faculty of research report faculty of 08/09 dentistry 2010/nus dentistry... · 2 faculty research...

Faculty ofResearch Report

08/09Faculty of

Dentistry

Contents1 Foreword

2 FacultyResearchStrategy

3 StrategicResearchInitiatives

7 GraduateResearchProgrammes

8 GraduateCourseworkProgrammes

10 UndergraduateResearchOpportunitiesProgramme(UROP)

12 ResearchHighlights

17 CompletedResearchProjectsinFY2008/09

26 NewResearchProjectsAwardedforFundinginFY2008/09

33 ResearchCollaborations

34 ResearchAchievements

35 ResearchStatistics

Faculty of Dentistry Research Report 08/09

1Research Report 08/09Faculty of Dentistry

Researchvibrancyis integralforaninstitution’ssustainablegrowthanddevelopment.While thepast twoyearshavewitnessedinfrastructuralconsolidation,AcademicYear2008/09waswheneffortwasfocusedonemergingareasofresearchengagementandmulti-disciplinarycollaboration.

Thesettingupofastate-of-the-artFluorideLaboratoryaswellastheestablishmentofanOralBiofilmAnalysisfacilityincollaborationwiththeUniversityofOtago,undertheCraniofacialClinicalResearchUnit(CCRU)/DentalBiophotonics&BiomaterialsProgramme(DBBP)ResearchInitiativeswillfacilitatethestudyofadiversespectrumofbacteriaandyeasts,andpromisestobringtheFacultytoanotherintellectualparadigm.TheOralTissueRepositoryundertheCentreforCraniofacial&RegenerativeBiology(CCRB)hassupportedthemaidenstepsinthestudyofethicallylesscontroversial,dentalpulpstemcells,whichholdsupthepotentialofbridgingDentistrywithotherlife-sciencerelatedplatforms.

Thepursuitofacademicexcellencewouldonlybepossibleifexistingstrengthsarecapitalizedupon,coupledwithcontinualrecruitmentofglobalresearchtalent.TheFacultyhasprovidedanenginereadytobedriven,workinginconcerttocreateanincubatorthatwouldempowerustotakeontheincreasingresearchchallengesthatareemerging.

CitingArthurSchopenhauer“…thegreatestamountofknowledge,ifnot

elaboratedbyourownthoughts,isworthmuchlessthanafarsmaller

volumethathasbeenabundantlyandrepeatedlythoughtover.”.Excellence

isnotaboutcapacity,it’saboutmindpower.TheFaculty’sresearchenterprise

maybesmall,butifweperseverepositively,wecanmakeanimpact.

AssociateProfessorVarawanSae-LimViceDean(Research)

Foreword

Foreword

Faculty of Dentistry 2 Research Report 08/09

ToimproveOral,DentalandCraniofacialHealthandtheDeliveryofClinicalCare

Faculty Research Strategy

Faculty VisionTobeaDentalInstitutionofInternationalDistinction

Strategic Research Initiatives

Centre for Craniofacial Regenerative Biology (CCRB)

Dental Biophotonics and Biomaterials Programme (DBBP)

Faculty Mission

Research Mission

ToimproveOralHealththroughAcademicExcellence,HighImpactResearchandQualityClinicalService

Craniofacial Clinical Research Unit (CCRU)

Faculty Research Strategy


The Centre for Craniofacial and Regenerative Biology (CCRB)Contributed by Ag. Director Assoc Prof Yeo Jin Fei

Overview:Intheacademicsessionreviewed,besidesfacilitatingestablishedresearchprogrammeslikeembryonicstemcellresearchandorofacialpainresearch,CCRBispleasedtoreportthecompletionofthesetupofkeyinfrastructureandcapability,i.e.‘OralTissueDepository[OTR]’whichisessentialtonurturebuddingresearchthatharnessoraltissue-derivedadultstemcells.Withtheacquisitionofthiscapabilityofdentalpulpstemcell,CCRBaimstoadvancecell-basedresearchexploitableincraniofacialtissueregenerationandothertranslationalmedicalresearchentities.TheCCRB-OTRwillthereforepositiontheFoDintheresearchforefrontofthisglobalresearcharena.

Progress in FY 2008/09:TheOralTissueRepository,whichisestablishedasacoreresearchfacilityfollowingtheapprovalofInstitutionalReviewBoard,starteditsinitialoperationbysettingupallthebasicequipmentsandconsumablesrequiredfortissuecollectionandbanking.TheOTR–PatientInformationandConsentform,requiredfortheworkflow,wasrevisedandhadreceivedapprovalfromIRB.OtherOTRformsinclude:

1. OTRDataCollectionForm2. OTRLaboratoryInformationSheet3. OTRInterimsheet4. OTRParticipantContactinformationsheet

AbriefworkflowfortheoperationsofOTRwasintroducedstartingfromtakingpatient’sconsenttocollectionofspecimenfromtheNUHOperationTheatre.Asuccessfultrialrunwascompletedforthecollectionofafewspecimensi.e.thefirstthreetobecollected.Atpresent,OTRisfunctioningsuccessfullywithafewtoothspecimensinstore.Apilotstudyisbeingimplementedonisolationandcryopreservationofdentalpulpcellsfromhealthywisdomteeth.Infuture,weanticipatecollectingandcryopreservinggingivalandPeriodontalligamentcellsalongwithnon-wisdomtoothspecimens.Intheyearunderreview,CCRBhassecuredthreeAcademicResearchFund(AcRF)researchandonestart-upgrant(withatotalgrantamountofS$580,560)andanotherexternalcollaborationgrantwithSIMTechamountingtoS$88,7859.Dr.LiuHuaintheresearchteamunderAPCaoTongwon“TheChinaScholarshipCouncilAward”withaprizemoneyofUS$5000.APCaoTongtogetherwithProfessorYuGuang-yanofPekingUniversityPRCsecuredanInternationalCollaborationgrantamountforRMB2,570000fromtheMinistryofScienceandTechnology,PRC.CCRBthroughitsresearchteamsunderAPCaoTong&APYeoJinFeipublishedfourfull-lengthpapersinpremierjournals.



The Dental Biophotonics and Biomaterials Programme (DBBP)Contributed by Director: Assoc Prof Stephen Hsu

Overview:Progress in FY 2008/09:ThisyearthemembersofDBBPhaveobtainedtwoAcademicResearchFund(AcRF)research,onestart-upgrantandoneexternalgrant(withatotalofS$427,414.47),13articles(withninepublishedinthepremierjournals)andtworegionalresearchawards.Thethematicprogressissummarizedbelow:

Tooth-biofilm Interaction: • Dr.Anil’sgroupsuccessfullypublishedtwoarticlesinpremierjournals.Theteam

hasleveragedonthehighintensityfocusedultrasoundtodeliverantibacterialnanoparticlesintodentaltubules.OneUROPstudentteamutilizedtheLightActivatedDisinfection(LAD),withMBinemulsion(PF4),togeneratesinglet-oxygenfordestructionofbiofilmbacteria.Thestudentresearchteamwonanawardinthe2008IADR-SEAManilameetingandpublishedtheirarticleinareputablejournal.

• Anotherundergraduateresearchteam,supervisedbyA/PHsu,challengedthe“textbooktruth”anddemonstratedthecariostaticpotentialofanacidicdrinkcontainingsucrose,glucose,andlactobacillus(Yakult™,pH=3.65).Thisclinicaltrial,drivenbyacounter-intuitivehypothesis,wonthemtheBestPaperAwardinthe2008“GCAsia-SEAADEStudentPreventionProgramCompetition”.Theirresultshavepavedthewaytosecurearesearchgrantfurtheringtheirworktopreventwhitespotlesionsaroundorthodonticbrackets.

Laser-tissue interaction:• Dr.Anil’s teampublishedanarticleaugmentingantibacterialefficacyof

AdvancedNon-InvasiveLightActivateddisinfection,inadditiontotheirsuccessinmonitoringcompositionalchangesduringdentindemineralizationemployingElectronicImpedanceBasedSpectroscopy.

• A/PHsu’steaminvestigatedthe“maskingeffects”ofsalivaonlaser/heat-inducedphysicochemicalchangesinenamel,whichisacriticalissueforclinicallaserapplicationoncariesprevention.

Bio-imaging research: • A/PKelvinFoong’steamcontinuedbuilding3-Dstatisticalmodelstoprofiletooth

andhumanfaceusinglaserimagingmodalities,MRI,andconebeamCT.TheteampublishedtwoarticlesusingMRItoconductquantitativeanalysisonhumanmasticatorymuscles.

• A/PHsu’steamemployedthe2ndand3rdharmonicgenerationmicroscopyto characterize the crystalline lattice structures of pathological enamelhydroxyapatite.



The Dental Biophotonics and Biomaterials Programme (DBBP) cont’d

Biomaterial Research:• A/PKesonTan’sgrouppublishedthreepremierjournalarticlesinvestigating

osseointegrationandimplantstabilityusingfiniteelementanalysisandaneuralnetwork.Healsosecuredagrantinvestigatingthe3-Daccuracyofplastictransferimpressioncopingsforthreeimplantsystems.

• Dr.ClarisseNg launchedher start-upgrant to studybio-mimetic surfacemodification.

• A/PNgoutilizedhisstart-upgranttoworkonthemechanismsinvolvedintheremineralizationofpartiallydemineralizeddentineinthepresenceofglass-ionomer.


Craniofacial Clinical Research Unit (CCRU)Contributed by Director: Assoc Prof Jennifer Neo

Overview:Intheyearofreview,twoARFandtwostart-upgrants(totalingS$534,460)wereobtained.Fourarticleswerepublished,twoofwhichwereinpremierjournals.Theprogressissummarizedbelow:

Fluoride StudiesTheunitalsoestablishedastate-of-theartfluoridelaboratory(IonChromatography)whichwillbeusedtosupportprojectswhichincludethedetectionoffluorideinfluoridatedsalt,fluoridatedtoothpaste,fingernailsamplesandbabymilkformulae.

Caries Risk Assessment (CRA)A/PStephenHsu’sresearchteamhascarriedoutthefirstofitskindcommunity-basednation-widesurveytoassessthecariesriskamongpreschoolersinSingapore.Atotalof1,782preschoolerswererandomlyselectedfororalexamination,salivarytests,andquestionnairesurvey.ThestudyestablishedbiophysiologicalCRAmodelswhichcouldbeusefulforearlydetectionofcariesinchildrenandearlyinterventionwithcost-effectivecariespreventionprograminthecommunity.Intheclinic,itcanbeutilizedforevidence-baseddiagnosisandtreatmentplanning.

