Early-stage periodontal ligament compression predicts orthodontically induced root resorption in rats

OBJECTIVES

To determine the effect of orthodontic pressure on periodontal ligament (PDL) compression in rats and assess correlation between PDL compression and orthodontically induced root resorption (OIRR).

MATERIALS AND METHODS

Eight female Wistar rats aged 10 weeks underwent surgery to place 2 mini-screws at the center of the palatal plate. 25 cN coil springs connecting the maxillary first molars and mini-screws were applied bilaterally to generate mesial force. Maxillary first molars were assigned to undergo either bodily or tipping movements. Micro-computed tomography (μCT) scans were taken on days 0, 3, 7, and 14, and histological sections were taken on day 14. OIRR was measured from histological sections, and the corresponding PDL compression ratio was quantified using μCT images.

RESULTS

The PDL was compressed by approximately 76% in tipping movement and 55% in bodily movement after 3 days, and by approximately 47% in bodily and tipping movements after 7 days of orthodontic force application. The extent of OIRR in tipping movement was significantly greater than that in bodily movement. A strong positive correlation between OIRR and PDL compression ratio was observed on day 3; however, no correlation was observed on day 7.

CONCLUSIONS

A strong correlation between PDL compression ratio and OIRR was observed at an early stage after the application of orthodontic force regardless of the tooth movement type (bodily or tipping), implying the importance of early stage PDL compression in the induction of OIRR.

Risk factors for dental findings of the development of medication-related osteonecrosis of the jaw: Investigation of 3734 teeth in cancer patients receiving high dose antiresorptive agents

Background/purpose

Local infection is a risk factor for medication-related osteonecrosis of the jaw (MRONJ), along with invasive dental treatment of the bone; the tooth that is the source of infection should be extracted prior to the administration of bone resorption inhibitors. However, which teeth should be extracted remains unclear. This study aimed to determine the relationship between dental findings prior to high-dose antiresorptive agent (ARA) administration and the subsequent development of MRONJ.

Materials and methods

Patients with cancer who were scheduled to receive high-dose ARAs and referred to our hospital between 2011 and 2020 were included in this retrospective study. Apical lesions, enlargement of the periodontal space, thickening of the lamina dura, alveolar bone resorption of >1/3, periapical osteosclerosis, and local infection symptoms in each tooth were investigated using medical records and panoramic radiographs.

Results

A total of 172 patients, 329 jaws, and 3734 teeth were registered. MRONJ developed in 68 teeth in 33 jaws of 32 patients. In tooth-by-tooth analysis, fewer teeth (P < 0.001), apical lesions (P < 0.001), periapical osteosclerosis (P < 0.001), local infection symptoms (P = 0.002), and one or more dental findings (P < 0.001) were significant factors for MRONJ development. In jaw-by-jaw analysis, old age, local infection symptoms, and number of radiographic abnormalities per tooth were significant. In patient-by-patient analysis, patients with diabetes and those with fewer teeth developed MRONJ.

Conclusion

Patients with fewer teeth, apical lesions, periapical osteosclerosis, and local infection were more likely to develop MRONJ. Therefore, these teeth should be treated as much as possible before ARA administration.

Fixation of an orthodontic anchor screw using beta-tricalcium phosphate in a screw-loosening model in rats

OBJECTIVES

To create an orthodontic anchor screw (OAS)-loosening model and to investigate whether filling the bone hole with beta-tricalcium phosphate (β-TCP) can fix the OAS against orthodontic force.

MATERIALS AND METHODS

Bone holes with different diameters (1.6, 2.1, or 2.5 mm) were drilled in the tibias of 11-week-old male Wistar rats, and an OAS (3.0 mm in length and 1.2 mm in diameter) was inserted. After a healing period of 2 or 4 weeks, orthodontic force was applied, and the diameter of the bone hole appropriate for the loosening model was determined. Subsequently, under the loosening model, the bone hole was filled with β-TCP, orthodontic force was applied, and movement of the OAS and surrounding tissue changes were evaluated by micro-computed tomography images and histological specimen analysis.

