placement of fixed orthodontic appliances usually colonizes streptococcus mutans , and enhances the risk of dental caries.[13 ] fluoride - releasing bonding materials for bonding the brackets showed almost no demineralization inhibiting effect .
buyukilmaz and ogaard in an earlier study suggested the combined use of antimicrobials and fluoride to enhance the cariostatic effect of fluoride .
a new fluoride releasing and antimicrobial bonding material clearfil protect bond self - etch primer ( cpb ) ( kurrary medical inc .
this two - step self - etch primer ( sep ) consists of a specially treated sodium fluoride to resist against demineralization .
additionally , it contains 12-methacryloyloxydodecyl pyridinium bromide ( mdpb ) ; the antibacterial agent of this sep .
recently , another self - etching primer has been developed for orthodontic practice ( transbond plus self - etching primer , 3 m unitek , monrovia , ca , usa ) .
this one - step sep combines the etching , priming , and bonding in one - step application and reduces the bonding time , increases the cost - effectiveness for the clinician and the patient , and not requiring a separate acid etching step and the need for rinsing . however , effective bonding of these two self - etching primers is controversial .
and cal - neto and miguel reported that the sbs of brackets bonded with cpb , in comparison with conventional method ( cm ) ( acid etching and priming ) did not show any significant difference , while bishara et al . and tuncer et al
. found that cpb had significantly higher sbs than cm . on the other hand , ulker et al . , and holzmeier et al . , stated that the sbs of brackets bonded with cpb was significantly lower than cm .
dorminey et al . , reported no significant difference in the bond strength between the brackets bonded with tp and cm , whereas aljubouri et al .
, and grubisa et al . , observed significantly lower sbs in brackets bonded with tp and conversely , buyukilmaz et al . , and
bishara et al . , reported significantly higher sbs values in brackets bonded with tp , in comparison with cm .
based on the controversial results of the previous studies , the purpose of this study was to evaluate and compare the sbs and adhesive remnant index ( ari ) of brackets bonded with conventional acid etching and priming , transbond plus , and clearfil protect bond self - etch primers .
in this prospective in vitro study accomplished in torabinejad dental research center of isfahan dental school , we examined 48 human maxillary premolars , extracted for orthodontic purposes .
the selection criteria included intact buccal enamel , the absence of pretreatment with chemical agents and the absence of cracks and dental caries .
after storage of the sample in thymol ( 0.1% wt / vol ) for a week , they were rinsed with distilled water and then the roots of them were embedded into a self - cure acrylic resin ( rapid repair , detrey dentsply ltd .
the long axis of each tooth was aligned parallel to the cylindrical base with a jig .
the teeth were cleaned and polished with a fluoride - free pumice ( prophylaxis paste , golchai co. , tehran , iran ) using a low - speed handpiece for 10 seconds , and then , they were washed and air dried with an oil free air spray thoroughly .
the samples were randomly divided into three groups of 16 teeth each . for bonding the samples with transbond xt adhesive resin ( 3 m unitek , monrovia , ca , usa ) [ figure 1 ] , 0.018  stainless steel brackets ( standard edge , orthoorganizer , ca , usa ) were used .
the bonding procedure was performed for each self - etch primer as follows : transbond xt adhesive resin the teeth were etched with 37% phosphoric acid ( american orthodontics co. , wi , usa ) for 30 seconds .
then , they were washed completely and dried for 10 seconds to chalky white appearance . after application of a thin layer of the transbond xt primer (
3 m unitek , monrovia , ca , usa ) [ figure 2 ] on the etched enamel surface , the brackets were bonded with transbond xt adhesive resin and light cured with dr 's light ( prestige dental products inc .
first , the self - etching primer was applied using slight agitation for 20 seconds and dried with a mild air flow .
after that , the adhesive system was cured for 10 seconds and the brackets were bonded with transbond xt adhesive resin similar to group 1 .
