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Paper text:
streptococcus salivarius generally has a stronger affinity for the oral soft tissues , but its strains are also found in dental plaque .
several claims have been made regarding the antibacterial effects of restorative materials to prevent recurrent caries .
apart from this , it has been recommended to use an antimicrobial cavity cleanser after tooth preparation and before tooth restoration . because not much information is available regarding the antibacterial effects of dentin bonding systems , two new seventh generation ( one component single - step self - etch ) bonding systems  adper easy one and g bond , one sixth generation ( two component single - step self - etch ) bonding system  xeno iii and one fifth generation ( universal total - etch self - priming ) bonding system  xp bond were compared for their antibacterial effects .
in this study , four dentin bonding systems , adper easy one ( 3 m espe ) , g bond ( gc company , usa , xeno iii ( dentsply , tulsa , oklahoma , usa ) ) and xp bond ( dentsply , tulsa , oklahoma , usa ) , were tested against three bacteria over a period of three months .
the experimental groups were divided according to the test conducted for the antibacterial effects of four bonding systems and control against streptococcus mutans microbial type culture collection ( mtcc ) 497 ( group a ) , streptococcus salivarius mtcc 1938 ( group b ) and l. acidophilus mtcc 447 ( group c ) .
five absorbent filter paper disks of 5 mm diameter were used in each petri plate 
four disks with dentin bonding agents and one blank disk as control . of each dentin bonding agent was dropped with the respective micropipettes on the paper disk and blown dry for 10 s using a chip blower at a distance of 5 mm to remove excess material and solvents .
then , the bonding agent was light - cured at a distance of 2 mm for 20 s using quartz tungsten halogen ( qth ) visible light curing unit ( translux curing light , kulzer ) .
the bacterial strains used in this study were s. mutans , s. salivarius , and l. acidophilus .
the bacterial suspensions were prepared in sterile brain heart infusion broth at 37c for 24 h until a turbidity of 0.5 on the macfarland scale was obtained . for each reading , 100 l of the bacterial suspension was spread evenly on mueller hinton agar plates using sterile cotton swabs . after the surface of the plates dried ,
the disks were placed immediately over the freshly inoculated agar plates using sterile forceps and then incubated at 37c for 48 h for the first reading .
the rest of the paper disks were stored in dark , submersed in distilled water at 37c .
they were placed on freshly inoculated spread plates after specific time intervals  1 day , 1 week , 2 weeks , 1 month and 3 months  after ageing in phosphated buffer saline .
after incubation , the diameter of the zones of inhibition around the disks was measured at two locations using a millimeter scale and the average was calculated .
the data were recorded in terms of the average diameter of inhibition zone ( in mm ) and subjected to the following statistical analysis : anova test and post hoc tukey test .
the dentin bonding system that exhibited the maximum diameter of zone of inhibition was considered as having the most efficient antimicrobial activity .
samples from triplicate trials showed consistent results , which are depicted in graphs 1 , 2 and 3 .
the results revealed that : 
 adper easy one and g bond had minimal effect against the all the test bacteria during the test period(p<0.005)xeno iii had the maximum antibacterial efficacy over a period of 3 months(p<0.005 ) , followed by xp bond .
this antibacterial activity was maximum against s. mutans , followed by l. acidophilus , and least against s. salivarius.xp bond showed inhibition of the test bacteria for up to 2 weeks(p , 0.005 ) .
adper easy one and g bond had minimal effect against the all the test bacteria during the test period(p<0.005 ) xeno iii had the maximum antibacterial efficacy over a period of 3 months(p<0.005 ) , followed by xp bond .
this antibacterial activity was maximum against s. mutans , followed by l. acidophilus , and least against s. salivarius .
xp bond showed inhibition of the test bacteria for up to 2 weeks(p , 0.005 ) .
antibacterial effects of bonding agents against samples inoculated at different time periods in group a antibacterial effects of bonding agents against samples inoculated at different time periods in group b antibacterial effects of bonding agents against samples inoculated at different time periods in group c
operative work in restorative dentistry is now moving away from complete caries removal to an ultraconservative approach , preserving tooth structure and preventing pulpal injury .
