***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: The aims of this study were : ( 1 ) to correlate surface ( SH ) and cross-sectional hardness ( CSH ) with microradiographic parameters of artificial enamel lesions ; ( 2 ) to compare lesions prepared by different protocol s. Fifty bovine enamel specimens were allocated by stratified r and omisation according to their initial SH values to five groups and lesions produced by different methods : MC gel ( methylcellulose gel/lactic acid , pH 4.6 , 14 days ) ; PA gel ( polyacrylic acid/lactic acid/hydroxyapatite , pH 4.8 , 16 h ) ; MHDP ( undersaturated lactate buffer/methyl diphosphonate , pH 5.0 , 6 days ) ; buffer ( undersaturated acetate buffer/fluoride , pH 5.0 , 16 h ) , and pH cycling ( 7 days ) . SH of the lesions ( SH1 ) was measured . The specimens were longitudinally sectioned and transverse microradiography ( TMR ) and CSH measured at 10- to 220-μm depth from the surface . Overall , there was a medium correlation but non-linear and variable relationship between mineral content and √CSH . √SH1 was weakly to moderately correlated with surface layer properties , weakly correlated with lesion depth but uncorrelated with integrated mineral loss . MHDP lesions showed the highest subsurface mineral loss , followed by pH cycling , buffer , PA gel and MC gel lesions . The conclusions were : ( 1 ) CSH , as an alternative to TMR , does not estimate mineral content very accurately , but gives information about mechanical properties of lesions ; ( 2 ) SH should not be used to analyse lesions ; ( 3 ) artificial caries lesions produced by the protocol s differ , especially considering the method of analysis This paper describes a microradiographic method for measuring mineral concentration in a transversal geometry with thick ( ≤3.2 mm ) sections : transversal wavelength-independent microradiography ( T-WIM ) . It was tested on bovine enamel and dentin sample s in vitro , and the results were vali date d with those of transversal microradiography ( TMR ) .  48 enamel and 48 dentin sample s ( 3.2 × 3.2 × 1.5 mm ) were embedded in acrylic resin  , r and omly divided into six groups of 8 dentin or 8 enamel sample s , and demineralized for 0 ( sound control ) , 1 , 2 , 3 , 4 , or 5 weeks . For T-WIM , sample s were imaged on film with polychromatic 40-kV Cu X-rays with an Al ( 0.25 mm)/Ni ( 0.02 mm ) filter together with an aluminium/zinc step wedge . TMR slices ( about 80 µm for enamel and about 130 µm for dentine ) were subsequently cut from the centre of the sample s and subjected to TMR . Microradiographs from both methods were digitized and image analysis software was used to calculate lesion depth and mineral loss . The relations between T-WIM and TMR  results for mineral loss ( ΔZ ) and lesion depth were nearly linear ( r ≧ 0.96 ) for both enamel and dentin . The slopes of the regression lines were between 0.99 and 1.02 except for ΔZ in dentine , which was 0.89 . It was concluded that T-WIM is a suitable method for TMR on thick sample PURPOSE To evaluate the in situ effect of fluoride and MDPB-containing adhesives on antibacterial activity around  restorations in conditions of high caries risk . METHODS Bovine enamel and dentin blocks were restored with a fluoride-containing ( One-up Bond F Plus - OP ) or a MDPB and fluoride-containing adhesive ( Clearfil Protect Bond - PB ) .  Volunteers ( n = 17 ) wore an intra-oral appliance containing three enamel and three dentin blocks , aligned side-by-side and restored with OP or PB and one enamel and dentin block ( controls ) . The cariogenic challenge was carried out in two phases of 14 days each . The counts of total streptococci ( TM ) , mutans streptococci ( MS ) and lactobacilli ( LB ) were analyzed in the biofilm formed . Cross-sectional microhardness ( CSM ) and polarized light microscopy ( PLM ) evaluated caries lesions around the restorations and the demineralization extension . Data obtained by CSM testing was analyzed by Split-Split Plot ANOVA ( P < 0.05 ) . PLM and microbiota results were analyzed by Wilcoxon test ( P < 0.05 ) . RESULTS TM and MS counts were highest for the OP enamel restorations , and these presented higher lesion depths than PB in both the enamel and dentin . The CSM in