Strategic treatment planning for anterior open bite: A comprehensive approach.

Anterior open bite (AOB), characterized by the lack of vertical overlap between upper and lower anterior teeth, poses a considerable challenge in orthodontics. The condition depends on many factors that combine to render it difficult to achieve post treatment stability. AOB is commonly classified as dental, skeletal, or functional on the basis of the clinical presentation and causative factors. Traditionally, skeletal AOB necessitates surgical intervention, whereas nonsurgical approaches such as extrusion arches and the Multiloop Edgewise Archwire Technique (MEAW) can be employed in more straightforward cases. Functional appliances are reserved for situations in which a patient's growth potential offers the possibility of effectively addressing AOB. This review presents a strategic treatment approach for addressing AOB, taking into account the classification and severity of the condition. The proposed SHE framework describes the use of mini-screws (S) for anchorage and vertical control, encouragement to correct habits (H), and the utilization of extractions and elastics (E). By incorporating extra-radicular mini-screws, AOB closure is achieved through anterior retraction in extraction cases or whole arch distalization of dentition with elastics in non-extraction cases. This framework emphasizes habit correction through a regimen of oral myofunctional therapy (OMT) and habit-correcting appliances to enhance posttreatment stability. This review suggests that nonsurgical correction is viable in the majority of cases, whereas surgical intervention should be reserved for severe cases of skeletal vertical overgrowth or horizontal discrepancies.

Effectiveness of Clear Aligners on Sequential Maxillary Molar Distalization: Discrepancy between Treatment Goal and Outcome.

Objectives: The purpose of this preliminary study was to determine the differences between planned and actual maxillary molar movements after the completion of treatment with an initial set of clear aligners including sequential maxillary molar distalization. Methods: The data records of 14 non-growing patients who completed orthodontic treatment with sequential maxillary molar distalization using clear aligners were retrospectively evaluated (n= 14, 4 males and 10 females, 33.61 ± 8.57 years). Data on planned tooth movements were obtained from ClinCheck software (ClinCheck Pro version 5.3). The amounts of actual tooth movements were obtained by performing superimposition of lateral cephalograms taken before and after treatment. The amounts of distal translation and tipping between planned and actual maxillary molar movements were compared with the paired Student's t-test. Results: The statistically significant differences between planned and actual translation movements of maxillary first and second molars were shown after completing treatment with the first series of aligners (p < 0.05). The average actual amount of molar distalization on maxillary first molars was less than the planned amount by 1.32 ± 0.42 mm. Similarly, the average actual amount of molar distalization on maxillary second molars was less than the planned amount by 1.57 ± 0.45 mm. The accuracy for molar distalization, namely, the percentage of actual distal translation to planned movement, was 40.11% for maxillary first molars and 35.39% for maxillary second molars. However, the difference between the planned and actual angulation movements was not significant (p > 0.05). Conslusions: In conclusion, the amounts of actual distal translation of maxillary molars through the utilization of clear aligners were significantly lower than planned. However, there were no statistically significant differences between the degrees of actual and planned molar angulation movement.

Shear Bond Strength of Clear Aligner Attachment Using 4-META/MMA-TBB Resin Cement on Glazed Monolithic Zirconia.

Increasing demand for adult orthodontic treatment using clear aligners has highlighted challenges in bonding clear aligner attachments to various restorations. Specifically, the bond strength of clear aligner attachments to glazed monolithic zirconia has not been extensively studied. This study aims to compare the shear bond strength (SBS) and mode of failure (MOF) of conventional bonding methods versus Superbond C&B (4-META/MMA-TBB resin cement) for clear aligner attachments on glazed monolithic zirconia. Fifty sintered and glazed zirconia samples were divided into five groups and attached with clear aligner attachments: Si (silane), B (bonding agent), SiB (bonding agent and silane), SU (Superbond C&B), and SiSU (silane and Superbond C&B). SBS and MOF of these samples were analyzed. Results indicated a significant difference in bond strength among the groups. SiSU exhibited the highest bond strength, followed by SU, while B had the lowest bond strength. SEM analysis revealed that SiSU and SU predominantly exhibited mixed failure, indicating high bond strength without affecting the glazed layers of the zirconia. In contrast, B exhibited only adhesive failure at the interface, resulting in insufficient bond strength for effective orthodontic treatment. In conclusion, using 4-META/MMA-TBB resin cement provides high bond strength for clear aligner attachments on glazed zirconia with minimal material damage during debonding.

