Comparison of a magnetic treatment system combined with miniscrews and a conventional NiTi spring for tooth movement and bone formation: A Beagle model study.

Bone remodeling is mediated by the interaction between osteoblasts and osteoclasts, so does osteoinduction triggered by calcium phosphate (CaP) biomaterials. This study aims to investigate the role and function of osteoclasts in ectopic bone formation induced by CaP biomaterials. Four kinds of mice, two outbred mouse strains (KM and ICR) and two inbred mouse strains (C57BL/6 and BALB/c), were chosen for the experiments. The hydroxyapatite/𝛽-tricalcium phosphate (HA/𝛽-TCP) biomaterials were implanted into the bilateral thigh muscle of each mouse, and then all mice ran on the treadmill to accelerate the ectopic bone formation. Five and ten weeks later, five mice in each group were euthanized and the samples were harvested for electron microscope scanning or histological identification: hematoxylin and eosin (HE), Masson-trichrome and tartrate-resistant acid phosphatase (TRAP) staining, respectively. The inflammation indexes, angiogenesis, and osteogenic ability were compared among the four kinds of mice, and the role of osteoclasts was analyzed based on this evidence. The number of multinucleated cells, the number of new blood vessels, and the area percentage of new bone tissues were higher in outbred mouse strains than in inbred mouse strains; and there were more TRAP-positive cells in the outbred mouse strains group. We believe that the monocytes from the peripheral blood could migrate into new bone tissues to form osteoclasts. Bone induction could be triggered by CaP biomaterials in mice, and osteoclasts could maintain the dynamic balance between bone resorption and remodeling, and induce the production of new bone marrow tissues.

ObjectiveThis study aimed to evaluate the effect of an intentionally created socket on bone remodeling with orthodontic tooth movement in rabbits.MethodsEighteen male rabbits weighing 3.8 - 4.25 kg were used. An 8-mm deep and 2-mm wide socket was drilled in the bone 1 mm mesial to the right mandibular first premolar. The left first premolar was extracted to serve as an extraction socket. A traction force of 100 cN was applied to the right first premolar and left second premolar. Sections were obtained at the middle third of the moving tooth for both the drilled and extraction sockets and evaluated with hematoxylin and eosin staining and immunohistochemical analyses. The amount of tooth movement and tartrate-resistant acid phosphatase (TRAP)-positive cell count were compared between the 2 groups using the Mann-Whitney U test.ResultsAt week 2, the distance of tooth movement was significantly higher in the intentional socket group (p < 0.05) than in the extraction socket group. The number of TRAP-positive cells decreased in week 2 but increased in week 3 (p < 0.05). However, there were no significant differences between the groups. Furthermore, results of transforming growth factor (TGF)-β staining revealed no significant differences.ConclusionsThe intentional socket group showed greater distance of tooth movement than did the extraction socket group at week 2. Osteoclast counts and results of immunohistochemical analyses suggested elevated bone remodeling in both the groups. Thus, osteotomy may be an effective modality for enhancing tooth movement in orthodontic treatment.

Tooth movement is a biological process of bone remodeling induced by mechanical force. Sclerostin secreted by osteocytes is mechanosensory and important in bone remodeling. However, little is known regarding the role of sclerostin in tooth movement. In this study, models of experimental tooth movement were established in rats and mice. Sclerostin expression was investigated with immunohistochemistry staining, and osteoclastic activity was analyzed with tartrate-resistant acid phosphatase (TRAP) staining. MLO-Y4 osteocyte-like cells underwent uniaxial compression and tension stress or were cultured in hypoxia conditions. Expression of sclerostin was assessed by RT-qPCR and ELISA. MLO-Y4 cells were cultured with recombinant human sclerostin (rhSCL) interference and then co-cultured with RAW264.7 osteoclast precursor cells. Expressions of RANKL and OPG were analyzed by RT-qPCR, and osteoclastic activity was assessed by TRAP staining. During tooth movement, sclerostin was expressed differently in compression and tension sites. In SOST knock-out mice, there were significantly fewer TRAP-positive cells than in WT mice during tooth movement in compression sites. In-vitro studies showed that the expression of sclerostin in MLO-Y4 osteocyte-like cells was not different under a uniaxial compression and tension force, whereas hypoxia conditions significantly increased sclerostin expression in MLO-Y4 cells. rhSCL interference increased the expression of RANKL and the RANKL/OPG ratio in MLO-Y4 cells and the osteoclastic induction ability of MLO-Y4 cells in experimental osteocyte-osteoclast co-culture. These data suggest that sclerostin plays an important role in the bone remodeling of tooth movement.

