Clear aligner orthodontic therapy of rotated mandibular round-shaped teeth: A finite element study

Objective:To evaluate, using the finite element method, the orthodontic rotational movement of a lower second premolar obtained with clear aligners, analyzing different staging and attachment configurations.Materials and Methods:A CAD model including a complete lower dental arch (with element 4.5 mesially rotated 30°) and the corresponding periodontal ligaments, attachments, and aligner was designed and imported to finite element software. Starting from the CAD model, six projects were created to simulate the following therapeutic combinations for correcting element 4.5 position: (1) without attachments, (2) single attachment placed on the buccal surface of element 4.5, (3) three attachments placed on the buccal surfaces of teeth 4.4 to 4.6. For each project, both 1.2° and 3° of aligner activation were considered.Results:All the analyzed configurations revealed a clockwise rotation movement of element 4.5 on the horizontal plane. Models with attachments showed a greater tooth displacement pattern than models without attachments. Simulations with attachments and 3° of aligner activation exhibited the best performance concerning tooth movement but registered high stresses in the periodontal ligaments, far from the ideal stress levels able to produce tooth rotational movement.Conclusions:The model with a single attachment and 1.2° of aligner activation was the most efficient, followed by the three attachment model with the same degree of activation. Aligner activation should not exceed 1.2° to achieve better control of movement and reasonable stress in periodontal structures.     

Morphometric analysis of dental arch form changes in class II patients treated with clear aligners

Journal of Orofacial Orthopedics / Fortschritte der Kieferorthopädie - The purpose of this study was to evaluate the arch form changes in class II Caucasian patients treated with...     

Bone mineral density improvement after lung volume reduction surgery for severe emphysema

BACKGROUND: In patients with severe emphysema, bone mineral density (BMD) is reduced and the risk of osteoporosis is increased. STUDY OBJECTIVES: To identify the impact of lung volume reduction surgery on BMD. DESIGN: Prospective cohort study. SETTING: University hospital. PATIENTS AND INTERVENTIONS: Forty emphysematous patients, all receiving oral steroid therapy, underwent bilateral lung volume reduction surgery. Thirty similar patients, who refused the operation, followed a standard respiratory rehabilitation program. MEASUREMENTS: All subjects were evaluated pretreatment and 12 months posttreatment for respiratory function, nutritional status, and bone-related biochemical parameters. BMD was assessed by dual-energy radiograph absorptiometry. RESULTS: After surgery, we observed significant improvements in respiratory function (FEV1, + 18.8% [p < 0.01]; residual volume [RV], -29.6% [p < 0.001]; diffusing capacity of the lung for carbon monoxide [Dlco], + 21.6% [p < 0.01]) nutritional parameters (fat-free mass, + 6.0% [p < 0.01]), levels of bone-related hormones (free-testosterone, + 20.5% [p < 0.01]; parathormone, -11.2% [p < 0.01]), bone turnover markers (osteocalcin, -12.7% [p < 0.05]; bone-alkaline-phosphatase, -14.0% [p < 0.05]; beta-crosslaps, -33.6% [p < 0.001]), BMD (lumbar, + 8.8% [p < 0.01]; femoral, + 5.5% [p < 0.01]), and T-score (lumbar, + 21.0% [p < 0.01]; femoral, + 12.4% [p < 0.01]) with reduction in osteoporosis rate (50 to 25%). Nineteen patients who had undergone surgery were able to discontinue treatment with oral steroids. These subjects showed a more significant improvement in BMD (lumbar, + 9.6%; femoral, + 6.8%; p < 0.001) and T-score (lumbar, + 27.3%; femoral, + 14.3%; p < 0.001). The remaining 21 patients who had undergone surgery experienced significant improvement compared to respiratory rehabilitation subjects despite continued therapy with oral steroids (BMD: lumbar, + 4.5% vs -0.7%, respectively [p < 0.01]; femoral, + 2.7% vs -1.1%, respectively [p < 0.05]; T-score: lumbar, + 14 vs -2.1, respectively [p < 0.01]; femoral, + 7.4 vs -2.7, respectively [p < 0.01]). The increase in lumbar BMD was correlated with the surgical reduction of RV (p = 0.02) and with the increase in Dlco (p = 0.01) and fat-free mass (p = 0.01). CONCLUSIONS: Lung volume reduction surgery significantly improves BMD compared to respiratory rehabilitation therapy, even in patients requiring oral steroids. The increase in BMD correlates with RV, Dlco, and fat-free mass, suggesting that the restoration of respiratory dynamics, gas exchange, and nutritional status induces improvement in bone metabolism and mineral content.     

Cellular signaling by an agonist-activated receptor/Gs alpha fusion protein.

The consequences of agonist-dependent activation of guanine nucleotide-binding protein (G protein)-coupled receptors vary from cell to cell, depending on a complex network of regulations between components of the signaling cascade. Specific interactions between receptors, G proteins, and effectors are difficult to analyze in intact cells. Engineering of receptor-transducer fusion proteins might be an effective strategy to target cellular effectors more efficiently and specifically. As a model, we evaluated the ability of a fusion protein of beta 2-adrenergic receptor bound to the alpha subunit of adenylyl cyclase-stimulatory G protein (Gs alpha) to restore the defective activation of adenylyl cyclase in S49 cyc- cells that lack endogenous Gs alpha. The coupling between the two partners of the fusion protein was functional, and the agonist-dependent activation of the effector was more potent and more productive in transfected than in wild-type S49 cells. The covalent link between receptor and Gs alpha could thus convey an advantage over freely interacting components. Such receptor-G alpha fusion proteins may help to elucidate the complex interactions between members of signaling pathways and may also constitute a useful tool for studying the effects of single effector activation.