Internal porosities,retentive force,and survival of cobalt–chromium alloy clasps fabricated by selective laser-sintering

PurposeThe purpose of this study was to evaluate internal porosities, retentive force values and survival of cobalt–chromium (Co–Cr) alloy clasps fabricated by direct metal laser-sintering (DMLS) and compare them to conventionally cast clasps.MethodsEmbrasure clasps were digitally designed fitting teeth 35 and 36 on identical metal models (N = 32). Sixteen clasps were fabricated using DMLS (group DMLS) and another sixteen clasps were additively manufactured from wax and then cast from a Co–Cr alloy (group CAST). Internal porosities were examined using micro-focus X-ray (micro-CT) and analyzed applying Kolmogorov–Smirnov test, Mann–Whitney test, and T test (significance level: p < 0.050). A universal testing machine was used to determine the retentive force values at baseline and after 1095, 5475, 10,950 and 65,000 cycles of simulated aging. Data were analyzed employing Kolmogorov–Smirnov test, one-way ANOVA, and Scheffé’s post-hoc test (significance level: p < 0.050). Survival was estimated for 65,000 cycles of artificial aging using Kaplan–Meier analysis.ResultsMicro-CT analysis revealed a higher prevalence (p < 0.001), but a more homogeneous size and a significantly smaller mean (p = 0.009) and total volume (p < 0.001) of internal porosities for group DMLS. The groups showed mean initial retentive force values of 13.57 N (CAST) and 15.74 N (DMLS), which significantly declined over aging for group CAST (p = 0.003), but not for group DMLS (p = 0.107). Survival was considerably higher for group DMLS (93.8%) than for group CAST (43.8%) after 65,000 cycles of aging.ConclusionsClasps made by laser-sintering could be an alternative to conventional cast clasps for the fabrication of removable partial denture frameworks.     

Single leg aerobic capacity and strength in individuals with surgically repaired anterior cruciate ligaments

ObjectivesCompare single-leg aerobic capacity and strength differences between the surgically repaired ACL leg (injured) and the uninjured leg.DesignCross-sectional study.SettingLaboratory.ParticipantsEight participants (5 female, 3 male, age = 23 ± 3.5 y, mass = 72.3 ± 17.3 kg, height = 169.7 ± 9.4 cm) that returned to play from ACL surgery between six and 18 months.Main outcome measuresParticipants performed an aerobically-based, single-leg cycling protocol to determine maximum oxygen consumption, ventilatory threshold, heart rate, rating of perceived exertion, and maximal watts cycled. Participants also performed isokinetic knee flexion and extension on a dynamometer to assess peak torque, total work, work fatigue, and power.ResultsThere were no statistical differences in single-leg aerobic capacity or strength outcomes between the injured and uninjured legs.ConclusionsIndividuals who have had an ACL surgically repaired six to 18 months after return to play do not appear to have aerobic capacity or strength deficits between the injured leg and uninjured leg.     

Analysis of landing performance and ankle injury in elite British artistic gymnastics using a modified drop land task: A longitudinal observational study

ObjectivesTo determine whether differences in landing force and asymmetry of landing force exist between gymnasts at the time of data collection versus those that subsequently experienced an ankle injury 12-months later.Study designProspective longitudinal observational design with baseline measures and 12 month follow up.SettingBritish Gymnastics National Training Centre.ParticipantsThirty-two asymptomatic elite level gymnasts from three artistic gymnastic squads (n = 15 senior female, n = 10 junior female and n = 7 senior male).Main outcome measuresA modified drop land task was used to quantify measures of landing performance. Peak Vertical Ground Reaction Force (PVGRF) was used to measure landing force. The level of inter-limb asymmetry of landing force was calculated using the Limb Symmetry index (LSI). Other measures included injury incidence and percentage coefficient of variation (% CV).ResultsThere was no statistical difference for landing force (p = 0.481) and asymmetry of landing force (p = 0.698) when comparing injured and non-injured gymnasts. Most participants (69%) demonstrated inter-limb asymmetry of landing forces.ConclusionsOur findings observed inter-limb asymmetry of landing force in injured gymnasts, although uninjured gymnasts also exhibited asymmetry of landing force. Both magnitude of landing force and inter-limb asymmetries of landing force failed to identify the risk of ankle injury.     

