this advantage is enhanced through sealant strength in penetrating to the depth of the fissures and retention in the porosity of the etched enamel surfaces .
the better the resin and the etched enamel contact , the more increased will be the adhesion of s sealant to the enamel .
therefore , the cleaner the teeth surface and the better etching , rinsing and drying , the better resin can wet the etched enamel and penetrate into deeper depth .
the remains of the etching products will cause in lesser resin penetration in the etched enamel and causes lesser retention ; therefore , the total eradication of dissolved calcium phosphate salts will result into improvement of sealant bond to the tooth .
the purpose of the present study is to assess the effect of different rinsing angles of the etched enamel to the bond strength between the tooth and the sealant .
in the present study , 60 first - maxillary premolars , which had been extracted for orthodontic purposes were collected .
all teeth were free of any caries , breakage or enamel problems at buccal or lingual surfaces . following rinsing with water , the teeth
depending on the rinsing angle , the teeth were divided into six groups as follows : group i ( with a rinsing angle of 90 ) ; group ii ( with a rinsing angle of 75 ) ; group iii ( with a rinsing angle of 60 ) ; group iv ( with a rinsing angle of 45 ) ; group v ( with a rinsing angle of 30 ) ; and group vi ( with a rinsing angle of 15 ) . following this division ,
the teeth in each of the groups were sub - divided into two groups as follows : buccal ( five teeth ) and palatal ( five teeth ) randomly .
next , the teeth roots were mounted in plaster blocks ( vel - mix stone , kerr , italy ) with a diameter of 2.5 cm and a height of 2 cm .
they were mounted in such a way that the height of contour of the surfaces were almost in vertical positions .
tow fissures , one vertically and one horizontally were cut by a high speed hand piece to indicate the location , which was etched and rinsed . by means of a low speed hand piece , the examination sites on the teeth were cleaned or 10 sec . in this step ,
the teeth were microscopically tested for a second time to find any enamel problems . in order to clarify the rinsing angle exactly , a syringe on a moving protractor in a distance of 2 cm of the tooth surface
a barometer , on the water pouring system , helped to uniform the water pressure , pouring on all samples .
after 20 sec of etching ( by scotch bond , 3 m , st paul , mn , usa ) , the teeth surfaces were rinsed for 20 sec at each of the angles mentioned above .
the teeth were dried in such a way that the chalky - white enamel surface was visible . to put the sealants ( concise , 3 m , espe , usa ) on the etched surfaces , transparent plastic pipes with an internal diameter of 3.6 mm and a height of 4 mm were used .
finally , following sealant placing in the plastic cylinders and curing them , the plastic matrix was dissected by the scalpel blade and finally separated . a cylinder with a diameter of 3.5 and a height of 4 mm was remained on the buccal or palatal surface of the teeth .
the roots were dissected from 2 cm below the c.e.j . by a diamond discus ( d and z diamond , germany ) and separated .
all samples were kept in distilled water for 24 h , before being prepared for micro tensile bond test .
a water syringe mounted onto a protractor to determine the exact rinsing angle the teeth were sectioned in x and y directions to obtain bonded sticks with a cross - sectional area of approximately 1.0 mm , measured to the nearest 0.01 mm with a digital caliper ( mitutoyo corp , japan ) .
the samples were then fixed on the plate of the micro tensile test machine ( bisco inc .
, usa ) conforming to the midline of the plates . in this machine , a pulling strength of 200 n with a speed of 0.5 mm / min was exerted to the samples .
the load ( n ) and the bonding surface area of the specimens in mm were noted and the microtensile bond strength calculated in mpa .
the type of failure in the samples was determined at a magnification of 90 by stereo microscope ( szx olympus , japan ) .
the failure mode was classified in three forms as follows : 
 adhesive ; failure between the enamel and the sealantcohesive ; failure inside the sealanta mixed form of adhesive and cohesive . 
 
adhesive ; failure between the enamel and the sealant cohesive ; failure inside the sealant a mixed form of adhesive and cohesive . in the case of a mixed failure mode ,
the amount of the remaining composite on the surface was calculated by a grid lens and expressed in percentage .
the normal distributions of bond strength and sealant remnant were verified using the kolmogrov - smirnov test and an all pair - wise multiple comparison post - hoc tukey test used to determine the statistical significance between the groups .
the normal distributions of bond strength and sealant remnant were verified using the kolmogrov - smirnov test and an all pair - wise multiple comparison post - hoc tukey test used to determine the statistical significance between the groups .
the results concerning the tensile bond strength of the samples mpa ( mean  sd ) are shown in table 1 .
tukey honestly significant difference test showed that the tensile bond strength in the group i was significantly higher than those in groups v and vi ( p < 0.05 ) .
kolmogroy - smirnov test results on the amount of tensile bond strength in different rinsing angles the percentage values of different failures at various rinsing angles and in total are demonstrated in table 2 . the most prevalent failure in the present study was a
furthermore , an increase in the rinsing angle from 15 to 90 , is associated with a reduction in the number of specimens with adhesive failures and an increase in  mixed  and  cohesive  failures [ figure 2 ] . based on table 3 ,
the highest average of residual composite percentage was at 90 while the lowest was at 15. percentage of different failures at various rinsing angles comparison of failure modes in different rinsing angles kolmogrov - smirnov test results on the % of the residual composite at different rinsing angles
the intention of this study was to improve caries preventive effect of sealants by improving their adhesion to the underlying enamel .