This study investigated specific activities of tartrate resistant acid phosphatase (TRAP) in gingival crevicular fluid (GCF) and cumulative canine movement when two orthodontic forces were applied during orthodontic treatment. Each selected subjects (n = 12) randomly received a 100 and 150 g force for canine retraction either on the right or left site of maxillary arch. GCF was collected at the mesial and distal sites of the canines for 5 consecutive weeks where baseline activity served as control. Canine distance was measured before retraction and weekly (5 weeks) after force application. TRAP activity was determined using spectrophotometer. At the distal site of test canine (150 g force), TRAP activity peaked significantly (P 0.05) TRAP activities were found between 150 and 100 g of forces. There was significantly (P < 0.05) more cumulative canine movement by 5 weeks in 150 g as compared to 100 g force. TRAP enzyme can be a useful biomarker for monitoring orthodontic tooth movement. A force of 150 g was found to be more optimal in canine retraction than 100 g force. Key words: Biomarker, bone remodeling, orthodontic forces, tartrate resistant acid phosphatase, tooth movement.

The porpose of this study was to determine the optimal length of power arms for achieving controlled anterior tooth movement in segmented arch mechanics combined with power arm. A three-dimensional finite element method was applied for the simulation of en masse anterior tooth retraction in segmented power arm mechanics. The type of tooth movement, namely, the location of center of rotation of the maxillary central incisor in association with power arm length, was calculated after the retraction force was applied. When a 0.017 × 0.022-in archwire was inserted into the 0.018-in slot bracket, bodily movement was obtained at 9.1 mm length of power arm, namely, at the level of 1.8 mm above the center of resistance. In case a 0.018 × 0.025-in full-size archwire was used, bodily movement of the tooth was produced at the power arm length of 7.0 mm, namely, at the level of 0.3 mm below the center of resistance. Segmented arch mechanics required shorter length of power arms for achieving any type of controlled anterior tooth movement as compared to sliding mechanics. Therefore, this space closing mechanics could be widely applied even for the patients whose gingivobuccal fold is shallow. The segmented arch mechanics combined with power arm could provide higher amount of moment-to-force ratio sufficient for controlled anterior tooth movement without generating friction, and vertical forces when applying retraction force parallel to the occlusal plane. It is, therefore, considered that the segmented power arm mechanics has a simple appliance design and allows more efficient and controllable tooth movement.

Residents’ journal review

Low-intensity pulsed ultrasound enhances the rate of lateral tooth movement and compensatory bone formation in rats

To investigate the accuracy and reliability of cone beam computed tomography (CBCT) measurements of buccal alveolar bone height (BBH) and thickness (BBT) using custom acquisition settings. School of Dentistry, Oregon Health & Science University. Twelve embalmed cadavers. Cadaver heads were imaged by CBCT (i-CAT® 17-19, Imaging Sciences International, Hatfield, PA) using a 'long scan' (LS) setting with 619 projection images, 360° revolution, 26.9 s duration, and 0.2 mm voxel size, and using a 'short scan' (SS) setting with 169 projection images, 180° rotation, 4.8 s duration, and 0.3 mm voxel size. BBH and BBT were measured with 65 teeth, indirectly from CBCT images and directly through dissection. Comparisons were assessed using paired t-tests (p≤0.05). Level of agreement was assessed by concordance correlation coefficients, Pearson's correlation coefficients, and Bland-Altman plots. Mean differences in measurements compared to direct measurements were as follows, LS 0.17±0.12 (BBH) and 0.10±0.07 mm (BBT), and SS 0.41±0.32 (BBH) and 0.12±0.11 mm (BBT). No statistical differences were found with any of BBH or BBT measurements. Correlation coefficients and Bland-Altman plots showed agreement was high between direct and indirect measurement methods, although agreement was stronger for measurements of BBH than BBT. Compared to the LS, the similarity in results with the reduced scan times and hence reduced effective radiation dose, favors use of shorter scans, unless other purposes for higher resolution imaging can be defined.

