Vieira Carvalho, Ana Maria Ramires dos Santos

English

Dental erosion, the dissolution of hard tooth tissues due to acids of nonbacterial origin, can cause extreme tooth material loss especially if combined with mechanical factors in the mouth. The best approach to prevent the problem is to reduce the acid challenges in the mouth. This, however, poses a problem when dealing with erosion due to intrinsic factors as gastro-intestinal problems or low patient's compliance in erosion due to acidic diets. ... Zie: Summar

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   University of GroningenErosive enamel wear and the inhibiting effect of topical fluoridesVieira Carvalho, Ana Maria Ramires dos SantosIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2006Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Vieira Carvalho, A. M. R. D. S. (2006). Erosive enamel wear and the inhibiting effect of topical fluorides.s.n.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 06-06-2022Dental  eros ion,  the d issolut ion of  hard tooth t issues due to ac ids of  non-bacter ia l  or ig in,  can cause extreme tooth mater ia l  loss especia l ly  i fcombined wi th mechanical  factors in  the mouth.  The best  approach top reven t  t he  p rob lem i s  t o  reduce  the  ac id  cha l l enges  i n  t he  mou th .  Th i s ,however,  poses a problem when deal ing wi th eros ion due to in t r ins ic  factorsas  gas t ro - i n tes t i na l  p rob lems  o r  l ow  pa t i en t ' s  comp l i ance  i n  e ros ion  due  toacid ic  d iets .  Therefore complementary prevent ive measures such as f luor ideapp l i ca t i ons  have  been  p roposed .  Commerc ia l l y  ava i l ab le  f l uo r i de  p roduc tshave been developed for  the purpose of  car ies prevent ion and t reatment ,and fundamental  d i f ferences ex is t  between the car ies and erosionprocesses.  For  th is  reason research should focus on understanding theDrocess of  eros ive wear In order  to choose the f luor ide oroducts best  su i tedfor  i ts  prevent ion.Chapter  1 g ives an overv iew of  the processes involved in tooth wear,Erosion assumes a centra l  ro le and is  therefore d iscussed in more deta i lthan the other  wear Drocesses.  Prevent ive measures for  eros ive tooth wearare rev iewed,  wi th a par t icu lar  in terest  in  the use of  f luor ide and theconsiderat ions that  need to be made when choosing a par t icu lar  compound.The interact ion between mechanical  factors in  the mouth,  the erodedename l  and  the  f l uo r i de  p roduc ts  and ,  i n  pa r t i cu la r  t he  wea r  res i s tance  o fthe products,  seem important  points to take in to account  when select ingf luor ide products for  wear prevent ion.  However,  l i t t le  is  known about  theperformance of  the avai lable topical  f luor ide products under wearcondi t ions.  Therefore,  the a im of  the research descr ibed in th is  thesis  wasto  eva lua te  t op i ca l  f l uo r i des  i n  t he i r  ab i l i t y  t o  p reven t  e ros i ve  wea r  and  tounderstand thei r  mechanism of  act ion.  Subsid iary a ims were to evaluate theinteract ion between enamel  eros ive wear and mechanical  factors in  themou th  and  the  va l i da t i on  a  new me thod  fo r  ename l  wea r  ouan t i f i ca t i on .The pathology of  enamel  eros ion involves superf ic ia l  demineral isat ioncausing the loss of  the outermost  enamel  sur face.  In  addi t ion,  d i f fus ion ofe ros i ve  agen ts  i n to  t he  ename l  a l so  causes  subsu r íace  demine ra l i sa t i on  a dthe format ion of  a sof tened layer .  Al though i t  is  known that  the sof tenedlayer  is  very suscept ib le to d isrupt ion by mechanical  factors such asr42SUMMARYbrush ing  ab ras ion ,  t ongue  f r i c t i on  and  a t t r i t i on ,  t he  ex ten t  o f  damagecaused by these factors had not  been compared before.  