***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: To investigate the relationship of smoking with the rate of pseudarthrosis ( surgical nonunion ) , 50 patients , who were smokers , and 50 patients , who were not , and who had had a two-level laminectomy and fusion during 1977 and 1978 were r and omly selected for this study . Most of those participating had sustained job-related injuries whereas the others had no common etiology for their back dysfunction . Most of the patients were from the southeastern United States . Ages ranged from 23 to 62 years , with a mean age of 42.4 years for smokers and 42.7 years for nonsmokers . There was an equal representation of males and females , with minorities represented according to their general percentage in the population . Examination 1 to 2 years after surgery revealed that 40 % ( 20 ) of the smokers had developed a pseudarthrosis , whereas among nonsmokers , the rate was 8 % ( 4 ) . This finding appears to be independent of age , sex , or race and was statistically significant ( χ2=14.035 , p=.001 ) . It was hypothesized that the higher incidence of surgical nonunion among smokers may be related to blood gas levels . Nonsmokers showed no significant deficiencies , whereas smokers showed a mean PO2 level of 78.5 % ( normal=95 - 97 ) and a mean O2 saturation level of 92.9 % ( normal=95 or above ) . Implication s and suggestions for further research are also discussed The aim of this controlled , clinical study was to evaluate guided tissue regeneration using a bioabsorbable membrane in periodontal intraosseous defects . Forty patients , each contributing one defect > or = 4 mm in depth participated . The control group ( 18 individuals ) received conventional flap therapy , while the test group ( 22 individuals ) was treated using the bioabsorbable membrane , Guidor . Clinical assessment s were made by one examiner , blinded with respect to treatment group , at baseline , 6 and 12 months following surgery . Baseline probing pocket depths of 7.7+/-1.4 mm in the membrane group and 7.6+/-1.9 mm in the control group were measured . Twelve month results showed a significant clinical attachment level gain in both control ( 1.1+/-1.8 mm ) , and membrane group ( 1.3+/-2.1 mm ) . Probing pocket depth reduction of 2.6+/-1.9 mm and 2.7+/-1.9 mm was observed in the respective groups . Bone sounding showed a non-significant gain of 0.4+/-1.8 mm and 0.6+/-1.4 mm at membrane and control sites , respectively . Radiographic evaluation confirmed these results . There were no significant differences found between treatment groups for any of the tested variables . Smoking had a negative effect on healing in both groups . In conclusion , clinical and radiographic results indicate that guided tissue regeneration using a bioabsorbable membrane at intraosseous defects did not predictably achieve greater clinical attachment level gain nor bone gain when compared to conventional flap therapy We retrospectively review ed a prospect ively followed cohort of 105 patients with 110 open tibia fractures treated with external fixator or intramedullary nail  to determine whether smoking affects fracture healing . Severe open tibia-shaft fractures treated at a tertiary-care medical center were included . Patients with type II , IIIA , or IIIB tibia fractures were eligible . Treatment for all patients was similar , except that they were r and omized to receive external fixator or intramedullary nail .  Time to fracture healing was the main outcome measurement . Smokers had a union rate of 84 % ( 52/62 ) , and nonsmokers had a union rate of 94 % ( 45/48 ) , P = .10 . For smokers in one arm of the study , time to union was significantly longer ( P = .01 ) , and there were more complications ( P = .04 ) . Smoking decreased unions , slowed healing , and increased complications Objectives : Current data show smoking is associated with a number of complications of the fracture healing process . A concern , however , is the potential confounding effect of covariates associated with smoking . The present study is the first to prospect ively examine time to union , as well as major complications of the fracture healing process , while adjusting for potential confounders . Setting : Eight Level I trauma centers . Patients : Patients with unilateral open tibia fractures were divided into 3 baseline smoking categories : never smoked ( n = 81 ) ,  previous smoker ( n = 82 ) , and  current smoker ( n = 