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Abstract

Spatial and temporal control is a key advantage for placement and rapid setting of light-activated resin composites. Conventionally, placement of multiple thin layers (<2. mm) reduces the effect of light attenuation through highly filled and pigmented materials to increase polymerisation at the base of the restoration. However, and although light curing greater than 2. mm thick layers is not an entirely new phenomenon, the desire amongst dental practitioners for even more rapid processing in deep cavities has led to the growing acceptance of so-called "bulk fill" (4-6. mm thick) resin composites that are irradiated for 10-20. s in daily clinical practice. The change in light transmission and attenuation during photopolymerisation are complex and related to path length, absorption properties of the photoinitiator and pigment, optical properties of the resin and filler and filler morphology. Understanding how light is transmitted through depth is therefore critical for ensuring optimal material properties at the base of thick increments. This article will briefly highlight the advent of current commercial materials that rationalise bulk filling techniques in dentistry, the relationship between light transmission and polymerisation and how optimal curing depths might be achieved.
Shining a light on high volume photocurable materials

 !"   ! #$ %&#'
! !  %#$ ( )$&
$  $%  &  *&+ $  , "    *,"+
#$ ( )$&&
 -
& !
#$ %&
 !
"   !
& !. 
/%
0 
&&/10
233454366//31
233454366//35
Abstract
!   7%$    8 $ 
 $ %     %*95 +     
   %   %    
  :$    5 7%  %:
     $$ 
 : 8;7< *386 7+   
 4=85=% >    
 % ?          
    %# :
           
7 > :%   $      
  7    )     %      :    
% :   $
Contents
4= "  
5=      
54      $  
55        &8 :
554  $ %
555      
55@   $ 
553    
@= >;78<
3= 0     
/=
1.0 Introduction
A% $  %8  % %
 :$ % $   
 %% $$   )% $
         :        
   7   @8     
  %
> %  %7% $ $ 
               " %    
        %  7    %  
    7             : 
:$  $     $ *#B+       C   
%#B "   %   *4D1=+:
 : #B   C % :  ? E@6/
%C8% *E@3=8@F=+ 
) C>  6=  E4/
*1/=G%"!H + 7%  :*/=? 
%   0     I  A 4+       $ %    :   >% "
      :$ > #B8 
 : $% $ %    %8
>%""   : %C %:% $*+
      :$ : %
 $ %    )*
  ?      
+$? -16J #B8
  %  418%K4L @=8
%:8 C     : $  
661J @=%:  44JK5L> :7
 - 8   8 %8   :    5 %
) :8 :8 %8 
A4-!   % *?@6/+: 0
*?3//+ E5=4===M5 $%
A % %          $ %    $  
           :$    
    %%7        
   %:      
$    >  $     7     
  %    :%     :   %
$    :$   $ )
                        %
   $ 
0? $      $  
  $8 $    
       :      %  )$
              % 8
;78<    )    
$ >?  ? $ $  % 
      8$  :
   "   % $:   
       C 7  )    %    :
 :                
 %C :        $
  
2.0 Curing light transport through depth
54     $  
>   %C        
?  %  %      %   >
     ?received by a surface  *M5+: 
     ?    % %
        
     *  :7    : K@L %   %
         7  
0$  $ %    
  *   ? ; 8 < 
  +  %*  $ %+C * 
:$    :   +K3/LN :   
 $      :
 7   ?    / 7
O7P*&A+   *1D5QFD=JI>4+
Irradiance / mW.cm-2
Mould
Thickn
ess
(mm)

      
high
power
LED
(without
material
)
1










2162
(7.6)a
 











 









3








1848
(2.0)b
 









 











4










1468
(1.6)c
 









 









