***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: This study reports a prospect i ve clinical trial comparing a carbon fibre reinforced carbon ( CFRC ) endodontic post with a conventional prefabricated post .  Twenty-seven single rooted maxillary anterior teeth in 18 patients ( nine males and nine females ; age range 18 - 60 years ) were restored either with a CFRC post or a wrought precious alloy control . Cast type III gold alloy cores were used in conjunction with both post groups . The CRFC posts ( n = 16 ) were cemented with a composite luting agent and the conventional posts ( control ) were cemented with zinc phosphate . Four failures were recorded in the CFRC post group at 24 , 29 , 56 and 87 months , compared with one failure in the control group at 84 months . These results suggest that post-retained crowns utilizing a CFRC material and a composite resin luting agent do not perform as well as conventional wrought precious alloy posts AIMS AND METHODS The purpose of this retrospective , non-r and omised cohort study was to evaluate the success rate of 775 endodontically treated teeth depending on the restoration type . A total of 508 patients with 775 endodontically treated teeth were examined during at least 12 months . The radiographic controls , time span between root canal filling and definitive restoration , restoration material type , inserted post system type and the occurrence of possible endodontically as well as restorative post-operative complications were recorded . RESULTS 18.3 % of the 775 investigated teeth were incisors and canines , 33.5 % were premolars and 48.2 % molars . Pre-fabricated and casted metal post systems were used only in 15.6 % of the endodontically treated teeth ( 18.4 % incisors and canines , 44.8 % premolars , 36.8 % molars ) . 6.6 % of the teeth had endodontically related symptoms or severe complications , whereas in 13.2 % of the teeth restored with metal posts showed complications , such as root or crown fractures . The Cox-Regression analysis showed that teeth restored with a post system had a statistically significant higher failure rate ( p = 0.044 ) than those which had been restored without posts . CONCLUSIONS The results showed a high success rate for endodontically treated teeth when the final restoration was placed within a short period of time ( two weeks ) . A higher tooth loss was observed when metal post systems were employed suggesting that pre caution is recommended when these types of posts are inserted 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 Through a st and ardized procedure using clinical examination , interviews , and dental history , this 2-year study documents 100 cases of tooth fracture in 98 patients . For comparison , pertinent information was also recorded for more than 2,000 teeth in a r and omly selected sample population . Two chief types of fracture were found : incomplete crown-root fractures and root fractures associated with earlier endodontic therapy BACKGROUND A prospect i ve study was started in 1995 to evaluate the success of carbon fibre reinforced epoxy resin ( CFRR ) posts used to restore endodontically treated teeth . All the teeth in the study had lost more than 50 % of their coronal structure . METHODS Fifty-nine carbon fibre Composiposts cemented with Metabond and built up with Core Paste cores were placed into the teeth of 47 patients . Each tooth received a full-coverage restoration ( porcelain fused to metal crown ) and was followed for 6.7 - 45.4 months ( average = 28.0 months , st and ard deviation = 10.7 ) . RESULTS Results for 52 teeth in 42 patients were analyzed . There were no fractures . The overall failure rate was 7.7 % and the cumulative survival rate was 89.6 % at the end of the follow-up period . The only statistically significant finding ( p = 0.04 ) was that posts in lower premolars were at higher risk of failure . CONCLUSION CFRR posts are among the most predictable systems available today . CFRR posts in the upper anterior teeth are associated with a higher success rate and longer life than those placed in premolars , especially lower premolars . This study contributes to the growing body of evidence that supports the use of CFRR posts in the restoration of endodontically treated teeth PURPOSE This study prospect ively evaluated the clinical performance of three types of translucent posts over a follow-up period of between 2 and 3 years . MATERIAL S AND METHODS Selected were 225 patients with one premolar in need of endodontic treatment , followed by restoration with a fiber post and porcelain crown .  The sample was r and omly divided into three groups of 75 patients each . The same type of post was used in all patients within a group : group 1 = Aesthetic Plus ; group 2 = DT ; and group 3 = FRC Postec . For bonding the post , a light-curing adhesive ( One-Step ) and a dual-curing resin cement ( Duo-Link ) were applied in group 1 and 2 roots , whereas self-curing material s ( Excite DSC as adhesive and MultiLink as resin cement ) were used in group 3 . After 6 , 12 , and 24 months , patients were recalled , and a clinical and radiographic examination was performed . For some patients , 30-month follow-up data were also collected . RESULTS Debonding of the post occurrred in eight cases ( 3.5 % ) ; in another six cases , a recurrence of the periapical lesion was reported . CONCLUSION The statistical analysis did not reveal any significant difference in the survival rate of the tested posts , suggesting that all are equally and sufficiently reliable for clinical use PURPOSE In the present prospect i ve study , four different post- and -core systems were evaluated over a period of up to 10 years . MATERIAL S AND