FRONZA  BM*1,  AYRES  APA1,  PACHECO  RR1,  AMBROSANO  GMB1,  BRAGA  RR2,  RUEGGEBERG  FA3,  M  GIANNINI1    1  Dentistry  School,  State  University  of  Campinas,  Piracicaba,  Brazil    

2  Dentistry  School,  University  of  São  Paulo,  São  Paulo,  Brazil  3  College  of  Dental  Medicine,  Georgia  Regents  University,  Augusta,  EUA    

 *bruna.fronza@hotmail.com  

OBJECTIVES  

MATERIALS  AND  METHODS  

     The  aims  of  this  study  were  to  investigate  the  polymerization  shrinkage  stress  (PS)  and  the  influence  of  depth  on  biaxial  flexural  strength  (FS)  and  elastic  modulus  (MO)  of  four  bulk-­‐fill  and  one  regular  composites.  The  hypothesis  tested  were  that  (1)  the  bulk-­‐fill  composites  would  have   lower  PS  values;   (2)   there  would  be  no  difference   in  mechanical   properties   at   different  depths   for  bulk-­‐fill   composites,  while   to   the   conventional   composite  these  properties  would  be  reduced  with  increasing  depth.  

Herculite  Classic  Kerr  

Tetric  EvoCeram  Bulk  Fill  Ivoclar  Vivadent  

Filtek  Bulk  Fill  3M  ESPE  

Sure6ill  SDR  Flow  Dentsply  

EverX  Posterior  GC  

Group H Group S Group E Group T Group F

RESULTS  

  FS   at   different   depths   did   not   present   statistically  

significant   differences   for   all   bulk-­‐fill   composites,  

suggesting  an  uniform  polymerization   throughout   the  

material.   In   general,   MO   of   the   top   disc   was   higher  

than  that  located  at  the  bottom  for  all  materials  tested.  

  Regarding   PS,   values   observed   for   most   bulk-­‐fill  

materials  were   similar   to   the   regular   composite.   Only  

one  bulk-­‐fill  composite  showed  lower  PS.  

Acknowledgement: FAPESP (2013/05247-4)

#2197  

0.5  mm  1  mm  

1.5  mm  2  mm  2.5  mm  

3  mm  3.5  mm  

4  mm  

a

b

b b

c

Disc-­‐shaped  specimens  (0.5  thickness  x  6  mm  diameter)  were  fabricated  using  a  set  of  eight   Teflon  molds,   simulating   a   polymerization   depth   of   4  mm.   Composites   (n   =   8)  were  light  activated  according  to  manufacturers`  instructions.  These  procedures  were  performed  in  a  light-­‐proof  room  with  controlled  temperature  of  21o  C.    

Specimens   dimensions   were   measured   and   each   disc   was   tested   in   the   piston-­‐ring  biaxial  test  coupled  to  universal  testing  machine  at  1.27  mm/min  until  failure.  Maximum  load  was  recorded  for  each  specimen,  and  elastic  modulus  was  determined  from  the  linear  portion  of  each  stress/strain  curve.      

Polymethyl   methacrylate   rods   with   4   mm  diameter   were   used   as   substrate.   Surfaces  were   sandblasted   with   alumina   particles  followed   by   silane   and   resin   bond.   The  composites   (n   =   5)   were   inserted   between  them  with  space  fixed  at  0.8  mm,  determining  a   volume   of   6.8   mm3   (C-­‐Factor:   1.3).   An  extensometer  was  a-ached  to  the  rods  and  the  composite   was   light-­‐ac6vated   for   10   seconds.  Force   development   was   monitored   for   10  minutes   from   the   beginning   of   light-­‐ac6va6on  and  the  maximum  nominal  stress  was  calculated  (MPa)   by   dividing   the   maximum   force   value  recorded  by  the  cross-­‐sec6on  of  the  rods.