Studies in the pipeline include the following• Theimpactoforalhealthonthedailyperformanceofinstitutionalizedelderly

Singaporeans–apilotstudy• Evaluationofcariesriskassessmentmodelsamongindividualsundergoingmulti-

brackettherapy(fixedorthodonticappliance)• Identifyingriskofexacerbationofasymptomaticpersistentendodonticlesions

(APEL)andbuildingariskassessmentmodelforevidence-basedmanagement• Real-time computationmodels for determining the centreof resistance

forOrthodontics


Research Funding in FY 2008/09

Research Publication in AY 2008/09

$500,000

$400,000

$300,000

$200,000

$100,000

$0

C C R B D B B P C C R U

Research Units

Am

ou

nt

of

fun

din

g (

SGD

)

$427,414,47

14

12

10

8

6

4

2

0

C C R B D B B P C C R U

Research Units

No

. of

pap

ers

Premium

Leading

TotalReputable

Others

$338,629.42

0 0 00

$400,700 $400,700

Total

External Funding

NUS Funding

5

2 2

0

9 9

2

1

2 2

0 0

1

13

4


$88,785


List of Conferred MSc and PhD Students in AY 2008/09

Name Main Supervisor Degree Nationality Thesis Title

Annie Shrestha A/P Anil Kishen M.SC. Nepal Chairside Optical Sensor to Monitor Bacterial - Mediated Acidogenic - Profile of Saliva in Children

Md Nazrul Islam

Dr. Victor Fan M.SC. India Radiograhic assessment of bone regeneration in alveolar sockets with PLGA bioscaffold after teeth extraction

Shibi Mathew A/P Anil Kishen M.SC. Indian Enterococcus Faecalis Biofim Mediated Inflammatory Potential

Khoo Suan Phaik

A/P Adrian Yap PH.D. Malaysian Biopsychosocial characteristics as predictors of treatment outcome of TMD patients with symptoms of pain

Graduate Research Programmes


List of Conferred MDS Students in AY 2008/09

Endodontics

Student NameLim Siow HooiIntakeAY2006/07

Main Supervisor/ Co-Sup(s)A/P Varawan Sae-Lim Dr. George YipCl A/P Chen Nah Nah

Research TitleIL-6 Expression Following Delayed ToothReplantation in a Canine Model

Student NameNg Yuk ChingIntakeAY2006/07

Main Supervisor/ Co-Sup(s)A/P Varawan Sae-Lim Dr. George YipCl A/P Chen Nah Nah

Research TitleIL-8 Expression Following Delayed ToothReplantation in a Canine Model

OMS

Student NamePoh Hze-Khoong,EugeneIntakeAY2006/07

Main Supervisor/ Co-Sup(s)Dr. Khoo See MengAdj A/P Adrian YapDr. Chan Yiong HuakA/P Yeo Jin Fei

Research TitleA Clinical Prediction Rule for ObstructionSleep Apnea

Student NameWee Tze HaurIntakeAY2006/07

Main Supervisor/ Co-Sup(s)Dr. Poon Choy YokeA/P Yeo Jin Fei Dr. Andrew Tay

Research TitleNeurosensory Distrubance FollowingMandibular Setback Surgery Using BilateralSagittal Split Osteotomy: A Pilot Study of 10Patients

Student NameNorhisham Bin MohamedIntakeAY2006/07

Main Supervisor/ Co-Sup(s)A/P Yeo Jin FeiDr. Aidan YeoDr. Chan Yiong Huak

Research TitleSurgical Complications Following MandibularThird Molar Removal: A ComparativeRetrospective study between the Young andMatured Population

Orthodontics

Student NameChan Feng Yi

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)Dr. Soh JenDr. Chew Ming TakDr. Chan Yiong HuakA/Prof Kelvin Foong

Research TitleOrthodontics and Quality of Health: A Patient-Centered Evaluation

Student NameChong Canon

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)A/P Kelvin FoongDr. Goh Poh SunA/P Ho Yew KeeA/P Ong Sim HengDr. Chan Yiong Huak

Research TitleComputed Tomographic Scanning of Plaster Models – A Study of Validity and Cost Benefit

Student NameLow Hwee Hiang

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)Prof Murray MeikleA/P Cao TongA/P Kelvin Foong

Research TitleThe development of a new in vitro model to study the effects of comprehensive mechanical strain on human periodontal ligament cells

Student NameKoh Poh Leong, Kelvin

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)Dr. Soh JenDr. Chan Yiong Huak A/P Kelvin Foong

Research TitleA Patient-Centred Perspective of Facial Profile Aesthetics

Graduate Coursework Programmes


List of Conferred MDS Students in AY 2008/09 (cont’d)

Periodontology

Student NameNg Cher Hui, Mervyn

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)Dr. Marianne OngA/P Lim Lum Peng Dr. Koh Chu GuanDr. Chan Yiong Huak

Research TitleTooth Loss & Patient Compliance in Periodontally Treated Patients: A Retrospective Analysis 7 Years or More AfterActive Periodontal Treatment

Student NameYap Kin Wai

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)A/P Lim Lum PengDr. Madeliene GunaratnamDr. Chan Yiong Huak

Research TitleSelf Reported Periodontal Disease and Periodontal Health Status in Adults in a Hospital and Private Practise Setting

Orthodontics

Student NameTan Ching Ching

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)A/P Kelvin FoongProf Toshio DeguchiDr. Chew Ming TakA/Prof Ong Sim HengDr. Chan Yiong Huak

Research TitleThree-Dimensional Smile Arc Analysis in Orthodontically Treated Class III Malocclusion Patients

Student NameWong Liping, Florence

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)A/P Kelvin FoongProf Toshio Deguchi Dr. Arthur LimDr. Chan Yiong Huak

Research TitleReliability of the 3dMDface Stereophotogrammetric System: Towards Developing an Industry Standard for Reliability Testing of Surface Imaging Devices

Prosthodontics

Student NameChan Wee Kiong

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)A/P Keson Tan Dr. Ansgar ChengDr. Wong Keng Mun

Research TitleInterface Fit Accuracy of 3 Implant-Conical Abutment Systems

Student NameLim Sze Kheng

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)A/P Hien Chi NgoA/P Keson Tan Dr. Anil Kishen

Research TitleAnti-Bacterial Property of An Electroplated Dental Casting Alloys

Student NameSee Toh Yoong Liang

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)A/P Keson TanCl A/P Chua Ee KiamDr. Quek Heng Chuan

Research TitleLoad Fatigue Performance Conical Implant Abutment Combinations

Student NameSng Hong Cheong, Jeffrey

IntakeAY2006/07

Main Supervisor/ Co-Sup(s)Prof Chew Chong LinCl A/P Chua Ee KiamDr. Teoh Khim Hean A/P Keson Tan

Research TitleBond Strength of Repaired Zirconium Ceramic Crowns

Graduate Coursework Programmes


Undergraduate Research Opportunities Programme (UROP)

Group No. : 07-01 Group No. : 07-02

Pain Reduction Following Third Molar Surgery with 830nm GaA1As Low Level Laser Therapy of Energy Densities 50 & 100 J/cm2

Group membersZhou Shicai, Chua Chew Kiat Simon Jude Chan Pei Yuan Song Yi Lin Luo Wenyuan

SupervisorsProf Loh Hong Sai A/P Yeo Jin Fei

3D Digitisation of Plaster models Using Computed Tomography- A Pilot Work on the Accuracy and Validation of the Approach

Group membersMelvin Liew Kang Ming Ng Jing Hao Hoo Swee TiangTan Jiunn Ming Gary Ode Wataru See-Toh Kai Mun

SupervisorsA/P Kelvin Foong A/P Keng Siong Beng


Advanced Non-invasive Light Activated Disinfection (ANILAD) : An alternative to caries removal by hand instrumentation for deep occlusal caries?

Group membersTan Hui Xian Melissa Cai Xingni Esther Ogawa Chong May May Gomes Mario Regino Wenliang SupervisorsA/P Anil Kishen A/P Jennifer Neo

A 3D Interactive and Visualisation Educational Platform in Oral Histopathology

Group membersZhuang Ronglin Lim Min Min Low Minhui Lu Zhiyin Yim Shao’en Joey Emilia Balasubramanian Suraj

SupervisorsA/P Yeo Jin FeiA/P Kelvin Foong A/P Keng Siong Beng


Cytotoxicity Testing of Hemostatic Agents, Bonewax and Surgicel, on CRL-1486 Cells

Group membersLeonardo Saigo Chew Qin’An Amelia Kwan Yi Alexia Chan Wai Seng Ong Guo An Sia Kia Suan Priscilla

SupervisorsA/P Cao TongA/P Yeo Jin Fei

Fibre Post : Does Fit or Different Post Space Cleaning Methods Affect Retention ?

Group membersTan Jun Da Joanne Ou Jiazhen Tang Hui Yun Marian Elizabeth Ho Swee Ferng Cindy Tan Wye Lynn Tan Hui Lu Shella

SupervisorDr. Lim Kian Chong



Faculty Research Day 2008


ThepurposeoftheUndergraduateResearchOpportunities Programme (UROP) was topromoteanddevelopresearchinterestineveryundergraduate student within the Faculty.Italsoenabledstudentsandfacultymemberstointeractsoastofostertiesinperformingtheresearchworkandprovidingtheopportunitytoacquireskillsfortheintellectualprocessofinquiry.Studentsworkedingroupsunderthesupervisionandguidanceofaresearchmentortoexploreresearchideasandtesthypotheses.

TheprogrammecommencedinYear2Term3andlastedforabout2years.Afinalresearchreporthastobesubmittedattheendoftheprogramme and selected groups will thenpresenttheirresearchfindingsduringtheFacultyResearchDay.FacultyResearchDay2008washeldon7Nov2008andatotalofsixgroupspresentedtheirfindingstoapanelofjudgescomprisingProfToshioDeguchi,ProfMurrayClydeMeikleandAssocProfStephenHsu.

The results of the competition were as follows:

StartingfromLeft:MrTokWeeWah,A/PKengSiongBeng,See-TohKaiMun,HooSweeTiang,TanJiunnMingGary,Ode

Wataru,NgJingHao,MelvinLiewKangMingandA/PKelvinFoong

StartingfromLeft:A/PJenniferNeo,CaiXingni,ChongMayMay,EstherOgawa,TanHuiXianMelissaandA/PAnilKishen

(Notinphoto:GomesMarioReginoWenliang)

StartingfromLeft:TanJunDa,JoanneOuJiazhen,TangHuiYunMarianElizabeth,TanHuiLuShella,HoSweeFerng

Cindy,TanWyeLynnandDr.LimKianChong

Winning Group - Group 2 (07-02)

Project Title3D Digitisation of Plaster models Using Computed Tomography-A Pilot Work on the Accuracy and Validation of the Approach

1st Runner Up - Group 3 (07-03)

Project TitleAdvanced Non-invasive Light Activated Disinfection (ANILAD) : An alternative to caries removal by hand instrumentation for deep occlusal caries?

