***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 r and omized-controlled clinical trial was to compare the objective and subjective esthetic outcomes of two types of  screwed-retained single-implant crowns .  MATERIAL S AND METHODS participants were r and omly assigned to the test ( all-ceramic ) and control [ porcelain-fused-to-ceramic ( PFM ) ] groups and were seen under investigation at baseline ( B ) , crown insertion ( CI ) , 1-year follow-up ( 1Y ) , and 2-year follow-up ( 2Y ) . Objective parameters were assessed by an intra-oral digital photograph ( 1:1 ratio ) , a study cast , a st and ardized radiograph , periodontal/peri-implant measurements , and question naires were obtained for the subjective parameters . In addition , pink esthetic score ( PES ) and white esthetic score ( WES ) were calculated for both groups . For the subjective evaluation , a visual analogue scale ( VAS ) question naire was used to assess the level of patient satisfaction regarding the esthetic outcome . Then , nine expert clinicians visually inspected and assessed subjective evaluation at the professional level . Statistical analysis was used to compare between groups and investigational appointments . RESULTS twenty patients were included in the study , 10 allocated to the all-ceramic group and 10 to the PFM group . No statistically significant differences were observed for the objective measurements comparing the test and control groups . Minor chipping of the ceramic veneering material was observed in the two patients of control group . The mean difference for all groups comparing objective parameters revealed an increase of papilla height between time points . A slight recession ( 0.26 mm ) of the peri-implant mucosal margin at the implant site was observed between 1Y and 2Y . Mean values for PES and WES were 13.9 and 13.1 for the PFM group and for the all-ceramic group , respectively . These values were not statistically significant . Implant crown volume , outline , translucency , and characterization showed major discrepancies with the contra-lateral natural teeth . As for subjective parameters , VAS patients ' responses regarding their perceptions of the esthetic outcome showed no statistical differences between groups and clinicians ' accuracy scores were 50 % and 47 % for PFM and all-ceramic crowns , respectively . CONCLUSION PFM and all-ceramic single-implant restorations may be indistinguishable from each other regarding the objective /subjective assessment of esthetic integration . The material chosen for fabricating an implant crown per se does not ensure an optimal esthetic outcome if other esthetic parameters are not present STATEMENT OF PROBLEM Computer-aided design and computer-aided manufacturing ( CAD/CAM ) generated restorations are gaining popularity . However , limited clinical evidence is available for single-unit posterior CAD/CAM restorations fabricated with established and newer crown material s. PURPOSE The purpose of this clinical study was to assess the restoration quality of and gingival response to CAD/CAM fabricated posterior single-tooth restorations with different processing technologies . MATERIAL AND METHODS Twenty-two individuals in need of posterior complete coverage crowns were recruited under an institutional review board approved protocol . Teeth were r and omized to 1 of 3 groups : metal ceramic , lithium disilicate , and monolithic zirconia . An unprepared or minimally restored tooth on the contralateral side was chosen as a control tooth for gingival measurements with each participant . Teeth were prepared and scanned intraorally by 1 of 3 experienced practitioners . A total of 32 restorations  were digitally design ed and fabricated with either milling technology or rapid-prototype printing and casting with conventional porcelain application . Restorations were evaluated with modified United States Public Health Service criteria for contour , marginal adaptation , occlusion , and shade . Gingival crevicular fluid volume and bleeding on probing were recorded preoperatively , at 1-month and 6-month postcementation visits . Polyvinyl siloxane impressions were made of the buccal margin of cemented restorations and evaluated with microcomputed tomography to assess marginal adaptation ( horizontal discrepancy ) . The Mantel Haenszel row mean score was used to assess whether the crown systems differed with respect to the modified United States Public Health Service criteria . Linear mixed models were used to assess whether the average gingival volumes were affected by the explanatory variables ( crown system , tooth status [ treated vs control ] , or visit ) . A generalized estimating equation approach was used to assess whether bleeding on probing was affected by the explanatory variables . One-way ANOVA was used to assess marginal discrepancy values among the crown systems ( α=.05 for all tests ) . RESULTS Twelve metal ceramic  , 10 lithium disilicate  , and 10  zirconia restorations were fabricated for 22 participants .  