RESULTS

The bone hole of 1.6 mm in diameter was employed as the OAS-loosening model. When β-TCP was inserted into the bone hole, the linear distance and mesial tipping angle of the OAS movement decreased markedly. Furthermore, the values of bone morphometry significantly increased with β-TCP filling.

CONCLUSIONS

An OAS-loosening model was established in rats and demonstrated that the loosening OAS was stabilized by β-TCP filling through bone formation. β-TCP may be useful for fixation of a loosening OAS.

The effect of masseter muscle mass on the rate of experimental tooth movement in rats

BACKGROUND

Previous clinical observational studies have suggested that orthodontic tooth movement (OTM) is related, at least partly, to the mass and/or capabilities of the masticatory muscles.

OBJECTIVES

Our study aimed to examine the influence of masticatory muscle mass on the OTM in an animal experimental model in which the masseter muscle was modulated by botulinum neurotoxin type A (BTX) injection.

METHODS

Eighteen Wistar rats were equally divided into two groups: BTX injection and control. BTX was injected bilaterally into the masseter muscles. Three days after the injection, the maxillary left first molars were orthodontically moved for 14 days. At the end of the experiment, micro-computed tomography was performed to evaluate the rate of OTM and bone morphometry. The masseter muscles were weighed and prepared for histological analyses.

RESULTS

The masseter muscle mass in the BTX group was less than that in the control group, and histological findings showed atrophy of muscle fibers. The rate of OTM was significantly higher in the BTX group than in the control group. Furthermore, a negative correlation was detected between masseter muscle mass and OTM in the BTX group. Bone morphometry showed no difference between the control and BTX groups.

CONCLUSION

Decreased masseter muscle mass was found to be closely related to an increase in the rate of OTM in rats using BTX injection to modify the masseter muscle mass. Masseter muscle mass could be a predictive factor for OTM in rats injected with BTX.

Lithium reduces orthodontically induced root resorption by suppressing cell death, hyalinization, and odontoclast formation in rats

OBJECTIVES

To examine whether lithium suppresses orthodontically induced root resorption (OIRR) via two mechanisms (prevention of hyalinization in periodontal tissue and suppression of odontoclasts) and to investigate the changes in the periodontal tissue and alveolar bone, focusing on the appearance of cell death, hyalinization, and odontoclasts.

MATERIALS AND METHODS

The maxillary first molars of 10-week-old male Wistar rats were moved mesially by a closed-coil spring for 14 days. Lithium chloride (LiCl; 0.64 mM/kg) or saline (control) was administered intraperitoneally daily. Tooth movements were measured using micro-computed tomography. Appearances of cell death, hyalinization, and odontoclasts were evaluated by histological analysis.

RESULTS

OIRR observed on day 14 in the control group was suppressed strongly by LiCl administration. Apoptotic cells observed on day 1 in the compression area were gradually diminished on days 2 and 3 and transformed to hyalinization tissue in the control group. LiCl administration remarkably suppressed this cell death and subsequent hyalinization. Also, the appearance of odontoclasts in the compression area observed on day 7 was significantly suppressed by LiCl administration. Accordingly, these degenerative processes to OIRR were suppressed substantially by LiCl treatment.

CONCLUSIONS

Lithium reduces OIRR through the suppression of periodontal ligament cell death, hyalinization, and odontoclast formation.

A severe skeletal Class III malocclusion treated with Le Fort I combined with sagittal split ramus osteotomy, mandibular body ostectomy and tongue reduction surgery. A case report

This case report describes the orthodontic-orthognathic management of a 17-year-old male patient with extremely severe skeletal Class III malocclusion due to a marked mandibular protrusion with a small and narrowed upper jaw which increased the remarkable concave facial profile. Dental articulation was entirely lacking, resulting in great difficulty in masticating food. A two-jaw surgery combined with mandibular body ostectomy was performed to correct mandibular asymmetry and the severe sagittal skeletal discrepancy (Wits appraisal –36.5 mm and ANB angle –14.3°). Bi-maxillary surgery was performed in two-stages; the first surgery consisted of maxillary advancement with Le Fort I osteotomy followed by a second surgery where a combination of sagittal split ramus osteotomy (SSRO) and mandibular body ostectomy was performed to correct the severe mandibular prognathism. A partial glossectomy was also carried out to address macroglossia. After a total treatment time of 32 months, a Class I occlusion with a favorable facial profile and lip competence were obtained. The occlusion was made approximately ideal, and mastication improved remarkably. Three years after retention, the occlusion was stable and no relapse was observed. The patient’s complaints and orthodontic problems were completely resolved. Therefore, a combination of two-jaw surgeries with Le Fort I maxillary osteotomy, mandibular SSRO, mandibular ostectomy, and glossectomy may be a viable option in the correction of extremely severe anteroposterior skeletal discrepancy.

