Force-extension characteristics of orthodontic elastics.

The force-extension characteristics for a wide range of elastics were determined. It was found that (1) selection of elastics were determined. It was found that (1) selection of elastics based on 3 x lumen size will probably result in more force being generated than was previously reported, (2) there is very little difference seen in force-extension characteristics when the two manufacturers' elastics are compared, and (3) for experimental purposes, elastic testing can be done in the dry state for force-extension characteristic studies. This investigation has shown that stretching an orthodontic elastic to twice its original lumen diameter produces a force which better represents the manufacturer's expected value. Keeping these principles in mind, a more effective tooth-moving force can be realized, enabling the clinician to properly select orthodontic elastics for intra- and intermaxillary biomechanical procedures.     

In vitro study of force decay of latex and non-latex orthodontic elastics

The aim of this study was to evaluate the force decay of two brands of orthodontic elastics, both offering latex and non-latex products. Samples were subjected to continuous stretching, measuring force at 5 seconds, 8 hours, and 24 hours in both dry and wet conditions. Five hundred samples were used, GAC? and Lancer? 0.25 inch and 4 oz, divided into testing sample sizes of n = 25 per group. For the dry test, elastics were kept stretched to three times their internal diameter for 5 seconds (initial force), 8 hours, and 24 hours; for the wet test, they were stretched for 8 and 24 hours. Both brands showed initial forces significantly greater than those specified by the manufacturers (P < 0.05). Comparing wet/dry conditions, there was a greater force loss in the wet medium than the dry. As for elastic composition (latex or non-latex), the only significant difference found was between Lancer elastics with and without latex in dry conditions, force loss being greater for latex-free elastics. Comparing brands, there was greater force loss with GAC than with Lancer. Comparing elastic force at the eight-hour mark and the twenty-four hour mark to the initial force (only in wet conditions), GAC latex and non-latex and Lancer latex elastics showed significantly less force at eight and twenty four hours than initially. On the other hand, Lancer non-latex was the only type of elastics that did not show a significant decrease in its initial elastic characteristics at eight hours in wet conditions. Nevertheless, Lancer non-latex did show significantly less force in wet conditions at twenty four-hours than the forces observed initially and at eight-hours.     

Evaluation of force degradation characteristics of orthodontic latex elastics in vitro and in vivo

OBJECTIVE: To evaluate the characteristics of force degradation of latex elastics in clinical applications and in vitro studies. MATERIALS AND METHODS: Samples of 3/16-inch latex elastics were investigated, and 12 students between the ages of 12 and 15 years were selected for the intermaxillary and intramaxillary tractions. The elastics in the control groups were set in artificial saliva and dry room conditions and were stretched 20 mm. The repeated-measure two-way analysis of variance and nonlinear regression analysis were used to identify statistical significance. RESULTS: Overall, there were statistically significant differences between the different methods and observation intervals. At 24- and 48-hour time intervals, the force decreased during in vivo testing and in artificial saliva (P < .001), whereas there were no significant differences in dry room conditions (P > .05). In intermaxillary traction the percentage of initial force remaining after 48 hours was 61%. In intramaxillary traction and in artificial saliva the percentage of initial force remaining was 71%, and in room conditions 86% of initial force remained. Force degradation of latex elastics was different according to their environmental conditions. There was significantly more force degradation in intermaxillary traction than in intramaxillary traction. The dry room condition caused the least force loss. CONCLUSIONS: There were some differences among groups in the different times to start wearing elastics in intermaxillary traction but no significant differences in intramaxillary traction.     

An in vitro comparison of 4 brands of nonlatex orthodontic elastics.

