUSION: In this study, glyburide inhibits bone resorption by traumatic occlusion in rats. It suggests that the NLRP3/IL-1ß pathway might be associated with bone resorption induced by traumatic occlusion.

Traumatic occlusion aggravates bone loss during periodontitis and activates Hippo-YAP pathway.

AIM: This study aimed at exploring changes in YAP expression and their effect on periodontitis (PD) combined with traumatic occlusion (TO). MATERIALS AND METHODS: BALB/cJ mice were used to establish a PD model by local administration of Porphyromonas gingivalis (P.g, ATCC 33277) and a TO model by occlusal elevation (OE) using composite resin bonding on the bilateral maxillary molar. The mouse fibroblast cell line (L929) and pre-osteoblast cell line (MC3T3-E1) were subjected to cyclic tensile/compressive stress and inflammatory stimuli (lipopolysaccharide from Escherichia coli) to verify in vivo results. RESULTS: Severe bone resorption was observed by microCT scanning in OE with P.g group, when compared to OE only and P.g only groups. Mechanical stress caused by OE activated the Hippo-YAP pathway in periodontal tissues and upregulated the expression of JNK/AP-1. OE with P.g further promoted the expression of YAP and JNK/AP1, leading to the upregulation of the JNK/AP-1 related inflammatory cytokines TNF-α and IL6. Similar results were obtained when osteoblasts were subjected to mechanical stress in vitro. CONCLUSIONS: Our study demonstrated that periodontitis with TO caused severe inflammation-induced bone resorption. Activation of YAP and upregulation of JNK/AP-1 induced by TO potentially aggravated the symptoms of PD.

Metallic crown-induced occlusal trauma as a protocol to evaluate inflammatory response in temporomandibular joint and periodontal tissues of rats.

OBJECTIVES: The goal of this study is to propose a standard protocol of experimental occlusal trauma to evaluate the inflammatory hyperalgesia induced by metallic crowns on orofacial tissues of rats. MATERIALS AND METHODS: Thirty animals were randomly divided into six groups (n = 5 per group). Detailed methodology on the manufacturing of metallic crowns is described. The inflammatory hyperalgesia induced by occlusal interference was evaluated by intra-articular injection of a low dose of 0.5% formalin (30 µl) or vehicle (saline) into temporomandibular joint, 21 or 28 days after metallic crown cementation. Posteriorly, pro-inflammatory cytokines were evaluated by enzyme-linked immunosorbent assay to assess the effect of occlusal interference on periodontium. RESULTS: The cementation of metallic crowns with dental anatomy on the lower molar of rats does not show signs of stress and lack of feeding. Metallic crown-induced occlusal trauma results in a temporomandibular joint inflammatory hyperalgesia (P < 0.05: ANOVA, Tukey's test). Otherwise, it was observed that occlusal trauma results in the increase of protein level of pro-inflammatory cytokines TNF-alpha and IL-1beta in the gingival tissues (P < 0.05). CONCLUSION: This study demonstrates in detail a methodology of occlusal trauma resulting from the cementation of metallic crowns in the lower molars of rats, mimicking occlusal interferences commonly evaluated in the dental clinic. This methodology makes new studies to better understand the mechanisms involved in the occlusal trauma of orofacial tissues possible. CLINICAL RELEVANCE: The standardization of an experimental occlusal interference model will allow us to understand the deleterious effect and mechanisms that affect the orofacial tissues.

Periodontal manifestations of systemic diseases and developmental and acquired conditions: Consensus report of workgroup 3 of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions.

