The impact of antioxidant agents complimentary to periodontal therapy on oxidative stress and periodontal outcomes : a systematic review

Review

The

impact

of

antioxidant

agents

complimentary

to

periodontal

therapy

on

oxidative

stress

and

periodontal

outcomes:

A

systematic

review

Francisco

Wilker

Mustafa

Gomes

Muniz

*

,

Sergiana

Barbosa

Nogueira

,

Francisco

Lucas

Vasconcelos

Mendes

,

Cassiano

Kuchenbecker

Ro¨sing

,

Maria

Moˆnica

Studart

Mendes

Moreira

,

Geanne

Matos

de

Andrade

,

Rosimary

de

Sousa

Carvalho

a

Post-GraduatePrograminDentistry,FederalUniversityRioGrandedoSul,RuaRamiroBarcelos,2492,PortoAlegre, RioGrandedoSul90035-003,Brazil

b_{SchoolofDentistry,FacultyofPharmacy,DenstistryandNursing,FederalUniversityofCeara´,}

RuaAlexandreBarau´na,949,Fortaleza,Ceara´ 60430-160,Brazil

c_{DisciplineofPeriodontology,SchoolofPharmacy,DentistryandNursing,FederalUniversityCeara´,}

RuaAlexandreBarau´na,949,Fortaleza,Ceara´ 60430-160,Brazil d

DepartmentofPhysiologyandPharmacology,FacultyofMedicine,FederalUniversityCeara´, RuaAlexandreBarau´na,949,Fortaleza,Ceara´ 60430-160,Brazil

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Accepted19May2015

Keywords:

Chronicperiodontitis Periodontaldiseases Vitamins

Respiratoryburst Reactiveoxygenspecies Superoxidedismutase

a

b

s

t

r

a

c

t

Thereissignificantevidencelinkingchronicperiodontitis(CP)andoxidativestress(OS). CPisamultifactorialinfecto-inflammatorydiseasecausedbytheinteractionofmicrobial agents present in the biofilm associated with hostsusceptibility and environmental factors.OSisaconditionthatariseswhenthereisanimbalancebetweenthelevelsof freeradicals(FR)anditsantioxidantdefences.Antioxidants,definedassubstancesthat areabletodelayorpreventtheoxidationofasubstrate,existinallbodilytissuesand fluids,andtheirfunctionistoprotectagainstFR.Thissystematicreviewassessedthe effectsofthecomplimentaryuseofantioxidantagentstoperiodontaltherapyintermsof oxidativestress/antioxidants.Onlyrandomised,controlled,double-blindorblindstudies wereincluded.Themajorityoftheincludedstudieswereperformedinchronic periodon-titispatients.Lycopene,vitaminC,vitaminE,capsuleswithfruits/vegetables/berryand dietaryinterventionsweretheantioxidantapproachesemployed.Onlythestudiesthat usedlycopeneandvitaminEdemonstratedstatisticallysignificantimprovementwhen compared toa controlgroupintermsof periodontalparameters.However,oxidative

*Correspondingauthor.Tel.:+558596520187/5195715453.

E-mailaddresses:wilkermustafa@gmail.com(F.W.M.G.Muniz),sergianab@gmail.com(S.B.Nogueira),lucas_v_mendes@hotmail.com

(F.L.V.Mendes),ckrosing@hotmail.com(C.K.Ro¨sing),monicastudartmoreira@gmail.com(M.M.S.M.Moreira),

gmatos@ufc.br(G.M.deAndrade),roseperio@yahoo.com.br(R.d.S.Carvalho).

Abbreviations: CP, chronic periodontitis; OS, oxidative stress; FR,free radicals; ROS, reactive oxygen species; SOD, superoxide dismutase;CAT,catalase;GPx,glutathioneperoxidase;SRP,scalingandrootplanning;8-OHdG,8-hydroxydeoxyguanosine;TAOC,total antioxidantcapacity;ELISA,enzymelinkedimmunosorbentassay.

Available

online

at

www.sciencedirect.com

ScienceDirect

journalhomepage:http://www.elsevier.com/locate/aob

http://dx.doi.org/10.1016/j.archoralbio.2015.05.007

Contents

1. Introduction ... 1204

2. Methodology ... 1204

3. Results... 1205

4. Discussion... 1210

5. Conclusions... 1212

References... 1212

1.

