Elastic Ligation Research Articles

The Effect of Elastic and Metallic Ligation Methods on the Unloading Forces for Three Different Types of Nickel-Titanium Archwires Inserted Into Metallic Brackets: An In-vitro Study.

One of the unique properties of the nickel-titanium (NiTi) archwires is the release of light continuous forces with a wide range of activation, which is affected by the method of ligating the wire to the bracket. Both elastomeric modules and metallic ligatures are the most common components to ligate the archwire to the bracket. This study aimed to evaluate the effect of elastomeric versus metallic ligatures on the released forces of three types of rectangular 0.016- by 0.022-inch NiTi wires. This investigation evaluated three different situations of ligating the NiTi archwires to metallic brackets. The produced forces by these wires were evaluated using a modified three-point bending test (a universal testing machine: Testometric 350M®, Instron, Lincoln Close, Rochdale, England). A 0.022-inch slot-size premolar bracket was used for this investigation with zero torque and zero angulation (Master Series®, American Orthodontics, Sheboygan, USA). The first situation involved no ligation to the metallic brackets using three types of NiTi wires, whereas the second situation (the elastic ligation) involved the use of colored elastomeric modules with a 0.045-inch inner diameter and a 0.115-inch outer diameter (Color Ligatures®, American Orthodontics, Sheboygan, USA) to ligate the archwire into the metallic bracket's slot. In the third situation (metallic ligation), stainless steel metallic ligatures with a 0.012-inch (Preformed Ligature Wire®, American Orthodontics, Sheboygan, USA) were used to perform the ligation. The employed NiTi wires were 0.016 x 0.022-inch in diameter (American Orthodontics®, Sheboygan, Wisconsin, USA), and they were of three different types: (1)the superplastic wires (NT3-SE®), the thermally activated wires at 25°C (Thermal Ti-D®), and the thermally activated wires at 35°C (Thermal Ti-Lite®). The thermally activated wires at 35°C (Thermal Ti-Lite®) recorded the lowest force levels for the three ligation methods, while the highest result appeared with the superelastic type (NT3-SE®) and the thermally activated type at 25°C (Thermal Ti-D®) which showed a varied force for different ligation methods. Regarding the three different NiTi wires used, the elastic and metallic ligation increased the force levels for the superelastic type (NT3-SE®) over non-ligation by 50% and 110%, respectively, whereas the elastic ligation raised only the forces for the thermal types (Thermal Ti-D®and Thermal Ti-Lite®) by 75% and 22%, respectively. Both thermally activated types (Thermal Ti-D®and Thermal Ti-Lite®) released forces in the elastic ligation method greater than that of the metallic method by 125% and 20%, respectively. The elastic ligation method raised the unloading forces in comparison with the non-ligation for all tested archwires, whereas the metallic ligation method raised the released forces for the superelastic type (NT3-SE®) and decreased those related to the activated types (Thermal Ti-D®, Thermal Ti-Lite®)due to the increased friction and the instability of the crystalline structure. Only the heat-activated type at 35°C (Thermal Ti-Lite®) reflected the unique properties of the NiTi wires in producing light continuous forces with a wide range of activations regardless of the type of ligation.

