***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: BACKGROUND Several recent studies have indicated that total antioxidant capacity ( TAOC ) of plasma seems to be compromised in chronic periodontitis ( ChP ) . The aim of this study is to investigate plasma TAOC in patients with ChP and to assess the effects of vitamin C as an adjunct to non-surgical periodontal treatment . METHODS The study population consisted of 60 subjects : 30 diagnosed with ChP and 30 matched controls . Furthermore , patients from the ChP group were r and omly allocated into ChP1 ( 15 patients received non-surgical treatment with adjunctive dose of vitamin C ) and ChP2 ( 15 patients received non-surgical periodontal treatment alone ) . Plasma TAOC levels were measured by an ABTS assay at baseline and 1 month post-therapy . RESULTS Plasma TAOC levels were significantly lower in ChP patients than controls ( P < 0.001 ) . The periodontal therapy result ed in increasing plasma TAOC and improvements in clinical measures among both ChP1 and ChP2 groups ( P < 0.001 ) . However , the adjunctive dose of vitamin C did not offer additional effect ( P > 0.05 ) . CONCLUSIONS ChP is significantly associated with lower levels of plasma TAOC . The non-surgical periodontal therapy seems to reduce the oxidative stress during the periodontal inflammation . However , the use of adjunctive vitamin C still needs further investigation BACKGROUND Reactive oxygen species might be associated with the onset and progression of gingival inflammation . The aim of this study is to investigate the effect of a dentifrice containing L-ascorbic acid 2-phosphate magnesium salt ( APM ) , a long-acting ascorbic acid derivative with antioxidant properties , on  gingival inflammation . METHODS The clinical effects of APM were investigated in a multicenter , r and omized , parallel-group , controlled clinical trial comprising 300 individuals with gingivitis . Half of the participants were given an APM-containing dentifrice and half were given a control dentifrice . The primary outcome was the gingival index ( GI ) at 3 months . Secondary outcomes included gingival redness as an indicator of the degree of local gingival inflammation , gingival bleeding as a measure of the gingivitis severity index , and total antioxidant activity of the saliva . RESULTS Under the intent-to-treat analysis , GI did not significantly differ between the groups ( P = 0.12 ) . However , under the per- protocol analysis , GI was significantly lower in the APM group ( P = 0.01 ) than in the control group . In the APM group , gingival redness was significantly lower , and the difference from the baseline gingivitis severity index was significantly greater ( P = 0.04 and P = 0.02 , respectively ) . The total antioxidant activity of the saliva was significantly higher in the APM group ( P = 0.03 ) . The incidence of adverse events did not significantly differ between the groups ( P > 0.15 ) . CONCLUSION These findings indicate that the regular application of an APM-containing dentifrice could reduce gingival inflammation ABSTRACT Background : Deficient ascorbic acid levels ( AALs ) and Type 2 diabetes mellitus ( T2DM ) are associated with periodontal disease . This study evaluated the relationship between plasma AAL and periodontitis in systemically healthy and T2DM subjects , which to the best of our knowledge is being reported for the first time . Methods : One hundred twenty subjects were categorized into four groups of 30 each as group 1 : without periodontal disease ; group 2 : chronic gingivitis ; group 3 : chronic periodontitis , and group 4 : chronic periodontitis and freshly diagnosed T2DM .  Plaque index ( PlI ) , sulcus bleeding index ( SBI ) , and probing pocket depths ( PPDs ) were evaluated . Venous blood was evaluated for plasma AAL spectrophotometrically . R and omized subjects were subgrouped within groups 2–4 , to receive either scaling and root planing ( SRP ) with dietary supplementation ( 450 mg ) of ascorbic acid ( AA ) for two weeks or only SRP . After two weeks , the clinical parameters were reassessed . Tukey 's multiple post hoc procedures and paired t test were used with the level of statistical significance adjusted to p ≤ .05 . Results : AAL plasma levels were significantly greater in group 1 than in group 2 ( p = .0007 ) and in group 4 ( p = .0003 ) . A significant reduction in the SBI was seen in the subgroups that received dietary supplementation of vitamin C within group 2 ( p = .0012 ) and group 4 ( p = .036 ) . Conclusions : Plasma AAL is below the normal range in systemically healthy subjects with gingivitis and diabetics with periodontitis  . Dietary AA supplementation with SRP improves the SBI in subjects with gingivitis and diabetics with periodontitis Identification of the cause of the development and progression of periodontitis has received extensive attention , with notable advances over the past decade in clinical , microbiological , immunological , biochemical , and behavioral knowledge . However , it is still largely unknown which factors lead to the conversion of non-destructive forms of periodontal disease into destructive forms and disease progression . Chronic adult periodontitis is believed to be influenced by an interaction of host defense and environmental factors . Although these variables have been studied extensively , no study has employed r and omized controlled prospect i ve human or r and omized controlled community intervention design s , method ologies necessary to prove a variable to be a cause of periodontitis . Owing to the absence of literature employing rigorous experimental design , this article assesses systematic ally observational , cross-sectional and longitudinal studies