Relationship between Cephalometric and Ultrasonic Airway Parameters in Adults with High Risk of Obstructive Sleep Apnea.

Background/Objectives: Polysomnography and cephalometry have been used for studying obstructive sleep apnea (OSA) etiology. The association between craniofacial skeleton and OSA severity remains controversial. To study OSA's etiology, cephalometry, fiberoptic pharyngoscopy, polysomnography, and sleep endoscopy have been used; however, airway obstructions cannot be located. Recent research suggested ultrasonography for OSA screening and upper airway obstruction localization. Thus, this study aims to investigate the relationship between specific craniofacial cephalometric and ultrasonic airway parameters in adults at high risk of OSA. Methods: To assess craniofacial structure, lateral cephalograms were taken from thirty-three adults over 18 with a STOP-Bang questionnaire score of three or higher and a waist-to-height ratio (WHtR) of 0.5 or higher. Airway parameters were assessed through submental ultrasound. Results: NSBA correlated with tongue base airspace width, while MP-H correlated with oropharynx, tongue base, and epiglottis airspace width. SNA, SNB, and NSBA correlated with tongue width at the oropharynx. At tongue base, ANB and MP-H correlated with tongue width. SNB and NSBA were associated with deep tissue thickness at the oropharynx, while MP-H correlated with superficial tissue thickness at velum and oropharynx. Conclusions: Cephalometric parameters (SNA, SNB, ANB, NSBA, and MP-H) were correlated with ultrasonic parameters in the velum, oropharynx, tongue base, and epiglottis.

Comparison of Skeletal Stability after Le Fort I Osteotomy With Bone Fixation Using Biodegradable and Titanium Systems: A Retrospective Study.

The titanium osteosynthesis system used for fixing bone segments after maxillary osteotomy provides reliable outcomes owing to its biocompatibility and adequate strength. In addition, several studies have evaluated the skeletal stability after maxillary osteotomy with fixation using a biodegradable system. However, the indications for applying a biodegradable system after maxillary osteotomy remain controversial. Therefore, this study aimed to compare the long-term skeletal stability of bone segments after maxillary osteotomy with bone fixation using biodegradable and titanium osteosynthesis systems and to assess the usefulness of a biodegradable osteosynthesis system. Patients who underwent Le Fort I osteotomy of the maxilla to correct jaw deformities between April 2008 and March 2021 were included in this study. A total of 45 patients were included, with 28 in the biodegradable osteosynthesis system group and 17 in the titanium group. Cephalometric and computed tomography analyses were performed to evaluate the skeletal stability of the bone segments after maxillary osteotomy with bone fixation using biodegradable or titanium osteosynthesis systems. The maxillary segment was repositioned anteriorly with a clockwise rotation. Skeletal stability was similar between the biodegradable and titanium osteosynthesis systems. Segmental changes occurred mainly in the first 6 months after surgery, and the segment was completely stable between 6 and 12 months after surgery. This study revealed no significant differences in skeletal stability after maxillary osteotomy between the biodegradable and titanium osteosynthesis systems. However, the findings in this study should be interpreted with caution owing to the small sample size and small amount of maxillary-segment movement.

Biomechanical effect of dual-dimensional archwire on controlled movement of anterior teeth compared with rectangular archwire: A finite element study.