Introduction

Periodontitisisachronicinfecto-inflammatorydisease pre-senting inflammation ofthe periodontal tissues that cause alveolarbonelossand,insomeseverecases,toothexfoliation.1 Progressionofperiodontaldiseaseisdependentonthehost immuneresponseandsusceptibility.2,3_{Recently,studieshave} pointedtooxidativestressasbeingpartofthepathogenesisof periodontaldiseases.4Oxidativestressisaconditioncausedby aharmfulincreaseintheproductionofreactiveoxygenspecies (ROS),5 _{which are important signalling molecules in the} regulationofseveralcellularprocesses,6_{emergingwhenthere} isanimbalancebetweenROSlevelsandthehostantioxidant defences.Consequencesoftheoxidativestressinclude adap-tation,damageorcelldeath7_{throughavarietyofmechanisms,} suchasDNA,lipidandproteindamage.8

RegardingthepreventionofROSformation,enzymaticand non-enzymaticantioxidantmechanismshavebeenstudiedand reportedintheliterature.Enzymaticmechanismsare responsi-blefordirectROSneutralisation,4,9,10andthesemechanismsare constitutedbyprimaryenzymesinvolvedinhumanorganism protectioninattempttomaintaintheROSlevelsinanormal range.Examplesoftheseenzymesaresuperoxidedismutase (SOD),catalase(CAT)andglutathioneperoxidase(GPx).

Superoxidedismutase(SOD)isoneofthemostabundant antioxidant enzymes in the human body.11,12 _{One of its} mechanismsofactionistheconversionofsuperoxideanions intohydrogenperoxide(H2O2),whichoperatesasapreventive antioxidantbecauseit avoidstheformation ofthehydroxyl radical (OH ).13 _{The SOD levels are reduced in chronic} periodontitispatientswhencomparedwithcontrols,12andit hasbeenshownthat,afterscalingandrootplaning(SRP),its serumandsalivarylevelswereincreasedsignificantly.14_CATis mainlylocatedintheperoxisomes,anditiscapableofremoving intracellularH2O2and superoxideradicalswithgreat effica-cy.4,10,15 Salivary levels of CAT were reduced in chronic periodontitispatientswhencomparedtoperiodontallyhealthy subjects.16_{GPxisaselenium-containingperoxidaseresponsible} for the protection of mammalian cells against oxidative

damages byreducting a variety ofhydroperoxides,suchas ROOH and H2O2extracellularly and inthemitochondria.4,17 Additionally,one studyshowedthatgingivalcrevicularfluid from periodontitis patients contained significantly lower amountsofreducedandoxidisedglutathionethanmatched periodontallyhealthysubjects.17

Furthermore, non-enzymaticantioxidantsaresecondary mechanismstoneutraliseROS.4,9,18,19_{Generally,thesetypes} ofantioxidantsareobtainedexogenously,mainlythrougha balanced diet, which included a variety of fruits and vegetables,suchasblueberries,strawberries,grapes,20 avoca-do,21_tomatoes,22_spinach,23_andcarrots.19_{Thenon-enzymatic} antioxidantsarerepresentedbyfat-solublevitamins(vitamin A,vitaminE-tocoferolandb-carotene),water-solublevitamins (vitaminCandvitaminBcomplex),traceelements(zincand magnesium),andbioflavonoids(plantderived).

Studies have demonstrated that, in patients with peri-odontitis,oxidative levelsareincreasedwhencomparedto periodontallyhealthysubjects.24,25_{However,theantioxidant} levelsaresignificantlylowerinchronicperiodontitispatients whencomparedtoperiodontallyhealthyindividuals.17,26–28

Itiswellestablishedthatmosttypesofperiodontitiscanbe successfullytreatedbyremovingthesupra-andsubgingival biofilmbyscalingandrootplaningcombinedwithadequate periodontalsupportmaintenance.29_{Scalingandrootplaning} isalsocapableofdecreasingthe totaloxidantstatusinthe gingivalcrevicularfluidandimprovingtheantioxidantlevels inpatientswithchronicperiodontitis.26,30

Therefore,periodontaldiseasesand reducedantioxidant levels seem to be associated with one another,leading to increasedoxidativedamages intheoral environment.This systematicreviewassessedtheeffectofantioxidantagentsas complimentarytoperiodontaltherapyintermsofoxidative stress/antioxidants.

2.

Methodology

Thefocusedquestionforthissystematicreviewwas:istherea benefitofantioxidantagentscomplimentarilytoperiodontal stressoutcomes didnot follow the same pattern throughoutthe studies. It may be concludedthattheuseofsomeantioxidantshasthepotentialtoimproveperiodontal clinicalparameters.Theroleofantioxidant/oxidativestressparametersneedsfurther investigations.

therapyintermsofperiodontalandoxidative stress/antioxi-dantparameters?