a move in this direction is needed as the interest of the dental profession in preventive dentistry is increasing .
considerable research has been undertaken to optimize the bond strength between resin based dental materials and dental enamel .
the ability of the resin to penetrate between the enamel crystallites and rods is a determinant of the bond strength between the resin and the etched enamel . to enhance the enamel surface free - energy and resin penetration ,
, we showed that a general trend exists between reduction in bond strength and the rinsing angle from 90 to 15 [ table 1 ] .
it seems that the increased tensile bond strengths , associated with the more thorough washing , were due to the increased rinsing angle . as shown in [ figure 3 ] , at 90
, the complete evacuation of the etching products can be achieve while the persistence of deposit remnants on enamel surface might possibly be a consequence of reduction in the rinsing angle .
these data ; therefore support the hypothesis that failure to remove the etched enamel surface deposits markedly reduces bonding between the sealant and the enamel .
indeed , scanning electron microscopy of etched enamel surfaces has shown the presence of such deposits after inadequate washing .
a : 90 , b : 75 , c : 60 , d : 45 , e : 30 , f : 15. increasing the angle from 15 to 90 results in discharging of more precipitates from the resin tags incomplete cleansing obscures the fine structure of the etched prism by a generalized precipitate layer so that the surface does not lend itself to mechanical bonding . the efficacy of sealants and resins has been evaluated by numerous mechanical testing methods , such as shear bond strength , tensile bond strength and micro - leakage . in this study , we used the micro tensile technique , a recent but widely employed test to evaluate the bond strength of adhesive materials to dental tissues . compared to other debonding tests , this method tends to increase adhesive failures . because of the small size of the specimens in the micro tensile test
, stress distributions are improved and failures occur in materials with true ultimate strength closer to the applied load . thus ,
the mean micro tensile bond strength varied between 23 mpa and 24.98 mpa [ table 1 ] . in spite of such high bond strength
this behavior may be attributed to the micro tensile test characteristics , which have been shown to produce a more homogeneous stress distribution and to the prismatic orientation of the intact enamel surface , which is mostly perpendicular to the enamel periphery and parallel to the applied stress .
these will result in higher bond strength and fewer cohesive failures . a possible explanation for the cohesive failures occurred in groups i and ii [ figure 2 ] may be the higher bond strength in these groups , which was probably stronger than the ultimate tensile bond strength of the adhesive , leading to failures in sealant material .
a reduction in the rinsing angle was coupled with more adhesive failures , which would be attributable to the lower bond strength observed in the acute angles .
light stereo microscopy of the specimens revealed that the presence of more sealant remnants at the failure site when a rinsing angle of 90 was used .
this indicates that bond failures in acute angles occur more frequently at the enamel adhesive interface consistent with the other findings in this study , showing that rinsing at 90 results in improved adhesion of sealant to the enamel surface .
it should be further noted that in view of the fact that many researchers consider a clinically successful bond as being between 15 mpa and 35 mpa , it seems that there was acceptable bond strength in the acutest rinsing angles . since
many variables encountered in the clinical cases can not be controlled for in - vitro , we are unable to make direct inferences from the information obtained in this study to the clinical cases
. therefore , future clinical trials that assess the longevity of sealants placed subsequent to washing with different rinsing angles are necessary .
within the limitations of this in - vitro study , the following conclusions can be drawn : 
 rinsing the etched enamel surface at an acute angle ( 15 and 30 ) reduces the bond strengtha direct relationship existed between the rinsing angle and percent values of sealant remnants on the tooth surface after failure , contributing to the bond strength of each grouphowever , there will be acceptable bond strengths in the acutest rinsing angle . 
 
rinsing the etched enamel surface at an acute angle ( 15 and 30 ) reduces the bond strength a direct relationship existed between the rinsing angle and percent values of sealant remnants on the tooth surface after failure , contributing to the bond strength of each group however , there will be acceptable bond strengths in the acutest rinsing angle .
 background and objectives : attempts to enhance bond strength of the sealant have been among the most important sides of dental research . 
 the purpose of the present study was to evaluate the effect of using different rinsing angles on the micro - tensile bond strength of the sealant to the etched enamel.materials and methods : sixty first - premolars were randomly assigned to six groups based on the rinsing angle applied ( 15 , 30 , 45 , 60 , 75 and 90 ) . following etching and rinsing , a 4-mm height build - up of sealant material was created . 
 bonded specimens were sectioned into sticks ( 1 mm  1 mm ) , which were subjected to micro - tensile bond strength , testing at a cross head speed of 0.5 mm / min.statistical analysis used : the data were analyzed by kolmogorov - smirnov and post - hoc tukey test.results:the tensile bond strength in specimens rinsed at 90 were statistically higher compared to those rinsed at 15 and 30 ( p < 0.05 ) and increasing the angle from 15 to 90 was correlated with a reduction in the number of specimens with adhesive failures.conclusions:rinsing the conditioned enamel surface at 90 may improve the bond strength and retention of the sealant . 
Introduction
Materials and Methods
Data analyses
Results
Discussion
Conclusion