Use of Panicker’s cannula in management of atonic postpartum hemorrhage

Postpartum hemorrhage (PPH) is leading cause of maternal mortality worldwide. Panicker’s cannula creates negative pressure inside the uterus that causes shrinking of the uterus which can assist the physiological process of contraction and retraction to stop atonic postpartum hemorrhage. It is safe and simple technique to prevent and treat PPH. It can be used in low-resource and primary care settings, where even para medical personnel can use this method effectively to prevent morbidity and mortality. This can also be used in non-PPH conditions. In this study total 20 women with singleton pregnancy (14 had vaginal delivery and 6 underwent cesarean section), who developed atonic postpartum hemorrhage were included in the study. Panicker’s cannula was used in the patients, in whom bleeding was not stopped despite using uterotonics. Cessation of complete bleeding was observed in all 20 women within 4 minutes, which was associated with contraction and firm retraction of the uterus. Amount of the blood in bottle ranged from 150-250 ml. Vacuum retraction of uterus assists in the normal physiological process of contraction and retraction. This simple and cost effective technique, takes very little time to stop bleeding. This lifesaving technique is useful in all settings especially in low resource settings.

Research progress on the molecular genetics and neuroscience of congenital cranial dysinnervation disorders / 国际眼科杂志(Guoji Yanke Zazhi)

Congenital cranial dysinnervation disorders(CCDDs)are a group of diseases with congenital non-progressive developmental abnormalities or absence of one or more cranial nerves, resulting in primary or secondary abnormalities of cranial nerves innervating the extraocular muscles. CCDDs can be sporadic or hereditary, and may be accompanied by systemic abnormalities. In recent years, with the research progress of neuropathology, neuroimaging, and genetics, it has not only been clarified that the cause of eye movement disorder in CCDDs is neurogenic, but also been found the pathogenic genes of CCDDs, including SALL4, HOXA1, KIF21A, PHOX2A, TUBB3, and HOXB1, etc. In this review, the relevant domestic and international literatures on the molecular genetics and neuroscience of CCDDs in recent years are reviewed, aiming to address how the causing gene mutations of CCDDs affect brain neural development and further lead to congenital abnormal cranial nerve innervation, in order to provide references for the clinical and basic research of CCDDs.

Orthodontic treatment using segmental T loop for correction of ectopically erupting canine: a case report

Most of the patients approach the orthodontist with their prime issue being their appearance. The patient expects the treatment to improve their overall appearance which in turn increases the acceptance by their peers. A 14 year old female report with a chief complain of irregularly placed teeth in upper and lower front region of jaw. After detailed diagnosis her treatment was planned wherein over retained 53 was extracted followed by correction of buccally erupting 13 and correction of crowding and improvement in airway was achieved. Titanium molybdenum (TMA) segmental T loop was used to retract 13. Post-treatment records revealed that treatment objectives were achieved and patient was satisfied with the treatment.

Retracción dural percutánea en cirugías mínimamente invasivas de columna vertebral / Percutaneuos Dural Retracion in Minimally Invasive Spine Surgery

Introducción. El desarrollo de técnicas quirúrgicas mínimamente invasivas se considera un pilar esencial de la medicina moderna. La técnica de retracción dural percutánea espinal se presenta como una estrategia novedosa con la intención de contribuir a su adopción en el tratamiento de patologías intradurales. Objetivos. Describir la técnica quirúrgica de apertura dural percutánea para patologías intradurales espinales. Descripción de la técnica. Se trata de una técnica para la apertura dural primaria en la técnica mínimamente invasiva, permitiendo objetivarse con mayor perspectiva visual la medula espinal y el objetivo diana. Se realiza una descripción con imágenes del paso a paso. Conclusión. La exéresis de tumores raquídeos intradurales mediante abordajes tubulares es un procedimiento complejo. La misma se ve incrementada si debe realizarse a través de un ojal dural o apertura dural insuficiente. La retracción dural ampliada beneficia la visión del cirujano al exponer en mayor medida los tejidos intradurales

