To investigate the level and distribution of stresses in composite-restored mandibular first molars with various combinations of base materials.The finite element package Abaqus was used for the stress analysis. Several different base materials were evaluated [light-cured glass ionomer (LC-GI), chemically-cured calcium hydroxide (CC-CH), and light-cured calcium hydroxide (LC-CH)] in combination with light-cured composite (LC-CP). Four models of restored molars with Class I deep cavity preparations were simulated, including (1) LC-GI/LC-CP, (2) CC-CH/LC-CP, (3) CC-CH/LC-GI/LC-CP, and (4) LC-CH/LC-GI/LC-CP. A 250N static single-point load was applied vertically on the central fossa of the tooth to simulate physical loading conditions.In each case, the peak stresses were found to be concentrated mainly at the interfaces between the various materials and the dental tissues. In the residual tooth structures, the maximum Von Mises stresses were 20.01 MPa in model LC-GI/LC-CP, 23.85 MPa in model CC-CH/LC-CP, 23 MPa in model CC-CH/LC-GILC-CP and 21.83 MPa in model LC-CH/LC-GIILC-CP. In the LC-CP restorations, the maximum Von Mises stresses were 43.68 MPa in model LC-GILC-CP, 42.24 MPa in model CC-CH/LC-CP, 42.29 MPa in model CC-CH/LC-G/LC-CP and 42.55 MPa in model LC-CH/LC-GI/LC-CP. In the bases, the maximum Von Mises stresses were 5.71 MPa in model LC-GI/LC-CP, 0.85 MPa in model CC-CH/LC-CP, 4.69 MPa in model CC-CH/LC-GI/LC-CP, and 4.93 MPa in model LC-CH/LC-GILC-CP.
The objective of this study was to evaluate the efficacy of cognitive behavioral therapy intervention for patients who experienced pain during orthodontic treatment. The baseline characteristics were assessed via questionnaires and oral examinations. Four hundred and fifty eligible individuals were recruited and randomized by computer-generated block randomization into three groups: cognitive behavioral therapy intervention (n = 150), ibuprofen intervention (n = 150), and no intervention (control; n = 150). Primary outcomes were the change from baseline in pain intensity measured with 100-mm Visual Analog Scale (VAS) scores at 1, 2, 3, 7, 14, and 30 days after initial archwire placement. Outcomes assessment was blinded and followed the intention-to-treat principle. One hundred forty-three (95.30%), 145 (96.70%), and 141 (94.00%) individuals in the cognitive behavioral therapy, the ibuprofen, and the control groups, respectively, completed the one-month follow-up evaluations. Those in the cognitive behavioral therapy group showed a greater decrease in mean VAS scores than did those in the control group over the previous five time-points (p < 0.001). Cognitive behavioral therapy was shown to be effective in pain control during the initial stage of orthodontic treatment. The study registration number was ChiCTR-TRC-00000556.
Abstract High‐performance ferromagnetic materials are essential for energy conversion and electronic devices. However, the random and nonuniform magnetization reversal in ferromagnetics limits their performance that can be achieved. Here, through both micromagnetism simulations and experiments, a directional magnetization reversal that initiates first from large grains toward smaller ones is discovered by engineering Nd 2 Fe 14 B/α‐Fe gradient nanostructures. Such directional magnetization reversal enables a rare combination of high magnetization and large coercivity, thus leading to a record‐high energy density (26 MG Oe) for isotropic permanent magnetic materials, which is ≈50% higher than that of its gradient‐free counterpart. The unusual magnetization reversal originates from an ordered arrangement of grain sizes in the gradient material, where the large grains have a lower reversal field than that of the smaller ones. These findings open up new opportunities for developing high‐performance magnetic materials.
Increased susceptibility to bone fragility and the diminution of bone regenerative capacity are recognized as significant and frequent sequelae of diabetes mellitus. Research has elucidated the pivotal role of macrophages in the pathogenesis and repair of diabetic bone defects. Notwithstanding this, the therapeutic efficacy of traditional interventions remains predominantly inadequate. Concomitant with substantial advancements in tissue engineering in recent epochs, there has been an escalation in the development of biomaterials designed to modulate macrophage activity, thereby augmenting osseous tissue regeneration in the context of hyperglycemia. This review amalgamates insights from extant research and delineates recent progressions in the domain of biomaterials that target macrophages for the regeneration of diabetic bone, whilst also addressing the clinical challenges and envisaging future directions within this field.
OBJECTIVE Retention elements were added in the removable reverse headgear appliances in order to achieve better treatment effects of skeletal Class III malocclusion. METHODS Eighteen patients who needed treatments with reverse headgear appliances were randomly and equally divided into two groups with traditional type of retention elements (T group) and modified type of retention elements (M group) respectively. For the modified type appliances, an adams clasp was added in the position of central incisors on the basis of the traditional type. The minimum dislocating force for both types was measured with the same forcemeter in the first and second visit, respectively. The occurrence of dislocation caused by traction was recorded during the visits of the first three months. RESULTS The M group showed significantly greater retention than the T group. The minimum dislocating force for M group was larger in the first and second visit (P<0.01, P<0.001). Furthermore, during the first three months, two times of dislocation occurred in M group while it was nine times for T group, indicating great difference in retention (P< 0.05). CONCLUSION Adding an adams clasp in the position of upper central incisors could effectively prevent the downward dislocation of the appliance when traction force was applied. Accordingly, the therapeutic efficacy was greatly improved.
To test the null hypothesis that increased tooth displacement in ovariectomized rats is not related to differential expressions of OPG and RANKL in the periodontium.Eighty-four 12-week female rats were used; half were ovariectomized and half were not. Three months later, the maxillary first molar was moved mesially. Groups of rats were sacrificed at days 0, 1, 3, 5, 7, 10, and 14 after activation. Tooth movement was measured at each time point. OPG and RANKL expressions were examined through immunohistochemistry.Ovariectomized and nonovariectomized rats showed three-phase tooth movement. In both groups, OPG expression increased at the tension area and RANKL increased at the pressure area. The OPG/RANKL ratio coincided with tooth movement, especially in the linear phase from 7 to 14 days.The null hypothesis is rejected. The increased rate of tooth movement in ovariectomized rats was related to differential expressions of OPG and RANKL.
To: Editor, The Angle OrthodontistRe: Effect of injectable platelet-rich fibrin (i-PRF) on the rate of tooth movement: A randomized clinical trial. Emire Aybuke Erdur, Kuter Karakaslı, Elif Oncu, Bahadır Ozturk, Sema Hakkı. Angle Orthod. 2021;91:285-292.We read this article with great interest. However, in the Materials and Methods section, it said that “movement of the canine was evaluated by measuring the distance between the midpoints of the vertical lines drawn from the incisal edge to the cervical line over the marginal ridge of the lateral and canine teeth on the dental cast”, which means that the movements and positions of both the lateral incisor and canine directly affected the accuracy of measurement of canine retraction. However, the authors say that “Canine distalization was conducted using Ni-Ti closed-coil springs connected from a miniscrew to a hook placed in front of the canine brackets”, as shown in Figure 1, which means that the incisors and canine may have been retracted together with an en mass retraction pattern. Thus, the lateral incisor was retracted along with the canine, making the measured distance of canine movement less than the actual value. Do you think it would have been better to measure canine movement relative to a more stable landmark, or that the method of retraction could have been achieved differently for this study?
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