A117 MANAGEMENT OF VARICEAL BLEEDING WITH ENDOSCOPIC INJECTION OF N-BUTYL-2-CYANOACRYLATE IN PREGNANCY

BackgroundAlthough variceal bleeding is rare in pregnancy, pregnant woman with non-cirrhotic portal hypertension are at greater risk of variceal hemorrhage due to increased splanchnic blood flow. Variceal hemorrhage is associated with increased risk of maternal and fetal mortality. Most documented cases of variceal bleeding in pregnancy report the use of elastic ligation for hemostatic management. Histoacryl glue has become increasingly utilized in the acute management and secondary prophylaxis of gastric and ectopic varices in the general population.AimsEvidence surrounding the use of Histoacryl glue in pregnancy is limited. We report two cases of variceal bleeding during pregnancy managed successfully with glue.MethodsVarices were confirmed endoscopically. Images were obtained and reviewed. Aliquots of injected glue were recorded. Maternal and fetal outcomes were monitored during pregnancy and post-partum.Results Case 1: A 39-year-old G4P3L0, presented at 20 weeks gestation following several episodes of hematemesis. Urgent esophagogastroduodenoscopy (EGD) revealed hyperemia and portal hypertensive gastropathy in the fundus. A gastric varix with high-risk stigmata was injected with a total of 9mL of 50/50 Histoacryl/Lipodol and bleeding stopped. The patient returned to the hospital two weeks following discharge with melena. Repeat EGD showed mild portal hypertensive gastropathy with a clot at the site of the previous bleeding. No further intervention was required, and the patient delivered at 37 weeks via elective caesarian-section. Case 2: A 41-year-old G2P0L1 presented at 26 weeks gestation with severe anemia refractory to five units of blood transfusion. Urgent EGD showed a large gastric varix with recent stigmata of hemorrhage, but no active bleed. A total of 13 mL of 75/50 Histoacryl/Lipidol was injected into the varix with no further bleeding. She delivered by elective caesarian-section at 37 weeks gestation. Repeat EGD performed following delivery showed a larger varix with fresh clot at the inferior portion of the fundus. Due to concern for re-bleeding, a total of 4 mL of 50/50 Histoacryl/Lipidol was injected at the site. CT scan post-partum showed prominent gastric varices with glue visualized within the peripheral branches of the portal vein (Figure 1).ConclusionsOur cases highlight the successful management of gastric varices using Histoacryl glue in pregnancy. Risks associated with Histoacryl glue include glue embolization, local venous thrombosis, as well as extrusion of glue and ulceration. The general complication rate is quoted between 0.5%-5%. One of the two cases was associated with a maternal complication, with evidence of new portal vein thrombosis following injection. The safety of sclerotherapy in pregnancy with cyanoacrylate remains unclear, and further evaluation of the management of gastric varices in this unique population are required. Funding AgenciesNone

Recurrence of Upper Gastrointestinal Hemorrhage in Sclerotherapy X Elastic Ligature: Systematic Review

Upper gastrointestinal bleeding is an important medical emergency, with a high rate of morbidity and lethality [1]. Over the past few years, a significant evolution in the methods and techniques available has been observed. Endoscopic therapy, whether with elastic ligation or sclerotherapy, is the most indicated for the management of upper gastrointestinal bleeding and for post-bleeding treatment [2].

Recurrence of Upper Gastrointestinal Hemorrhage in Sclerotherapy X Elastic Ligature: Systematic Review

Upper gastrointestinal bleeding is an important medical emergency, with a high rate of morbidity and lethality [1]. Over the past few years, a significant evolution in the methods and techniques available has been observed. Endoscopic therapy, whether with elastic ligation or sclerotherapy, is the most indicated for the management of upper gastrointestinal bleeding and for post-bleeding treatment [2].

Impact of passive self-ligation and conventional elastic ligation on orthodontic force in the simulation of a mandibular lateral incisor linguoversion

This study compared three-dimensional forces delivered to the displaced tooth and its adjacent teeth between passive self-ligation (PSL) and conventional elastic ligation (CL) in simulation of mandibular lateral incisor linguoversions. A multisensor system was used to measure three-dimensional forces delivered to brackets attached to the mandibular left central incisor, lateral incisor, and canine (FDI tooth numbers 31, 32, and 33, respectively). Two ligation methods (PSL and CL), 3 nickel-titanium (0.014-inch) archwires similar to the arch form of normal occlusion, and 2 displacements (1 and 4mm) were tested. In 1-mm displacement, forces were significantly smaller in CL than in PSL at 32 in the labial direction and larger at 31 in the mesial direction for all 3 types of archwires (P<0.01 for both). For 2 of 3 archwires, forces were larger in CL than in PSL at 33 in the lingual direction (P<0.01). In 4-mm displacement, forces were significantly larger in CL than in PSL at 31 in the mesial direction and significantly smaller in CL than in PSL at 33 in the distal direction for all 3 archwires (P<0.05 and P<0.01, respectively). Mean forces in the vertical direction were small, ranging from -0.05 to 0.05N. Under a small amount of displacement, force magnitude in PSL was smaller than that in CL at the displaced tooth in labial-lingual directions. Under a large amount of displacement, a more "open coil spring effect" was significantly obtained in CL than PSL at both adjacent teeth of the displaced tooth.