Thesearchforthis systematicreview wasconducted in MEDLINE-Pubmed,Lilacs, and Scielo databases. Thesearch strategy included the following terms: ‘‘periodontitis’’ OR ‘‘chronicperiodontitis’’AND‘‘oxidativestress’’OR ‘‘antioxi-dant’’OR‘‘antioxidant effect’’OR‘‘vitamin’’. Theliterature wassearcheduptoSeptember2014.

Titlesandabstractsresultingfromthesearchasdescribed above were screened. Retrieval of studies was performed whenthetitlesorabstractsfulfilledthefollowingcriteria:

Randomisedclinicaltrial Double-blindorblind

Interventiongroup:studiesthattreated gingivitis/periodon-titis with supragingival plaque control/nonsurgical peri-odontal therapy and administered, complimentarily, antioxidantagentsinoneofthefollowingmanners: Systemically.

Locally.

Throughanytypeofdietintervention.

Controlgroup:studiesthatusedoneofthefollowingcontrol groupswereaccepted:

Aplaceboagentwithnonsurgicalperiodontaltherapy. Nonsurgicalperiodontaltherapyonly.

Absenceofperiodontaltherapy. Healthyperiodontalsubjects.

Nolanguageorpublicationdaterestrictionswereapplied. However,thestudieswereexcludediftheypresentedoneof thefollowingcriteria:

Observationalandexperimentalanimalstudies. Casereports,lettersandreviews.

Includedonlysubjectsyoungerthan18yearsold. Usedexperimentalgingivitisintheirstudydesign. Didnotassessanykindofoxidativestressoutcome.

Studieswithoutabstractsbutwhosetitlessuggestedthat theycouldberelatedtotheobjectiveofthissystematicreview were also selected so the full text could be screened for eligibility. All the references of every selected study were screenedforpossibleeligiblestudiesaswell.

Toreducethepotentialbiasinthereview,screeningwas performed independently by two reviewers (SBN and FWMGM). Any discrepancies with regard to the exclusion and inclusion of the studies were resolved by extensive discussionbetweenthetworeviewers.Ifanydoubtremained, anotherinvestigator(RSC)becameinvolvedintheprocess.

3.

Results

One-thousand one-hundred and fifty-three (1153) titles/ abstracts were retrieved from the search, of which seven were selected based on the criteria previously described (Fig.1).AlloftheselectedstudieswerewritteninEnglish,and themainresultsofthesestudiesareshowninTable1.

Moststudies focused on the use of antioxidants inthe treatmentofchronicperiodontitisinnonsmokers26,31–34_and

onlyonestudyinthetreatmentofgingivitis.32_{Theantioxidant} agentsusedwerevitaminE,34_vitaminC26_{andconcentrated} capsules of fruits/vegetables/berry,31 and lycopene both locally33,35 _{and systemically.}32 _{One study also performed} dietary intervention on anindividual basis toimprove the amountofantioxidantintake.36_{Additionally,twostudiesused} thesplit-mouthintheirexperimentaldesign.32,33_Thisdesign ischaracterisedbyatrialinwhicheachindividualistreatedby atleasttwodifferenttreatmentsinaseparateportionofthe mouth.37_{Therefore,inthisdesign,eachindividualis} consid-ered their own control, as these different therapies may resultsindifferentoutcomes.

Split-mouthdesignisatrialinwhicheachsubjectreceives at leasttwo different treatments ina separate part ofthe mouth.

Thestudythatusedsystemicallyadministeredlycopene wasdevelopedbyChandraetal.,32_{andtheyanalyseditseffect} inthetreatmentofgingivitis.Asplit-mouthdesignwasused with20patientsdiagnosedonlywithgingivitis;10individuals received 8mg lycopene/day systemically for 2 weeks (test group),andtheremaining10subjectsreceivedaplaceboagent (controlgroup).Bothgroupsreceivedoralprophylaxisintwo contralateraloralquadrants,andtheotherquadrantsdidnot receiveanytreatmentatbaseline.After2weeks,allgroups demonstratedstatisticallysignificantreductionsingingivitis, bleeding index and plaque index compared to baseline. Furthermore,sitestreatedwithlycopeneandoralprophylaxis significantly reduced more gingivitis when compared with bothcontrolgroups.Additionally,gingivitispatientswhowere treated onlywithlycopeneshowedagreater improvement comparedwiththegroupthatwastreatedwiththeplacebo only. That study also evaluated the relationship between salivary uric acid levels and the percentage reduction of gingivitis,showingthat,after2weeks,onlythegrouptreated withlycopeneandoralprophylaxisdemonstratedasignificant strongnegativecorrelation.

