Enamel cracks and ceramic bracket failure during debonding in vitro. The Effects of Composite Resin Types and Debonding Pliers on the Amount of Adhesive Remnants and Enamel Damages: A Stereomicroscopic Evaluation Evaluation of enamel damages following orthodontic bracket debonding in fluorosed teeth bonded with adhesion promoter The effects of bracket removal on enamel. Bond strength with APF applied after acid etching. Orthodontic bracket removal using conventional and ultrasonic debonding techniques, enamel loss, and time requirements. Remineralization of Artificial Caries in Primary Teeth by Grape Seed Extract: An In Vitro Study Fracture resistance of tooth fragment reattachment: effects of different preparation techniques and adhesive materials. [Efficacy of Tooth Mousse in reducing enamel demineralization and promoting remineralization]. In vivo debonding strength and enamel damage in two orthodontic debonding methods. Qualitative and quantitative evaluation of enamel after various post-stripping polishing methods: an in vitro study. Effects on shear bond strength and the enamel surface with an enamel bonding agent. Argon laser vs conventional visible light-cured orthodontic bracket bonding: an in-vivo and in-vitro study. A new one-step dental flowable composite for orthodontic use: an in vitro bond strength study. In vitro Comparison of Impact of Different Bleaching Agents on the Microhardness of Enamel. Effect of experimental fluoride-releasing tooth separator on acid resistance of human enamel in vitro. Shear bond strength of orthodontic brackets cemented with a zinc oxide-polyvinyl cement. Comparison of bracket debonding force between two conventional resin adhesives and a resin-reinforced glass ionomer cement: an in vitro and in vivo study. The Influence of Post Bleaching Treatments in Stain Absorption and Microhardness Effect of a fluoride varnish on demineralization adjacent to orthodontic brackets. Influence of force location in orthodontic shear bond strength testing. Comparison of bond strength between a conventional resin adhesive and a resin-modified glass ionomer adhesive: an in vitro and in vivo study. How Is the Enamel Affected by Different Orthodontic Bonding Agents and Polishing Techniques?
OBJECTIVE To test the null hypothesis that no difference in bracket failure characteristics is noted when use of a new ceramic bracket debonding instrument is compared with the use of conventional pliers . MATERIAL S AND METHODS Thirty maxillary premolars were r and omly assigned to one of two groups . In group 1 , Clarity collapsible ceramic brackets ( 3 M Unitek , Monrovia , Calif ) were debonded with the use of conventional Utility/Weingart ( 3 M Unitek , Monrovia , Calif ) pliers . In group 2 , Clarity brackets were debonded with a new Debonding Instrument ( 3 M Unitek ) . For all teeth , the same bracket bonding system was used . Following debonding , teeth and brackets were examined under 10x magnification for assessment of bracket failure ( fracture ) and of residual adhesive on the enamel surface . Enamel surfaces were visualized with transillumination prior to bonding and after removal of the residual adhesive , so the effect of the debonding forces could be determined . RESULTS The results of Adhesive Remnant Index comparisons indicated that a statistically significant difference ( chi2 = 8.73 ; P = .013 ) in bond failure patterns was apparent when the two groups were compared . Brackets debonded with the new instrument showed a greater tendency for the adhesive to be removed from the tooth during debonding . CONCLUSIONS The hypothesis is rejected . Although the incidence of enamel damage following debonding was similar in the two groups , the use of the new Debonding Instrument decreased the incidence of bracket fracture Background and aims . This in vitro study was design ed to evaluate the effect of composite resin types and orthodontic debonding pliers on the amount of adhesive remnants and enamel damages using a novel method of measurement . Material s and methods . 120 extracted human premolars were r and omly divided into four groups ( n = 30 ) . The st and ard edgewise metallic brackets were bonded to the teeth with light-cured composite resin “ Transbond XT ” in the first and second groups , and No-mix composite resin “ Unite ” in the third and fourth groups . Bracket debonding was carried out with Lift Off Debonding Instrument “ LODI ” ( 3 M Unitek ) in the first and third groups , and with Bracket Removing Pliers ( Dentaurum ) in the second and forth groups . yStereomicroscopic evaluation was performed by unbiased sterelogy . All teeth were evaluated for the amount of adhesive remnants and the number and length of enamel cracks . The obtained data on each step was analyzed by two-way ANOVA , chi-square , Wilcoxon , and Kruskal-Wallis . Results . Teeth in group 