Occlusal hypofunction causes periodontal atrophy and VEGF/VEGFR inhibition in tooth movement

Effects of Occlusal Contact on Maxillary Alveolar Bone Morphology in Patients with and without Anterior Open Bite: A Cross-Sectional Study

Background/Objectives: Anterior open bite (AOB) is characterized by the absence of occlusal contact between the maxillary and mandibular anterior teeth, while the posterior teeth are in contact when occluded. Here, we aimed to clarify the difference in maxillary alveolar bone morphology in adult patients with and without AOB. Methods: This cross-sectional study was conducted on 50 adults aged 18-39 years: 25 patients without AOB (control group; 13 males and 12 females; age: mean ± standard deviation [SD], 22.2 ± 4.5 years) and 25 patients with AOB (9 males and 16 females; age: 24.2 ± 6.4 years). Using cone-beam computed tomography images, the height of the maxillary alveolar bone crest in the anterior and posterior teeth and thickness of the alveolar cortical bone on the labial and palatal sides were measured and compared between the two groups. An independent t-test and Pearson's correlation analysis were used to examine statistical significance (p < 0.05). Results: The AOB group showed a significantly longer (p = 0.016) posterior alveolar crest and thinner cortical bone on the buccal (p < 0.001) and lingual (p = 0.009) sides of the anterior region and the buccal (p = 0.006) sides of the posterior region than the control group did. Moreover, a significant negative correlation (p = 0.046; r = -0.403) was observed between bite force and cortical bone thickness on the buccal side of the posterior region in the AOB group. Conclusions: It is suggested that the absence of occlusal contact in the anterior area influences the alveolar bone morphology of the maxilla.

Effect of micro-osteoperforations (MOPs) on the rate of en masse orthodontic tooth retraction : A randomized controlled trial

PURPOSE

To evaluate the effect of micro-osteoperforations (MOPs) on the rate of orthodontic tooth movement (OTM) during en masse anterior retraction.

MATERIALS AND METHODS

Twenty patients were randomly allocated into experimental and control group of 10 each. In the control group, en masse retraction was performed with sliding mechanics with a coil spring. In the experimental group after alignment and levelling, MOPs were performed mesially and distally to all six anterior teeth in the interdental cortical region on the labial aspect of both arches. MOPs were performed at the beginning of space closure (T0) and 1 month after beginning of space closure (T1). En masse retraction was performed with sliding mechanics with a coil spring. Measurements were recorded on digital models made from scanned plaster casts at the beginning of space closure (T0) and monthly at each follow-up visit for the next 4 months (T1, T2, T3, T4). The monthly rate of OTM, the overall rate of OTM, and the difference between OTM in the MOP period (T0-T2) and post-MOP (T2-T4) period in the experimental and control group were evaluated. A visual analogue scale (VAS) was used to evaluate patients' pain experience.

RESULTS

The overall rate of OTM was significantly greater in the experimental group for both arches in the MOP period (T0-T2) and also in the post-MOP period (T2-T4) as compared to the control group. Within the experimental group, the rate of OTM in the MOP period was significantly greater than in the post-MOP period, which in turn was greater than that of the control group. The patients reported only mild discomfort for 24 h after performing the MOPs, which then gradually decreased.

CONCLUSIONS

The use of MOPs is effective in increasing the rate of en masse tooth retraction in both the maxillary and the mandibular arch. The rate of tooth movement was greater even in the post-MOP period as compared to the control group.

