***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: OBJECTIVES The aim of this prospect i ve cohort study was to compute the long-term clinical survival and complication rates of alumina-toughened zirconia abutments used for implant-supported restorations and to evaluate the effects of several clinical variables on these rates . MATERIAL AND METHODS From May 1998 to September 2010 , 213 patients aged 18 years or older were recruited . The patients received 611 external hex implants and 328 implant-supported fixed restorations using alumina-toughened zirconia abutments .  During the follow-up , each restoration was coded as a dental event , which included loosening or fracture of abutment screws , and abutment fracture . From the coded data , the effects of the investigated clinical variables-restored area ( anterior/posterior ) , number of prosthodontic units ( one/two units or over ) , prosthesis type ( single-unit/multiunit without pontic/multiunit with pontic ) , implant system , and patient gender-on the survival of the abutments were evaluated . Survival analysis using Kaplan-Meier method and Cox proportional hazard model was applied . The 5-year survival and complication rates of the abutments were assessed . RESULTS The number of prosthodontic units and the type of prosthesis had a significant association with complication rates ( P < 0.05 ) . Kaplan-Meier survival analysis estimated that the cumulative 5-year complication rate of the abutments used in single restorations was 19.7 % . Multiunit-fixed dental prostheses without and with pontics had complication rates of 3.9 % and 3.8 % , respectively . The 5-year survival rate of the abutments was more than 95 % , regardless of the type of prosthesis . CONCLUSIONS Alumina-toughened zirconia abutments are likely to exhibit excellent long-term survival in clinical use for fixed restorations . Single tooth replacement with the abutment at the molar region may require special care and extra attention OBJECTIVES To test the survival rates , and the technical and biological complication rates of customized zirconia and titanium abutments 5 years after crown insertion . MATERIAL AND METHODS Twenty-two patients with 40 single implants in maxillary and m and ibular canine and posterior regions were included . The implant sites were r and omly assigned to zirconia abutments supporting all-ceramic crowns or titanium abutments supporting metal-ceramic crowns . Clinical examinations were performed at baseline , and at 6 , 12 , 36 and 60 months of follow-up . The abutments and reconstructions were examined for technical and /or biological complications . Probing pocket depth ( PPD ) , plaque control record ( PCR ) and Bleeding on Probing ( BOP ) were assessed at abutments ( test ) and analogous contralateral teeth ( control ) . Radiographs of the implants revealed the bone level ( BL ) on mesial ( mBL ) and distal sides ( dBL ) . Data were statistically analyzed with nonparametric mixed models provided by Brunner and Langer and STATA ( P < 0.05 ) . RESULTS Eighteen patients with 18 zirconia and 10 titanium abutments were available at a mean follow-up of 5.6 years ( range 4.5 - 6.3 years ) . No abutment fracture or loss of a reconstruction occurred . Hence , the survival rate was 100 % for both . Survival of implants supporting zirconia abutments was 88.9 % and 90 % for implants supporting titanium abutments . Chipping of the veneering ceramic occurred at three metal-ceramic crowns supported by titanium abutments . No significant differences were found at the zirconia and titanium abutments for PPD ( meanPPDZrO2 3.3 ± 0.6 mm , mPPDTi 3.6 ± 1.1 mm ) , PCR ( mPCRZrO2 0.1 ± 0.3 , mPCRTi 0.3 ± 0.2 ) and BOP ( mBOPZrO2 0.5 ± 0.3 , mBOPTi 0.6 ± 0.3 ) . Moreover , the BL was similar at implants supporting zirconia and titanium abutments ( mBLZrO2 1.8 ± 0.5 , dBLZrO2 2.0 ± 0.8 ; mBLTi 2.0 ± 0.8 , dBLTi 1.9 ± 0.8 ) . CONCLUSIONS There were no statistically or clinical ly relevant differences between the 5-year survival rates , and the technical and biological complication rates  of zirconia and titanium abutments in posterior regions The roughness of intraoral hard surfaces plays an important role in bacterial adhesion and colonization . Earlier studies have shown that rough surfaces accumulate up to 25 times more subgingival plaque than do smooth sites . In the present study , the influence of surface smoothing was studied . In six partially edentulous patients waiting for a fixed prosthesis supported by endosseous titanium implants , four titanium abutments