4 had the lowest adhesive remnants on the enamel surface ( p < 0.01 ) ; and the highest increase in the number of enamel cracks ( p < 0.01 ) among the groups . In addition , groups bonded with Unite showed the highest increase in the length of enamel cracks . Conclusion . Dentaurum debonding pliers with sheer – peel force , when used with the Unite adhesive ( group 4 ) , decreased the amount of adhesive remnants on the enamel surface while it increased enamel damages Objective : To evaluate shear bond strength ( SBS ) of the orthodontic brackets bonded to fluorosed and nonfluorosed teeth using Light Bond with and without adhesion promoters and compare their enamel damages following debonding . Material s and Methods : In this study , 30 fluorosed ( Thylstrup and Fejerskov Index = 4–5 ) and 30 nonfluorosed teeth were r and omly distributed between two subgroups according to the bonding material s : Group 1 , fluorosed teeth bonded with Light Bond ; Group 2 , fluorosed teeth bonded with adhesion promoters and Light Bond ; Group 3 , nonfluorosed teeth bonded with Light Bond ; Group 4 , nonfluorosed bonded with adhesion promoters and Light Bond . After bonding , the SBS of the brackets was tested with a universal testing machine . Stereomicroscopic evaluation was performed by unbiased stereology in all teeth to determine the amount of adhesive remnants and the number and length of enamel cracks before bonding and after debonding . The data were analyzed using two-way analysis of variance , Kruskal – Wallis , Wilcoxon Signed Rank , and Mann – Whitney test . Results : While fluorosis reduced the SBS of orthodontic bracket ( P = 0.017 ) , Enhance Locus Ceruleus LC significantly increased the SBS of the orthodontic bracket in fluorosed and nonfluorosed teeth ( P = 0.039 ) . Significant increasing in the number and length of enamel crack after debonding was found in all four groups . There were no significant differences in the length of enamel crack increased after debonding among four groups ( P = 0.768 ) while increasing in the number of enamel cracks after debonding was significantly different among the four groups ( P = 0.023 ) . Teeth in Group 2 showed the highest enamel damages among four groups following debonding . Conclusion : Adhesion promoters could improve the bond strength of orthodontic brackets , but conservative debonding methods for decreasing enamel damages would be necessary BACKGROUND Enamel cracks , which may develop during debonding orthodontic brackets , may jeopardise the integrity of the enamel and detract from the appearance of the teeth . AIM To compare the adhesive remnant scores ( ARI ) , the number , lengths and directions of enamel cracks before bonding and after debonding metal orthodontic brackets with three different methods . METHODS Metal brackets were bonded with a self-curing orthodontic adhesive to the buccal surfaces of 75 recently extracted upper and lower premolars . The teeth were r and omly divided into three groups , and the brackets removed either with a side-cutter , a single-blade bracket remover or a two-blade bracket remover . The number , directions and lengths of the enamel cracks before bonding and after debonding were compared . The number of ' pronounced ' cracks ( i.e. cracks that could be identified with the naked eye ) and the ARI scores in each group were also compared . RESULTS After debonding , the number of enamel cracks and pronounced cracks , and the lengths of the enamel cracks increased in all groups ( p < 0.001 ) . There were no statistically significant differences between the groups . The ARI scores and the direction of propagation of the enamel cracks were not influenced by the debonding method used ( p = 0.73 ) . CONCLUSIONS Concerns about the enamel damage caused by the three methods of debonding justify caution . Despite widespread use of these methods , it would be sensible to search for methods that result in less enamel damage One tenet of successful orthodontic therapy is to complete treatment without decalcification , hypocalcification , or discoloration of the natural dentition . Fluoride application has been shown to reduce demineralization of enamel . The purpose of this study was to see if fluoride could be incorporated into enamel before orthodontic bracketing without adversely affecting bond strength . Forty extract adolescent human premolars were r and omly divided into two equal groups with 20 teeth each . Group 1 served as control group , and group 2 ( experimental ) was immersed in 1.23 % acidulated phosphate fluoride for 4 minutes after acid etching . The buccal surfaces of all 40 teeth were then bonded with the same type of metal bracket and debonded with an Instron machine . The debonding interface was observed with scanning electron microscopy ( SEM ) . The mapping was calculated with energy dispersive