BACKGROUND: A variety of systemic diseases and conditions can affect the course of periodontitis or have a negative impact on the periodontal attachment apparatus. Gingival recessions are highly prevalent and often associated with hypersensitivity, the development of caries and non-carious cervical lesions on the exposed root surface and impaired esthetics. Occlusal forces can result in injury of teeth and periodontal attachment apparatus. Several developmental or acquired conditions associated with teeth or prostheses may predispose to diseases of the periodontium. The aim of this working group was to review and update the 1999 classification with regard to these diseases and conditions, and to develop case definitions and diagnostic considerations. METHODS: Discussions were informed by four reviews on 1) periodontal manifestions of systemic diseases and conditions; 2) mucogingival conditions around natural teeth; 3) traumatic occlusal forces and occlusal trauma; and 4) dental prostheses and tooth related factors. This consensus report is based on the results of these reviews and on expert opinion of the participants. RESULTS: Key findings included the following: 1) there are mainly rare systemic conditions (such as Papillon-Lefevre Syndrome, leucocyte adhesion deficiency, and others) with a major effect on the course of periodontitis and more common conditions (such as diabetes mellitus) with variable effects, as well as conditions affecting the periodontal apparatus independently of dental plaque biofilm-induced inflammation (such as neoplastic diseases); 2) diabetes-associated periodontitis should not be regarded as a distinct diagnosis, but diabetes should be recognized as an important modifying factor and included in a clinical diagnosis of periodontitis as a descriptor; 3) likewise, tobacco smoking - now considered a dependence to nicotine and a chronic relapsing medical disorder with major adverse effects on the periodontal supporting tissues - is an important modifier to be included in a clinical diagnosis of periodontitis as a descriptor; 4) the importance of the gingival phenotype, encompassing gingival thickness and width in the context of mucogingival conditions, is recognized and a novel classification for gingival recessions is introduced; 5) there is no evidence that traumatic occlusal forces lead to periodontal attachment loss, non-carious cervical lesions, or gingival recessions; 6) traumatic occlusal forces lead to adaptive mobility in teeth with normal support, whereas they lead to progressive mobility in teeth with reduced support, usually requiring splinting; 7) the term biologic width is replaced by supracrestal tissue attachment consisting of junctional epithelium and supracrestal connective tissue; 8) infringement of restorative margins within the supracrestal connective tissue attachment is associated with inflammation and/or loss of periodontal supporting tissue. However, it is not evident whether the negative effects on the periodontium are caused by dental plaque biofilm, trauma, toxicity of dental materials or a combination of these factors; 9) tooth anatomical factors are related to dental plaque biofilm-induced gingival inflammation and loss of periodontal supporting tissues. CONCLUSION: An updated classification of the periodontal manifestations and conditions affecting the course of periodontitis and the periodontal attachment apparatus, as well as of developmental and acquired conditions, is introduced. Case definitions and diagnostic considerations are also presented.

Angiogenic mechanisms of human dental pulp and their relationship with substance P expression in response to occlusal trauma.

Angiogenesis is the formation of new blood vessels based on a pre-existing vasculature. It comprises two processes, sprouting of endothelial cells and the division of vessels due to abnormal growth of the microvasculature. It has been demonstrated that substance P (SP) can induce angiogenesis either by modulating endothelial cell growth (direct mechanism) or by attracting cells with angiogenic potential to the injury site (indirect mechanism). Therefore, the purpose of this article is to review the angiogenic mechanisms that regulate mineralized tissue formation in human dental pulp tissue and their relationship with SP expression as a defence response to stimuli such as the masticatory function and occlusal trauma. Articles included in this review were searched in PubMed, Scopus and ISI Web of Science databases, combining the following keywords: human dentine pulp, angiogenesis, angiogenic growth factors, neuropeptides, substance P, neurogenic inflammation, dentine matrix, dentinogenesis, occlusal trauma and dental occlusion. It is concluded that human dental pulp tissue responds to occlusal trauma and masticatory function with a neurogenic inflammatory phenomenon in which SP plays an important role in the direct and indirect mechanisms of angiogenesis by the action evoked via NK1 receptors at different cells, such as fibroblasts, endothelial and inflammatory cells, leading to new blood vessel formation which are needed to stimulate mineralized tissue formation as a defence mechanism.

Horizontal root fractures in posterior teeth without dental trauma: tooth/root distribution and clinical characteristics.