2nd Runner Up - Group 6 (07-06)

Project TitleFibre Post : Does Fit or Different Post Space Cleaning Methods Affect Retention ?


Chairside Optical Sensor to Monitor Bacterial-Mediated Acidogenic-Profile of Saliva in Children

Research Highlights

Student: Dr.AnnieShresthaSupervisor: AssocProfAnilKishen

Despitemanyadvances indentistrytoday,areliable, costeffectiveand simple chairsidemethodtomonitorcariesactivityinanindividualisstill lacking.Themultifactorialetiologyofdental caries is considered to be the mainobstacleinthisdevelopment.Thecardinalstepincariesprocessistheformationofacidfollowingcarbohydrateintake,whichlowersthepHbelowthecriticallevel,resultinginthedissolutionanddisintegrationofdentalhardtissues.Further,certainsalivaryproteinsareknowntofacilitatebacterialadherenceandcolonizationto thetoothsurface.Thelevelsofsalivarytotal-proteinhavebeenassociatedwithbothcariesactivityandperiodontaldiseaseconditions.

Optical spectroscopy isahighlysensitivetechnique that can determine biochemicalparametersfromsalivabothquantitativelyandqualitatively. This studyaimed toapply theprinciplesofopticalspectroscopytomonitorbacterial-mediatedacidogenic-profileandtotal-proteinconcentrationofsaliva.Experimentswereconductedusingoptical spectroscopic

sensor (OSS) to monitor the bac ter ia l -mediatedacidogenic-profileof salivamixedwithsucrosefrom70childrenofagegroup6-12years.Bromophenolblue,apHsensitivephotoindicator,wasusedtomonitortherateofacidproductionbysalivarybacteriafollowingthe additionof sucrose. The findings fromtheOSSwerecomparedwiththepastcariesexperience(cariesscores:dmfsindex),cariesactivitydeterminedusingmutansstreptococcicounts(DentocultSM)andLactobacillicounts(DentocultLB)andpHshifts(pH-meter).TheOSS showed a decrease in the absorptionintensityat595nmwavelengthofsaliva-sucrosesamplewithdecreaseinthepH.Thehalf-lifedecayvaluedeterminedfromtheOSSdifferedsignificantlybetweenthecaries-active (CA),caries-inactive(CI)andcaries-free(CF)groups(P<0.05).ChildreninCFgroup(90%)showedlowMSandLBcounts.However,thiscorrelationwasweakincasesoftheCAandCIgroups.TheOSwasabletodistinguishchildrenshowingdifferentcariesactivity.

Figure 1:SchematicdiagramoftheexperimentalsetupoftheOSSusedinthestudy.

Abstract

MSc Project Thesis Title: Chairside Optical Sensor to Monitor Bacterial-Mediated Acidogenic-Profile of Saliva in Children Student: Dr Annie Shrestha Supervisor: Assoc Prof Anil Kishen Summary Despite many advances in dentistry today, a reliable, cost effective and simple chairside method to monitor caries activity in an individual is still lacking. The multifactorial etiology of dental caries is considered to be the main obstacle in this development. The cardinal step in caries process is the formation of acid following carbohydrate intake, which lowered the pH below the critical level, resulting in the dissolution and disintegration of dental hard tissues. Further, certain salivary proteins are known to facilitate bacterial adherence and colonization to the tooth surface. The levels of salivary total-protein have been associated with both caries activity and periodontal disease conditions.

Figure 1: Schematic diagram of the experimental setup of the OSS used in the study.

Optical spectroscopy is a highly sensitive technique that can determine biochemical parameters from saliva both quantitatively and qualitatively. This study aimed to apply the principles of optical spectroscopy to monitor bacterial-mediated acidogenic-profile and total-protein concentration of saliva. Experiments were conducted using optical spectroscopic sensor (OSS) to monitor the bacterial-mediated acidogenic-profile of saliva mixed with sucrose from 70 children of age group 6-12 years. Bromophenol blue, a pH sensitive photoindicator, was used to monitor the rate of acid production by salivary bacteria following the addition of sucrose. The findings from the OSS were compared with the past caries experience (caries scores: dmfs index), caries activity determined using mutans streptococci counts (Dentocult SM) and Lactobacilli counts (Dentocult LB) and pH shifts (pH-meter). The OSS showed a decrease in the

Computer

Spectrophotometer

Cuvette containing

saliva sample

Optical fiber

Light

source

MSc Project

Summary

13Research Report 08/09Faculty of Dentistry Research Highlights

Experimentswerealsoconductedtoquantifythetotal-proteinconcentrationofsalivausingOSS.AbsorptionIntensitiesforvariousproteinconcentrations were characterized using aproteinsensitiveindicatorcoomassiebrilliantblue(CBB).Finally,consideringtheabilityoftheOSStodetectmultipleparameters,afiberopticbasedsensorincorporatingtwosensingregionsfor pH (methyl red as the photosensitizer)andprotein(CBBasthephotosensitizer)wasfabricatedusingtheprinciplesoffiberopticevanescentwavespectroscopy(FOEWS)andsol-geltechnology.ThisexperimentdemonstratedtheabilityofFOEWStoquantifytotal-proteinconcentrationsandmonitor theacidogenic-profileofsalivausingasinglesensor.

This studyhighlighted theabilityofOSStodeterminebacterial-mediatedacidogenic-profileofsaliva,whichcanbeusedasacariesactivityindicator.TheFOEWSdevelopedwasabletomonitortheacidogenic-profileaswellasquantifythetotal-proteincontentofsaliva.TheOSScanbeasignificantapplicationforthechairsidemeasurementofclinicallyimportantparametersfromsaliva.

Figure 2:Graphsshowingdecrease

intheabsorptionintensity(595nm)of

salivaduetopHchangeasdetected

bytheOSS;(A)caries-active(CA);(B)

caries-inactive(CI)and(C)caries-free

(CF)groups.

Table 1: Differentparametersmeasuredfromchildrenofthethreecariesstatusgroups.Where,I0-opticalintensityattime

0;I180-opticalintensityattime180minandt1/2-half-lifedecayofthebacterialmediatedexponentialreaction.

1.2

1

0.8

0.6

0.4

0.2

0 6 0 1 2 0 1 8 0 2 4 0Time (minutes)

No

rmal

ized

inte

nsi

ty

(A)y = 0.9943e-0.0066x

R2 = 0.9578

(B)y= 1.1328e-0.0083x

R2 = 0.9578

(C)y = 0.9943e-0.0066x

R2 = 0.9876

BA C

Caries-Active (CA)

Caries-Inactive (CI)

Caries-Free (CF) Caries-Active (CA)

dmfs/ ds >1/ >1 >1/ 0 0/ 0 CA vs. CF CA vs. CI CI vs. CF

pH(T0-T180)

1.91±0.47 1.73±0.46 1.64±0.56 0.10 0.237 0.46

I0-I180 0.66±0.15 0.64±0.19 0.58±0.09 0.02* 0.77 0.40

Half life(t1/2)

94.92±57.49 66.88±62.53 136.72±46.30 0.005** 0.20 0.005**


Student: ProfKhooSuanPhaikSupervisor: AssocProf.AdrianYap&Dr.ChanYiongHuak

Introduction:TemporomandibularDisorders(TMD)encompassesacollectionofmedicalanddentalproblemsthatinvolvethemusclesofmastication,theTemporomandibularjointaswellasassociatedstructures.PainisthecommonreasonwhypatientswithTMDseektreatment.Thebiopsychosocialfactorsassociatedwithpainsymptoms(WIPS)inTMDpatientsandtheirroleinthepredictionofTMDtreatmentresponsearestilllargelyunknown.

Aims:Theaimsofthisprojectwereto(a)developacross-culturallyadaptedRDC/TMD(ResearchDiagnosticCriteriaforTMD)foruseinMalaysia,(b)comparethebiopsychosocialcharacteristicsofTMDpatientswithWIPSandwithoutpainsymptoms(WOPS)inamulti-racialurbanpopulationand(c)constructapredictivemodelforidentificationofnon-responderstoconservativeTMDtreatment.

Methods:TheRDC/TMDwascross-culturallyadaptedusingstandardproceduresandwasusedtocollectdataonthebiopsychosocialcharacteristicsof314TMDpatientsagedbetween18to74yearsfromanurbanMalaysiansetting.Across-sectionalstudycomparingthebiopsychosocialcharacteristicsofTMDpatientWIPSandWOPSwascarriedoutinordertodeterminefactorsthatwerelikelytobeassociatedWIPS.SelectioncriteriaforpatientsWIPSwasthepresenceofpainasthemainsymptom.PatientsWIPS(n=100)weregivenconservativeTMDtreatmentwithoutocclusalsplints.Patients’progresswasdocumentedat6weeksandat6months.OutcomemeasuresincludedimprovementinCPI(CharacteristicPainIntensity)andmaximalwidthofpain-freemouthopening.DataweresubjectedtounivariatefollowedbymultivariateanalysiswithSPSS.

Findings:Thecross-culturallyadaptedRDC/TMDwasfoundtobevalid,reliableandsuitableforuseinMalaysia.Differencesinsociodemography,physicalandself-reportedcharacteristicsandpsychologicalstatus

wereobservedbetween TMDpatientsWIPSandWOPS.Ofthese,factorsassociatedwithpainsymptomswerelimitedwidthofpain-freemouthopening(p=0.011),self-reportofnocturnaltoothgrinding/jawclenching(p=0.036),presenceofamyofascialpaindiagnosis(p=0.001)andlargerLRMF(limitationrelatedtomandibularfunctioning)scores(p=0.003).

Of the100TMDpatientsWIPSwhoreceivedconservativeTMDtreatment,69respondedpositivelywhile31didnot.Thesignificantfactorspredictiveofnon-responsetoconservativeTMDmanagementwerethefemalesex(p=0.013),limitedexcursive-protrusivejawmovement(p=0.014),highermusclepalpationscores(p=0.047),lowerdepressionscores(p=0.044)andself-reportsofuncomfortable/usualbite(p=0.014).

Amodelwasdevelopedforthepredictionofnon-responsetoconservativeTMDtreatment.Thiswasfoundtohaveasensitivityof80.6%,specificityof95.7%,negativepredictivevalueof91.7%andpositivepredictivevalueof89.3%.Respondershadgreaterimprovementinpsychologicaldistressscoresovertimewhencomparedtonon-responderstoconservativeTMDtreatment.

