Chidchanok Leethanakul

Vibratory stimulation increases interleukin-1 beta secretion during orthodontic tooth movement

OBJECTIVES To investigate the effects of application of vibratory stimuli on interleukin (IL)-1β secretion during maxillary canine distalization. MATERIALS AND METHODS Split-mouth design study in 15 subjects (mean age, 22.9 years; range 19-25 years) whose bilateral maxillary first premolars were extracted with subsequent canine distalization. On the experimental side, light force (60 g) was applied to the canine for 3 months in combination with vibratory stimuli provided using an electric toothbrush 15 minutes a day for 2 months; only orthodontic force was applied to the contralateral control canine. Gingival crevicular fluid (GCF) was collected from the mesial and distal sides of each canine at each monthly appointment. IL-1β levels were analyzed using an enzyme-linked immunosorbent assay. Canine movement was measured monthly. RESULTS Overall, enhanced IL-1β secretion was observed at the pressure sites of experimental canines compared to control canines (mean, 0.64 ± 0.33 pg/µL vs 0.10 ± 0.11 pg/µL, respectively, P < .001). The accumulative amount of tooth movement was greater for the experimental canine than for the control canine (mean, 2.85 ± 0.17 mm vs 1.77 ± 0.11 mm, respectively, P < .001). CONCLUSIONS This study demonstrates that, in combination with light orthodontic force, application of vibratory stimuli using an electric toothbrush enhanced the secretion of IL-1β in GCF and accelerated orthodontic tooth movement.

Interseptal bone reduction on the rate of maxillary canine retraction.

OBJECTIVE To propose and evaluate a novel surgical approach with minimal trauma, termed interseptal bone reduction, combined with the use of a conventional orthodontic fixed appliance to accelerate canine retraction. MATERIALS AND METHODS A split-mouth design study was conducted in 18 female subjects (mean age, 21.9 years) whose bilateral upper first premolars were extracted and who subsequently received canine distalization. The extraction socket on the experimental side was deepened, and interseptal bone distal to the maxillary canine was reduced in thickness using a surgical bur; conventional extraction was performed on the control side. The canines were then distalized using elastomeric chains on both the labial and palatal sides, with a net force of 150 g. The extent of canine movement and rotation was determined from study models, and the angulation was analyzed based on lateral cephalograms. RESULTS A Wilcoxon signed rank test demonstrated that the extent of canine movement in the mesio-distal direction after 3 months was significantly greater on the experimental side than on the control side (5.4 and 3.4 mm, respectively, P  =  .002). However, there was no statistically significant difference in canine angulation or rotation after 3 months between the experimental and control sides. CONCLUSIONS In combination with the use of conventional orthodontic appliances, interseptal bone reduction can enhance the rate of canine movement when interseptal bone is sufficiently reduced in both thickness and depth following surgical criteria.

Factors related to alveolar bone thickness during upper incisor retraction

OBJECTIVE To investigate the factors related to changes in alveolar bone thickness during upper incisor retraction. MATERIALS AND METHODS The subjects consisted of 23 ongoing orthodontic patients (mean age 20.4 ± 2.7 years) whose upper incisors were bound for retraction. Changes in alveolar bone thickness in the retracted area were assessed using preretraction (T0) and postretraction (T1) cone-beam computed tomography images. Labial bone thickness (LBT), palatal bone thickness (PBT), and total bone thickness (TBT) were assessed at the crestal, midroot, and apical levels of the retracted incisors. Paired t-tests were used to compare T0 and T1 bone thickness measurements. Spearmans rank correlation analysis was performed to determine the relationship of changes in alveolar bone thickness with the rate of tooth movement, change in inclination, initial alveolar bone thickness, and the extent of intrusion. RESULTS As the upper incisors were retracted, the LBT at the crestal level and TBT at the apical level significantly increased (P < .005). Changes in alveolar bone thickness were significantly associated with the rate of tooth movement, change in inclination, and extent of intrusion (P < .05) but not initial alveolar bone thickness (P > .05). CONCLUSION Rate of tooth movement, change in inclination, and extent of intrusion are significant factors that may influence alveolar bone thickness during upper incisor retraction. These factors must be carefully monitored to avoid the undesirable thickening of alveolar bone.