ENDOSCOPIC BAND LIGATION FOR THE TREATMENT OF HEMORRHOIDAL DISEASE

There are several therapeutic options for symptomatic hemorrhoids, from hygienic and dietary measures to conventional surgery. The best technique adopted for alternative and non-surgical treatment for intermediate grade (II and III) hemorrhoidal disease is rubber band ligation. More recently, the technique has been used with the aid of a gastroscope and a kit of elastic rubber bands for esophageal varices. This technique was called Endoscopic Rubber Band Ligation of hemorrhoids (ERBL). The objective is Compare the results and the incidence of the immediate and late complications in patients undergoing ERBL. The satisfaction with the treatment of patients undergoing different number of rubber band ligatures were also analyzed. This is a cohort study included patients undergoing ERBL from 2007 to 2014 at the hospital. The incidence of early and late complications and the satisfaction with the treatment of patients undergoing until two ligatures and patients undergoing three or more ligatures in the same procedure were compared. The study included 116 patients. The most frequently reported symptom was anal bleeding (n=72; 62.1%). The number of rubber band ligatures performed during the ERBL procedure varied from one to six; 84 (72,4%) patients had three or more rubber band ligatures performed during the procedure. No significant associations were observed between the incidence of early or late complications and satisfaction with ERBL among the group subjected until two rubber band ligatures or three or more rubber band ligatures. The endoscopic elastic ligation method proved to be a feasible, safe and efficient for the treatment of symptomatic hemorrhoidal disease grades II and III. The technique had moderate rates of immediate and late complications, but most of the complications are considered of low magnitude, easily resolved and without clinical repercussions, no matter how much ligations were performed in the same procedure.

The Elastic Ligation of Internal Hemorrhoids: Where Are We Now?

Hemorrhoidal disease requires different means of treatment: medical, surgical and instrumental. Among these, the elastic ligature seems to be an effective and widespread technique in the world. The aim of our study is to report our experience in methodology and short and medium term results of ligation in a population that strongly fears surgery. Patients and Methods: It’s about a retrospective and descriptive study of 208 outpatients treated with elastic ligations for symptomatic internal hemorrhoids. These patients were collected over a period of 15 years (October 2003-April 2018) at the gastroenterology department of Hassan II CHU in Fez. Results: The average age of our patients was 50.3 years [20 - 82 years] with a sex-ratio M/F of 2.85. The clinical signs were dominated by rectorrhagia (99%) complicated by anemia in 116 cases requiring blood transfusion in 72 cases, followed by proctalgia (27.4%). Transit disorders were noted in 65 patients (31.2%). Indications for elastic ligation were symptomatic internal hemorrhoids Grade 3 (65.4%) and Grade 2 (34.6%). The average number of ligation sessions that achieved the therapeutic goal was 2.30 sessions [1 - 4]. The average number of rings per session was 3.1 rings [1 - 6]. Moderate to severe pain was reported by 20 patients (9.6%) mostly within 6 hours of ligation. Minimal rectorrhagia was reported in 33 cases (15.8%). There were no major complications who required a hospitalization. The success rate was 80.7% (n = 168). Surgery was performed in 31 patients (14.9%) and sclerosis in 7 patients (3.3%). Conclusion: The elastic ligation of internal hemorrhoids remains an effective and inexpensive technique when it comes to the treatment of symptomatic internal hemorrhoids of Grade 2 to 3. The results obtained in our study were very reassuring and motivating.

Interest of Sclerosing Injections in Hemorrhoidal Pathology: Experience of the Service of Hepato-Gastroenterology of Fez

