Dental, skeletal and soft tissue changes after bimaxillary protrusion treatment with temporary anchorage devices using different retraction mechanics.

BACKGROUND: Temporary anchorage devices (TADs), which are absolute anchorage, are used for retraction of the anterior teeth in cases of severe bimaxillary protrusion. There have been a number of studies regarding anterior tooth movement using TADs performed by simulation systems and actual treated materials with sliding mechanics. However, there are few studies regarding anterior tooth movement using TADs treated by loop mechanics The purpose of this study was to investigate the effect of TADs in anterior tooth movement using loop mechanics performed in actual cases of bimaxillary protrusion. METHODS: This study was performed in 20 adult patients with severe bimaxillary protrusion treated with four bicuspid extraction with sliding or loop mechanics (n = 10 in each mechanics) using TADs. The skeletal and denture patterns, as well as the soft tissue profile from pre-treatment (T0) and post-treatment (T1) lateral cephalograms, were compared between sliding and closing loop mechanics. RESULTS: The use of TADs is useful for retraction of anterior teeth without molar anchorage loss. in sliding and loop mechanics. The upper anterior teeth were less lingual tipped and lower anterior teeth were more upright resulting in less clockwise rotation of the occlusal plane in loop mechanics compared to sliding mechanics. CONCLUSION: An oblique retraction force vector with a lower point of application causes less intrusion and more lingual tipping of upper anterior teeth as well as more clockwise rotation of the occlusal plane compared to a parallel retraction force vector.

Continuous Compressive Force Induces Differentiation of Osteoclasts with High Levels of Inorganic Dissolution.

BACKGROUND Osteoclast precursor cells are constitutively differentiated into mature osteoclasts on bone tissues. We previously reported that the continuous stimulation of RAW264.7 precursor cells with compressive force induces the formation of multinucleated giant cells via receptor activator of nuclear factor kappaB (RANK)-RANK ligand (RANKL) signaling. Here, we examined the bone resorptive function of multinucleated osteoclasts induced by continuous compressive force. MATERIAL AND METHODS Cells were continuously stimulated with 0.3, 0.6, and 1.1 g/cm² compressive force created by increasing the amount of the culture solution in the presence of RANKL. Actin ring organization was evaluated by fluorescence microscopy. mRNA expression of genes encoding osteoclastic bone resorption-related enzymes was examined by quantitative real-time reverse transcription-polymerase chain reaction. Mineral resorption was evaluated using calcium phosphate-coated plates. RESULTS Multinucleated osteoclast-like cells with actin rings were observed for all three magnitudes of compressive force, and the area of actin rings increased as a function of the applied force. Carbonic anhydrase II expression as well as calcium elution from the calcium phosphate plate was markedly higher after stimulation with 0.6 and 1.1 g/cm² force than 0.3 g/cm². Matrix metalloproteinase-9 expression decreased and cathepsin K expression increased slightly by the continuous application of compressive force. CONCLUSIONS Our study demonstrated that multinucleated osteoclast-like cells induced by the stimulation of RAW264.7 cells with continuous compressive force exhibit high dissolution of the inorganic phase of bone by upregulating carbonic anhydrase II expression and actin ring formation. These findings improve our understanding of the role of mechanical load in bone remodeling.

Functional comparison of high and low molecular weight basic fibroblast growth factors.

Acid-electrolyzed functional water (FW) is obtained through the electrolysis of sodium chloride solution. Stimulation of the human fibroblastic cell line HeLa by FW led to the augmented secretion of basic fibroblast growth factor (bFGF). Immunoprecipitation followed by Western blot analysis revealed that both high and low molecular weight isoforms of bFGF were secreted in response to FW treatment. To explore intracellular bFGF localization, a cell fractionation assay was performed. Despite the presence of nuclear localization signals within the N-terminal portion of these proteins, the high molecular weight isoforms (34, 24, 22.5, and 21 kDa) were localized in the cytoplasm. FW stimulation drastically reduced the amount of intracytoplasmically localized isoforms, and the 34-kDa isoform was found to localize in a DNase-sensitive fraction, suggesting a weak nuclear attachment. By contrast, the 24-kDa isoform remained in the nucleus even after FW stimulation. Functional differences between the 34- and 18-kDa isoforms were examined further. Chinese hamster ovary cells were transfected with expression plasmids for each isoform. By treating each transfectant with FW, both isoforms were secreted successfully into the culture supernatants. Stimulation of HeLa cells with these supernatants resulted in the augmented secretion of vascular endothelial growth factor (VEGF). To further confirm the functionality of these isoforms, an in vitro transcription/translation reaction was performed; both of the isoforms induced VEGF secretion from HeLa cells. Taken together, these results indicate that the high molecular weight 34-kDa isoform and low molecular weight 18-kDa mature bFGF isoform have identical roles in VEGF induction.

