***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: INTRODUCTION Bacterial plaque is an etiologic factor in the development of gingival inflammation and periodontitis . The presence of orthodontic b and s and brackets influences plaque growth and maturation . The purpose s of this research were to monitor microbiologic and periodontal changes after placement of orthodontic attachments over a 1-year period and to link these changes to alterations in cytokine concentrations in the gingival crevicular fluid ( GCF ) . METHODS This longitudinal split-mouth trial included 24 patients .  Supragingival and subgingival plaque composition , probing depth , bleeding on probing , and  GCF flow and composition  were assessed at baseline ( Tb ) and after 1 year ( T52 ) . A statistical comparison was made over time and between the b and ed and bonded sites . Prognostic factors for the clinical reaction at T52 in the GCF at Tb were determined . RESULTS Between Tb and T52 , the pathogenicity of the plaque and all periodontal parameters increased significantly , but intersite differences were not seen , except for bleeding on probing . The cytokine concentrations in the GCF did not differ significantly between the sites or between Tb and T52 . The interleukin-6 concentration in the GCF at Tb was a significant predictive value for the GCF flow at T52 ( P < 0.05 ) . The same relationship was found between the interleukin-8 concentration at Tb and the increase in probing depth at T52 ( P < 0.05 ) . CONCLUSIONS Interleukin-6 and interleukin-8 concentrations before orthodontic treatment were shown to be significant predictive factors for some potential inflammatory parameters during treatment Das Ziel der hier vorgestellten Untersuchung war es , die Auswirkung von Intrusion sowie Extrusion auf die Blutversorgung der Pulpa am Menschen zu ermitteln . Die Unterschiede der Durchblutungsänderungen wurden an zehn lateralen Inzisiven ( sechs Prob and en ) durch Laser Doppler Flowmetry ( Perimed , Sweden ) mittels an den bukkalen Flächen der Zähne befestigter Metallröhrchen gemessen . Die Brackets wurden an den Zähnen 13 und 23 befestigt , und intrusive bzw . extrusive Kräfte von 2 N wurden an den zu untersuchenden Zähnen über einen Zeitraum von fünf Minuten appliziert . Der jeweilige kontralaterale Zahn diente als Kontrolle . Die Extrusion bewirkte keine signifikante Veränderung des Pulpablutdurchflusses weder während noch nach der Aufhebung der extrusiven Kräfte . Intrusive Kräfte reduzierten jedoch während der ersten Minute der Kraftapplikation den Pulpablutdurchfluß um 20 % . Während der nächsten vier Minuten kam es zu einer kontinuierlichen Zunahme des Pulpablutdurchflusses in Richtung des Ausgangswertes , und drei Minuten nach Aufhebung der Kraft erreichte er wieder den normalen Wert . Zusammenfassend kann festgestellt werden , daß die orthodontische Intrusion mit einer Kraft von 2 N eine temporäre Reaktion des Pulpablutdurchflusses hervorrief , die Extrusion hingegen keine Auswirkung auf den Pulpablutdurchfluß hatte . The purpose of the present investigation was to measure the effect of tooth intrusion and extrusion on pulpal blood flow in man . The flow changes were measured in 10 lateral incisors ( 6 subjects ) by means of laser Doppler flowmetry ( Perimed , Sweden ) applied on the buccal surface through metal tubes bonded to the teeth . Brackets were bonded onto teeth 13 and 23 , and intrusive and extrusive forces of 2 N were applied in r and om order to the experimental tooth for 5 min before unloading . The contralateral tooth served as a control . Extrusion of the teeth gave no significant changes in pulpal blood flow during loading or unloading , However , intrusion of the teeth reduced the pulpal blood flow by 20 % during the first minute after force application . The pulpal blood flow gradually increased towards the preloading flow values for the next 4 min , and was returned to the prestimulus level 3 min after unloading . In conclusion orthodontic intrusion of teeth with a 2 N force evoked a temporary reduction in the pulpal blood flow , whereas extrusion had no effect on the pulpal blood flow A careful review of the literature reveals an absence of studies about the reactions of dental pulp to orthodontic extrusion . The purpose of the present research investigation is to study the pulpal reactions and the sequence of histologic events in human dental pulp after orthodontic extrusion . The sample consisted of 36 intact maxillary first premolars of young adult orthodontic subjects . The mean age of the subjects was 18 years . Eighteen maxillary first premolars were extruded , under controlled conditions with the aid of fixed edgewise orthodontic appliances , for either 1 , 2 , or 4 weeks . The contralateral maxillary first premolars were not extruded and were used as controls . Immediately after removal of the appliances , all the maxillary first premolars were extracted . The pulps were histologically examined in a double-blind experiment . The results obtained from this study indicate that certain characteristic pulpal reactions arise from orthodontic extrusion . These reactions involve circulatory disturbances with congested and dilated blood vessels , odontoblastic degeneration , vacuolization and edema of the pulp tissues , and ( by the fourth week ) manifestation of fibrotic changes . It is speculated that the vacuolization of the pulp tissues ( which occurred after the application of extrusive orthodontic forces in young adult subjects ) result ed from a prolapse of the pulp , made possible by the relatively wide apical foramina . However , the odontoblastic degeneration is most probably the result of a compromised blood supply . The authors believe that this study constitutes a building block for establishing a more complete biologic foundation for orthodontic tooth movement . Further studies are suggested to reach more definitive conclusions OBJECTIVE To determine the levels of two sensory neuropeptides ( substance P [ SP ] and calcitonin gene-related peptide [ CGRP ] ) and two endogenous opioids ( methionine-enkephalin [ Met-Enk ] and β-endorphin [ β-End ] ) in dental pulp tissue sample s subjected to controlled orthodontic intrusive forces . MATERIAL S AND METHODS Sixteen healthy premolars were selected from eight patients who were undergoing extraction for orthodontic purpose