Conclusions:ThefindingsofthisstudyvalidatetheimportanceofbiopsychosocialfactorsinTMD.ThefoursignificantfactorsthatwereassociatedwithpainsymptomsinTMDpatientswerereflectiveofthepatients’self-reportedandphysicalcharacteristicswhilstthefivesignificantpredictivefactorsofnon-responsetoconservativeTMDtreatmentwerereflectiveofpatients’sociodemographic,psychologicalstatus,physicalandself-reportedcharacteristics.Potentialnon-responderstoconservativeTMDmanagementcanbeidentifiedbythesebiopsychosocialpredictorssothatamoretailoredtreatmentcanbeplannedfromtheoutset.ConservativeTMDtreatmentappearedtohavebeneficialeffectsonTMDpatientswithhighdepressionscores.

Biopsychosocial Characteristics as Predictors of Treatment Outcome of Temporomandibular Disorders (TMD) Patients with Symptoms of Pain

PhD Project

Research Highlights


Introduction:Ithasbeenwell-established that supportiveperiodontal therapy (SPT) is important inthemaintenanceoforalhealth. Therehasbeenincreasing emphasis on the use of “true”endpoints(e.g.toothloss)ratherthan“surrogate”endpointsfortheevaluationofeffectivenessofperiodontaltherapy.

Objectives:Theaimsofthisstudyweretoinvestigatetheincidenceand reasons for tooth lossduringactiveperiodontaltherapy(APT)andsupportiveperiodontaltherapy(SPT)inacohortofpatientstreatedinaninstitutionalpractice(NationalDentalCentreSingapore,NDCS).Comparisonwasmadewithasub-setofpatientswhofailedtoattendSPTfollowingAPT.PrognosticfactorsassociatedwithtoothlossduringtheSPTwerealsoidentified.

Subjects and Methods: This research comprised of two parts – alongitudinal retrospective cohort study (SPTgroup)andaclinicalrecallcross-sectionalstudy(non-compliance group). The longitudinalretrospectivecohortcomprisedofpatientswithchronicperiodontitistreatedandmaintainedforatleast7yearsbyperiodontistsattheDepartmentofRestorativeDentistry,NationalDentalCentreSingapore(NDCS).Patientswereidentifiedfromanelectronicpatientdatabaseandtheirrecordfolderswereretrievedandreviewed.Thenumberofteethpresentwasdeterminedatthreetimepoints:Initialexaminationandconsultation,endofAPTandthemostrecentSPTappointmentvisit.Reasonsandclinical/periodontalparametersfortoothlossweredocumented.Totalnumberoffoldersdrawnwas478anduponreview,273patientsmettheinclusioncriteria.

Thecross-sectionalcohortcomprisedofpatientswhodroppedoutaftercompletionofAPT(non-compliers).Theywereidentifiedfromthedatabaseandinvitedtoparticipateinthispartofthestudy.

Thepatientswererecalledandassessedontheexistingnumberofteethpresent.Afterreviewing1,318folders,207patientsmetthecriteriabutonly39patientsreturnedforclinicalassessment.

RelevantinformationwascollectedandenteredintoanExcelspreadsheet.DescriptivestatisticsweredoneusingSPSS.Thedifferencesinthetoothlossbetweenthe2groupswereanalyzedusing2 sample t-test if normality (assessedusingKomolgorovSmirnov)andhomogeneityassumptionsweresatisfiedotherwisethenon-parametric equivalentMannWhitneyU testwasapplied.Amultivariate linear regressionwasperformedtoadjustforrelevantcovariates.Significancewassetatp<0.05.

Results:ForthesubjectsintheSPTgroup,atotalof360teethwereextracted(1.3teeth/patient)duringAPT,withmulti-rootedteethhavingtwo-foldoddscomparedwithsingle-rootedteeth.DuringSPT(meanof10.7years),atotalof253teethwereextracted(0.9teeth/patient).Theannualtoothlossduetoperiodontitiswas0.03teeth/patient/year.Logisticregressionanalysisfoundthatageof>60wasahighlysignificantpredictoroftoothlossduringSPT(p=0.015),withadjustedoddsratioof2.1(95%CI:1.14–3.40).

Fornon-compliers(subjectswhofailedtoattendSPT),atotalof41teethwereextracted(1.1teeth/patient)duringAPT,whichwasnotsignificantlydifferentfromthoseonSPT.DuringdiscontinuationofSPTfor9.6years,atotalof107teethwerelost(2.7teeth/patient),a3-foldincreasecomparedwiththoseonSPT.Theannualtoothlossduetoperiodontitisinthenon-complierswas0.22teeth/patient/year,whichwas7-foldhigheroddsthanthoseintheSPTgroup(p<0.05).Logisticregressionanalysisfailedtoidentifytheage,gender,diabetes,initialperiodontaldiagnosisaspredictorsfortoothlossduringdiscontinuation.

Student: Dr.NgCherHui,MervynMain Supervisor: Dr.MarianneOngCo-Supervisors: AssocProfLimLumPeng,Dr.KohChuGuan&Dr.ChanYiongHuak

Tooth Loss & Patient Compliance in Periodontally Treated Patients: A Retrospective Analysis 7 Years or More After Active Periodontal Treatment

MDS Project

Research Highlights


Conclusions:Withinthelimitationsofthecurrentstudy,provisionofSPTledtominimaltoothloss,especiallyduetoperiodontitis,foraperiodof10yearsafterAPT.SPTisbeneficialregardlessofcompliance.However,completionofAPTwithoutSPTwillpredisposepatientstolosesignificantlymoreteethcomparedtopatientswhodoundergoSPT.

Research Highlights

17Research Report 08/09Faculty of Dentistry Completed Research

Projects in FY 2008/09

New Direction 1Aim:Todevelopa rapidandaccurate solution toconvertstoredorthodonticplastermodel fordigitalstorageusingconventionalhigh-resolutioncomputedtomographyasaviablesolutiontothecommonandexpensiveproblemofstorageforphysicalplastermodels.

Method: ApilotstudywasconductedononemaxillaryarchofaFrasacomodelofartificialhumanteeth.ThemodelwasscannedoncewiththeMinolta900VIVIDsurfacelaserscannerandthe64-sliceSiemensSomatomCTscanner.Mesio-distalwidthandbuccalcuspal-gingivalheightmeasurementsaremadeonbothvirtualimages.TheaccuracyisvalidatedagainstidenticalparameterstakenwithaCoordinateMeasuringMachine(CMM).Intheprecisionexperiment,thevirtualmodelsoftheCTandlaserscannerfromtheaccuracyexperimentareused.Theinter-caninedistanceismeasured10 times each on both virtual models. Themeasurementsarerepeated3dayslater.

Results:CTscanningoftheplastermodelisaccurateto0.39mmand0.80mmforbuccalcuspal-gingivalandmesio-distaldistances, respectively.Theprecisionerror iswithin0.2mmfortheinner-caninedistance.

Conclusion:TheconclusionfromthepilotstudyindicatedthatphysicalplastermodelscouldberapidlyandaccuratelyconvertedtodigitalproxiesusingCTscanning.

Afterthepilotstudy,anindepthstudyhassincestartedwiththeundergraduateUROPamdMDSOrthodonticresearchprogrammesto(i)identifytheoptimalCTscanningprotocolthatgivesthe

mostaccuratevisualdisplayofthevirtualmodel,and(ii)todeterminethecost-effectivenessofCTscanningincomparisonwithphysicalstorage.Anadditionalsteptodetermineaccuracyofmulti-sliceCTscannedplastermodelshadbeenundertakenusingconventionalCAD-CAMtechnology ingeneratingarapid-prototyped(RP)modeloftheCTscannedplastermodel.ThisRPmodelhasbeencomparedwiththeoriginalphysicalmodelusingCMM,andwillundergosurfacescanningforcomparisonofsurfacecontours.Datafromtheindepthaccuracy/precisionandcost-effectivenessstudieswillberepresentedattheUROPresearchpresentationinNovember2008andviaMDSthesisinJan2009.

New Direction 2Indevelopingtherapidandaccuratesolutiontothecommonandexpensiveproblemofstorageforphysicalplastermodels,theseconddirectionistodevelopa3DdigitalmethodofassessingtheIndexofOrthodonticTreatmentNeed(IOTN)andPeerAssessmentRating(PAR)indexstatusmalocclusionsfromuntreatedandtreatedcasesusingdigitalplastermodels.TheoutcomeofthisapproachwashighlypredictableasthecurrentresearchworkofthePIhasdevelopedtheabilitytodigitallyseparatetheindividualcrownsofeachtoothfromtheplastermodelbaseandgingival,andmovetheseparatedteeth.Theteamwasalsoabletodigitallyoccludethedigitalplastermodelsinmaximumintercuspationwithouttheaidofreferencebases.Withdigitallyoccludedmodels,thedigitalassessmentoftheseverityofthemalocclusionsviathePeerAssessmentRatingindexandtheIOTNcanbesemi-automated.Theseconddirection(startedinJanuary2008)wasstillworkinprogressunderaFacultyofEngineeringFinalYearProjecttodevelopthemeasurementsystemandGraphicalUserInterface(GUI)forthevirtualplastermodelsinocclusion.

Principal Investigator: AssocProfKelvinFoongTotal Project Value: S$66,705

An Assessment of Malocclusion Status in Hospital Based Orthodontic Patients

Summary/Achievements

Faculty of Dentistry 18 Research Report 08/09Completed Research


DemyelinationoftheperipheralnerveinvolveschangesintheUltrastructuresofmyelinandaffectssodiumandpotassiumchannelsatthenodesofRanvier.LowLevelLaserTherapy(LLLT)hasbeenpreviouslyreportedtopromotemyelination.Thisstudyusedchemicaldemyelinationachievedbylysolecithinapplicationontheexposedsciaticnerves. LLLTwasgiven to theexperimentalanimals.Therateandcompletionofremyelinationisnotedtogetherwiththereturnofnormalfeaturesofsodiumandpotassiumchannels.Inthecontrol

animals,demyelinationwasallowedtotakeitscourseandtherate&completionofremyelinationwereassessed.AcomparisonoftheresultsofthetwogroupsofratsdemonstratedasignificanteffectsoftheLLLTonremyelination.Theresultswerecommunicatedtotheinternationalmedicallasercommunity.Theimpactwouldbeseenintheclinicalmanagementofcurrentdemyelinationassociated neuropathic pain conditions likeTrigeminalneuralgia.

Principal Investigator: AssocProfYeoJinFeiTotal Project Value: S$45,150

The Effects of Low Level Laser Therapy on the Rat’s Sciatic Nerve, Following Lysolecithin – Induced Focal Demyelination


Aimsi) Tofindouttheperiodontalhealthofacohort

ofadultdiabetesinSingaporeii) Toevaluate longitudinally theeffectsofa

periodontalhealthprogrammeonperiodontalhealthstatusandmetaboliccontrolaswellassomeinflammatorymarkersinadultdiabetics

Thesubjectsweredividedintothreeperiodontaltreatmentmodality:Scaling+oralhygiene,scalingandacontrol.Allsubjectswereexaminedatbaseline,3monthsand9months.At9monthsallgroupsreceivedscaling+oralhygiene.Clinicalexaminationswerecarriedoutusingstandardperiodontalparametersandbloodtestswerealsotakentoevaluatethemetaboliccontrol.