Recommended thickness (mm) 
>4-   * 33F+  :O$ P *,+O78P*&A+ %:    4
@ 3 7&A4R:$ %  I&A583 R$ %  :  @)$ ?
&A4   : 6 : %8  : 3 
 %        7N    
:  , 4,5*  5 + : &A % *?+   ,
  3 7$    >   &A  
?  %        %   8      4  @ 
 &A@&A3I     *! 553+N8  
%8:%NHB 8>7%*9==/+ %  :   7
"     :         
:  7       
 !    %   %
           * % ?     
   ?   $  +: 
 ?        A      
  : *>4I 44=
6=  +    % ?  :      
  *! 555+    7 K6L
% %  $ ? :        *! 
553+:$  %8 ;78<  
$ %  ?  %%*&A@&A
3I>4+      "   
$  :  %*  + %  : 
  % $ $%$
:   *A5@+"    %    
      $  K1FL:  %
$  O7 P         %C     %  : 
 7  $$ 3 
: 4$   %$ 
*E4==I A 5+   7  $8   > ?    
  :   ? : $       $ >
 $ @6=* +:  ?  
       :: ) $
   *A5+A:4=?,4 
 $ 3:  %:    4 7:
?   $       :     :  
?     5:$,5  $
 3: 4:4=?:    7 &A
583:  $  )          
$ :7      O7P  7 53   ? KD 4=L
    :7     $     $  $  
  *7+   7         K44L :  %  7 8
  %: : ? > &A4 3
:*A5+  :  $ *:
+
A5- $   $ * +  : 4 7 3 7*6  : 
%+$  *,+         *>,+A> %*A>",!+ 
  4=@6=* % % + $ : %   
  *46@F84+          *4/DF 84  46=F 84+ %  $    $
:  7 $ ? $$ 
3
 !"#$%
 !"#$%

A@-$  $* + :4 73 7*6 : %
+ O78P*&A+           *>,+8A>",!    4=  * %   +
 $: %     *46@F84+      *4/DF
84 46=F84+
55       &8 :
>     : :  7 ? %
&8 P :      :        
:    $%K45843LI
IZ=I=(4=εCz)
*4+
:Iz    zI0   *CR=+  
 $ %Cz         z#  $  
 *+           
:      ?        
   :   :  
# )    $ 
  $ * % +     
:$%:  :   K4/LI
∂ I (z , t )
∂ z =−
[
εiCi
(
z , t
)
+Am+εpCp
(
z ,t
)
]
I(z , t )
*5+
:Iz   z t
i  $ %    Ci(z,t)
         z t Am    
   % *  $   + 
p    $ %  %
  Cp(z,t)         %   z   t>
:! 5548553 $: 0) 5  
   %
2.2.1 Molar absorptivity
:  %       $ :$      $ %
*?   +         7
 :$   $  ? :
$     
     %C % :
%  $% 
        K4/L > 7  >%""
   ) *S+  7      $ % $  
    :%    88 8       
N$         %   % 
  >% "     :    :$  % :    
 $ %%?>I  %:
S  $    > 
 $ $ : $ %* 
  :$                
 80  +  $  %C   :  $%
 $     K4/46L>   
   :  $  $%               >%  "    >%  ""
    $ 7*A3+ S*:   %8  58
* %+ % %   JS+%?*H+
           %     %      
     :  :$   : 
         *3=/ 36F  H  S  $%I
A/+>    $   H:  S
%     *94=+ 7  5*A/
/ $%+:     % $ % H*A @+
:$ %        *:         
  +%      % : :7
:     :$  ?  *A//+
:          "  ? SM>H     %   )$
 * 36F3=/ $%+:    
% :?      :    
  :7    ?  %  S>H  :
       ::  7
*A/  /+ "   %C  %  ?    
 $ %H: $  %         %
      : :7     S: 
      #      %       
$  % % 8  $  
   %     $    
   :   $   
 *T3+:  S>H   *A6+>
   :   :$ >
?   % : $%   $ %  )  %    : 
: :$ : %    : 
   :$  >  
    7%  :    
: $ %* SM0+ 0$  S    
     $       %C  : >H  
  : $K41L     :%
$: %   *T@A6+:  $
      :   $ %*>H+K4FL" 
) % $ %: %*E5+
?   >H   : % 
%          K4D5=L>
$   A6:     8  
            :    
 $   0$      $
  ? %              
$  %  %) %>H  3=/
>    >H %   $ %:$ 
  :      :  $ % $     
% %     $ :   : 
   