x-ray spectrometry . The results showed that the bond strength of group 1 was significantly greater than that of group 2 . The enamel detachment ( enamel fracture ) was found in the experimental group only . Although the application of acidulated phosphate fluoride to a tooth can prevent dental decay or decalcification , the bond strength decreases and enamel detachment is found after debonding . The result shows that the application of acidulated phosphate fluoride after acid etching enamel has an adverse effect on orthodontic bond strength of human enamel The purpose of this study was to examine the effects of ultrasonic orthodontic bracket removal and cleanup and compare them with conventional debonding and cleaning of the enamel surfaces with burs and polishing disks . The amount of enamel loss and time for bracket removal and clean-up were also addressed . Thirty extracted human premolars were collected . The teeth were r and omly placed in one of the three debonding groups : debonding with orthodontic pliers and enamel clean-up with finishing burs and polishing disks ( group 1 ) , debonding with orthodontic pliers and ultrasonic clean-up of the enamel surface ( group 2 ) , and ultrasonic debonding enamel clean-up ( group 3 ) . The teeth were stored for 48 hours in 100 % humidity before bracket removal . All brackets were then removed . Polyvinyl siloxane impressions were made before and after bracket removal . Direct measurements of the teeth in micrometers were made at all steps . An additional 30 teeth were similarly prepared , and the brackets were debonded and cleaned-up as in the three groups previously described . The total time for bracket removal and enamel clean-up for each group was recorded in seconds . ( ABSTRACT TRUNCATED AT 250 WORDS Background and aims . Promoting remineralization is the ultimate goal of clinical prevention of caries lesion . The present in vitro study aim ed to investigate the effect of grape seed extract ( GSE ) on artificial enamel caries in primary human teeth . Material s and methods . Seventeen human sound primary incisors were sectioned mesiodistally . The tooth slices were placed in a demineralizing solution for 96 hours at 37ºC and 50 % relative humidity to create lesions . The demineralized fragments of each tooth were r and omly divided into two case ( immersed in GSE solution in phosphate buffer for 8 days ) and control ( immersed in distilled water ) groups . The sample s were subsequently evaluated using a scanning electron microscope and a micro-hardness tester . Data were analyzed using independent t-test . Results . The mean ± SD micro-hardness values for the case and control groups were 358.6±83.42 and 296.51± 69.41 , respectively . Grape seed extract significantly increased the micro-hardness of the lesions ( P=0.03 ) . The morphology  of GSE treated enamel was clearly different from that in the control group , and there were deposits of scaffolding insoluble complexes on the enamel surface . Conclusion . GSE enhanced the remineralization process of artificial enamel lesions of primary teeth , and thus , might be considered an effective natural agent in non-invasive dentistry The purpose of this study was to evaluate and compare the bond strengths of experimentally fractured human tooth fragments reattached with different adhesive material s and retentive techniques in vitro . Uncomplicated crown fractures were obtained on intact human m and ibular permanent incisors by applying perpendicular load to the buccal aspect of tooth crowns . Fractured teeth were r and omly assigned into one of three reattachment protocol s : ( i ) Simple reattachment , ( ii ) Overcontour preparation , and ( iii ) Internal dentin groove . The first and second groups were divided into 10 subgroups , and the third group into five subgroups ( n = 10 per group ) with respect to five different adhesive systems ( Prime&Bond NT , Adper Single Bond II , Adper Prompt L-Pop , Clearfil S(3 ) Bond , G Bond ) used with or without a hybrid resin composite ( Z250 ) . Restored teeth were subjected to thermal cycling , and subsequently to the same loading protocol used for fracturing intact teeth . Fracture strength after reattachment procedures was recorded as a percentage of the original fracture strength . Both type of adhesive material and placement of an intermediate layer of resin composite affected the fracture resistance ( P < 0.05 ) . The highest fracture strength recovery was obtained using the internal dentin groove technique ( 54 + /- 0.58 % , P < 0.05 ) , followed by the overcontour and simple reattachment protocol s ( 49 + /- 0.58 % and 32 + /- 0.82 % , respectively , P < 0.05 ) . Ultramorphological evaluation of bonded specimens revealed voids and microcracks along the adhesive interface , which might contribute to postadhesive failure OBJECTIVE To evaluate the efficacy of Tooth Mousse in reducing enamel demineralization lesions adjacent to bonded orthodontic brackets and promoting remineralization in vitro . METHODS 60 bovine teeth with bonded orthodontic brackets were r and omly divided into three groups , negative control group , positive control group and experimental group , applied separately with distilled water , Duraphat fluoride varnish , Tooth Mousse . 