***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: Bleeding on probing ( BOP ) is the most significant clinical parameter for the assessment of periodontal inflammation . The aim of this prospect i ve longitudinal trial was to study the association between allelic variants of the IL-1 gene complex and  gingival inflammation .  Three hundred and twenty-three r and omly selected periodontal maintenance patients ( 64.4 % females ) received a  periodontal examination that included probing depth measurements and BOP at each of 4 supportive periodontal therapy ( SPT ) appointments . A blood sample taken from each subject was analysed for the presence of specific allotypes of the IL-1 gene complex . Two polymorphisms located at + 4845 bp in the IL-1 alpha region and at + 3954 bp in the IL-1 beta region were evaluated by a polymerase chain reaction method ; 35.3 % of the examined subjects were positive for specific combinations of allotypes of the IL-1 gene complex previously associated with an increased risk for severe periodontitis . The population consisted of 90 current smokers and 94 former smokers . An analysis of the association between the IL-1 genotype and BOP in the whole population ( including smokers ) did not reach statistical significance because of the overriding effect of smoking . A subset analysis of the 139 never smokers indicated that genotype positive patients had a significantly elevated chance of presenting an increase in the BOP% over a 4-appointment recall period ( p = 0.03 ) after correcting for oral hygiene . In fact , patients who were genotype-negative had a 50 % smaller chance of showing increases in BOP% during SPT . A further analysis explored the relationship between the genotype and the level of BOP% at the most recent recall visit . A generalized linear model showed a statistically significant effect of the genotype status after correcting for plaque accumulation and prevalence of residual pockets ( > or = 5 mm ) . Genotype-negative subjects had significantly lower BOP% ( p = 0.0097 ) . It is concluded that the increased BOP prevalence and incidence observed in IL-1 genotype-positive subjects indicates that some individuals have a genetically determined hyper-inflammatory response that is expressed in the clinical response of the periodontal tissues BACKGROUND Factors influencing the outcome of regenerative therapy of Class II furcations are incompletely and poorly understood . The purpose of this 24-month prospect i ve study was to examine the relationship of patient- , site- , and treatment-related factors to the clinical closure of r and omly selected m and ibular Class II furcations . Results of therapy were evaluated at 1 and 2 years postoperatively . One-year outcome data are presented in this report . METHODS A total of 43 otherwise healthy individuals with chronic periodontitis ( 26 male , 17 female ) , 36 to 70 years of age , completed the 12-month evaluation of the study . Entry criteria included clinical and radiographic evidence of two or more m and ibular facial Class II furcation defects ( > or = 3 mm horizontal probing depth ) .  Surgical therapy was completed by four periodontists ( two each ) in either a university clinic or private practice . Each patient contributed two furcation defects that were treated by combination therapy using an exp and ed polytetrafluoroethylene ( ePTFE ) membrane and demineralized freeze-dried bone allograft ( DFDBA ) . Clinical measurements included a gingival index , plaque index , mobility , and , referencing an occlusal stent , probing depth ( PD ) , probing attachment level-vertical ( PAL-V ) , and probing attachment level-horizontal ( PAL-H ) . Multiple linear measurements were recorded for each site clinical ly and after surgical debridement to characterize defect morphology , root configuration , and barrier placement . Defect volume was computed mathematically . Postsurgical maintenance care was provided at 1 to 2 , 4 , 6 , and 8 weeks , and then biweekly until 3 months , with subsequent supportive periodontal maintenance visits at 3-month intervals . The clinical status of the furcation ( open or closed ) , measured by a non-treating periodontist at 1 and 2 years , was the primary outcome measure . The association of patient-related factors ( e.g. , smoking ) , site-related factors ( e.g. , root configuration and defect morphology ) , and treatment-related factors ( e.g. , membrane exposure ) to clinical status of furcations was assessed using r