105 ) . Outcome Measure : Time to fracture healing , diagnosis of infection , and osteomyelitis . Methods : Survival and logistic analyses were used to study differences in time to fracture healing and the likelihood of developing complications , respectively . Multivariate models were used to adjust for injury severity , treatment variations , and patient characteristics Results : After adjusting for covariates , current and previous smokers were 37 % ( P = 0.01 ) and 32 % ( P = 0.04 ) less likely to achieve union than nonsmokers , respectively . Current smokers were more than twice as likely to develop an infection ( P = 0.05 ) and 3.7 times as likely to develop osteomyelitis ( P = 0.01 ) . Previous smokers were 2.8 times as likely to develop osteomyelitis ( P = 0.07 ) , but were at no greater risk for other types of infection . Conclusion : Smoking places the patient at risk for increased time to union and complications . Previous smoking history also appears to increase the risk of osteomyelitis and increased time to union . The results highlight the need for orthopaedic surgeons to encourage their patients to enter a smoking cessation programs The aim of the present clinical trial was to evaluate the effect of different modes of periodontal therapy on patients with moderately advanced periodontal disease and to express the findings in terms of probing pocket depth and attachment level alterations at periodontal sites with different initial probing depths . The material consisted of 16 patients , 35 - 65 years of age . Following a Baseline examination including assessment s of oral hygiene status , gingival conditions , probing pocket depths and probing attachment levels , the patients were subjected to periodontal treatment . A " split-mouth " design approach of therapy was used and the jaw quadrants were r and omly selected for the following different treatment procedures : ( 1 ) scaling and root planning , ( 2 ) scaling and root planing in conjunction with a gingivectomy procedure , ( 3 ) scaling and root planing in conjunction with an apically repositioned flap procedure without bone recontouring , ( 4 ) scaling and root planing in conjunction with an apically repositioned flap procedure including bone recontouring , ( 5 ) scaling and root planing in conjunction with a modified Widman flap procedure without bone recontouring and ( 6 ) scaling and root planing in conjunction with a modified Widman flap procedure including bone recontouring . The patients were following active treatment enrolled in a supervised maintenance care program including " professional tooth cleaning " once every 2 weeks during a 6-month period of healing , after which a final examination was performed . The investigation demonstrated that active therapy including meticulous subgingival debridement result ed in a low frequency of gingival sites which bled on probing , a high frequency of sites with shallow pockets ( less than 4 mm ) and the disappearance of pockets with a probing depth of greater than 6 mm . Between the Baseline examination and the 6-month re-examination , the probing attachment level for initially shallow pockets remained basically unaltered , but with a tendency of a minor apical shift . This occurred in all 6 treatment groups . For sites with initial probing depths of 4 - 6 mm and greater than 6 mm , there was in all groups some gain of probing attachment . This gain was most pronounced in the initially deeper ( greater than 6 mm ) pockets . With the use of regression analysis , the " critical probing depth " ( CPD ) value ( i.e. the initial probing depth value below which loss of attachment occurred as a result of treatment and above which gain of probing attachment level result ed ) was calculated for each of the 6 methods of treatment used . A comparison of the CPD-values between the 6 treatment groups did not reveal any major differences OBJECTIVES Current literature is ambivalent on the use of barrier membranes for regeneration of intraosseous defects . One of the reasons for unpredictable results may be related to infection before , during and after the surgical procedure . Therefore , the purpose of the present controlled study was to evaluate both the use of membranes ( MEM ) and antibiotics ( AB ) , separately and in combination . METHODS In all , 25 patients with two intraosseous periodontal defects each were r and omized in two groups : AB+ group receiving systemic antibiotics ( n = 13 ) and