dentin was the lowest at 60 μm from the restoration wall . None of the adhesives prevented demineralization and bacteria growth , but PB reduced the amount of oral pathogens in enamel and demineralization around restorations in enamel and dentin This study evaluates in situ the effect of erbium-doped yttrium aluminum garnet ( Er : YAG ) laser parameters on the development of caries-like lesions adjacent to dental restorations . One hundred fifty bovine enamel slabs were r and omly allocated among 15 volunteers . The specimens were subdivided into ten groups : nine experimental groups prepared with Er : YAG laser ( 300 mJ output , frequency of 2 , 4 or 6 Hz , water flow rate of 2.0 , 5.0 , or 8.0 mL/min ) and one control group ( high-speed h and piece ) . The prepared cavity was restored with a composite resin , and the slabs were mounted on palatal appliance to be installed in the volunteers to the cariogenic challenge . After this , the specimens were sectioned to the longitudinal microhardness measurements . Data were su bmi tted to Friedman and Wilcoxon paired tests . All groups prepared with Er : YAG laser demonstrated microhardness values higher than those prepared with high-speed h and piece , which showed the lowest microhardness values ( 24.86 ) . The group prepared with Er : YAG laser ( 2 Hz–2.0 mL/min ) showed the highest microhardness values ( 152.43 ) , followed by those prepared with Er : YAG laser ( 2 Hz–5.0 mL/min ) ( 133.08 ) and Er : YAG laser ( 2 Hz–8.0 mL/min ) ( 91.61 ) , respectively . The groups Er : YAG laser with 4 and 6 Hz of frequency and water flow rates of 2.0 , 5.0 , and 8.0 mL/min showed microhardness values lower than the groups cited above and showed statistical similarity among them . The Er : YAG laser parameters employed to cavity preparation influenced the acid resistance of the irradiated substrate , and the Er : YAG laser was capable to control the development of caries-like lesions around composite resin restorations PURPOSE To investigate in situ the influence of gaps in the development of secondary caries lesion in adhesive restorations . METHODS 10 volunteers utilized intra-oral appliances , containing three human dental blocks ( enamel and dentin ) , representing the three different groups ( two restored , one sound ) : ( 1 ) restored with resin composite using the total acid etch adhesive technique ( 37 % H3PO4 + Single Bond + Z250 ) ; ( 2 ) restored with resin composite but without acid etching ( Single Bond + Z250 ) ; ( 3 ) and sound blocks ( control group ) . The dental blocks ( n=30 ) were r and omly positioned inside the intra-oral appliances , and covered by a porous tissue ( gabardine base ) to induce a cariogenic biofilm . The volunteers used the appliances 24 hours daily for a 28-day period , removing just during meals and oral hygiene . Eight times a day , a 20 % sucrose solution was dripped onto the blocks . Five minutes later , the appliance was washed with distilled water and replaced in the oral environment . After the experimental period , the dental blocks were removed from the appliance and examined by visual examination to detect the presence or the absence of an active carious lesion ( kappa= 0.89 ) . Posteriorly , they were prepared for the polarized light microscopy examination , which was performed to describe enamel surface characteristics on the restored and unrestored blocks with active caries lesion ( kappa= 1 ) . RESULTS The visual examination demonstrated that almost all ( 29/30 ) of the blocks showed non-cavitated active caries lesion on the enamel surface . The microscopic evaluation showed non-cavitated caries lesions on enamel surfaces for all groups . In the restored blocks ( with and without the total etch technique ) , the demineralization was first identified as an outer lesion that follows the enamel prism directions , and in some cases , reached the cavity walls . The results showed that caries lesion development adjacent to the restoration was determined by the cariogenic challenge of the oral environment , instead of the restoration adhesive quality , and the wall lesion was determined by the prism orientation , regardless of the presence of gaps OBJECTIVE This study assessed the effect of the Er : YAG laser on enamel