This is  an importantmat ter  to  be considered in the development  of  prevent ive measures forerosive wear prevent ion and was therefore invest igated in  the f i rs t  par t  oft h i s  t hes i s  (Chap te r  2 ) .  Fo r t y  two  bov ine  ename l  samp les  we re  randomlyd i v i ded  i n to  7  g roups  (n  =  6  pe r  g roup )  and  submi t t ed  t o  3  cyc les  o f  one  o ft he  fo l l ow ing  reg imens :  e ros ion  and  rem ine ra l i sa t i on  (e r l r em in ) ;  t oo thb rushab ras ion  and  rem ine ra l i sa t i on  (ab r / rem in ) ;  e ros ion ,  t oo thb rush  ab ras ionand  rem ine ra l i sa t i on  (e r l ab r l r em in ) ;  a t t r i t l on  and  rem ine ra l i sa t i on(a t l r em in ) ;  e ros ion ,  a t t r i t i on  and  rem ine ra l i sa t i on  (e r l a t l r em in ) ;  s lmu la tedtongue  f r i c t i on  and  rem ine ra l i sa t i on  ( t g l r em in ) ;  e ros ion ,  s imu la ted  tonguef r i c t i on  and  rem lne ra l i sa t i on  (e r l t g / rem ln ) .  E ros ion  took  p lace  i n  ademine ra l i sa t i on  so lu t i on  (50  mM c i t r i c  ac id ,  pH  3 )  f o r  10  m in  unde rcon t ro l l ed  ag i t a t i on  (  100  rpm) .  B rush ing  ab ras ion ,  t ongue  f r i c t i on  anda t t r i t i on  we re  s imu la ted  fo r  1  m in  us ing  a  home-made  wear  dev i ce .Remine ra l i sa t i on  was  ca r r i ed  ou t  i n  a f t i f i c i a l  sa l i va  f o r  2  h .  Ename l  l oss  wasquan t i f i ed  us ing  op t i ca l  p ro f i l ome t r y .  One -way  ANOVA ind i ca ted  a  s i gn i f i can td i f ference between the amounts of  enamel  lost  due to the d i f ferent  wearreg imes  (p  <  0 .001 ) .  Mu l t i p l e  compar i sons  w i th  Bon fe r ron i  p rocedu reshowed  tha t  t he  wea r  dep ths  f ound  fo r  t he  e r l a t / r em in  (p  <  0 .001 )  ande r l t g l r em in  (p  <  0 .001 )  we re  s ign i f i can t l y  h ighe r  t han  the  amoun t  f ound  fo rthe  e r l r em in  g roup  (4 .4  + .0 .7  pm) .  Th i s  was  no t  t he  case  fo r  e r l ab r l r em ing roup  (p  =  0 .075 ) .  The  resu l t s  sugges ted  tha t  t he  t h ree  fo rms  o fmechanical  insul ts  remove the sof tened layer  formed by erosion to vary ingex ten t .  Th l s  resu l t ed  i n  t he  hypo thes i s  t ha t  a  m ine ra l  g rad ien t  ex i s t s  i n  t heso f tened  l aye r ,  w i t h  t he  ou te r  pa r t  mos t  demine ra l i sed  and  consequen t l ythe most  f ragi le .The resul ts  obta ined in Chapter  2 conf i rm the f ragi l i ty  of  the sof tened layerand ra ise important  quest ions concerning the quant i f icat ion of  eros ive wearsuch as:  Are contact  methods appropr iate for  eros ion quant i f icat ion? And,  i fthe re l iab i l i ty  of  contact  methods such as prof i lometry is  in f luenced byposs ib le  damage  o f  t he  so f tened  l aye r  by  t he  s t y l us  o f  t he  equ ipmen t  wh i chcomes  i n  con tac t  w i t h  t he  samp le  du r i ng  the  scann ing  o f  t he  su t face ,  i s  t h i sdependent  on the wear regimen appl ied? The answers to these quest ions. | 4 5are found in Chapter 3, where the performance of an opt ical  prof i lometerand a contact prof i lometer in the quant i f icat ion of enamel loss under 3dif ferent wear regimens was evaluated. In this study eighteen bovineenamel samples were divided into 3 groups and submitted to 3erosion/remineral isat ion, erosion/brushing abrasion/remineral isat ion orerosion/tongue fr ict lon/remineral isat ion cycles. Erosion was model led byimmers ion  o f  the  samples  in  a  deminera l i sa t ion  so lu t ion  cons is t ing  o f  50  mMci t r i c  ac id  (pH 3)  fo r  10  min  under  cont ro l led  ag i ta t ion  (100 rpm) .  