with different surface roughness were r and omly placed . After 1 month of intraoral exposure , subgingival plaque sample s from each abutment were compared within each patient by means of differential phase-contrast microscopy . After 3 months , supragingival and subgingival plaque sample s were taken from all abutments for differential phase-contrast microscopy and culturing . Probing depth , recession , and bleeding upon probing were scored at the same visit . Differential phase-contrast microscopy showed that subgingivally , only the two roughest abutments harbored spirochetes after 1 month . After 3 months , subgingivally , the composition of the flora showed little variation on the different abutment types , although spirochetes were only noticed around the roughest abutments . Anaerobic culturing result ed in comparable amounts of colony-forming units for all abutment types , both supragingivally and subgingivally . Subgingivally , the microbiologic composition did not show major interabutment differences . Clinical ly , small differences in probing depth were observed . The roughest abutment showed some attachment gain ( 0.2 mm ) during 3 months , whereas all other abutments had an attachment loss ranging from 0.8 to greater than 1 mm . The results indicate that a reduction in surface roughness ( less than a roughness of 0.2 micron ) had no major effect on the microbiologic composition , supragingivally or subgingivally . These observations indicate the existence of a threshold roughness below which no further impact on the bacterial adhesion and /or colonization should be expected . However , clinical evaluation seems to indicate that a certain surface roughness is necessary for increased resistance to clinical probing Bacterial adhesion to intra-oral , hard surfaces is firmly influenced by the surface roughness to these structures . Previous studies showed a remarkable higher subgingival bacterial load on rough surfaces when compared to smooth sites . More recently , the additional effect of a further smoothening of intra-oral hard surfaces on clinical and microbiological parameters was examined in a short-term experiment . The results indicated that a reduction in surface roughness below R(a ) = 0.2 microns , the so-called " thresholds R(a ) " , had no further effect on the quantitative/qualitative microbiological adhesion or colonisation , neither supra- nor subgingivally . This study aims to examine the long-term effects of smoothening intra-oral hard transgingival surfaces . In 6 patients expecting an overdenture in the lower jaw , supported by endosseus titanium implants , 2 different abutments ( transmucosal part of the implant ) : a st and ard machined titanium ( R(a ) = 0.2 microns ) and one highly polished and made of a ceramic material ( R(a ) = 0.06 microns ) were r and omly installed . After 3 months of intra-oral exposure , supra- and subgingival plaque sample s from both abutments were compared with each other by means of differential phase-contrast microscopy ( DPCM ) . Clinical periodontal parameters ( probing depth , gingival recession , bleeding upon probing and Periotest-value ) were recorded around each abutment . After 12 months , the supra- and subgingival sample s were additionally cultured in aerobic , CO2-enriched and anaerobic conditions . The same clinical parameters as at the 3-month interval were recorded after 12 months . At 3 months , spirochetes and motile organisms were only detected subgingivally around the titanium abutments . After 12 months , however , both abutment-types harboured equal proportions of spirochetes and motile organisms , both supra- and subgingivally . The microbial culturing ( month 12 ) failed to detect large inter-abutment differences . The differences in number of colony- forming units ( aerobic and anaerobic ) were within one division of a logarithmic scale . The aerobic culture data showed a higher proportion of Gram-negative organisms in the subgingival flora of the rougher abutments . From the group of potentially " pathogenic " bacteria , only Prevotella intermedia and Fusobacterium nucleatum were detected for anaerobic culturing and again the inter-abutment differences were negligible . Clinical ly , the smoothest abutment showed a slightly higher increase in probing depth between months 3 and 12 , and more bleeding on probing . The present results confirm the findings of our previous short-term study , indicating that a further reduction of the surface roughness , below a certain " threshold R(a ) " ( 0.2 microns ) , has no major impact on the supra- and subgingival microbial composition Health care professionals are increasingly required to base clinical decisions on the best available evidence . Evidence based medicine ( EBM ) is a systematic approach to clinical problem solving which allows the integration of the best available research evidence with clinical expertise and patient values . This paper explains the concept of EBM and introduces the five step EBM model  : formulation of answerable clinical questions ; search ing for evidence ; critical appraisal ; applicability of evidence ; evaluation of performance .  