"Gearing Effect in Clockwise Rotational Orthognathic Surgery".

BACKGROUND: The standard procedure for the management of skeletal class III malocclusion is maxillary advancement with mandibular setback. Occlusal plane altering orthognathic surgery, such as jaw rotation, is useful as well. Although clockwise jaw rotation is a common procedure, its mechanism has not been well-investigated. Therefore, in this study, we aim to introduce the gearing effect to correct class III malocclusion in Asians by maxillary posterior impaction via clockwise rotation without advancing the maxilla. METHODS: Patients with class III correction with clockwise rotation of the maxillomandibular complex without maxillary advancement were included, while those with genioplasty were excluded. Various facial skeletal cephalometric landmarks were measured through artificial intelligence based cephalometric analysis software. The gearing effect was determined by dividing the lower anterior facial height (LAFH) in relatively short and long groups compared to those in the ANS‒PNS length. RESULTS: In a total of 29 patients, the amount of Menton setback between group 1 (n=15, short LAFH) and group 2 (n=14, long LAFH) was 1.67±0.66 and 2.74±0.99 mm per 1 mm of PNS impaction, respectively (p=0.002), and 1.58(interquartile range(IQR) 0.78) and 1.95(IQR 1.05) mm per 1° clockwise rotation of palatal angle, respectively (p=0.007). The convexity of the A point was improved without any significant change in the SNA angle before and after surgery. CONCLUSIONS: This article addressed the scientific evidence in impact of clockwise rotational orthognathic surgery based on the gearing effect. Considering the gearing effect, the mandibular setback turned out to be more effective in patients with a long LAFH.

Differences in the stability of the lesser and greater maxillary segments after cleft orthognathic surgery: A retrospective study using 3D analysis.

The aim of this study was to determine whether significant differences in postoperative stability exist between the lesser and the greater maxillary segments after cleft orthognathic surgery in patients with and without residual alveolar cleft. A retrospective study of orthognathic patients with unilateral cleft was conducted. The patients were divided into two groups according to maxillary status before surgery, with group 1 comprising single-piece maxilla and group 2 comprising two-piece maxilla. Four maxillary points were used for intra- and intergroup comparisons of movements and relapses between the two maxillary segments. In total, 24 patients were included. The intragroup comparison showed significant differences in vertical relapses between lesser and greater segments in both group 1 (anterior, p = 0.004 and posterior, p = 0.01) and group 2 (posterior, p = 0.013). With regard to intergroup comparison, the lesser segments in the two groups differed in transverse movements (anterior, p = 0.048) and relapses (posterior; p = 0.04), while the greater segments differed in transverse movements (anterior, p = 0.014 and posterior, p = 0.019), with significant differences in relapses anteriorly (vertical, p = 0.031 and sagittal, p = 0.036) and posteriorly (transverse, p = 0.022). Maxillary changes following cleft orthognathic surgery showed significant differences between the lesser and the greater segments. These findings imply that 3D images should be used to assess each maxillary segment separately with regard to planning and outcome evaluation.

Surgery-First Orthognathic Approach to Correct Facial Asymmetry: Artificial Intelligence-Based Cephalometric Analysis.

BACKGROUND: The surgery-first orthognathic approach has been applied at our institution since 2007. However, its indications remain debated. The aim of this study was to investigate the reliability of the surgery-first approach to correct facial asymmetry compared to the traditional orthodontics-first approach using a novel artificial intelligence-based cephalometric analysis. METHODS: Intervention outcomes of surgery-first (n = 33) and orthodontics-first (n = 26) approaches to correct facial asymmetry were examined. Patients with facial asymmetry who had undergone orthognathic surgery from January of 2006 to January of 2019 were included in the study. In the surgery-first approach, the novel preoperative simulation process on the dental model was performed to determine the final occlusion without presurgical orthodontic treatment. Changes in cephalometric landmarks were compared using the supervised deep learning process developed at our institution. RESULTS: The surgery-first approach without presurgical orthodontic treatment corrected facial asymmetry and yielded results similar to those of the traditional orthognathic approach. The statistical analysis revealed that changes in skeletal cephalometric landmarks were similar in the two groups. CONCLUSIONS: The surgery-first orthognathic approach without presurgical orthodontic treatment treated facial asymmetry, possibly suggesting a possible paradigm shift in treatment. In addition, artificial intelligence-based cephalometric analysis was an effective tool. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Surgery-first orthognathic approach for the correction of facial asymmetry.