s. Eight were r and omly used as controls , and the other eight were assigned to an experimental group ( controlled orthodontic intrusive forces applied for 24 hours ) . After this period , teeth were extracted , and pulp sample s were obtained . All sample s were processed to quantify the expression levels of SP , CGRP , Met-Enk , and β-End using commercial radioimmunoassay kits . RESULTS All sample s exhibited basal levels of both neuropeptides and endogenous opioids . After 24 hours of the intrusive stimulus , all patients reported a tolerable discomfort localized at the involved premolar . Only SP was significantly increased ( P<.05 ) . For the other molecules , no statistically significant differences were observed ( P>.05 ) ; however , they expressed important increasing trends . CONCLUSIONS The expression levels of SP and CGRP in dental pulp sample s from the experimental group support the positive correlation between the symptomatic clinical scenario and increased expression levels of neuropeptides , clarifying the role of neurogenic inflammation in early injury response This study examines the aspartate aminotransferase activity in the pulp of orthodontically treated teeth . Seventeen healthy male and female subjects ( ages : 14.5 - 19.6 ; mean 16.8 + /- 1.6 years ) who needed extraction of the maxillary first premolars for orthodontic reasons were enrolled in the study . One r and omly chosen maxillary first premolar , included in a straight-wire fixed orthodontic appliance and supporting orthodontic force , was considered as the test tooth . The contralateral first premolar , included in the orthodontic appliance but not subjected to mechanical stress , was used as the control tooth . After a week of treatment , the dental pulp tissues were extracted from both experimental teeth . Aspartate aminotransferase activity was significantly elevated in the test teeth as compared with the control teeth . These results demonstrate that in the early phases of treatment , orthodontic force application to the teeth can lead to significant metabolic changes in the pulp of these teeth INTRODUCTION The forces applied during orthodontic treatment bring about effects on the teeth and surrounding tissues . The aim of this study was to evaluate the possible changes in the human pulpal tissue result ing from orthodontic intrusion in a 21-day period using histologic examination . METHODS The sample consisted of 17 young individuals of both sexes between the ages of 12 and 19 years . A total of 34 premolars were evaluated with orthodontic indication of extraction . Because it is a split-mouth study , in each patient , intrusion force of 60 g was applied r and omly on 1 of the dental elements experimental group for 21 days . The counterpart control group received no force . After extraction s , these dental elements were fixed in 10 % formaldehyde , processed automatically , su bmi tted to histotechnical preparation , and stained with hematoxylin-eosin for analysis under optical microscope . RESULTS The paired Fisher exact test ( P ≤ .05 ) showed a significant increase of fibrous tissue in the experimental group . The nonparametric paired Wilcoxon test ( P ≤ .05 ) showed a significant increase in the number of pulpal nodules in the elements of the experimental group and showed no difference in the number of blood vessels between the groups . Large-caliber vessels and congested elements were observed in 8 of the experimental group elements . CONCLUSIONS The orthodontic intrusion force , in these conditions , caused vascular changes in the pulpal tissue and also increased the presence of fibrosis and the number of pulp calcifications in the experimental elements This study investigates the effect of an orthodontic force on pulpal respiration in the human premolar . The participants in this study required the removal of four first premolars for orthodontic treatment .  After written consent was obtained , these teeth were used in the following manner . R and omly , the premolars on one side of the mouth were design ated as experimental and the premolars on the opposing side served as controls . The four teeth were removed following a 3-day application of an orthodontic force . The pulp tissue was then extirpated and used for the investigation . A radioactively labeled carbon dioxide production system was used to evaluate the effect on pulpal respiration of the orthodontic force . It is thought that this method has been proved to provide a viable and sensitive biochemical analysis of tissue respiration on very small sample s over short observation periods . The data were collected and prepared for statistical analysis . This investigation demonstrated that the pulp tissue respiration in seventeen subjects was depressed an average of 27 % as a result of orthodontic force application . A positive correlation between the age of the participant and the amount of tissue respiratory depression was also demonstrated . It was therefore concluded that orthodontic forces of very short duration do cause biochemical and biologic pulpal tissue alterations and that orthodontic forces may be less biologically safe as the age of the patient increases INTRODUCTION The aim of this study was to examine alkaline phosphatase ( ALP ) activity in the dental pulp of orthodontically treated teeth . METHODS Sixteen healthy subjects ( mean age 17.0 + /-1.6 years ) who required extraction of 4 first premolars for orthodontic reasons participated . One maxillary first premolar subjected to orthodontic force was the test tooth . The contralateral first premolar , bracketed but not subjected to mechanical stress , was the control tooth . After a week of treatment , the first premolars were extracted and the dental pulp removed from the teeth . ALP activity was determined spectrophotometrically and the results expressed as units/liter per milligram of pulp tissue [ U/(L x mg ) ] . RESULTS ALP activity was 89 + /- 26 U/(L x mg ) in the test teeth and 142 + /- 33 U/(L x mg ) in the control teeth . The difference between the groups was statistically significant ( P < .01 ) . CONCLUSIONS Orthodontic treatment can lead to significant early-phase reduction in ALP activity in human dental pulp tissue 
    Output:
    
However , a history of dental trauma maybe considered a risk factor for loss of pulp vitality during orthodontic treatment