Impact of occlusal contact pattern on dental stability and oromandibular system after orthodontic tooth movement in rats

How to ensure dental stability in new positions and reduce the likelihood of relapse is a major clinical concern in the orthodontic field. Occlusal contacts between arches may affect the transmission of masticatory forces, thereby influencing the biological response of the periodontal and the oromandibular system. Occlusion factors that may influence the stability after orthodontic tooth movement (OTM) remain largely unknown. Hence, this research was conducted in order to investigate the influence of different occlusal contact patterns on tooth stability and oromandibular system including the masseter muscle and the temporomandibular joint following OTM. By modifying the occlusal surfaces, in vivo animal study models with distinct occlusal patterns corresponding to clinical circumstances were established. The relapse distance of teeth and the level of inflammatory factors in the gingival cervical fluid were analyzed. We also closely observed the histological remodeling of periodontal tissue, masseter tissue, and joint tissue after one week of relapse. Moreover, genes expression in the alveolar bone was analyzed to illustrate the potential biological mechanisms of relapse under the influence of different occlusal contact patterns following OTM. Different occlusal contact patterns after OTM in rats were established. The intercuspation contact between cusp and fossa group exhibited the lowest level of relapse movement, inflammatory factors and osteoclast activity (P < 0.05). On the other hand, groups with interferences or inadequate contacts exhibited more relapse movement, and tend to promote inflammation of periodontal tissue and activate bone resorption (P < 0.05). Adequate occlusal contacts without interference may enhance tooth stability and reduce the likelihood of relapse. After active orthodontic treatment, necessary occlusal adjustment should be made to achieve the desired intercuspation contact relationship and ensure adequate contact between the arches. The elimination of occlusal interferences is crucial to achieving optimal stability and promoting overall healthy condition of the oromandibular system.

Effect of Mini-implant assisted Micro-osteoperforation on the rate of orthodontic tooth movement-A randomized clinical trial

OBJECTIVE

To evaluate the effectiveness of micro-osteoperforation (MOP) over a 56-day period and to determine the influence of number of perforations on the rate of canine retraction. In addition, the amount of pain and discomfort caused by the MOP was evaluated.

TRIAL DESIGN

A single-center, split-mouth, triple-blind, randomized, controlled trial.

METHODS

22 patients (18-30 years) who need fixed orthodontic treatment were recruited and randomly assigned to MOP1 and MOP2 groups. The recruited patients were divided into two groups with 1:1 allocation ratio. Randomization for the determination of experimental side and number of perforations was done using sealed envelopes. On each patient, the other side of mouth worked as control side with no MOPs. 4 months after first premolar extraction, patients in MOP1 received 3MOPs on the buccal surface of alveolar bone, whereas patients in MOP2 received three buccal and three palatal MOPs in the experimental side. The amount of canine retraction was measured every 28 days at two intervals on both sides of mouth. Pain perception was measured after 1 hr, 24 hr, 72 hr, 7 days, and 28 days of procedure.

RESULTS

Result of the intra-examiner reliability using ICC is more than 0.97 (P < 0.001), indicating excellent repeatability and reliability of the measurements. The baseline characteristics between groups were similar (P > 0.05). A statistically significant difference in the rate of canine retraction on the MOP side was observed at the end of 56 days, amounting to two folds more than that of the control side. No significant difference was seen between MOP1 and MOP2 groups (P > 0.05). Mild-to-moderate pain was experienced only in first 72 hours of procedure.

CONCLUSION

The study recommends that MOP procedure has substantial potential to be used as an adjunct to the routine mechanotherapy for accelerating tooth movement, as it may reduce treatment time by half in the first four weeks after the MOP procedure.

TRIAL REGISTRATION

Clinical trial registry of India (CTRI/2022/12/048181).

Alteration of extracellular matrix proteins in atrophic periodontal ligament of hypofunctional rat molars

OBJECTIVES

The aim of this study was to investigate the effect of mechanical force on possible dynamic changes of the matrix proteins deposition in the PDL upon in vitro mechanical and in vivo occlusal forces in a rat model with hypofunctional conditions.

MATERIALS AND METHODS

Intermittent compressive force (ICF) and shear force (SF) were applied to human periodontal ligament stem cells (PDLSCs). Protein expression of collagen I and POSTN was analyzed by western blot technique. To establish an in vivo model, rat maxillary molars were extracted to facilitate hypofunction of the periodontal ligament (PDL) tissue of the opposing mandibular molar. The mandibles were collected after 4-, 8-, and 12-weeks post-extraction and used for micro-CT and immunohistochemical analysis.