A case of periosteal fasciitis located in the mandible in a child

Periosteal fasciitis (PF), a subtype of nodular fasciitis, is an uncommon benign soft-tissue mass that originates from the periosteum or tissues adjacent to bones. PF has rarely seen in children, especially involving in the mandible. This case report presents a rare case of PF originating from the periosteum of the mandible in an 11-year-old girl. She was referred to our hospital with fast-growing painless swelling in her left mandible. Computed tomography revealed an exophytic juxtacortical mass eroding the lower part of the left mandible and lower mandibular cortex with a periosteal reaction. The mass showed low signal intensity on T1-weighted magnetic resonance imaging (MRI) and high signal intensity on T2-weighted MRI. The apparent diffusion coefficient (ADC) of the lesion found to be moderate. Dynamic contrast-enhanced MRI revealed a gradual increment pattern in the central region of the mass. On 18F-fluorodeoxyglucose (FDG) positron-emission tomography/computed tomography (PET/CT), relatively high 18F-FDG uptake was observed on the early scan and the 18F-FDG uptake was declined on the delayed scan. The clinical and conventional radiological findings of the mass were suggestive of malignancy. However, the findings of ADC and dynamic MRI and dual-time-point FDG-PET/CT favored benign etiology over malignant etiology. Histological and immunohistochemical findings along with reactive ossification of the periosteum confirmed the diagnosis of PF. Currently, comprehensive examinations, such as clinical, imaging, and histopathological examinations, are recommended for the definitive diagnosis of PF, while MRI and dual-time-point FDG-PET/CT could have a potential usefulness to differentiate from malignancy.

Traumatic myositis ossificans: multifocal lesions suggesting malignancy on FDG-PET/CT-a case report

Myositis ossificans (MO) is a benign soft-tissue lesion characterized by the heterotopic formation of the bone in skeletal muscles, usually due to trauma. MO is occasionally difficult to diagnose because of its clinical and radiological similarities with malignancy. We report a case of traumatic MO (TMO) in the masseter and brachial muscles of a 37-year-old man who presented with painless swelling in the left cheek and severe trismus. Due to the absence of a traumatic history at the first consultation and identification of a tumorous lesion in the left masseter muscle by magnetic resonance imaging (MRI), the lesion was suspected to be a malignant tumor. Subsequently, 18F-fluorodeoxyglucose positron-emission tomography/computed tomography (FDG-PET/CT) showed multiple regions of high FDG uptake across the whole body, suggestive of multiple metastases or other systemic diseases. However, intramuscular calcifications were also observed in the left masseter and brachial muscles, overlapping the areas with high FDG uptake. Moreover, multiple fractures were seen in the rib and lumbar spine, also overlapping the areas with high FDG uptake. Based on these imaging findings, along with a history of jet-ski trauma, TMO was suspected. The left cheek mass was surgically excised and histologically diagnosed as TMO. In this case report, FDG-PET/CT could detect multiple TMOs across the whole body. To the best of our knowledge, cases of multiple TMOs located far apart in different muscles are rare, and this may be the first report.