AIM: To describe the clinical characteristics and radiographic findings of horizontal root fractures (HRF) in posterior teeth without a history of dental trauma. METHODOLOGY: A total 24 patients and 31 HRF cases in 28 posterior teeth were collected from 2006 to 2015. Clinical examinations and radiographic imaging were evaluated. Value of confidence intervals of the proportions was calculated for data presentation. RESULTS: The number of males (54%) was similar to females (46%). The patients were predominantly between 50 and 70 years of age (75%). Most HRF cases were found in nonendodontically treated teeth (79%), without crown and bridge restorations (82%), and maxillary molars (54%). Many roots of maxillary molars had developed HRF, and the probability was nearly equal. Fractured teeth usually presented with periodontal and apical bone loss, and most patients (92%) were diagnosed with full mouth chronic periodontitis. Tooth wear was another common clinical feature amongst these patients. CONCLUSIONS: HRF in posterior teeth without dental trauma occurred mainly in patients aged between 50 and 70, in nonendodontically treated teeth, teeth with attrition but without crown and bridge restorations, maxillary molars and with periodontal and periapical bony destruction. Periodontal condition, occlusal wear and patients' age at diagnosis were the possible related factors. HRF in posterior teeth without dental trauma is a diagnostic challenge and even misdiagnosed. A thorough clinical examination, radiographic analysis and recognition of the clinical characteristics are helpful in the early diagnosis and treatment of HRF.

Functional Role of HSP47 in the Periodontal Ligament Subjected to Occlusal Overload in Mice.

We carried out an experiment to induce traumatic occlusion in mice periodontal tissue and analyzed the expression of HSP47. Continuous traumatic occlusion resulted to damage and remodeling of periodontal ligament as well as increase in osteoclasts and bone resorption. Four days after traumatic occlusion, osteoclasts did not increase but Howship's lacunae became enlarged. That is, the persistent occlusal overload can destroy collagen fibers in the periodontal ligament. This was evident by the increased in HSP47 expression with the occlusal overload. HSP47 is maintained in fibroblasts for repair of damaged collagen fibers. On the other hand, osteoclasts continue to increase although the load was released. The osteoclasts that appeared on the alveolar bone surface were likely due to sustained activity. The increase in osteoclasts was estimated to occur after load application at day 4. HSP47 continued to increase until day 6 in experiment 2 but then reduced at day 10. Therefore, HSP47 appears after a period of certain activities to repair damaged collagen fibers, and the activity was returned to a state of equilibrium at day 30 with significantly diminished expression. Thus, the results suggest that HSP47 is actively involved in homeostasis of periodontal tissue subjected to occlusal overload.

Cytological Kinetics of Periodontal Ligament in an Experimental Occlusal Trauma Model.

Using a model of experimental occlusal trauma in mice, we investigated cytological kinetics of periodontal ligament by means of histopathological, immunohistochemical, and photographical analysis methods. Periodontal ligament cells at furcation areas of molar teeth in the experimental group on day 4 showed a proliferation tendency of periodontal ligament cells. The cells with a round-shaped nucleus deeply stained the hematoxylin and increased within the day 4 specimens. Ki67 positive nuclei showed a prominent increase in the group on days 4 and 7. Green Fluorescent Protein (GFP) positivity also revealed cell movement but was slightly slow compared to Ki67. It indicated that restoration of mechanism seemed conspicuous by osteoclasts and macrophages from bone-marrow-derived cells for the periodontal ligament at the furcation area. It was suggested that the remodeling of periodontal ligament with cell acceleration was evoked from the experiment for the group on day 4 and after day 7. Periodontal ligament at the furcation area of the molar teeth in this experimental model recovered using the cells in situ and the bone-marrow-derived cells.

Occlusal trauma accelerates attachment loss at the onset of experimental periodontitis in rats.