RESULTS

ICF and SF increased the synthesis of POSTN by human PDLSCs. Histological changes in the hypofunctional teeth revealed a narrowing of the PDL space, along with a decreased amount of collagen I, POSTN, and laminin in perivascular structures compared to the functional contralateral molars.

CONCLUSION

Our results revealed that loss of occlusal force disrupts deposition of some major matrix proteins in the PDL, underscoring the relevance of mechanical forces in maintaining periodontal tissue homeostasis by modulating ECM composition.

Effect of platelet-rich plasma on the rate of orthodontic tooth movement

INTRODUCTION

This study aimed to evaluate the effect of platelet-rich plasma (PRP) on the rate of orthodontic tooth movement (OTM) during en-masse anterior retraction.

METHODS

Twenty adult patients with Angles Class I bimaxillary protrusion or crowding requiring first premolar extraction for routine orthodontic treatment were divided into control and experimental groups. The control group did not receive PRP, whereas the experimental group received PRP in the alveolar mucosa of the maxillary 6 anterior teeth just before starting en-masse retraction. Measurements were recorded on digital models made from scanned plaster casts at the beginning of space closure and the end of 3 months. The overall rate of OTM between both groups was compared. The amount of anchorage loss and type of anterior retraction on lateral cephalogram was also compared between the groups.

RESULTS

The overall rate of OTM was minimally increased but not statistically significant in the experimental vs control group (P = 0.838). Anterior retraction parameters in both groups showed incisors moving primarily by controlled tipping and partly by translation. An intergroup comparison of all cephalometric parameters for anchorage loss and anterior retraction showed statistically insignificant differences between both groups.

CONCLUSIONS

PRP is ineffective in accelerating the rate of OTM during en-masse anterior retraction.

The effect of micro-osteoperforations on orthodontic space closure investigated over 12 weeks: a split-mouth, randomized controlled clinical trial

OBJECTIVES

To evaluate the effects of minimally invasive micro-osteoperforations (MOPs) on orthodontic tooth movement and pain.

DESIGN

Prospective, split-mouth, randomized controlled trial.

SETTING

Single-centre, university hospital.

METHODS

Twenty subjects requiring maxillary first premolar extractions were included. Right and left sides of the maxilla were randomly allocated into experimental and controls. Space closure was initiated following alignment on 0.20″ stainless steel archwires, using 150 g force, applied by coil springs on power arms. Nance-TPA was used for anchorage. On the experimental side, two 5 mm deep MOPs in vertical alignment on distal aspect of the maxillary canine mid-root region were performed prior to space closure.

OUTCOMES

The primary outcome was the amount of tooth movement during space closure, measured every 4 weeks for 12 weeks (T1, T2, and T3). Secondary outcome was the pain levels related to MOP, measured using Visual Analogue Scale (VAS) questionnaires. Significance was set at P < 0.01.

RANDOMIZATION

Randomization was generated using a randomization table, and allocation was concealed in sequentially numbered, opaque, sealed envelopes.

BLINDING

Blinding was not possible during the experiment but assessor was blinded during outcome assessment.

RESULTS

All subjects completed the study, with tooth movement measurements available for all 20 patients for T0-T2. In three patients, space was closed on one side at T2. The average tooth movement between sides at three intervals (T0-T1, T1-T2, and T2-T3) were not significantly different. Overall difference following 12 weeks (T0-T3) was 0.69 mm higher on the experimental side (P < 0.001). No harms were observed.

LIMITATIONS

Short-term study, cast measurements done with digital callipers.

CONCLUSION

This 12-week randomized split-mouth controlled clinical trial showed two MOPs that are 5 mm deep, applied once prior to space closure, did not create clinically significant increase in maxillary premolar space closure.

PROTOCOL

The protocol was not published before trial commencement.