Lycopenewasalsousedlocallyintwostudies complimen-tarilyforSRP.33,35_{Oneofthesestudiesshowedthat} lycopene-treatedsitespresentedsignificantlyhigherlevelsofprobing depth reduction and more clinical attachment gain when comparedtositestreatedwithplacebogel,despitesmoking habits.35_{Thestudyalsoshowedthatperiodontaltreatment} wascapableofreducingtheserumlevelsof 8-hydroxydeox-yguanosine (8-OHdG), a biomarker of oxidative damage. Additionally,thelycopene-treatedsitesinnonsmokers,when compared tosmokers, benefited morefromthis reduction, achievinglevelsquitesimilartothoseofperiodontalhealthy individuals. Theotherstudy,developedbyChandraetal.,33 used asplit-mouthdesign.Three sitesofall patientswere randomlytreatedwithSRP,placebogelapplicationafterSRP and 2% lycopene gel application after SRP. In that study, lycopene-treated sitespresented significantlymoreprobing depthreductionandclinicalattachmentgainaftersixmonths. Additionally,thelevelsof8-OHdG1weekaftertherapywere statisticallyreducedatlycopene-treatedsiteswhencompared withtheothertwogroups.However,thosedifferenceswereno longerpresentafterthreemonths.

Table1–Mainresultsoftheselectedstudies.

References Follow-up Typesanddoseof antioxidants

applied

Experimentaldesign Mainresults P-value

Chandra etal.32

2weeks Lycopene8mg/day Negativecontrolgroup:

twoquadrantsdidnot receiveany

treatment+placebo

Percentreduction ofgingivalindex frombaselineto 2weeks

Intergroup comparison

Negativecontrol group:11.946.55

Positivecontrol group:18.857.29

Negative controlgroup vs.test group1

<0.01

Positivecontrolgroup:

oralprophylaxisintwo quadrants+placebo

Testgroup 1:24.144.81

Negative controlgroup vs.testgroup2

<_0.01

Testgroup2:

30.027.17

Positivecontrol groupvs.test group2

<0.05

Testgroup1:two quadrantsdidnotreceive anytreatment+lycopene

Relationshipbetween salivaryuricacid levelsandthepercent reductioningingivitis at2weeks(values expressedbyPearson correlation)

Negativecontrol group: 0.126

0.730

Testgroup2:oral prophylaxisintwo quadrants+lycopene

Positivecontrol group: 0.478

0.163

Testgroup1: 0.580 0.079 Allsubjectswere

diagnosedonlywith gingivitis

Testgroup2: 0.802 0.005

Chandra etal.22,35

3months (8-OHdG outcomes)

2%lycopenegel locallyapplied

Controlgroup:healthy periodontalpatients

Controlgroup P-value

not shown PD:1.030.27mm

(baseline) PD:1.100.31mm (6months) 8-OHdG: 1.650.16ng/mL (baseline) 8-OHdG: 1.300.17ng/mL (3months) 6months

(periodontal outcomes)

Smokersgroup:subjects diagnosedwithCPand treatedwith

SRP+placebogel/ lycopenegel

Smokersgroup (lycopene-treated sites)

<0.05

PD:6.211.29mm (baseline) PD:3.500.92mm (6months)

<_0.05

Table1 (Continued)

References Follow-up Typesanddoseof antioxidants

applied

Experimentaldesign Mainresults P-value

Smokersgroup (placebo-treated sites)

<0.05

PD:6.021.49mm (baseline) PD:5.161.52mm (6months)

<_0.05

8-OHdG: 5.661.52ng/mL (baseline) 8-OHdG: 1.460.26ng/mL (3months)

Nonsmokersgroup:

subjectsdiagnosedwith CPandtreatedwith SRP+placebogel/ lycopenegel

Nonsmokersgroup (lycopene-treated sites)

<0.05

PD:6.040.87mm (baseline) PD:3.951.21mm (6months)

<_0.05

8-OHdG: 5.341.14ng/mL (baseline) 8-OHdG: 1.110.28ng/mL (3months) Nonsmokersgroup (placebo-treated sites)

PD:6.311.27mm (baseline) PD:4.811.34mm (6months) 8-OHdG: 5.431.14ng/mL (baseline) 8-OHdG: 1.490.25ng/mL (3months)