3 groups were dipped into an artificial caries solution and an artificial saliva solution , cycling between them . All sample s were detected by polarized light microscope , scanning electron microscope and electron probe micro- analysis . RESULTS Polarized light microscope showed that the enamel surface of the experimental group were completed , the areas of positive birefringence were decreased obviously . Scanning electron microscope showed that a large number of deposits were found on the dental enamel surface of the experimental group , filled in the small local concave of enamel surface . Compared with the control group , electron probe micro- analysis showed that calcium and phosphate concentration of enamel surface was higher in experimental group than in negative control group ( P<0.05 ) , there was no significant differences between experimental group and positive control group ( P>0.05 ) . CONCLUSION Tooth Mousse can reduce enamel demineralization and promoting remineralization in vitro Bracket debonding strength related to diverse debonding methods and enamel damage has not been assessed in vivo . The study hypothetized a direct relationship between these three parameters . Debonding strength was measured clinical ly in the wings method and base method on 50 patients in a split mouth method using a calibrated debonding plier . Brackets from 30 of these patients were scanned in SEM and EDAX for adhesive remnant index and enamel calcium remnants . Base method debonding force was significantly greater than wings method ( 163.5+/-68.7 N , 106.1+/-66.2 N , respectively , p < 0.001 ) . A positive adhesive remnant index score was found in both methods ( 68.7 % , 66.7 % , respectively ) . Debonding strength vs. adhesive remnant index or calcium index scores were not correlated . However , the latter two were significantly correlated ( 0.524 < R < 0.895 , p < 0.031 ) . Half of the debonding failures developed at the adhesive enamel interface . The results warnts the potential of enamel damage during debonding AIM The purpose of this study was to evaluate the ultramorphology and surface roughness of permanent tooth enamel after various post-stripping polishing methods . METHODS Sixty extracted , permanent lower incisors were r and omly assigned to two groups ( Group A and Group B ) . Group A was morphologically assessed by a scanning electron microscopy ( SEM ) and Group B was assessed by a stylus profilometer which applied a surface roughness test . Each group was divided into five subgroups of six incisors . Four of the subgroups were subjected to interpoximal enamel reduction , followed by various polishing methods ; the fifth subgroup served as a control . The polishing methods comprised ; Subgroup 1 , diamond disk followed by a fine Sof-lex disc ; Subgroup 2 , diamond disk and fine diamond bur ; Subgroup 3 , diamond disk and fine tungsten carbide bur ; Subgroup 4 , diamond disk and chemical stripping using 37 % orthophosphoric acid in conjunction with a fine 3 M finishing strip and Subgroup 5 ( control ) , no stripping nor polishing . Qualitative ( scanning electron microscopy ) and quantitative ( surface roughness test ) assessment s were performed . Surface roughness values ( Ra ) for permanent enamel were evaluated using the Welch analysis of variance ( ANOVA ) . RESULTS Subgroup 1 ( diamond disk and fine Sof-lex disc ) produced the smoothest enamel surface and Subgroup 4 ( chemical stripping ) produced the roughest enamel surface . CONCLUSIONS All proximal stripping and polishing methods significantly roughened the enamel surfaces . The best results were obtained when the stripped enamel surfaces were polished and finished with fine Sof-lex discs INTRODUCTION The purpose of this study was to evaluate the shear bond strength of orthodontic brackets and the effect of an enamel bonding agent ( EBA ) on enamel surface after debonding . METHODS Seventy-five extracted maxillary premolars were collected and r and omly divided into 3 groups of 25 . The enamel cracks were surveyed with a stereomicroscope . In the first group , 1 layer of EBA was applied before the adhesive resin . In the second group , 2 layers of EBA were used ; in the third group , no EBA was used . Bonding was followed by incubation for 48 hours at 37 degrees C and thermocycling for 1000 cycles . Debonding was performed with a shear force . The surfaces of the teeth were evaluated , and the length , depth , direction