BACKGROUND AND OBJECTIVE: Occlusal trauma is an important factor that influences the progression of periodontitis, but it is unclear whether occlusal trauma influences periodontal destruction at the onset of periodontitis. We established an experimental periodontitis model with both site-specific loss of attachment and alveolar bone resorption. The purpose of the present study was to investigate the effects of occlusal trauma on periodontal destruction, particularly loss of attachment, at the onset of experimental periodontitis. MATERIAL AND METHODS: Sixty rats were used in the present study. Forty-eight rats immunized with lipopolysaccharide (LPS) intraperitoneally were divided into four groups. In the trauma (T) group, occlusal trauma was induced by placing an excessively high metal wire in the occlusal surface of the mandibular right first molar. In the inflammation (I) group, periodontal inflammation was induced by topical application of LPS into the palatal gingival sulcus of maxillary right first molars. In the trauma + inflammation (T+I) group, both trauma and periodontal inflammation were simultaneously induced. The PBS group was administered phosphate-buffered saline only. Another 12 nonimmunized rats (the n-(T+I) group) were treated as described for the T+I group. All rats were killed after 5 or 10 d, and their maxillary first molars with surrounding tissues were observed histopathologically. Loss of attachment and osteoclasts on the alveolar bone crest were investigated histopathologically. To detect immune complexes, immunohistological staining for C1qB was performed. Collagen fibers were also observed using the picrosirius red-polarization method. RESULTS: There were significant increases in loss of attachment and in the number of osteoclasts in the T+I group compared with the other groups. Moreover, widespread distribution of immune complexes was observed in the T + I group, and collagen fibers oriented from the root surface to the alveolar bone crest had partially disappeared in the T, T+I and n-(T+I) groups. CONCLUSION: When inflammation was combined with occlusal trauma, immune complexes were confirmed in more expanding areas than in the area of the I group without occlusal trauma, and loss of attachment at the onset of experimental periodontitis was increased. Damage of collagen fibers by occlusal trauma may elevate the permeability of the antigen through the tissue and result in expansion of the area of immune-complex formation and accelerating inflammatory reaction. The periodontal tissue destruction was thus greater in the T+I group than in the I group.

Clinical issues in occlusion - Part I.

Good occlusal practise provides an important cornerstone to optimal patient care. Occlusal problems can manifest in different areas of dentistry but these are more apparent when there are restorative aspects to the patient׳s problem. This review highlights areas of restorative dentistry where the appreciation of occlusal aspects can optimise diagnosis and follow up care.

Experimental traumatic occlusion drives immune changes in trigeminal ganglion.

We previously demonstrated that experimental traumatic occlusion (ETO) induces a long-lasting nociceptive response. These findings were associated with altered neuronal patterns and suggestive satellite glial cell activation. This study aimed to elucidate the activation of satellite glial cells following ETO in the trigeminal ganglion. Moreover, we explored the involvement of resident and infiltrating cells in trigeminal ganglion in ETO. Finally, we investigated the overexpression of purinergic signaling and the CX3CL1/CX3CR1 axis. RT-qPCR and electrophoresis showed overexpression of GFAP in the trigeminal ganglion (TG), and immunohistochemistry corroborated these findings, demonstrating SGCs activation. ELISA reveals enhanced levels of TNF-α and IL-1ß in TG after 28 d of ETO. In trigeminal ganglia, ETO groups improved the release of CX3CL1, and immunohistochemistry showed higher CX3CR1+ -immunoreactive cells in ETO groups. Immunohistochemistry and electrophoresis of the P2X7 receptor were found in ETO groups. The mRNA levels of IBA1 are upregulated in the 0.7-mm ETO group, while immunohistochemistry showed higher IBA1+ -immunoreactive cells in both ETO groups. The expression of CD68 by electrophoresis and immunohistochemistry was observed in the ETO groups. For last, ELISA revealed increased levels of IL-6, IL-12, and CCL2 in the TG of ETO groups. Furthermore, the mRNA expression revealed augmented transcription factors and cytokines associated with lymphocyte activation, such as RORγt, IL-17, Tbet, IFNγ, FOXP3, and IL-10. The findings of this study suggested that ETO activates SGCs in TG, and purinergic signaling and CX3CL1/CX3CR1 axis were upregulated. We uncovered the involvement of a distinct subtype of macrophages, named sensory neuron-associated macrophage activation (sNMAs), and detected an expanded number of infiltrated macrophages onto TG. These findings indicate that ETO induces chronic/persistent immune response.