Accelerations relevant to blunt trauma: theory and data

Maximum acceleration and the Head Injury Criterion (HIC) are both used as indicators of likely head injury severity. A dataset has previously been published of impacts of an instrumented missile on four ground surfaces having a layer of between 0 and 16 cm of sand. The dataset is compared with recently-developed theory that predicts power-function dependence of maximum acceleration and HIC on drop height. That prediction was supported by the data. The surfaces differed in respect of the exponents estimated.     

Treatment of skeletal open bite using a navigation system: CAD/CAM osteotomy and drilling guides combined with pre-bent titanium plates

Severe skeletal open bite associated with posterior vertical maxillary excess and mandibular deformity is considered a difficult problem in orthodontic and surgical treatment. This study used a navigation system for the correction of severe skeletal open bite in order to accurately transfer the virtual plan to the actual operation and achieve precise rigid internal fixation in bimaxillary osteotomies of the jaws. Twelve patients with a severe skeletal open bite associated with vertical maxillary excess and mandibular deformity were recruited. All patients underwent Le Fort I osteotomy and bilateral sagittal split ramus osteotomy with the guidance of this navigation system. Computed tomography and cephalometric examinations were performed to evaluate the correction of the deformity. Deviations between the simulated plan and actual postoperative outcome were measured to determine the precision of the surgery. Satisfactory and stable results were achieved in all patients postoperatively, without complications or relapse during follow-up. Photographs and cephalometric evaluations showed that the facial profile and occlusion were improved. Assessment of the deviations between the simulated plan and actual postoperative outcome showed that the navigation system can precisely transfer the virtual plan to the actual operation. The results suggest that the navigation system can accurately transfer the virtual plan to the actual operation during bimaxillary jaw osteotomies, without relapse, in patients with a severe skeletal open bite.     

DryEyeRhythm: A reliable and valid smartphone application for the diagnosis assistance of dry eye

PurposeUndiagnosed or inadequately treated dry eye disease (DED) decreases the quality of life. We aimed to investigate the reliability, validity, and feasibility of the DryEyeRhythm smartphone application (app) for the diagnosis assistance of DED.MethodsThis prospective, cross-sectional, observational, single-center study recruited 82 participants (42 with DED) aged ≥20 years (July 2020–May 2021). Patients with a history of eyelid disorder, ptosis, mental disease, Parkinson's disease, or any other disease affecting blinking were excluded. Participants underwent DED examinations, including the Japanese version of the Ocular Surface Disease Index (J-OSDI) and maximum blink interval (MBI). We analyzed their app-based J-OSDI and MBI results. Internal consistency reliability and concurrent validity were evaluated using Cronbach's alpha coefficients and Pearson's test, respectively. The discriminant validity of the app-based DED diagnosis was assessed by comparing the results of the clinical-based J-OSDI and MBI. The app feasibility and screening performance were evaluated using the precision rate and receiver operating characteristic curve analysis.ResultsThe app-based J-OSDI showed good internal consistency (Cronbach's α = 0.874). The app-based J-OSDI and MBI were positively correlated with their clinical-based counterparts (r = 0.891 and r = 0.329, respectively). Discriminant validity of the app-based J-OSDI and MBI yielded significantly higher total scores for the DED cohort (8.6 ± 9.3 vs. 28.4 ± 14.9, P < 0.001; 19.0 ± 11.1 vs. 13.2 ± 9.3, P < 0.001). The app's positive and negative predictive values were 91.3% and 69.1%, respectively. The area under the curve (95% confidence interval) was 0.910 (0.846–0.973) with concurrent use of the app-based J-OSDI and MBI.ConclusionsDryEyeRhythm app is a novel, non-invasive, reliable, and valid instrument for assessing DED.