***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: PURPOSE To examine the reduction in enamel demineralization provided by fluoride release from a conventional glass-ionomer , a resin-modified glass-ionomer and an experimental fluoride-releasing resin-based composite compared to a conventional resin-based composite control , and to correlate the level of fluoride release with demineralization . MATERIAL S AND METHODS Enamel surfaces of extracted human incisors had a 0.4 mm thick layer of the specified test material carefully placed in a b and across the mid-facial enamel to simulate a cement layer beneath an orthodontic bracket . The top surface of the test material was covered with nail varnish , leaving only the edges of the material exposed to release fluoride . The teeth were additionally covered with nail varnish to within 1 mm of the test material . Each group of teeth was placed into separate volumes of unstirred demineralizing solution at a pH of 4.7 for 4 days . The specimens were sectioned and examined by polarized light microscopy . Lesion areas were measured at distances from 100 - 800 microm away from the test material . Fluoride release for the test material s was measured for periods up to 5 months . RESULTS All of the fluoride-releasing material s demonstrated a statistically significant ( P < 0.05 ) degree of protection of enamel from demineralization compared to the non-fluoride control material . The degree of protection was greatest near the material , but lesion areas increased with distance in an inverse relationship to the amount of fluoride release . Lesions were displaced from the region near the material s and the mean displacement was directly related to amount of fluoride release . The mean lesion areas for each distance decreased with the logarithm of the cumulative fluoride release The prevalence of enamel decalcification beneath orthodontic b and s has indicated the need for a fluoride-releasing , enamel-adhesive orthodontic luting cement . The purpose of this study was to compare the retentive bond strengths of orthodontic b and s cemented with two new fluoride-releasing cements , a zinc polycarboxylate and a glass ionomer , with the retentive bond strength of b and s cemented with the st and ard orthodontic cement zinc phosphate . The site of cement failure was also evaluated . One hundred eighty extracted human molar teeth were embedded in resin blocks and r and omly assigned to three cement groups . Adapted b and s were cemented by a clinical ly acceptable technique . The cemented teeth were then assigned to one of three time intervals--24 hours , 7 days , and 60 days-- and thermocycled in synthetic saliva . The force required to initially fracture the cement bond was used as a measure of cement retention . By means of the Instron , a tensile load was applied to each cemented b and . The maximum retentive strength ( cement failure ) was interpreted from the stress-strain curve at the point where linearity deviated . The failure site was judged subjectively : between cement and enamel , within the cement , or between cement and the b and . Using stress at failure , an analysis of variance showed no significant differences among the retentive strengths of the three cements . The chi-square test revealed a significant difference ( P less than 0.01 ) between failure sites of the zinc phosphate and glass ionomer cements . Significantly more b and s cemented with the glass ionomer failed at the cement/b and interface , leaving the cement adhered to the tooth . ( ABSTRACT TRUNCATED AT 250 WORDS The aim of this investigation was to examine the fluoride uptake by enamel after application of glass ionomer cement for orthodontic b and cementation compared with zinc phosphate cement . The study was conducted on 21 children whose mean age was 14 years . All the children were reared in the Middle Anatolian cities where the water fluoride concentration was below the level of 0.50 ppm . The subjects were r and omly divided into three groups . The first experimental group , had seven subjects whose teeth were topically fluori date d with 2 per cent NaF solution , before orthodontic b and cementation with zinc phosphate cement . The second experimental group also had seven subjects whose orthodontic b and s were cemented with glass ionomer cement . The third group , consisted of seven control subjects and no dental procedures were performed in this group . All the participants were followed for 3 months and at the end of this period maxillary first premolars , which were in the ninth developmental stage according to Nolla ( 1960 ) , were extracted for orthodontic purpose s. The enamel fluoride concentrations were determined on the left maxillary first premolars at three successive etch depths by means of a fluor ion electrode , whereas the calcium concentrations were determined with an atomic absorption spectrophotometer . The results of this investigation showed that in both cementation groups enamel fluoride concentrations at three successive etch depths were highly increased compared with the control group . However , the difference between the cementation groups was not statistically significant Failure of orthodontic b and s occurs most frequently at the b and -cement interface , when conventional glass ionomer cements are used . Modification of the b and surface may improve clinical performance by increasing the mechanical interlock at this junction . The aim of this prospect i ve study was to compare the retention of micro-etched and untreated first molar orthodontic b and s in a r and omized , half-mouth trial . Seventy-nine patients had 304 b and s cemented as part of routine fixed appliance therapy . The effect of micro-etching , patient age and gender , operator , molar crossbite , treatment mechanics , and arch on b and failure was investigated . Failure rates and survival times were compared for each variable assessed . Micro-etched molar b and s showed a significant reduction in clinical failure rate over untreated molar b and s and an increase in mean survival time ( P < 0.001 ) . Of the other variables examined , only the presence of a molar crossbite had any significant effect on b and failure ( P = 0.004 ) In this study 1,976  b and s were cemented onto the teeth of 102 patients . The mean duration of active treatment for a case was 702 ( ± 182 ) days , during which time 419 b and s , i.e. 21·2 per cent were recemented . B and s which required most frequent recementing were those affixed to the upper central incisor teeth . Of the 102 b and s cemented on the upper central incisors 28·4 per cent remained intact , while 71·6 per cent required recementing . The possible causes for the high incidence of recementation of the incisor b and s are discussed . The performance of the direct attachment technique in relation to the conventional orthodontic b and is review ed in the light of the data presented in this survey The objective of this study was to compare the shear-peel b and strength of 5 orthodontic cements using both factory and in-office micro-etched b and s. The 5 orthodontic cements evaluated were a zinc phosphate ( Fleck 's Cement ) , 2 resin-modified glass ionomer cements (RMGI)(3 M Multicure glass ionomer and Optib and ) , and 2 polyacid-modified composite resin cements (PMCR)(Transbond Plus and Ultra B and Lok ) . Salivary contamination was examined with a polyacid-modified composite resin ( Transbond Plus ) .  