We aimed to compare the reliability of the surgery-first approach and the traditional orthodontic-first approach for the correction of facial asymmetry based on the new classification of facial asymmetry. Patients with facial asymmetry who underwent orthognathic surgery between January 2016 and January 2019 were included. Cephalometric changes and relapse ratios were analyzed 12 months before and after surgery. Patients were divided into horizontal and vertical asymmetry groups based on the asymmetry vector, and subgroup analysis was conducted. The surgery-first approach without presurgical orthodontic treatment and the orthodontic-first approach showed a similar degree of asymmetry correction and skeletal stability. The relapse ratios of the maxilla height in the surgery-first and orthodontic-first groups were 0.25 ± 0.21 and 0.27 ± 0.25, respectively (p = 0.63), the relapse ratios of the maxilla width were 0.31 ± 0.32 and 0.21 ± 0.2, respectively (p = 0.14), the mandibular height relapse ratios were 0.34 ± 0.58 and 0.29 ± 0.36, respectively (p = 0.69), and the mandibular width relapse ratios were 0.12 ± 0.22 and 0.26 ± 0.31, respectively (p = 0.058). The treatment period of the surgery-first group (18.5 ± 5.3 months) was significantly shorter than that of the orthodontic-first group (22.9 ± 7.5 months, p = 0.024). Among the surgery-first group, patients with vertical asymmetry (15.0 ± 3.2 months) had a shorter treatment than those with horizontal asymmetry (21.6 ± 6.8 months, p = 0.006). Although contesting traditional standards is always challenging, the surgery-first orthognathic approach may lead to a new era in traditional orthognathic approaches. This new classification of facial asymmetry could be useful and practical when treating patients with facial asymmetry regardless of the etiology.

Current concept of the surgery-first orthognathic approach.

Traditional orthognathic surgery has long been performed after presurgical orthodontic treatment. Despite some concerns, the surgery-first orthognathic approach (SFOA) or surgery-first approach (SFA) without presurgical orthodontic treatment has gradually gained popularity. In recent years, several articles dealing with the concepts of the SFA have been published worldwide. However, the SFA has not yet been standardized, and many surgeons use slightly different protocols and concepts. This review article discusses the beginning and evolution of the SFA and its current concepts, including some opinions based on the authors' clinical experiences over the last 15 years. According to recent investigations, the SFA could be applied effectively in several situations including class III malocclusion, class II malocclusion, and facial asymmetry. However, debate on the SFA continues and many issues remain to be resolved. This review article addresses the current issues regarding the SFOA, including its advantages and disadvantages, as well as its indications and contraindications. The authors summarize various aspects of the SFA and expect that this review article will help surgeons and orthodontists better understand the current status of the SFA.

Counterclockwise Rotational Orthognathic Surgery for the Obstructive Sleep Apnea in Class II Dentofacial Deformity: Polysomnography and 3D Computed Tomographic Analysis.

