Microsoft Word - Morieira Proof Feb 11.docx   Vol  3,  No  1  (2015)   ISSN  2167-­‐8677  (online)   DOI  10.5195/d3000.2015.29           http://dentistry3000.pitt.edu     New  articles  in  this  journal  are  licensed  under  a  Creative  Commons  Attribution  4.0  United  States  License.     This  journal  is  published  by  the  University  Library  System,  University  of  Pittsburgh  as  part  of  its  D-­‐Scribe  Digital  Publishing  Program  and  is  cosponored   by  the  University  of  Pittsburgh  Press.   Profile  of  fluoride  release  from  a  nanohybrid  composite  resin   Raquel  Assed  Bezerra  Silva1,  Fernanda  Regina  Ribeiro  Santos1,  Augusto  Cesar  Cropanese  Spadaro2,  Ana  Cris)na  Morseli  Polizello2,  Andiara  De   Rossi1,  Marilia  Rodrigues  Moreira1,  Paulo  Nelson-­‐Filho1     1  Department  of  Pediatric  Clinics,  Preventive  and  Community  Dentistry,  School  of  Dentistry  of  Ribeirão  Preto,  University  of  São  Paulo,  Ribeirão  Preto,  SP,  Brazil   2  Department  of  Physics  and  Chemistry,  School  of  Pharmaceutical  Sciences  of  Ribeirão  Preto,  University  of  São  Paulo,  Ribeirão  Preto,  SP,  Brazil   Abstract   The  aim  of   this   study  was   to   evaluate   in   vitro   the   amount   and  profile  of   fluoride   release   from  a  fluoride-­‐containing  nanohybrid  composite  resin  (Tetric®  N-­‐Ceram)  by  direct  poten1-­‐ ometry.  Thirty  specimens  (5  mm  diameter  x  3  mm  high;  n=10/material)  were  made  of  Tet-­‐ ric®  N-­‐Ceram,  Vitremer®  resin-­‐modified  glass  ionomer  cement  (RMGIC)  (posi8ve  control)  or   Filtek®   Z350  nanofill   composite   resin   (nega8ve   control).   The   specimens  were   stored   indi-­‐ vidually  in  plas,c  tubes  containing  1  mL  of  ar,ficial  saliva  at  37°C,  which  was  daily  renewed   during  15  days.  At  each  renewal  of  saliva,  the  amount  of  fluoride  ions  released  in  the  solu-­‐ !on  was  measured  using  a  fluoride  ion-­‐selec%ve  electrode  with  ion  analyzer,  and  the  values   obtained  in  mV  were  converted  to  ppm  (µg/mL).  Data  were  analyzed  sta=s=cally  by  ANOVA   and  Tukey’s  post-­‐hoc  test  at  a  significance  level  of  5%.  The  results  showed  that  the  resins   Tetric®  N-­‐Ceram  and  Filtek®  Z350  did  not  release  significant  amounts  of  fluoride  during  the   whole  period  of  evalua,on   (p>0.05).  Only  Vitremer®  released  significant  amounts  of  fluo-­‐ ride  ions  during  the  15  days  of  the  experiment,  with  greater  release  in  first  2  days  (p<0.05)   and  stabiliza%on  in  the  subsequent  days  (p>0.05).  In  conclusion,  the  nanohybrid  composite   resin  Tetric®  N-­‐Ceram  did  not  present  in  vitro  fluoride-­‐releasing  capacity  throughout  the  15   days  of  study.       Cita%on:   Silva   RAB,   Santos   FRR,   Spadoro   ACC,   Polizello  ACM,  De  Rossi  A,  Moreira  MR,  Nelson-­‐ Filho  P.   (2015)  Profile  of  fluoride  release  from  a   nanohybrid   composite   resin.   Den$stry   3000.   1:a001  doi:10.5195/d3000.2015.29   Received:  January  1,  2015   Accepted:  February  2,  2015   Published:  February  23,  2015   Copyright:  ©2015  Silva  et  al.  This  is  an  open  ac-­‐ cess  ar!cle   licensed  under  a  Crea!ve  Commons   A"ribu%on  Work  4.0  United  States  License.   Email:  marilia.moreira@ig.com.br     Introduction       The   effect   of   !luoride   on   dental   caries   pre-­‐ vention  appears  to  be  dependent  of  its  con-­‐ stant   presence   at   adequate   levels   on   oral   environment,   which   may   interfere   in   the   dynamics  of  the  carious  lesion  by  a  decrease   in   demineralization   and   increase   in   remin-­‐ eralization   (1,2,3).   Since   the  most   common   cause   of   restoration   failure   in   the   dental   clinic   is   the  occurrence  of   secondary  or   re-­‐ current   caries   around   the   restoration  mar-­‐ gins  (4,5),  the  incorporation  of  4luoride  into   restorative   materials   could   improve   the   success  of  restorative  treatment  (2,6,7).  