PYK2 mediates BzATP-induced extracellular matrix proteins synthesis.

Mechanical stimuli such as fluid shear and cyclic tension force induced extracellular adenosine triphosphate (ATP) release in osteoblasts. In particular, cyclic tension force-induced ATP enhances bone formation through P2X7 activation. Proline-rich tyrosine kinase 2 (PYK2) mediate osteoblasts differentiation is induced by mechanical stimuli. Furthermore, activation of PYK2 also was a response to integrin by mechanical stimuli. Extracellular matrix protein (ECMP)s, which are important factors for bone formation are expressed by osteoblasts. However, the effect of the interaction of 2'(3)-Ο-(4-Benzoylbenzoyl) adenosine-5'-triphosphate (BzATP), which is the agonist of the mechanosensitive receptor P2X7, with PYK2 on ECMP production is poorly understood. Thus, our purpose was to investigate the effects of PYK2 on BzATP-induced ECMP production in osteoblasts. BzATP increased phospho-PYK2 protein expression on days 3 and 7 of culture. Furthermore, the PYK2 inhibitor PF431394 inhibited the stimulatory effect of BzATP on the expression of type I collagen, bone sialoprotein and osteocalcin expression. PF431396 did not inhibit the stimulatory effect of BzATP on osteopontin (OPN) mRNA expression. These results suggest that mechanical stimuli activate P2X7 might induce ECMPs expression through PYK2 except in the case of OPN expression. Altogether, mechanical stimuli-induced ECMPs production might be implicated by extracellular ATP secretion or integrin via PYK2 activation.

EMMPRIN Inhibits bFGF-Induced IL-6 Secretion in an Osteoblastic Cell Line, MC3T3-E1.

Background: Electrolytically-generated acid functional water (FW) is obtained by electrolyzing low concentrations of saline. Although it has been widely used in clinical practice with various purposes, the underlying mechanisms of action involved have not been fully elucidated so far. We used the human cervical cancer-derived fibroblastic cell line (HeLa), to examine the cytokine secretion profile following FW treatment in the present study. Results: FW stimulation significantly induced the secretion of basic fibroblast growth factor (bFGF) and extracellular matrix metalloproteinase inducer (EMMPRIN). The effect of both factors on osteoblast-like MC3T3-E1 cells was further examined by stimulating the cells with the conditioned medium of FW-stimulated HeLa cells. However, the conditioned medium failed to induce IL-6 secretion. The MC3T3-E1 cells were further stimulated with recombinant bFGF or EMMPRIN or a combination of both factors. Intriguingly, bFGF-stimulated IL-6 induction was totally inhibited by EMMPRIN. Pretreatment with the specific inhibitor of nuclear factor-kappa B (NF-κB) drastically inhibited IL-6 secretion indicating that bFGF-induced IL-6 expression was dependent on NF-κB activation. The phosphorylation status of NF-κB p65 subunit was further examined. The results indicated that EMMPRIN inhibited bFGF-induced NF-κB p65 phosphorylation. Conclusions: These findings suggest that bFGF can induce IL-6 secretion in MC3T3-E1 cells through NF-κB activation. As EMMPRIN inhibited bFGF-induced IL-6 secretion by reducing the p65 subunit phosphorylation, it might be concluded that bFGF and EMMPRIN crosstalk in their respective signaling pathways.

Connexin 43 contributes to ectopic orofacial pain following inferior alveolar nerve injury.