The purpose of this study was to compare 4 brands of nonlatex orthodontic elastics with respect to initial force produced and force decay over a 24-hour period. Sample sizes of 12 elastics from American Orthodontics (Sheboygan, Wis), Ortho Organizers (San Marcos, Calif), GAC International (Islandia, NY), and Masel (Bristol, Pa) were used. Equivalent or near-equivalent products were tested: the quarter-in (6.35 mm), 4 or 4.5 oz (113 or 128 g) elastics from each company. An apparatus that repeatedly cycled the elastics to simulate interarch usage with chewing was used to measure force decay over a 24-hour period. Results showed a wide range of initial forces between the brands at an extension of 3 times the marketed internal diameter. The elastics from American Orthodontics, Ortho Organizers, and Masel generated forces statistically below their marketed force levels at 3 times their marketed internal diameter extensions. GAC elastics generated significantly higher forces than marketed at 3 times internal diameter extension. All elastics generated forces below those marketed at 2 times internal diameter. Initial force production was significantly correlated with the measured cross-sectional area of the elastics (P <.01). The force decay patterns of all brands were very similar, but there were significant differences in their abilities to withstand testing. Grouped average percentages of initial force at 4, 8, and 24 hours were 68%, 61%, and 49%, respectively, for the elastics that did not break during testing.     

Orthodontic latex elastics: a force relaxation study

The objectives of this study were to assess the force relaxation of latex elastics occurring within 24 hours of extension and to estimate the extension required to reach the reported force. Five specimens of various manufacturers' latex elastics size and force levels were mounted on a custom-made setup capable of monitoring force levels in real time with a continuous mode and without operator intervention. The percentage of force relaxation was estimated from the initial and 24-hour levels, and the results were analyzed with one-way analysis of variance and the Tukey test at alpha = 0.05 level of significance. The elastics showed force relaxation in the order of 25%, which consisted of an initial high slope component and a latent part of decreased rate. Most relaxation occurred within the first 3-5 hours after extension, regardless of size, manufacturer, or force level of the elastic. The overall as well as the initial relaxation curves were fitted to equations, which described the variation of force with time. Elastic extension to achieve the reported force was found to range between 2.7 and five times the original length. Latex elastics show force relaxation in the order of 25%, which consists of an initial high slope component and a latent part of decreased rate. Most relaxation occurs within the first 3-5 hours after extension, regardless of size, manufacturer, or force level of the elastic. The empirical rule of "3" shows remarkable variation, ranging from 2.7 to five.     

Influence of different beverages on the force degradation of intermaxillary elastics: an in vitro study

Objective:

The aim of this study was to evaluate in vitro the effects of frequently ingested beverages on force degradation of intermaxillary elastics.

Material and Methods:

One hundred and eighty 1/4-inch intermaxillary elastics (TP Orthodontics) were immersed into six different beverages: (1) Coca-Cola^®; (2) Beer; (3) Orange juice; (4) Red wine; (5) Coffee and (6) artificial saliva (control). The period of immersion was 15 min for the first and second cycles and 30 min for the third to fifth cycles. Tensile forces were read in a tensile testing machine before and after the five immersion cycles. One-way repeated measures ANOVA was used to identify significant differences.

Results:

Force degradation was seen in all evaluated groups and at all observation periods (p<0.05). A greater degree of degradation was present at the initial periods, decreasing gradually over time. However, no statistically significant differences were seen among groups at the same periods, showing that different groups behaved similarly.

Conclusion:

The chemical nature of the evaluated beverages was not able to influence the degree of force degradation at all observation periods.     

Latex and non-latex orthodontic elastic force loss due to cyclic temperature

The purpose of this study was to compare the force loss of 1/4 inch (6.35mm) 3.5oz (99g) medium latex elastics from Ormco Corp. to non-latex elastics from ClassOne Orthodontics and Phoenix after being cycled between different temperatures. Elastics were stretched to 1.57 inches (40mm) on jigs and cycled in water baths for 4 minutes at 5 degrees C and 37 degrees C, 21 degrees C and 37 degrees C, 5 degrees C and 50 degrees C, 37 degrees C and 50 degrees C, and a control group was held at 3 degrees 7 degrees C. The force produced by new elastics and elastics after incubation was measured using a Mini 44 Instron. RESULTS: All elastics experienced increased force loss that correlated with increased temperatures with the exception of Ormco latex elastics. The latex elastics had the greatest force loss upon cycling between 5 degrees C and 50 degrees C while the non-latex elastics had the greatest force loss while cycling between 37 degrees C and 50 degrees C. All elastics were strongest when cycled between 5 degrees C and 37 degrees C. CONCLUSION: This study suggests that hot liquids reduce the force of latex and non-latex elastics even when cycled between hot temperatures for brief periods of time.     