The   intimate   contact   between   the   restoration   and   the   tooth   margins   may   also   prevent   penetration  of  cariogenic  bacteria  and  acids   and   facilitate   the   exchange  of   /luoride  with   the   hydroxyapatite   (8,9).   Thus,   the   use   of   restorative  materials   that   not   only   release   !luoride,   but   also   have   adhesivion   to   tooth   structure   has   been   suggested   to   prevent   recurrent  caries  around  restorations  and  to   promote   remineralization   of   incipient   cari-­‐ ous   lesions   on   restored   surfaces9   or   even   on  adjacent  teeth  (10).       Although   the   use   of   composite   resins   has   increased   considerably   during   the   last   years,   their   ability   to   release   .luo-­‐ ride   is   low  or   insigni,icant  when  compared   to   other   materials,   such   as   glass   ionomer   cements   (GICs)   (11,12).   Thus,   there   has   been  a  growing  interest  in  the  development   of   newer   composites   resins   with   ef/icient   !luoride   release   abilities   and   improved   physical  and  mechanical  properties,  such  as   lower  polymerization  shrinkage  (9,13,14).  A   novel   'luoride   containing   composite   resin   (Tetric®   N-­‐Ceram,   Ivoclar   Vivadent   AG,   Schaan   -­‐   Liechtenstein)   was   developed   based   on   nanotechnology,   aiming   to   pro-­‐ mote   low   shrinkage   and   shrinkage   stress,   high   level  of  radiopacity,   low  wear  and   fast   polish   ability,   and   high   gloss.   Tetric®   N-­‐ Ceram  is  composed  by  dimethacrylates  and   the  nano-­‐!illers  contain  barium  glass,  copol-­‐ ymers,   mixed   oxide   and   ytterbium   tri1luo-­‐ ride   (YbF2),  which,  according   the  manufac-­‐ turer,   was   added   to   provide   radiopacity,   and  simultaneously  release  /luoride.  YbF2  is   a  well  know  radiopaque  agent  used   for  de-­‐ tection  of  secondary  caries  or  imperfections   like  air  bubbles,  but   its   -luoride   ion  release   ability  in  association  with  nanohybrid  parti-­‐ cles   has   not   been   documented.   It   has   been   hypothesized   that   the   presence   of   nano-­‐ sized  'illers  offers  increased  surface  area  to   volume  and  could  provide  a  quicker  release   of  $luoride  (12).     Since   the   )luoride   release   ef)icacy   of  restorative  materials  is  largely  dependent   on   their   composition   and   setting   reaction   and   nature   of   +luoride   incorporated,   we   conducted  an   in  vitro  study   to  evaluate  hy-­‐ pothesis   that   the   *luoride-­‐containing   nano-­‐ hybrid   composite   resin   (Tetric®   N-­‐Ceram)   can   promote   +luoride   release   compared   with   a   non)luoride-­‐releasing   material   (Fil-­‐ tek®   Z350)   and   high   1luoride-­‐releasing   material  (Vitremer®).       Material  and  Methods      Profile  of  fluoride  release  from  a  nanohybrid  composite  resin   Vol  3,  No  1  (2015)        DOI  10.5195/d3000.2015.29    http://dentistry3000.pitt.edu   2     The   materials   used   in   this   study   were   the   'luoride-­‐containing   nanohybrid   composite   resin   Tetric   N-­‐Ceram®   (Ivoclar   Vivadent   AG,   Liechtenstein),   the   RMGIC   Vitremer®   (3M   ESPE,   St.   Paul,   MN,   USA),   and   the   nano)ill   composite   resin   Filtek   Z350®   (3M   ESPE,   St.   Paul,   MN,   USA).   The   materials   composition   and   manufacturer   are  summarized  (Table  1).         Thirty  specimens  (5  mm  diameter   and   3   mm   thickness)   were   prepared   from   the   three   materials   (n=10)   by   packing   the   material   into   a   custom-­‐made  polytetra,luo-­‐ roethylene  matrix.   The  matrix  was   2illed   at   room   temperature   (approximately   25°C)   and   the   materials   were   mixed   and   light-­‐ activated   according   to   the   manufacturers’   instructions.   