human
***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 purpose of this study was to assess the fracture resistance of roots that were prosthetically restored with intra-radicular posts  of different lengths . Forty-five bovine incisors were sectioned 17 mm from their apices , endodontically treated and r and omly divided into three experimental groups : GI , fibreglass posts luted at a depth of 12 mm ; GII , 8 mm and GIII , 4 mm . All posts were luted with dual resin cement . Resin composite cores were prepared with st and ardized measurements , and all teeth were restored with metal crowns . The sample s were su bmi tted to the fracture resistance test in a universal testing machine , at an angle of 135 degrees and speed of 0.5 mm min(-1 ) , until fracture occurred . The data , in MPa , were su bmi tted to the analysis of variance ( anova ) followed by Tukey 's test ( alpha = 0.01 ) . No statistically significant difference ( P > 0.01 ) was found between GI ( 129.72 + /- 12.14 ) and GII ( 154.3 + /- 12.08 ) , which presented the highest fracture resistance values . Group GIII ( 100.5 + /- 8.07 ) showed lower fracture resistance ( P < 0.01 ) when compared with GI and GII . Within the limitations of this study , it was concluded that the post lengths influenced the fracture resistance of prosthetically restored roots . These results suggest that it is not necessary to perform excessive intra-radicular post-space preparation to improve the fracture resistance of roots STATEMENT OF PROBLEM Crowns have been considered the restoration of choice for endodontically treated teeth , but their selection has been based primarily on anecdotal evidence . PURPOSE This study tested the hypothesis that crown placement ( coronal coverage ) is associated with improved survival of endodontically treated teeth when preaccess , endodontic , and restorative factors are controlled . MATERIAL AND METHODS A University of Iowa College of Dentistry treatment data base was used to identify permanent teeth that had undergone initial obturation between July 1 , 1985 , and December 31 , 1987 . Study patients were restricted to persons with at least 1 dental visit in each 2-year interval from 1985 to 1996 ; a simple r and om sample of 280 patients ( n = 400 teeth ) was selected . Dental charts , radiographs , and computerized data bases were examined to ascertain variables of interest and to verify study inclusion criteria . Kaplan-Meier survival estimates were generated for the 203 teeth that satisfied study inclusion criteria . Multivariate Cox proportional hazards regression models were developed , with st and ard errors adjusted to account for clustering of teeth within patients . RESULTS When tooth type and radiographic evidence of caries at access were controlled , the final Cox model showed that endodontically treated teeth not crowned after obturation were lost at a 6.0 times greater rate than teeth crowned after obturation ( 95 % confidence interval : 3.2 to 11.3 ) . CONCLUSION Within the limitations of this study , a strong association between crown placement and the survival of endodontically treated teeth was observed . These results may impact treatment planning if long-term tooth retention is the primary goal PURPOSE To determine , in a 3-year clinical trial , whether tooth type and ferrule significantly affect the survival of pulpless teeth restored with fiber posts . METHODS A sample of 87 teeth in 87 patients ( 32 men and 55 women , age ranged from 23 to 78 ) were restored using Snowpost : 34 incisors , 12 canines , 25 premolars and 16 molars . The posts were cemented with RelyXUnicem and the core was made with a resin composite ( Dentocore Automix ) . Every tooth was covered with a metal-ceramic or all ceramic crown . Two experimental groups , according to the presence or absence of ferrule , were defined : A ) 45 teeth with ferrule ( > 2 mm height ) ; and B ) 42 teeth without ferrule ( < 2 mm height ) . Patients were reevaluated every 6 months . RESULTS 14 of the total restorations failed ( 16.1 % ) . The failure modes were caries ( n=4 ) , post fracture ( n=4 ) , root fracture ( n=2 ) , and marginal gap , post cement failure , crown cement failure , and periapical lesion ( n= 1 respectively ) . In Group A the failure observed was 6.67 % and in Group B it was 26.20 % . The log-rank test showed statistically significant differences between both groups . According to the type of tooth , the incisors were the teeth with the highest failure rate ( 73.52 % ) , but Chi-square test showed no statistically significant differences among the four tooth types , perhaps because of the low number of the sample OBJECTIVE To assess the survival rate of two different post systems after 5 years of service with a prospect i ve r and omized controlled trial . METHOD AND MATERIAL S One hundred patients in need of a post were studied . Half of the patients received long glass fiber-reinforced posts , while the other half received long metal screw posts . The posts were assigned r and omly . After at least 5 years ( mean , 61.37 months ) , follow-ups were established . When a complication occurred prior to this recall , the type and time of the complication was documented . Statistical analysis was performed using the log-rank test and Kaplan-Meier analysis . Additionally , a Cox regression was performed to analyze risk factors . RESULTS