A 3- >         :8       *  #!+ :  7     3=/    36F   
       % ?*H+  ) *S+ $% H ? 
  %     $ %   :   :7      S >    :$  ?      
8;%:$<* +    3=/  %: 
$
A /->        *>+ + % ? *H+   3=/ + ) 2 58
* %+ % % *S+ 36F+SMH 3=/+SMH 36F>
:       ==4@38@*)+   / 7*4
5@36I  : >+ #B8B  % )K41L0 :  7:$ 
 3=/ 36F *A3+ : >       E4/== 85 6= *>: 
 $   7: )$ :     +         %
    $ $    : 7*   + 
     K6L
A  6- >         $ *R@+                     %  * 
SM0>H  +:$  * 36F3=/? $%+ A/, 
: : 6=M3=:M: M  6=$J4G  *//$J+==/G 
*/$J+ $:, %*1F=/3==M +%   
  R 463=84:$     R 46=F 84   >
 ::  %$*4/M5+
$ :7                 $ %
   K4F4D54LH $ $ ::
 $ %     :         % ? 
    % S  K555@L >    : $     %
$   3SM>H:  S
*A/+ : )  3=/ :   %  
8;%:$<* +     
   " %  *! 55+ ?  $  
$       *A 6+ N :          
 * 3=/+:   :$ 
       %% $  
*5 7:4:71/J  +: S8
  5=K53L
 ?   $    
    C%    $ $  !%        C%  %  
C% %88 *>%"+  % : : 
  8 $ %  )  % *           
  I=F/: =//8=/D%?K5/L =4=S8
% K56L+     K51L!% 
   $ $  8*38 ?%C%+ %  :        5==D    
"$U*"$8B$   +K5FL
2.2.2 Photoinitiator concentration
>     %   * 8:+
              %C    
$        ?              
     *0) 5+      
? K434/5D8@3L   $   
:$:$     :
   ::       
 ::   :$ 
K43L"     % %   
  ?     % $      
$  %0) 45 %I
Ri
(
z , t
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=5ϕεiCi
(
z ,t
)
I(z , t )
 *@+
:
Ri
(
z , t
)
      z t
ϕ
 ) 
%     K4/L  %    %C *t</+    
  :          :
:       ?   *A1I  
 5==5K4/L+ $*tR5//=+   
         $%    
  %:$  ?  
  *A 1 + >  % 7:  O%C  :$  P 
  $       7% ? O 
 %C P *  %    %C  K@/L+    %
        $ % *      :$   :  
Ci

εi
+%C  7    K4/5D
@= @@L                  
 ::          
:  *A6+,    ? 
 ?       
   : %       
   $ %:       
%C          :$       
   $  % $      %C  $
  $ :     7  K@5@6
@1L  ?    ) 
 *%T5= :   7%E4=85=+
A1->   :           *-=4@3=5=: JI   -==/@1
 =F : JI :- ==56F  =3 : J *  %  :   %  %   +  I *+ /  *+ 5/   *+ /=
   4=85I) %=5I $ %D118484*  5==5K4/L+
!$    ?    $
$      $    :    
   8    $ $K@F834L
2.2.3 Competitive light absorbers
> %  ? :C    :$ : 
   $   %     
     "  %     8   %   
    % :35=/5= K35L   
  Am  0)  5  %   :$   
 % %   :    %     :$ 
*
pCp 0) 5+$ % %C    :
 $% $ $    %    
       K413@L : %       
   %C     7  K33L
"       
  %?*%:+  ? 
 *+   *AF+> $% % 
 ?)*?E31=IAF+: $7
   *AF+     % 
%    OP *    +     K3/L   
 ?  :   *AF+> C
   : $  %
  %:   ? K36L  ? 
    *! 53+H $$%% 
8 %  :$ $  % %C  : 
     $       %  :  $ 
   :    $ 
! ?  :$     
:   )K31L
A F- *+ >%    V             *+ >        
:  $  )?           
  *+>    %     * 31=
+  *+    $    :       *"!H3=3DI5==D K3FL+    $%
  K @! #!L
2.2.4 Light refraction and scattering
>)%8   $% C 
%   %$%E/=8
F/J* V $ %:8O:P   +K3DL 
   :  :  $
                ?   
7: :  ? %8 :$ 
 E=58=@ K/=8/@L :$  ?     %  
$      C    :     C *9 /== + 
  8C  % ? A     C : 
  *T 4= +::     :  ? 
  !     O78P    $ %   
%  K/38//L
! ?  )  
? $   %   
%8   %%C , * % +
         :  : 
 * :$    +, $? 
:     :   $
 : $4@6= :  $>?    
 :  $%!P:, : 
   C   $? : 
 "  $? %7: *:
         +          
 >         %:
 :$   $ ?      %C   :  
  %%  %  
 *! 4>4+ %:  $ 
8? " :     
  % :%C K/6L:%$ 
8   $  : % O78P
 