Background. The development of minimally invasive surgical techniques is considered an essential pillar of modern medicine. The percutaneous spinal dural retraction technique is presented as a novel strategy with the intention of contributing to its adoption in the treatment of intradural pathologies. Objectives. To describe the surgical technique of percutaneous dural opening for intradural spinal pathologies.Technique Description. It is a technique for primary dural opening with the minimally invasive technique, allowing the spinal cord and the target objective to be observed with a greater visual perspective. A description is made with step-by-step images. Conclusions. The excision of intradural spinal tumors through minimally invasive tubular approaches is a complex procedure. It is increased if it must be performed through a dural eyelet or insufficient dural opening. Extended dural retraction benefits the surgeon's vision by further exposing intradural tissues

Treatment of Multiple Gingival Recessions in Maxilla and Mandible: a Case Report / Tratamento de Recessões Gengivais Múltiplas em Maxila e Mandíbula: um Relato de Caso

This study aimed to report a treatment of multiple gingival recession in a 43-year-old female patient. After clinical and tomographic evaluation, Miller's class I and II (or Cairo RT1) gingival recessions were observed in several teeth of maxilla and mandible. Non-carious cervical lesions, poorly adapted crowns and unbalanced occlusion were also diagnosed, with the absence of canine guides. A thin gingival phenotype was also found. Orthodontic treatment was not performed, as a thin vestibular bone wall in the mandible was detected. Therefore, correction of the occlusion was performed by means of selective wear on cusps of the posterior teeth to relieve premature contacts. For root coverage, tunneling technique was used in the first, second and fourth sextants. In the fifth sextant, full covering occurred only after a second surgery. A third surgery was performed in the fourth quadrant, and the modified Bruno technique was chosen. The donor region was the palate in all the procedures. The two techniques employed reached up to 100% root coverage in all areas that received the surgery. The patient was satisfied with the final result. It was concluded that complete root coverage is possible when using tunneling technique in patients without interproximal bone loss. (AU)

Esse estudo objetivou reportar um tratamento de recessões gengivais múltiplas em uma paciente do sexo feminino de 43 anos. Após avaliação clínica e tomográfica, recessões gengivais classe I e II de Miller (ou RT1 de Cairo) foram observadas em diversos dentes da maxila e mandíbula. Lesões cervicais não cariosas, coroas mal adaptadas e oclusão desbalanceada também foram diagnosticadas, com ausência de guias caninas. Um fenótipo gengival fino foi observado. Tratamento ortodôntico não foi realizado, pois uma parede óssea vestibular fina na mandíbula foi detectada. Portanto, correção da oclusão foi realizada com desgastes seletivos de cúspides dos dentes posteriores para avaliar os contatos prematuros. Para o recobrimento radicular, técnica de tunelização foi utilizada no primeiro, secundo e quarto sextantes. No sexto sextante, recobrimento completo foi conseguido apenas após a segunda cirurgia. Uma terceira cirurgia foi realizada no quarto quadrante, e a técnica modificada de Bruno foi escolhida. O palato foi a região doara em todos os procedimentos. As duas técnicas cirúrgicas empregadas chegaram até a 100% de recobrimento radicular em todas as áreas que receberam a cirurgia. A paciente ficou satisfeita com o resultado final. Foi concluído que o recobrimento radicular complete é possível quando se utiliza a técnica da tunelização em pacientes sem perda óssea interproximal. (AU)

Finite Element Method Comparison of Biomechanics Between Labial and Lingual Orthodontics Involved in Canine Retraction

Background: FEM is a mathematical method in which the shape of complex geometric objects and their physical properties are computer-constructed. Physical interactions of the various components of the model can then be calculated in terms of stress and strain, detailed information which is difficult to obtain by any other experimental or analytical means due to the interaction of anatomical structures with the surrounding tissue.. The aim is to Comparison of biomechanical differences by FEM between labial and lingual orthodontic mechanotherapy involved in canine retraction. Material & Methods: ANSYS software was preferred over others for the analysis. As ANSYS can import computer assisted designing (CAD) data and also enables to build geometry , In the current study, we have shown the simulated individual (sequential) canine retraction using the sliding(friction method) mechanics by an elastic component. Sliding mechanics was preferred over the closing loop mechanics (frictionless method). Results: Stress in the PDL and Alveolar bone were calculated and depicted. Conclusion: On retraction, the high stress was produced with the Labial system in the PDL and alveolar bone that gradually reduced on force degradation. On combined force application slight increase in stress was noticed.