Integrated magnetic and elastic force systems.

Magnetic force increases as the distance (d) of the force- generating elements (F approximately 1/d(2)) decreases, whereas elastic force decreases as the distance decreases (F approximately kd). These opposing characteristics suggest that combining both force systems will establish an integrated system with a long-range working ability. The objective of this study was to determine the vertical closure force (F(X)) and the transverse axis moment (M(Y)) of an integrated force system, ie, attracting magnets with elastics (vertical or Classes II and III). F(X) and M(Y) were examined on the orthodontic measurement and simulation system. It was found that the integrated force system had a positive closure force (+F(X)) that never declined to 0 and a long working range. Three regions characterized the force-deflection curve of F(X): the magnetic region (0-3 mm, for magnets with 3/16-in medium elastics), in which the decline in magnetic force was larger than the increase in elastic force (6.3-2.5 N); the constant region (3-7 mm), in which the decline in magnetic force equaled the increase in elastic force (2.5-2.9 N); and the elastic region (7-10 mm), in which there was only an increase in elastic force (2.9-3.5 N). The transverse axis moment (+M(Y)), which tends to close the bite, developed especially in magnets with a single vertical elastic. Clinically, inactivation of vertical elastics by closing the mouth can be overruled by the integrated force system because it exerts adequate force level at both short and long distances.     

高性能固定矫治用磁体与橡皮圈组合力的评价

目的:分析与托槽大小相近的高性能固定矫治用磁体与橡皮圈形成的组合力的稳定性及有效工作距离。方法:将形状及体积与托槽相近的N48型钕铁硼,分别与1/8、3/16、1/4、3/8inch正畸弹力橡皮圈组合成超长距离移动牙齿的组合力,使用万能材料实验机对磁体磁力、橡皮圈弹力和组合力进行测试,并绘制力的变化曲线,分析组合力的特征、磁力与橡皮圈弹力的互补作用、不同拉伸距离的组合力中磁力及弹力的构成比,对组合力与橡皮圈弹力的差异进行t检验。结果:随着拉伸间距的加大,磁体磁力急剧下降,而橡皮圈弹力呈线性增大,组合后力的变化较为平缓,力较为恒定,4种组合力分别达到86、138、163、192g超长工作距离(1.25～20mm)稳恒矫治力。拉伸距离为3mm时,磁力占各组合力的百分比范围是34.94%～93.98%。拉伸距离为6mm时,占组合力的12.60%～37.89%。拉伸距离为12mm时,磁力降到仅占组合力的2.69%～5.98%。统计结果显示,拉伸距离为3mm(P<0.01)、6mm(P<0.01)、9mm(P<0.05)时,4种组合力与单独的橡皮圈弹力的差异有显著性。结论:磁体与橡皮圈形成的组合力是一种新型、理想、超长工作距离的稳恒矫治力。     

The effect of static and dynamic testing on orthodontic latex and non-latex elastics

The purpose of this study was to test the force decay properties of different kinds of orthodontic elastics after subjecting them to static and cyclic testing. Latex and non-latex elastics obtained from GAC, American Orthodontics and Ortho-Organizers were used in a sample size of 10 elastics per group. Static testing involved stretching the elastics three times the internal diameter, while in cyclic testing, the elastics were stretched up to 50 mm to simulate maximum mouth opening. Elastic forces generated were measured using the Instron testing machine and recorded in grams. Elastics on average lose 10% and 12% as a result of static test and 30% and 35% as result of cyclic test for latex and non-latex brands respectively, and most of the force loss occurs during the first half hour and after the first 10 cycles. This difference in force loss between latex and non-latex elastics could be due to the different structure and composition of the polymer involved. There are no significant differences between different groups of latex elastics in terms of force loss or even between the different groups of the non-latex elastics under static testing, however, under cycling testing differences between the groups were detected. Forces generated by the elastics are different from the manufacturers’ labeled forces.     