of cracks , and adhesive remnants on the enamel surface were recorded . Data were analyzed by using analysis of variance and paired sample s t tests . RESULTS There were no significant differences between the shear bond strengths ( P = 0.341 ) of the 3 groups , or in the direction , length , and depth of the cracks before and after debonding ( P > 0.05 ) . There was a significant increase in the number of cracks after debonding in the 3 groups ( P < 0.05 ) . The evaluation of adhesive remaining on the surface of the teeth indicated that most bond failures occurred at the resin-bracket interface . CONCLUSIONS The use of EBA does not enhance bond strength or provide greater protection to the enamel surface during debonding INTRODUCTION Many advantages of argon lasers have been reported , including high-speed orthodontic adhesive curing and less enamel demineralization . The purpose of this study was to compare bond strengths after curing with the argon laser ( 10 seconds ) and the conventional curing light ( 40 seconds ) in vivo and in vitro . METHODS Four premolars from each of 23 volunteers were r and omly assigned to either the argon laser group or the conventional light group for the in-vivo study . Shear bond strengths were measured after 14 days with custom- design ed debonding pliers . In-vitro bond strengths were measured by using 4 premolars from each of 25 volunteers .  Shear bond strength was measured after 14 days of thermocycling with the same protocol as the in-vivo study . Adhesive remnant index scores ( ARI ) were determined . RESULTS No significant differences were found in bond strengths according to curing method , dental arch , or sex . In-vivo results were significantly lower ( P < .05 ) than in-vitro results . A significant ( P < .05 ) difference in ARI scores between the curing methods was determined ; no significant correlation between mean bond strengths and ARI scores was determined . CONCLUSIONS Bond strength for argon laser curing is comparable to conventional light curing and is sufficient for clinical applications . Although the argon laser left more adhesive on the tooth surfaces on debonding , there was no increase in enamel surface fractures A new flowable composite , Denfil Flow , has shown an acceptable shear bond strength for bonding orthodontic brackets , when used with an intermediate , unfilled , low-viscosity resin . According to the manufacturer , it also shows a good viscosity for use with no preliminary adhesive . This could reduce the total time of bonding procedure while maintaining clinical ly useful bond strength . The aim of the current research was to assess this property . Eighty extracted human premolars were r and omly divided into four equal groups . Stainless steel brackets were bonded to etched enamel using ( 1 ) Denfil Flow , ( 2 ) a traditional flowable composite ( Dyract Flow ) , ( 3 ) Denfil Flow composite resin and an intermediate liquid resin , and ( 4 ) Transbond XT adhesive . Debonding was performed with a shearing force . The residual adhesive on the enamel surface was evaluated using the adhesive remnant index . The bond strength of Denfil Flow ( 34.8 MPa ) showed no significant difference with the other control groups and was clinical ly acceptable . Denfil Flow and Dyract Flow tended to display cohesive failure within the adhesive . Denfil Flow can be used without liquid resin to reduce the bonding procedure time while maintaining acceptable bond strength . Further studies are required to evaluate the enamel surface of the teeth after the same polishing procedure in the four groups BACKGROUND Various agents are used these days for increasing the esthetics . One such procedure is bleaching that offers various advantages , as it is minimal invasive and cheap option to color the teeth and remove stain . The altered enamel after the bleaching process shows surface demineralization and porosities . The present study aim ed to evaluate the effect of different bleaching agents on the microhardness of enamel . MATERIAL S AND METHODS A total of 100 freshly human extracted maxillary premolar teeth were selected for the study . Teeth with sound tooth structure were included for the study . All the specimens were r and omly divided into four groups with 25 specimens in each group depending upon the type of bleaching agent used : Group A , artificial saliva ( Control group ) ; Group B , 35 % hydrogen peroxide ( HP ) ; Group C , 25 % HP ; Group D , 10 % carbamide peroxide ( CP ) .  