Hemorrhoids are a clinical and anatomical subject that has not been completely investigated [1]. This benign condition is expressed by intermittent functional manifestations as rectorrhagies and prolapse. while the medical treatments seek to relieve symptoms, the instrumental ones are intended to reposition and hold the hemorrhoids in an anatomically correct position and to reduce their vascularity [1]. Indeed, sclerotherapy seems an effective and safe method in fact. Aim of the Study: To report the results of a moroccan series of patients treated with sclerosing injections, emphasizing short- and long-term efficacy as well as the rate of complications. Methods: This is a descriptive retrospective study of the 148 patients with symptomatic internal hemorrhoids who have been treated with sclerotherapy in the gastroenterology department of the university medical center of Fez over a period of 17 years [2001-2018]. Results: The average age of our patients is 47.1 years [19 - 86]. We notified a large male predominance with a sex ratio M/F 2.58. Rectorrhagies and prolapse were the most frequent reasons for consultation; they were respectively notified in 96% (n = 143) and 83% of patients (n = 123). Anemia was found in 45 cases (30.4%), of which 29 cases required transfusion. Proctologic examination found internal hemorrhoids grade 2 in 83% (n = 124) and grade 1 in 16.2% (n = 24) of patients. Initial success was found in 119 cases (80.4%) after an average of 2.25 sessions (1 - 4). Nine patients (8, 11%) had minor complications dominated by minimal rectorrhagies in 8 cases, resolved spontaneously. In 29 cases (19.5%), the sessions were interrupted following a failure of the technique in 12 cases (41.3%), in 11 cases after change of the stage of hemorrhoids of stage II to III, in 4 cases following the appearance of an anal fissure contraindicating the procedure, and in 2 cases due to severe pain post sclerosis. Among these 29 cases, 13 patients were referred for surgery, while in 16 patients we opted for an instrumental treatment by ligature. The initial evolution was specified with a average follow-up of 3 months (1 - 13 months). The recurrence rate was 22.3% (N: 33 cases) after an average follow-up of 9.5 months (1 - 48 months). In the long term (over one year) and in the short term, the recidivism rate was 6% (n = 9 cases) and 16.2% (n = 24) respectively. Among recurrent patients, the sclerosis protocol was repeated in 20 patients (60.6%) with a success rate of 85%; for the remaining 13 patients, we opted for elastic ligation in 4 patients, and for surgery in 6 patients, while 3 patients were lost to follow-up. Conclusion: Since the end of the XIX century, sclerosis has been an instrumental technique, simple, inexpensive, and effective for the treatment of symptomatic internal hemorrhoids of grades 1 and 2, allowing good results in the long run, with minimal risk of complications.

Effect of wire size on maxillary arch force/couple systems for a simulated high canine malocclusion.

To better understand the effects of copper nickel titanium (CuNiTi) archwire size on bracket-archwire mechanics through the analysis of force/couple distributions along the maxillary arch. The hypothesis is that wire size is linearly related to the forces and moments produced along the arch. An Orthodontic Simulator was utilized to study a simplified high canine malocclusion. Force/couple distributions produced by passive and elastic ligation using two wire sizes (Damon 0.014 and 0.018 inch) measured with a sample size of 144. The distribution and variation in force/couple loading around the arch is a complicated function of wire size. The use of a thicker wire increases the force/couple magnitudes regardless of ligation method. Owing to the non-linear material behaviour of CuNiTi, this increase is less than would occur based on linear theory as would apply for stainless steel wires. The results demonstrate that an increase in wire size does not result in a proportional increase of applied force/moment. This discrepancy is explained in terms of the non-linear properties of CuNiTi wires. This non-proportional force response in relation to increased wire size warrants careful consideration when selecting wires in a clinical setting.

Effect of ligation method on maxillary arch force/moment systems for a simulated lingual incisor malalignment.

Introduction:The objectives of this study were to determine whether there is a difference in the magnitude of forces and moments produced by elastic ligation when compared to passive ligation, and whether these forces and moments propagate differently along the arch for the two ligation types. A lingual incisor malalignment was used in this study.Methods: The Orthodontic Simulator (OSIM) was used to quantify the three-dimensional forces and moments applied on the teeth given a lingually displaced incisor. A repeated measures MANOVA was performed to statistically analyze the data. Results: The interaction factor illustrated convincing evidence that there is a difference in maximum force and moment values for all outcome variables between ligation types considering all tooth positions along the arch. The mean differences for FX and FY between ligation types were found to be clinically significant, with values for elastic ligation consistently higher than passive ligation.Conclusion: It was found that the maximum forces and moments produced by elastic ligation are greater than those produced by passive ligation and that the magnitude of this difference for the mesiodistal and buccolingual forces is clinically relevant. Additionally, it was determined that elastic ligation causes forces and moments to propagate further along the arch than passive ligation for all outcome variables.

Evaluation of torque moment in a novel elastic bendable orthodontic wire.

The objective of the study was to measure the torque moment delivered by a novel elastic bendable wire, Ti-Nb wire, and to compare it with nickel-titanium (Ni-Ti) and titanium-molybdenum (Ti-Mo) alloy wires. Two sizes of Ti-Nb, Ni-Ti and Ti-Mo alloy wires and 0.022-inch slot stainless steel brackets were ligated with elastic modules or ligature wires. The torque moment delivered by the various wire-bracket combinations was measured using a torque gauge at the temperature and humidity of 37°C and 50%, respectively. As the degree of applied torque and the inserted wire size increased, the torque moment gradually increased. The torque moment of Ti-Nb wires was smaller than those of Ni-Ti wires and Ti-Mo wires, at more than 20 degrees applied torque. The torque moment with wire ligation was significantly larger than those with elastic ligation.

