Effect of varying auxiliaries on maxillary incisor torque control with clear aligners: A finite element analysis.

INTRODUCTION: This study aimed to evaluate the effects of varying auxiliaries on tooth movement and stress distribution when maxillary central incisors were torqued 1° with a clear aligner through finite element analysis. METHODS: Three-dimensional finite element models, including maxillary alveolar bone, periodontal ligament, dentition, and clear aligner, were constructed. According to the auxiliaries designed on the maxillary central incisor, 5 models were created: (1) without auxiliaries (control model), (2) with the power ridge, (3) with the semi-ellipsoid attachment, (4) with the horizontal rectangular attachment, and (5) with the horizontal cylinder attachment. The tooth movement and periodontal ligament stress distribution after a palatal root torque of 1° were analyzed for each of the 5 models. RESULTS: With 1° torque predicted, the maxillary central incisor without auxiliaries showed a tendency of labial tipping, mesial tipping, and intrusion. The rotation center moved occlusally in the power ridge model. The labiolingual inclination variation increased in the semi-ellipsoid attachment model but decreased in the power ridge model. The maxillary central incisor is twisted in the distal direction in the power ridge model. The maxillary central incisor of the horizontal rectangular attachment and the horizontal cylinder attachment model behaved similarly to the control model. Periodontal stresses were concentrated in the cervical and apical areas. The maximum von Mises stresses were 11.6, 12.4, 3.81, 1.14, and 11.0 kPa in the 5 models. The semi-ellipsoid attachment model exhibited a more uniform stress distribution than the other models. CONCLUSIONS: Semi-ellipsoid attachment performed better efficacy on labiolingual inclination, and power ridge performed better efficacy on root control. However, a distal twist of maxillary incisors could be generated by the power ridge.

Efficacy of upper-incisor torque control with clear aligners: a retrospective study using cone-beam computed tomography.

OBJECTIVES: The objectives of this retrospective clinical study were to evaluate the efficacy of clear aligners on upper-incisor torque control, with the expectation of providing guidance for clinics. MATERIALS AND METHODS: Pretreatment (T0) and posttreatment (T1) cone-beam computed tomography (CBCT) scans of 47 patients with a nonextraction treatment using clear aligners were obtained and 120 upper-incisors with torque ≥5° were selected. Voxel-based superimpositions were performed using Dolphin imaging software and achieved movements were then measured. Difference between achieved and predicted movement (DAPM) and the efficiency for upper-incisor torque were used to evaluate the torque control efficacy. RESULTS: The achieved torque movement with clear aligners was lower than predicted significantly, as the mean efficiency was 46.81±33.95%. Additionally, the achieved incisor movement of the crown and root differed significantly from the predicted movement, especially root movement. CONCLUSIONS: Clear aligners struggle to control upper-incisor torque, particularly root movement. In that case, overcorrection is necessary to prevent torque loss. CLINICAL RELEVANCE: Clear aligners remain a limitation on torque control and overcorrection should be considered.

Wide-field optical design for a 60 m submillimeter telescope.

We present a practical wide-field optical design for a 60 m aperture submillimeter telescope, which is currently under conceptual design study in China. The telescope is specified to operate over a wavelength range of 0.65-3 mm and provide a wide field of view (FOV) of 1° in diameter. We designed an F/6 Ritchey Chrétien (RC) system with a quasi-planar tertiary corrector, which cancels all spherical, coma, and astigmatism aberrations. It also achieves a good balance among the mirror sizes, central obscuration, and focal-plane curvature. The problems of focal surface curvature and nontelecentricity are treated in the subfield instrumental design, which employs a simple silicon wedge prism to obtain flat and telecentric focal planes for each subfield instrument module. Our studies show that by such a design, more than ${{10}^5}$105 detector pixels can be efficiently and uniformly fed at the shortest wavelength band with Strehl ratios above 0.85 across the entire 1° FOV. Several practical issues related to the telescope optics are also discussed.