Knoop Hardness Number ( KHN ) was calculated at 24 , 48-hour , and 7-week interval . RESULTS Results showed no statistical significant differences between the microhardness of enamel of different groups ( p < 0.005 ) . A slight fall in the value of KHN was seen in all the groups , except for the control group , although the results were statistically nonsignificant ( p > 0.005 ) . CONCLUSION Although nonsignificantly , all the bleaching solutions produced some amount of alterations in the microstructure of enamel . More studies with higher study groups and more advanced estimation technologies are required to minimize microstructure alterations and promote for better outcome of bleaching procedures This study aim ed to investigate the fluoride-releasing ability of an experimental tooth separator consisting of polyurethane elastomer with tin fluoride and its effect on the acid resistance of human enamel . The tooth separator was set around an enamel slab and stored in de-ionized water for 10 days . The daily concentration of fluoride in the de-ionized water was measured . Then the enamel surface was artificially decalcified by a lactic acid buffer solution ( pH 4.5 ) for 96 hours . The mineral density at the surface layer of the enamel was measured to evaluate the acid resistance . The fluoride release increased with the amount of fluoride in the separator , but decreased with the immersion time . Both the enamel area contacting with the separator and its surrounding area showed lower mineral loss and lesion depth compared with the controls ( P < 0.05 ) . It is suggested that the experimental tooth separator would release enough fluoride and improve the acid resistance of the enamel surface layer The purpose of this study was to compare the shear bond strengths and enamel surface structure after debonding a conventional metal bracket and a polycrystalline ceramic bracket bonded with a bipolar zinc oxide-polyvinyl cement ( F-21 ) or a light-cured resin cement ( Transbond ) .  Forty extracted human premolars were used . The buccal enamel surfaces were used , and the teeth r and omly divided into four groups of 10 teeth each : group 1 : conventional metal bracket ( Unitek ) bonded with Transbond ; group 2 : metal bracket bonded with F-21 ; group 3 : ceramic bracket ( Transcend 2000 ) bonded with Transbond ; and group 4 : ceramic bracket bonded with F-21 . The brackets were bonded to the etched enamel surfaces according to manufacturer 's instructions . All specimens were stored in distilled water for 24 hours and then thermocycled for 300 cycles between 5 degrees C and 55 degrees C. The specimens were mounted in dental stone and placed in the Instron at a crosshead speed of 0.5 mm/min with a knife-edged blade . Immediately after debonding , the enamel surface and bracket-enamel interface were evaluated visually and with a stereomicroscope . Representative sample s were then examined with the scanning electron microscope . The analysis of variance and Student-Newman-Keuls tests were performed . The results in megapascals were Group 1 : 19,6 ( + /- 9,6 ) ; group 2 : 14,3 ( + /- 4,6 ) ; group 3 : 28,8 ( + /- 12,6 ) ; and group 4 : 18,5 ( + /- 7,5 ) . Group 3 was statistically significantly different ( P < 0.008 ) from all other groups . Groups 1 , 2 , and 4 were not significantly different . ( ABSTRACT TRUNCATED AT 250 WORDS The purpose of this study was to compare the debonding force of orthodontic brackets bonded with two conventional resin adhesives ( Resilience L3 and Light Bond ) and a resin-reinforced glass ionomer cement ( Fuji Ortho LC ) . For the in vitro part of the study , 80 extracted premolars were r and omly divided into four groups . In groups A and B , brackets were bonded to unetched enamel using Fuji Ortho LC cement in wet and dry conditions , respectively . In groups C and D , brackets were bonded to etched enamel using Resilience L3 and Light Bond , respectively .  Debonding force was determined using a servohydraulic testing machine at a crosshead speed of 1 mm/min . Data was analyzed using the ANOVA and Tukey-Kramer multiple comparison test at p<0.05 . A significant difference was found in debonding force between unetched Fuji Ortho LC and the two conventional resins . There was no significant difference between the two conventional resins or between unetched resin-reinforced glass ionomer in the wet and dry conditions . For the in vivo part of the study , 30 patients were r and omly assigned to one of the three bonding material groups . Bracket survival rates and distributions were obtained by following these patients for 1.2 years . Data was analyzed using the Kaplan-Meier product-limit estimates of survivorship function . Bond failure interface was determined using a modified adhesive remnant index ( ARI ) . These results showed no significant difference between survival rates and distributions among the three bonding material s with respect to the type of malocclusion , type of orthodontic treatment , or location of bracket . There were significant differences between survival distributions of males and females in the unetched Fuji Ortho LC group and among type of teeth in the conventional resin groups . The predominant