BACKGROUND: Clinically, it is well known that injury of mandibular nerve fiber induces persistent ectopic pain which can spread to a wide area of the orofacial region innervated by the uninjured trigeminal nerve branches. However, the exact mechanism of such persistent ectopic orofacial pain is not still known. The present study was undertaken to determine the role of connexin 43 in the trigeminal ganglion on mechanical hypersensitivity in rat whisker pad skin induced by inferior alveolar nerve injury. Here, we examined changes in orofacial mechanical sensitivity following inferior alveolar nerve injury. Furthermore, changes in connexin 43 expression in the trigeminal ganglion and its localization in the trigeminal ganglion were also examined. In addition, we investigated the functional significance of connexin 43 in relation to mechanical allodynia by using a selective gap junction blocker (Gap27). RESULTS: Long-lasting mechanical allodynia in the whisker pad skin and the upper eyelid skin, and activation of satellite glial cells in the trigeminal ganglion, were induced after inferior alveolar nerve injury. Connexin 43 was expressed in the activated satellite glial cells encircling trigeminal ganglion neurons innervating the whisker pad skin, and the connexin 43 protein expression was significantly increased after inferior alveolar nerve injury. Administration of Gap27 in the trigeminal ganglion significantly reduced satellite glial cell activation and mechanical hypersensitivity in the whisker pad skin. Moreover, the marked activation of satellite glial cells encircling trigeminal ganglion neurons innervating the whisker pad skin following inferior alveolar nerve injury implies that the satellite glial cell activation exerts a major influence on the excitability of nociceptive trigeminal ganglion neurons. CONCLUSIONS: These findings indicate that the propagation of satellite glial cell activation throughout the trigeminal ganglion via gap junctions, which are composed of connexin 43, plays a pivotal role in ectopic mechanical hypersensitivity in whisker pad skin following inferior alveolar nerve injury.

Alkaline phosphatase determines polyphosphate-induced mineralization in a cell-type independent manner.

Polyphosphate [Poly(P)] has positive effects on osteoblast mineralization; however, the underlying mechanism remains unclear. In addition, it is unknown whether Poly(P) promotes mineralization in soft tissues. We investigated this by using various cells. Poly(P) concentrations of 1 and 0.5 mg/mL yielded high levels of mineralization in ROS17/2.8 osteoblast cells. Similarly, Poly(P) induced mineralization in cell types expressing alkaline phosphatase (ALP), namely, ATDC5 and MC3T3-E1, but not in CHO, C3H10T1/2, C2C12, and 3T3-L1 cells. Furthermore, forced expression of ALP caused Poly(P)-induced mineralization in CHO cells. These results suggest that ALP determines Poly(P)-induced mineralization in a cell-type independent manner.

Low-intensity pulsed ultrasound accelerates nerve regeneration following inferior alveolar nerve transection in rats.

Inferior alveolar nerve (IAN) injury, which is frequently caused by orofacial surgery or trauma, induces sensory loss in orofacial regions innervated by the IAN. However, no effective treatment for orofacial sensory loss currently exists. We determined whether sensory loss in facial skin above the mental foramen following IAN transection was recovered by exposure of the transected IAN to low-intensity pulsed ultrasound (LIPUS). Inferior alveolar nerve transection (IANX) was performed in 7-wk-old male Sprague-Dawley rats. On day 7 after IANX, the effect of daily LIPUS (from day 0) on the transected IAN, in terms of sensitivity to mechanical stimulation of the facial skin above the mental foramen, was examined. Moreover, the number of trigeminal ganglion (TG) neurons innervating the facial skin above the mental foramen of rats with IANX treated daily with LIPUS was counted using the retrograde neurotracing technique. Daily exposure of the transected IAN to LIPUS significantly promoted recovery of the head-withdrawal threshold in response to mechanical stimulation of the facial skin above the mental foramen, and the number of TG neurons innervating the facial skin above mental foramen was significantly increased in rats with IANX treated daily with LIPUS compared with sham or LIPUS-unexposed rats. Daily treatment of stumps of the transected IAN with LIPUS facilitated morphological and functional regeneration, suggesting that LIPUS is an effective and novel therapy for IAN injury.

Are assessments of damping capacity and placement torque useful in estimating root proximity of orthodontic anchor screws?