Clinical application of botulinum toxin type A in the treatment of thyroid-associated ophthalmopathy / 国际眼科杂志(Guoji Yanke Zazhi)

Thyroid-associated ophthalmopathy(TAO)is an autoimmune inflammatory disease involving multiple orbital tissues with a variety of clinical manifestations, which has serious effects on the life quality of patients.Interventions of TAO mainly include medical treatment to stabilize thyroid function, reduce inflammation and regulate immune function, as well as surgical treatment to relieve ocular symptoms. Botulinum toxin type A can paralyze muscles by blocking nerve impulse conduction at the neuromuscular junction, which is of certain therapeutic value for restrictive strabismus due to extraocular muscle involvement and upper eyelid retraction due to involvements of levator palpebrae superioris and Müller's muscle in TAO patients, especially when they have surgical contraindications, lack surgical opportunity, or refuse surgery. This paper reviews the application of botulinum toxin type A in the treatment of TAO, focusing on its pharmacological mechanism, dosage, effectiveness, and possible complications when treating restrictive strabismus and upper eyelid retraction, and discussing potential therapeutic values of botulinum toxin type A for intraocular pressure elevation, glabellar frown lines and dry eye caused by extraocular muscle compression in TAO patients, in order to provide a reference for clinical intervention.

Research progress on anterior alveolar bone changes after orthodontic treatment involving extractions / 口腔疾病防治

@#It has been traditionally believed that a 1:1 cortical bone remodeling/tooth movement ratio has been preserved during orthodontic treatment for tooth movement, with the alveolar bone on the tension side growing and the alveolar bone on the pressure side resorbing to maintain the balance of the alveolar bone. However, recent studies have shown that alveolar bone loss has been found in patients who have undergone orthodontic treatment, suggesting that the alveolar bone does not change as the teeth change over time. Whether the morphology of the alveolar bone will change when the anterior teeth are moved has been the clinical focus. The changes of anterior alveolar bone in patients who have undergone tooth extraction after orthodontic treatment were summerized by literature review in this paper. The results of the review showed that the alveolar bone at the lingual/palatal root-cervical site of the anterior root is more prone to bone loss after extensive movement of the anterior teeth. With the development of imaging technology, CBCT is now more commonly used for analysis instead of two-dimensional images for measurement, as its results are more accurate. However, there are few multifactorial studies in which CBCT has been used to assess the morphological changes in the alveolar bone. The focus of future research is to compare the long-term changes in the anterior alveolar bone of patients of different ages based on three-dimensional imaging, and to study the correlation between different skeletal features, tooth movement patterns and alveolar bone remodeling.

Quantitative grading evaluation of the therapeutic efficacy of asymmetric bilateral lateral rectus recession in type Ⅲ Duane retraction syndrome / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To quantitatively evaluate the therapeutic efficacy of the asymmetric recession of bilateral lateral rectus in patients with unilateral type III Duane retraction syndrome.METHOD:Retrospective analysis of clinical data. The clinical data of 12 cases of type III Duane retraction syndrome with unilateral lateral rectus recession were analyzed. All subjects had restricted internal rotation, with narrowing of the palpebral fissure and vertical deviation, and restricted external rotation with widening of the palpebral fissure. All patients had abnormal head positions. The degree of strabismus was measured while maintaining the head in a neutral position. Asymmetric recession of bilateral lateral rectus was selected based on the degree of strabismus of affected eye or 1～3mm longer, with a smaller recession and Y-splitting in the affected eye and a larger recession in the healthy eye.RESULT:The difference in the degree of strabismus in the healthy eyes before and after surgery was statistically significant(Z=-4.158, P<0.01), as was the difference in the degree of restricted internal rotation(Z=-2.640, P=0.008). The difference in the degree of restricted external rotation was not statistically significant(Z=-1.732, P=0.083). The difference in abnormal head position was statistically significant(Z=-4.181, P<0.01), while the difference in eyeball recession was not statistically significant(Z=-1.414, P=0.157). The difference in vertical deviation was statistically significant(Z=-3.115, P=0.002). A total of 10 patients(83%)had stereoscopic vision before surgery, and 11 patients(92%)had recovered stereoscopic vision after surgery, with a further improvement in stereoacuity in 50% of patients.CONCLUSION:Asymmetric recession of bilateral lateral rectus combined with Y-splitting of the affected lateral rectus can effectively improve the degree of strabismus, abnormal head position, vertical deviation and stereoacuity without aggravating the degree of restriction of external rotation or eyeball recession.