AB- group without antibiotics ( n = 12 ) . After raising flaps and after debridement , both defects in each patient were covered by a bioresorbable membrane ( MEM+ ) . However , just before suturing the flaps in a coronal position , the membrane over one of the two defects was removed at r and om ( MEM- ) . This protocol result ed in four groups of defects : ( i ) . MEM- AB- ; ( ii ) . MEM+ AB- ; ( iii ) . MEM- AB+ ; ( iv ) . MEM+ AB+ . Patients were monitored clinical ly and microbiologically for 1 year . Data were analyzed in repeated measures ancova 's and adjusted means for clinical variables were obtained from the final statistical model . RESULTS Reduction in probing pocket depth ( PPD ) at 12 months postoperatively varied between 2.54 and 3.06 mm between the four treatment modalities , but overall no main effect of  MEM  or  AB  was found . Gains in probing attachment level ( PAL ) at 12 months postoperatively varied between 0.56 and 1.96 mm for the 4 treatments . In the overall analysis for PAL , no main effect of  MEM or AB  was found . Gains in probing bone level ( PBL ) 12 months postoperatively ranged from 1.39 to 2.09 mm between the treatment groups . Again , overall , no main effects of  MEM or AB  were found for PBL . Explorative statistical analyses indicated that smoking and not MEM or AB is a determining factor for gain in PBL ( P = 0.0009 ) . Nonsmokers were estimated to gain 2.04 mm PBL compared to 0.52 mm in smokers . The prevalence of several periodontal pathogens , at the day of surgery or postoperatively , and specific defect characteristics , were not determining factors for gain in PAL and PBL . CONCLUSIONS Neither the application of barrier membranes nor the use of systemic antibiotics showed an additional effect over control on both soft and hard tissue measurements in the treatment of intraosseous defects . In contrast , smoking was a determining factor severely limiting gain in PBL in surgical procedures aim ed at regeneration of intraosseous defects The role of smoking as a risk factor for periodontitis was assessed separately in diabetic and nondiabetic study groups . Subject listings stratified for age ( 19 to 40 years ) and sex were obtained for subjects with insulin-dependent diabetes mellitus ( IDDM ) and nondiabetic subjects . For both the IDDM group ( n = 132 ) and the nondiabetic group ( n = 95 ) , age and sex stratified sample s were constructed by r and om selection of subjects from each subject listing . Patients were recruited by phone , examined , and their medical and dental histories obtained . Among nondiabetic subjects , the prevalence of periodontitis was markedly higher among current smokers compared with never smokers ( P < or = 0.005 ) in both the 19 to 30 year-old ( 46 % vs. 12 % ) and 31 to 40 year-old groups ( 88 % vs. 33 % ) . The subject mean percent of sites with gingival pocket depth > or = 4 mm was higher among current smokers than never smokers ( P = 0.001 ) in the 19 to 30 ( 8.2 % vs. 3.4 % ) and 31 to 40 ( 14.3 % vs. 4.3 % ) age groups . The effects of smoking among IDDM subjects were similar to that observed in the nondiabetic population . There were no differences between current and never smokers in the proportion of sites positive for plaque . Attributable risk percents from prevalence data suggest that among nondiabetic subjects , a large proportion , perhaps as much as 51 % of the periodontitis in the 19 to 30 year old group and 32 % of the periodontitis in the 31 to 40 year old group , is associated with smoking . ( ABSTRACT TRUNCATED AT 250 WORDS BACKGROUND The purpose of this r and omized , controlled , blinded , clinical investigation was to determine the effect of postsurgical antibiotics on osseous healing in Class II furcation defects . METHODS Twenty-four Class II furcation defects in 24 patients were treated with either a polylactide bioabsorbable membrane , demineralized freeze-dried bone allograft ( DFDBA ) plus antibiotics ( GBA or test group ) or with a polylactide membrane and DFDBA alone ( GB or control group ) .  Twelve patients were included in each group . The antibiotic regimen consisted of ciprofloxacin 250 mg twice daily and metronidazole 250 mg tid for 1 week followed by a 7-week regimen of doxycycline hy 
    Output:
    
Smoking has a negative effect on bone regeneration after periodontal treatment .
Patients should be advised that their smoking habit may result in poorer bone regeneration after periodontal treatment