ResultsPatientswithgoodglycaemiccontrolpresentedwithlesssevereperiodontaldiseaseintermsof

%bleeding,%calculus,andsiteswithincreasedprobingdepths.

Therewasa significant improvementof theplaqueandbleedingscoresandprobingdepthsofallpatients.Improvementwasmostmarkedinthescaling+Oralhygienegroup.Improvementwascomparableinpatientswithacceptableandunacceptableglycaemiccontrol.

Improvementinperiodontalhealthdidnothavesignificantimpactonglycaemicandmetabolicserummarkers.

ConclusionThestudyhighlightedtherelevanceofperiodontaltherapyinimprovingperiodontalhealthofpatientswithdiabetes.

Principal Investigator: AssocProfLimLumPengTotal Project Value: S$114,125

Prospective Study of Periodontal Disease Risk Markers and Treatment Outcome of a Periodontal Programme for Adult Diabetics in Singapore


Demineralizationandresorptionofhardtissuesarecommonsignsofdiseaseprocesswhichoftenaremediatedbybacteria.Bacteriapossesstheabilitytosurviveharshenvironmentalandgrowthconditionsbygrowingasabiofilmandbacterialbiofilmhasbeenassociatedwithmanychronic infectionsdiseasesinhumanbeings.Whenbacteriagrowasbiofilmsonhardtissuesurfacessuchasenamelanddentine,underfavorableconditions,theyincreasetheacidityatthevicinityofthebiofilm/hard-tissueinterface.This localizedincreaseinaciditymayleadtohard-tissuedemineralizationandsubsequentdisintegration (resorption). Understandingthismechanismofbiofilm formationwould

facilitateustodevelopnon-invasivestrategies(a) to remineralize, thedemineralized-hard-tissuesand(b)topreventsubsequentbacteria-induced-demineralizationofremineralized-hard-tissues.Previousstudieshadhighlightedthatcollagenfibrilsundergochemicalmodificationduringbiofilmformationanddemineralization.In this study, in vitrodemineralization andre-mineralizationexperimentswasconductedonenamelanddentinemodelsusingbothpH-cycleModelandBacterialModel.Theroleofdifferentapproachestofunctionalizecollagenindemineralizedsubstrates(dentine),suchasdeprotonation,chelation,phosphorylation,etc,wereevaluated.

FigureSEMmicrographsofcross-sectionandlongitudinaldentinespecimensafterdifferentperiodsofdemineralization:

(a),2day;(b),4day;(c)and(d),6day;(e)and(f),10day;(g)and(h),14day;(i)and(j)control.Thespecimensin(d)and

(f)underwentsonicationtreatmenttoremovethebiofilm.Theinsertin(g)isaFSEMmicrographshowingnetworkof

collagenfibrils(arrow)onthesurfaceofintertubulardentine.Theinsertin(h)isamagnifiedimageoftheleftofthis

SEMmicrographshowingthebacterialcells(arrow)penetratingintodentinaltubules.ODT:orificeofdentinaltubuleDT:

dentinaltubule;ID:intertubulardentine;PD:peritubulardentine.

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Completed Research Projects in FY 2008/09

Principal Investigator: AssocProfAnilKishenTotal Project Value: S$46,500

Biomimetic Remineralization of Demineralized Hard Tissue


Faculty of Dentistry 20 Research Report 08/09Completed Research


Summary/AchievementsTheaimofthisstudywastocompareexvivoosteogenesisofhESCs-derivedosteogeniccellswiththatofhumansomaticosteoblasts;tocompareinvivoosteogenesisofhESCs-derivedosteogeniccellswiththatofhumansomaticosteoblasts.

The conducted study was to compare theosteogenic potential of human embryonicstem cells (hESCs) within two- and three-dimensional(2Dand3D)culturesystems.hESCsof theH1 line (Wicell Inc.,Madison,Wisc.,USA)wereinducedtoformembryoidbodies(EBs) through5daysof suspension culturewithinnon-adherentculturedishes.Followingenzymaticdissociation,theEBderivedsinglecellswereseededoneithernovel3DporousPLGAscaffoldsor2Dculturedisheswiththesametotalcellnumber.Osteogenicdifferentiationwasinducedthroughculturemediasupplementedwith dexamethasone, L-ascorbic acid andb-glycerophosphate.After3weeksofinvitroculture,quantitativeandqualitativeassaysofosteogenicdifferentiationwereconducted.Osteocalcinsecretionandalkalinephosphatase(AP)activitiesweredetectedatsignificantlyhigherlevelswithin3Dculturecomparedwiththe2Dsystem.Subsequently,thecell-scaffoldconstructswereimplantediniliaccrestdefectsofimmunosuppressedrabbits.After4weeks,theconstructsweresubsequentlyexplantedandcharacterizedbyhistologyandX-rayanalysis.

Formationofnewbonewasdetectedwithinandaroundtheimplantedscaffolds.Theresultsdemonstratethattheosteogenicdifferentiationofhumanembryonicstemcellsisenhancedina3Dculturesystemcomparedtoa2Dcultureenvironment.Upon implantation insitu,thedifferentiatinghumanembryonic stemcellscan contribute positively to the repair andregenerationofbonedefects.

ThisstudyalsoevaluatedPLGAscaffoldsforbone regeneration within a rabbit model.The scaffolds were implanted at two siteson thesameanimal,within theperiosteumandwithinbi-cortical bonedefectson theiliaccrest.Subsequently,theefficacyofboneregenerationwithintheimplantedscaffoldswasevaluatedat4,12and24weekspost-surgerythroughhistologicalanalysis.Inboththeintra-periosteumandiliacbonedefectmodels,theimplantedscaffoldsfacilitatednewbonetissueformationandmaturationoverthetimecourseof24weeks,eventhoughtherewasinitiallyobservedtobelittletissueingrowthwithinthescaffoldsat4weekspost-surgery.Hence,the3DprintedporousPLGAscaffoldsinvestigatedinthisstudydisplayedgoodbiocompatibilityandareosteoconductive inboth the intra-periosteumandiliacbonedefectmodels.

Theproject hasgenerated threepublishedpapersinpeer-reviewedinternationaljournals.

Principal Investigator: Dr.VictorFanCo-Principal Investigator:A/PTongCaoTotal Project Value: S$179,850

Characterization of osteogenesis by human embryonic stem cell derived osteogenic cells


Thesuccessofacastrestorationdependslargelyonadequate resistanceandretention form.Resistanceformisdefinedasthose‘featuresofatoothpreparationthatenhancethestabilityoftherestorationandresistdislodgementalonganaxisotherthanthepathofplacement’.Factorsthataffecttheresistanceofacrownincludeauxiliarypreparationfeatures, totalocclusalconvergence,occluso-cervical(OC)dimensionand luting cement.A recent reviewon theprinciplesoftoothpreparationproposedthat3mmbetheminimumOCheightforpremolarstopossessadequateresistanceform.Howeverthisnumberwasbasedontheoreticalcalculationsandmonotonicload-to-failurestudies.

Inmostcasesteeth inneedoffullcoveragerestorationshavelostsubstantialtoothstructure,thereby making it difficult to incorporateadequate resistance and retention form.Placementoffoundationrestorationshasbeenadvocatedtoreplacelosttoothstructurepriortocrownfabrication.Ifthetoothtoberestoredisseverelydamaged,thencrownlengtheningand /or or thodontic ex trusion must alsobeconsidered.

Inspiteofallthisinformationnostudieshavebeendonetodeterminewhetherthepresenceoffoundationrestorations(coresandpost-cores)canenhanceresistanceform.Mostofthestudiesoncoresfocusedontestingdifferentmaterials,whilethoseonpost-coresfocusedondifferentconfigurationsandferruleheightsrangingfrom0-2mm.

Theaimofthisstudywastoevaluatetheloadfatigueperformanceof teeth restoredwithpostsandcores,withvaryingtoothheights,andtocomparethemwithsimilargroupshavingnopostsandcores.Thesecondaryaimwastodeterminewhetheracriticaltoothheightexistedatwhichtheplacementofafoundationrestorationresultedinnosignificantdifferenceintheloadfatigueperformance.Threetestgroupswithpreparedtoothheightsof2,3and4mmweretested.Thesewerecomparedwithanotherthreegroupswithsimilartoothheights,thistimerestoredwithprefabricatedtitaniumpostsandcoreheightsof4,3and2mm,respectively.Castcompletecrownswere thenfabricatedandcementedwithzincphosphate.Afatigueloadof58.8Nwasappliedatanangleof135degreestothelongaxisofeachcrown-toothspecimen.Thenumberofcyclestopreliminaryfailurewasdetermined.Theresultsshowedthatforall3toothheights,groupswithfoundationrestorationshadsignificantlyhighernumberofcyclestopreliminaryfailurethanthosewithoutfoundationrestorations.

Thisin-vitrostudysuggeststhatplacementoffoundationrestorationsonteethwithshortferruleheightsimprovetheclinicalperformanceofthefinalrestorations.


Principal Investigator: AssocProfJenniferNeoTotal Project Value: S$51,150

Effect of Foundation Restorations on the Load Fatigue Performance of Full Gold Crowns



This project was conducted in two parts.The first partof the studywas carriedoutto obtain better insight into the causes ofpersistenceofEnterococcus faecalis in rootcanaltreatmentfailedteeth.ThisinvestigationwascarriedouttoexamineE. faecalisbiofilmmediatedinflammatoryresponse.ThreestrainsofE. faecalis(ATCC29212,OG1RFandFA2-2),grownasplanktonicandbiofilmweretestedfor(1)theirhydrophobicityandsurfacecharge(2) intracellular survival (3)ability to induceinflammatorymediators(TNF-α,IL-6andNO)productionbymonocytes,and(4)abilitytoco-aggregatewithActinomyces israeliitostimulateinflammatoryresponsesinmonocytes.Inthefirstphaseofthestudymonospeciesbiofilm/planktonicbacteria(E. faecalis)weretestedfortheir interactionwithTHP1cells (monocyte)and in-vitrodifferentiatedmacrophages. Inthesecondphaseofthestudy,adualspeciesbiofilm/coaggregation(E. faecalisstrainswithA. israelii)wassimilarlytested.Findingsfromthis studyshowedthatnutrient-deprivationcouldsignificantlyincreasethehydrophobicityandsurfacechargeofbiofilmcells.Inaddition,nutrient deprivation significantly increased(p<0.05)theintracellularviabilityofE. faecalis

cells internalizedbymonocytesand in-vitrodifferentiatedmacrophages.AmongthethreeE. faecalisstrainstested,OG1RFandATCC29212strainsexhibitedlongerdurationofsurvivalthanFA2-2strain.In-vitrodifferentiatedmonocyteswhenco-culturedwithplanktonicE. faecaliscellsexhibitedasignificantlyhigher(p<0.05)productionofTNF-α,IL-6andnitricoxidethanwithbiofilmcellsfromnutrient-richandnutrient-deprivedconditions.PlanktonicmonoculturesofA. israeliicellswereabletoinduceasignificantlyhigher (p<0.05)TNF-α, IL-6andnitricoxideproductionby themonocytes compared toA. israeliibiofilmcells.However,thesecretionofTNF-α,IL-6andnitricoxidedecreasedwhenmonocyteswereco-culturedwithA. israelii-E. faecaliscoaggregatesorasco-adheredbiofilm.Thisstudyshowsthatbacterialbiofilms,amodeofgrowth inharshenvironments similar topost-treatmentendodonticenvironment,couldpotentiateE. faecaliscellstosurvivewithinthehostimmunecellsandstimulateaninflammatoryresponse. In addition, coaggregation ofE. faecaliswithA. israelii,anotherendodonticpathogen,couldattenuatetheinflammatoryresponseandfacilitatetheintracellularsurvivalofbacteria.

