these 
 materials are made of either latex ( natural rubber ) or synthetic polymer materials 
 ( polyurethane ) .
latex elastics are more commonly used because they present improved 
 properties such as : greater flexibility , lower cost and greater capacity of returning to 
 the original dimensions after undergoing deformation . in orthodontic practice
, the use of elastics has some advantages , such as 
 biocompatibility , low cost , easy installation and removal by the patients .
however , the oral environment may 
 interfere negatively in the properties of these materials .
exposure of these elastics to 
 oral environment results is degradation of their elastic forces .
literature has reported 
 that rubber elastics exposed to oral environment lose between 10 to 40% of their initial 
 force .
after 1211 to 24 
 h of installation , this 
 degradation rate is greatly reduced , resulting in forces with reasonably constant 
 intensity . moreover , in spite of being considered a biocompatible material , santos , et 
 al .
the elongation of the molecular chains of materials should be considered one of the main 
 mechanisms by which the elastic force decay occurs . when the elastic stretches , the 
 polymer chains are uncoiled becoming elongated .
if the force is excessive , such chains 
 will slide one over another resulting in permanent deformation of the material and 
 consequently in the degradation of the force generated by the elastic .
additionally , the oral environment acts as an agent of the elastic force degradation 
 because of physical damages , e.g. : mechanical traumas and temperature 
 alterations .
moreover , the 
 chemical interactions among the material , saliva and dietary substances promote both the 
 absorption of water and other salivary constituents and the solubilization / release of 
 the material 's components in the saliva , consequently modifying the elastics ' molecular 
 structure and favoring their degradation .
most studies on the influence of the oral environment are conducted in 
 vitro , evaluating humidity , saliva composition , ph , temperature and stress 
 induced by elastic cyclic stretch .
however , few studies on the effects of dietary 
 substances are found in the literature .
( 2004 ) evaluated the 
 effect of diet on the mechanical properties of intermaxillary elastics .
these authors 
 observed that dietary substances did not significantly increase the degradation of the 
 mechanical properties of elastics .
( 1998 ) verified that the immersion of elastomeric chains in 
 coca - cola resulted in a greater degradation of forces compared with the 
 immersion in water .
( 2008 ) demonstrated that immersion in coca - cola was 
 not able to alter the pattern of force degradation in two different types of elastomeric 
 chains .
intermaxillary elastics have been routinely employed in orthodontics it is thus 
 important that orthodontists be aware of the mechanical properties of these materials as 
 well as of the influence of oral environment factors on their properties . due to the 
 limited number of studies evaluating the effect of diet on force degradation , the aim of 
 this study was to evaluate in vitro the effects of frequently ingested 
 beverages on the force degradation of intermaxillary elastics .
one hundred and eighty medium force 1/4-inch intermaxillary elastics ( tru - force latex 
 elastic system ; tp orthodontics inc . ,
la porte , in , usa ) were used and divided into six 
 groups ( n=30 ) : group 1 ( control - artificial saliva ) , group 2 ( coca - cola - 
 coca - cola company , so paulo , sp , brazil ) , group 3 ( beer - heineken , so paulo , sp , 
 brazil ) , group 4 ( orange juice - del valle pure squeezed orange juice , coca - cola 
 company , so paulo , sp , brazil ) , group 5 ( red wine - santa lucia cabernet sauvignon , 
 henriquez hermanos ltd . ,
talca , chile ) , group 6 ( coffee - nescaf classic , nestl s.a . , 
 araraquara , sp , brazil ) .
the composition of artificial saliva was 0.0625% kcl , 0.0865% 
 nacl , 0.0056% mgcl2 , 0.0166% cacl2 , 0.0804% 
 na2hpo4 , 0.0326% kh2po4 , 4.274% sorbitol , 
 0.0004% naf , 0.1% c6h5coona , 2% carboxymethylcellulose and 
 distilled water .
elastics with tensile strength ranging from 1.55 to 2 n were selected to standardize the 
 samples and eliminate possible mechanical behavior bias .
therefore , 282 elastics were 
 tested to reach a test sample size of 180 elastics .
initially all elastics were mounted on an epoxy resin board on two steel pins at a 
 distance of 26 mm ( figures 1a and 1b ) and their 
 forces were measured in a tensile testing machine ( dl1000 ; emic ltda . , so jos dos 
 pinhais , pr , brazil ) at a crosshead speed of 150 mm / min .
b ) 
 elastic stretched at 26 mm next , the samples were randomly divided into six groups .
the test of variance 
 homogeneity was applied to verify the baseline forces , showing statistically similar 
 mean values of initial forces ( p>0.05 ) among the groups .
after the baseline readings , the elastics were immersed in a glass flask ( 15x9x14 cm ) 
 containing 300 ml of the tested beverages , according to the experimental groups . 