A Filipino child with schinzel-giedion syndrome

@#Schinzel-Giedion syndrome is a rare condition characterized by dysmorphic features, neurologic features, urogenital abnormalities, and radiographic changes. The etiology has been traced to mutations in the SETBP1 gene. We report a Filipino patient with features suggestive of Schinzel-Giedion Syndrome and the first to be confirmed through molecular testing.

An expandable chamber for safe brain retraction: new technologies in the field of transcranial endoscopic surgery / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Neurosurgery is a highly specialized field: it often involves surgical manipulation of noble structures and cerebral retraction is frequently necessary to reach deep-seated brain lesions. There are still no reliable methods preventing possible retraction complications. The objective of this study was to design work chambers well suited for transcranial endoscopic surgery while providing safe retraction of the surrounding brain tissue. The chamber is designed to be inserted close to the intracranial point of interest; once it is best placed it can be opened. This should guarantee an appreciable workspace similar to that of current neurosurgical procedures. The experimental aspect of this study involved the use of a force sensor to evaluate the pressures exerted on the brain tissue during the retraction phase. Following pterional craniotomy, pressure measurements were made during retraction with the use of a conventional metal spatula with different inclinations. Note that, although the force values necessary for retraction and exerted on the spatula by the neurosurgeon are the same, the local pressure exerted on the parenchyma at the edge of the spatula at different inclinations varied greatly. A new method of cerebral retraction using a chamber retractor (CR) has been designed to avoid any type of complication due to spatula edge overpressures and to maintain acceptable pressure values exerted on the parenchyma.

Analysis of the characteristics of retracted scientific papers in the field of global liver diseases published by Chinese scholars / 中华肝脏病杂志

Objective: To analyze the characteristics of scientific papers in the field of global liver diseases published by Chinese scholars that were retracted for diverse reasons from the Retraction Watch database, so as to provide a reference to publishing-related papers. Methods: The Retraction Watch database was retrieved for retracted papers in the field of global liver disease published by Chinese scholars from March 1, 2008 to January 28, 2021. The regional distribution, source journals, reasons for retraction, publication and retraction times, and others were analyzed. Results: A total of 101 retracted papers that were distributed across 21 provinces/cities were retrieved. Zhejiang area (n = 17) had the most retracted papers, followed by Shanghai (n = 14), and Beijing (n = 11). The vast majority were research papers (n = 95). The journal PLoS One had the highest number of retracted papers. In terms of time distribution, 2019 (n = 36) had the most retracted papers. 23 papers, accounting for 8.3% of all retractions, were retracted owing to journal or publisher concerns. Liver cancer (34%), liver transplantation (16%), hepatitis (14%), and others were the main areas of retracted papers. Conclusion: Chinese scholars have a large number of retracted articles in the field of global liver diseases. A journal or publisher chooses to retract a manuscript after investigating and discovering more flawed problems, which, however, require further support, revision, and supervision from the editorial and academic circles.