REGISTRATION

Trial was not registered.

FUNDING

The Australian Society of Orthodontists Foundation for Research and Education.

Effects of miniscrew-facilitated micro-osteoperforations on the rate of orthodontic tooth movement : A split-mouth, randomized controlled trial

PURPOSE

The aim of the present split-mouth randomized controlled trial was to evaluate the effects of miniscrew-facilitated micro-osteoperforations (MOPs) on the rate of orthodontic tooth movement during canine retraction.

METHODS

A total of 20 young adult patients (mean age 16.5 years) with the indication for bilateral maxillary first premolar extraction were included in the study. The MOPs were randomly applied to either the right or left side of the mouth with miniscrews (1.5 mm width, 8 mm length) to the extraction area, 28 days apart. The canine distalization continued for 3 months. The closure of the extraction space was measured by using a digital analysis program on the pre- and postdigital study models for both the control and experiment sides.

RESULTS

The mean rate of extraction space closure on the MOP side was 2.51 ± 1.41 mm and on the control side was 2.88 ± 1.32 mm. There was no statistically significant difference between the groups (p > 0.05).

CONCLUSION

Overall, we found that MOPs did not significantly affect the rate of orthodontic tooth movement during canine retraction.

BBS7-SHH Signaling Activity Regulates Primary Cilia for Periodontal Homeostasis

Objectives: Mechanical stimuli are essential for the maintenance of periodontal ligament (PDL) homeostasis. Although there are several studies on atrophic changes in PDL due to occlusal hypofunction, the underlying mechanism is still unknown. Here, we aimed to explore the changes of gene expression in occlusal hypofunctional PDL and elucidate the related role in maintaining the PDL homeostasis.

Methods: To investigate the transcriptomic difference between control and hypofunctional PDL tissue from patients, RNA sequencing was performed on 34 human teeth. The atrophic changes in PDL were evaluated by histological analysis. The effect of the Bardet-Biedl syndrome 7 (BBS7) knockdown was evaluated by the RT-qPCR, Western blot, wound healing, and tubule formation assay.

Results: We detected that the expression of BBS7 was downregulated in occlusal hypofunctional PDL through RNA sequencing. Dynamic changes, including the number of periodontal ligament cells, alignment of collagen fibers, diameter of blood vessels, appearance of primary cilia, and torturous oxytalan fibers, were observed following occlusal hypofunction. Furthermore, Sonic hedgehog signaling (Shh) activity was closely associated with BBS7 expression in PDL cells. In addition, the cell migration and angiogenesis were also suppressed by BBS7 knockdown in vitro.

Conclusion: We suggest that BBS7 plays an essential role in maintaining Shh signaling activity for PDL homeostasis.

The Effectiveness of Micro-osteoperforations during Canine Retraction: A Three-dimensional Randomized Clinical Trial

Aim:

A major challenge in orthodontics is decreasing treatment time without compromising treatment outcome. The purpose of this split-mouth trial was to evaluate micro-osteoperforations (MOPs) in accelerating orthodontic tooth movement.

Materials and Methods:

Eight patients of both genders were selected, age ranging between 15 and 40 years, with Class II Division 1 malocclusion. The participants in this trial with MOPs were randomly allocated to either the right or the left side, distal to the maxillary canine. First maxillary premolars were extracted as part of the treatment plan on both sides and then canine retraction was applied. Miniscrews were used to support anchorage. MOP side received (three small perforations) placed on the buccal bone, distal to the maxillary canine, on randomly selected side using an automated mini-implant driver and the other side was the control side. Blinding was used at the data collection and analysis stages. The primary outcome was the rate of canine retraction measured with a three-dimensional (3D) digital model from the baseline to the first 2 weeks superimposed at the rugae area from the baseline to the first, second, and third months. The following secondary outcomes were examined: anchorage loss, canine tipping, canine rotation, root resorption, plaque index, and gingival index. Pain level, pain interference with the patients’ daily life, patients’ satisfaction with the procedure and degree of ease, willingness to repeat the procedure, and recommendation to others were also evaluated.