Residents' journal review

Assessing accelerated tooth movement techniques on their own catabolic merits: a review

BackgroundAt present, specific immune targeted therapeutics including biologics and kinase inhibitors has made significant progress in Rheumatoid arthritis (RA). However, the irresponse to targeted therapies in some refractory RA patients...

Material-induced osteoinduction is reported in comparatively large animals such as dogs and pigs; however, it does not often occur in small animals such as rodents. In this study, we implanted porous calcium-deficient hydroxyapatite (CDHA) in the dorsal muscles of dogs and rats and compared the two species, with emphasis on multinucleated cells, by using hematoxylin and eosin (HE) staining, tartrate-resistant acid phosphatase (TRAP) staining, transmission electron microscope (TEM) observation, and reverse transcription-polymerase chain reaction (RT-PCR). In CDHA extracted from dogs, numerous TRAP-positive multinucleated cells were detected after 2 weeks and new bone formation was observed after 4 weeks. In contrast, in rats, only a small number of TRAP-positive cells were detected and no bone formation was observed within 6 weeks. CDHA was more degraded in dogs than in rats. TEM observation of the multinucleated cells in CDHA extracted from dogs after 3 weeks revealed osteoclast-like features such as ruffled borders. However, CDHA extracted from rats did not exhibit osteoclast-like features. RT-PCR evaluation showed that the expression of cathepsin K was higher in dogs than in rats. These results indicate that TRAP-positive cells might be one of the main factors responsible for the cross-species difference in material-induced osteoinduction.

Genetic Factors and Tooth Movement

The tooth movement in the alveolus is possible due to bone remodeling. This process could be the risk factor for the formation of gingival recessions—the most common side effects of orthodontic therapy. Gingival recessions are found 5.8–11.5% more frequently among the orthodontically treated patients. What is more, anterior mandibular teeth are the ones most prone to gingival recession dehiscences and fenestrations. The aim of this narrative review was to evaluate, based on CBCT (Cone beam computed tomography) scans, the changes in the alveolar bone of lower incisors in adolescent and adult patients after orthodontic tooth movements. From the pool of 108 publications, a total of 15 fulfilled the criteria of this review. Both retrospective and prospective longitudinal studies—using CBCT or CT (Computed Topography) and evaluating alveolar bone changes in mandibular incisors during orthodontic treatment performed before and after teeth movement—were included. In the group of growing patients, either proclination or retroclination of mandibular incisors led to increase of the distance from CEJ (cementoenamel junction) to marginal bone crest. The difference in bone loss was greater on the lingual side of the incisors in both types of tooth movement. The results were similar for adults patients. The thickness of the alveolar bone was reduced after proclination (total bone thickness) among growing and non-growing patients and retraction (lingual and buccal) of lower anterior teeth in the group of growing patients. The only improvement was measured for buccal thickness of mandibular incisor in bimaxillary protrusion patients treated with extraction therapy. The control of retraction movement (more root than crown movement) enhanced preservation on bone height and thickness. In order to minimize possible deterioration and place teeth in the center of alveolus, CBCT monitoring and scrupulous clinical evaluation are recommended.

Objective. The aim of this study was to investigate the effects of estrogen deficiency on tooth movement in ovariectomized rats. Material and methods. Forty-two adult female Sprague-Dawley rats were assigned at random to one of the following groups: test group (n=20), ovariectomized rats (or estrogen-deficient rats); control group (n=22), non-ovariectomized rats. Two months after ovariectomy, expansion springs exerting 10 g of force were inserted between the upper central incisors in both groups. The amount of movement was measured daily until tooth movement began and then at intervals of 3 days. The rats were sacrificed 18 days after applying the expansion spring and histomorphometric analysis was performed along the left upper central incisor root towards the apex of the alveolar bone. Results. The amount and speed of movement was observed to be greater in ovariectomized rats. On histomorphometric analysis, osteoblast and osteocyte counts on the pressure side were higher in the non-ovariectomized group than in the ovariectomized group (p<0.001). In contrast, the osteoclast count was significantly higher (p <0.01) in the ovariectomized group than in the non-ovariectomized group. The osteoblast and osteocyte counts were significantly higher (p <0.001) on tension side in the non-ovariectomized group than in the ovariectomized group. Conclusion. Estrogen deficiency increased orthodontic tooth movements but counts of osteoblasts, which are responsible for new bone formation, were lower in regions of tension and of pressure.