A comparison of dynamic and static testing of latex and nonlatex orthodontic elastics

The purpose of this study was to determine the effects of repeated stretching (cyclic testing) and static testing on the force decay properties of two different types of orthodontic elastics from a single supplier. Samples of American Orthodontics' 0.25 inch, 4.5 oz (6.35 mm, 127.5 g) latex and nonlatex elastics were used and a sample size of 12 elastics per group was tested. Static testing involved stretching the elastics to three times marketed internal diameter (19.05 mm) and measuring force levels at intervals over 24 hours. Cyclic testing used the same initial extension but cycled the elastics an additional 24.7 mm to simulate extension with maximal opening in the mouth. Both types of elastic had similar initial forces that were statistically below the marketed force (122 and 118 g for latex and nonlatex elastics, respectively) at three times marketed internal diameter. Cyclic testing caused significantly more force loss and this difference occurred primarily within the first 30 minutes. For statically tested elastics the percentage of initial force remaining at 4, 8, and 24 hours was 87%, 85%, 83%, and 83%, 78%, 69% for latex and nonlatex elastics, respectively. For cyclically tested elastics the percentage of initial force remaining at 4, 8, and 24 hours was 77%, 76%, 75%, and 65%, 63%, 53% for latex and nonlatex elastics, respectively.     

CYTOTOXICITY OF INTERMAXILLARY ORTHODONTIC ELASTICS OF DIFFERENT COLORS: AN IN VITRO STUDY

Objectives:

Natural latex does not fall into the category of materials known to be entirely inoffensive. The purpose of this in vitro study was to test the hypothesis that there is no difference in the cytotoxicity between elastics of different colors and those from different manufacturers.

Material and Methods:

Different latex intraoral elastics of different colors (5/16 = 7.9 mm, mean load) were compared. The sample was divided into 7 groups of 24 elastics each: Group T (TP Orthodontics, natural latex elastics, control); Groups U1, U2, U3, U4, U5 and U6 (Uniden, natural latex elastics and colored elastics, namely, green, pink, yellow, red and purple, respectively). Cytotoxicity assays were performed by using cell culture medium containing epithelioid-type cells (Hep-2 line) derived from human laryngeal carcinoma. The cytotoxicity was evaluated by using the "dye-uptake" test, which was employed at two different moments (0 and 24 h). Data were compared by analysis of variance (ANOVA) and Tukey''s test (p<0.05).

Results:

There was statistically significant difference (p<0.05) between Group T and all other groups (U1, U2, U3, U4, U5 and U6) at 0 and 24 h. No statistically significant difference (p<0.05) was found between Groups U1 and U5, U1 and U6, U2 and U3, U2 and U4, U2 and U5, U2 and U6, U3 and U4, U3 and U5, U3 and U6, U4 and U5, U4 and U6, and U5 and U6 at 0 and 24 h.

Conclusions:

The TP Orthodontics elastics promoted less cell lysis compared to the Uniden elastics regardless of their color.     

Experimental evaluation of latex-free orthodontic elastics' behaviour in dynamics

Latex-free products have been introduced in orthodontics following a growth in the number of latex allergy cases reported. The aim of this study is to compare the efficiency between latex-free and latex elastics which are normally used in clinics. In this study, 80 latex-free and 80 latex elastics were divided into 4 groups of 20 elastics. Each group was exposed to a variable number of opening/closing cycles (100, 1200, 2400 or 4800), using a specially adapted machine which simulated the stretching of these elastomeric products during the dynamics of the mouth. The machine extended the elastics' inner diameter from 3 to 5 times its original dimension (the extension being comparable to that experienced during the opening/closing movements of the mouth). Following this, the elastics underwent a dynamic tensile test using the Instron 4301 machine to evaluate possible force loss and deformation. The different test results were analyzed using the Student t-test and ANOVA test of Tuckey. The test results showed differences between the two types of elastics particularly in the inner diameter behaviour: the increase in the inner diameter of the non-latex elastics' was pronounced. The forces applied by both types of elastics were similar until 2400 opening/closing cycles were reached. Thereafter, the nonlatex elastics lost a larger force (p < .01). The test results suggest that latex-free elastics must be replaced more frequently than conventional latex elastics.     