immersion period was 15 min for the first ( t1 ) and second ( t2 ) cycles and 30 min for 
 third to fifth ( t3 , t4 , t5 ) cycles . at every immersion cycle ,
the beverages were changed 
 ( figure 2 ) and the elastics were washed in 
 distilled water and immersed into 300 ml of artificial saliva for 3 min .
next , the 
 elastics were again washed in distilled water and removed from the resin board to 
 perform a new tensile strength test .
sequence of the experimental groups data were analyzed by one - way repeated measures anova to compare the effects of 
 intervals , beverages and the interaction between them .
figure 3 shows the homogenous distribution of the 
 sample at t0 , where the groups presented statistically similar mean values of initial 
 force ( p>0.05 ) .
since the mean force values of each group were statistically similar , 
 it may be affirmed that the alterations were due to the tested treatments and not to the 
 differences in each group behavior .
homogeneous distribution of samples at t0 figure 4 exhibits the mean force values produced 
 by the intermaxillary elastics regardless of their groups .
notice that in the first 
 moments ( from t0 to t1 ) , there was a greater reduction of the generated forces 
 ( p<0.05 ) , followed by a decrease of degradation rate in the following periods .
mean force values of the intermaxillary elastics regardless of the group this same behavior pattern was seen in the tensile strength forces produced by each 
 group at all observation periods ( figure 5 ) .
figure 5 reveals that the different groups behaved 
 similarly at each study period ( t1 , t2 , t3 , t4 and t5 ) ( p>0.05 ) .
this study evaluated in vitro the effects of frequently ingested 
 beverages on the force degradation of intermaxillary elastics .
the force degradation of 
 intermaxillary elastics , measured by tensile strength test , was observed at all periods , 
 regardless of the group ( figure 4 ) . the greatest 
 degree of force degradation occurred at the initial periods ( from t0 to t1 ) and a 
 gradual reduction of this degradation occurred at the following periods , showing a 
 tendency to reduction over time .
this was confirmed by the statistically significant 
 difference existing between t0 and t1 , t1 and t2 , t2 and t4 , t3 and t5 ( p<0.05 ) .
the mechanical behavior of intermaxillary elastics in the present study was similar to 
 the findings of previous studies in which a greater degradation in the elastic forces at the initial 
 periods of assessment was detected .
( 2011 ) found a different behavior of the degradation of 
 elastic forces : after a first phase of greater force degradation , there was a second 
 stage where the elastics partially recovered the force ( negative degradation ) , followed 
 by a third stage in which slow and gradual force degradation occurred . due to this behavior ,
andreassen and bishara ( 1970 ) suggested the use of a force magnitude four times greater 
 than the intended magnitude for a determined case .
consequently , when the elastics lose 
 40% of their initial force , levels close to those required would still be present for 
 longer periods .
notwithstanding , 
 such procedure should be carefully analyzed because of the risks of damaging the tooth 
 and periodontal tissues by excessively strong forces .
additionally , the findings of an 
 in vivo study 
 suggested that elastics should be changed daily because the oral activity dynamics would 
 increase the fatigue and deformation of material , enhancing the risk of their fracture 
 and failure .
some in vitro studies have been conducted using a dynamic experimental 
 model in which mouth opening and closing movements are simulated , stretching the 
 intermaxillary elastics .
for the present study , a static experimental model was chosen 
 based on the results of previous investigations , which demonstrated that 
 the cyclic elastic stretching only enhances force degradation in the first hour of the 
 experiment ; after this period , the degradation rate returns to its pattern and , by the 
 end of the study , cyclic stretching or not exerts no statistically significant influence 
 on the elastics . liu , et 
 al .
( 1993 ) showed that after 
 200 stretching cycles there was no significant force degradation of intermaxillary 
 elastics .
the results of this research indicate that the contact of dietary beverages with 
 intermaxillary elastics is not able to influence the degradation degree of their forces 
 ( figure 5 ) .
the elastics presented the same 
 behavior when immersed in either artificial saliva or test beverages at all 
 observational periods .
the lack of influence of dietary components on the degradation of 
 intermaxillary forces has also been observed in a laboratory study .
other studies have 
 demonstrated that the ph of the medium in which the intermaxillary elastics are immersed 
 did not influence significantly force decrease of the elastics .
based on this evidence , 
 the beverages used in the present study were not subjected to any ph analysis .
the mechanical behavior of the intermaxillary elastics in the present study can be 
 explained by the " swelling phenomenon " .
the chemically cross - linked points among the 
 molecular chains enable the absorption of liquid into the latex three - dimensional 
 reticulate structure .
the rubber 's free energy decreases with the simultaneous effect of 
 mixing entropy . at the same time
, the molecular chains are elongated followed by the 
 decrease of elasticity of the rubber .
although this study showed solid evidences , the obtained results should be carefully 
 examined because no in vitro study is capable of simulating all factors 
 acting on intermaxillary elastics in the oral environment .
notwithstanding , our findings 
 contribute to improve the knowledge of the mechanical behavior of the intermaxillary 
 elastics employed in orthodontics , enabling greater predictability in the application of 
 mechanotherapy involving latex elastics .
the results also have clinical applications 
 since no restrictions were found to the consumption of the studied beverages in relation 
 to the use of the tested intermaxillary elastics , bringing comfort and freedom for 
 patients choosing their own diet during the orthodontic treatment .
the chemical nature of the evaluated beverages was not able of influencing the degree of 
 degradation of intermaxillary elastics ' forces .
 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 . 