Measurements of the torque moment in various archwire-bracket-ligation combinations

The torque moment generated by third-order bends is important for tooth movement. The purpose of this study was to measure the torque moment that can be delivered by various archwire and bracket combinations at the targeted tooth. Stainless steel (SS) upper brackets with 0.018 and 0.022 inch slots, two sizes of nickel-titanium (Ni-Ti) alloy wires, and three sizes of SS wires for each bracket were used. The wire was ligated with elastics or wire. The torque moment delivered by the various archwire-bracket-ligation combinations was measured using a torque gauge. Statistical analysis was undertaken using analysis of variance (multiple comparison tests and post hoc using Tukey's honestly significant difference test. The torque moment increased as the degree of torque and wire size increased. There was no significant difference in torque moment between the SS and Ni-Ti wires at lower or higher than 40 degrees torque. The torque moment with wire ligation was significantly larger than that with elastic ligation with 0.016 × 0.022 and 0.017 × 0.025 inch Ni-Ti wires in the 0.018 inch slot brackets and the 0.017 × 0.025 and 0.019 × 0.025 inch SS and Ni-Ti wires in the 0.022 inch slot brackets. However, there was no significant difference in torque moment between either ligation method when using the full slot size wires.

Measurement of friction forces between stainless steel wires and “reduced-friction” self-ligating brackets

In this study, we assessed the friction forces between various self-ligating brackets and stainless steel orthodontic wires, subjected to different shear and bending forces in the buccolingual plane. Three kinds of self-ligating brackets and 2 kinds of ligated controls were tested in a newly developed in-vitro system. Friction was tested with stainless steel orthodontic wire in 3 deflection states. The Bonferroni multiple comparisons test was applied to evaluate intergroup differences (P <0.05). Wire samples were examined with a scanning electron microscope before and after sliding. The results showed significant intergroup differences in friction resistance in response to wire deflection. In nonzero buccolingual deflections, passive self-ligating brackets developed higher friction forces, comparable with those in the conventional elastic ligation control group. The control brackets with reduced friction ligature had considerably lower friction forces than any other group. The active self-ligating bracket ranked between the self-ligating brackets and the reduced friction ligature group. A tribologic survey showed substantial surface alterations among wire samples coupled with passive self-ligating brackets. In contrast to manufacturers' claims, this study illustrates that, in certain clinical situations, a firm passive bracket clip can have a negative influence on the wire-bracket frictional characteristics.

In vitro evaluation of the frictional forces between brackets and archwire with three passive self-ligating brackets

The aim of this in vitro study was to evaluate the frictional forces between bracket and archwire that included three passive self-ligating brackets (Damon SL2 SDS). The brackets were individually bonded to a brass mount using a preformed 0.021 x 0.025 inch stainless steel wire jig in order to exclude adverse tipping or torsion. The central bracket was positioned 1 mm higher than the others, in order that the three brackets were vertically unaligned. Thirty-six similar set-ups including in total 108 brackets were investigated using the same wire: copper (nickel-titanium) 0.014 inches. A testing machine was designed and constructed to measure the frictional forces between the wire and the three-bracket set-up. Twelve set-ups were tested to measure kinetic frictional forces between the wire and unaligned passive self-ligating brackets used in the closed position. The frictional properties of two sets of 12 three-bracket set-ups (control) were tested and measured with an open slide and conventional ligation. A stainless steel ligature wire was used in the former, while elastomeric modules were employed in the latter. One-way analysis of variance showed a significant effect of ligation mode on the frictional properties of the three-bracket set-ups (P < 0.001). Post hoc pairwise comparison showed that the frictional forces arising from passive self-ligation were significantly lower (P < 0.01) than those resulting from elastic ligation. The same result was achieved when comparing self-ligation and metallic ligation (P < 0.01). No significant difference was found when comparing elastic and metallic ligation.

