following completion of fixed orthodontic treatments and debonding of the brackets , the remnants of adhesive should be eliminated in a manner that tooth enamel remains as intact as possible .
change in the superficial layer of enamel , with the most content of minerals and fluoride , is orthodontists concern because following the loss of enamel surface , and exposure of enamel prisms to the mouth environment and organic acids in dental plaque , the susceptibility to decalcification increases .
remnants of adhesive on enamel surface can be eliminated through different methods and instruments including : finishing carbide bur , bioactive glass air abrasion , tungsten carbide bur in low or high speed hand pieces , aluminum oxide air abrasion .
mechanical elimination of adhesives , which are tooth colored materials , is associated with some degree of damages to enamel surface .
studies show that conventional methods of adhesive removal including : ultrasonic and hand scalers , and low speed handpiece with abrasive create visible surface roughness , 10 - 20 m deep gouges , and loss of 100 m thickness of enamel . therefore , any improvement in the technique of adhesive removal is welcomed by orthodontists .
in addition , to conventional techniques , fiber reinforced composite burs and different kinds of laser such as free running erbium - doped yttrium aluminum garnet ( er : yag ) , neodymium - doped yttrium aluminum garnet , xecl and millisecond pulsed co2 are investigated .
composite burs were initially designed to remove cement , stain , and colors from the tooth surface and were recommended for adhesive removal following orthodontic debracketing . according to the manufacturer , the fiber sections with abrasive property is the advantage of this bur .
these sections of zircon / glass fibers are embedded in a matrix of resin and slowly become disintegrated in contact with a hard surface .
they evaluated the surface using atomic force microscopy and concluded that composite bur creates smoother surface compared to tungsten carbide bur .
the studies of almeida et al . and burkes et al . showed that er : yag laser removed greater volume of enamel compared to tungsten carbide bur . on the other hand , the generated heat during adhesive removal
is transferred to the dental pulp and causes histopathological changes that may lead to necrosis through injury to blood vessels .
zach and cohen concluded that raised temperature of the dental pulp tissue by 5.5 ( c ) causes irreversible inflammation in 40% of cases , and by 11 ( c ) leads to the dental pulp necrosis .
studies show that er : yag laser with water cooling , and tungsten carbide bur without water or air cooling did not significantly raise the temperature of the dental pulp tissue .
david et al . reported a cleanup time of 40 s by tungsten carbide bur in high speed hand piece .
the roughness of enamel surface has been assessed by different devices including : linear contact measuring tools , optical three - dimensional scanners , and electron microscopy .
linear contact measuring tools evaluate a limited area of the enamel surface , but optical three - dimensional scanner considers a large area .
electron microscopy is a visual analyzer , which is suitable to evaluate the smoothness of surfaces . considering that no safe method has been suggested to remove residual adhesive , in this in vitro study ,
the effect of three methods of removing adhesive from enamel surface roughness , dental pulp temperature , and also on the time spent was compared .
a sample of 90 intact extracted human premolar teeth were randomly placed in three groups of 30 , although the estimated sample size of each group , through a pilot study on 10 teeth at 95% coefficient of confidence and the power of 80% , was 21 cases .
following cleaning the buccal surface of teeth with fluoride free pumice paste and rubber cup in low speed handpiece , the teeth were rinsed with water and dried by air stream .
then , the surfaces were etched by phosphoric acid gel 37% ( etching agent , resilient ortho technology , florida , usa ) for 30 s , rinsed for 15 s , and dried to appear a matt and chalky surface . a thin layer of adhesive ( resilient ortho technology , florida , usa ) was applied by a micro brush on the etched surface . a standard stainless steel edgewise premolar bracket ( gac , central islip , new york , ny , usa ) was attached to enamel surface with composite ( resilience ortho technology , florida , usa ) , then all four edges were light cured ( top light , taiwan ) for 40 s after removing the excess composite .
the samples were incubated in water for 24 h at 37 ( c ) before debracketing by bracket removal pliers ( ormco , ca , usa ) .