Thelevelsof8-OHdG werereducedin everygroupthat receivedSRP

<_0.001

Lycopene-treated sitesreducedeven more8-OHdGlevels, especiallyin nonsmokers

Chandra etal.33

3months (8-OHdG outcomes)

2%lycopenegel locallyapplied

Shamgroup:treatedonly withSRP

PDSDmeansat 6months

Intergroup comparison

6months (periodontal outcomes)

Placebogroup:treated withSRP+placebogel

Shamgroup:

4.921.35mm

Placebogroup:

4.511.22mm

Lycopenegroup:

3.621.04mm

Placebovs. sham Lycopenevs. sham Lycopenevs. placebo

0.430 0.001 0.020

Lycopenegroup:treated with+lycopenegel

8-OHdGlevels at3months

Table1 (Continued)

References Follow-up Typesanddoseof antioxidants

applied

Experimentaldesign Mainresults P-value

Shamgroup:

1.42ng/mL

Placebogroup:

1.52ng/mL

Lycopenegroup:

1.39ng/mL

Placebovs. sham Lycopenevs. sham Lycopenevs. placebo

0.460 0.930 0.277

Abou Sulaiman and Shehadeh26

1month (TAOC outcomes)

VitaminC2000mg/ day

Controlgroup:healthy periodontalsubjects

TAOClevels1 monthafter periodontaltherapy:

3months (periodontal outcomes)

Testgroup1:subjects diagnosedwithCPand treatedwith

SRP+vitaminC

Controlgroup:

62588.7mm Teq(baseline)

Testgroup1:

655.843.2mm Teq

Testgroup2:

651.463.3mm Teq

>_0.05

(between all groups)

MeanofPD3 monthsafter periodontaltherapy

Testgroup2:subjects diagnosedwithCPand treatedonlywithSRP

Controlgroup:

notshown

Testgroup1:

2.880.48mm

Testgroup2:

3.070.61mm

0.329 (between testgroup 1and2)

ZareJavid etal.36

6months Customiseddietary intervention

Controlgroup:treated onlywithSRP

TAOCmeanand 95%CIat6months

Controlgroup:

1.23(1.18;1.26)

0.02

Testgroup:treatedwith SRP+dietaryintervention

Testgroup:1.31 (1.23;1.39) Nostatistical differencewas foundinthe periodontal outcomes(data notshown)

Chapple etal.31

8months CapsulesFV(4 fruits/vegetables capsules+2placebo capsulesfor9 months)

Controlgroup:onlySRP ThetestgroupFV showedstatistically significantgreater reductioninPD whencomparedto thecontrolgroup2 monthsafter therapy

<0.03

CapsulesofFVB(6 fruits/vegetables/ berrycapsulesfor9 months)

TestgroupFV:

SRP+capsulesFV

At5-and8-months evaluation,that differencewasno longerstatistically significant

>_0.05

TestgroupFVB:

SRP+capsulesFVB

Additionally,thePD reduction,intest groupFVB,wasnot statisticallydifferent fromcontrolgroup atanytime

only in half of this sample was vitamin C systemically administered in a 2000mg dose per day for 4 weeks. The totalantioxidantcapacity(TAOC)ofplasmawasevaluatedat baselineand1monthafterSRP.Complimentaryuseofvitamin CdidnotpromoteanyadditionalimprovementintheTAOC levelsandinperiodontalparameters3monthsaftertherapy. However,periodontaltherapyitselfwassufficienttoimprove theTAOClevels.

The impact of customised dietary intervention was verified by Zare Javid et al.36 _{in 51 chronic periodontitis} patients.Thecustomiseddietaryinterventionwasperformed toincreasethehabitofeatingfruits,vegetablesandwhole grainsinanattempttoimprovetheantioxidantstatus.Inthat study,onegroupreceivedonlySRPandgeneralnutritional considerations (control group), while the other group re-ceivedSRP,aone-to-onesessionwithacommunitynutrition assistantandapersonalisedpackagewithdietary interven-tions(testgroup).Thelevels oftotalapparentantioxidant capacityinplasma,assessed byTroloxequivalent antioxi-dantcapacity,showedthatthetestgrouppresented signifi-cantlyhigherlevelsofantioxidantcapacitythanthecontrol group.However,thedifferentperiodontaloutcomesdidnot demonstrate statistically significant differences in both

groups. Furthermore, it is important tohighlight that the periodontalparameters(bleedingindex)remainedunaltered inbothgroupsduringtheentirestudy.