Figure:THP1cells infectedwithE. faecalis

(ATCC29212)planktonicandbiofilmbacteria

.A&B THP1 cells infected with planktonic

bac ter ia. Arrow in f igure A shows the

internalized bacteria (green fluorescent).

C&Dshowsgreen fluorescingnutrient rich

biofilmbacteriawithinTHP1cellsandsurface

adheredbacteriaappearred.Arrowindicates

surfaceboundbacteria(redfluorescent).E&F

shownutrient-deprivedbiofilmcellswithin

theTHP1cells.Dataisrepresentativeofthree

independentexperiments.

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Intra-radicular Causes of Persistent Endodontic Infection



AimsHigh-intensity focusedultrasound (HIFU)produces col lapsing cav itat ion bubbles.Thisstudyaimsto investigate theefficacyofcollapsingcavitationbubbles todeliverantibacterialnanoparticlesintodentinaltubulestoimproverootcanaldisinfection.

MethodsIn stage1,experimentswereperformed tocharacterizetheefficacyofcollapsingcavitationbubblestodelivertheminiatureplasterbeadsinto a tubular channel model. In stage 2,experimentswereconductedonroot-dentinblockstotesttheefficacyofHIFUappliedat27kHzfor2minutestodeliverantibacterialnanoparticlesintodentinaltubules.Afterthestage2experiment,thesamplesweresectionedandanalyzedusing fieldemission scanningelectron microscopy and energy dispersiveX-rayanalysis.

ResultsThestage1experimentshowedthatcollapsingcavitationbubblesusingHIFUdeliveredplasterbeadsalongtheentire lengthofthetubularchannel. Itwasobserved from the stage2experimentsthatthediffusionoffluidsalonewasnotabletodeliverantibacterialnanoparticlesintodentinaltubules.Thecollapsingcavitationbubbles treatment using HIFU resulted insignificantpenetrationup to1,000mmofantibacterialnanoparticles into thedentinaltubules.Thestatisticalanalysisshowedahighlysignificantdifferenceinthedepthofpenetrationofantibacterialnanoparticlesbetweenthetwogroups(<0.005).

ConclusionThecavitationbubblesproducedusingHIFUcanbeusedasapotentialmethodtodeliverantibacterialnanoparticles intothedentinaltubulestoenhancerootcanaldisinfection.(JournalofEndod2009;35:1028–1033)

Figure.FieldEmissionScanningElectronMicrographsof

dentinesamplefromcontrolgroupwithoutHIFUtreatment

(A-C).Thedentinaltubulesopeningtowardstherootcanal

wallisdevoidofanyantibacterial-nanoparticlesattached

tothesurface(A).Thecross-sectionofthedentinesamples

withexposeddentinaltubulesdoesnotshowantibacterial-

nanoparticleswithinthelumen(B,Cmagnifiedinletfrom

B).FieldEmissionScanningElectronMicrographsofdentinal

tubulesfromtheHIFUtreatmentgroupsample(D-F).Lower

magnificationviewofdentinaltubules(D).Theinletin

(D)ismagnifiedin(E)showingantibacterial-nanoparticles

penetratingintothedentinaltubules.Thedistributionof

antibacterial-nanoparticleswasfoundtobenon-uniform

alongthelumenofthedentinaltubules(blackarrow)and

thenanoparticlesshowedatendencytoformaggregates

(whitearrow).Asingledentinaltubulewithantibacterial-

nanoparticleswithinitslumen(F)showingaggregationof

antibacterial-nanoparticlesof100±20μmsizes.

A B

C D

E F



Removal of Bacterial Biofilms Using Focused Ultrasound for Endodontic Disinfection


Despitetheadvancesinoralhealthpromotion,dentalcariesremainsamainhealthproblemthreateningchildren’shealthworldwide. InSingapore,althoughperiodicoralhealthsurveyswereconductedamongschoolchildren, thecaries prevalence among preschoolers hasnotbeendocumented.Cariesriskassessment(CRA) isconsideredanessentialcomponentforcost-effectivecariescontrolandevidence-basedtreatmentplanning.Nevertheless,theapplicationof caries riskassessment in thecommunityandclinicalsettings ishamperedbythelackofapracticalcariesriskassessmenttoolwithsufficientsimplicityandaccuracy.ThemainobjectivesofthisstudyweretoprofilethecariesstatusofpreschoolersinSingaporeandtoestablishandvalidateanepidemiologicallyandclinicallypracticaltoolforcariesriskassessmentforcost-effectivecariescontrol.

With ethical approval andparents’writtenconsents, 1,782 children aged 3-5 yearswere recruited from 13 randomly selectedkindergartens.Thebaselinedatawereobtainedin 2005 through a parent-administeredquestionnaire,anoralexamination,andsalivarytests.After12months,thecariesstatusof1,576(88%)childrenwasfollowedup.TheplaquepHvaluesof1,207childrenweremeasuredthroughamicro-touchmethod. The cariesprevalenceandoralhealthknowledgeattitudesandpracticeweredescribedandcomparedamong ethnic and socioeconomic groups.Bothtraditionalstatisticalmethods(multipleregressions)andartificialneuralnetworks(ANN)wereemployedforconstructingandvalidatingcariesriskassessmentmodels.

This study revealed that dental caries is asevere oral health problem affecting 40%childrenaged3-5yearsinSingapore.Thecariesdistribution was highly skewed. Prominentoralhealthdisparityexistedamongethnicandsocioeconomicgroupsandwaspartlyexplainedbyamultilevelbehavioralpathwaysubstantiatedby Structural Equation Modeling. Multiplebiopsychosocialcariesriskfactors/indicatorswereidentified.Variouscariesriskassessmentmodelswereconstructedandvalidated.Withthe sensitivity/specificity of 82%/73% and90%/90%,thescreeningandfull-blownmodelsreachedahigheraccuracyincariesprediction,ascomparedwithCariogram.Thesemodels,cateringtovariousneedsatthecommunityandclinicalsettings,arepromisingtoolsforcost-effectivecariescontrolandevidence-basedtreatmentplanning.

The resultsof this studyhaselucidated thecurrentcariesprofileamongthepreschoolersinSingaporeandconfirmedtheresurgenceofcaries.ThehighaccuracyoftheCRAmodelsachievedinthisstudyhavewonaninternationalresearchawardconferredbytheInternationalAssociationforDentalResearch (IADR).Theresults have also drawn the attention ofgovernmentalagentsandhavebeenreviewedfortherelatedhealthcarepolicyplanning.


Principal Investigator: AssocProfStephenHsuTotal Project Value: S$144,925

Caries Risk Assessment for Children in Singapore


25Research Report 08/09Faculty of Dentistry New Research Projects Awarded

for Funding in FY 2008/09

Mechanicalstressisanimportantdeterminantofbonemassandarchitecture. Increases inbonestrainsaboveacertainthresholdhavea positive effect on bone mass, whereasreductionsinstrainmagnitudeleadtobonelossandosteopenia.Theaimofthisstudyistotestthehypothesisthatmechanicalstrainisakeydeterminantofosteoblastdifferentiationandfunction,andcanactoncellsoftheosteoblastlineageinadose-dependentmanner.Inotherwords, whether the osteoblastic responseresultsinanosteogenicorresorptivestimulusinboneisdependentuponthebiomechanicalenvironmentofthecells.

Specifically,mechanically-inducedstrainwillbeappliedtoratcalvarialosteoblastsinvitroinaFlexercellapparatusdesignedtodelivertensionorcompressionofvariabledurationtoculturedcellsundercontrolledexperimentalconditions.TotalRNAwillbeextractedfromthecells,assessedfordegradationstatusandthenassayedforthedifferentialexpressionofgenesinvolvedin(1)osteoblastdifferentiationandboneformation,(2)cell–cellandcell–matrixinteractions,and(3)apoptosis(programmedcell death). For genes showing significantdifferentialexpression,theculturesupernatantswillbeassayedforthecorrespondingproteinbyenzyme-linkedimmunosorbentassays(ELISAs),andtheirbiologicalactivitytestedusinginvitroboneresorptiveassays.

Theresearchincludes:

1. os teob las t pr imar y cu l ture: get t ingosteoblastsfromneonateSDrat’scalvarialboneandcharacterizingtheosteoblasts;

2. tests of osteoblasts’ functions undermechanicaltension:

(a) vitality of osteoblasts under the mechanical tensions:

(b) apoptosis of osteoblasts under the tension;

(c) biomolecular reactions of osteoblasts to mechanical tension: RNA extraction; RT-PCR microarrays; ELISAs analysis, etc;

3.results/statisticalanalysis;

Summary

Principal Investigator: Dr.LiXiaobingTotal Project Value: S$128,500

The Bio-molecular Responses of Rat-derived Osteoblasts to Mechanical Strain in vitro

Osteoblastprimarycultureandcharacterization:

1:primaryculture:16/02/2009----25/03/2009.

10neonatalSDratsused:calvarialbonescut,digested,

andplateout,andcellspassagedtoPassagefive(fig.1).