to examine the potential causal association between cigarette smoking and  periodontitis . The methodology of Sir Bradford Hill 's criteria for causation was used as the framework . Results suggest that cigarette smoking is causally associated with periodontitis . That is , cigarette smoking is consistently associated with an increased prevalence/severity of periodontitis and is suspected on theoretical grounds of playing a causal role . Hill 's criteria provide a useful methodology to better underst and the pathogenesis of periodontal diseases and may be applied to study the pathogenesis of other dental diseases as well Objective Previous studies demonstrate a relationship between a lack of vitamin C and increased risk of periodontal disease . In the present study we examine the  vitamin C plasma levels and inflammatory measures in periodontitis patients before and after the consumption of grapefruit .  Subjects and methods Fifty-eight patients with chronic periodontitis were assigned to the test group ( non-smokers n=21 , smokers n=17 ) and a diseased control group ( non-smokers n=11 , smokers n=9 ) . Furthermore , 22 healthy subjects were recruited to compare vitamin C plasma levels between periodontally diseased and healthy subjects . Clinical evaluations , including plaque index ( PI ) , sulcus bleeding index ( SBI ) , probing pocket depths ( PPD ) and plasma vitamin C levels , were performed at baseline , and after two weeks of grapefruit consumption . Results At baseline , we observed significantly reduced plasma vitamin C levels in the test group and diseased controls in comparison with the healthy controls . On principle , smokers showed lower levels of vitamin C ( mean 0.39 ± 0.17 mg dl−1 ) than non-smokers ( mean 0.56±0.29 mg dl−1 ) . After grapefruit consumption , the mean plasma vitamin C levels rose significantly in the test group compared to the diseased controls ( non-smokers : 0.87±0.39 mg dl−1 , smokers : 0.74±0.30 mg dl−1 ) . Furthermore the SBI was reduced in the test group ( non-smokers : from 1.68±0.6 to 1.05±0.6 , p<0.001 ) , whereas PI and PPD were unaffected . Conclusion The present results show that periodontitis patients are characterised by plasma vitamin C levels below the normal range , especially in smokers . The intake of grapefruit leads to an increase in plasma vitamin C levels and improves sulcus bleeding scores . Longer term studies are necessary to determine whether other periodontal outcomes improve with such supplementation especially in smokers OBJECTIVE To determine the relationship between serum vitamin C and periodontitis as estimated by clinical attachment loss ( CAL ) in community-dwelling elderly Japanese . MATERIAL AND METHODS This analysis was confined to 413 Niigata citizens aged 70 years in whom the data for serum vitamin C and CAL were available .  High-pressure liquid chromatography method was used to ascertain the serum vitamin C levels while  CAL  was assessed on six sites of all teeth present including third molars by means of pressure-sensitive probes . Other variables included gender , smoking , toothbrushing frequency , number of teeth present and r and om blood sugar levels . RESULTS Serum vitamin C concentration was inversely related to CAL ( r=-0.23 , p<0.00005 ) at bivariate level . Multiple linear regression analysis showed that CAL was 4 % greater in subjects with lower serum vitamin C levels than in subjects with higher serum vitamin C levels notwithst and ing smoking , diabetes , oral hygiene , gender or number of teeth present . CONCLUSION The findings suggested that serum vitamin C might have relatively weak but a statistically significant relationship with periodontitis in this elderly population UNLABELLED Forty adult female rats were r and omly divided into four groups : control , nicotine , nicotine+vitamin C and nicotine+selenium group . Splenic tissues concentrations of thiobarbituric acid reactive substances ( TBARS ) , nitric oxide , superoxide dismutase ( SOD ) and catalase ( CAT ) activities were measured . The P53 and Bcl2 proteins were detected by Western blot and their expression in splenic tissues were measured by quantitative real time PCR in all groups . Compared to control group , nicotine increased the concentrations of TBARS and nitric oxide significantly . However , Vit . C or Se supplementation with nicotine caused a significant decrease in these concentrations . SOD and CAT activities of nicotine group decreased significantly compared to control group . Treatment with Vit . C or Se plays a significant role in elevation of SOD and CAT activities . In splenic tissues , nicotine significantly decreases the protein levels and the mRNA expression of P53 and increases the protein levels of Bcl2 and its expression . Administration of Vit . C. to nicotine-treated rats completely reversed the decrease in P53 levels and its mRNA expression and the increase in Bcl2 levels and its mRNA expression to the control values . In contrast , Se administration did not induce any significant changes in these genes levels or expressions compared to nicotine group . CONCLUSION Vit . C supplementation to nicotine treated rats was more effective than selenium in attenuation of nicotine-induced oxidative stress , p53 and Bcl2 expression in rat spleen tissues 
    Output:
    
The patients with a lower dietary intake or lower blood level of vitamin C  showed a greater progression of periodontal disease than the controls .
The intervention using vitamin C administration improved gingival bleeding in gingivitis , but not in periodontitis .
Alveolar bone absorption was also not improved .
The present systematic review suggested that vitamin C contributes to a reduced risk of periodontal disease