however , if there is a decreased removal of the tooth structure , it is possible that some active residual bacteria may be left behind in the minimally excavated lesions .
s. mutans is the most cariogenic , and is responsible for the initiation of enamel caries and development of secondary caries .
l. acidophilus is the main pathogen responsible for the progression of dental caries , especially deep . in vitro studies
have shown that the tooth - restoration interface created when using the dentin bonding agents does not eliminate microleakage and bacterial penetration .
this may lead to invasion of cariogenic bacteria and their toxins into the dentin . then
, their proliferation occurs and the bacteria may permeate the dentinal tubules , which leads to secondary caries .
thus , dentin bonding is an adjunct in preventing secondary caries as it may stop or slow the bacteria that invade the tooth - restoration interface via microleakage .
these materials provide adjunct treatment , contributing to suppression of residual infection , and increase the longevity of the restored tooth .
this biological , hermetic seal can be obtained by application of the dentin bonding systems directly to the dentin surface to obtain a resistant structure against bacterial invasion .
the decrease in bacterial counts in the oral cavity is associated with decreased caries incidence .
but , once a carious lesion is established , caries removal and an adequate tooth preparation are required as part of the restorative treatment .
three of these were self - etching systems that simplified the application procedure and reduced the technique sensitivity and risk of the primed surface being contaminated . for the etch and rinse bonding systems , like xp bond
the antibacterial effect might also be due to the release of residual monomers present in the oxygen - inhibited layer .
the current dentin bonding systems available are one- , two- or three - step systems , depending on how the three cardinal steps of etching , priming , and bonding to the tooth structure are accomplished or simplified . the recently introduced , seventh generation all - in - one adhesives
the self - etching dentin bonding systems used in this study demonstrated antibacterial action to varying degrees .
g bond does not show much antibacterial activity , and it did not differ significantly from the control group .
adper easy one , having a ph of 3.5 , also does not show much antibacterial activity .
this result is in agreement with a study that found that the benefit of the low ph environment exhibited by dentin bonding systems should be considered as being limited .
the difference noted in the antibacterial activity of adhesives against the bacteria could be related to either their acidity or their chemical composition .
it may also be related to the viscosity , diffusion capacity and presence of antibacterial agents in the bonding systems .
previous studies concerning the antibacterial effect of commercially marketed dentin bonding systems have generally attributed this effect to their low ph environments .
harper and loesche in 1984 reported that the ph values of denting bonding systems , which cause 100% killing over a 3-h - period , is 3.0 for s. mutans .
thus , adper easy one , having a ph of 3.5 , does not show appreciable antibacterial activity against it , while xeno iii , whose self - etch primer has a ph of 1.4 , showed considerable antibacterial property against it . a recent review on self - etching dentin bonding systems
has attributed their antibacterial properties to their low ph or to specific antimicrobial components such as glutaraldehyde and 12-methacryloyloxydodecylpyridinium bromide .
the inhibitory property of xeno iii has also been attributed to the liquid b of this adhesive system , which contains fluoride among other components .
the high viscosity of this adhesive due to the presence of urethanedimethacrylate in its formulation , which is a hydrophobic resin monomer with high molecular weight , may modulate its antibacterial activity due to its slow diffusion . considering the observed variations of inhibition zones between the dentin bonding systems used , it may be speculated that their antibacterial effects depends on components that are originally incorporated to promote adhesion .
bacterial binding to the tooth / restoration interface or leakage through a marginal gap might not occur for a specific period of time when using these materials .
thus , the size of inhibition zones was measured for up to 3 months ( ) against the caries - causing bacteria .
equally important is the effect that the tested materials have on residual bacteria left in the tooth preparation prior to the restorative procedure per se . in a clinical setting ,
the materials are freshly applied to the cavity preparation that might contain some residual bacteria and then light cured before the final restoration is placed .