Epithelial Cells Secrete Interferon-γ Which Suppresses Expression of Receptor Activator of Nuclear Factor Kappa-B Ligand in Human Mandibular Osteoblast-Like Cells

BACKGROUND Prostaglandin (PG)E2 accumulates in inflamed periodontal tissue and induces receptor activator of nuclear factor kappa-B ligand (RANKL)-RANK-osteoprotegerin (OPG) signaling associated with bone resorption. Although oral epithelial cells maintain tissue homeostasis, the role of these cells in RANKL regulation remains unknown. METHODS To mimic an inflamed condition, RANKL upregulation in human mandibular osteoblast-like cells (HMOBs) were stimulated with PGE2. Effect of recombinant human interferon (IFN)-γ or epithelial-derived IFN-γ in constitutively released or Porphyromonas gingivalis lipopolysaccharide (PgLPS)-stimulated epithelial supernatant was investigated in HMOBs. Some HMOBs were pretreated with an anti-IFN-γ antibody before PGE2 stimulation. THP-1 human monocytes and HMOBs were cocultured in a transwell system to investigate RANKL-driven THP-1 osteoclastic activity. RESULTS PGE2 significantly increased RANKL messenger RNA (mRNA) and protein in HMOBs in a dose-dependent manner, while OPG protein remained similar to baseline. Epithelial cells constitutively released IFN-γ, which was substantially increased by PgLPS. HMOBs treated with epithelial supernatant or recombinant IFN-γ, concurrently with PGE2 stimulation, reduced RANKL, but not OPG, expression. In contrast, anti-IFN-γ antibody reversed the effect of epithelial mediators on RANKL expression. When cocultured with THP-1, RANKL released by PGE2-stimulated HMOBs is adequate to drive THP-1 differentiation as osteoclastogenic gene expression and bone resorption pit are increased. However, recombinant IFN-γ, or IFN-γ derived from oral epithelial cells, suppressed RANKL expression at both the mRNA and protein level, resulting in decreased THP-1-derived osteoclastic activity. CONCLUSION Oral epithelial cells interact with HMOBs by releasing IFN-γ to regulate RANKL expression and contribute to osteoclastogenesis.

Effects of low magnitude high frequency mechanical vibration combined with compressive force on human periodontal ligament cells in vitro

Objective Vibration can be used to accelerate tooth movement, though the exact mechanisms remain unclear. This study aimed to investigate the effects of low magnitude high frequency (LMHF) vibration combined with compressive force on periodontal ligament (PDL) cells in vitro. Materials and methods Human PDL cells were isolated from extracted premolar teeth of four individuals. To determine the optimal frequency for later used in combination with compressive force, three cycles of low-magnitude (0.3 g) vibrations at various frequencies (30, 60, or 90 Hz) were applied to PDL cells for 20 min every 24 h. To investigate the effects of vibration combined with compressive force, PDL cells were subjected to three cycles of optimal vibration frequency (V) or 1.5 g/cm2 compressive force for 48 h (C) or vibration combined with compressive force (VC). Cell viability was assessed using MTT assay. PGE2, soluble RANKL (sRANKL), and OPG production were quantified by ELISA. RANKL, OPG, and Runx2 expression were determined using real-time PCR. Results Cell viability was decreased in groups C and VC. PGE2 and RANKL, but not OPG, were increased in groups V, C, and VC, thus increasing the RANKL/OPG ratio. The highest level was observed in group VC. sRANKL was increased in groups V, C, and VC; however, no significant different between the experimental groups. Runx2 expression was reduced in groups C and VC. Conclusions Vibration increased PGE2, RANKL, and sRANKL, but not OPG and Runx2. Vibration had the additive effects on PGE2 and RANKL, but not sRANKL in compressed PDL cells.