INTRODUCTION: This study aimed to determine and compare the effectiveness of the use of the dual-dimensional archwire and conventional rectangular archwire on tooth movement patterns when combined with various lengths of power arms. METHODS: Displacements of the maxillary central incisor and the deformation of the wire section were calculated when applying retraction forces from different lengths of power arms using the finite element method. RESULTS: Torque control of the incisor could be carried out more effectively when using the dual-dimensional archwire combined with long power arms than with the rectangular archwire. The use of the dual-dimensional archwire produced bodily movement of the central incisor at height levels of the power arm between 8 and 10 mm and lingual root tipping at the level of 10 mm. CONCLUSIONS: The use of the dual-dimensional archwire provided better-controlled movement of the incisor, including bodily movement or root movement, than the rectangular archwire.

Clinicopathological comparison between PTCL-TBX21 and PTCL-GATA3 in Japanese patients.

AIM: Peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) is a heterogeneous disease that can be classified into the PTCL-TBX21 and PTCL-GATA3 subtypes. METHODS: In this study, we compared the clinicopathological features of PTCL-NOS in a Japanese cohort, classified using an IHC algorithm. RESULTS: One hundred patients with PTCL-NOS were categorized as having PTCL-TBX21 (n = 55), PTCL-GATA3 (n = 24), or PTCL-unclassified (n = 21). When comparing PTCL-TBX21 and PTCL-GATA3, PTCL-TBX21 showed significantly lower CD4 positivity (p = 0.047), lower counts of high endothelial venules (p = 0.032), and a tendency for a better response to initial treatment (p = 0.088). Gene expression analysis using the nCounter system showed higher expression of tumor immunity-related genes, such as PD-L1, LAG3, and IDO1, in PTCL-TBX21 than in PTCL-GATA3. PTCL-GATA3 had significantly worse overall survival (OS) than those with PTCL-TBX21 (p = 0.047), although a similar tendency was observed for progression-free survival (PFS) (p = 0.064). PTCL-GATA3 was a prognostic factor for OS in univariate analysis (HR 2.02; 95% CI, 1.09-3.77; p = 0.027), although multivariate analysis did not show significance (HR 2.07; 95% CI, 0.93-4.61; p = 0.074). In the PFS analysis, PTCL-GATA3 was an independent prognostic factor by univariate analysis (HR 1.96; 95% CI, 1.08-3.56; p = 0.027) and multivariate analysis (HR 2.34; 95% CI, 1.07-5.11; p = 0.032). CONCLUSION: The classification of PTCL-NOS into PTCL-TBX21 and PTCL-GATA3 is useful for predicting the prognosis of Japanese patients and stratifying the administration of tumor immune checkpoint inhibitors in clinical practice.

Comparison of the skeletal stability after mandibular counter-clockwise rotation in three surgical procedures.

The treatment of mandibular deformities with an anterior open bite is challenging. In this study, skeletal stability after mandibular osteotomies was evaluated to determine the best treatment for mandibular prognathism with an anterior open bite in three procedures: intraoral vertical ramus osteotomy (IVRO), conventional sagittal split ramus osteotomy (conv-SSRO), and SSRO without bone fixation (nonfix-SSRO). Patients who underwent mandibular osteotomy to correct skeletal mandibular protrusion were included. Changes in skeletal and soft tissues were assessed using lateral cephalograms taken before (T1), 3 ± 2 days (T2), and 12 ± 3 months (T3) after surgery. Thirty-nine patients were included: nine in the IVRO group and 11 and 19 in the conv- and nonfix-SSRO groups, respectively. The mandibular plane angles (MPAs) of the T2-T1 were - 2.7 ± 2.0 (p = 0.0040), - 3.7 ± 1.7 (p < 0.0001), and - 2.3 ± 0.7 (p < 0.0001) in the IVRO, conv-SSRO, and nonfix-SSRO groups, respectively. The skeletal relapse of the MPAs was not related to the MPA at T2-T1, and it was approximately 1.3° in the conv-SSRO group. The skeletal relapse of the MAPs was significantly correlated with the MPA of T2-T1 in the IVRO (p = 0.0402) and non-fix-SSRO (p = 0.0173) groups. When the relapse of the MPAs was less than 1.3°, the MPA of T2-T1 was calculated as 2.5° in the nonfix-SSRO group. When the MPA of T2-T1 is less than 2.5°, non-fix SSRO may produce a reliable outcome, and when it is more than 2.5°, conv-SSRO may produce better outcomes.

