***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 aim of this investigation was to compare root resorption in the same individual after application of continuous intrusive and extrusive forces . In nine patients ( mean age 15.3 years ) , the maxillary first premolars were r and omly intruded or extruded with a continuous force of 100 cN for eight weeks . Eleven maxillary first premolars from six r and omly selected orthodontic patients served as controls . Root resorption was determined using scanning electron microscopy . Quantitative assessment of the percentage of resorbed area of the total root surface was performed on composite micrographs . The severity of root resorption was also assessed by visual scoring of the roots . Root resorption mainly occurred at the apical part of the roots in both experimental groups . A significant difference in root resorption was found between the intruded and the control teeth ( P = .006 ) but not between the extruded and the control teeth . However , the mesial and distal root surfaces showed resorption on 5.78 + /- 3.86 % of the root surface of the intruded teeth and 1.28 + /- 1.24 % of the root surface of the extruded teeth , and this difference was significant ( P = .004 ) . In addition , a large individual variation was found . From this study , it can be concluded that intrusion of teeth causes about four times more root resorption than extrusion . Because the amount of root resorption due to intrusion or extrusion in the same patient is correlated , every clinician should be aware that the extrusion of teeth might also cause root resorption in susceptible patients Background Examination with Cone Beam CT ( CBCT ) is common for localizing maxillary canines with eruption disturbance . The benefits and costs of these examinations are unclear . Objectives To measure : 1 . the proportion of orthodontists ' treatment decisions that were different based on intraoral and panoramic radiography ( M1 ) compared with CBCT and panoramic radiography ( M2 ) ; and 2 . the costs of producing different treatment plans , regarding patients with maxillary canines with eruption disturbance . Subjects and methods Orthodontists participated in a  web-based survey and were r and omly assigned to denote treatment decisions and the level of confidence in this decision for four patient cases presented with M1 or M2 at two occasions for the same patient case . Results One hundred and twelve orthodontists made 445 assessment s based on M1 and M2 , respectively . Twenty-four per cent of the treatment decisions were different depending on which method the raters had access to , whereof one case differed significantly from all other cases . The mean total cost per examination was € 99.84 using M1 and € 134.37 using M2 , result ing in an incremental cost per examination of € 34.53 for M2 . Limitations Benefits in terms of number of different treatment decisions must be considered as an intermediate outcome for the effectiveness of a diagnostic method and should be interpreted with caution . Conclusions For the patient cases presented in this study , most treatment decisions were the same irrespective of radiological method . Accordingly , this study does not support routine use of CBCT regarding patients with maxillary canine with eruption disturbance OBJECTIVE : To assess the prevalence of  severe external root resorption  and its potential risk factors result ing from  orthodontic treatment .  METHODS : A r and omly selected sample was used . It comprised conventional periapical radiographs taken in the same radiology center for maxillary and m and ibular incisors before and after active orthodontic treatment of 129 patients , males and females , treated by means of the St and ard Edgewise technique .  Two examiners measured and defined root resorption according to the index proposed by Lev and er et al. The degree of external apical root resorption was registered defining resorption in four degrees of severity . To assess intra and inter-rater reproducibility , kappa coefficient was used . Chi-square test was used to assess the relationship between the amount of root resorption and patient 's sex , dental arch ( maxillary or m and ibular ) , treatment with or without extraction s , treatment duration , root apex stage ( open or closed ) , root shape , as well as overjet and overbite at treatment onset . RESULTS : Maxillary central incisors had the highest percentage of severe root resorption , followed by maxillary lateral incisors and m and ibular lateral incisors . Out of 959 teeth , 28 ( 2.9 % ) presented severe root resorption . The following risk factors were observed : anterior maxillary teeth , overjet greater than or equal to 5 mm at treatment onset , treatment with extraction s , prolonged therapy , and degree of apex formation at treatment onset . CONCLUSION : This study showed that care must be taken in orthodontic treatment involving extraction s , great retraction of