The survival rate of fiber-reinforced posts was 71.8 % . In the metal screw post group , the survival rate was significantly lower , 50.0 % ( log-rank test , P = .026 ) . Metal posts result ed more often in more unfavorable complications ( eg , root fractures ) ; consequently , more teeth ( n = 17 ) had to be extracted . The Cox regression identified the following risk factors : position of the tooth ( anterior vs posterior teeth ) , degree of coronal tooth destruction , and the post system  ( fiber-reinforced post vs metal screw post )  . Fiber-reinforced restorations loosened in several patients ; in some of these cases ( n = 6 ) , patients did not notice this , leading to the extraction of teeth . CONCLUSION Long metal screw posts should be used with great care in endodontically treated teeth . Besides the selection of the post system , other factors influence the survival of the restoration STATEMENT OF PROBLEM Little information exists regarding the outcome of crown build-ups on endodontically treated teeth restored with metal-ceramic crowns or with only a direct-placed composite . PURPOSE The aim of this study was to evaluate the clinical success rate of endodontically treated premolars restored with fiber posts and direct composite restorations and compare that treatment with a similar treatment of full-coverage with metal-ceramic crowns . MATERIAL AND METHODS Subjects included in this study had one maxillary or m and ibular premolar for which endodontic treatment and crown build up was indicated and met specific inclusion /exclusion criteria . Only premolars with Class II carious lesions and preserved cusp structure were included . Subjects were r and omly assigned to 1 of the following 2 experimental groups : ( 1 ) teeth endodontically treated and restored with adhesive techniques and composite or ( 2 ) teeth endodontically treated , restored with adhesive techniques and composite , and then restored with full-coverage metal-ceramic crowns .  Sixty teeth were included in the first group and 57 in the second . All restorations were performed by one operator . Causes of failure were categorized as root fracture , post fracture , post decementation , clinical and /or radiographic evidence of marginal gap between tooth and restoration , and clinical and /or radiographic evidence of secondary caries contiguous with restoration margins . Subjects were examined for the listed clinical and radiographic causes of failure by 2 calibrated examiners at intervals of 1 , 2 , and 3 years . Exact 95 % confidence intervals for the difference between the 2 experimental groups were calculated . RESULTS At the 1-year recall , no failures were reported . The only failure modes observed at 2 and 3 years were decementations of posts and clinical and /or radiographic evidence of marginal gap between tooth and restoration . There was no difference in the failure frequencies of the 2 groups ( 95 % confidence interval , -17.5 to 12.6 ) . There was no difference between the number of failures caused by post decementations and the presence of marginal gaps observed in the 2 groups ( 95 % confidence intervals , -9.7 to 16.2 and -17.8 to 9.27 ) . CONCLUSION Within the limitations of this study , the results upheld the research hypothesis that the clinical success rates of endodontically treated premolars restored with fiber posts and direct composite restorations after 3 years of service were equivalent to a similar treatment of full coverage with metal-ceramic crowns INTRODUCTION This is the first clinical long-term pilot study that tested the biomimetic concept of using more flexible , dentine-like ( low Young modulus ) glass fiber-reinforced epoxy resin posts ( GFREPs ) compared with rather rigid , stiff ( higher Young modulus ) titanium posts ( TPs ) in order to improve the survival rate of severely damaged endodontically treated teeth . METHODS Ninety-one subjects in need of postendodontic restorations in teeth with 2 or less remaining cavity walls were r and omly assigned to receive either a tapered TP ( n = 46 ) or a tapered GFREP ( n = 45 ) . The posts were adhesively luted using self-adhesive resin cement . The composite core build-ups were prepared ensuring a circumferential 2-mm ferrule . The primary endpoint was a loss of restoration for any reason . To study group differences , the log-rank test was calculated ( P < .05 ) . Hazard plots were constructed . RESULTS After 84 months of observation ( mean = 71.2 months ) , 7 restorations failed ( ie , 4 GFREPs and 3 TPs ) . The failure modes were as follows : GFREP : root fracture ( n = 3 ) , core fracture ( n = 1 ) and TP : endodontic failure ( n = 3 ) . No statistical difference was found between the survival rates ( GFREPs = 90.2 % , TPs = 93.5 % , P = .642 ) . The probability of no failure was comparable for both post material s ( risk ratio ; 95 % confidence interval , 0.965 - 0.851/1.095 ) . CONCLUSIONS When using self-adhesive luted prefabricated posts in severely destroyed abutment teeth with 2 or less cavity walls and a 2-mm ferrule , postendodontic restorations achieved high long-term survival rates irrespective of the post material used ( ie , glass fiber vs titanium ) 
    Output:
    
agent
Conclusions The most frequently reported failures in the available studies were as follows : fiber post debonding , loss of retention of single crowns , and marginal gaps .