The   mass   of   each   specimen   was  recorded  using  a  digital  precision  scale.   Vitremer®  specimens  presented  an  average   mass  of  0.143  g,  while  Tetric  N-­‐Ceram®  and   Filtek  Z350®  specimens  presented  an  aver-­‐ age  mass  of  0.159  g  and  0.140  g,  respective-­‐ ly.       The   specimens   were   stored   indi-­‐ vidually  in  Eppendorf  tubes  containing  1  mL   of  arti(icial  saliva  (School  of  Pharmaceutical   Sciences  of  Ribeirão  Preto,  University  of  São   Paulo,  SP-­‐Brazil)  at  37°C  during  15  days  and   were   daily   re-­‐immersed   in   new   tubes   con-­‐ taining   1   mL   of   fresh   arti0icial   saliva.   The   amount   of   )luoride   released   was   studied   every   24   hours   for   15   days.   Each   sample   was  buffered  with  citrate  0.5  mol/L,  pH  5.5,   and   the   (luoride   measurements   were   per-­‐ formed  by  direct  potentiometry  with  an  ion-­‐ selective   electrode   (Orion   2008;   Thermo   Electron   Corporation,   Orion   Products,   Bev-­‐ erly,   MA,   USA)15.   For   the   measurements,   0.5   mL   of   arti-icial   saliva   were   collected   from  the  plastic   tubes  containing  the  speci-­‐ mens   and  homogenized  with  0.5  mL  of   the   citrate  buffer,  and  the  resulting  solution  was   homogenized   again   right   before   the   meas-­‐ urement  of  *luoride  release.   The  mean  values  among  the  different  study   groups   were   compared   using   one-­‐way   ANOVA   followed  by  multiple-­‐range  Tukey’s   HSD   test   to   identify   the   signi0icant   groups   (p=0.05)   in   the   GraphPad   Prism   4.0   soft-­‐ ware   (GraphPad   Software,   Inc.,   San   Diego,   CA,  USA).  A  signi-icance  level  of  5%  was  set   for  all  analyses.     Results       Results  were   recorded   in  mV   and   converted   into   ppm.   For   such   purpose,   a   standard   curve   was   prepared   using   11   samples   of   solutions   with   different   +luo-­‐ ride   concentrations.   From   this   standard   curve,   the   results   in   mV   were   converted   to   ppm   and   com-­‐ pared   with   the   val-­‐ ues   obtained   from   the   standard   curve.   The   values   of   ,luo-­‐ ride   release   were   tabulated   as  mean   ±   standard   deviations.   As   shown   in   Figure   1,   the   results   of   the   present   study   showed   that,   on   days   1   and   2,   the   mean   value   of   !luoride  release  of  Vitremer®  was  the  high-­‐ est   (p<0.05)   and   then   !luoride   release   stabilized   in   the   subse-­‐ quent   days   (p>0.05).   Tetric   N-­‐ Ceram®   and  Filtek   Z350®   showed   no   de-­‐ tectable   amounts   of   $luo-­‐ ride   release   through-­‐ out   the   experi-­‐ mental  period  and  presented  no  statistically   signi%icant   differences   (p>0.05)   from   each   other.       Discussion       The   advances   in   nanotechnology   have   allowed   the   development   of   novel   composite   resins   with   improved   physical   properties,   high   strength,   good   wear   re-­‐ sistance,   and  excellent  esthetics   (13).  How-­‐ ever,   few   composites   are   reported   to   in-­‐ clude  in  their  composition  0luoride  that  may   be   ef%iciently   released   to   oral   environment   by   ion   exchange   or   hydrolysis   (16).   It   has   been  recently  suggested  that  0luoride  incor-­‐ poration   into   materials   containing   nano   sized  'illers  could  favor  its  faster  release  by   a   higher   surface   area-­‐to-­‐volume   ratio12   Nanocomposites  with   high   strength   can   be   promising  materials  if  they  have  the  capaci-­‐ ty   to   release   *luoride,   phosphate   and   calci-­‐ um  ions  for  the  precipitation  of  0luorapatite   (17).  