ATM-associated signalling triggers the unfolded protein response and cell death in response to stress

Endoplasmic reticulum (ER) stress can be caused by perturbations in ER function resulting from the accumulation of unfolded/misfolded proteins in the ER lumen. Accumulating unfolded proteins trigger unfolded protein responses (UPRs) through activating three transmembrane sensors on the ER: IRE1α, PERK, and ATF6. The orchestrated action of these molecules upregulates genes encoding proteins involved in the downregulation of protein synthesis and acceleration of protein secretion. Ineffectiveness of these fail-safe mechanisms may lead to apoptosis. However, the molecular mechanisms upstream of the UPR are not fully understood. Here we show participation of ataxia telangiectasia mutated (ATM) in stress-induced apoptosis. Cytoplasmic ATM serves as a platform on which protein phosphatase 2A-dependent dephosphorylation of AKT activates glycogen synthase kinase 3β, thereby downregulating nascent polypeptide-associated complex α subunit and γ-taxilin, triggering UPRs and leading to mitochondria-dependent apoptosis. These results suggest an ATM/AKT-dependent cell death pathway triggered by various forms of stress.

Hotokezaka et al. identify a role for ataxia telangiectasia mutated (ATM) in stress-induced signalling responses. They show that ATM–associated protein phosphatase 2A mediates dephosphorylation of AKT which triggers the unfolded protein response leading to mitochondria-dependent apoptosis in response to various forms of stress.

Phase 1 clinical study of cell therapy with effective-mononuclear cells (E-MNC) for radiogenic xerostomia (first-in-human study) (FIH study on E-MNC therapy for radiogenic xerostomia)

BACKGROUND

Treatment for most patients with head and neck cancers includes ionizing radiation with or without chemotherapy. This treatment causes irreversible damage to salivary glands in the irradiation field accompanied by a loss of fluid-secreting acinar cells and a considerable decrease of saliva secretion. There is currently no adequate conventional treatment for this condition. In recent years, we developed an effective culture method to enhance the anti-inflammatory and vasculogenic phenotypes of peripheral blood mononuclear cells (PBMNCs), and such effectively conditioned PBMNC (E-MNC) therapy has shown promising improvements to the function of radiation-injured salivary glands in preclinical studies. However, the safety and effect of E-NMC therapy have yet assessed in human. The objective of this ongoing first-in-man study is to assess the safety, tolerability, and in part the efficacy of E-MNC therapy for treating radiation-induced xerostomia.

METHODS/DESIGN

This phase 1 first-in-man study is an open-label, single-center, two-step dose escalation study. A total of 6 patients, who had no recurrence of head and neck cancer over 5 years following radiation therapy and suffered from radiation-induced xerostomia, will receive a transplantation of E-NMCs derived from autologous PBMNCs to a submandibular gland. The duration of the intervention will be 1 year. To analyze the recovery of salivary secretion, a gum test will be performed. To analyze the recovery of atrophic salivary glands, computed tomography (CT), and magnetic resonance imaging (MRI) of salivary glands will be conducted. The primary endpoint is the safety of the protocol. The secondary endpoints are the changes from baseline in whole saliva secretion and salivary gland atrophy.

DISCUSSION

This will be the first clinical study of regenerative therapy using E-MNCs for patients with severe radiation-induced xerostomia. The results of this study are expected to contribute to developing the low-invasive cell-based therapy for radiation-induced xerostomia.

TRIAL REGISTRATION

This study was registered with the Japan Registry of Clinical Trials (http://jrct.niph.go.jp) as jRCTb070190057.

A case of tophaceous pseudogout of the temporomandibular joint extending into the cranium

A case of tophaceous pseudogout (i.e., calcium pyrophosphate dihydrate crystal deposition disease) in the temporomandibular joint (TMJ) extending into the cranium is reported. A 59-year-old woman was referred to hospital with swelling and pain in the left cheek, and with trismus. Computed tomography imaging revealed a large, granular, calcified mass surrounding the left condylar head, partly destroying the cortex of the condylar head, and extending into the cranium by destroying the glenoid fossa. Magnetic resonance imaging revealed that the soft-tissue mass was of low-signal intensity on T1- and T2-weighted images, and was enhanced after intravenous injection of gadolinium. The mass was clinically and radiographically suspected to be a neoplastic lesion or a synovial osteochodromatosis. However, histological analysis demonstrated that the mass contained granulomatous lesion due to multiple nodular deposits of numerous rod-shaped and rhomboid crystals, which verified the diagnosis of tophaceous pseudogout. The lesion was excised surgically using a preauricular approach. Neither radiographic nor clinical examination demonstrated any signs of mass recurrence in the long-term 8- and 14-year postoperative recall examinations. Tophaceous pseudogout is a rare benign arthropathy that presents with clinical and radiographic features mimicking neoplastic conditions of the TMJ. Therefore, it is recommended that tophaceous pseudogout is considered in the differential diagnosis when a calcified mass lesion of the TMJ is encountered.