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

OBJECTIVES: To determine the effect of orthodontic pressure on periodontal ligament (PDL) compression in rats and assess correlation between PDL compression and orthodontically induced root resorption (OIRR). MATERIALS AND METHODS: Eight female Wistar rats aged 10 weeks underwent surgery to place 2 mini-screws at the center of the palatal plate. 25 cN coil springs connecting the maxillary first molars and mini-screws were applied bilaterally to generate mesial force. Maxillary first molars were assigned to undergo either bodily or tipping movements. Micro-computed tomography (µCT) scans were taken on days 0, 3, 7, and 14, and histological sections were taken on day 14. OIRR was measured from histological sections, and the corresponding PDL compression ratio was quantified using µCT images. RESULTS: The PDL was compressed by approximately 76% in tipping movement and 55% in bodily movement after 3 days, and by approximately 47% in bodily and tipping movements after 7 days of orthodontic force application. The extent of OIRR in tipping movement was significantly greater than that in bodily movement. A strong positive correlation between OIRR and PDL compression ratio was observed on day 3; however, no correlation was observed on day 7. CONCLUSIONS: A strong correlation between PDL compression ratio and OIRR was observed at an early stage after the application of orthodontic force regardless of the tooth movement type (bodily or tipping), implying the importance of early stage PDL compression in the induction of OIRR.

TP63 fusions drive multicomplex enhancer rewiring, lymphomagenesis, and EZH2 dependence.

Gene fusions involving tumor protein p63 gene (TP63) occur in multiple T and B cell lymphomas and portend a dismal prognosis for patients. The function and mechanisms of TP63 fusions remain unclear, and there is no target therapy for patients with lymphoma harboring TP63 fusions. Here, we show that TP63 fusions act as bona fide oncogenes and are essential for fusion-positive lymphomas. Transgenic mice expressing TBL1XR1::TP63, the most common TP63 fusion, develop diverse lymphomas that recapitulate multiple human T and B cell lymphomas. Here, we identify that TP63 fusions coordinate the recruitment of two epigenetic modifying complexes, the nuclear receptor corepressor (NCoR)-histone deacetylase 3 (HDAC3) by the N-terminal TP63 fusion partner and the lysine methyltransferase 2D (KMT2D) by the C-terminal TP63 component, which are both required for fusion-dependent survival. TBL1XR1::TP63 localization at enhancers drives a unique cell state that involves up-regulation of MYC and the polycomb repressor complex 2 (PRC2) components EED and EZH2. Inhibiting EZH2 with the therapeutic agent valemetostat is highly effective at treating transgenic lymphoma murine models, xenografts, and patient-derived xenografts harboring TP63 fusions. One patient with TP63-rearranged lymphoma showed a rapid response to valemetostat treatment. In summary, TP63 fusions link partner components that, together, coordinate multiple epigenetic complexes, resulting in therapeutic vulnerability to EZH2 inhibition.

Rab44 negatively regulates myoblast differentiation by controlling fusogenic protein transport and mTORC1 signaling.