teeth surfaces were explored by microscope at 35 magnification to assess the adhesive residue . according to adhesive remnant index ( ari ) , described by artun and bergland ,
teeth were categorized in 4 grades : 0 = no adhesive , 1 = less than 50% of adhesive , 2 = more than 50% of adhesive and 3 = all the adhesive remains on the tooth surface .
since no difference was found between three groups [ table 1 ] , we tried to remove the remnant of adhesive by either eight bladed tungsten carbide bur ( geber .
brasseler , komet - lemgo , germany ) in low speed handpiece ; er : yag laser at 2.94 m , 20 hz , 125 mj , 2.5 w and at the distance of 5 mm ; and zircon - rich glass fiber reinforced composite bur ( stainbuster abrasive technology inc . , lewis center , oh , usa ) in low speed hand piece . a thermocouple sensor , connected to a microcontroller , was installed on the buccal wall of the pulp chamber through the access hole .
the micro controller was recording time and temperature during the process of removing the adhesive .
enamel surface roughness was evaluated using scanning electron micrographs ( sem ) at 100 magnification .
the texture of the surface was interpreted by enamel damage index , introduced by howell and weekes . in this index : grade 0 is when the surface is smooth without any scratches ; grade 1 is when some scattered scratches are visible ; grade 2 is when the surface is rough with numerous deep scratches and some grooves , and grade 3 is when deep scratches and wide groves are visible with naked eyes .
chi - square test was used to compare the surface roughness and residual adhesive between groups .
t - test and also analysis of variance ( anova ) were used to compare the time spent and thermal changes .
the results were evaluated at the p < 0.05 significance level , with a 95% confidence interval .
the results of enamel surface roughness , assessed under sem at 100 magnification [ figures 13 ] , are shown in table 2 .
the comparison between groups showed that enamel surface roughness was significantly more in er : yag laser group , and composite bur created the smoothest surface .
figures 1 through 3 show the post - treatment image of surfaces , which are : acceptable with fine scattered scratches created by composite bur , with coarse scratches created by tungsten carbide bur , and with wide grooves and numerous coarse scratches created by er : yag laser , which was the roughest , respectively . scanning electron micrograph of a specimen after adhesive removal by composite bur ( 100 magnification ) . scanning electron micrograph of a specimen after adhesive removal by tungsten carbide bur ( 100 magnification ) . scanning electron micrograph of a specimen after adhesive removal by erbium - doped yttrium aluminum garnet laser ( 100 magnification ) .
distribution of enamel damage index * following adhesive removal comparing the thermal changes in each group showed a significant decrease in er : yag laser group , but significant increase in two other groups .
the time required for increasing the temperature of the pulp chamber by 5.5c was 56.53 s in tungsten carbide bur , and 37.86 in composite bur groups [ table 4 ] . in none of the cases of er : yag group , the temperature increased by 5.5c .
four cases of composite bur and four cases of tungsten carbide bur groups did not show an increase in temperature of the pulp chamber by 5.5c .
the time spent ( sec ) that raised temperature of pulp cavity by 5.5 c table 5 shows the time spent in groups .
the results revealed that although no statistical significant difference was found , but er : yag group took the longest time , while the shortest time belonged to tungsten carbide bur group .
regardless of the methods used , some enamel scarring occurs after debracketing and adhesive removal .
however , the advantages of bonding orthodontic attachments unquestionably outweigh the disadvantages . cleaning up of residual bonding resin following debracketing needs to be in a manner that the enamel surface remains intact as much as possible .
hence , the clinician must be aware of the best methods for minimizing enamel damage .
the results of the present study implied that the texture of enamel surfaces , following adhesive removal in the three groups is different .
composite bur created the smoothest , and er : yag laser the roughest surfaces , although at the minimum related power setting .
almeida et al . and burkes et al . showed that er : yag laser removed more enamel compared to tungsten carbide bur . in the present study , and the study of karan et al .
this result might be related to disintegration of composite bur in contact with enamel surface while the cutting edges of tungsten carbide bur remove a significant amount of enamel .
the temperature of the pulp chamber increased significantly in composite bur and tungsten carbide bur groups while decreased significantly in er : yag laser group .
this decrease in temperature was apparently related to the cooling air and water system in er : yag laser application .
stated that in the absence of air or water cooling system , the temperature of the pulp chamber did not significantly increase while ozer et al . suggested low speed hand piece with air cooling , and uysal et al . showed a decrease in temperature by 5.36c when cooling water was applied .