Lithium chloride reduces orthodontically induced root resorption and affects tooth root movement in rats

OBJECTIVE

To investigate the influence of lithium chloride (LiCl) on orthodontic tooth movement (OTM), orthodontically induced root resorption (OIRR), and bone morphometry.

MATERIALS AND METHODS

Ten-week-old female Sprague Dawley rats (n = 32) were divided into four groups based on the concentration of LiCl administered daily per kilogram body weight: 0 (control group), 0.32, 0.64, and 1.28 mM/kg body weight. The maxillary left first molars were moved mesially by a 10 cN coil spring for 14 days. Micro-computed tomography, scanning electron microscope, and scanning laser microscope images were taken to measure the amount of OTM, the volume of OIRR, and bone morphometry.

RESULTS

OIRR clearly decreased depending on the amount of LiCl administered, although OTM moderately decreased. The tooth inclined mesially and the root apex moved distally in the control and 0.32 mM groups. On the other hand, the tooth inclination angle became smaller and the root apex moved mesially in the 0.64 and 1.28 mM groups. In bone morphometry, the cortical bone mineral content and bone volume increased because of LiCl administration, and the trabecular bone measurements decreased. OIRR negatively correlated to the cortical bone measurements, and the amount of OTM significantly correlated to the cortical bone morphometry.

CONCLUSIONS

In rats, LiCl reduced OIRR, which induced mesial movement of the tooth root apex. OIRR positively correlated to cortical bone morphometry.

An in vivo 3D micro-CT evaluation of tooth movement after the application of different force magnitudes in rat molar

OBJECTIVE

To investigate the precise longitudinal change in the periodontal ligament (PDL) space width and three-dimensional tooth movement with continuous-force magnitudes in living rats.

MATERIALS AND METHODS

Using nickel-titanium closed-coil springs for 28 days, 10-, 25-, 50-, and 100-g mesial force was applied to the maxillary left first molars. Micro-CT was taken in the same rat at 0, 1, 2, 3, 10, 14, and 28 days. The width of the PDL was measured in the pressure and tension sides from 0 to 3 days. Angular and linear measurements were used to evaluate molar position at day 0, 10, 14, and 28. The finite element model (FEM) was constructed to evaluate the initial stress distribution, molar displacement, and center of rotation of the molar.

RESULTS

The initial evaluation of PDL width showed no statistical differences among different force magnitudes. Tooth movement was registered 1 hour after force application and gradually increased with time. From day 10, greater tooth movement was observed when 10 g of force was applied. The FEM showed that the center of rotation in the molar is located in the center of five roots at the apical third of the molar roots.

CONCLUSION

The rat's molar movement mainly consists of mesial tipping, extrusion of distal roots, intrusion of mesial root, palatal inclination, and mesial rotation. Although the initial tooth movement after the application of different force magnitudes until day 3 was not remarkably different, 10 g of force produced more tooth movement compared with heavier forces at day 28.

Molecular analysis of RANKL-independent cell fusion of osteoclast-like cells induced by TNF-alpha, lipopolysaccharide, or peptidoglycan