3.0 The era of “bulk-fill”?
> %  $% %C      3 Q/  
 %$ % %   $ 
: $ 5 7 :$O78P :! 
 4DD= $7  :  / *>5+$
 $ 78 : $$%
 / K/18/FL %  8  
      $  7    * /  +  $  
$   % ) $7%C $
:$    "!H3=3D OP  *=/  
   +  %    *F=J+          
?     %  $         K/D864L $  @8   /8%
      78    $       
: $  5 K656@L
 :   %      $
  :  $        : $ %  >  
)  $ %   :  $ :   
  %%))% % *   
 %+          % 7    $
V               ?      
  $? :  % %
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@#3&(!###1((#&*1&#;#,&7&&13#&
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
2 !A1&#;143#&4-5 mm
>5-!?      7 $   :   
/ %       "!H3=3DI  ;  P4DFF*   7OP 
$%5+     5===
    $       : %C 
   $ %                 %
K63L     $ ?   
$  )    7   >   
$    % ):
% $      
* O  P+ ?  8
  " ? 8   :$ % : 
  :  %$ ? : 
$ % K6/866L  $   
: $  *>5+    $     $  $   
%C       $  %    $ 
 7 A? $:  %
 %7:       
 $  %$$  $  
$ % $   %C   7  
: $  K61814L   %C  *$
$ +  %: $$%   K63L::%$
 $ O7:P  $ 
K15L :$       $     $          
%C  $ 7 A7 :
7 $%   ? :     
  $   $  ? &7  
? : : $ O8%P % 
 $$   %K1@L:% 
$%C  $? 7 
  $  8      : 7 
   % 8  % :7  $ %:    
  :7  %  7  % K13L !    7% $$ 
   %      % 8  %  % 
:$%  %C  K1/16L   
  % 8  %7  
     :7         %C 
 7   8 $: K11L
4.0 Emerging and potential future technologies for deep photocuring
N :    C     $    %     
   $      *!  5+  $ $
   $    %C   *5=46+
K1FL$    %   : $% 7*+
F/  E44=M5 *3=/ + 5= "  $      
 ? *>+  :       $     
  %?    %C  $ %* 3=/+
    >:$%:! :7 :  
  % % 7 *D+:
%):    
 %C   :  8
$:    *E1=J E/=J$ 
: F  $%+   %
?):7%  %  
   $   %%:: :$%
 )
!,% $%    ::$  :
    ?   :   :$  * % #B8   
 I! 4+" :         :$ :$
     A?   *",+
    :8   %C       V   ? $     
$  $*  + >:   $
$   :  $ #B        %  
    K1DL:$ )
      : 8
     
$$ $*#+   $ 8",% 
 :$ * 8! 7 +#B$     A  
  :     :7,% ",
: $ #  :$    
:   $ $    )*SI
? E31=+0 % #        8   
   S>$$   $   :5
# $   $E6=J  
4@1NWA3-4FJW=/J>KF=L! 7 *5=45+KF4L 
  $*S  +M *6=M3=+: # 
*NWA3: W>+ 4=  : DF=: 
       3==8/== :$ % )  
 $ %C :%-46=M5 DF=",?  $
# ==/GM5A  $ %C  : $
8",      DF= 
:$ :   $ *6F56 $%+
"$         
    C      * ?  
     :$ + :           
)%  A  8 ;7< 
         "    %
   %    % % C$% 7 
% :$       %    )
?H :  *%  +   
8?  :  %*%+'?
 8     KF5L>)
:$ ?%$%:%
 !8;8<%   $ 8? 
$             :7  %  
    ?       ! %P  $  %
  )8  :$     %C  :% 
 %   $%KF@L 8    
:     >        
%C  $$   ?  %           
  :  $% :?>
   %  *    $ :$  +    
?C  $     ? EF=J
$*0+   E45= : ? :  $  
 :EFJ,7%E45 70::
@3M56=:   $ $   "  
   $ SM   %  
     $ C $       $ 
 :4= :  $ ?% KF@L> 
     %       ?   $ 
 :  $    *     ?    
$    ! 54IA5+  
  * % + %    %    ? %    
 $        %        
                %    
$   % :$    $    % 
 %$ 7  KF3L
5.0 Conclusions
 %C    % 4D1=  )$ 
  $      %
   ;78<        %:  
   ?   $: 
   $ $      7  
    $ %$$   
  %  ?        % %   %   
      %         
 %7   8 :  %
% :         :  %   
  ,      %            $ 
 %C   $:     ? 
    7   : %   %
   