A modified fixation technique for the treatment of buried penis in children / 亚洲男科学杂志(英文版)

For many years, surgical treatment of buried penis in children has been researched by several scholars, and numerous methods exist. This study aimed to explore the clinical effect of a modified fixation technique in treating buried penis in children. Clinical data of 94 patients with buried penis who were treated using the modified penile fixation technique from March 2017 to February 2019 in Fujian Maternity and Child Health Hospital (Fuzhou, China) were retrospectively collected, compared, and analyzed. Clinical data of 107 patients with buried penis who were treated using traditional penile fixation technique from February 2014 to February 2017 were chosen for comparison. The results showed that at 6 months and 12 months after surgery, the penile lengths in the modified penile fixation group were longer than those in the traditional penile fixation group (both P < 0.05). The incidence of postoperative skin contracture and penile retraction in the modified penile fixation group was less than that in the traditional penile fixation group (P = 0.034 and P = 0.012, respectively). When the two groups were compared in terms of parents' satisfaction scores, the scores for penile size, penile morphology, and voiding status in the modified penile fixation group were higher than those in the traditional penile fixation group at 2-week, 6-month, and 12-month follow-ups after surgery (all P < 0.05). We concluded that the modified penile fixation technique could effectively reduce the incidence of skin contracture and penile retraction and improve the penile length and satisfaction of patients' parents.

Analysis and prevention of ethical issues related to biomedical research in retracted journal articles / 中华医学科研管理杂志

Objective:To analyze the specific reasons for journal articles being retracted due to biomedical research-related ethical issues after publication and propose corresponding preventive measures.Methods:Journal articles that were retracted between January 1, 2021, and January 1, 2023, were retrieved from PubMed, a literature database in the biomedical field. The retraction statements of those articles that were retracted due to ethical-related issues were analyzed with a summarization of detailed reasons and types.Results:A total of 77 and 128 articles were retracted due to ethical issues in 2021 and 2022 respectively, accounting for 3.9% and 5.4% of all retracted articles in the same period. The major ethical issue was the lack of valid ethical approval. Among articles retracted for ethical issues related to human trials, the proportion of articles retracted due to lack of valid ethical approval increased from 45.9% in 2021 to 57.0% in 2022, which also increased from 50.0% in 2021 to 67.3% in 2022 among retracted articles related to animal experiments. Other ethical issues included problems in the informed consent process, delay in obtaining ethical approval, inconsistency between ethical approvals and the content of the article, and violation of the principles of laboratory animal welfare.Conclusions:The ethical review of medical research involving humans and laboratory animal welfare needs to be strengthened. By promoting the construction of an institutional ethical review system, encouraging researchers to study ethics-related knowledge, standardizing ethical applications and approvals, improving the informed consent process, and attaching importance to the welfare of laboratory animals, the retraction due to ethical issues can be prevented.

A case of recurrent ureteral terminal tumor after radical cystectomy and rectal bladder replacement / 中华泌尿外科杂志

For invasive bladder cancer, radical cystectomy and rectal substitution for sigmoid skin fistulas were commonly used in some medical centers. There is no report on the feasibility of sigmoid colon retraction except nephroureterectomy for patients with recurrent ureteral tumors after operation. We presented a case of recurrent ureteral tumors after rectal substitution bladder surgery for bladder cancer. Finally, left ureteral resection + sigmoid colon return + right ureteral skin stoma was successfully performed.The patient was followed up for 1 year without recurrence.

Effects of a special shaped tip cartilage support structure on alar rim retraction / 中华医学美学美容杂志

Objective:To investigate the clinical effectiveness and significance of special fixing cartilaginous support structure on nasal tip to prevent and correct alar rim retraction.Methods:Special shaped tip extension support structure was composed of two parts of type Ⅲ of septum extension graft (SEG) and two pieces of wedge graft fixed on either side of the cephalic end near the top of support structure. After the alar cartilage vault was fixed to the nasal tip cartilage support structure, the lower lateral cartilage (LLC) cephalic was fixed to both sides of this nasal tip support structure. The LLC received support from the cartilaginous support structure to counter and correct the lower lateral cartilage cephalic retraction. From January 2017 to January 2020, this surgical procedure was used in 34 patients (aged from 20 to 46 years, with mean 32.6 years) with rhinoplasty who had a nasal tip support structure but still had a space between the LLC and the stent intraoperativly. Preoperativly, 4 cases had normal relation of alar columella and alar rim, 18 cases had mild alar rim retraction, and 12 cases had moderate alar rim retraction. The patients were followed up for 6 to 18 months to observe the correction effect and patient satisfaction.Results:Among the 34 patients, 8 patients received alar edge graft, 2 patients received lateral foot support graft, and 2 patients received alar rim graft combined with lateral foot support graft. All patients were followed up for 6-18 months, 30 patients with alar rim retraction were completely corrected, and 4 patients with normal alar and nasal columella relationship did not have alar rim retraction after surgery. No complications such as infection, necrosis, contracture or respiratory dysfunction were found in all patients. 28 cases (82.4%) were very satisfied; 6 cases (17.6%) were satisfied; the satisfactory rate was 100%.Conclusions:The special shaped nasal tip cartilage support structure combined with type Ⅲ SEG and its cephalic wedge grafts could achieve satisfactory clinical results in the prevention and correction of alar rim retraction.