mode of bracket failure for the unetched Fuji Ortho LC cement was at the enamel-adhesive interface , and for conventional resins , the enamel-adhesive interface and the bracket-adhesive interface . These results suggest that resin-reinforced glass ionomer cement can withst and occlusal and orthodontic forces despite having a bond strength lower than that of conventional resin adhesives Objectives : This study investigated the effects of post bleaching treatments to prevent restaining and the change of enamel surface microhardness after dental bleaching in vitro . Methods : Sixty intact human incisor teeth were stained in tea solution and r and omly assigned into four groups ( n=15 ) . Then sample s were bleached for two weeks ( 8 hours daily ) by 15 % carbamide peroxide . Tooth color was determined both with a spectrophotometer and visually before bleaching ( T1 ) and immediately after bleaching ( T2 ) . Next , it was applied in group 1 fluoride ( Naf 2 % ) gel for 2 minutes , and in group 2 a fractional CO2 laser ( 10 mJ , 200 Hz , 10 s ) , and in group 3 , nanohydroxyapatite gel for 2 minutes . The bleached teeth in group 4 remained untreated ( control group ) . Then teeth placed in tea solution again . Color examinations were repeated after various post bleaching treatments ( T3 ) and restaining with tea ( T4 ) and color change values recorded . The microhardness was measured at the enamel surface of sample s. Data was analyzed using ANOVA , Tukey HSD test and Dunnett T3 ( α = 0.05 ) . Results : Directly after bleaching ( ΔE T3-T2 ) , the treatment with nanohydroxyapatite showed significantly the least color lapse in colorimetric evaluation . In experimental groups , the color change between T3 and T4 stages ( ΔE T4-T3 ) was significantly lower than control group ( P < 0.05 ) . Different methods of enamel treatment caused a significant increase in surface microhardness compared to control group ( P < 0.05 ) . Significance : Application of fluoride , fractional CO2 laser and nanohydroxyapatite as post bleaching treatments are suggested for prevention of stain absorption and increasing the hardening of bleached enamel Home fluoride regimens have long been used to reduce the amount of demineralization adjacent to orthodontic appliances . In the absence of patient compliance , another method of applying the fluoride must be used . The purpose of this study was to evaluate , in vitro , the ability of a fluoride varnish , Duraflor , to directly inhibit demineralization of enamel surrounding orthodontic brackets . Brackets were bonded to 36 extracted human canines and premolars with a traditional composite resin and r and omly assigned to three equal groups of twelve . Group 1 served as the control with no topical application after bonding . Group 2 was treated with a single application of a nonfluori date d placebo varnish . Group 3 was treated with a single application of Duraflor . All groups were cycled in an artificial caries challenge for 1 hour two times daily for 37 days and were brushed with a medium bristled toothbrush to simulate mechanical wear of the varnish . Demineralization of enamel was evaluated in longitudinal buccolingual tooth sections using polarized light microscopy . Both average depth and area of demineralization were measured with a sonic digitizer . ANOVA ( P < /=. 0001 ) and Duncan 's test ( P < /=.05 ) indicated significant differences in depth and area of demineralized enamel . Those teeth treated with Duraflor exhibited 50 % less demineralization than the control teeth and an even greater difference when compared to the placebo group . Fluoride varnishes should be considered for use as a preventive adjunct to reduce enamel demineralization adjacent to orthodontic brackets , particularly in patients who exhibit poor compliance with oral hygiene and home fluoride use OBJECTIVE The purpose of the present study was to analyze the influence of debonding force location in shear bond strength testing of orthodontic brackets in vitro . METHODS Ninety extracted permanent bovine m and ibular incisors were r and omly divided into 3 groups of 30 specimens each . Teeth were bonded with stainless steel orthodontic brackets . Enamel surfaces were etched with 37 % phosphoric acid for 30s and bonded with a composite adhesive .  