Acknowledgements
>   H?'*@! #!+
           %    *!  55@I
AF+! %*#$ %#!+
              %C         *#$ %  
&#'+%7:   
$   *!  54I A 5  @+ > %      
 % 7:   $      *  +    
N%IH 5=41
References:
K4L%'N&%!>%A'A!$ 8% %
 $ 8  """  0 ,  4DDDI44-4@/8435
K5L#$V7C @=%: $ 
 ""    5=4/I@4-45@584533
K@LX!:,>7
   -  %:8$  %!5=46I@4-
1FD8F=D
K3L,&,AA?" $ *3=/+
*36=+    0  ,  5=4=I55-@6@8
@11
K/L ,&>,A A?" %   
   0  ,  5=4=I55-F684=@
K6L !  !     $
   5=45I5F-44/3864
K1LV  $ &%       $  - ?
 %  5==@I4D-/@48/34
KFL! $?
? %:  5=44I@D-/3D8//1
KDL,X!N!  : !7N 8 $ 
    %78$   5=4/I3@-5=D8
54F
K4=L 8  '  " N  !7  N     %C   7        
%C  $ 78 %$  
  5=4/I@4-45=18454@
K44L >S % 78 -
%8   5=46I@5!-D4
K45L     ;    $               <
*  %   + %416=
K4@L&;&    A7 *  
    )+<%4F/5I465-1FQFF
K43LP,'7%"  %C -0?  %
 ,5==4I46-@/@68@/33
K4/LN%B!      
 7%C % %!- %5==5I3=-1D@8F=F
K46L H   "     @83 "-  %C 0I H
%!*5==3+54F8553
K41L!   $   $ 8
   5=45I5F-F@48F34
K4FL! A$?   
% %? %:  $  
5=44I51-4/18463
K4DL   B!   8,    %      $  
          % %:$   :$ 0  
 5=45I3=-4=684@
K5=L N    !      >      ?        
% %!5==DI445-45D84@3
K54L V$Y$X7$Y"$V$Y8Y" $N 
B0 :87 % %?   
% ? 8  !0
 &5=46I/F-3F18D3
K55L  H$ , "&A !  >   
     %         8   
 5=46I@5-45=D841
K5@L ! B0& $   ,,! A 0     
                0  , 
 5=4/I51-!4-!348F
K53L, &!$?C& # 8
 8  :   $      
5=43I@=-/D386=3
K5/L  &A #' C N 7 , N:  $   %8
   $ 5==FI34-5@D3853==
K56L   W8  A      !  S   %  $         
)  5==1I5@-6//8663
K51LCNA#' &7,,B&C%$ $
$$        5==FI53-D=48D=1
K5FL C N A #' !C # 7 , &  X A   &  
% X C  %$  "   #!8 
16=/4D=&5*5=4=5==D+08  4D=/34/&4*=4=15==D+"$B$ 
K5DLB  %   H'> "    
 %C :$5=4/I3F-4DF85=/
K@=L ' N! A7 &   !  & !    $   
     7%%  %%  - 
   0%%" 5==FI/1-44@38443=
K@4L>A :$ :7 % %5==/I
36-35@=83534
K@5L !  N '7  08C:  !   !    $   
     7%%   %" 5==/I/3-435D8
43@D
K@@L&:N$ $ %C 
     70!5==5I/1-FF18D==
K@3L>    0             
      %C 5==4I@3-@4D/8@5=3
K@/LN ,>%V#B8 %C   
* +% 5==/I@F-//=68//45
K@6L  &77 ''  !  &   %C  )      
$%5==4I35-3@48334
K@1L"$$B7'  %    %C %" 5==4I/=-
44@844F
K@FL H%7    !   )       %   
$?      
5==1I5@-F=18F4@
K@DL  V    A    !7  ,                
         5==DI5/-DD38
4===
K3=L  !  A    !7  ,  &  ,,            $
 -          $     7   $   7  
%C   5==DI55-5=6854=
K34L Z > ! A & ,,  !  )  
$            %   :   %  %    SM
   5=43I@=-45138451D
K35L!7B    %C 
   % 8         :   )M  "      
  0%5==DI3/-/4/8/55
K3@L)),,$ !A  %
$:   %   :     
%  5=4@I34-61815
K33L!B  %C  % 
    : %8458M     -  5==DI 5=5-
55F85@3
K3/LV$&8   8  $   
5==6I55-F=38F41
K36L '!CNN:     
5==/I4@6-5483/
K31L!!! !8 %  8
?:" 05==5I34-415D841@5
K3FL"!H3=3D5==D  %Q%  $ 5==D
K3DL ,A    
  %8   5=46I@5-4/F684/DD
K/=L,% "0[%\$   $ $  $ 
   H !4DF5I3=-41D84D5
K/4L A7 >0 H   $8   $        8
 $   ,4DFDI6F-4/@384/@D
K/5L     !  H  &    0N  !   #B8B       
 %   5==1I5@-15381@=
K/@L ! & ,B A,!$0A:0   
   5==FI53-/148/16
K/3L" N& ! &788 - $   
H 5=4@I@F-64F865/
K//L  &   ! "  N         8       7    $
$  H"$ 5=43I4F-4DD485===