ABSTRACT: Traditionally, maxillomandibular advancement is an orthognathic surgical procedure that has been used to manage obstructive sleep apnea in patients not able or willing to maintain adherence to continuous positive airway pressure therapy or for patient who are not able to adhere to treatment. However, maxillomandibular advancement often leads to unsatisfactory cosmetic results.This prospective study investigated functional and esthetic outcomes using polysomnography and 3-dimensional computed tomography, after counterclockwise rotational orthognathic surgery. We enrolled 17 patients with obstructive sleep apnea, who underwent orthognathic surgery at single institution between March 2013 and December 2018.After 12 months, the patients' mean self-rated score for facial appearance, using a 10-step visual analog scale, was 7.36. The preoperative apnea-hypopnea index and respiratory disturbance index were 34.70 and 37.45, respectively; postoperative indices were 11.60 and to 12.69, respectively (P = 0.003, 0.003). The mean posterior pharyngeal airway space increased from 5357.88 mm3 preoperatively to 8481.94 mm3 after 6 postoperative months.Counterclockwise rotational orthognathic surgery for the correction of obstructive sleep apnea turned out to be the ideal solution not only in the correction of the sleep apnea, but also in the facial esthetics.

Three-dimensional Photogrammetric Analysis of Facial Soft-to-Hard Tissue Ratios After Bimaxillary Surgery in Facial Asymmetry Patients With and Without Sturge-Weber Syndrome.

Sturge-Weber syndrome (SWS) is a rare neurocutaneous syndrome characterized by facial port-wine stains. Most patients with facial asymmetry due to SWS have soft and/or hard tissue hypertrophy and require both soft tissue correction and bone surgery. In our experience, because SWS patients are more likely than non-SWS patients to be dissatisfied after bone surgery because of limited soft tissue change, we compared soft tissue changes after bimaxillary surgery between facial asymmetry patients with and without SWS.All patients-5 with SWS and 5 without SWS-underwent bimaxillary surgery by a single surgeon. Soft-to-hard ratios were determined using the preoperative and postoperative vertical lengths from the intersection point between the external orbital contour laterally and the oblique orbital line (LO) to the occlusion line (OL) and the LO to the mandible angle (AG) on cephalography and the distances between the lateral canthus (LC) and oral commissure (OC) and between the LC and soft tissue gonion (Go') on 3-dimensional scanned images.The average change in the [LC-OC] to [LO-OL] ratio was 23.03% ± 10.09% in SWS patients and 88.05% ± 10.44% in non-SWS patients (P = 0.008). The average change in the [LC-Go'] to [LO-AG] ratio was 35.54% ± 15.47% in SWS patients and 78.90% ± 47.56% in non-SWS patients (P = 0.032).Soft-to-hard tissue ratios after orthognathic surgery are significantly smaller in SWS patients than in non-SWS patients. This information is important for preoperative patient counseling, managing patient expectations, enhancing results, and planning the second-stage soft tissue surgery.

Large-Scale Study of Long-Term Vertical Skeletal Stability in a Surgery-First Orthognathic Approach Without Presurgical Orthodontic Treatment: Part II.

The surgery-first approach (SFA) is a new paradigm in orthognathic surgery. In our experience over the last 10 years, SFA, particularly for the correction of the class III dentofacial deformity and facial asymmetry, has demonstrated high success rates without any major complications. However, many craniofacial surgeons remain concerned about the skeletal stability of SFA. In the present study, the authors aimed to compare the traditional and SFA with regard to the long-term outcomes of vertical skeletal stability using large-scale data. The authors enrolled patients with skeletal class III dentofacial deformities who had undergone and completed orthognathic surgery between December 2007 and December 2015. The inclusion criteria were based on the presurgical simulation of the dental model, and the authors predicted the potential of the SFA based on this preoperative simulation model. Patients with cleft-related syndromes, and those who had undergone orthognathic surgeries for facial asymmetry or class II deformity were excluded. A total of 104 and 51 class III patients were enrolled in the surgery-first and traditional orthodontics-first groups, respectively. Satisfactory results were achieved in all 155 patients with dentofacial deformity. The initial preoperative measurements of cephalometric analysis, particularly vertical skeletal stability, were similar and well maintained after the procedure in both groups. In conclusion, the SFA without any presurgical orthodontic treatment for correcting dentofacial deformities can achieve similar long-term vertical stability results to the orthodontic treatment-first approach.