Results:

No statistically significant difference was observed in the rates of tooth movement between the MOP and the control sides at all-time points (first month: P = 0.77; mean difference, 0.2 mm; 95% CI, −0.13, 0.18 mm; second month: P = 0.50; mean difference, −0.08 mm; 95% CI, −0.33, 0.16 mm; third month: P = 0.76; mean difference, −0.05 mm; 95% CI, −0.40, 0.29 mm). There were also no differences in anchorage loss, rotation, tipping, root resorption, plaque index, periodontal index, and pain perception between the MOP and control sides at any time point (P > 0.05). MOPs had no effect on the patients’ daily life except for a feeling of swelling on the first day (P = 0.05). Level of satisfaction and degree of easiness of the procedure were high.

Conclusion:

According to our clinical trial, MOPs cannot help in speeding up a canine retraction.

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.

Dental hypofunction alters subgingival microorganisms: a pilot study

BACKGROUND

The aim of this study was to evaluate dental plaque compositions, vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF) 1-alpha levels in gingival crevicular fluid (GCF) at hypofunctional and normofunctional teeth in healthy individuals and chronic periodontitis patients.

METHODS

Sixty systemically healthy individuals were enrolled. Study groups were: group 1 hypofunctional healthy group (group 1, N.=15); group 2 hypofunctional periodontitis group (group 2, N.=15); group 3 normofunctional healthy group (group 3, N.=15); and group 4 normofunctional periodontitis group (group 4, N.=15). Clinical periodontal measurements (plaque index, gingival index and clinical attachment level) were recorded. Dental plaque and GCF samples were taken. VEGF and HIF 1-alpha levels in GCF were determined. Subgingival plaque samples were evaluated for 11 different bacterial species as, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Prevotella intermedia, Peptostreptococcus micros, Fusobacterium nucleatum, Campylobacter rectus, Eubacterium nodatum, Eikenella corrodens and Capnocytophaga species.

RESULTS

Tannerella forsythia, Peptostreptococcus micros, Eubacterium nodatum levels decreased in hypofunctional healthy and periodontitis groups (P<0.05). Porphyromonas gingivalis levels increased in hypofunctional healthy group and decreased in hypofunctional periodontitis group (P<0.05). There was also a decrease in Eikenella corrodens levels in hypofunctional periodontitis group (P<0.05). There were no difference regarding the Aggregatibacter actinomycetemcomitans, Capnocytophaga spp., Prevotella intermedia and Fusobacterium nucleatum levels among the groups (P>0.05). VEGF and HIF-1α levels in both GCF and serum samples were also similar (P>0.05).

CONCLUSIONS

Within the limits of this study, the authors found that the levels of four significant bacterial strains were decreased in both hypofunctional healthy and hypofunctional periodontitis groups compared to normofunctional equivalents. Though not evaluated in this study, this situation could be due to periodontal ligament atrophy and related physiological alterations.

The circadian expression of osteogenic factors in periodontal tissue loading mechanical force: new concepts of the personalized orthodontic care

Objective

The need for orthodontic treatment continues to increase. Strategies that shorten the treatment course and reduce discomfort are most welcome in clinic. Circadian rhythm plays important role in various physiological processes, including bone formation. This study intended to depict a possible circadian releasing property of the osteogenic factors within the periodontal tissue during orthodontic treatment, which may direct a more efficient and satisfactory orthodontic treatment to the patient.

Methods

Primary periodontal ligament cells (PDLCs) were obtained from the Sprague-Dawley (SD) rats. An equibiaxial strain value of 12% was applied on rat PDLCs (rPDLCs). After 2 h stimuli of 10^-7 M dexamethasone (DX), the osteogenic genes' expressions were detected by real-time polymerase chain reaction (RT-PCR) at Zeitgeber times 0, 4, 8, 12, 16, 20, and 24. An orthodontic appliance was placed on 45 SD rats. Animals were maintained under 12-h light/dark periods and euthanized at 9 time points over the diurnal cycle. The orthodontic sensitive tissues of the mesial root of the maxillary first molar were collected for RT-PCR and immunohistological assay.