Brush ingabrasion and tongue fr ict ion were simulated for 1 mln using a home-madewear device. Remineral isat ion took olace in art i f ic ial  sal iva for 2 h. Enamelloss was quant i f ied using opt ical  prof i lometry and contact prof i lometry andthe methods were compared, One-way ANOVA showed no signi f icantdi f ferences for the wear depths obtained with the two prof i lometers. Thetwo methods were highly l inearly correlated (r  = 0.95).  Least-squares l inearregress ion  ana lys is  y ie lded a  y - in te rcept  o f  -  0 .78  (95o/o  C. I . :  -2 .08  to  0 .52)and a  s lope o f  1 .14  (95% C.L :  0 .95  to  1 .33) .  A l though a l l  samples  howedscratches on the enamel surface after contact prof i lometry,  the resultsindicated that the prof i lometer stylus penetrated only the very surface ofthe softened enamel.  The scratch depths were inversely related to the weardepths what seems to conf irm the previous hypothesis about themorphology of the softened layer.  Nevertheless the use of non-contactmethods for erosion quant i f icat ion seems preferable and opt ical  prof i lometryis considered a feasible method for that purpose.The second part  of  this thesis focuses on the invest igat ion of f luor idecompounds capable of remineral is ing the softened layer and thereforel imit ing the extent of enamel loss. Based on the knowledge obtained inChapters 2 and 3 on the disrupt ion of the softened layer by mechanicalfactors, we selected f luor ide products that may provide chemical andmechanical  protect ion of the suface.In Chapter 4, the effect of 1 and 47o titanium tetrafluoride (TiF4) gels,amine f luor ide (AmF) to/o and 0.25o/o and a f luor ide varnish (FP) on theprevent ion of dental  erosion was evaluated. Two experlmental  groupsserved as controls,  one with no pretreatment,  and another one pretreatedr44SuvvnnYwi th  a  f l uo r i de - f ree  va rn i sh  (FP-b l ) .  Den ta l  e ros ion  was  mode l l ed  us ingbov ine  ename l  samp les  submi t t ed  t o  a l t e rna te  cyc les  o f  ac ld  exposu re  i nc i t r i c  ac id  and  rem ine ra l i sa t i on  i n  a r t i f i c i a l  sa l i va .  Ca l c i um loss  o f  a l l  samo lesinvolved in the study was quant i f ied by atomic absorpt ion spectroscopy anderosion depths were est imated.  Two samples of  each exper imenta l  groupwere  a l so  ana l ysed  by  wh i te  l i gh t  con foca l  m ic roscopy .  The  cumu la t i veerosion depth ( in  ; rm) af ter  72 min was:  T iF+ gel  I  o /o 8.29 t  0 .39;  T iF+ gel  4o / o  8 . 2 7  t  0 . 5 5 ;  A m F  1 %  8 . 6 9  r  0 . 6 6 ;  A m F  0 . 2 5 o / o  8 . 8 6  r  0 . 3 3 ;  F P  3 . 4 3  !L07 ;  FP-b l  14 .86  t  1 .59  and  con t ro l  9 .77  x  0 .49 .  A  s ta t i s t i ca l l y  s i gn i f i can tprotect ive ef fect  (p < 0.001)  was found only for  the group pretreated wi ththe  f l uo r i de  va rn i sh .  W i th in  t he  l im i t a t i ons  o f  an  i n  v i t r o  s tudy  i t  wasconc luded  tha t  t op i ca l  app l l ca t i ons  o f  t he  f l uo r i de  va rn i sh  t es ted  have  aprotect ive ef fect  on the prevent ion of  denta l  eros ion.Since erosion is  rare ly  the only factor  contr ibut ing to denta l  wear,  i t  isimportant  to  know whether  the f luor ide products tested in  Chapter  4 canwi thstand the chal lenge of  mechanical  factors in  the mouth.  In  Chapter  5,s ingle professional  appl icat ions of  4o/o t i tan ium tet raf luor ide (T iF4) ,  Lo/oamine  f l uo r i de  (AmF)  and  0 .1oÁ  d i f l uo ros i l ane  va rn i sh  (FV)  we re  eva lua tedin  t he  p reven t i on  o f  wea r  due  to  comb ined  e ros ion  and  b rush ing  ab ras ion .One  hund red  and  e igh t  bov ine  ename l  samp les  we re  used .  Con t ro l  g roupswere not  pret reated wi th any product  (C) ,  pret reated wi th a f luor ide- f reeva rn i sh  (FV-b l )  o r  p re t rea ted  w i th  f l uo r i de  va rn i sh  and  subsequen t l ysubmit ted to varn ish removal  (FV-r) .  