Chappleetal.31investigatedtheadjunctiveeffectofdaily supplementationwithencapsulatedfruit,vegetableandberry juicepowderconcentratedinclinicalperiodontalparameters. Sixty chronic periodontitispatients weredivided into three groups,withonereceivingonlySRP (controlgroup),andthe other receiving SRP, four fruit/vegetable capsules and two placebocapsulesfor9months(FVgroup),andanothergroup receivedSRPandsixcapsules,containingfruit/vegetable/berry juicepowderconcentrationsfor9months(FVBgroup). Two months after periodontal therapy, the FV group showed significantlygreaterprobingdepthreductionwhencompared tothecontrolgroup.Thisdifferencewasnolongerstatistically significantafter5months.RegardingtheFVBgroup,theresults werestatisticallyequaltothoseofthecontrolgroupandFV group at all experimental times. Despite the absence of differences intheperiodontaloutcomeswithlonger follow-up,theserumb-carotenelevelswereincreasedsignificantlyin boththeFVandFVBgroupsincomparisonwiththeplacebo group.Surprisingly, thehighestlevelswerefoundintheFV group,even8monthsaftertherapy.

Table1 (Continued)

References Follow-up Typesanddoseof antioxidants

applied

Experimentaldesign Mainresults P-value

Singh etal.34

3months VitaminE200mg everyotherday

Controlgroup:healthy periodontalsubjects

Median(minimum; maximum)PDvalues

<0.05

(between test group1 andtest group2)

Controlgroup:1.19 (0.17;2.18)mmat baseline

Testgroup1:2.06 (1.12;3.03)mmat 3months

Testgroup2:1.85 (1.14;2.98)mmat 3months

Testgroup1:subjects diagnosedwithCPand treatedonlywithSRP

Median(minimum; maximum)of serumSODactivity

<0.05

(between test group1 andtest group2)

Testgroup2:subjects diagnosedwithCPand treatedwith

SRP+vitaminE

Controlgroup:69.36 (53.85;91.31)%

Testgroup1:62.06 (55.19;90.92)%

Testgroup2:85.90 (49.06;95.63)%

Singhetal.34_{evaluatedtheeffectofvitaminE,} complimen-tarilytoSRP,inperiodontalandSOD outcomes.Thisstudy used38patientsdividedintotwogroups:onegroupreceived onlySRP,andtheotherwastreatedwithSRPandvitaminE 200mg(300IU)everyotherday.Itwasfoundthatthegroup that receivedSRP and vitaminEdemonstrated statistically significant improvements in all periodontal parameters analyzed, which included plaque index, probing depth, clinicalattachmentlevel,and bleedingonprobing. Further-more,the serum SOD activitywas significantlyelevated in bothSRP-treated groups. However, inthe vitaminEgroup, when compared with the control group, the increase was statisticallysignificant,achievinglevelssimilartoperiodontal healthysubjects.

4.

Discussion

Thepresentsystematicreviewwasaimedatunderstanding the optimal use ofantioxidants asadjuncts toperiodontal therapy.Theresultsofthereviewmayhaverelevanceforthe developmentoftreatmentprotocols.

Theselectedstudiesforthissystemicreviewhaddiverse study designs with follow-ups ranging from 2 weeks to 8 months; those studies were mainly focused on treating chronicperiodontitis.Theantioxidantusedandthe antioxi-dant/oxidativestressoutcomemeasuredalsovariedineach study.Thishighdegreeofvariationinmethods,aswellasthe heterogeneity in results, prevented using a meta-analytic approach. Therefore, direct extrapolations of the results shouldbemadewithextremecaution.

Oxidativestressisaphysiologicalconditionthat,inlow levels, can somehow be beneficial for the host, as it can

stimulatethegrowthofepithelialcellsandfibroblastsandkill some bacteria. However, oxidative stress can cause tissue damageasaconsequenceoftheabnormalincreaseinreactive oxygen species(ROS).10,38_{Neurodegenerative, inflammatory} diseases, cancer, nutritional deficiency, diabetes and some psychiatricdisordersmaybeinvolvedwithabnormal produc-tion of ROS.39,40 _{Additionally, the mechanisms of tissue} damage caused by ROS have been used to explain the relationshipbetweenperiodontitisandavarietyofsystemic diseases,suchasdiabetes,41_{mitochondrialdysfunction,}42_and metabolicsyndrome.43_{Intheperiodontium,different} biologi-calmechanismsareresponsiblefortheincreaseinROSlevels, such as neutrophil infiltration, fibroblasts, osteoclasts and endothelialcells,whichresultsinbreakdownoftheepithelial structureanddamagetotheconnectivetissuesintheadjacent areas.25,44,45 _{Additionally, an in vitro study showed that}