Zirconia restorations were significantly different from the other 2 crown systems ( P<.001 ) with respect to occlusion . No occlusal adjustment was needed on 80 % of the zirconia restorations . The average gingival crevicular fluid volumes did not differ among crown systems , between treated and control groups , or over time . The average horizontal marginal discrepancy was significantly different between lithium disilicate and zirconia crowns ( P=.027 ) , with zirconia crowns having the least amount of horizontal marginal discrepancy . CONCLUSIONS Given the small sample size and limitations of this study , CAD/CAM-generated restorations for posterior teeth made from different material s had acceptable clinical results 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 Carbon/graphite fiber-reinforced poly ( methyl methacrylate ) ( CGFP ) has been suggested as an alternative framework material for implant-supported fixed prostheses . The aim of this study was to evaluate CGFP prostheses  clinical ly over time in patients treated with titanium implants of the Brånemark type and to study the h and ling of the material in the technical production . Twenty-five patients were fitted with 27 CGFP prostheses supported by 119 implants .  Three implants , all in the upper jaw , were lost after loading . After a mean functioning time of 44 months ( range 32 - 56 ) , 19 prostheses ( 70 % ) were still in situ . In all , 5 prostheses fractured , of which 3 were exchanged whereas 2 could be repaired . The fractures were discovered early after loading and located close to the end abutment cylinders . During the follow-up period , the bone loss around the implants was about the same as earlier reported values for fixed prostheses with cast frameworks . It is concluded that a CGFP framework can be used to form the biocompatible superstructure of implant-supported prostheses with high precision at a low material cost and with good aesthetic results . The mechanical properties are so far not satisfactory but the method has the potential to be further developed and st and ardized PURPOSE This is a 2-year report from an ongoing prospect i ve 5-year multicenter study . The aim of the study was to evaluate the short- and long-term clinical function of CerAdapt ceramic abutments supporting short-span fixed partial dentures ( FPD ) . MATERIAL S AND METHODS Initially , 105 Brånemark System implants were placed in a total of 32 patients at 3 different clinics . After initial healing 103 implants remained . For the support of 36 FPDs , 53 ceramic and 50 titanium abutments were connected , 19 on ceramic and 17 on titanium abutments . RESULTS All patients remained in the study after 2 years . There was a cumulative survival rate of 97.1 % for implants and a cumulative success rate of 97.2 % for FPDs ( 94.7 % for ceramic and 100 % for titanium abutment-supported FPDs ) . One of 53 ceramic but none of 50 titanium abutments failed , giving a cumulative success rate of 98.1 % and 100 % , respectively , for the abutments . Soft tissue around abutments and adjacent teeth appeared healthy . More crown margins were placed submucosally at titanium ( 31 % ) than at ceramic ( 14 % ) abutments , and the level of the periimplant mucosa was relatively stable in relation to the abutment/crown . No differences were seen between ceramic and titanium abutments regarding bleeding of the periimplant mucosa . There was a minimal marginal bone loss recorded after 1 year , which was slightly more at titanium ( 0.4 mm ) than at ceramic ( 0.2 mm ) abutments . All patients and dentists were satisfied with the achieved esthetic result and no FPD was remade because of compromised esthetics . CONCLUSION So far the ceramic abutments have worked very well and the 2-year results have been very encouraging for CerAdapt abutments supporting short-span FPDs . However , ceramic material s tend to undergo static fatigue , and it is therefore important to wait for the 5-year results before making any more definite statement about the long-term prognosis for CerAdapt abutments PURPOSE The aim of this study was to quantitatively measure tooth and ceramic wear over a 2-year period using a novel superimposition technique . Three ceramic systems -- experimental hot-pressed ceramic ( EC ) , Procera AllCeram ( PA ) , and metal-ceramic -- were used . MATERIAL S AND METHODS A total of 90 posterior crowns in 48 patients were r and omized into 3 groups , and impressions were made at baseline and at 6-month intervals for 2 years . Clinical images were taken after using a dye to highlight surface changes . The impressions were digitized and modeled as superimposable 3-dimensional colored surface images . The depth of wear at the occlusal contact areas was quantitatively measured at 6 , 12 , 18 , and 24 months . RESULTS The quantitative evaluation showed more wear in Procera AllCeram at the occlusal contact areas , whereas the experimental and metal-ceramic systems showed less wear . There was a significant difference in the amount of enamel worn between all types of restorations ( P < .05 ) . There was a statistically significant difference ( P < .05 ) in the mean depth of wear between all systems . CONCLUSIONS The metal-ceramic and experimental systems showed less change , indicating improved wear resistance compared with Procera AllCeram . In addition , enamel opposing metal-ceramic and experimental crowns showed less wear compared to enamel opposed by Procera AIICeram crowns PURPOSE The aim of this r and omized controlled clinical trial was to compare the outcomes of  zirconia crowns and fixed partial dentures ( FPDs ) supported by teeth or implants . MATERIAL S AND METHODS Patients were recruited based on inclusion /exclusion criteria , and 59 eligible subjects were assigned r and omly to treatment by one of four zirconia systems ( Cercon , ZirkonZahn , Lava , and Katana )  . One hundred seven single-tooth and 160 three- to six-unit FPDs were fabricated on teeth and implants and cemented using composite resin cement .  Californian 
    Output:
    
There is insufficient evidence to support or refute the effectiveness of metal-free material s for fixed prosthodontic treatment over metal-ceramic or other type of st and ard restorations .