Focusing on the final step of osteoclastogenesis, we studied cell fusion from tartrate-resistant acid phosphatase (TRAP)-positive mononuclear cells into multinuclear cells. TRAP-positive mononuclear cells before generation of multinuclear cells by cell fusion were differentiated from RAW264.7 cells by treatment with receptor activator of nuclear factor kappa B ligand (RANKL), and then the cells were treated with lipopolysaccharide (LPS), followed by culturing for further 12 h. LPS-induced cell fusion even in the absence of RANKL. Similarly, tumor necrosis factor (TNF)-alpha and peptidoglycan (PGN) induced cell fusion, but M-CSF did not. The cell fusion induced by RANKL, TNF-alpha, and LPS was specifically blocked by osteoprotegerin (OPG), anti-TNF-alpha antibody, and polymyxin B, respectively. LPS- and PGN-induced cell fusion was partly inhibited by anti-TNF-alpha antibody but not by OPG. When TRAP-positive mononuclear cells fused to yield multinuclear cells, phosphorylation of Akt, Src, extracellular signal-regulated kinase (ERK), p38MAPK (p38), and c-Jun NH2-terminal kinase (JNK) was observed. The specific chemical inhibitors LY294002 (PI3K), PP2 (Src), U0126 (MAPK-ERK kinase (MEK)/ERK), and SP600125 (JNK) effectively suppressed cell fusion, although SB203580 (p38) did not. mRNA of nuclear factor of activated T-cells c1 (NFATc1) and dendritic cell-specific transmembrane protein (DC-STAMP) during the cell fusion was quantified, however, there was no obvious difference among the TRAP-positive mononuclear cells treated with or without M-CSF, RANKL, TNF-alpha, LPS, or PGN. Collectively, RANKL, TNF-alpha, LPS, and PGN induced cell fusion of osteoclasts through their own receptors. Subsequent activation of signaling pathways involving PI3K, Src, ERK, and JNK molecules was required for the cell fusion. Although DC-STAMP is considered to be a requisite for cell fusion of osteoclasts, cell fusion-inducing factors other than DC-STAMP might be necessary for the cell fusion.

Interaction of the eukaryotic elongation factor 1A with newly synthesized polypeptides

eEF1A, the eukaryotic homologue of bacterial elongation factor Tu, is a well characterized translation elongation factor responsible for delivering aminoacyl-tRNAs to the A-site at the ribosome. Here we show for the first time that eEF1A also associates with the nascent chain distal to the peptidyltransferase center. This is demonstrated for a variety of nascent chains of different lengths and sequences. Interestingly, unlike other ribosome-associated factors, eEF1A also interacts with polypeptides after their release from the ribosome. We demonstrate that eEF1A does not bind to correctly folded full-length proteins but interacts specifically with proteins that are unable to fold correctly in a cytosolic environment. This association was demonstrated both by photo-cross-linking and by a functional refolding assay.

The in vivo function of the ribosome-associated Hsp70, Ssz1, does not require its putative peptide-binding domain

Two proteins of the Hsp70 class (Ssb and Ssz1) and one of the J-type class (Zuo1) of molecular chaperones reside on the yeast ribosome, with Ssz1 forming a stable heterodimer with Zuo1. We designed experiments to address the roles of these two distantly related ribosome-associated Hsp70s and their functional relationship to Zuo1. Strains lacking all three proteins have the same phenotype as those lacking only one, suggesting that these chaperones all function in the same pathway. The Hsp70 Ssb, whose peptide-binding domain is essential for its in vivo function, can be crosslinked to nascent chains on ribosomes that are as short as 54 amino acids, suggesting that Ssb interacts with nascent chains that extend only a short distance beyond the tunnel of the ribosome. A ssz1 mutant protein lacking its putative peptide-binding domain allows normal growth. Thus, binding of unfolded protein substrates in a manner similar to that of typical Hsp70s is not critical for Ssz1's in vivo function. The three chaperones are present in cells in approximately equimolar amounts compared with ribosomes. The level of Ssb can be reduced only a few-fold before growth is affected. However, a 50- to 100-fold reduction of Ssz1 and Zuo1 levels does not have a substantial effect on cell growth. On the basis of these results, we propose that Ssbs function as the major Hsp70 chaperone for nascent chains on the ribosome, and that Ssz1 has evolved to perform a nonclassical function, perhaps modulating Zuo1's ability to function as a J-type chaperone partner of Ssb.

Oral and maxillofacial radiology teaching file on the World Wide Web

An oral and maxillofacial radiology teaching file on the World Wide Web was created effective June 15, 1995. The file contains 106 cases (279 images) of 94 diseases in the oral and maxillofacial region.