Large-Scale Study of Long-Term Anteroposterior Stability in a Surgery-First Orthognathic Approach Without Presurgical Orthodontic Treatment.

Presurgical orthodontic treatment has long been known as a prerequisite in the traditional orthognathic approach. However, achieving ideal decompensation is very difficult even in the presurgical orthodontic period. For minimization of this problem, the surgery-first orthognathic concept has been introduced. The authors hypothesized that this treatment modality will be feasible for skeletal class III dentofacial deformity patients. In this study, the authors tried to compare the traditional and surgery-first approaches regarding long-term outcomes in terms of stability, based on large-scale data. The patients included in this study had skeletal class III dentofacial deformities, and all underwent, and completed, orthognathic surgery between December 2007 and December 2015. The inclusion criteria were based on presurgical simulation on the dental model, and the authors predicted the potential of the surgery-first approach by this preoperative simulation model. Patients with cleft-related syndromes, those who underwent orthognathic surgeries due to facial asymmetry or class II deformity were excluded from the study. In total, 104 class III patients were enrolled in the surgery-first group and 51 class III patients in the traditional orthodontic-first group. Satisfactory results were achieved in all 155 patients with dentofacial deformity in this study. Overall, the analysis revealed that anteroposterior skeletal long-term stability in the surgery-first approach was not different, statistically or otherwise, from that in the orthodontic-first approach. Anteroposterior skeletal stability was maintained well in the surgery-first approach. In conclusion, surgery-first approach without presurgical orthodontic treatment can achieve similar results of long-term anteroposterior stability in correcting dentofacial deformities as the orthodontic treatment-first approach.

Can a surgery-first orthognathic approach reduce the total treatment time?

Although pre-surgical orthodontic treatment has been accepted as a necessary process for stable orthognathic correction in the traditional orthognathic approach, recent advances in the application of miniscrews and in the pre-surgical simulation of orthodontic management using dental models have shown that it is possible to perform a surgery-first orthognathic approach without pre-surgical orthodontic treatment. This prospective study investigated the surgical outcomes of patients with diagnosed skeletal class III dentofacial deformities who underwent orthognathic surgery between December 2007 and December 2014. Cephalometric landmark data for patients undergoing the surgery-first approach were analyzed in terms of postoperative changes in vertical and horizontal skeletal pattern, dental pattern, and soft tissue profile. Forty-five consecutive Asian patients with skeletal class III dentofacial deformities who underwent surgery-first orthognathic surgery and 52 patients who underwent conventional two-jaw orthognathic surgery were included. The analysis revealed that the total treatment period for the surgery-first approach averaged 14.6 months, compared with 22.0 months for the orthodontics-first approach. Comparisons between the immediate postoperative and preoperative and between the postoperative and immediate postoperative cephalometric data revealed factors that correlated with the total treatment duration. The surgery-first orthognathic approach can dramatically reduce the total treatment time, with no major complications.

Stability of pre-orthodontic orthognathic surgery depending on mandibular surgical techniques: SSRO vs IVRO.

The aim of this retrospective cohort study was to evaluate the postoperative stability of sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO) in pre-orthodontic orthognathic surgery (POGS) for skeletal Class III malocclusion. Thirty-seven patients (SSRO, n = 18; IVRO, n = 19) who underwent bimaxillary surgery were divided into two groups according to the type of surgery. During the postoperative period, there were no significant differences in anterior and superior movements of the mandible at point B between the two groups, but occlusal plane angle of the SSRO group significantly decreased more than that of the IVRO group (P = 0.003). Only the SSRO group showed a linear relationship between the amount of postoperative horizontal and vertical movements of the mandible (R(2) = 0.254; P = 0.033), indicating that the amount of postoperative upward movement of the mandible increased as the amount of postoperative forward movement increased (r = -0.504; P = 0.033). The mandible after SSRO in POGS rotated counterclockwise due to rigid fixation between two segments, whereas the mandible after IVRO without rigid fixation in POGS moved mainly in a superior direction. These differences must be considered before surgery to ensure postsurgical stability for patients with mandibular prognathism.