METHODS Fifty endodontically treated teeth in 31 patients were r and omized to one of four groups for post- and -core placement : Group 1 received conventional tapered cast posts and cores ( n = 14 ) ; group 2 received ParaPost system prefabricated gold posts with cast cores ( n = 13 ) ; group 3 received ParaPost system cast posts and cores ( n = 13 ) ; and group 4 received Radix-Anchor posts ( n = 10 ) . Clinical and radiologic evaluations were made . RESULTS One post and core in group 2 was functioning well 58 months after placement when the patient died . No posts and cores in groups 1 or 2 had been lost or had any complications , one in group 3 had been lost because of a root fracture after 108 months , and two in group 4 had been lost after 54 and 88 months , respectively , because of loss of retention . The final treatment result for 46 of the 49 remaining posts ( 30 patients ) was successful . The overall failure rate was 6 % . There were no statistically significant differences between the four groups . CONCLUSION If recommended procedures are strictly followed , posts and cores can serve as abutments for fixed single crowns with satisfactory long-term results OBJECTIVES The aim of this study is to provide prospect i ve clinical data for the survival of postendodontic reconstructions of teeth with varying degrees of hard tissue loss using tapered or parallel-sided post shapes . METHODS Eighty-three patients got 105 glass fibre reinforced posts of tapered ( Luscent Anchors , Dentatus , Sweden ) and parallel-sided , serrated ( FibreKor , Jeneric Pentron , USA ) post shape . A dual curing hybrid composite Compolute ( 3 M ESPE , Germany ) was used as luting material , EBS-Multi ( 3 M ESPE ) as adhesive system and Clearfil Core ( Kuraray , Japan ) for core built-up . The restorations were followed for a minimum of 24 months . The statistical analysis was performed on a r and om sub- sample of one restoration per subject . The Fisher exact test was used to compare frequencies of failures after 12 and 24 month . A Kaplan-Meier- analysis was used to analyse time-to-failure in both groups . Differences of survival time between post types were tested with the log-rank test . RESULTS 3.8 % of the restorations failed after 12 month , 12.8 % after 24 month , respectively . The main failure type observed was post fractures . All but one failed teeth could be restored . There was no difference in failure frequency between post types after 12 or 24 months . The log-rank test showed no differences in survival between the two types of post ( p=0.37 ) . CONCLUSION Parallel-sided and tapered glass fibre posts result after 2 years of clinical service in an equal rate of survival PURPOSE This prospect i ve clinical follow-up evaluated the acceptability of quartz fiber-reinforced epoxy posts used in endodontically treated teeth over a 30-month period . MATERIAL S AND METHODS In 132 patients , 180 endodontically treated teeth were restored using AEstheti-Plus quartz-fiber posts . The posts were luted with the All-Bond 2 adhesive system and C&B Resin Cement according to the manufacturer 's recommendations . The core was made with Core-Flo or Bis-Core , and all-ceramic crowns or metal-ceramic crowns were applied as final restorations . The parameters considered as clinical failure were displacement , detachment , or fracture of posts ; core or root fracture ; and crown or prosthesis decementation . Patients were reevaluated at 6 , 12 , 24 , and 30 months . RESULTS One cohesive failure involving a margin of the composite core was observed after 2 weeks , and two adhesive fractures were seen after 2 months . These failures were located between the cement and the dentin walls of the canals . All three failures occurred during removal of the temporary crown . The percentage of failures was thus 1.7 % over a 30-month period , but it was possible to successfully replace the restoration in all three failed cases . CONCLUSION Over a 30-month period , the rehabilitation of endodontically treated teeth using quartz-fiber posts showed good clinical results . No crown or prosthesis decementation was observed , and no post , core , or root fractures were recorded Prospect i ve clinical studies comparing the results of different types of restorations of endodontically treated teeth are lacking . This study compared the clinical success rate of endodontically treated premolars restored with fiber posts and direct composite to the  restorations of premolars using amalgam . Premolars with Class II carious lesions were selected and r and omly assigned to one of two experimental groups : ( 1 ) restoration with amalgam or ( 2 ) restoration with fiber posts and composite .  One hundred and nine teeth were included in Group 1 and 110 in Group 2 . Patients were recalled after 1 , 3 and 5 years . No statistically significant difference was found between the proportion of failed teeth in the two experimental groups . Significant differences were observed between the proportion of root fractures ( p=0.029 ) and caries ( p=0.047 ) , with more root fractures and less caries observed in the teeth restored with amalgam at the five-year recall . Within the limits of this study , it can be concluded that restorations with fiber posts and composite were found to be more effective than amalgam in preventing root fractures but less effective in preventing secondary caries 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 
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Thus fewer failures occurred when using non-metal posts but the evidence is unreliable .
Our systematic review could not specify which type of post and core system should be used when two or three dentine walls remain .