Wear was model led submit t ing thef luor ide and contro l  groups to 3 cyc les of  the fo l lowing regimens:e ros ion / rem ine ra l i sa t i on  (e r l r em in ) ,  ab ras ion / rem ine ra l i sa t i on  (ab r l r em in )or  eros ion/abrasion/remineral isat ion (er labr / remin) .  Erosion was s imulatedby  immers ion  o f  t he  samp les  f o r  10  m in  i n  c i t r i c  ac id  50  mM (pH  3 )  unde rag i t a t i on  (100  rpm) .  Ab ras ion  was  ca r r i ed  ou t  f o r  1  m in  (200  s t rokes ,  l oad150  g )  i n  a  wea r  dev i ce .  Remine ra l i sa t i on  (2  h  a r t i f i c i a l  sa l i va )  t ook  p lacebetween the cyc les.  Two-way ANOVA showed that  there was a s igni f icantin teract ion (p s 0.001)  between the f luor ide t reatments and the wearregimens.  Under er l remin a s igni f icant  wear protect ive ef fect  was found forthe FV,  FV-r  and FV-bl  groups.  Abr / remin resul ted in  some enamel  loss forthe TiF+ and AmF groups,  however the amounts were not  s tat is t ica l ly1,45s ign i f i can t  (p  =  0 .185  and  P  =  1 .000  respec t i ve l y ) .  Unde r  e r l ab r l r em in  a l lproducts showed a s igni f icant  protect ive ef fect  except  T iF4.  I t  was concludedtha t  FV  and  AmF can  p ro tec t  bov ine  ename l  aga ins t  wea r  due  to  comb inederosion and brushing abrasion in  v i t ro.A  s tep  fu r the r  i n  t he  d i rec t i on  o f  a  c l i n i ca l  app l i ca t i on  was  taken  w i th  an  i ns i fu s tudy where the f luor ide product  wi th the best  in  v i t ro per formance wasstudied under more real is t ic  condi t ions.  In  Chapter  6,  a s tudy on the ef fecto f  f l uo r i de  va rn i sh  (FV)  i n  t he  p reven t i on  o f  wea r  due  to  e ros ion  andcomb lned  e ros ion  and  too thb rush  ab ras ion  i s  reoo r ted .  E leven  vo lun tee rswore  fo r  3  weeks ,  du r i ng  wo rk ing  hou rs ,  app l i ances  con ta in ing  2  con t ro l  and2  FV- t rea ted  human  ename l  samp les .  E ros ion  took  p lace  ex t rao ra l l y  3  t imesa  day  (5  m in )  i n  t he  so f t  d r i nk  Sp r i t e  unde r  con t ro l l ed  ag i t a t i on  (100  rpm) .At  the end of  each exper imenta l  day one contro l  and one FV sample (C-e r+ab r  and  FV-e r+ab r )  we re  b rushed  (5  s )  w i t h  f l uo r i da ted  den t r i f i ce .  Therema in ing  con t ro l  and  FV  samp le  (C -e r  and  FV-e r )  we re  l e f t  unb rushed .Ename l  vo lume  l oss  was  quan t i f i ed  by  op t i ca l  p ro f i l ome t r y  a t  day  5 ,  10  and15 .  A  s ta t i s t i ca l l y  s i gn i f i can t  p rog ress ion  i n  ename l  l oss  was  found  fo r  t he  C -e r ,  C -e r+ab r  and  FV-e r+ab r  g roups  (p  <  0 .001 ,  p  <  0 .001  and  p  =  0 .001 ,respec t i ve l y )  bu t  no t  f o r  t he  FV-e r  g roup  (p  =  O .OS: ) .  The  va lues  o fcumu la t i ve  no rma l i sed  vo lume  l oss  ( x  103  pm)  a t  day  15  were :  C -e r  5 .53  t2 .14 ;  C -e r+ab r  5 .70  !  2 .07 ;  FV-e r  0 .79  !  0 .67  and  FV-e r+ab r  2 .76  t  1 .35 .The FV-er  and FV-er+abr groups showed s igni f icant  lower volume loss thanthe  C-e r  g roup  (p  <  0 .001  and  p  =  0 .005 ,  respec t i ve l y )  and  the  C-e r+ab rg roup  (p  <  0 .001  and  p  =  0 .002 ,  respec t i ve l y ) .  The  resu l t s  i nd i ca ted  tha tf luor ide varn ish is  ef fect ive in  the reduct ion of  eros ive wear.Al though the in  v i t ro and in s i tu  s tudies prov ided much informat ion on theperformance of  the tested f luor ide products,  thei r  exact  mechanism ofact ion in  eros ive wear prevent ion remained to be expla ined.  To c lar i fy  th isma t te r  a  more  fundamen ta l  app roach  was  taken  i n  t he  s tudy  desc r i bed  i nChapter  7,  where the morphology of  the f luor ide- t reated enamel  sur faceswas  i nves t i ga ted  w i th  SEM.  I n  t h i s  s tudy  th i r t y - s i x  bov ine  ename l  samp leswere  randomly  d i v i ded  i n to  18  g roups  o f  two  samp les  each .  