Clinical and histological responses to laparoscopically-induced peritonitis in rats

To evaluate the efficacy of inducing peritonitis in rats through laparoscopic cecal ligation (CL), by means of an elastic band. Twelve Wistar rats were subjected to cecal ligated with an elastic band applied using a specially constructed applicator. In six of the animals (the CL group) the cecal sac was preserved intact whilst in the remaining animals (the CLP group) the sac was perforated with scissors. Clinical parameters, characteristics of the peritoneal cavity and cecum, and histological features of the cecal tissue were observed in all experimental animals 8 and 24 h after surgery. CLP animals exhibited at least one clinical sign of sepsis within the first 8 h of observation. The peritoneal liquid was observed to be clear in almost all members of the CLP. Polymorphonucleated cells were detected in the tunica serosa of the cecum of CLP animals. In contrast, all members of the CL group were alive after 24h, and of polymorphonucleated cells in the muscle layer of the cecal wall were observed. The presence of peritoneal liquid was not detected in CL animals. Although elastic ligation of the cecum was reproducible, puncture of the cecal sac was essential for induction of sepsis.

Pseudolipomatose do cólon: relato de caso

A pseudolipomatose cólica é uma condição benigna, raramente descrita, caracterizada histologicamente pela presença de múltiplas vesículas contendo ar na parede do intestino grosso. Acredita-se que a doença tenha origem iatrogênica, ocasionada pela infiltração de ar através da mucosa cólica durante a realização de procedimentos endoscópicos. O objetivo do presente relato é apresentar um caso de pseudolipomatose cólica, confirmada por meio de estudo histopatológico e imunoistoquímico. Relato do caso: Mulher, 74 anos foi submetida à colonoscopia para investigação de anemia. Apresentava sangramento retal cíclico durante as evacuações, perda ponderal e anemia. O exame endoscópico não mostrou alterações do cólon, detectando apenas mamilo hemorroidário que no momento do exame apresentava sinais de sangramento recente. Três semanas após o exame foi submetida à ligadura elástica do mamilo hemorroidário. Durante a realização do procedimento encontrou-se área sobrelevada na mucosa intestinal, de coloração amarelo-esbranquiçada, com aproximadamente quatro centímetros de diâmetro, localizada na parede posterior do reto, a 13 cm da margem anal que inexistia quando da realização da colonoscopia. Foi realizada biópsia da região alterada da mucosa e ligadura elástica do mamilo hemorroidário. O exame histopatológico demonstrou a presença de inúmeros vacúolos de diâmetro variado, algumas vezes confluentes, localizados na lamina própria da parede intestinal mimetizando tecido adiposo. Notava-se ainda presença de pertuito longitudinal que comunicava a região vacuolizada com a superfície da mucosa cólica. As técnicas histoquímicas e imunoistoquímicas para detecção de gordura no interior das vesículas revelaram-se negativas, permitindo o diagnóstico de pseudolipomatose cólica. Após a ligadura elástica a enferma não mais apresentou sangramento retal, recuperando-se da anemia. Conclusão: A pseudolipomatose do cólon, apesar da raridade, é uma condição que pode ser encontrada após a realização de procedimentos endoscópicos no cólon.

In-vitro evaluation of frictional resistance between brackets with passive-ligation designs

The lower frictional resistance produced by passive self-ligating brackets can be helpful during orthodontic sliding mechanics. The aims of this study were to evaluate the frictional resistance of brackets with passive ligation and to compare these values with corresponding controls. Two passive self-ligating brackets (Damon SL II, Sybron Dental Specialties/Ormco, Orange, Calif; SmartClip, 3M Unitek, Monrovia, Calif) and 1 novel bracket with passive elastic ligation (Synergy, Rocky Mountain Orthodontics, Denver, Colo) were used. The brackets were coupled with 3 nickel-titanium archwires (0.014-in round, 0.016 x 0.022-in, 0.019 x 0.025-in) in a simulated ideal arch introducing first-order rotations of 3 degrees and 6 degrees, second-order intrusions of 0.5 and 1.0 mm, and a third-order labial crown inclination of 3 degrees . The dimensions of the brackets were measured with scanning electron micrographs. The results of initial maximum drawing forces (IMDF) were analyzed by 2-way ANOVA and 1-way ANOVA tests. The SmartClip bracket had larger critical angles and distances for binding than the other 2 brackets. When coupled with 0.019 x 0.025-in archwires in an ideal arch alignment, SmartClip brackets had lower IMDF than the other brackets. For the first-order rotations, Synergy brackets had significantly lower IMDF than the other brackets. Damon SL II brackets with smaller critical angles had greater IMDF. For the third-order inclination, the Damon SL II brackets with less torsional play also had greater IMDF. No significant differences of IMDF were found for all the brackets tested in second-order intrusions. However, IMDF increased as the severity of the malocclusion increased. No significant bracket differences were found when binding occurred in second-order distances. In an ideal arch alignment, brackets with greater slot lumen have lower frictional resistance. First-order rotational control was influenced by slot depth, bracket width, and labial cover of the brackets with the same archwire. When a sliding mechanism was used with a third-order inclination change, the brackets with smaller third-order critical contact angles had greater frictional resistance.