Effects of Continuous and Interrupted Orthodontic Force on Interleukin-1β and Interleukin-8 Secretion in Human Gingival Crevicular Fluid

The purpose of this study was to compare levels of human IL-1β and IL-8 secretion during tooth movement using a nickel-titanium closed coil spring (NTCS) and an elastic c-chain (EC). Data were obtained from twenty healthy orthodontic patients treated with a pre-adjusted edgewise appliance with all first premolars extracted. In each subject, one maxillary canine received continuous force with a NTCS. The opposite maxillary canine received an interrupted force with an EC. Gingival crevicular fluid (GCF) was collected from distal sides of the canines before bracket placement, before canine retraction (baseline), at 24 hours, and at 1 and 2 months after canine retraction. IL-1β and IL-8 levels were measured. The amount of canine movement was measured from the models using the third palatal rugae as the reference point. IL-1β and IL-8 levels at each time point were compared to the baseline by analysis of variance (ANOVA) for repeated measures. A paired t-test was used to determine any significant differences of IL-1β and IL-8 levels between the groups at each time point and to compare the rate of canine movement between groups. The results demonstrated that IL-1β and IL-8 levels in both groups showed a significant elevation at 24 hours, and then declined. IL-1β and IL-8 levels in the NTCS group were significantly higher than the EC group at 24 hours, and 1 and 2 months after force application (p<0.001). The rate of canine retraction in the NTCS group was significantly higher than that of the EC group (p<0.001). In conclusion, the NTCS gave higher rate of canine retraction, which correlates with IL-1β and IL-8 levels.

The effect of compressive force combined with mechanical vibration on human alveolar bone osteoblasts

Objective This study aimed to investigate the effects of compressive force combined with mechanical vibration on the expression of pro-inflammatory cytokines that promote osteoclastogenesis and related to orthodontic tooth movement acceleration in human alveolar bone osteoblasts in vitro. Methods Osteoblasts were subjected to compressive force (C), mechanical vibration (V), compressive force combined with mechanical vibration (CV), or no force as a control for 12, 24 and 48 h. Interleukin-1 beta (IL-1β), interleukin-6 (IL-6), receptor activator of nuclear factor kappa-Β ligand (RANKL) and osteoprotegerin (OPG) mRNA and protein expression were assessed using quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assays. Results In C and CV groups, IL-1β and IL-6 mRNA and protein expression were significantly higher and OPG mRNA and protein expression were significantly lower than control and V groups. However, the expressions were not different between C and CV groups. RANKL mRNA and protein expression were not different between any groups. While, OPG mRNA and protein expression in V group were significantly higher than control group. Conclusions Vibration neither enhanced nor inhibited the expression of IL-1β, IL-6, RANKL and OPG in compressed human alveolar bone osteoblasts.

Comparison of clinical and histological characteristics of orthodontic tooth movement into recent and healed extraction sites combined with corticotomy in rats

Objective This study was performed to investigate the rate of tooth movement and histological characteristics of extraction sockets those were subjected to corticotomy. Methods A split-mouth randomized controlled trial experiment was designed. Thirty-two adult, male Wistar rats were divided into 2 groups: healing extraction socket (H) and recent extraction socket (R); these groups were randomly classified into 4 subgroups (0/7/21/60 days). The first maxillary molar was extracted on 1 side and 2 months were allowed for complete bone healing; then, the corresponding molar was extracted on the other side and surgical intervention was performed at the mid-alveolar point of the first maxillary molar. Ten grams of continuous force was applied. The outcomes measured were rate of tooth movement, percentage of periodontal space and histological evaluation. The rate of tooth movement was calculated as the measured distance divided by the duration of molar movement. Histomorphometric evaluations were performed on the second and third maxillary molars. The Wilcoxon signed rank test was used to compare differences between the two groups. Results There were no significant differences in the rates of tooth movement between H and R groups at any of the 4 time points. The histological appearance and percentage of periodontal space between the R and H groups also demonstrated no significant differences. Conclusions The rates of orthodontic tooth movement into recent and healed socket sites did not differ between the groups. Histological analysis of tooth movement revealed regional acceleration during every time period.