[Effect of Salvia Miltiorrhiza Bunge on expression of osteoprotegerin in cultured human periodontal ligament fibroblasts].

PURPOSE: To study the effect of Salvia Miltiorrhiza Bunge on the expression of osteoprotegerin (OPG) in cultured human periodontal ligament fibroblasts. METHODS: Primary culture of human periodontal ligament fibroblasts was established and the fifth passage cells were used in this study. Concentration-dependent effect of Salvia Miltiorrhiza Bunge on OPG mRNA and OPG protein secretion were determined by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme linked immunosorbant assay (ELISA), respectively. The data were analyzed with SPSS15.0 software package. RESULTS: OPG mRNA expression was increased after 1 h exposure to various concentrations of Salvia Miltiorrhiza Bunge compared with the control group (P<0.05). OPG protein secretion was significantly increased after 12 h exposure to various concentrations of Salvia Miltiorrhiza Bunge compared with the control group (P<0.05). CONCLUSION: Salvia Miltiorrhiza Bunge can up-regulate the expression of OPG in cultured human periodontal ligament fibroblasts.

[Study on the height of marginal ridge to cusp in posterior teeth and its effect on brackets placement].

OBJECTIVE: To measure the vertical height of mesio-distal marginal ridge to cusp in posterior teeth, which may be helpful to brackets positioning. METHODS: The study groups comprised of 60 patients (30 men, 30 women, mostly aged 12-14 years) who underwent orthodontic treatment without tooth extraction and matched the Andrews normal occlusion standard after treatment. Study model of each patient was made. Three-dimensional laser measurer was used to evaluate the vertical height of mesio-distal marginal ridge to mesial cusp in posterior teeth. The data were stored in a personal computer and submitted to statistical analysis of paired t test. RESULTS: No statistical significant difference was found in the same teeth between men and women. Not only in maxilla but also in mandible, there was no significant difference between the left and the right (P>0.05). The average vertical height of maxillary first premolars was (1.70+/-0.50) mm, the maxillary second premolars was (1.24+/-0.45) mm, and for maxillary first molars, the result was (0.83+/-0.40) mm. The difference between each result was statistically significant (P9< 0.01). The average vertical height of mandibular first premolars was (2.25+/-0.45) mm, the mandibular second premolars was (1.55+/-0.45) mm, and for mandibular first molars, the result was (1.18+/-0.40) mm. The difference between each result was statistically significant (P<0.0 1). CONCLUSION: The vertical height of brackets position in posterior teeth should be considered to guarantee that mesio-distal marginal ridges of deferent posterior teeth located in the same plane, so that satisfying goal could be achieved, If the vertical height in the first molar was X mm, the vertical height in the second premolar should be (X+0.5) mm, and (X+1.0) mm might be suit for the first premolar.

[Orthodontic treatment of Class III patients with mandibular asymmetry].

OBJECTIVE: To investigate the treatment outcome of Class III patients with dental, functional and mild skeletal mandibular asymmetry. METHODS: Thirty-five patients (14 males and 21 females) with dental, functional and mild skeletal mandibular asymmetry were selected. The age range of the patients was 7 - 22 years with a mean age of 16.5 years. Dental mandibular asymmetry was treated with expansion of maxillary arch to help the mandible returning to normal position. Functional mandibular asymmetry was treated with activator or asymmetrical protraction and Class III elastics. Mild skeletal mandibular asymmetry was treated with camouflage treatment. RESULTS: Good occlusal relationships were achieved and facial esthetics was greatly improved after orthodontic treatment in patients with dental and functional mandibular asymmetry. However, patients with skeletal mandibular asymmetry should be treated with both extraction and genioplasty. CONCLUSIONS: Orthodontic treatment was suitable for patients with dental and functional mandibular asymmetry, while combined orthodontics and surgery could get good results in patients with skeletal mandibular asymmetry.

Expression of vascular endothelial growth factor in cultured human dental follicle cells and its biological roles.

