***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: AIM The purpose of the present study is to evaluate the healing of periapical lesions of teeth with positive and negative canal cultures at the time of obturation , and to evaluate the periapical healing of teeth treated in one visit ( without ) or in two visits with an interappointment dressing of calcium hydroxide . METHODOLOGY Thirty-nine patients received root-canal treatment .  In the first visit , teeth were instrumented , and 18 of these teeth were filled ( after microbiological sampling ) with calcium hydroxide in sterile saline . The other 21 teeth were obturated with gutta-percha and AH-26 sealer after microbiological sampling . Four weeks later , the teeth with calcium hydroxide were accessed again and after microbiological sampling they were obturated with gutta-percha and AH-26 sealer .  Healing of periapical radiolucency was recorded over a period up to 4.5 years . RESULTS In both the treatment groups , the size of the periapical lesions reduced significantly during the follow-up period . Complete radiographic healing was observed in 81 % of the cases in the one-visit group , and in 71 % of the cases in the two-visit group . The probability of success increased continuously over time for both treatment groups . Seven out of eight cases ( 87.5 % ) that showed a positive root-canal culture at the time of obturation healed . The number of colony forming units ( CFU ) in six out of eight positive canals was < 10(2 ) CFU mL(-1 ) . CONCLUSIONS Within the limitations of this study , no significant differences in healing of periapical radiolucency was observed between teeth that were treated in one visit ( without ) and two visits with inclusion of calcium hydroxide for 4 weeks . The presence of a positive bacterial culture ( CFU<10(2 ) ) at the time of filling did not influence the outcome of treatment AIM This prospect i ve clinical study explored the influence of calcium hydroxide as an interappointment dressing on the healing of periapical lesions associated with pulpless teeth that had not been endodontically treated previously . This was achieved by comparing the prognosis after a two-visit root canal treatment with that following a one-visit treatment . METHODOLOGY Seventy-three patients were recruited having one tooth with an endodontically induced lesion . Of these patients , 67 could be re-examined .  Calcium hydroxide was placed in the instrumented root canals of 31 teeth for at least one week and the treatment finished at the second visit . Thirty-six teeth were root canal treated at one visit . The criteria for success were the absence of signs and symptoms indicating an acute phase of periapical periodontitis and radiographically a periodontal ligament space of normal width . Methods for event time analysis were used to evaluate and compare the prognosis of both treatment approaches . RESULTS The probability that complete periapical healing will take place increased continuously with the length of the observation period . In both treatment groups the likelihood that the root canal treatment yields a success within an observation time of five years exceeded 90 % . A statistically significant difference between the two treatment groups could not be detected . CONCLUSIONS From a microbiological perspective , one-visit root canal treatment created favourable environmental conditions for periapical repair similar to the two-visit therapy when calcium hydroxide was used as antimicrobial dressing . One-visit root canal treatment is an acceptable alternative to two-visit treatment for pulpless teeth associated with an endodontically induced lesion This study was performed to evaluate radiographic healing  of teeth with apical periodontitis , treated in one visit or in two visits ( a ) with or ( b ) without calcium hydroxide as an intracanal disinfecting medicament .  The patients were assigned one of the three treatment groups by the throwing of a die . The Periapical Index ( PAI ) Scoring Method was used to compare differences in periapical status from the beginning of treatment to a 52-wk follow-up evaluation . Overall , the periapical status of the treated teeth improved significantly after 52 wk ( p < 0.0001 ) . A PAI score of 1 or 2 was considered as representing a " good " periapical status while 3 , 4 , or 5 was a " bad " status . When base line PAI scores were controlled for , the calcium hydroxide group showed the most improvement in PAI score ( 3 , 4 , or 5 to 1 or 2 ) , followed by the one-step group ( 74 % vs. 64 % ) . The teeth that were left empty between visits had clearly inferior healing results . Power statistics were conducted to determine the numbers required for significant differences between the groups , and it was shown that large experimental groups on the order of hundreds of patients would be required to show significant differences 
    Output:
    
The authors draw the conclusion , using defective review material , that removal of smear layer enhances the seal of the root filling .