Mechanical and biological comparison of latex and silicone rubber bands.

Latex rubber bands are routinely used to supply orthodontic force. However, because the incidence of allergic reactions to latex is rising, the use of nonlatex alternatives is increasing, and assessing the mechanical properties of the replacement products is becoming more important. The purposes of this study were to compare the mechanical properties of latex and silicone orthodontic rubber bands through static testing under dry and wet conditions, and to compare their biologic (cytotoxic) properties. Three brands of latex and 1 brand of silicone rubber bands were tested. When extended to 300% of the lumen diameter, the silicone group had an initial force equal to 83% of the product specifications; this was the lowest of the 4 groups. All 4 brands showed notable amounts of force degradation at the 300% extension when subjected to saliva immersion; this approximated a 30% force decay over 2 days. The latex bands all followed a similar pattern of force degradation, whereas the silicone bands showed a greater increase in force decay as the extension length increased. The silicone bands were less cytotoxic than 2 of the 3 types of latex. Although the silicone bands showed the least discrepancy of force degradation between air and saliva conditions, the amount of the force decay was the greatest. Therefore, great improvements in the physical properties of the silicone band are required before they can be considered an acceptable replacement for latex.     

An in vitro study simulating effects of daily diet and patient elastic band change compliance on orthodontic latex elastics

This project investigated the effects of food exposure and patient compliance with elastic-band change on the degradation of forces in 3/16-inch, medium-wall, latex elastic bands during a simulated day of clinical wear. Six levels of daily diet/patient compliance were chosen as representative of orthodontic patients and a quasicontrol group. The groups differed with respect to how much exposure to artificial saliva and foodstuffs they experienced. After exposure in mild tension to daily diets and based on compliance with instructions about changing orthodontic elastics, the elastics were tested in tensile mode by stretching to 25 mm, where the load was recorded in newtons. The bands of three manufacturers, Rocky Mountain Orthodontics (RMO), 3M Unitek (UNO), and American Orthodontics (AMO), were examined, with 10 bands per group, per manufacturer, forming a cohort. Two-way analysis of variance and the Tukey-Kramer honestly significant difference tests were used to identify statistical significance (P > .05). With respect to bands from a single manufacturer, no differences were found between daily diet/patient compliance levels. However, differences (P < .0001) were found between manufacturers' bands. RMO > UNO > AMO in all environments. Over a 24-hour period, latex elastics maintain their applied load in the simulated oral environments.     

Effect of the vertical force component of Class II elastics on the anterior intrusive force of maxillary archwire.

Class II elastics are usually employed in the treatment of excessive overbite and overjet with the Begg technique. The effect of Class II elastics on bite opening and the extent of such an effect is uncertain. This article, based on measurements of 30 cases, illustrates that the effect of the vertical component of force from Class II elastics in reducing the intrusive force generated by the anchor bands in the upper archwire is less than previously believed. The position of the circles in the archwire for intermaxillary elastics has the greatest influence on the anterior intrusive force of the upper archwire. The direction of the Class II elastics and the length of the dental arch (a negative correlation) came second, while the force actually exerted by the elastics had the smallest influence. It is, therefore, suggested that the position of the intermaxillary elastic circles should be located according to the differing clinical objectives.     

Does chlorhexidine in different formulations interfere with the force of orthodontic elastics

Objective:To evaluate the effects of different concentrations of chlorhexidine on the decline in force of orthodontic elastics.Materials and Methods:In a laboratory study, five groups of samples were tested, with one control group represented by distilled water (group 1) and four experimental groups: 0.12% manipulated chlorhexidine (group 2), 0.2% manipulated chlorhexidine (group 3), 0.12% chlorhexidine gluconate–based oral solution (0.12% Periogard; group 4), and 0.2% Cleanform mouthwash (formula and action; group 5). The test groups were submersed in artificial saliva at 37°C. Templates were used and submerged in the chlorhexidine solutions for 30 seconds twice a day. Force was measured with a digital dynamometer at six different time intervals: 0, 1, 7, 14, 21, and 28 days.Results:No statistical differences were found among the groups in the initial period, at 24 hours, and at 7 days (P > .05). There were statistical differences between groups 2 and 5 at 14 days of the experiment and between group 1 and the others at 28 days. In the initial period, the force was statistically higher than it was at any of the other periods of the experiment (P < .05).Conclusion:In the present study, chlorhexidine showed no significant influence on the force degradation of the chain elastics tested.     