AIM: To investigate the expression of vascular endothelial growth factor (VEGF) in cultured human dental follicle cells (HDFC), and to examine the roles of VEGF in the proliferation, differentiation, and apoptosis of HDFC in vitro. METHODS: Immunocytochemistry, ELISA, and RT-PCR were used to detect the expression and transcription of VEGF in cultured HDFC. The dose-dependent and the time-course effect of VEGF on cell proliferation and alkaline phosphatase (ALP) activity in cultured HDFC were determined by MTT assay and colorimetric ALP assay, respectively. The effect of specific mitogen-activated protein kinase (MAPK) inhibitors (PD98059 and U0126) on the VEGF-mediated HDFC proliferation was also determined by MTT assay. The effect of VEGF on HDFC apoptosis was measured by flow cytometry. RESULTS: VEGF was transcribed and expressed in cultured HDFC. VEGF at 10-300 microg/L significantly increased HDFC proliferation and ALP activity compared to the control. Following 1, 3, 5, or 7 d of stimulation, VEGF induced a significant increase in HDFC proliferation compared with the corresponding control, while VEGF was effective at increasing ALP activity at the incubation time point of 3, 5, or 7 d. PD98059 and U0126 could attenuate the VEGF-mediated HDFC proliferation. Fewer apoptotic cells were observed in the VEGF-treated groups compared to the controls, although the difference was not statistically significant. CONCLUSION: VEGF is expressed in cultured HDFC, and at a proper concentration range can stimulate HDFC proliferation, induce HDFC to differentiate in a "cementoblast/osteoblast" pathway and protect HDFC from apoptosis. The MAPK signaling pathway might be involved in the VEGF-mediated HDFC proliferation.

Research on hereditability of gastric cancer in wuwei city.

AIM: To explore hereditability of gastric cancer in Wuwei city. METHODS: A case-control study was used to investigate 251 gastric cancer families located in Wuwei city. Li-Mantel-Gan and Falconer regression methods were used to calculate segregation ratios and hereditability. RESULTS: The segregation ratio in Wuwei families was 0.0774, the hereditability of class I kinfolks and class II kinfolks were respectively 22.91% and 20.07%. CONCLUSION: The segregation ratio of gastric cancer in Wuwei was significantly lower than for mono-genetic diseases (0.25), corresponding better with a model of polygenetic diseases. The genetic susceptibility factor accounted for about 1/5-1/4 in the formation of gastric cancer familial aggregation. Mi DH, Chen XP, Luo HZ Research on hereditability of gastric cancer in Wuwei city.

[Effects of surface potentials of tooth hard tissue on bone remodeling in rabbit tibiae].

OBJECTIVE: To investigate the influence of surface potentials of tooth hard tissue on bone remodeling. METHODS: After insured the surface potentials of human extracted teeth with electrochemical methods, teeth sections and artificial hydroxyapatite were implanted into 25 rabbits' tibiae. The rabbits were sacrificed at 1, 2, 4, 6 and 8 weeks after implantation, respectively. The bone regeneration was compared between opposite two sides (cathode side and anode side) of tooth sections using hematoxylin-eosin (HE) staining, tartrate-resistant acid phosphatase (TRAP) activity detecting and tetracycline tracing method. RESULTS: Resorption lacunae was seen in the tibiae facing to the enamel anode and new bone density in the implant bed near the cathode of tooth samples was much higher than that near the anode, while the number of TRAP positive cells near the cathode was smaller than that near the anode (P < 0.01). The fluorescent area of tetracycline tracing near the cathode was larger than that near the anode (P < 0.05). CONCLUSIONS: The cathode of tooth hard tissue (cementum) could improve or trigger new bone formation, while the other side, anode (enamel), could improve the bone resorption. This study suggests that tooth hard tissue's electrochemical characteristic might affect the remodeling of alveolar bone, and tooth supraeruption and the alveolar bone loss after tooth extraction might result from the redundant or lack of root electrochemical stimulation to bone.