and om effects hierarchical logistic regression analysis , controlling for design and demographic variables . Non-parametric analysis was used for specific group comparisons . RESULTS Complete clinical closure was achieved in 74 % of all sites . Of the residual furcation defects , 68 % were reduced to Class I. No defects progressed to Class III . Significant improvements in mean PD and PAL-V were obtained following surgical therapy . Although the proportion of sites demonstrating complete furcation closure was comparable for smokers and non-smokers , the proportion of Class II residual defects was significantly higher among smokers than non-smokers ( 62.5 % versus 14.3 % , respectively ) . Increases in presurgical PAL-H were associated with monotonic decreases in the percentage of sites demonstrating complete clinical closure , with only 53 % of lesions > or = 5 mm responding with complete closure . Similarly , significant reductions in the frequency of clinical closure were associated with increases in the distance between the roof of furcation and crest of bone , roof of furcation and base of defect , depth of horizontal defect , and divergence of roots at the crest of bone . CONCLUSIONS The successful clinical closure of Class II furcations was achievable at 1 year following combination therapy with an ePTFE membrane and DFDBA . The highest frequency of clinical furcation closure was observed in early Class II defects . Furcations with vertical or horizontal bone loss of 5 mm or greater responded with the lowest frequency of complete clinical closure . Nevertheless , complete furcation closure was achievable in 50 % of molars with extensive bone loss . Also , 15 out of 22 ( 68 % ) of all residual defects were reduced to Class I and only seven ( 8 % ) failed to improve , demonstrating that successful clinical resolution of advanced defects remains an attainable goal This prospect i ve multicenter intra-individual r and omized controlled clinical trial was design ed to compare the efficacy of guided tissue regeneration ( GTR ) with bioresorbable barrier membranes versus access flap surgery , in intrabony defects . 2 similar defects were selected in each of 23 patients and r and omly assigned to 1 of the 2 treatments . Surgery consisted of an identical procedure except for the omission of the barrier membrane in the flap control sites . At 1-year , probing pocket depth reductions were 4.3+/-2.3 mm in GTR treated sites and 3.0+/-1.5 mm in the flap control sites ( p=0.02 , paired t-test ) . Clinical attachment level ( CAL ) gains were 3.0+/-1.7 mm in the GTR sites and 1.6+/-1.8 mm in the control sites ( p=0.009 , paired t-test ) . A subset analysis , performed according to the initial depth of the intrabony component of the defects ( INFRA ) , indicated that in shallow defects ( INFRA < or =3 mm ) treated with the access flap alone , CAL gains were 1+/-1.5 mm , while in deep ones ( INFRA > or = 4 mm ) they were consistently greater ( 1.9+/-1.9 mm ) . The % CAL gains , calculated as the % of the baseline intrabony component depth , however , were almost identical in the 2 sub population s ( 45.8+/-64.7 % in shallow and 43.8+/-37.6 % in deep defects ) . Similarly , in the GTR sites , linear CAL gains were greater in deep ( 3.7+/-1.7 mm ) than in shallow defects ( 2.2+/-1.3 mm ) , but no differences were observed in terms of % CAL gains ( 76.7+/-27.7 % and 75.8+/-45 % , respectively ) . The frequency distribution of CAL changes expressed as % s of the baseline INFRA indicates that most of the sites treated with GTR ( 73 % in shallow and 92 % in deep defects ) gained 50 % or more CAL . Furthermore , many defects ( 64 % of shallow and 33 % of deep defects ) reached 100 % of CAL gain . The present study demonstrated that : ( i ) GTR with bioresorbable barrier membranes result ed in a significant added benefit in comparison with access flap alone ; ( ii ) the linear amounts of CAL gains were greater in deep than in shallow defects ; ( iii ) CAL gains expressed as % s of the baseline depths of the intrabony component , were similar in shallow and deep defects ; ( iii ) the regenerative procedure tested in the present study result ed in CAL gains equal to the depth of the intrabony component of the defect in some , but not in most of the instances 
    Output:
    
Within the limits of the present review , no direct conclusion for the effect of a susceptible IL-1 genotype status to the clinical outcome after periodontal regeneration could be drawn .