clearfil protect bond ( self etching primer and bond ) according to the manufacturer 's instruction , tp [ figure 4 ] was applied to the teeth for 5 seconds and the brackets were bonded with transbond xt adhesive resin and light cured for 40 seconds .
transbond plus ( one step self etching primer ) all the samples were stored in 37c distilled water for 24 hours and were thermocycled from 5c to 55c for 500 cycles .
sbs of the sample was evaluated by a universal testing machine ( zwick 2020 , zwick gmbh and co. , ulm , germany ) .
the blade of machine was placed vertically between the base of bracket and the resin [ figures 5 and 6 ] and started to apply force in and occluso - gingival direction with a crosshead speed of 1 mm / min . placing the blade of zwick machine vertically between the base of the bracket and the resin ( lateral view ) placing the blade of zwick machine vertically between the base of the bracket and the resin ( frontal view ) to determine the shear bond strength in mpa , the measured sbs in newton was divided by the bracket surface area 11.55 mm .
the mode of failure was assessed with optical stereomicroscope ( 10 magnification , olympus szx9 , olympus corporation , shinjuku- ku , japan ) .
failures were scored , according to adhesive remnant index ( ari ) developed by artun and bergland .
the following scale is used to quantify the amount of remaining adhesive on the teeth surfaces :  o  : no adhesive remains on the tooth ;  1  : less than 50% of adhesive remains on the tooth ;  2  : more than 50% of adhesive remains on the tooth ;  3  : all adhesive remains on tooth and the imprint of bracket base is visible on it .
all statistical analyses were preformed with the statistical package for special science ( spss 11.0 , spss inc . ,
descriptive statistics , including the mean , standard deviation , minimum , and maximum , were calculated for each of the three groups . after analysis the normal distribution of sbss of the samples with kolmogorov - smirnov test and test of homogeneity of variances , comparisons of the means of sbs in the three groups were carried out with one - way analysis of variance ( anova ) .
the kruskal - wallis test was used to determine significant differences in the ari values of the groups .
for bonding the samples with transbond xt adhesive resin ( 3 m unitek , monrovia , ca , usa ) [ figure 1 ] , 0.018  stainless steel brackets ( standard edge , orthoorganizer , ca , usa ) were used .
the bonding procedure was performed for each self - etch primer as follows : transbond xt adhesive resin the teeth were etched with 37% phosphoric acid ( american orthodontics co. , wi , usa ) for 30 seconds .
then , they were washed completely and dried for 10 seconds to chalky white appearance . after application of a thin layer of the transbond xt primer (
3 m unitek , monrovia , ca , usa ) [ figure 2 ] on the etched enamel surface , the brackets were bonded with transbond xt adhesive resin and light cured with dr 's light ( prestige dental products inc .
first , the self - etching primer was applied using slight agitation for 20 seconds and dried with a mild air flow .
, the adhesive system was cured for 10 seconds and the brackets were bonded with transbond xt adhesive resin similar to group 1 .
clearfil protect bond ( self etching primer and bond ) according to the manufacturer 's instruction , tp [ figure 4 ] was applied to the teeth for 5 seconds and the brackets were bonded with transbond xt adhesive resin and light cured for 40 seconds .
transbond plus ( one step self etching primer ) all the samples were stored in 37c distilled water for 24 hours and were thermocycled from 5c to 55c for 500 cycles .
the teeth were etched with 37% phosphoric acid ( american orthodontics co. , wi , usa ) for 30 seconds .
then , they were washed completely and dried for 10 seconds to chalky white appearance . after application of a thin layer of the transbond xt primer (
3 m unitek , monrovia , ca , usa ) [ figure 2 ] on the etched enamel surface , the brackets were bonded with transbond xt adhesive resin and light cured with dr 's light ( prestige dental products inc .
first , the self - etching primer was applied using slight agitation for 20 seconds and dried with a mild air flow .