The reliability of a surgery-first orthognathic approach without presurgical orthodontic treatment for skeletal class III dentofacial deformity.

BACKGROUND: Orthognathic surgery with presurgical and postsurgical orthodontic treatment is the most widely accepted method for the correction of skeletal or dentoalveolar malocclusion. However, recent advancements in presurgical orthodontic simulations and postsurgical orthodontic treatments using miniscrews have shown remarkable stability and control of the occlusion after orthognathic surgery. Thus, we have adopted a surgery-first orthognathic approach without presurgical orthodontic treatment, based on a novel presurgical simulation process using a dental model. We hypothesized that this treatment modality will be feasible for skeletal class III dentofacial deformity patients. MATERIALS AND METHODS: This prospective study investigated intervention outcomes in 24 standard and 32 surgery-first approaches for patients with skeletal class III dentofacial deformity. The patients underwent orthognathic surgery between December 2007 and July 2010. In the surgery-first approach, a dental model was created and a novel preoperative orthodontic simulation of the standard presurgical orthodontic treatment was performed to determine the final occlusion between the maxilla and mandible. Changes in cephalometric landmarks were compared between the standard and surgery-first groups in the preoperative, immediate postoperative, and postoperative periods. The Student t test, Kruskal-Wallis test, and a linear mixed model were used for statistical analysis. RESULTS: The follow-up period ranged from 12 to 36 months (average, 20.5 months). The average age of the patients was 22.4 years, with 16 male and 40 female patients. We found that a surgery-first approach without presurgical orthodontic treatment is possible and can give similar results to standard orthognathic surgery. The statistical analysis showed that changes in skeletal cephalometric landmarks were similar between the surgery-first and standard approach groups, according to each period. However, the cephalometric landmarks relating to the dental component showed changes between treatment groups at different time points but similar final values. This suggests that the benefits of postsurgical orthodontic treatment after the surgery-first approach could be similar to those obtained via the standard approach. CONCLUSIONS: The surgery-first orthognathic approach without presurgical orthodontic treatment was found to be predictable and applicable to treat class III dentofacial deformities, and we recommend consideration of the technique as an effective alternative for treating this condition.

Frontal soft tissue analysis using a 3 dimensional camera following two-jaw rotational orthognathic surgery in skeletal class III patients.

Although two dimensional cephalometry is the standard method for analyzing the results of orthognathic surgery, it has potential limits in frontal soft tissue analysis. We have utilized a 3 dimensional camera to examine changes in soft tissue landmarks in patients with skeletal class III dentofacial deformity who underwent two-jaw rotational setback surgery. We assessed 25 consecutive Asian patients (mean age, 22 years; range, 17-32 years) with skeletal class III dentofacial deformities who underwent two-jaw rotational surgery without maxillary advancement. Using a 3D camera, we analyzed changes in facial proportions, including vertical and horizontal dimensions, facial surface areas, nose profile, lip contour, and soft tissue cheek convexity, as well as landmarks related to facial symmetry. The average mandibular setback was 10.7 mm (range: 5-17 mm). The average SNA changed from 77.4° to 77.8°, the average SNB from 89.2° to 81.1°, and the average occlusal plane from 8.7° to 11.4°. The mid third vertical dimension changed from 58.8 mm to 57.8 mm (p = 0.059), and the lower third vertical dimension changed from 70.4 mm to 68.2 mm (p = 0.0006). The average bigonial width decreased from 113.5 mm to 109.2 mm (p = 0.0028), the alar width increased from 34.7 mm to 36.1 mm (p-value = 0.0002), and lip length was unchanged. Mean mid and lower facial surface areas decreased significantly, from 171.8 cm(2) to 166.2 cm(2) (p = 0.026) and from 71.23 cm(2) to 61.9 cm(2) (p < 0.0001), respectively. Cheek convexity increased significantly, from 171.8° to 155.9° (p = 0.0007). The 3D camera was effective in frontal soft tissue analysis for orthognathic surgery, and enabled quantitative analysis of changes in frontal soft tissue landmarks and facial proportions that were not possible with conventional 2D cephalometric analysis.