Skeletal muscle is composed of multinucleated myotubes formed by the fusion of mononucleated myoblasts. Skeletal muscle differentiation, termed as myogenesis, have been investigated using the mouse skeletal myoblast cell line C2C12. It has been reported that several "small" Rab proteins, major membrane-trafficking regulators, possibly regulate membrane protein transport in C2C12 cells; however, the role of Rab proteins in myogenesis remains unexplored. Rab44, a member of "large" Rab GTPases, has recently been identified as a negative regulator of osteoclast differentiation. In this study, using C2C12 cells, we found that Rab44 expression was upregulated during myoblast differentiation into myotubes. Knockdown of Rab44 enhanced myoblast differentiation and myotube formation. Consistent with these results, Rab44 knockdown in myoblasts increased expression levels of several myogenic marker genes. Rab44 knockdown increased the surface accumulation of myomaker and myomixer, two fusogenic proteins required for multinucleation, implying enhanced cell fusion. Conversely, Rab44 overexpression inhibited myoblast differentiation and tube formation, accompanied by decreased expression of some myogenic markers. Furthermore, Rab44 was found to be predominantly localized in lysosomes, and Rab44 overexpression altered the number and size of lysosomes. Considering the underlying molecular mechanism, Rab44 overexpression impaired the signaling pathway of the mechanistic target of rapamycin complex1 (mTORC1) in C2C12 cells. Namely, phosphorylation levels of mTORC1 and downstream mTORC1 substrates, such as S6 and P70-S6K, were notably lower in Rab44 overexpressing cells than those in control cells. These results indicate that Rab44 negatively regulates myoblast differentiation into myotubes by controlling fusogenic protein transport and mTORC1 signaling.

Occlusal Plane Angle as a Key Factor for Chin Protrusion After Mandibular Osteotomy in Skeletal Class III.

There is no treatment algorithm to decide whether maxillomandibular or mandibular osteotomy alone should be performed in borderline cases. This study assessed the factors that affect the changes in soft tissue after mandibular setback. Patients who underwent mandibular osteotomy alone to correct mandibular protrusion were included in this study. Hard and soft tissue analyses were performed on lateral cephalograms before and 12±3 months after surgery. The popular points were set for referencing hard and soft tissues on the lateral cephalogram. Nasolabial, labiomental, and soft tissue facial plane angles were measured for the soft tissue assessment. To assess the mandibular setback amount, SNB was calculated. Twenty-one patients were included in this study. The nasolabial angle was increased after surgery and its change significantly correlated with the change in SNB ( P =0.00815). The change in soft tissue facial plane angle after surgery per change in SNB significantly correlated with the occlusal plane angle ( P =0.0009). An occlusal plane angle of at least 15.45 degrees was required for the SNB and soft tissue facial plane angle to change to the same degree. The occlusal plane angle (whether or not it was ≥15.45 degrees) may help in determining the surgical approach in borderline cases, specifically on whether maxillomandibular or mandibular osteotomy alone should be performed if the mandibular setback is simple.

Three major reasons why transgenerational effects of radiation are difficult to detect in humans.

PURPOSE: Ionizing radiation can induce mutations in germ cells in various organisms, including fruit flies and mice. However, currently, there is no clear evidence for the transgenerational effects of radiation in humans. This review is an effort to identify possible reasons for the lack of such observations. METHODS: Literature search and narrative review. RESULTS: 1) In both mice and humans, resting oocytes locate primarily in the cortical region of the ovary where the number of blood vessels is very low especially when young and extra-cellular material is rich, and this region is consequently hypoxic, which probably leads to immature oocytes being resistant to the cell killing and mutagenic effects of radiation. 2) In studies of spermatogonia, the mouse genes used for specific locus test (SLT) studies, which include coat color genes, were hypermutable when compared to many other genes. Recent studies which examined over 1000 segments of genomic DNA indicate that the induction rate of deletion mutation per segment was on the order of 10-6 per Gy, which is one order of magnitude lower than that obtained from the SLT data. Therefore, it appears possible that detecting any transgenerational effects of radiation following human male exposures will be difficult due to a lack of mutable marker genes. 3) Fetal malformations were examined in studies in humans, but the genetic component in such malformations is low, and abnormal fetuses are prone to undergo miscarriage which does not occur in mice, and which leads to difficulties in detecting transgenerational effects. CONCLUSION: The lack of clear evidence for radiation effects in humans probably does not result from any problem in the methodologies used but may be due largely to biological properties. Currently, whole genome sequencing studies of exposed parents and offspring are planned, but ethical guidelines need to be followed to avoid discrimination, which had once happened to the atomic bomb survivors.