Orthodontic elastic materials.

Latex elastics and synthetic elastomers have certain similarities and differences. In the fracture tests the latex elastics showed a greater amount of loss in strength than plastic elastomers when stretched over a 21 day period. There is a great variability, as much as 50%, in the tensile strength of the plastic materials taken from the same batch and stretched under the same conditions. The Ormco Power Chain was more resilient than the Unitek AlastiK chain. The Unitek AlastiKs had more force and stretched less. The force decay of synthetic elastomers, stretched over a specific length and time, exhibited a great loss in force. This loss could be as great as 73% during the first day. The decay of force continued at a slower rate during the rest of the 21 day period. Unitek AlastiK C2 double links, when stretched 17 millimeters, had a higher initial force averaging 641 grams (22.5 ounces) than the Ormco Power Chain which averages 342 grams (12.0 ounces). In one day the force was reduced to 171 grams (6.0 ounces) for both materials. The elastic materials within the same batch showed a great variation in the modulus of elasticity under different test conditions. The approximate force generated when stretched dry, within the elastic limit, was 22 grams per millimeter for 3/16 inches heavy latex elastics. The Unitek AlastiK C2 gave a force of 89 grams per millimeter, while the Ormco Power Chain had a value of 46 grams per millimeter. The modulus of elasticity of all of the materials was much lower after immersion in the water bath. The force decay under constant force application to latex, elastic, polymer chains, and tied loops showed that the greatest amount of force decay occurred during the first three hours in the water bath. The forces remained relatively the same throughout the rest of the test period. The elastic materials undergo permanent deformation in shape. The synthetic elastomers exhibited plastic deformation when the elastomers were stretched 17 millimeters for 21 days. In the dry condition the force decay was 63% for the Unitek chains and 42% for the Ormco Power Chain. The synthetic elastomers should be prestretched before being placed in the mouth. The elastomers should be used within their resilient ranges. Clinical treatment procedures should take into consideration the rapid initial force decay of elastic materials that occurs during the first day and the residual forces remaining.     

Influence of temperature and humidity on the long-term storage of latex and non-latex orthodontic elastics

Objectives: The objective of this study was to evaluate the influence of long-term storage on latex and non-latex orthodontic elastics.

Materials and methods: The sample consisted of 300 orthodontic elastics, 150 latex and 150 non-latex (American Orthodontics^® *(AO) and Morelli^®) of medium force and a standard size of 3/16′′ divided into 20 groups, 10 for each manufacturer, with 15 specimens each. The groups (G1*–G10* and G1–G10) were made up based on the manufacturer, storage temperature (ambient and refrigerated), material, and ambient humidity (exposed and non-exposed). The elastics were stretched and their forces measured in five progressive increases of 100% of their inner diameter, starting at a level of 200% stretching, by the MESDAN LAB 3000^® (MESDAN, Italy) testing machine. The tests were carried out at two different times: immediately in as-received state and again after 1 year. Data were analysed using SPSS 16.0 software, the Student’s t-test, one-way analysis of variance (ANOVA) and the Tukey’s post-test.

Results: There was a statistically significant difference between the average forces exerted by the latex elastics compared to the non-latex elastics for all distention levels evaluated, except for 300%; however, the different storage conditions of temperature and humidity did not interfere in the mechanical properties.

Conclusion: Both the latex and non-latex elastics may be stored under any of the conditions tested in the present study, since there were no changes in the potential of the force exerted by the elastics in relation to their percentage stretch over a 1-year period.