However,  according  to  our  results,  the   nanohybrid   resin   containing   YbF2   3illers   (Tetric®  N-­‐Ceram)  did  not  present  a  signi0i-­‐ cant   release   of   ,luoride   during   15   days   of   experiment,   having   similar   results   to   those   of   the   negative   control   (a   conventional   hy-­‐ brid   composite).   Our   results   con3irmed   those   of   previous   studies,   which   found   a   constant  low  level  of  -luoride  released  from   different  composite  resins  with  YbF2   !illers   in  their  composition  (18,19).       The  low  (luoride  release  from  cur-­‐ rent   commercially   available   composite   res-­‐ ins   has   been   associated   with   the   low   amount   of   )luoride   incorporated   into   these   materials  as  *illers,  low  solubility  of  YbF2  in   water   (2,10),   low  water   content  of   the  ma-­‐ terial,   and   composite   resin   permeability   Table  1.  Restorative  materials  used  in  this  study.   Material   Manufacturer   Classi&ication   Glass  Ionomer  Ce-­‐ ment  Vitremer®   3M  Dental  Prod-­‐ ucts,  St  Paul,  Min-­‐ nesota,  United   States   Glass  Ionomer  Cement   resin-­‐modi%ied  type  II   Composite  Resin   Tetric  N-­‐Ceram®   Ivoclar  Vivadent,   São  Paulo/SP,   Brasil   Nanohybrid  Compo-­‐ site  Resin   Composite  Resin   Filtek  Z350®   3M  Dental  Prod-­‐ ucts,  St  Paul,  Min-­‐ nesota,  United   States   Nanohybrid  Compo-­‐ site  Resin   Figure  1.  Release  of  0luoride  ions  from  the  three  materials  at  each  day  of   the  experiment.      Profile  of  fluoride  release  from  a  nanohybrid  composite  resin   Vol  3,  No  1  (2015)        DOI  10.5195/d3000.2015.29    http://dentistry3000.pitt.edu   3   (18).  In  addition,  due  to  the  low  solubility  of   YbF2   in  water,   it   is   postulated   that   the   re-­‐ charging   effect   of   ‘.luoride-­‐releasing’   com-­‐ posite   resins   containing   this   agent   may   simply   be   the   release   of   surface-­‐retained   !luoride   (2).   The   incorporation   of   !luoride   into   composite   resins   has   not   shown   any   bene$icial  effect  in  reducing  the  deminerali-­‐ zation   of   carious   lesions   in   roots   when   compared  with  GICs(12,20).       Aiming   to   solve   this   problems,   novel   nanocomposites   containing   alterna-­‐ tive   &luoride   sources   has   been   developed   (13,19,21).   One   alternative   are   composite   resins   containing   nanoparticles   of   calcium   phosphates  (CaF2),  which  may  release  6luo-­‐ ride   ions   that  matched  or  exceeded  report-­‐ ed   releases   from   conventional   GICs   and   RMGICs   (21).   The   mechanical   properties   and   ion   release   of   these   composites   could   be   tailored   by   changing   the   nanoparticle   !iller  level  and  reinforcing  !iller  level.  These   nanocomposites   present   high   release   of   !luoride,   phosphate   and   calcium   ions   for   precipitation   of   ,luorapatite   and   inhibition   of   caries   together   with   good   mechanical   properties.       The   reason   for   the   relatively   high   !luoride   release   from   these   new   CaF2-­‐ containing  nanocomposite  is  likely  the  small   size  and  hence   the  high   surface  area  of   the   nanoparticles19.   Other   alternative   are   ex-­‐ perimental   composites  made   of   novel   1luo-­‐ ride-­‐releasing   monomers,   such   as   ternary   heavy-­‐metal-­‐!luoride   chelates,   which   have   been   developed   based   on   the   hypothesis   that   reduction   of   hydrophilic   monomers   and   improvement   of   photoinitiators   could   reduce   water   sorption   and   signi0icantly   increase   the   mechanical   properties   of   the   composite13.   In   the   study   by   Ling   et   al.   (2009)   (13),   one   of   these   experimental   composites   showed   signi.icantly   higher   !luoride-­‐release   and   recharge   capabilities   than   commercial   -luoride-­‐releasing   compo-­‐ sites,   but   physical   and   mechanical   proper-­‐ ties   were   still   lower   than   those   of   most   commercial  composite  resins.   