(fig.1):primarycalvarialderivedosteoblasts:P5;

Faculty of Dentistry 26 Research Report 08/09New Research Projects Awarded

for Funding in FY 2008/09

Dental implants requireaperiodof limitedor no loading in order for bone ingrowthandosseointegrationtoprogresssufficientlyfor the implant tobear load. Prematureorinadvertent loadingduring theperiodafterimplantationmayresultinlossoffixationwiththeformationoffibroustissueattheimplantbonejunction.Currentpracticeistolimitearlyloadbearingactivities,however,thismaynotbedesirablefromafunctionalorrehabilitativeperspective.Therefore,itishighlydesirabletoenhanceandacceleratebone ingrowthandosseointegration immediatelyafter surgery.This studyuseselectrospunnanofibersandbiomineralizationtomodifythetitaniumsurfacetoenhanceosseointegration.Ourhypothesisisthatthemodifiedsurfacewillimprovestemcellcaptureandthereforeincreasethenumberofosteoprogenitorcellsattheimplantsite.Ti6Al4Vdiscs were pretreated and PLGA, collagenblendedPLGA,nano-hydroxyapatite/PLGA,andnano-hydroxyapatite/collagen-blendedPLGAnanofiberswerefabricatedusingastandardelectrospinningprocess.Humanbonemarrowderivedmesenchymal stemcellswere thenseededontothetestsampleswithuntreatedtitaniumdiscasthecontrol.Thesampleswereincubatedfor10,20,30and60minutes,afterwhichtheattachmentefficiencyofeachsamplewasevaluated.At10minutes,cellsstartedtoadhere to all the modified surfaces. There

was50%ormorecelladhesiononthenano-hydroxyapatite/PLGA,andnano-hydroxyapatite/collagen-blended PLGA nanofibers at 30minutes.At60minutes,celladherencewas75%inthenano-hydroxyapatite/collagenblendedPLGA,64%inthenano-hydroxyapatite/PLGA,52%inthecollagenblendedPLGAand38%inthePLGAnanofibers.Nocelladhesionwasseenontheuntreatedtitaniumplatesat60minutes.Thissuggeststhatthesurfacemodificationsenhanceearlycellcapturewhencomparedtountreated titanium.Anano-hydroxyapatite/collagenblendedPLGAcoatedtitaniumsurfaceinparticular improves initialcellattachmentwhichmayprovetobebeneficialforenhancingosseointegration.

Electrospun nanofibers

Principal Investigator: Dr.ClarisseNgTotal Project Value: S$165,829.42

Biomimetic Surface Modification of Dental Implants for Enhanced Osseointegration

Summary


The aim of this study was to measure the3-Daccuracyofplastic transfer impressioncopingsof3implantsystems,asafunctionofimplantangulations.Thenewerplastictransferimpressioncopingshadnotbeentestedfortheiraccuracyintransferof implantpositiontoamastermodel.Errorsduringthisstageoffabricationofprosthesishadbeenshowntoleadtostressbuild-upintheimplantcomponentsand/orprosthesis.Non-parallelorangulatedimplantscouldleadpotentiallytoincreaseddimensionalinaccuracy.TheuseofaCoordinateMeasuringMachine(CMM)allowedthe3dimensionallydetection of these errors. This study wasintendedtocomparecomponentsfromthreeimplantsystems,vizTissueLevelImplantSystem

(Institut Strauman AG), Osseotite CertainSystem(ImplantInnovationsInc)andBranemarkImplantSystem(NobelBiocare).Mastermodelsusing twoadjacent implantswithdifferingangulationswillbefabricated.Astandardizedimpressionandmodel fabricationtechniquewouldbeusedtocreateworkingcasts.ThedifferenceinpositionoftheimplantsbetweenthemastermodelsandtheworkingcastsshallbemeasuredusingCMM.Quantificationofthesetransferinaccuraciesintermsoftheθx,θyandθzrotationaldisplacementsaswellasx,yandz lineardisplacements (6degreesoffreedom)wouldprovideclinicianswithrelevantinformationinassessingtheclinicalsuitabilityofthecomponentsandtechniquesstudied.

New Research Projects Awarded for Funding in FY 2008/09

Summary

Principal Investigator: AssocProfKesonTanTotal Project Value: S$50,880

3-D Accuracy of Plastic Transfer Impression Copings for 3 Implant Systems

Fig 2.CMMprobemeasurementtodefine3-Dpositionof

Implantabutments

Fig 1ImplantMasterModelwithPlasticPick-upImpression

Coping


Present study was carried out to examineglobalgeneexpression in thebrainstem, inamousemodeloforofacialpain.Mice thatreceivedfacialcarrageenaninjectionshowedincreasedmechanicalallodynia,whichpeakedat3-4daysafterfacialcarrageenaninjection,demonstratedbyincreasedresponsestovonFreyhairstimulationoftheface(Fig.1.).Themicebrainstemwereharvestedat3dayspost-injection,andanalyzedbyAffymetrixMouseGenomemicroarrays.CommongenesthatarechangedintherespectivesidesofthebrainstemwereidentifiedandclassifiedusingtheGeneOntology(GO)termenrichmentanalysisfromthe DAVID resource website (http://david.abcc.ncifcrf.gov/).Thetopcategoryshowed

“leukocy tes adhesion” and the 2 genesinvolved in this categoryareP-selectinandIcam-1.P-selectinandIcam-1expressionwerefurthervalidatedusingreal-timeRTPCRandwesternblot (Fig.2&3).WepostulatethatincreasedP-selectin and Icam-1expressioncould contribute to pro- rather than anti-nociception,probablythroughtheenhancementofmacrophage/monocyteentryintothebrain.Anattempttoreversefacialcarageenaninducedhyperalgesiausinginhibitorstothedifferentiallyexpressedgeneswill be carriedout. Thesecouldpavethewayforidentificationofnoveldrugtargetsfortheclinicaltreatmentofhumanorofacialpain.

UC

B

* *

*

*

* **

**

35

30

25

20

15

10

5

0

No

. of

Face

Str

oke

s

Left injected vs Left Untreated

BI 1D 2D 3D 4D 5D 6D 7D 8D 9D 10D 11D12D

UC

A

*

*

** *

**

**

35

30

25

20

15

10

5

0

No

. of

Face

Str

oke

s

Right injected vs Right Untreated

BI 1D 2D 3D 4D 5D 6D 7D 8D 9D 10D 11D12D

Fig. 1.ResponsestovonFreyhairstimulationofthefaceaftertissueinflammationinducedbycarrageenaninjection.

(A)Right-sidedfacialcarrageenaninjection.(B)Left-sidedfacialcarrageenaninjection.BI:beforeinjection,1Dto12D

referto1dayto12daysafterinjection.U:untreatedcontrol.C:afterfacialcarrageenaninjection.AnalyzedbyStudent’s

t-test.Asterisksindicatesignificantdifference(P<0.05).


Principal Investigator: AssocProfYeoJinFeiTotal Project Value: S$146,400

Global Gene Expression Analysis in the Mouse Brainstem after Hyperalgesia Induced by Facial Carrageenan Injection

Summary

Day Day


Control

Control

P-selectin

Beta-selectin

A

UC

B

*

*30

25

20

15

10

5

0

Fold

Ch

ang

e

Right injected vs Right Untreated

ICAM-1 P-selectin

UC

A

*

*

30

25

20

15

10

5

0

Fold

Ch

ang

e

Left injected vs Left Untreated

ICAM-1 P-selectin

Fig. 2.Real-timeRT-PCRanalysisofdifferentiallyexpressedgenesinthebrainstemafterfacialcarrageenaninjection.

P-selectinandICAM-1inthemousebrainstemafterfacialcarrageenaninjection.(A)Right-sidedfacialcarrageenan

injection.B:left-sidedfacialcarrageenaninjection.U:untreatedcontrol.C:afterfacialcarrageenaninjection.Analyzed

byStudent’st-test.Asterisksindicatesignificantdifference(P<0.05).

Fig. 3.Westernblotanalysisofhomogenatesofthebrainstemforuntreatedand3-daypost-facialcarrageenan-injected

mice.(AandB)Leftpanels:theantibodytoP-selectin(A)andICAM-1(B)detectedsinglebandsat~140kDaand~90

kDa,respectively.Rightpanels:nobandsweredetectedinnegativecontrolsthatwereincubatedwithPselectinor

ICAM-1antigen-absorbedantibodies.

Treated

Treated

NegativeControl

NegativeControl

Icam-1

Beta-selectin B

A



Tissue regenerated oral skin and mucosaequivalentshavebeensuggestedtobetheidealsubstitutestoreplacevariousautologousskinormucosalgraftsforthetreatmentofdefects,usuallybecauseofsurgicalexcisions,injuries,andcongenitaldiseasesintheoralmaxillofacialregion.Fortissueregenerationoforalskinormucosalgrafts,itcouldbepossibletoutilizeeitherEScellsderivedfromtheinnercellmassofblastocyst-stageembryos[Trounson,2002],oradultstemcellsofnon-epidermalorigin,suchasthatderivedfromthebonemarrow[Kataokaetal,2003]andperipheralbloodcirculation[KorblingM,etal,2002],whichhavealsobeenshowntobecapableoftrans-differentiationintothekeratinocytelineage.Nevertheless,therewereanumberoffactorsthatwouldnotfavortheuseofadultstemcells[NIH,2008a;Coraux,etal,2003;Green,etal,2003]overembryonicstemcells.Amongthem, themortalityandlimitedrenewalcapacityofadult stemcellswasmostambiguousandthesubjectofmuchcontroversy.Bycontrast,theimmortalityandself-renewal capacityofhumanembryonicstemcells(hESCs)wasunquestionable.Besides,hESCsaregeneticallyyoungerandhealthier.

TheresearchwastostimulateanddirectthehESCdifferentiationtowardsthekeratinocyte


Principal Investigator: AssocProfCaoTongTotal Project Value: S$125,800

Keratinocyte Differentiation of hESCs for Potential Dental, Medical and Wide Biotech Needs

Summarylineages.hESCs-derivedkeratinocytesarethebestsourcetogeneratehumanoralskinandmucosa, which could be utilized for manypurposes.Themajorapplicationsarepotentiallyinthedental,medicalandbiotechareasof:(1)thestudyofgeneticanddevelopmentalmechanismsrelatingtoskinormucosaregeneration,(2)thestudyofgene/proteindeliverytherapytocureskinororalmucosalesions;(3)thestudyofcell-injectiontherapyforskinormucosarepair;(4)thestudyofcelltransplantation-basedskinormucosareconstructionandregeneration;(5)thediseasestudyanddrugdiscovery(NIH,2001)forskinandmucosa;(6)thedevelopmentofnoveltoxicityscreeningtestsforepithelium-relatedbiomaterialsanddrugs;and(7)thedevelopmentandvalidationofhESCepithelialmodelsforwide biosafety-health evaluation of foodproductsandsupplements,cosmetics,personalcareproducts,houseandofficeproducts,livingandworkingenvironment,water,soil,airandnaturalenvironment.ThekeratinocytelineagesderivedfromhESCswouldbeestablished inSingapore,asaresultofthisproject.Moreover,thescientificdataandintellectualpropertiesofhESCkeratinocytedifferentiationwouldbesetupinFOD/NUS,pioneeringinglobaldentistry,forvariousapplicationsinthenearfuture.