Fusobacteriumnucleatum,aperiodontopathogenicgram nega-tive bacterium, was able to stimulate ROSproduction and inducelipidperoxidation.46

AbnormalROSproduction can leadtophysiologicaland pathologicalconsequencesofhypoxia,impairmentofaerobic function, lysis of the cell membrane, DNA fragmentation, ischaemicinjury, inactivationofcertainproteolyticenzyme inhibitors, activation of proteolytic enzymes and, more drastically, cell death.42,47 These events might result in collagenolysisanddegradationofspecificextracellularmatrix components, such as hyaluronic acid and proteoglycans,47 whichcanpartiallyexplaintheetiopathogenesisof periodon-titis.

Antioxidantsexistineverybodyfluidandtissue,protecting against the damages of ROS.48 _{Antioxidants act against} oxidative damagebydirectlyscavenging ROSandrepairing the damage caused by these harmful agents. In addition,

antioxidants act through down-regulation of some redox-sensitivepro-inflammatorygenetranscriptionfactorsand,at the same time, they regulate the anti-inflammatory gene transcription factors.4,48 _{Uricacid isthe mostpredominant} antioxidantinsaliva,49_{anditslevelswillvaryaccordingtothe} degree of saliva stimulation.17 _{The uric acid antioxidant} activityincludesscavengingofsingletoxygenandhydroxyl radicals.4Thesecharacteristicsmayexplainwhyuricacidwas negativelycorrelatedwithreductionofgingivitisinoneofthe selected studies that used lycopene complimentarily to gingivitistreatment.32

Accordingtotheliterature,oneofthemostcommonlyused assaysformeasuringoxidativestressdamageis8-hydroxy-20 -deoxyguanosine(8-OHdG),whichisamarkerofDNAdamage derived from conversion of guanine to 8-hydroxyguanine, assessed by an enzyme linked immunosorbent assay (ELISA).25,50_{The levelsof8-OHdG insaliva wasfound tobe} higherinsubjectswithchronicperiodontitiscomparedwith periodontallyhealthycontrols,24showingthat8-OHdG corre-lates reliably with the increase of ROS production during periodontalinflammation.Therefore,thisbiomarkerisreliable for evaluatingtheefficacy ofantioxidantson oxidantstress studies.51_{Twooftheselectedstudiesevaluatedtheeffectof} complimentaryuseoflocallydeliveredlycopeneinperiodontal outcomes and also in the 8-OHdG levels.33,35 Both studies showedthatthreemonthsafterSRP,thelevelsof8-OHdGwere reduced in all sites. That decrease was significantly more pronounced in the sites that were treated with SRP and lycopene. However, in one ofthese studies, that difference wasobservedonlyoneweekaftertherapy,anditdisappeared afterthreemonths.33_{LocallydeliveredlycopeneandSRPwere} alsorelatedtosignificantimprovementsinprobingdepthand clinical attachment levels in both studies. Lycopene, the carotenoidthatgives ripetomatoesabrightredcolour,isa naturalnon-enzymatic antioxidant thatexhibitsthehighest physicalquenchingratewith singlet oxygen.52_Furthermore, lycopenealsoprotectsagainstDNAdamageinducedbyH2O2,53 decreasesthelevelsofgingivitis32_{andmayexertinhibitionon} bacterial colonisation.54,55 _{All of these characteristics may} explain the promising results from the studies that used lycopenecomplimentarily toSRP.However, theeffect ofan antioxidantagentin8-OHdGlevelsremainsunclear,andfurther studieswithdifferentantioxidantsshouldbeperformed.

Analysisoftotalantioxidantcapacity(TAOC)isthemost reliableoxidativestressoutcometoassesstheincapacityof antioxidantstoneutraliseROSandotherfreeradicals.56Two ofthe selected studies assessed TAOC using vitamin C or customiseddietaryinterventioncomplimentarilyto periodon-taltreatment.26,36_{ThestudythatusedvitaminCshowedthat} SRP was capable of increasing TAOC levels, which was accompaniedbyimprovementinperiodontalindices,despite theappliedcomplimentarytherapy.However,thestudythat intended to increase the intake of antioxidants through customised dietary intervention showed that TAOC levels weresignificantlyincreasedafterthecomplimentarytherapy. Ontheotherhand,theimprovementsinperiodontalindices didnotreachstatisticallysignificantdifferencesamongthe testgroupandthegroupthatreceivedonlySRP.