Results

The rPDLCs displayed typical fibroblastic spindle shape, and subcultured steadily in vitro. Induced by DX, the mRNA expression of Col-1, OPN, and IBSP within the loaded/unloaded rPDLCs oscillated as that of the main clock gene Per-1. The osteogenic genes' expressions as well as the protein releases sustained a circadian oscillation trend in vivo.

Conclusions

This study indicates the existence of a circadian rhythm of the osteogenic factors within the orthodontic sensitive tissues, which highlights the importance of precise timing of force loading in further orthodontic treatment. Thus, a periodicity pattern of orthodontic traction at night may prove a more efficient tooth movement while minimizing the treatment window and discomfort complains.

Comparison of piezocision and discision methods in orthodontic treatment

Background

Discision method may provide an alternative to the piezocision approach in accelerated orthodontic treatment. The purpose of this study was to investigate the efficacy of discision on accelerated orthodontic tooth movement in comparison to the piezocision method in moderate crowding Angle Class I malocclusions.

Methods

Thirty-five female individuals were included in this clinical study. The participants were classified into three groups as conventional fixed non-extraction orthodontic treatment only (OT, n = 14), piezocision in addition to fixed non-extraction orthodontic treatment (PG, n = 9), and discision in addition to fixed non-extraction orthodontic treatment (DG, n = 12). The piezocisions and discisions were performed 1 week after placement of bonding brackets. The patients were seen at 2–3 week-intervals. Initial Little’s irregularity index scores were recorded from dental casts. Periodontal parameters were measured initially, after the 1-month orthodontic treatment. Probing pocket depth, bleeding on probing, plaque index, and gingival index were recorded. Visual analog scale (VAS) was performed over the first month at different times following the bracket bonding for pain assessment. The total orthodontic treatment duration was noted.

Results

The duration of orthodontic treatment was statistically decreased in PG and DG compared to OT (P = 0.003). There was no statistical difference between PG and DG in orthodontic treatment duration (P > 0.05). There was no statistical difference between the two experimental groups in terms of VAS and periodontal parameter values (P > 0.05).

Conclusions

This is the first clinical orthodontic study to assess the effect of discision on the rate of orthodontic tooth movement. Discision is comparable to piezocision in terms of tooth movement acceleration, pain level, and periodontal status. The discision seems to be effective in reducing the time of orthodontic treatment.

Age-dependent biologic response to orthodontic forces

INTRODUCTION

Orthodontic tooth movement results from increased inflammation and osteoclast activation. Since patients of all ages now routinely seek orthodontics treatment, we investigated whether age-dependent biologic responses to orthodontic force correlate with the rate of tooth movement.

METHODS

We studied 18 healthy subjects, adolescents (11-14 years) and adults (21-45 years), with Class II Division 1 malocclusion requiring 4 first premolar extractions. Canines were retracted with a constant force of 50 cN. Gingival crevicular fluid was collected before orthodontic treatment and at days 1, 7, 14, and 28 after the canine retraction. Cytokine (IL-1β, CCL2, TNF-α) and osteoclast markers (RANKL and MMP-9) were measured using antibody-based protein assays. Pain and discomfort were monitored with a numeric rating scale. The canine retraction rate was measured from study models taken at days 28 and 56.

RESULTS

Although the cytokine and osteoclast markers increased significantly in both age groups at days 1, 7, and 14, the increases were greater in adults than in adolescents. Interestingly, the rate of tooth movement in adults was significantly slower than in adolescents over the 56-day study period. Adults also reported significantly more discomfort and pain.

CONCLUSIONS

Age is a significant variable contributing to the biologic response to orthodontic tooth movement. Adults exhibited a significantly higher level of cytokine and osteoclasts activity but, counterintuitively, had a significantly slower rate of tooth movement.