Human skin/mucosa cells differentiated from an embryonic

stem cell

Day

-21,

Hol

ocl

one

Day

-10,

K18

&D

api

Day

-20,

K14

&D

api

Day

-10,

K18

&D

api

CD

44


IntroductionTheformationofwhitespotlesions(WSL)aroundorthodonticbracketsisoneofthemajorrisksoffixedorthodontictreatmentandpresentsasanaestheticissuefororthodontistsandupto48%ofpatients.Severalstudieshavereportedthe increase inresistancetodemineralizationinenamelafterlaserirradiation.However,thelasereffectshavebeencharacterizedinchemicalmodelsbutnotinabiofilmmodelmimickingintra-oralconditions.Yakultisapopularsoftdrinkforchildrenandteenagersandhasdemonstratedacariostaticeffectinourpreviouspilotclinicaltrial.ThecombinedeffectoflaserandYakulthasnotbeeninvestigatedintheliterature.

Objective1)Tocharacterizeinabiofilmmodeltheeffectsofcarbondioxidelasertherapyonpreventionofenameldemineralizationaroundorthodonticbrackets;2)toevaluatetheeffectsofYakultonlasedenamelaroundtheorthodonticbracketsinthesamebiofilmmodel.

MethodsFor Phase-I: Freshly extracted premolar ormolarteethwithoutdecaywillbeselectedandorthodonticbracketswillbeplacedontheseteethwithaconventionalcompositeresin.Fourdefinedwindowareanexttothebracketswillbe irradiatedwith3setsof laserparameterswiththeremainingnon-irradiatedareaselected

asthecontrol.AbiofilmreactordevelopedbytheCenterforDiseaseControl(CDC,USA)willbeusedtodevelopadentalbiofilm,simulatingintraoralcondition and demineralization. Before andafter4-weekincubationwithoralbacteriaandpooledhumansaliva,themineralcontentoftheexperimentalandcontrolsiteswillbequantifiedbyaMicro-computedTomography(μCT)scanner.The factorial ANOVA will be employed tostatisticallyevaluatethepreventiveeffectsoflasertherapiesandthesite-specificityoflasereffect.ForPhase-II:Thesamelaserparameteremployedinthephase-IstudywillbeusedtopreventWSLaroundorthodonticbracketsinabiofilmsystemsuppliedwithdailyYakultrinsefor2weeks.Thesamemineralprofilingmethod(usingμCT)willbeconductedbeforeandafterthelesiondevelopmentinthesamebiofilmsystemplusadaily1-minflushofone-bottleYakultfortwoweeks.ThesampleswillberetrievedfromthesystemforenumerationofplaquepHattheendof2-weekand4-weekperiods.ThefactorialANOVAwillbeemployedtostatisticallyevaluatethepreventiveeffectsoflasertherapies,Yakult,andthesite-specificityonplaquepHandmineralloss.Theresultsofthisstudymaydeepenourknowledgeofpreventivelasereffectonenameldemineralizationinamicrobiologicalsystemandpavethewayfortheclinicalapplicationoflaserand/orprobiotictherapiesinpreventingwhitespotlesionsoforthodonticpatients.

Investigatingthebiofilmaroundthe

orthodonticbracketandlaser-induced

cariesprevention

TheCDCbiofilmreactor,developed

bytheCentersforDiseaseControl

andPrevention(CDC)In2002

MineralprofilingusingMicro-CTtoquantify

thecaries-preventiveeffectonenamel

Principal Investigator: AssocProfStephenHsuTotal Project Value: S$121,920

Effects of Yakult and laser therapy on preventing enamel demineralization around orthodontic brackets in a biofilm model



Research Collaborations in AY 08/09

Research Achievements

Collaborating Organizations Year Department Region

Universities

Massachusetts General Hospital, Harvard University, USA 2007 - 2009 Restorative Department International

University of Texas Health Science Center at San Antonio, USA 2007 - 2009 Restorative Department International

University of Wisconsin Madison 2003 - 2009 Oral and Maxillofacial Surgery International

Harvard University 2004 - 2009 Oral and Maxillofacial Surgery International

Peking University 2007 - 2009 Oral and Maxillofacial Surgery International

Tsinghua University 2006 - 2009 Oral and Maxillofacial Surgery International

Zhejiang University 2005 - 2009 Oral and Maxillofacial Surgery International

University of Otaga 2009 Restorative Department International

Jiaotong University 2006 - 2009 Oral and Maxillofacial Surgery International

Industries

Bio-Scaffold 2004 - 2008 Oral and Maxillofacial Surgery Local

Research Institutes

SIMTech Pte Ltd, A*STAR 2007 - 2009 Oral and Maxillofacial Surgery Local

Tissue Modulation Laboratory 2007 - 2009 Preventive Dentistry Local

Research Awards & Prizes Awarded in AY 2008/09

Awardee(s) Name of Award International or Local/Regional

Awarding Agency

Title of Article/Project

A/P Cao Tong International Collaboration Grant, Ministry of Science and Technology, PRC

International Ministry of Science and Technology, PRC

Development of hESC models for toxicity evaluation

Dr. Liu HuaA/P Cao Tong (Supervisor)

The China Scholarship Council Award 2008

International China Scholarship Council

NA

33Research Report 08/09Faculty of Dentistry Research Achievements

List of Editorial Board Memberships in AY 2008/09

Name of Staff Name of Journal/ Book Series Journal Tier Position Held

Prof Loh Hong Sai Singapore Dental Journal Reputable Section Editor

Prof Murray Clyde Meikle

Royal College of Surgeons, Edinburgh. Journal

Reputable Editorial Board Member

A/P Anil Kishen Singapore Dental Journal Reputable Section Editor

Optics and Lasers In Engineering Leading Editorial Board Member

Journal of Applied Oral Science Others Editorial Board Member

Open Dentistry Journal Others Editorial Board Member

A/P Keng Siong Beng Singapore Dental Journal Reputable Editorial Reviewer

A/P Lim Lum Peng Singapore Dental Journal Reputable Editorial Reviewer

Oral Health & Preventive Dentistry Others Editorial Board Member

Hong Kong Dental Journal Others Editorial Adviser

A/P Neo Chiew Lian, Jennifer

Journal of Dentistry Premium Editorial Board Member

Operative Dentistry Others Editorial Board Member

A/P Ong Hui Lian, Grace European Journal of Dental Education Leading Board member

A/P Sae-Lim, Varawan Journal of Endodontics Premium Scientific Advisory Panel of Editorial Board

Journal of Periodontology Premium Reviewer

Dental Traumatology Premium Editorial Board Member

Journal Of Dental Research Premium Reviewer

Acta Biomaterialia Others Reviewer

Singapore Dental Journal Reputable Reviewer

A/P Tan Beng Choon, Keson

Journal Of Oral Rehabilitation Leading Editorial Board Member

Singapore Dental Journal Reputable Editorial Reviewer

A/P Yeo Jin Fei Singapore Dental Journal Reputable Editorial Reviewer

Dr. Clarisse Ng Chai Hoon

Journal of Prosthodontics Leading Editorial Board Member

Dr. Uy Joanne Ngo Singapore Dental Journal Reputable Editorial Review Board Member

Singapore Dental Journal Reputable Editorial Reviewer

Faculty of Dentistry 34 Research Report 08/09 Research Statistics

New Research Students by Nationality

Enrolment of Research Students35

30

25

20

15

10

5

0

12

11

10

9

8

7

6

5

4

3

2

1

0

AY 2001/02

AY 2001/02

AY 2002/03

AY 2002/03

AY 2003/04

AY 2003/04

AY 2004/05

AY 2004/05

AY 2005/06

AY 2005/06

AY 2006/07

AY 2006/07

AY 2007/08

AY 2007/08

AY 2008/09

AY 2008/09

Academic Year

Academic Year

No

. of

Stu

den

tsN

o. o

f St

ud

ents

PhD

Foreign Students (FS)

MSc

Singapore Permanent Resident (SPR)

2

7

13

17

1213

14

17 17

17

17

15

19

14 14

11

7 8 5

5

8

2 64

3

1

4

2

1

2

4

0


Research Fundings

New and On-going Research Projects

Research Statistics

$1,600,000

$1,400,000

$1,200,000

$1,000,000

$800,000

$600,000

$400,000

$200,000

$0

40

35

30

25

20

15

10

5

0

AY 2001/02

AY 2001/02

AY 2002/03

AY 2002/03

AY 2003/04

AY 2003/04

AY 2004/05

AY 2004/05

AY 2005/06

AY 2005/06

AY 2006/07

AY 2006/07

AY 2007/08

AY 2007/08

AY 2008/09

AY 2008/09

Financial Year

Academic Year

Am

ou

nt

of

Fun

din

gN

o. o

f St

ud

ents

On-going Projects

New Projects

22

30

22 23

20

22

15

14

7 68 8 8

5 5

8

$799,915

$217,000

$0

$550,000

$786,805

$393,300

$1,308,020

$1,009,346

$426,276

$0

$530,000$498,524

$20,000

$962,690

$528,550

$674,252$589,000

$260,647

$10,000

$818,207

$376,050

$95,000

$525,069

$592,000

NUS Funding

External Funding

Research Scholarship


Research Publications80

70

60

50

40

30

20

10

0FY 2001/02 FY 2002/03 FY 2003/04 FY 2004/05 FY 2005/06 FY 2006/07 FY 2007/08 FY 2008/09

Financial Year

Academic Year

No

. of

Pub

licat

ion

sN

o. o

f Pa

per

s

15

57

22

33

6

0

8 8

24

39

11

17

41

19

10

24

7

13

66 57

41

7369

47

29 28

Conference Papers120

100

80

60

40

20

0AY 2001/02 AY 2002/03 AY 2003/04 AY 2004/05 AY 2005/06 AY 2006/07 AY 2007/08 AY 2008/09

Total

4247

33

74

84

68

106

61

Research Statistics

Premium

Leading

TotalReputable

Others

1216

1 3 14

16

23

38

34


Research InternshipsTheFacultyofDentistryhasreceivednumerousstudentsfromvariousschools,bothlocallyandinternationallyasresearchinterns.TheseschoolsincludeJuniorColleges,Polytechnics,andoverseasUniversities.Thedurationoftheinternshipvariesfromafewmonthstoaboutayear.Theinternshipcaneitherbefull-timeorpart-time.

ThesestudentsreceiveguidancefromtheacademicstaffmembersfromtheFaculty,bylearningandworkingunderthespecificresearchprojectsofthestaffmembers.

Research Statistics

FACULTY OF DENTISTRYNational University of Singapore

5LowerKentRidgeRoad,Singapore119074Telephone:(65)67724987Facsimile :(65)67785742http://www.dentistry.nus.edu.sg

faculty of research report faculty of 08/09 dentistry 2010/nus dentistry... · 2 faculty research...

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