Fabrication of lingual orthodontic appliances: past, present and future.

Lingual orthodontics is increasing in popularity, with more adults receiving orthodontic treatment and opting for truly invisible appliances that do not have any limitations on the type of tooth movement they can achieve. In addition, there are a growing number of children receiving lingual appliances as they have been shown to significantly reduce the incidence of decalcification. Combining this growth in popularity with advances in computer technology, it is possible to treatment plan, design the appliance and have it custom made all with the click of a button. This article highlights the different methods that have been utilized in the fabrication of lingual appliances.

Development of endovascular vibrating polymer actuator probe for mechanical thrombolysis: in vivo study.

In this study, we propose a new method for the enhancement of intraarterial thrombolysis by use of an endovascular vibrating polymer actuator probe (VPAP), which is fabricated from an ionic polymer metal composite (IPMC) actuator. The endovascular VPAP was fabricated by combining 0.8 × 0.8 × 10 mm3 IPMC samples, 0.22 mm × 50 cm copper wires, and 40 cm of Teflon tube. The purpose of this study was to evaluate the thrombolysis efficiency of an endovascular VPAP in a dog model. Both renal arteries of the enrolled dogs (n = 5) were used in the current study. A distal portion of the renal artery in a mongrel dog was occluded by a blood clot from autologous venous whole blood. Intraarterial thrombolysis was performed by use of a VPAP without the actuation force (control group), by a VPAP-only (VPAP-only group), or with a combination of recombinant tissue plasminogen activator (rtPA) and a VPAP (VPAP + rtPA group). The thrombolysis efficiency was evaluated by the modified Thrombolysis in Myocardial Infarction (TIMI) grading system based on the consensus between two radiologists. The grading scales were compared according to each intraarterial thrombolysis method. The VPAP + rtPA and VPAP-only groups showed a significantly higher thrombolysis efficiency than did the control group (p < 0.05). The VPAP-only group also showed a significantly higher thrombolysis efficiency than did the control group (p < 0.05). The VPAP+ rtPA group showed a significantly higher thrombolysis efficiency than did the VPAP-only group (p < 0.05). The use of an endovascular VPAP was a feasible and useful method for intraarterial thrombolysis, and it enhanced the thrombolysis efficiency when combined with the thrombolytic agent rtPA.

Development of endovascular vibrating polymer actuator probe for mechanical thrombolysis: a phantom study.

In this study, we propose a new method for enhancement of intraarterial thrombolysis using an ionic polymer-metal composite (IPMC) actuator. The purpose of this study was to test the mechanical thrombolysis efficiency of IPMC actuators and evaluate the endovascular vibrating polymer actuator probe for mechanical thrombolysis in a phantom model; 2 × 1 × 15 mm (2 mm in width, 1 mm in thickness, and 15 mm in length) and 0.8 × 0.8 × 10 mm (0.8 mm in width, 0.8 mm in thickness, and 10 mm in length) IPMC actuators were fabricated by stacking five and four Nafion-117 films, respectively. We manufactured the endovascular vibrating polymer actuator probe, for which thrombolysis efficiency was tested in a vascular phantom. The phantom study using 2 × 1 × 15 mm IPMC actuators showed that 5 Hz actuation is the optimal frequency for thrombolysis under both 2 and 3 V, when blood clot was not treated with rtPA, and when exposed to rtPA, IPMC actuators under the optimized condition (3 V, 5 Hz, and 5 min) significantly increased the thrombolysis degree compared with control and other experimental groups (p < 0.05). In addition, 0.8 × 0.8 × 10 mm IPMC actuators also revealed a significantly higher thrombolysis degree under the optimized condition than the control and rtPA only groups (p < 0.05). Finally, the fabricated probe using 0.8 × 0.8 × 10 mm IPMC actuators also incurred higher thrombolysis degree under the optimized condition than the control and rtPA only groups (p < 0.05). A vibrating polymer actuator probe is a feasible device for intravascular thrombolysis, and further study in an animal model is warranted.