Application of free skin graft or auricle composite tissue in the correction of nasal flange retraction / 中华医学美学美容杂志

Objective:To investigate the clinical effect and application value of free skin or auricle composite tissue transplantation in the correction of nasal alar retraction.Methods:From August 2019 to January 2023, a total of 45 patients with nasal retraction (7 males and 38 females) were treated in Shanghai United Regal Medical Cosmetology Hospital. Age ranged from 18 to 46 years, with a mean of 26.6 years. All patients had retroalar margin retraction caused by insufficient alar lining to varying degrees, with a retraction distance between 2-5 mm, with an average retraction distance of 3.3 mm. 11 cases of nasal flange retraction were corrected by free transplantation of composite tissue of auricle directly. The remaining 34 patients were corrected by alar border cartilage graft and free skin graft.Results:During 2-18 months of follow-up, 41 patients had satisfactory results and no obvious complications. Partial necrosis of free skin was observed in 2 patients, ischemic necrosis of complex flap of auricle was observed in 1 patient, and necrosis of free skin was observed in 1 patient. In addition to the above complications, 3 patients reported that the correction of alar retraction did not achieve the expected effect, but indicated that they were satisfied with the surgical effect, which was considered to be caused by skin contracture and other factors. The overall satisfaction rate of all patients was 91.1%. After follow-up and statistics, 41 patients in this group were satisfied with the results, with an overall satisfaction rate of 91.12%.Conclusions:The application of free skin graft (or auricle composite tissue) to correct nasal alar retraction has the advantages of simple operation, wide indications and accurate efficacy, and is worthy of clinical promotion.

Regulation of platelet function by cantharidin via PI3K/Akt/PKC pathway / 中国药理学通报

To investigate the effect of cantharidin ( CTD) on platelet function and the mechanism of anti-platelet aggregation. Methods Washed platelets were collected from the venous blood of healthy volunteers. The effect of CTD on platelet aggregation and release was determined by aggregometer. The CTD concentration was 2.5 ,5 ,10 μmol • L

Does head tilt influence facial appearance more than head turn?

Purpose: To evaluate the frequency of facial asymmetry parameters in patients with head tilt versus those with head turn. Methods: This cross-sectional comparative study was performed on 155 cases, including 58 patients with congenital pure head turn due to Duane retraction syndrome (DRS), 33 patients with congenital pure head tilt due to upshoot in adduction or DRS, and 64 orthotropic subjects as the control group. The facial appearance was evaluated by computerized analysis of digital photographs of patients' faces. Relative facial size (the ratio of the distance between the external canthus and the corner of the lips of both face sides) and facial angle (the angular difference between a line that connects two external canthi and another line that connects the two corners of the lips) measured as quantitative facial parameters. Qualitative parameters were evaluated by the presence of one-sided face, cheek, and nostril compression; and columella deviation. Results: The facial asymmetry frequency in patients with head tilt, head turn, and orthotropic subjects was observed in 32 (97%), 50 (86.2%), and 22 (34.3%), respectively (P < 0.001). In patients with head tilt and head turn, the mean facial angle was 1.78º ± 1.01º and 1.19º ± 0.84º, respectively (P = 0.004) and the mean relative facial size was 1.027 ± 0.018 and 1.018 ± 0.014, respectively (P = 0.018). The frequencies of one-sided nostril compression, cheek compression, face compression, and columella deviation in patients with pure head tilt were found in 19 (58%), 21 (64%), 19 (58%), and 19 (58%) patients, respectively, and in patients with pure head turn the frequencies were observed in 42 (72%), 37 (63%), 27 (47%), and 43 (74%), respectively. All quantitative and qualitative facial asymmetry parameters and facial asymmetry frequencies were significantly higher in head tilt and head turn patients as compared to the control group (P < 0.001). Conclusion: All facial asymmetry parameters in patients with head tilt and head turn were significantly higher than orthotropic subjects. The quantitative parameters such as relative facial size and facial angle were significantly higher in patients with pure head tilt than pure head turn. The results revealed that pure head tilt was associated with a higher prevalence of facial asymmetry than pure head turn.