INTRODUCTION: Placement torque and damping capacity may increase when the orthodontic anchor screws make contact with an adjacent root. If this is the case, root contact can be inferred from the placement torque and damping capacity. The purpose of this study was to verify the detectability of root proximity of the screws by placement torque and damping capacity. For this purpose, we investigated the relationship among placement torque, damping capacity, and screw-root proximity. METHODS: The placement torque, damping capacity, and root proximity of 202 screws (diameter, 1.6 mm; length, 8.0 mm) were evaluated in 110 patients (31 male, 79 female; mean age, 21.3 ± 6.9 years). Placement torque was measured using a digital torque tester, damping capacity was measured with a Periotest device (Medizintechnik Gulden, Modautal, Germany), and root contact was judged using cone-beam computed tomography images. RESULTS: The rate of root contact was 18.3%. Placement torque and damping capacity were 7.8 N·cm and 3.8, respectively. The placement torque of screws with root contact was greater than that of screws with no root contact (P <0.05; effect size, 0.44; power, <0.8). Damping capacity of screws with root contact was significantly greater than that of screws with no root contact (P <0.01; effect size, >0.5; power, >0.95). CONCLUSIONS: It was suggested that the damping capacity is related to root contact.

Tension force-induced ATP promotes osteogenesis through P2X7 receptor in osteoblasts.

Orthodontic tooth movement induces alveolar bone resorption and formation by mechanical stimuli. Force exerted on the traction side promotes bone formation. Adenosine triphosphate (ATP) is one of the key mediators that respond to bone cells by mechanical stimuli. However, the effect of tension force (TF)-induced ATP on osteogenesis is inadequately understood. Accordingly, we investigated the effect of TF on ATP production and osteogenesis in MC3T3-E1 cells. Cells were incubated in the presence or absence of P2X7 receptor antagonist A438079, and then stimulated with or without cyclic TF (6% or 18%) for a maximum of 24 h using Flexercell Strain Unit 3000. TF significantly increased extracellular ATP release compared to control. Six percent TF had maximum effect on ATP release compared to 18% TF and control. Six percent TF induced the expression of Runx2 and Osterix. Six percent TF also increased the expression of extracellular matrix proteins (ECMPs), ALP activity, and the calcium content in ECM. A438079 blocked the stimulatory effect of 6% TF on the expression of Runx2, Osterix and ECMPs, ALP activity, and calcium content in ECM. This study indicated that TF-induced extracellular ATP is released in osteoblasts, suggesting that TF-induced ATP promotes osteogenesis by autocrine action through P2X7 receptor in osteoblasts.

Osteocytes up-regulate the terminal differentiation of pre-osteoblasts via gap junctions.

We examined cell-to-cell interaction between pre-osteoblasts and osteocytes using MC3T3-E1 and MLO-Y4, respectively. First, GFP expressing MC3T3-E1 (E1-GFP) cells were generated to isolate the cells from co-culture with MLO-Y4. No changes were observed in the expression of osteogenic transcription factors Runx2, Osterix, Dlx5 and Msx2, but expression of alkaline phosphatase (ALP) and bone sialoprotein (BSP) in E1-GFP co-cultured with MLO-Y4 was 300-400-fold greater than that in mono-cultured E1-GFP. In addition, mineralized nodule formation was drastically increased in co-cultured E1-GFP cells compared to mono-cultured cells. Patch clamp assay showed the presence of gap junctions between E1-GFP and MLO-Y4. Furthermore, when the gap junction inhibitor carbenoxolone (CBX) was added to the culture, increased expression of ALP and BSP in E1-GFP co-cultured with MLO-Y4 was suppressed. These results suggest that gap junction detected between pre-osteoblasts and osteocytes plays an important role on the terminal differentiation of pre-osteoblasts.

Cancer cell-derived IL-8 induces monocytic THP1 cells to secrete IL-8 via the mitogen-activated protein kinase pathway.

Aberrant activity of transcription factors in oral squamous cell carcinoma (OSCC) results in the spontaneous secretion of various cytokines and chemokines. Among them, IL-8, owing to its angiogenic activity, promotes the growth of OSCCs. In the present study, we examined the role of IL-8 secreted by OSCCs, on the angiogenic activity of monocytic THP1 cells. Culture supernatant (Ca-sup) augmented IL-8 secretion by THP1 cells, which was found to be significantly reduced following the removal Ca9-22-derived IL-8 from the Ca-sup. IL-8 induction was regulated at the transcriptional level, because real-time PCR demonstrated the augmented IL-8 messenger RNA (mRNA) expression. We further performed the luciferase assay using the 5'-untranslated region of IL-8 gene. Contradictory to our speculations, luciferase activity was not augmented by Ca-sup stimulation. NF-κB-independent IL-8 induction was further confirmed by pre-treating THP1 cells with NF-κB-specific inhibitors. To elucidate the signaling pathway, THP1 was pre-treated with MEK inhibitors. The results demonstrated that pre-treatment of cells with MEK inhibitor drastically reduced IL-8 levels, suggesting the role of MEK. Moreover, Ca-sup was found to increase ERK1/2 phosphorylation in a time-dependent manner. These results indicated that OSCC-derived IL-8 appears to activate angiogenic activity in monocytes within the tumor microenvironment via the mitogen-activated protein kinase (MAPK) pathway.