maxillary incisors , prolonged therapy , and /or completely formed apex at orthodontic treatment onset OBJECTIVE To evaluate the perception of Greek and Swedish orthodontic practitioners regarding the possible occurrence and prognosis of root resorption occurring during orthodontic treatment  and to estimate practitioners ' approaches to the diagnosis of preexisting root resorption , screening of prevalence , and treatment planning approach when moderate or severe root resorption is present . MATERIAL S AND METHODS Question naires were received from r and omly selected Greek ( n = 90 ) and Swedish ( n = 106 ) practitioners . Topics of the questions included ( a ) the presence of history ; ( b ) the radiographic evaluation of root resorption  before , during , and after treatment ; ( c ) the treatment approach of initial prevention and protocol s in cases of radiographic diagnosis of root resorption during treatment . RESULTS Of the respondents , 47.1 % of the Swedish practitioners and 32.3 % of the Greek practitioners use  periapical and panoramic radiographs  to diagnose root resorption , mostly in the anterior region . Both groups recognize trauma , root form , and oral habits as predisposing factors . The majority of Swedish orthodontists perform  radiographic follow-up in the first 6 months . In contrast , the Greek orthodontists perform it at 1 year or at the end of treatment . The treatment approach for root resorption that is most frequently used by Swedish orthodontists is altering the treatment plan , using light forces , and allowing resting periods , while the Greek orthodontists most frequently use lighter forces and reduce the total duration of the treatment . CONCLUSIONS Because there is no specific approach offered in the literature , the prevention and treatment re assessment in cases of root resorption relies on individual practitioner perception OBJECTIVE : To test the feasibility of creating a valid and reliable checklist with the following features : appropriate for assessing both r and omised and non-r and omised studies ; provision of both an overall score for study quality and a profile of scores not only for the quality of reporting , internal validity ( bias and confounding ) and power , but also for external validity . DESIGN : A pilot version was first developed , based on epidemiological principles , review s , and existing checklists for r and omised studies . Face and content validity were assessed by three experienced review ers and reliability was determined using two raters assessing 10 r and omised and 10 non-r and omised studies . Using different raters , the checklist was revised and tested for internal consistency ( Kuder-Richardson 20 ) , test-retest and inter-rater reliability ( Spearman correlation coefficient and sign rank test ; kappa statistics ) , criterion validity , and respondent burden . MAIN RESULTS : The performance of the checklist improved considerably after revision of a pilot version . The Quality Index had high internal consistency ( KR-20 : 0.89 ) as did the subscales apart from external validity ( KR-20 : 0.54 ) . Test-retest ( r 0.88 ) and inter-rater ( r 0.75 ) reliability of the Quality Index were good . Reliability of the subscales varied from good ( bias ) to poor ( external validity ) . The Quality Index correlated highly with an existing , established instrument for assessing r and omised studies ( r 0.90 ) . There was little difference between its performance with non-r and omised and with r and omised studies . Raters took about 20 minutes to assess each paper ( range 10 to 45 minutes ) . CONCLUSIONS : This study has shown that it is feasible to develop a checklist that can be used to assess the method ological quality not only of r and omised controlled trials but also non-r and omised studies . It has also shown that it is possible to produce a checklist that provides a profile of the paper , alerting review ers to its particular method ological strengths and weaknesses . Further work is required to improve the checklist and the training of raters in the assessment of external validity INTRODUCTION There is still ambiguity about whether continuous or intermittent orthodontic forces produce more root resorption . This prospect i ve r and omized clinical trial was design ed to compare root resorption with these 2 force application patterns . METHODS The sample consisted of 16 maxillary first premolars from 8 patients who required bilateral extraction s as part of their orthodontic treatment . In each subject , a fixed experimental appliance was placed on the maxillary teeth on each side , allowing a buccally directed force . The force was generated by a segmental wire of beta-titanium-molybdenum alloy . The first premolar on 1 side received a buccally directed continuous force , and the contralateral premolar received intermittent force . The initial force magnitude for both sides was 225 cN. After 14 days of initial continuous force , the intermittent force application was obtained with subsequently repeated periods until the end of the eighth week of a 3-day rest period followed by a 4-day force application period . Force levels were set to 225 cN at each patient visit . After the experimental period of 8 weeks , the teeth were extracted under a strict protocol to prevent root surface damage and analyzed with a microcomputed-tomography scan system , and specially design ed software was used for direct volumetric measurements . RESULTS Intermittent force produced less root resorption than continuous force ( P < 0.05 ) . Analysis by position showed that the buccal-cervical region had significantly more root resorption than the other positions ( P < 0.001 ) , corresponding to a region of compression generated by tipping . CONCLUSIONS The application of intermittent orthodontic forces of 225 cN for 8 weeks ( 14 days of force application , 3 days of rest , then 4 days of force application repeated for 6 weeks ) caused less root resorption than continuous forces of 225 cN for 8 weeks . Although it might not be clinical ly practical , compared with continuous forces , intermittent forces might be a safer method to prevent significant root resorption . This regimen , however , could compromise the efficiency of tooth movement Aim : The aim of this prospect i ve study was to radiographically assess root morphology changes in maxillary and m and ibular premolars following Herbst appliance treatment . Patients and Methods : Twenty-five consecutive adolescents ( 19 boys and six girls , mean age 13.08 years ) with Class II , Division 1 malocclusion were treated with the b and ed Herbst appliance  for a mean period of 13.16 months . Periapical radiographs of the upper and lower premolars were obtained before appliance insertion and immediately after appliance removal using the parallel technique . All radiographs were scanned , digitized and analyzed using appropriately adjusted cephalometric software . The pre- and post-treatment length and area of the first and second maxillary and m and ibular premolar roots were calculated . Statistical analysis included paired t-tests to evaluate pre- and posttreatment changes , and independent t-tests to compare the pre and post-treatment differences between the first and the second premolars , which served as controls . The level of significance was set at p ≤ 0.05 for all tests . Results : No statistically significant decrease in premolar root lengths or areas was noted following removal of the Herbst appliance . We observed a statistically-significant decrease in the root area of the first m and ibular premolars compared to that of the second m and ibular premolars . Conclusions : Although we observed no statistically-significant root morphology changes in the first and second premolars following Herbst appliance treatment , the m and ibular first premolars revealed significantly more root resorption than did the m and ibular second premolars . ZusammenfassungZiel : Ziel dieser prospektiven Studie war , radiologische Veränderungen der Wurzelmorphologie an Oberkiefer- und Unterkieferprämolaren nach einer Beh and lung mit der Herbst-Apparatur nachzuweisen . Patienten und Method ik:25 aufein and er folgende jugendliche Patienten ( 19 Jungen und sechs Mädchen , mittleres Alter 13,08 Jahre ) mit einer Klasse-II/1-Anomalie wurden i m Schnitt für 13,16 Monate mit einem an Bändern befestigten Herbst-Scharnier beh and elt . Periapikale Röntgenaufnahmen der oberen und unteren Prämolaren wurden vor dem Einsetzen und unmittelbar nach der Entfernung der Apparatur mittels der Paralleltechnik angefertigt . Alle Röntgenaufnahmen wurden eingescannt , digitalisiert und mittels einer adäquat angepassten kephalometrischen Software analysiert . Die Wurzellänge und -fläche der ersten und zweiten Ober- und Unterkieferprämolaren wurden sowohl vor als auch nach der Beh and lung berechnet . Die statistische Analyse enthielt paarige t-Tests zur Evaluation der eingetretenen Veränderungen und unabhängige t-Tests , um diese Veränderungen bei den ersten Prämolaren mit denen der zweiten Prämolaren , die als Kontrollgruppe dienten , zu vergleichen . Das Signifikanz niveau wurde für alle Tests auf p ≤ 0,05 gesetzt . Ergebnisse : Es wurde keine statistisch signifikante Abnahme der Wurzellänge und -fläche der Prämolaren nach Entfernung der Herbst-Apparatur nachgewiesen . Eine statistisch signifikante Abnahme der Wurzelfläche der ersten unteren Pr 
    Output:
    
Statistically significant differences in OIRR were found according to tooth type or jaw , inclusion of extraction s , treatment duration , and diagnostic accuracy of the CBCT .
Conclusions Based on the results of this study , CBCT seems to be a reliable tool to examine OIRR during or at the end of orthodontic treatment .
Although the average OIRR measured with CBCT seems to lack clinical relevance , there are certain factors that may affect OIRR following orthodontic treatment .