Th ree  g roups  o fsamp les  (une roded ,  5  m ln  e ros lon  and  15  m in  e ros ion )  we re  ass igned  tot46S U M M A R Yeach of the controls (untreated samples (C) and samples pretreated with af luor ide-free varnish (FV-bl))  and to each of the fol lowing f luor ide products:t i tanium tetraf luor ide solut ion (TiF4-s),  t i tanium tetraf luor ide gel (TiFa-g),1Vo amine f luor ide (AmF) and f luor ide varnish (FV). Erosion took place in ademinera l i sa t Íon  so lu t ion  cons is t ing  o f  c i t r i c  ac id  50  mM (pH 3 .0)  undercont ro l led  ag i ta t ion  (100 rpm) .  A  th in  sec t ion  was prepared f rom eachsample. The sect ions were cryo-f ixated and subsequent ly fractured in l iquidnitrogen at -  196"C. The suface and fractured surface were analysed withSEM. The micrographs of the eroded C samples showed the fragi leappearance of the intrapr ismatic rystals.  The fractured surfaces showedd isso lu t ion  o f  the  c rys ta ls  a t  the  pr ism boundar ies  up  to  approx imate ly  3and 5 pm beneath the surface after 5 and 15 min erosion, respect ively.Appl icat ion of TiF4 resulted in the formation of a dense surface layercomposed part ly of  sheet- l ike mater ial  and globular structures, which werest i l l  v is ible after erosion. The acidi ty of the products produced howeverdemineral isat ion at pr ism junct ions up to approximately 3 pm from thesurface. AmF appl icat ion resulted in a thin amorphous layer formed on thesurface, which was almost completely removed after 5 min erosion. Theappl icat ion of FV resulted in the formation of a varnish layer approximately2 pm thick on the surface of the samples, which became porous aftererosion. The results helped to explain previous f indings on the per-formanceof TiF4, AmF and FV under erosive condit ions, however further physical  andchemical analysis of the f luor ide-treated surfaces before and after erosivewear seems necessary to further clar i fy the mechanism of act ion of theDrod ucts.In Chapter 8 the cr i t ical  points of the methodology and f indings arediscussed. I t is pointed out that the rn vi t ro and in si tu models used tosimulate the wear processes, al though not able to reproduce exact ly thephenomena that occur in the oral  environment,  were helpful  for theevaluat ion of the extent of softened layer damage by the di f ferentmechanical  factors and for the test ing of the f luor ide products undersimulated wear condit ions. The importance of choosing f luor ide productsthat combine chemical and mechanical  protect ive propert ies is stressed andIt  is suggested that the wear resistance of the products is the determinant7 4 7factor  in  thei r  per formance.  F inal ly  some suggest ions for  fu ture research areg i ven .  Conce rn ing  the  f l uo r i de  va rn i sh ,  i t  seems  necessa ry  t o  improve  i t smechan i ca l  r es i s tance  o r  a l t e rna t i ve l y  cons ide r  a  mu l t i l aye r  app l i ca t i on  o fthe product .  The development  of  h igher  pH TiF+ products is  a necessarydeve loomen t  i n  o rde r  t o  eva lua te  t he  t rue  wear  i nh ib i t i on  o f  t h i s  compound .With respect  to  the indiv idual  var iat lon found in the in  s i fu  s tudy repor ted inChapter  6,  i t  seems interest ing to explore the inhib i t ion potent ia l  o f  thesa l i va ry  pe l l i c l e  i n  t he  p rog ress ion  o f  e ros ion .  Top i cs  l i ke  pe l l i c l emodi f icat ion and l ts  in teract ion wi th the sof tened layer  can provide valuablein fo rma t i on  i n  t he  deve lopmen t  o f  ev idence  based  app roaches  fo r  e ros i vewear  o reven t i on .148

Erosive enamel wear and the inhibiting effect of topical fluorides

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Erosive enamel wear and the inhibiting effect of topical fluorides

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