Vitamin C(ascorbic acid) is anessential component of everylivingcell,anditsreducedusageisassociatedwithpoor

immunefunction.57_{Incontrast,higherintakeofvitaminCis} associated with antiviral resistance and anti-carcinogenic effects and several other immune function improve-ments.58,59_{TheuseofvitaminCisassociatedwith} stimula-tion of collagen fibre production andimmunomodulation functions, suchassignificant decreasesinserumlevelsof lipid peroxides andenhanced phagocytosis functions.59–61 Despite the benefits associated with vitamin C intake, significant improvements in periodontal indices were not demonstrated.Thisoutcomemightbebecauseascorbicacid actions in periodontal tissues are limited or because the optimal levelsofintakerequiredtomaintainanimproved immuneresponsetotreatorpreventinfectiousdiseaseshave notbeenassessed.59

Theingestionoffruits,vegetables,wholegrainproducts andalsolowerintakeoffoodwithsaturatedfatsandsugars arethefoundationofahealthyandbalanceddiet.62_Intwoof the selected studies, the increased intake of fruits and vegetables, otherwise known as antioxidants agents, was obtained through individualised dietary intervention36 _or through administration of capsules containing b-carotene, vitamin E, vitamin C and folic acid.31 _{It is known that b} -carotene isefficientatscavenging singletoxygen,63_{and its} levels aresignificantlylowerinperiodontitispatientswhen comparedtocontrolsubjects.64However,theanalysesfrom the selected studies showed that both types of dietary interventiondidnotpromoteadditionalperiodontal improve-mentslong-term,despiteitsbeneficialeffectsonantioxidant biomarkers(i.e.,b-caroteneandTAOC).

VitaminEisthemajorfat-solubleantioxidantpresentinall cellmembranes,anditreducesthelevelsoffreeradicalsand alsoexertssomeanti-inflammatorypropertieswith improve-mentsinthehumoralimmuneresponse.65–67_{Thisvitaminis} essentialfornormalreproductioninhumans,developmentof muscles and a variety of physiological and biochemical functions.Inoneoftheselectedstudies,vitaminEwasused complimentarily to SRP. The group that received both therapiesshowedsignificantimprovementsinallperiodontal parameterswhencomparedtothegroupthatreceivedonly SRP.34_{Thedifferenceswerealsofollowedbyimprovementsin} theSODactivityinseruminthetestgroup.Thepotential anti-inflammatoryeffectofvitaminEmaybeduetoitsinhibitionof prostaglandinbiosynthesis,68_{suppressionoftheproductionof} proinflammatorycytokines,69_{adecreaseinC-reactiveprotein} levels69_{andpreventionofactivationofnuclearfactor}

kBby free radicals.69,70 Despite the significantly different results obtainedbySinghetal.,34_{itisimportanttohighlightthatthe} meandifferencesbetweencontrolandtestgroupsweresmall andmightnothaveanyclinicalimpact.Additionally,vitamin E isknowntoinduceanxietyinratswithligature-induced periodontitis.71_{Therefore,theseconditionsshouldbe} consid-eredbeforethecomplimentaryuseofvitaminEinperiodontal treatment.

5.

Conclusions

Thissystematicreviewsuggestedthatuseofanantioxidant, complimentary treatment for periodontal disease has the potentialtoimproveperiodontalclinicalparameters. Howev-er,theimpactofthecombinationofperiodontaltherapywith antioxidantsintermsofantioxidant/oxidativestress param-etersrequiresfurtherinvestigation.

Authors’

contribution

F.W.M.G. Muniz selected the studies, extracted the data, analyzedthedataandwrotethemanuscript.S.B.Nogueira selectedthestudies,extractedthe data,analyzedthedata and wrote the manuscript. F.L.V. Mendes reviewed the manuscriptandhelpedwiththeliteraturereviewanddata analysis. C.K.Ro¨singreviewedthe manuscriptandhelped with the literature review and data analysis. M.M.S.M. Moreira reviewed the manuscript and helped with the literature review, data analysis and search strategy. G.M. de Andrade reviewed the manuscript and helped data analysis. R.D.S. Carvalho developed the review protocol, reviewed the manuscript and helped with the literature review,dataanalysisandsearchstrategy.Shealsohelpedin theselectionofthestudies.

Funding

None.

Competing

interests

Nonedeclared.

Ethical

approval

Notrequired.

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