High-magnitude mechanical strain inhibits the differentiation of bone-forming rat calvarial progenitor cells.

PURPOSE: Orthodontic tooth movement occurs during the bone remodeling induced by therapeutic mechanical strain. It is important to investigate the relation between the strength of mechanical stress and bone formation activity. The aim of this study was to determine the effect of high-magnitude mechanical strain on bone formation in detail. MATERIALS AND METHODS: Osteoblast-like cells isolated from fetal rat calvariae were loaded with 18% cyclic tension force (TF) for 48 h. To phenotypically investigate the effect of TF, we measured the number and the size of bone nodules stained by von Kossa technique on day 21 after cell seeding and determined the calcium content of bone nodules on day 14. Furthermore, we examined the gene expression of BMP-2, Runx2 and Msx2, which are important factors for bone nodule formation, on days 1, 4 and 7 after TF loading. RESULTS: The maximum bone nodule size in the control group was 1620 and 719 µm in the TF group. Furthermore, the mean number of bone nodules sized over 360 µm in the TF group was significantly decreased compared to the control group. The calcium content was also significantly decreased to 42% by TF loading. The mRNA expression of BMP-2, Runx2 and Msx2 was decreased 1 and 4 days after TF loading. CONCLUSION: The differentiation of bone forming progenitor cells into bone nodule forming cells was inhibited by TF due to the decreased expression of bone formation related factors such as BMP-2, Runx2 and Msx2.

Simultaneous activation of the α1A-, α1B- and α1D-adrenoceptor subtypes in the nucleus accumbens reduces accumbal dopamine efflux in freely moving rats.

Intra-accumbal infusion of the α1-adrenergic agonist methoxamine, which has comparable affinity for α1A-, α1B- and α1D-adrenoceptor subtypes, fails to alter noradrenaline efflux but reduces dopamine efflux in the nucleus accumbens of rats. In-vivo microdialysis experiments were carried out to analyse the putative contribution of α1A-, α1B- and α1D-adrenoceptor subtypes to the methoxamine-induced decrease in accumbal dopamine efflux in freely moving rats. The drugs used were dissolved in the infusion medium and administered locally through a dialysis membrane. Intra-accumbal infusions of the α1A-adrenoceptor antagonist 5-methylurapidil (6 pmol), the α1B-adrenoceptor antagonist cyclazosin (0.6 and 6 pmol) and the α1D-adrenoceptor antagonist BMY 7378 (0.6 pmol) did not alter accumbal efflux of noradrenaline or dopamine: pretreatment with each of these α1-adrenoceptor subtype-selective antagonists counteracted the methoxamine (24 pmol)-induced decrease in accumbal dopamine efflux. Doses indicated are the total amount of drug administered over a 60-min infusion period. These results clearly suggest that the α1A-, α1B- and α1D-adrenoceptor subtypes in the nucleus accumbens mediate the α1-adrenergic agonist methoxamine-induced decrease in accumbal dopamine efflux. The present study also provides in-vivo neurochemical evidence indicating that concomitant, but not separate, activation of the α1A-, α1B- and α1D-adrenoceptors in the nucleus accumbens is required for α1-adrenergic inhibition of accumbal dopaminergic activity.

Tension Force Downregulates Matrix Metalloproteinase Expression and Upregulates the Expression of Their Inhibitors through MAPK Signaling Pathways in MC3T3-E1 cells.