Less frequently , chippings and fractures were recorded in SCs .
***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 purpose of this study was to assess the fracture resistance of roots that were prosthetically restored with intra-radicular posts  of different lengths . Forty-five bovine incisors were sectioned 17 mm from their apices , endodontically treated and r and omly divided into three experimental groups : GI , fibreglass posts luted at a depth of 12 mm ; GII , 8 mm and GIII , 4 mm . All posts were luted with dual resin cement . Resin composite cores were prepared with st and ardized measurements , and all teeth were restored with metal crowns . The sample s were su bmi tted to the fracture resistance test in a universal testing machine , at an angle of 135 degrees and speed of 0.5 mm min(-1 ) , until fracture occurred . The data , in MPa , were su bmi tted to the analysis of variance ( anova ) followed by Tukey 's test ( alpha = 0.01 ) . No statistically significant difference ( P > 0.01 ) was found between GI ( 129.72 + /- 12.14 ) and GII ( 154.3 + /- 12.08 ) , which presented the highest fracture resistance values . Group GIII ( 100.5 + /- 8.07 ) showed lower fracture resistance ( P < 0.01 ) when compared with GI and GII . Within the limitations of this study , it was concluded that the post lengths influenced the fracture resistance of prosthetically restored roots . These results suggest that it is not necessary to perform excessive intra-radicular post-space preparation to improve the fracture resistance of roots STATEMENT OF PROBLEM Crowns have been considered the restoration of choice for endodontically treated teeth , but their selection has been based primarily on anecdotal evidence . PURPOSE This study tested the hypothesis that crown placement ( coronal coverage ) is associated with improved survival of endodontically treated teeth when preaccess , endodontic , and restorative factors are controlled . MATERIAL AND METHODS A University of Iowa College of Dentistry treatment data base was used to identify permanent teeth that had undergone initial obturation between July 1 , 1985 , and December 31 , 1987 . Study patients were restricted to persons with at least 1 dental visit in each 2-year interval from 1985 to 1996 ; a simple r and om sample of 280 patients ( n = 400 teeth ) was selected . Dental charts , radiographs , and computerized data bases were examined to ascertain variables of interest and to verify study inclusion criteria . Kaplan-Meier survival estimates were generated for the 203 teeth that satisfied study inclusion criteria . Multivariate Cox proportional hazards regression models were developed , with st and ard errors adjusted to account for clustering of teeth within patients . RESULTS When tooth type and radiographic evidence of caries at access were controlled , the final Cox model showed that endodontically treated teeth not crowned after obturation were lost at a 6.0 times greater rate than teeth crowned after obturation ( 95 % confidence interval : 3.2 to 11.3 ) . CONCLUSION Within the limitations of this study , a strong association between crown placement and the survival of endodontically treated teeth was observed . These results may impact treatment planning if long-term tooth retention is the primary goal PURPOSE To determine , in a 3-year clinical trial , whether tooth type and ferrule significantly affect the survival of pulpless teeth restored with fiber posts . METHODS A sample of 87 teeth in 87 patients ( 32 men and 55 women , age ranged from 23 to 78 ) were restored using Snowpost : 34 incisors , 12 canines , 25 premolars and 16 molars . The posts were cemented with RelyXUnicem and the core was made with a resin composite ( Dentocore Automix ) . Every tooth was covered with a metal-ceramic or all ceramic crown . Two experimental groups , according to the presence or absence of ferrule , were defined : A ) 45 teeth with ferrule ( > 2 mm height ) ; and B ) 42 teeth without ferrule ( < 2 mm height ) . Patients were reevaluated every 6 months . RESULTS 14 of the total restorations failed ( 16.1 % ) . The failure modes were caries ( n=4 ) , post fracture ( n=4 ) , root fracture ( n=2 ) , and marginal gap , post cement failure , crown cement failure , and periapical lesion ( n= 1 respectively ) . In Group A the failure observed was 6.67 % and in Group B it was 26.20 % . The log-rank test showed statistically significant differences between both groups . According to the type of tooth , the incisors were the teeth with the highest failure rate ( 73.52 % ) , but Chi-square test showed no statistically significant differences among the four tooth types , perhaps because of the low number of the sample OBJECTIVE To assess the survival rate of two different post systems after 5 years of service with a prospect i ve r and omized controlled trial . METHOD AND MATERIAL S One hundred patients in need of a post were studied . Half of the patients received long glass fiber-reinforced posts , while the other half received long metal screw posts . The posts were assigned r and omly . After at least 5 years ( mean , 61.37 months ) , follow-ups were established . When a complication occurred prior to this recall , the type and time of the complication was documented . Statistical analysis was performed using the