The chemokine receptor type 4 antagonist, AMD3100, interrupts experimental tooth movement in rats

OBJECTIVE

The aim of this study was to clarify the role of the stromal cell-derived factor-1 (SDF-1)/C-X-C chemokine receptor type 4 (CXCR4) axis in osteoclast accumulation, and the influence of orthodontic tooth movement (OTM) under mechanical force application to periodontal tissues, by administration of the CXCR4 antagonist AMD3100.

DESIGN

The upper right first molar (M1) of rats was moved mesially with a 10-g force titanium-nickel closed coil spring. Rats were treated with phosphate-buffered saline or AMD3100 (5mg/kg), which is a SDF-1 antagonist. After 0, 1, 3, and 7days, alveolar bones in all groups were examined at each time point by micro-computed tomography and histological analysis.

RESULTS

Tooth movement was decreased significantly in the AMD3100-treated group at 1, 3, and 7days after beginning OTM. The numbers of tartrate-resistant acid phosphatase-positive multinucleated cells in the periodontal ligament around the maxillary M1 were decreased significantly in the treated as compared to the control group on Days 1 and 3.

CONCLUSION

Administration of AMD3100 decreases OTM and osteoclast accumulation in rat molars under orthodontic force application. These findings suggest that the SDF-1/CXCR4 axis plays an important role in alveolar bone metabolism during OTM.

Three-dimensional alteration of constricted alveolar ridge affected by root thrusting with and without open-flap decortication

OBJECTIVE

To investigate the morphometric and histological alterations of the constricted alveolar ridge when affected by root thrusting with and without open-flap decortication.

MATERIALS AND METHODS

Eight beagles were divided into three groups: C, control without root thrusting; R, root thrusting only; RD, root thrusting with alveolar decortication. The ridge constriction model was prepared in 16 mandibular quadrants after extraction of the third premolars. Reciprocal root thrusting of the second and fourth premolars was performed toward the constricted ridge for 10 weeks, having a moment of 900 g-mm. Open-flap decortication was conducted on the constricted bone surface in group RD. Micro-CT-based histomorphometric analysis and trichrome-staining-based tissue fractional analysis were performed to evaluate morphometric and microstructural changes on the ridge.

RESULTS

Group R revealed a higher percentage of bone volume (P < .001), lower bone mineral density (P < .01), and higher trabecular number (P < .001) than did group C, which was supported by a higher bone fraction woven to lamellar bone (P < .05) resulting from histologic fractional analysis. However, group RD showed no significant difference from group C.

CONCLUSIONS

Root thrusting toward the constricted ridge induced hypertrophic bone modeling with a high trabecular fraction on the ridge. However, combined open-flap decortication with root thrusting did not improve the volume or quality of the constricted ridge.

A new approach to transfect NF-κB decoy oligodeoxynucleotides into the periodontal tissue using the ultrasound-microbubble method

The objective of this study is to investigate the effect of the ultrasound-microbubble technique in nuclear factor kappa B (NF-κB) decoy oligodeoxynucleotide (ODN) transfection in the gingival tissue in mice. The 6-FAM-labeled scrambled decoy ODN with microbubbles was applied to the periodontal tissue in 8-week-old male C57BL/6J mice by ultrasound radiation at low (LUM-Sc) and high (HUM-Sc) intensities to optimize the transfection condition of the ultrasound-microbubble method. Histological inspections were performed two hours after transfection to compare the expression with that in the sham-operated group without ultrasound radiation (A-Sc). Then, an NF-κB decoy was transfected into the periodontal tissue using the high-intensity ultrasound-microbubble (HUM-NF) technique to examine the anti-inflammatory effects of the decoy ODN. Western blot analysis was performed to investigate the expression of interleukin(IL)-1β, IL-6 and intercellular adhesion molecule-1 (ICAM-1) in the gingival tissues in the HUM-Sc, the HUM-NF and control groups. The fluorescence microscopy results showed that the fluorescent intensity in the periodontal tissues in the LUM-Sc and HUM-Sc groups was significantly higher than that in the A-Sc and the control groups. The fluorescent intensity in the HUM-Sc group, especially in the gingival connective tissue, was the highest of all groups. Western blot analysis indicated that the protein expression levels of IL-1β, IL-6 and ICAM-1 in the HUM-NF group were significantly lower than those in the HUM-Sc and the control groups. These findings suggest that the high-intensity ultrasound-microbubble technique is an effective tool for decoy transfection into the periodontal tissue.