Subsequent articles will focus on the principles and critical appraisal of r and omised controlled trials , systematic review s , and meta-analyses , and provide a practical demonstration of the five step EBM model using a real life clinical scenario OBJECTIVE To assess the frequency and amount of residual cement after attachment of  monolithic zirconia crowns  to st and ard and individualized ceramic abutments . MATERIAL AND METHODS Twenty patients ( mean age 58.9 years at inclusion in the study ; 30 % male ) were r and omized to receive either a st and ard or an individualized abutment on a bone-level implant . Monolithic zirconia single crowns were attached to abutments by use of permanent glass-ionomer cement . Crowns were fabricated with an occlusal hole to enable unscrewing of the abutment-crown complex . Immediately after cementation , superstructures were removed and both the peri-implant soft tissue and the abutment-crown complex were photographed in a st and ardized manner , to detect residual cement . Photographs were analyzed using Corel Photo Paint X7 , and residual cement-to-total abutment and residual cement-to-peri-implant soft tissue area ratios were calculated . RESULTS Residual cement was observed for 9 of 10 ( 90 % ) individualized abutments , compared with 4 of 10 ( 40 % ) st and ard abutments ( OR = 13.5 , P = 0.049 ) . Twenty-seven of 40 ( 68 % ) individualized abutment surfaces were affected , compared with 12 of 40 ( 30 % ) st and ard abutment surfaces . The probability of observing residual cement was approximately five times higher for the surfaces of individualized abutments than for those of st and ard abutments ( P = 0.005 ) . The mean amount of sulcus surface covered by cement was 1.17 % ( SD 2.85 ) for the individualized abutments and 3.78 % ( SD 7.40 ) for the st and ard abutments . The position of the margin significantly affected the amount of residual cement . CONCLUSION Both individualized and st and ard all-ceramic abutments result in small amounts of subgingival residual cement on abutment and sulcus surfaces . However , use of individualized abutments does not guarantee complete avoidance of undetected cement rests . Undetected residual cement might be avoided by use of all-ceramic abutments with visible abutment shoulders BACKGROUND It has been shown that different implant design s and different vertical implant positions have an influence on crestal bone levels . The aim of the present study was to evaluate radiographic crestal bone changes around experimental dental implants with non-matching implant-abutment diameters placed submucosally or transmucosally at three different levels relative to the alveolar crest . METHODS Sixty two-piece dental implants with non-matching implant-abutment diameters were placed in edentulous spaces bilaterally in five foxhounds . The implants were placed submucosally or transmucosally in the left or the right side of the m and ible . Within each side , six implants were r and omly placed at three distinct levels relative to the alveolar crest . After 12 weeks , 60 crowns were cemented . Radiographs were obtained from all implant sites following implant placement , after crown insertion , and monthly for 6 months after loading . RESULTS Radiographic analysis revealed very little bone loss and a slight increase in bone level for 
    Output:
    
The total number of complications was similar between the two connections , yet , at external connections , abutment or occlusal screw loosening was more predominant .
Ceramic abutments , both internally and externally connected , demonstrated a significantly higher incidence of abutment fractures compared with metal abutments .
For implant-supported SCs , both metal and ceramic abutments with internal and external connections exhibited high survival rates .
Moreover , implant-supported FDPs with metal abutments with internal and external connections for also showed high survival rates