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

OBJECTIVES: To create an orthodontic anchor screw (OAS)-loosening model and to investigate whether filling the bone hole with beta-tricalcium phosphate (ß-TCP) can fix the OAS against orthodontic force. MATERIALS AND METHODS: Bone holes with different diameters (1.6, 2.1, or 2.5 mm) were drilled in the tibias of 11-week-old male Wistar rats, and an OAS (3.0 mm in length and 1.2 mm in diameter) was inserted. After a healing period of 2 or 4 weeks, orthodontic force was applied, and the diameter of the bone hole appropriate for the loosening model was determined. Subsequently, under the loosening model, the bone hole was filled with ß-TCP, orthodontic force was applied, and movement of the OAS and surrounding tissue changes were evaluated by micro-computed tomography images and histological specimen analysis. RESULTS: The bone hole of 1.6 mm in diameter was employed as the OAS-loosening model. When ß-TCP was inserted into the bone hole, the linear distance and mesial tipping angle of the OAS movement decreased markedly. Furthermore, the values of bone morphometry significantly increased with ß-TCP filling. CONCLUSIONS: An OAS-loosening model was established in rats and demonstrated that the loosening OAS was stabilized by ß-TCP filling through bone formation. ß-TCP may be useful for fixation of a loosening OAS.

Mesial or distal to canine: Which is better for the position of closing loops? Analysis of tooth movements based on numerical simulation.

INTRODUCTION: Although many studies investigating the mechanical behavior of loop mechanics have focused on loop designs to produce a higher moment-to-force ratio, few studies have clarified the effect of loop position on the force system and resultant tooth movements. This study aimed to simulate orthodontic tooth movements during space closure and to compare the effects of loop position in association with different degrees of gable bend on tooth movements using the finite element method. METHODS: Two finite element models of the maxillary dentition were constructed, with the loop placed mesial or distal to the canine. Tooth movements during loop activation were simulated while varying the degree of gable bend. RESULTS: When the loop was placed distal to the canine, the incisor showed uncontrolled tipping even with the gable bend. Placement of the loop mesial to the canine produced controlled tipping or root movement of the incisor, depending on the degree of gable bend. CONCLUSIONS: Placement of the closing loop mesial to the canine in combination with the incorporation of a gable bend into the archwire distal to the canine could provide better control of incisor movements, such as controlled tipping or root movement, as compared with placement of a gable bend into the loop located distal to the canine.

Influence of different treatment procedures on the temporomandibular joint after mandibular setback in skeletal class III - A retrospective study.

The aim of this study was to clarify the effects of three different orthognathic surgical procedures on the temporomandibular joint after mandibular setback. Conventional sagittal split ramus osteotomy (SSRO) with segmental fixation (conv-SSRO), intraoral vertical ramus osteotomy (IVRO), or SSRO without fixation followed by the physiological positioning strategy (nonfix-SSRO) was performed for mandibular setback. Temporomandibular joint disorder (TMD) symptoms were clinically assessed, and the condylar head angle was measured. In total, 129 patients participated. Preoperative TMD and treatment procedure were related to postoperative TMD. A menton deviation of 3.43 mm was the cutoff for the risk of postoperative TMD. The incidence rate of postoperative TMD in the conv-SSRO group was higher than that in the IVRO (p = 0.0197) and nonfix-SSRO (p = 0.0001) groups in asymmetric cases. There was no significant postoperative change in the temporomandibular joint space in each group. In symmetric and asymmetric cases, the condylar head was rotated inwards by 5.82 ± 4.75° (p < 0.0001) and 5.44 ± 3.10° (p < 0.0001), respectively, in the conv-SSRO group, and outwards by -7.98 ± 5.05° (p < 0.0001) and -8.32 ± 6.38° (p < 0.0001), respectively, in the IVRO group, but it was almost stable in the nonfix-SSRO group. Within the limitations of the study it seems that nonfix-SSRO should be preferred over conv-SSRO and IVRO whenever appropriate.

Effect of masseter muscle mass on the rate of experimental tooth movement in rats.