then , clearfil protect bond was applied and gently air flowed . after that , the adhesive system was cured for 10 seconds and the brackets were bonded with transbond xt adhesive resin similar to group 1 .
according to the manufacturer 's instruction , tp [ figure 4 ] was applied to the teeth for 5 seconds and the brackets were bonded with transbond xt adhesive resin and light cured for 40 seconds .
transbond plus ( one step self etching primer ) all the samples were stored in 37c distilled water for 24 hours and were thermocycled from 5c to 55c for 500 cycles .
sbs of the sample was evaluated by a universal testing machine ( zwick 2020 , zwick gmbh and co. , ulm , germany ) .
the blade of machine was placed vertically between the base of bracket and the resin [ figures 5 and 6 ] and started to apply force in and occluso - gingival direction with a crosshead speed of 1 mm / min . placing the blade of zwick machine vertically between the base of the bracket and the resin ( lateral view ) placing the blade of zwick machine vertically between the base of the bracket and the resin ( frontal view ) to determine the shear bond strength in mpa , the measured sbs in newton was divided by the bracket surface area 11.55 mm .
the mode of failure was assessed with optical stereomicroscope ( 10 magnification , olympus szx9 , olympus corporation , shinjuku- ku , japan ) .
failures were scored , according to adhesive remnant index ( ari ) developed by artun and bergland .
the following scale is used to quantify the amount of remaining adhesive on the teeth surfaces :  o  : no adhesive remains on the tooth ;  1  : less than 50% of adhesive remains on the tooth ;  2  : more than 50% of adhesive remains on the tooth ;  3  : all adhesive remains on tooth and the imprint of bracket base is visible on it .
all statistical analyses were preformed with the statistical package for special science ( spss 11.0 , spss inc . , chicago , illinois , usa ) .
descriptive statistics , including the mean , standard deviation , minimum , and maximum , were calculated for each of the three groups . after analysis the normal distribution of sbss of the samples with kolmogorov - smirnov test and test of homogeneity of variances , comparisons of the means of sbs in the three groups were carried out with one - way analysis of variance ( anova ) .
the kruskal - wallis test was used to determine significant differences in the ari values of the groups .
the results of the anova showed statistically significant difference in sbs among the three groups ( p<0.001 ) .
the tukey 's hsd test indicated that the sbs of group cm ( mean : 15.084.00 mpa ) and group cpb ( mean : 13.653.01 mpa ) were significantly higher than group tp ( mean : 9.772.57 mpa ) ( p<0.001 ) , but there was no significant difference in sbs of group cm and group cpb ( p=0.435 ) .
descriptive statistics of shear bond strength in study groups the distribution of the ari scores is shown in table 2 .
wallis test showed no significant difference in the ari scores of the groups ( p=0.287 ) .
the potential risk of new enamel caries among patients with fixed appliances is estimated between 13 and 75% .
patients oral hygiene status and diet during treatment are the significant factors for developing dental caries .
mdpb in clearfil protect bond has revealed great antibacterial effect because it has the potential to destruct the cell membrane of bacteria .
the specially treated sodium fluoride ( naf ) in cpb makes the enamel resistant to the acid generated by bacteria . in the current study
the mean sbs of group cpb in comparison with the mean sbs of group cm did not show any significant difference , according to post hoc tukey 's test ( p=0.435 ) .
the obtained result was consistent with the results of studies conducted by korbmacher et al . and cal - neto and miguel . in spite of the results of the present study ,
the higher sbs of brackets bonded with cpb , has been reported by bishara et al . , and tuncer et al . , conversely , ulker et al . , and holzmeier et al . , showed lower sbs of brackets bonded with cpb than conventional acid etching and priming
however , according to our study cpb has fulfilled the requirement to bond orthodontic brackets , because it shows the sbs higher than the minimum recommended by reynold et al . , and is not such greatly high that could damage the periodontium during debonding .
self - etching systems have become an accepted bonding technique , since they combine the etching and priming steps and do not need a rinsing and drying step after etching ; so , diminishes chair time and are cost - effective for the clinician . according to the results of this study , one - step tp self - etching primer revealed lower sbs than cm and cpb ( p<0.001 ) .
stated that the sbs of bonded brackets should be more than 68 mpa for adequate adhesion in orthodontics .
thus , tp has the mean sbs , high enough to resist against accidental debonding during treatment .
notwithstanding , higher mean sbs of brackets bonded with tp has been observed by buyukilmaz et al . , and bishara et al . , while arnold et al . , and dorminey et al .