Debonding force measurements were performed with a universal testing machine . Location of the debonding force was : bracket base ( group A ) , ligature groove ( group B ) , occlusal bracket wings ( group C ) . RESULTS Mean shear bond strength measurements were as follows : 22.70(4.23)MPa ( group A ) , 11.52(2.74)MPa ( group B ) , 9.44(2.96)MPa ( group C ) . Analysis of variance indicated that there were significant differences in shear bond strength . Post-hoc Tukey tests showed that bond strength measurements of group A were significantly different from those of groups B and C. The adhesive remnant index also showed significant differences and ranged from a mean of 1.53 in group A to a mean of 2.10 in group C. SIGNIFICANCE Debonding force location had a significant influence on shear bond strength measurements and bond failure pattern , indicating that this parameter needs to be taken into consideration for inter study comparison of in vitro results The objectives of this study were ( 1 ) to compare the in vivo survival rates of orthodontic brackets bonded with a resin-modified glass ionomer adhesive ( Fuji Ortho LC ; GC America , Alsip , Ill ) after conditioning with 10 % polyacrylic acid and a conventional resin adhesive ( Light Bond ; Reliance Orthodontic Products , Itasca , Ill ) bonded with 37 % phosphoric acid , ( 2 ) to compare the in vitro bond shear/peel bond strength between the 2 adhesives , ( 3 ) to determine the mode of bracket failure in the in vivo and in vitro tests according to the adhesive remnant index ( ARI ) , and ( 4 ) to compare the changes in surface morphology of enamel surface after etching or conditioning with 10 % polyacrylic acid , with scanning electron microscopy . In the in vitro study , 50 extracted premolars were r and omly divided into 4 groups : brackets bonded with Fuji Ortho LC or Light Bond adhesive that were debonded after either 30 minutes or 24 hours . Bond strengths were determined with a testing machine at a crosshead speed of 1 mm/min . Data were analyzed with analysis of variance and a paired Student t test . The in vivo study consisted of 398 teeth that were r and omly bonded with Fuji Ortho LC or Light Bond adhesive in 22 subjects with the split-mouth technique . Bracket survival rates and distribution were followed for 1.3 years . Data were analyzed with Kaplan-Meier product-limit estimates of survivorship function . The in vitro study results showed significant differences ( P < .05 ) among the adhesives and the debond times . Light Bond had significantly greater bond strengths than Fuji Ortho LC at 24 hours ( 18.46 + /- 2.95 MPa vs 9.56 + /- 1.85 MPa ) and 30 minutes ( 16.19 + /- 2.04 MPa vs 6.93 + /- 1.93 MPa ) . Mean ARI scores showed that Fuji Ortho LC had significantly greater incidences of enamel/adhesive failure than Light Bond adhesive ( 4.9 vs 4.1 ) . For the in vivo study , no significant differences in failure rate , sex , or location in dental arch or ARI ratings were found between the 2 adhesives . These results suggest that , compared with conventional resin , brackets bonded with resin-modified glass ionomer adhesive had significantly less shear bond strength in vitro . However , similar survival rates of the 2 material s studied after 1.3 years indicate that resin-reinforced glass ionomers can provide adequate bond strengths clinical ly . The weaker chemical bonding between the adhesive and the enamel might make it easier for clinicians to clean up adhesives on the enamel surface after debonding Objectives : The objective of this study was to assess the effect of new bonding techniques on enamel surface . Material s and Methods : Sixty upper central incisors were r and omly divided into two equal groups . In the first group , metal brackets were bonded using TransbondXT and , in the second group , the same brackets were bonded with Maxcem Elite . The shear bond strength ( SBS ) of both agents to enamel was measured and the number and length of enamel cracks before bonding , after debonding and after polishing were compared . The number of visible cracks and the adhesive remnant index ( ARI ) scores in each group were also measured . Results : There were significantly more enamel cracks in the Transbond XT group after debonding and polishing compared to the Maxcem Elite group . There was no significant difference in the length of enamel cracks between the two groups ; but , in each group , a significant increase in the length of enamel cracks was noticeable after debonding . Polishing did not cause any statistically significant change in crack length . The SBS of Maxcem Elite was significantly lower than that of Transbond XT ( 95 % confidence interval ) . Conclusion : Maxcem Elite offers clinical ly acceptable bond strength and can thus be used as a routine adhesive for orthodontic purpose s since it is less likely to damage the enamel
Conclusions There is weak evidence indicating length and width of EMCs increase following bracket removal and the scientific evidence concerning quantitative evaluation of the number parameter before and after debonding is insufficient .
However , there is a strong evidence that after debonding the number of EMCs is likely to increase .
Objectives To evaluate and compare the enamel microcracks ( EMCs ) characteristics ( qualitative and quantitative ) in the form of tooth damage before and after debonding from human teeth of in vitro studies .