OBJECTIVE: Matrix metalloproteinases (MMPs), produced by osteoblasts, catalyze the turnover of extracellular matrix (ECM) molecules in osteoid, and the regulation of MMP activity depends on interactions between MMPs and tissue inhibitors of metalloproteinases (TIMPs). We focused on the degradation process of ECM in osteoid that was exposed to mechanical strain, and conducted an in vitro study using MC3T3-E1 osteoblastic cells to examine the effects of tension force (TF) on the expression of MMPs and TIMPs, and activation of mitogen-activated protein kinase (MAPK) pathways. DESIGN: Cells were incubated on flexible-bottomed culture plates and stimulated with or without cyclic TF for 24 hours. The expression of MMPs and TIMPs was examined at mRNA and protein levels by real-time RT-PCR and Western blotting, respectively. The phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, p38 MAPK, and stress-activated protein kinases/c-jun N-terminal kinases (SAPK/JNK) were examined by Western blotting. RESULTS: TF decreased the expression of MMP-1, -3, -13 and phosphorylated ERK1/2. In contrast, TF increased the expression of TIMP-2, -3 and phosphorylated SAPK/JNK. The expression of MMP-2, -14, TIMP-1, -4 and phosphorylated p38 MAPK was unaffected by TF. MMP-1, -3 and -13 expression decreased in cells treated with the ERK inhibitor PD98059 compared with untreated control cells. The JNK inhibitor SP600125 inhibited the TF-induced upregulation of TIMP-2 and -3. CONCLUSIONS: The results suggest that TF suppresses the degradation process that occurs during ECM turnover in osteoid via decreased production of MMP-1, -3 and -13, and increased production of TIMP-2 and -3 through the MAPK signaling pathways in osteoblasts.

The P75 neurotrophin receptor regulates proliferation of the human MG63 osteoblast cell line.

The 75 kDa transmembrane protein, p75(NTR), is a marker of mesenchymal stem cells (MSCs). Isolated MSCs are capable of differentiating into osteoblasts, but the molecular function of p75(NTR) in MSCs and osteoblasts is poorly understood. The aim of this study was to examine the function of p75(NTR) in the human MG63 osteoblast cell line compared to the murine MC3T3E-1 pre-osteoblast cell line. MG63 cells and MC3T3-E1 cells expressing exogenous p75(NTR) protein (denoted as p75-MG63 and p75GFP-E1, respectively) were generated to compare osteogenic differentiation and cell proliferation abilities. Overexpression of p75(NTR) induced alkaline phosphatase activity and the mRNA expression of osteoblast-related genes such as osterix and bone sialoprotein in both p75-MG63 and p75GFP-E1. Interestingly, exogenous p75(NTR) stimulated cell proliferation and cell cycle progression in p75GFP-E1, but not in p75-MG63. To elucidate any different effects of p75(NTR) expression on osteogenic differentiation and cell proliferation, we examined the mRNA expression of tropomyosin receptor kinase (trk) genes (trkA, trkB, trkC) and Nogo receptor (NgR), which are binding partners of p75(NTR). Although trkA, trkB, and trkC were detected in both p75-MG63 and p75GFP-E1, only NgR was detected in p75-MG63. We then used the K252a inhibitor of the trks to identify the signaling pathway for osteogenic differentiation and cell proliferation. Inhibition of trks by K252a suppressed p75(NTR)-mediated osteogenic differentiation of p75GFP-E1, whereas deletion of the GDI domain in P75(NTR) from the p75-MG63 produced enhanced cell proliferation compared to p75-MG63. These results suggest that p75(NTR) signaling associated with trk receptors promotes both cell proliferation and osteoblast differentiation, but that p75(NTR)-mediated proliferation may be suppressed by signaling from the p75(NTR)/NgR complex.

CO2 laser debonding of a ceramic bracket bonded with orthodontic adhesive containing thermal expansion microcapsules.

We have been studying an easy bracket debonding method using heating of an orthodontic adhesive containing thermal expansion microcapsules. However, heating with a high-temperature heater brings obvious risks of burns around the oral cavity. Thus, we examined safer and more effective bracket debonding methods. The purpose of this in vitro study was to examine the reduction in debonding strength and the time taken using a bracket bonded with an orthodontic adhesive containing thermal expansion microcapsules and a CO2 laser as the heating method while maintaining safety. Ceramic brackets were bonded to bovine permanent mandibular incisors using bonding materials containing various microcapsule contents (0, 30, and 40 wt%), and the bond strengths were measured after laser irradiation for 4, 5, and 6 s and compared with nonlaser-treated groups. Subsequently, the temperature in the pulp chamber during laser irradiation was measured. After laser irradiation for 5 or 6 s, the bond strengths of the adhesive containing 40 wt% microcapsules were significantly decreased to ∼0.40 - 0.48-fold (4.6-5.5 MPa) compared with the nonlaser groups. The mean temperature rise of the pulp chamber was 4.3 °C with laser irradiation for 6 s, which was less than that required to induce pulp damage. Based on these results, we conclude that the combined use of a CO2 laser and an orthodontic adhesive containing thermal expansion microcapsules can be effective and safe for debonding ceramic brackets with less enamel damage or tooth pain.