Implant-supported canine retraction using different reactivation intervals of elastomeric chains: A CBCT-based split-mouth randomized controlled trial

ABSTRACT Introduction: Orthodontists attempt to maximize treatment efficiency regarding time, tooth position and adverse effects. A new approach, not yet explored, is the activation frequency. Objective: The aim of this split-mouth randomized controlled trial was to evaluate the effect of reactivation intervals on the efficiency of tooth movement. Methods: Thirty eight patients having a Class I malocclusion with bimaxillary dentoalveolar protrusion or severe crowding, Class II with mandibular deficiency or Class III, requiring first premolar extraction and canine retraction were recruited. Elastomeric chains producing 150g were replaced every two, four, six or eight weeks. There were 36, 37, 36, and 36 quadrants randomly allocated to these groups, respectively. The canine retraction rate was the primary outcome. Canine tipping, rotation, and root resorption and pain were the secondary outcomes. Only the outcome assessors were blinded to group assignment. Results: The average total movement for the 6 months was 5.14, 5.31, 2.79 and 3.85 mm for the two-week, four-week, six-week and eight-week reactivation intervals, respectively. Root resorption was significantly higher in the two-week and four-week groups. No adverse events were observed. Conclusion: The canine retraction rate, tipping, rotation and pain were similar in 2, 4, 6 and 8-week activation intervals groups. Longer reactivation intervals show less root resorption. The trial protocol was not pre-registered. The study was self-funded.

RESUMO Introdução: Os ortodontistas buscam otimizar a eficiência do tratamento quanto ao tempo de duração, à posição dos dentes e aos efeitos adversos. Um aspecto ainda não avaliado são os diferentes intervalos entre as ativações. Objetivo: O objetivo desse estudo controlado e randomizado de boca dividida foi avaliar a influência de diferentes intervalos de reativação na eficiência da movimentação dentária. Métodos: Foram recrutados 38 pacientes com má oclusão de Classe I com biprotrusão dentoalveolar ou apinhamento severo, Classe II com deficiência mandibular ou Classe III, que necessitavam de extração do primeiro pré-molar e retração do canino. As cadeias elastoméricas gerando 150 g foram substituídas a cada duas, quatro, seis ou oito semanas, constando 36, 37, 36 e 36 quadrantes alocados aleatoriamente nesses grupos, respectivamente. O desfecho primário foi a taxa de retração do canino. Os desfechos secundários foram a inclinação, a rotação e a reabsorção radicular do canino, e a dor. Somente os avaliadores dos resultados não tinham conhecimento da alocação nos grupos. Resultados: O movimento total médio para os seis meses foi de 5,14; 5,31; 2,79 e 3,85 mm para os intervalos de reativação de duas semanas, quatro semanas, seis semanas e oito semanas, respectivamente. A reabsorção radicular foi significativamente maior nos grupos de duas e quatro semanas. Não foram observados eventos adversos. Conclusão: A taxa de retração, a inclinação e a rotação do canino e a dor foram semelhantes nos grupos com intervalos de ativação de duas, quatro, seis e oito semanas. Intervalos de reativação mais longos mostram menos reabsorção radicular. O protocolo do estudo não foi pré-registrado. O estudo foi autofinanciado.