Two hundred and eighty extracted human molar teeth were embedded in resin blocks and each was r and omly assigned to the following 7 groups : 6 groups with factory etched b and s , 5 cement groups and salivary contaminated group , and 1 in-office micro-etched  group . The cemented teeth were put in deionized water at 37 degrees C for 30 days and thermocycled for 24 hours . The force required to break the cement bond was used as a measure of shear-peel b and retention . With the use of an Instron testing machine , a shear-peel load was applied to each cemented b and . Data were analyzed with a one-way analysis of variance ( ANOVA ) with a Tukey test for the multiple comparisons . The RMGIs and PMCRs demonstrated significantly greater shear-peel b and strengths compared to the zinc phosphate cement . No statistically significant differences were noted between the RMGI cement and PMCR cements and within the RMGI groups , however , there was a statistically significant difference within the PMCR groups . Significantly lower b and strengths were noted with the saliva contaminated PMCR cement group ( Transbond Plus ) and the in practice s and blasted PMCR group . Both RMGIs and PMCRs were found to demonstrate favorable b and ing qualities . The lower b and strength with saliva-contaminated b and s suggests that moisture control is critical when using a PMCR . The variability noted in the in-office micro-etched b and s might be technique related The purpose of this study was to investigate the cariostatic effect of two glass ionomer cements on in vivo demineralization of partly uncovered enamel beneath orthodontic b and s. A 4-week clinical trial was conducted on a group of five patients with nine pairs of premolars to be extracted for orthodontic purpose s. Specially design ed orthodontic b and s were cemented with either Ketac-Cem ( K-C ) or Aqua-Cem ( A-C ) . A local cariogenic milieu was created between the buccal surface of the premolars and the inner surface of the b and s to secure plaque accumulation . The mineral content of the teeth was quantified by microradiography . The data were compared with data from a previous study of patients in the same age group with b and s that had been cemented with a non-F cement . After comparison with the non-F group , the lesion depth ( ld ) was reduced by 63 % for K-C and by 55 % for A-C. This reduction was statistically significant at the 2.5 % level ( t test ) . The total mineral loss in teeth cemented with  glass ionomer cements ( delta Z ) was reduced , in comparison with the loss in teeth cemented with non-F cement , by 49 % with K-C and by 27 % with A-C. The differences were statistically significant only for the K-C group ( t test , p less than 0.025 ) . There were no significant differences between the two glass ionomer cements with respect to either lesion depth or total mineral loss values ( paired t test ; p greater than 0.05 ) . This investigation shows that fluoride released from glass ionomer cements contributes substantially to demineralization " reduction . " However , these cements do not provide complete caries protection in sites where access is difficult The purpose of this study was to examine the effectiveness of a new glass polyphosphonate cement ( Diamond ) for orthodontic b and ing . Thirty-one subjects underwent in vivo testing to compare the failure rate of b and s cemented using the test cement and b and s cemented using a conventional glass polyalkenoate cement ( Ketac-Cem ) over a 6-month period at the beginning of active appliance therapy . In an ex vivo experiment 60 extracted teeth were b and ed using either the test cement or a glass polyalkenoate cement , and subjected to a deb and ing force using a Lloyd universal testing machine until failure . In the in vivo study the overall proportion of failure of the b and s cemented with each cement was identical at 0.048 . However , in the ex vivo study the probability of failure for the glass polyphosphonate cement was significantly higher than for the glass polyalkenoate cement , and the force to deb and the glass polyalkenoate cement was greater than that of the glass polyphosphonate cement . In the clinical setting the new glass polyphosphonate cement performed as well as a conventional glass polyalkenoate cement , and these results suggest that it could be used as an alternative cement for orthodontic b and ing . The results of the ex vivo test bring into question the usefulness of this laboratory test as an indicator of clinical performance The aim of this investigation was to determine the effectiveness of a conventional glass poly(alkenoate ) cement ( Intact ) and newer polyacid-modified composite resin cements ( Transbond Plus and Ultra B and -Lok ) to retain orthodontic b and s. In the in vitro part of this study , stainless steel b and s were cemented to 240 extracted third molar teeth in three test groups comprising Intact , Transbond Plus and Ultra B and -Lok . The force to deb and ( N ) for all three cements was recorded using an Instron universal testing machine after the following observation periods : 20 minutes and 3 , 6 and 12 months . The results indicated that all three cements increased their median force to deb and after 12 months . Of the two compomers , Transbondtrade mark Plus demonstrated the highest median force to deb and at all four time intervals . In the in vivo part of the study , 30 patients participated in a r and omized cross-mouth clinical trial where the molar b and s were cemented in place using either Intact or Transbond Plus . Ultra B and -Lok was not used in the clinical part of the study . The results showed there to be no clinical ly significant difference in b and failure rates between the two cements . When patients were asked to score each for taste , there was a significant difference , with the glass poly(alkenoate ) cement ( Intact ) being more acceptable than the polyacid-modified composite Transbond Plus ( P < 0.001 ) . No significant differences were observed in the in vitro median force to deb and or in vivo b and failure rates between the glass poly(alkenoate ) cement and the polyacid-modified composite resins . The choice of cementing agent can therefore be made on patient factors , e.g. taste , or operator factors , e.g. ease of h and ling , cost and shelf life The time to first failure , the position of b and failure at deb and , and the change in enamel white spot lesions of teeth bonded with a modified composite or a conventional glass ionomer 
    Output:
    
There is insufficient high quality evidence with regard to the most effective adhesive for attaching orthodontic b and s to molar teeth .