Effects of tooth root contact on the stability of orthodontic anchor screws in the maxilla: Comparison between self-drilling and self-tapping methods.

INTRODUCTION: We evaluated the effects of screw placement angle on the frequency of root contact and the effects of root contact on screw stability, comparing self-drilling and self-tapping methods. METHODS: In total, 80 patients with 142 screws (diameter, 1.6 mm; length, 8.0 mm) were included. Cone-beam computed tomography images were taken. Cortical bone thickness, interroot distance, shortest distance between the screw and adjacent tooth root, and screw placement angle were measured. RESULTS: The success rates of the screws were 91.5% for the self-drilling method and 94.4% for the self-tapping method (P >0.05). The self-drilling screws tended to contact the distal tooth roots in the right maxilla. In the self-drilling method, the failure rate was significantly higher in the root contact group than in the no-contact group (P <0.05). CONCLUSIONS: The success rate was not significantly different between the self-drilling and the self-tapping methods in the maxilla. Avoidance of tooth root contact may improve the success rate more in the self-drilling method than in the self-tapping method.

Satisfaction with orthognathic surgery of skeletal Class III patients.

INTRODUCTION: Class III relationships can be corrected with single-jaw or bimaxillary surgery. The purpose of this research was to assess patient satisfaction after bimaxillary surgery, compared with setback surgery alone, for Class III corrections. Identifying patients' relative levels of satisfaction will provide guidance for the selection of surgical options. METHODS: The cephalometric outcomes for 25 patients who underwent 2-jaw surgery were compared with the outcomes in 40 patients who had mandibular setback. Soft and hard tissue changes were evaluated using initial and postsurgical lateral cephalograms. The patients were asked to complete self-administered questionnaires after orthognathic treatment. Correlations between cephalometric improvement and patient satisfaction were evaluated. RESULTS: The patients in the 2-jaw group reported significantly higher satisfaction in the appearance of the mouth (P <0.05), smile (P <0.05), and treatment outcome (P <0.001). These item scores and the changes in ANB, ANS-M, and nasolabial angle showed strong correlations in the 2-jaw group and moderate correlations in the 1-jaw group. CONCLUSIONS: ANS-M and nasolabial angle should be considered in the conventional diagnosis of skeletal Class III orthognathic surgery to obtain adequate correction of facial esthetics and patient satisfaction. Esthetic needs contribute to surgical decisions when treating patients with skeletal Class III malocclusions and dentofacial deformities such as maxillary deficiency and long facial height that causes a turned-up upper lip.

Effects of palate depth, modified arm shape, and anchor screw on rapid maxillary expansion: a finite element analysis.

OBJECTIVES: This study examined the effects of palate depth, modifications of the arm shape, and anchor screw placement in the mid-palatal area on rapid maxillary expansion (RME) using finite element (FE) analysis. MATERIALS AND METHODS: Three-dimensional FE models were constructed that included the maxilla (cortical and cancellous bone), maxillary sinus, maxillary first molar and first premolar, periodontal membrane, and an RME appliance with arms, bands, and anchor screws. The expansion screws were activated 0.2mm transversely. RESULTS: The deepest palate model had the smallest lateral displacement of the tooth and expansion of the mid-palatal suture and the greatest strain of the arm among the models with different palate heights. The model with a larger diameter arm had the smallest arm strain among the models with various arm shapes. The model with an anchor screw had the greatest lateral displacement of the tooth and expansion of the mid-palatal suture among all models. CONCLUSIONS: For a deeper palate, the arm strain increased and the effect of RME decreased. Modified arm shapes such as a larger diameter arm, arms connected by a diagonal wire, a straight arm, and a shorter arm efficiently expanded the maxillary dental arch. Anchor screws increased the effect of RME, generated more and closer bodily movement of the tooth, and parallel expansion of the mid-palatal suture. The model with an anchor screw without arms decreased the displacement of the teeth compared to the models with arms, so the arms are necessary for effective RME.