, reported that there was no significant difference in the mean sbs of brackets bonded with tp and cm .
the contradictory results of the studies , conducted to evaluate and compare the mean sbs between brackets bonded with cm , cpb , and tp , could be related to difference in the conditions of the sample storage , operators techniques , duration of light curing , doing or not doing thermocycling , and the evaluation of the sbs with different methods.[2932 ] according to the results presented , in table 2 , the ari scores of 1 and 2 are the most prevalent for all three groups and the kruskal 
the site of failure could be within the bracket - adhesive - enamel complex and the ari scores of 1 and 2 in this study indicate that in the most of the samples , the bond failure has occurred within adhesive and some adhesive remained on the enamel .
this mode of failure in group cpb similar to the findings of other studies and dominant score of  1  and  2  for group tp is supported by the reports of the previous studies .
the first opinion supports the bracket adhesive interface failure and believes that this mode of failure is safe for enamel and diminishes the risk for enamel crack and damage .
our findings support this opinion . another opinion involves failure at the enamel  adhesive  resin interface and states that this mode of failure takes less time to remove the adhesive and polish the surface of enamel .
this pattern of failure is supported by some authors , but we believe that failure close to enamel is not safe , and , the findings of the present study support our belief .

 cpb has enough sbs to use for bonding of orthodontic brackets and the pattern of debonding is safe for enamel.despite that brackets bonded with tp has a lower mean sbs than those bonded with cm , but the sbs of brackets bonded with tp is high enough for clinical practice .
in addition , the mode of failure with tp is safe for enamel . 
  cpb has enough sbs to use for bonding of orthodontic brackets and the pattern of debonding is safe for enamel . despite that brackets bonded with tp has a lower mean sbs than those bonded with cm , but the sbs of brackets bonded with tp is high enough for clinical practice .
 background : the aim of this study was to evaluate the shear bond strength of an antimicrobial and fluoride - releasing self - etch primer ( clearfil protect bond ) and compare it with transbond plus self - etch primer and conventional acid etching and priming system.materials and methods : forty - eight extracted human premolars were divided randomly to three groups . in group 1 , 
 the teeth were bonded with conventional acid etching and priming method . in group 2 , 
 the teeth were bonded with clearfil protect bond self - etch primer , and transbond plus self - etch primer was used to bond the teeth in group 3 . 
 the samples were stored in 37c distilled water and thermocycled . 
 then , the sbs of the sample was evaluated with zwick testing machine . 
 descriptive statistics and the analysis of variances ( anova ) and tukey 's test and kruskal - wallis were used to analyze the data.results:the results of the anova showed that the mean of group 3 was significantly lower than that of other groups . 
 most of the sample showed a pattern of failure within the adhesive resin.conclusion:the shear bond strength of clearfil protect bond and transbond plus self - etch primer was enough for bonding the orthodontic brackets . 
 the mode of failure of bonded brackets with these two self - etch primers is safe for enamel . 
INTRODUCTION
MATERIALS AND METHODS
Bonding procedures
Group 1 (conventional acid etching and priming with Transbond XT primer) (group CM)
Group 2 (Clearfil protect bond) (group CPB)
Group 3 (Transbond Plus self-etching primer) (group TP)
Evaluation of shear bond strength
Residual adhesive
Statistical analysis
RESULTS
DISCUSSION
CONCLUSIONS