BACKGROUND: Previous clinical observational studies have suggested that orthodontic tooth movement (OTM) is related, at least partly, to the mass and/or capabilities of the masticatory muscles. OBJECTIVES: Our study aimed to examine the influence of masticatory muscle mass on the OTM in an animal experimental model in which the masseter muscle was modulated by botulinum neurotoxin type A (BTX) injection. METHODS: Eighteen Wistar rats were equally divided into two groups: BTX injection and control. BTX was injected bilaterally into the masseter muscles. Three days after the injection, the maxillary left first molars were orthodontically moved for 14 days. At the end of the experiment, micro-computed tomography was performed to evaluate the rate of OTM and bone morphometry. The masseter muscles were weighed and prepared for histological analyses. RESULTS: The masseter muscle mass in the BTX group was less than that in the control group, and histological findings showed atrophy of muscle fibres. The rate of OTM was significantly higher in the BTX group than in the control group. Furthermore, a negative correlation was detected between masseter muscle mass and OTM in the BTX group. Bone morphometry showed no difference between the control and BTX groups. CONCLUSION: Decreased masseter muscle mass was found to be closely related to an increase in the rate of OTM in rats using BTX injection to modify the masseter muscle mass. Masseter muscle mass could be a predictive factor for OTM in rats injected with BTX.

Biomechanical features of tooth movement from a lingual appliance in comparison with a labial appliance during space closure in sliding mechanics.

INTRODUCTION: The objectives of this study were to simulate long-term orthodontic tooth movement in en-masse retraction using the finite element method and investigate the effects of power arms on tooth movements when using a lingual appliance in comparison with a labial appliance. METHODS: A 3-dimensional finite element model of the maxillary dentition was constructed with 0.018-in brackets and 0.016 × 0.022-in stainless steel archwire. An en-masse retraction was performed by applying retraction force at various lengths of the power arm (4, 6, 8, and 10 mm) to the second molar tube, and long-term tooth movements with the lingual and labial appliances were analyzed using the finite element method. RESULTS: Although lingual crown tipping of the incisor was more marked with the lingual appliance than with the labial appliance in the early phase of space closure, only a slight difference was evident after space closure. Although the power arm was effective for achieving better-controlled tooth movement and reducing vertical and transverse bowing effects, bodily movement of the incisor could not be achieved, and bowing effects could not be eliminated. CONCLUSIONS: To provide better torque control of the incisor or prevent a vertical bowing effect, the incorporation of extra torque into brackets of incisors was recommended, and the use of power arms for the lingual appliance. To prevent a transverse bowing effect, incorporation of the antibowing bend or application of retraction force from both buccal and lingual sides or temporary skeletal anchorage devices was recommended.

Sp7 Transgenic Mice with a Markedly Impaired Lacunocanalicular Network Induced Sost and Reduced Bone Mass by Unloading.

The relationship of lacunocanalicular network structure and mechanoresponse has not been well studied. The lacunocanalicular structures differed in the compression and tension sides, in the regions, and in genders in wild-type femoral cortical bone. The overexpression of Sp7 in osteoblasts resulted in thin and porous cortical bone with increased osteoclasts and apoptotic osteocytes, and the number of canaliculi was half of that in the wild-type mice, leading to a markedly impaired lacunocanalicular network. To investigate the response to unloading, we performed tail suspension. Unloading reduced trabecular and cortical bone in the Sp7 transgenic mice due to reduced bone formation. Sost-positive osteocytes increased by unloading on the compression side, but not on the tension side of cortical bone in the wild-type femurs. However, these differential responses were lost in the Sp7 transgenic femurs. Serum Sost increased in the Sp7 transgenic mice, but not in the wild-type mice. Unloading reduced the Col1a1 and Bglap/Bglap2 expression in the Sp7 transgenic mice but not the wild-type mice. Thus, Sp7 transgenic mice with the impaired lacunocanalicular network induced Sost expression by unloading but lost the differential regulation in the compression and tension sides, and the mice failed to restore bone formation during unloading, implicating the relationship of lacunocanalicular network structure and the regulation of bone formation in mechanoresponse.