Accelerated Tooth Movement with Orthodontic Mini-Screws

This case report outlines the possibility of accelerated tooth movement with the combination of microosteoperforation and mini-screws. A 14-year-old male patient presented Class II malocclusion with maxillary incisor protrusion. Upper first premolars were extracted, and after leveling, accelerated canine distalization started. For pre- and postdistalization times, amount of distalization, periodontal health, and root resorption were assessed. Within the limitations of this case report, micro-osteoperforations with mini-screw have a potential for shortening the treatment time.

Restoration of a vertical alveolar bone defect by orthodontic relocation of a mesially impacted mandibular first molar

An impacted mandibular first molar tends to cause serious bone defects of the adjacent teeth. When choosing between the 2 typical treatment options-extraction or orthodontic relocation of the impacted tooth-the decision should be based on assessment of the prognosis. A 22-year-old man with severe mesioangulation and impaction of the mandibular first molar and a related vertical bone defect on the distal side of the second premolar was treated with extraction of the second molar and orthodontic relocation of the first molar with a retromolar miniscrew. Comprehensive orthodontic treatment involving premolar extraction was conducted. Strategic extraction of the molar and adequate orthodontic movement helped to restore the bone structure on the affected side. This case report suggests the effectiveness of restoration of bone defects by using viable periodontal tissues around the impacted tooth for the longevity of the periodontium.

Wnt signaling regulates homeostasis of the periodontal ligament

BACKGROUND AND OBJECTIVE

In health, the periodontal ligament maintains a constant width throughout an organism's lifetime. The molecular signals responsible for maintaining homeostatic control over the periodontal ligament are unknown. The purpose of this study was to investigate the role of Wnt signaling in this process by removing an essential chaperone protein, Wntless (Wls), from odontoblasts and cementoblasts, and observing the effects of Wnt depletion on cells of the periodontal complex.

MATERIAL AND METHODS

The Wnt responsive status of the periodontal complex was assessed using two strains of Wnt reporter mice: Axin2(LacZ/+) and Lgr5(LacZ/+) . The function of this endogenous Wnt signal was evaluated by conditionally eliminating the Wntless (Wls) gene using an osteocalcin Cre driver. The resulting OCN-Cre;Wls (fl/fl) mice were examined using micro-computed tomography and histology, immunohistochemical analyses for osteopontin, Runx2 and fibromodulin, in-situ hybridization for osterix and alkaline phosphatase activity.

RESULTS

The adult periodontal ligament is Wnt responsive. Elimination of Wnt signaling in the periodontal complex of OCN-Cre;Wls(fl/fl) mice resulted in a wider periodontal ligament space. This pathologically increased periodontal width is caused by a reduction in the expression of osteogenic genes and proteins, which results in thinner alveolar bone. A concomitant increase in fibrous tissue occupying the periodontal space was observed, along with a disruption in the orientation of the periodontal ligament.

CONCLUSION

The periodontal ligament is a Wnt-dependent tissue. Cells in the periodontal complex are Wnt responsive, and eliminating an essential component of the Wnt signaling network leads to a pathological widening of the periodontal ligament space. Osteogenic stimuli are reduced, and a disorganized fibrillary matrix results from the depletion of Wnt signaling. Collectively, these data underscore the importance of Wnt signaling in homeostasis of the periodontal ligament.