adjacent to restorations su bmi tted to cariogenic challenge in situ , by microhardness analysis . BACKGROUND DATA The influence of Er : YAG laser energy on secondary caries formation has been investigated in vitro . However , no research involving demineralization around cavities prepared with the Er : YAG laser under intra-oral conditions has yet been described . MATERIAL S AND METHODS Slabs of enamel were r and omly assigned to seven groups ( n = 12 ) , according to the cavity preparation technique : groups I , II , and III -- Er : YAG laser , 250 mJ , at 2 , 3 , and 4 Hz , respectively ; groups IV , V , and VI--350 mJ , at 2 , 3 , and 4 Hz , respectively ; group VII -- high-speed h and piece ( control ) . Cavities were restored and the specimens were fixed in intra-oral appliances and worn by 12 volunteers for 14 d. Sucrose solution was applied to each slab 6 times/d . Sample s were removed , sectioned , and examined for microhardness at 100 , 200 , and 300 microm ( factor distance ) , and 30 , 60 , and 90 microm ( factor depth ) , from the restoration and enamel surface , respectively . RESULTS Analysis of variance according to a split-plot model showed no difference among the cavity preparation techniques , among distances , or among depths , as well as no difference in the interaction between the factors of cavity preparation and distance . A significant difference was found in the interaction of cavity preparation and depth ( p < 0.0001 ) , as identified by contrast technique . CONCLUSION The results revealed that the Er : YAG laser did not differ from conventional cavity preparation with regard to enamel microhardness AIM This in situ study assessed the effects of adhesive systems containing or not fluoride and /or the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide ( MDPB ) on the microbiological composition of dental biofilm and enamel demineralization . MATERIAL S AND METHODS During two phases of 14 days , ten volunteers wore intraoral palatal appliances containing two slabs of human enamel according to a double-blind , crossover design . The slabs were r and omly restored using a composite resin and one of the following adhesive systems : All-Bond SE(TM ) ( self-etch , fluoride/MDPB free adhesive , AB ) and Clearfl Protect Bond ( self-etch containing fluoride and MDPB adhesive , CB ) . The biofilm formed on the slabs was analyzed with regard to total and mutans streptococci and lactobacilli counts . Demineralization represented by integrated area of hardness × lesion depth Delta S ( ΔS ) was determined on enamel by analysis of cross-sectional microhardness , at 20 and 70 μm from the restoration margin . Data were analyzed by ANOVA . RESULTS No statistically significant difference was found either in enamel demineralization or in the microbiological composition of dental biofilm . CONCLUSION All adhesive systems containing or not fluoride and /or MDPB tested were unable to inhibit secondary caries in the in situ model used in the present research OBJECTIVES Since secondary caries is one of the main reasons for replacing restorations , this study assessed the effects of different restorative material s on the microbiological composition of dental biofilm and on enamel demineralisation around the restoration . METHODS A r and omized , double-blind , split-mouth in situ design was conducted in one phase of 14 days , during which , 20 volunteers wore palatal devices containing five human dental enamel slabs . Each slab was r and omly restored with one of the following material s : Filtek-Z-250/Single Bond , control group ( composite resin ) , Permite ( amalgam ) , Fuji II ( encapsulated resin-modified glass ionomer ) , Vitremer ( resin-modified glass ionomer ) and Ketac Molar ( conventional glass ionomer ) . The volunteers used fluoride dentifrice , 3x/day and a 20 % sucrose solution was dripped onto the slabs 8x/day . The biofilm formed on the slabs was analyzed to determine the counts of total streptococci , mutans streptococci and lactobacilli . Enamel demineralisation was determined by cross-sectional microhardness 
    Output:
    
Discussion : Studies conducted with palatal models showed caries progression rates 2–5 times higher than the estimated clinical progression rates .