, it took 56.53 s for tungsten carbide bur and 37.85 s for composite bur to increase the temperature by 5.5c .
since increased temperature by 5.5c may lead to irreversible pulp tissue inflammation ( in 40% of cases ) , it is suggested to apply air or water cooling system , or work intermittently when using tungsten carbide or composite burs .
the time consumed to remove adhesive residue from the enamel surface depends largely on the amount of remnant adhesive . in this study ,
the distribution of ari scores for the experimental groups were broadly similar and the ari score two was the most frequent score ; hence , the groups were comparable .
although , no significant differences were observed between groups , tungsten carbide bur took shorter time than two other methods to remove adhesive residue .
this might be related to having sharp cutting edges on this bur while composite bur works by means of abrasion .

 sem images showed that composite bur created the smoothest enamel surface while er : yag laser the roughest.tungsten carbide and composite burs generated significantly more heat compared to er : yag laser.temperature of the pulp chamber increased by 5.5c in 56.36 and 37.86 s by tungsten carbide and composite burs , respectively.tungsten carbide bur was the fastest and er : yag laser the slowest devices to remove adhesive residue . 
 
sem images showed that composite bur created the smoothest enamel surface while er : yag laser the roughest .
tungsten carbide and composite burs generated significantly more heat compared to er : yag laser .
temperature of the pulp chamber increased by 5.5c in 56.36 and 37.86 s by tungsten carbide and composite burs , respectively .
tungsten carbide bur was the fastest and er : yag laser the slowest devices to remove adhesive residue .
regarding the results of the present study , composite bur with air or water cooling system , because of being less harmful to enamel and pulp tissue , is recommended to remove the residual adhesive following orthodontic bracket debonding .
 background : at the end of fixed orthodontic treatment , the remnant of adhesive should be eliminated from the tooth surface . the purpose of this study was to compare the effect of three methods of removing adhesive on enamel surface roughness , dental pulp temperature , and also on the time spent.materials and methods : the brackets on 90 extracted teeth were debonded using bracket removal pliers . 
 a thermocouple sensor was fitted on the buccal wall of the pulp chamber through access cavity to measure thermal changes during adhesive removal . 
 the residue of adhesive was eliminated from enamel surface of teeth by either tungsten carbide bur , erbium - doped yttrium aluminum garnet laser , or fiber reinforced composite bur . 
 scanning electron micrographs images were taken to assess the roughness of enamel surface . the time spent for adhesive removal 
 was recorded as well . 
 chi - square test was used to evaluate the remnants of adhesive and enamel surface roughness ; t - test and also repeated measurement analysis of variance were applied at p < 0.05 to compare the thermal changes of the pulp chamber and time spent between the methods of surface treatment.results:the results of surface roughness were significantly different ( p < 0.001 ) . 
 the pulp temperature changed significantly ( p < 0.001 ) . 
 tungsten carbide bur increased the temperature by 5.5c significantly slower than reinforced composite bur ( p = 0.004 ) , however removed the adhesive residue faster than two other methods although not significantly ( p = 0.069).conclusion : within the limitations of this study , fiber reinforced composite bur created the smoothest enamel surface while er : yag laser the roughest . 
 tungsten carbide and composite burs generated more heat compared to er : yag laser . 
 in addition , tungsten carbide bur was the fastest and er : yag laser the slowest devices to remove adhesive residue . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION