Aim: Functional appliances such as TWIN blocks are widely used to treat skeletal Cl II malocclusions. Myofunctional effects are one of the critical features of these appliances. The present study aimed to investigate the muscular effects of clear and traditional TWIN blocks.Methods: In this randomized clinical trial, 60 skeletal Class II div 1 patients were randomly divided into two groups: clear TWIN block (CTB) and traditional TWIN block (TTB). Electromyographic (EMG) evaluation of masseter, anterior temporalis, orbicularis oris, and mentalis muscles was carried out during deglutition, rest, whistling, and forced occlusion before insertion (T1) and six months (T2) after insertion of the appliance. Data were analyzed using independent t-test, paired t-test, and Wilcoxon’s signed-rank test at the 0.05 significance level.Results: There were no significant differences in T2 values between the groups (P>0.05). The intragroup comparisons showed a significant change from T1 to T2 in the CTB group for the clenching of the masseter muscle and in the TTB group for swallowing and rest position of the anterior temporalis muscle and swallowing of the masseter muscle (P<0.05).Conclusion: Both CTB and TTB changed the muscular activity of circumoral muscles. No significant difference was found when the post-treatment muscular activity of the two groups was compared.

According to the Einstein’s special theory of relativity in physics, the TWIN paradox, which explores the concept of time dilation, is a thought experiment involving identical TWINs. One of the TWINs’ journeys into space in a high-speed spacecraft and returns to Earth to find that the TWIN who stayed at home has aged more than the TWIN who made the high-speed journey in space. This seemingly contradictory result can be explained by the fact that time passes more slowly for an object in motion than for one at rest, a consequence of Einstein’s theory of special relativity. Thus, the passage of time is relative to the observer’s frame of reference and is affected by their relative motion.

Dear Editor, I would like to present a case entitled “ Massive hydrocephalus and intraventricular hemorrhage (IVH) in monochorionic diamniotic (MCDA) TWIN pregnancy with TWIN‑ TWIN transfusion syndrome (TTTS) plus TWIN anemia‑ polycythemia sequence (TAPS). ”..

Background: Monochorionic diamniotic ,(MCDA) TWIN pregnancies are considered high‑, risk for several reasons, especially the risk of TWIN‑, to‑, TWIN transfusion syndrome ,(TTTS). Renal artery Doppler ,(RAD) is reported as a useful tool for predicting oligohydramnios in singleton pregnancies. We aimed to compare the RAD indices between MCDA TWINs with and without TTTS. Materials and Methods: In this case–, control study, all pregnant women aged 18–, 38 , years, with gestational age , ≥,  , 18 , weeks, who were referred to two Prenatal Clinics, Alzahra and Beheshti Educational Hospitals, affiliated to Isfahan University of Medical Sciences, Isfahan, Iran, October 2020–, March 2022 were enrolled,the women with MCDA TWIN pregnancies complicated by TTTS , (case group, n , = , 12) and without TTTS , (control group, n , = , 24). For each TWIN, biometric analysis, fetal weight, and Doppler study of fetal arteries, including RAD, middle cerebral artery , (MCA), umbilical artery, and ductus venosus were performed. Peak systolic velocity, Pulsatility index , (PI), resistance index , (RI), and systole/diastole , (S/D) were measured for all arteries. Results: The donors of the case group had a lower mean MCA S/D , (4. 48 , ±,  , 1. 89) than the control group , (6. 48 , ±,  , 1. 97) , (P , = , 0. 01) and higher mean umbilical parameters, including PI, RI, and S/D , (P , < , 0. 05). The recipients of the case group had a lower mean renal PI than the control , (P , = , 0. 008) and lower mean MCA PI, RI, and S/D , (P , < , 0. 05). The donor group had a higher mean umbilical RI and S/D than the recipient TWIN, while the mean fetal weight of the recipient group was higher , (P , < , 0. 05). Conclusion: Comparing the RAD parameters between the TWINs with and without TTTS in the present study did not identify significant results, which rejected the primary hypothesis. Among all RAD parameters, the only significant difference observed in the present study was the lower RAD PI in RT, which cannot suggest this measurement as a valuable tool for the prediction of TTTS in MCDA TWINs. Therefore, the results of the present study failed to show the additional value of RAD, compared with the conventional Doppler examination of fetal arteries. Further studies are required to prove this conclusion.

Limb bud first appears during the third week of gestation with the upper limb buds appearing a few days before the lower limb buds. Complete absence of one or more limbs, called Amelia, occurs prior to the eighth week of gestation. We report a case of Amelia in a TWIN gestation.