Transcutaneous oxygen tensions in assessing the treatment of healed venous ulcers

Transcutaneous oxygen tension (Ptc,O2) was assessed as an indicator of risk of reulceration in 68 limbs with healed venous ulcers. Ptc,O2 was also used to assess two methods of ulcer prophylaxis. Measurements were made over the gaiter skin, the healed ulcer and the upper arm. The results were expressed as a ratio of the lower limb readings over those taken from the arm. Patients were randomized, after the ulcer had healed, to elastic stockings and stanozolol, or elastic stockings and surgical ligation of incompetent superficial veins. Patients who declined to participate in the study were prescribed elastic stockings only. Those limbs remaining healed at 12 months had Ptc,O2 ratios remeasured. The Ptc,O2 ratios from limbs that reulcerated were not significantly lower than those from limbs remaining healed. The Ptc,O2 ratio was significantly increased in limbs treated by stanozolol and elastic stockings (P less than 0.05) and by surgery and elastic stockings (P less than 0.05). There was no significant increase in Ptc,O2 in limbs treated by elastic stockings alone. In those treated by surgery and elastic stockings, there was a significant improvement in limbs with normal deep veins (P less than 0.01), but not in limbs with post-thrombotic changes on ascending phlebography. Although these two methods of ulcer prophylaxis improve the Ptc,O2 ratio, a high ratio has not been shown to be beneficial in preventing ulcer recurrence.

Tetanus intoxication in a filly after treatment for umbilical hernia by applying an elastic rubber ring ligation

Tetanus intoxication in a filly after treatment for umbilical hernia by applying an elastic rubber ring ligation

Friction and orthodontic mechanics: clinical studies of moment and ligation effects

<h2>Abstract</h2> The efficiency of tooth movement associated with orthodontic sliding mechanics can be compromised by friction between arch wire and tube or bracket slot. The described studies measured the apparent coefficient of static friction (μ_a) during sliding along an arch wire. Known moments were applied to simulate tooth tipping. Measurements tested whether intraoral vibration during gum chewing reduced friction. The first experiments measured intraoral friction associated with the sliding of 4 and 8 mm stainless steel (SS) tubes along a SS auxiliary arch wire, in 10 subjects. Mean intraoral μ_a for 4 and 8 mm tubes were 0.12 (SD = 0.04) and 0.17 (SD = 0.05), respectively. Analysis of variance (ANOVA) showed that μ_a was significantly higher (<i>P</i> < 0.001) for the longer tubes. Although intraoral vibration decreased μ_a compared with bench-top tests (<i>P</i> < 0.001), frictional resistance was never completely eliminated. The second experiments studied the effects of ligation. Ten professionals performed exercises to characterize average tight and loose SS ligation forces. These ligation forces (F_{N Ligation}), and those associated with elastic ligation, were reproduced by a calibrated operator in a modified intraoral device, where SS orthodontic brackets slid along a SS auxiliary wire. Ten subjects chewed gum with the device in place. Nested ANOVA and Tukey Honest Significant Difference tests determined the effects of ligation type and environment. No significant differences (<i>P</i> > 0.01) were found between ex vivo and intraoral μ_a values for tight and loose SS ligation. Intraoral values for μ_a were significantly greater than ex vivo values (<i>P</i> < 0.001) for elastic ligation. Overall, the results suggested that vibration introduced by gum chewing did not eliminate friction. Tipping moments and ligation forces were equally significant in determining frictional forces. As well, there was considerable intraoperator variation in F_{N Ligation} for SS ligatures. Variations in clinical ligation forces are likely to be equal or greater than these experimental data and have potential to affect treatment efficiency during orthodontic sliding mechanics.