To  date,  conventional  GICs  and  RMGICs  are     still  considered  the  unique  materi-­‐ als   with   higher   ,luoride-­‐releasing   ability   and   may   be   clinically   indicated   to   restore   decayed  non-­‐biting  areas  in  high-­‐caries-­‐risk   patients.  Several  studies  have  demonstrated   the   ef&icacy   of   these   materials   as   an   addi-­‐ tional  measure   for   preventing   occlusal   car-­‐ ies   lesions   (1,7,10,19,22)  by  means  of   their   ef#icient   #luoride   release   ability,   which   not   only  may  accelerate  mineral  deposition,  but   also  can  change  the  metabolic  activity  of  the   dental  plaque.       In  the  present  study,  Vitremer®,  a   RMGIC,  was  selected  as  the  positive  control   due   to   its  wide  use   in   restorative  dentistry   and   its  broad  clinical   indication.   In   fact,  we   found   that   Vitremer®   had   a   signi2icant   re-­‐ lease   of   (luoride   ions,   especially   in   the   1st   and  2nd  days  of  evaluation.  Our  results  are   in   agreement  with   those   of   a   number   of   in   vitro   studies   that   have   also   shown   higher   !luoride   release   in   the   !irst   24   hours   11,23,24),   with   gradual   decrease   after   48   hours   (12,21).   This   high   initial   4luoride   re-­‐ lease  from  GICs  is  due  to  an  acid-­‐base  reac-­‐ tion,   with   the   amount   of   .luoride   released   proportional   to   the   concentration   of   .luo-­‐ ride   in   the  material.  This   is   responsible   for   the  phenomenon  know  as  the  “burst  effect,”   wherein   high   amounts   of   0luoride   are   re-­‐ leased   during   the   +irst   two   days   (17,20).   Fluoride  release  declines  rapidly  during  the   !irst  week  and  stabilizes  after   three   to   four   weeks  (7,10,22)  as  a  result  of  the  high  initial   release   from   the   glass   particles   that   are   partially  dissolved  in  polyalkenoic  acid  dur-­‐ ing   the   setting   reaction   (18).   An   additional   property  of  Vitremer®  is   its  high  microbial   growth   inhibition   potential   because   it   re-­‐ tains  the  true  characteristics  of  convention-­‐ al   GICs,   unlike   .luoride-­‐containing   compo-­‐ site   resins,  which  do  not  have  antibacterial   activity   (25,26).   Caries   lesions   adjacent   to   the   restoration   are   likely   to   take   from   sev-­‐ eral   months   to   several   years   to   develop.   Thus,   'luoride   must   be   continuously   re-­‐ leased  from  dental  material  for  long  periods   to  help  preventing  the  development  of  new   caries  lesions.         Despite   the   well   demonstrated   effects   of   in   vitro   ,luoride   release   on   the   saliva,   dental   plaque   and   hard   dental   tis-­‐ sues,  clinical  studies  have  shown  controver-­‐ sial  results  with  respect  to  the  actual  clinical   relevance   of   +luoride-­‐releasing  materials   in   preventing  or   inhibiting   the   secondary   car-­‐ ies   development   compared   with   materials   without   capacity   of   releasing   3luoride   ions   (7).  Therefore  further  research  is  still  need-­‐ ed  for  the  development  of  novel  composites   resins   with   *luoride-­‐release   and   recharge   capabilities,   while   maintaining   their   physi-­‐ cal,   mechanical,   and   aesthetic   properties,   which   are   highly   desirable   to   improve   res-­‐ toration   longevity   in   high-­‐caries-­‐risk   pa-­‐ tients.       References     1.   Effects   of   Aged   Fluoride-­‐containing   Re-­‐ storative  Materials   on   Recurrent   Root   Car-­‐ ies.  Hsu  YS,  Donly  KJ,  Drake  DR  &  Wefel   JS.   Journal   of   Dental   Research.   1998;     77(2)   418-­‐425.  PMID: 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