lastly , a few points have to be kept in mind as limitations of this study .
first , as it was an in vitro study , the interactions that the adhesive components have with dentin will be different than from the experimental setting , which might affect their possible antimicrobial effect .
second , the diffusion co - efficient in agar gel and the ability of the material to wet the agar surface might not correspond to what occurs clinically . finally , different amounts of the adhesive systems remained in the paper discs after removing excess material by air blowing .
all the materials had similar - sized droppers for dispensing material but , due to the more viscous nature of adper easy one , more material was present on its discs as compared with the other three adhesive systems .
these differences might have also affected the end results to some extent and should be considered when comparisons are made among these materials .

 the antimicrobial efficacy of xeno iii was statistically superior , followed by xp bond , while g bond and adper easy one showed the least antibacterial activity over a period of 3 monthsthe maximum antibacterial activity was seen against s. mutans , followed by l. acidophilus , and least against s. salivariusthere was a statistically significant difference between the antibacterial properties of all the four dentin bonding agents against the test bacteriathe antibacterial effect decreased over a period of 3 months for all the dentin bonding systems .
this decrease was significant after 2 weeksthe data presented here relate to in vitro conditions .
the in vivo conditions , such as the presence of smear layer containing dentin , the amount and concentration of components released from dentin bonding systems , might modify the antimicrobial efficacy of the dentin bonding systems . 
 
the antimicrobial efficacy of xeno iii was statistically superior , followed by xp bond , while g bond and adper easy one showed the least antibacterial activity over a period of 3 months the maximum antibacterial activity was seen against s. mutans , followed by l. acidophilus , and least against s. salivarius there was a statistically significant difference between the antibacterial properties of all the four dentin bonding agents against the test bacteria the antibacterial effect decreased over a period of 3 months for all the dentin bonding systems .
this decrease was significant after 2 weeks the data presented here relate to in vitro conditions .
the in vivo conditions , such as the presence of smear layer containing dentin , the amount and concentration of components released from dentin bonding systems , might modify the antimicrobial efficacy of the dentin bonding systems .
aim : the aim of this in vitro study was to evaluate and the compare antibacterial efficacy of four dentin bonding system against streptococcus mutans , streptococcus salivarius and lactobacillus acidophilus over a period of three months using agar disk diffusion test.methodology:all the three standard bacterial strains were inoculated into bhi broth and incubated at 37c for 48 hours . 
 a 100 l of broth suspension containing aliquots of s. mutans , s. salivarius and l. acidophilus were spread onto m - h agar medium using sterile cotton swabs . 
 the experimental groups were as follows : group a : test conducted for evaluation of antimicrobial efficacy against s. mutans mtcc 497 , group b : test conducted for evaluation of antimicrobial efficacy against s. salivarius mtcc 1938 , and group c : test conducted for evaluation of antimicrobial efficacy against l. acidophilus mtcc 447 . for sample preparation , 20 l bonding agent was dropped with micropipettes on paper disks , and blown dry for 10 seconds . 
 then it was light - cured at 2 mm for 20 sec using a qth visible light curing unit . for first reading , 
 the sample disks were placed over the freshly inoculated agar plates and then incubated at 37c for 48 hours . 
 the rest of the paper disks were stored in dark , submerged in distilled water at 37c . 
 they were placed on freshly inoculated spread plates after specific time intervals- 1 day , 1 week , 2 weeks , 1 month and 3 months after ageing in pbs . 
 after incubation , the diameters of zones of inhibition around the plates were measured . 
 the experiment was performed twice in triplicate . 
 the data was then statistically analysed using two way anova test and post hoc.results:results showed that xeno iii had the maximum antibacterial efficacy over a period of three months , followed by xp bond . 
 this antibacterial activity was maximum against streptococcus mutans , followed by lactobacillus acidophilus and least against streptococcus salivarius . 
 adper easy one and g bond had minimal effect against the test bacteria during the test period.conclusion:the antibacterial effect decreased over a period of three months for all the dentin bonding systems .