log-rank test and Kaplan-Meier analysis . Additionally , a Cox regression was performed to analyze risk factors . RESULTS The survival rate of fiber-reinforced posts was 71.8 % . In the metal screw post group , the survival rate was significantly lower , 50.0 % ( log-rank test , P = .026 ) . Metal posts result ed more often in more unfavorable complications ( eg , root fractures ) ; consequently , more teeth ( n = 17 ) had to be extracted . The Cox regression identified the following risk factors : position of the tooth ( anterior vs posterior teeth ) , degree of coronal tooth destruction , and the post system  ( fiber-reinforced post vs metal screw post )  . Fiber-reinforced restorations loosened in several patients ; in some of these cases ( n = 6 ) , patients did not notice this , leading to the extraction of teeth . CONCLUSION Long metal screw posts should be used with great care in endodontically treated teeth . Besides the selection of the post system , other factors influence the survival of the restoration STATEMENT OF PROBLEM Little information exists regarding the outcome of crown build-ups on endodontically treated teeth restored with metal-ceramic crowns or with only a direct-placed composite . PURPOSE The aim of this study was to evaluate the clinical success rate of endodontically treated premolars restored with fiber posts and direct composite restorations and compare that treatment with a similar treatment of full-coverage with metal-ceramic crowns . MATERIAL AND METHODS Subjects included in this study had one maxillary or m and ibular premolar for which endodontic treatment and crown build up was indicated and met specific inclusion /exclusion criteria . Only premolars with Class II carious lesions and preserved cusp structure were included . Subjects were r and omly assigned to 1 of the following 2 experimental groups : ( 1 ) teeth endodontically treated and restored with adhesive techniques and composite or ( 2 ) teeth endodontically treated , restored with adhesive techniques and composite , and then restored with full-coverage metal-ceramic crowns .  Sixty teeth were included in the first group and 57 in the second . All restorations were performed by one operator . Causes of failure were categorized as root fracture , post fracture , post decementation , clinical and /or radiographic evidence of marginal gap between tooth and restoration , and clinical and /or radiographic evidence of secondary caries contiguous with restoration margins . Subjects were examined for the listed clinical and radiographic causes of failure by 2 calibrated examiners at intervals of 1 , 2 , and 3 years . Exact 95 % confidence intervals for the difference between the 2 experimental groups were calculated . RESULTS At the 1-year recall , no failures were reported . The only failure modes observed at 2 and 3 years were decementations of posts and clinical and /or radiographic evidence of marginal gap between tooth and restoration . There was no difference in the failure frequencies of the 2 groups ( 95 % confidence interval , -17.5 to 12.6 ) . There was no difference between the number of failures caused by post decementations and the presence of marginal gaps observed in the 2 groups ( 95 % confidence intervals , -9.7 to 16.2 and -17.8 to 9.27 ) . CONCLUSION Within the limitations of this study , the results upheld the research hypothesis that the clinical success rates of endodontically treated premolars restored with fiber posts and direct composite restorations after 3 years of service were equivalent to a similar treatment of full coverage with metal-ceramic crowns INTRODUCTION This is the first clinical long-term pilot study that tested the biomimetic concept of using more flexible , dentine-like ( low Young modulus ) glass fiber-reinforced epoxy resin posts ( GFREPs ) compared with rather rigid , stiff ( higher Young modulus ) titanium posts ( TPs ) in order to improve the survival rate of severely damaged endodontically treated teeth . METHODS Ninety-one subjects in need of postendodontic restorations in teeth with 2 or less remaining cavity walls were r and omly assigned to receive either a tapered TP ( n = 46 ) or a tapered GFREP ( n = 45 ) . The posts were adhesively luted using self-adhesive resin cement . The composite core build-ups were prepared ensuring a circumferential 2-mm ferrule . The primary endpoint was a loss of restoration for any reason . To study group differences , the log-rank test was calculated ( P < .05 ) . Hazard plots were constructed . RESULTS After 84 months of observation ( mean = 71.2 months ) , 7 restorations failed ( ie , 4 GFREPs and 3 TPs ) . The failure modes were as follows : GFREP : root fracture ( n = 3 ) , core fracture ( n = 1 ) and TP : endodontic failure ( n = 3 ) . No statistical difference was found between the survival rates ( GFREPs = 90.2 % , TPs = 93.5 % , P = .642 ) . The probability of no failure was comparable for both post material s ( risk ratio ; 95 % confidence interval , 0.965 - 0.851/1.095 ) . CONCLUSIONS When using self-adhesive luted prefabricated posts in severely destroyed abutment teeth with 2 or less cavity walls and a 2-mm ferrule , postendodontic restorations achieved high long-term survival rates irrespective of the post material used ( ie , glass fiber vs titanium ) 
    Output:
    