Choice of graft material in relation to maxillary sinus width in internal sinus floor augmentation.

PURPOSE: When grafts with solely osteoinductive or osteoconductive effects are used in the maxillary sinus, the medial wall of the sinus membrane should be reflected to receive the vascular supply and the osteoconductive effect. Because the internal sinus floor augmentation is a blind technique, it is impossible to directly verify whether the medial sinus wall is reflected in the operation. The purpose of this study is to describe the modality of choice among the grafting materials and techniques in relation to the width of the maxillary sinus through preoperative planning and measuring in computed tomography (CT) images. PATIENTS AND METHODS: In a total of 57 patients, 100 implants were placed by 3 different sinus floor augmentation techniques. Postoperative cone-beam CT (CBCT) scans were performed and the arrival distance of grafts from lateral wall to medial wall at the apical end level of the implant in the maxillary sinus was measured. RESULTS: Buccolingual arrival distances of grafts were measured to be a mean of 12.1 mm +/- 2.0 in postoperative CT images. In 23 of 77 cases (29.9%) in which distances were greater than 12.1 mm, the grafts made contact with the medial wall. However, in 22 of 23 cases (95.7%) in which distances were less than 12.1 mm, the grafts made complete contact with the medial wall. CONCLUSIONS: The buccolingual width of the maxillary sinus should be measured at the apical end level of the implant that will be placed in preoperative CT. In the internal sinus floor augmentation, grafting materials with solely osteoconductive potential are to be used for narrow sinuses. For large sinuses, autogenous bone with osteogenic potential should be used; alternatively, the reflection of the medial wall by the lateral window technique is recommended.

Radiation-grafted fluoropolymers soaked with imidazolium-based ionic liquids for high-performance ionic polymer-metal composite actuators.

On purpose to develop a polymer actuator with high stability in air-operation as well as large bending displacement, a series of ionic polymer-metal composites (IPMC) was constructed with poly(styrene sulfonate)-grafted fluoropolymers as ionomeric matrix and immidazolium-based ionic liquids (IL) as inner solvent. The prepared IPMC actuators exhibited greatly enhanced bending displacement compared to Nafion-based actuators. The actuators were stable in air-operation, maintaining initial displacement for up to 10(4) cycles or 24 h. Investigating the material parameters and morphology of the IPMCs, high ion exchange capacity of the ionomers resulted in high ion conductivity and robust electrode of IPMC, which synergistically contributed to the high bending performance.

Three-dimensional facial imaging: accuracy and considerations for clinical applications in orthodontics.

This study determined the accuracy of a camera system capable of recording three-dimensional facial images. A Rainbow 3D Camera Model 250 system (Genex Technologies Inc, Kensington, Md) was used to capture images of specific models: (1) a precalibrated precision model and (2) a mannequin model that served to simulate the human condition. To assess the accuracy of the camera system, repeated images of both models were recorded at two time points, one week apart. Repeated measurements of specific distances were recorded directly on the models and from each image. Means and standard deviations were calculated for all the repeated measurements at each time point. A two-tailed t-test was used to test for significant differences between (1) each distance measured directly on the precision model and the same distance measured on the images of the precision model, (2) each distance measured directly on the mannequin and the same distance measured on the images of the mannequin, and (3) the mean differences between the same distances measured at the two times. The findings showed that substantial image distortion occurred when images of sharp angles (90 degrees) were captured. Also, those images captured from the frontal perspective +/- 15 degrees were the most accurate.