Iliac and mandible osteoblasts exhibit varied responses to LMHF vibration: Sites affect bone cell responses to vibration

The facial and long bones have distinct developmental origins, structures, and cellular compositions. This study aimed to compare the in vitro responses of human mandible and long bone osteoblasts to low‐magnitude, high‐frequency (LMHF) mechanical vibration in terms of expression of mediators of bone remodeling. Osteoblast‐like cell cultures were prepared from iliac crest and mandibular bone specimens from three individuals and cultured in osteogenic induction media. Induction of mature osteoblastic phenotypes was confirmed by analysis of DNA content, alkaline phosphatase activity and gene expression every 3 days for 27 days. Based on gene expression, mature osteoblasts formed by day 15 of induction culture. After 15 days of culture in induction media, mature osteoblasts were subjected to vibration (0, 30, or 60 Hz) for 30 min every 24 h. After 48 h, RANKL, OPG, IL‐1β, IL‐6 and TGF‐β gene, and protein expression were determined by real‐time PCR analysis of total cellular mRNA and ELISAs of the cell supernatants. Both iliac and mandible osteoblasts responded to LMHF vibration: IL‐1β and RANKL mRNA were downregulated and IL‐6 mRNA was upregulated. However, TGF‐ β mRNA was unaltered and OPG mRNA was upregulated in iliac osteoblasts, whereas both TGF‐β and OPG mRNA were downregulated in mandible osteoblasts. As a result, LMHF reduced the RANKL/OPG mRNA ratio in iliac osteoblasts but did not alter the RANKL/OPG mRNA ratio in mandible osteoblasts. This study suggests mature iliac osteoblasts exhibit a more potent anti‐resorptive response to vibration, while this tendency was not obviously apparent in mature mandible osteoblasts.

Volumetric evaluation of root resorption on the upper incisors using cone beam computed tomography after 1 year of orthodontic treatment in adult patients with marginal bone loss

OBJECTIVES: To determine upper incisor root resorption, volume loss, and the relationship between root volume loss and tooth movement after 1 year of orthodontic treatment in patients with marginal bone loss. MATERIALS AND METHODS: A total of 30 women (46.3 ± 5.4 years old) with moderate upper incisor bone loss who required intrusion during orthodontic treatment were recruited. Pre- and post-treatment cone beam computed tomography images were reconstructed. Upper incisors at pre- and post-treatment were superimposed; labio- and palato-apical, middle, and coronal third root volumes were assessed. Tooth movement and alveolar bone height were measured from lateral cephalometric radiographs and cone beam computed tomography. Changes in root volume/alveolar bone height were compared using paired-sample t-tests, percentage root volume loss for each tooth/segment was evaluated by one-way analysis of variance, and the relationship between percentage root loss and degree of tooth movement was assessed by linear regression. RESULTS: Mean root volume significantly decreased on the labio- and palato-apical aspects of 12 and labio-apical aspects of 21 and 22 ( P ≤ .024). Palato-apical segment volume loss was greater on lateral than central incisors ( P ≤ .016). Two-dimensional root length and cementoenamel junction-bone crest distance did not change between T0 and T1, with no significant relationship between tooth movement amount and percentage root volume loss. CONCLUSIONS: Delivery of 40 g intrusive force to the four upper incisors using a T-loop and the leveling phase lead to more apical root volume loss on lateral than central incisors. There was no relationship between extent of tooth movement and upper incisor root volume loss.