K/6L !     &   , $ ?       $ %
   ,5==FF1-F38FF
K/1L  !  &! B % 0> %    7 
$   8  -  5===I4@4-464=8
464/
K/FLW & %C 7    7
 S " 5==/I@6-5/8@
K/DLWN$A%C 7 7
: H 5=43I@D-334833F
K6=LA%!%C! C    - "!H
3=3D  7 ]  5=45I5F-/548/5F
K64L$)N% &C&$?N:    
 % 8    5=45I5F-/458/5=
K65L V7#C   %$  78 
    %  5=43I@=-53/85/4
K6@LV7# 78   -/8%
  % 5=46I/4-5D8@/
K63LA >%    Q   % ]   
5=46I@5-484=
K6/L&,, >A   :   
% 8$% 5==@I4@3-154815F
K66L ! A  "&"     
7 % 7   8   
5==1I5@-4=D@844==
K61L08% % 7 7   
78 H 5=43-@D-@138@F5
K6FLAB&? > V!AB?? 
78: H 5=4/I3=-/4/8/5@
K6DL>&B7%!> V!AB?
   %7   5=43I@6-36F831@
K1=L % H: %&A & ,A 
 7       :  78 : 8   
  5=45I3=-/==8/=/
K14LB07B% ' $B7&&7
  8  $ -     $ %8     
5=4@I5D-56D8511
K15L$? % 8 
  %%  5=4@I5D-4@D84/6
K1@L         B7   !    $?        %8
  %$78  5=43I35-DD@84===
K13L'?! >A&:N! ? $ 8  
 8% 5==DI35-5//485//6
K1/L7W'?! >A&:A$   :7   $
-!  ? %  8    % 8 
  5=4=I56-4=4=Q4=46
K16L 7 W '?  % ! H?   &: N !  ?  $
 8         Tg    $   % 8    % 
5=45I3/-/63=8/636
K11L ! ' ! %   &: N      8  8
  * +%   :7  %  7 
%5=41IF-3@@D-3@/4
K1FL 8!$%A A$H8$  $ 
MC% ? ?    % - )  $  :  
 %C 5=46I3D-D@148D@F4
K1DL ! %"$@ : %- ? 
    5=46I@5-/3863
KF=L   ,    X)    !  A    ^   0? %    %C   
$  %5=46I1-53/18536@
KF4L! 7,NX''AA! 7#N",
 $ %  5=45I5F-@=38@44
KF5L $ &   !    % 4= 0  5=4F *  + 
 #' 4/_1
KF@L8!  B8   %  8  %C 
$58M42 -"  :   % !5=43I4@6-134F8
1351
KF3L ''$ ! % 8 $ 7  %   
5=41I@@!-48D5*   %   N%
H 5=41I -MM?M4=4=46MV 5=41=F4/5+
... Due to their composition and chemical, physical and aesthetic imperatives, the most common forms of most dental resins must be laminated in 2 mm layers to ensure proper polymerization. The 2 mm polymerization depth is a general characteristic of dental composite resins, except when specific properties, such as bulk-fill capabilities or self- curing mechanisms, are present, which can modify this parameter [37][38][39][40]. Figure 1 shows a schematic representation of the structure of a classic resin composite before and after polymerization. ...
... Due to their composition and chemical, physical and aesthetic imperatives, the most common forms of most dental resins must be laminated in 2 mm layers to ensure proper polymerization. The 2 mm polymerization depth is a general characteristic of dental composite resins, except when specific properties, such as bulk-fill capabilities or self-curing mechanisms, are present, which can modify this parameter [37][38][39][40]. Figure 1 shows a schematic representation of the structure of a classic resin composite before and after polymerization. Figure 1. ...
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The adhesive–resin composite pair has been the cornerstone of direct restorations in dentistry for many years. Resin composites are traditionally classified in three ways based on their inorganic structure, their organic composition and their viscosity. While these classifications have long been associated with the optical, mechanical, and clinical properties of resin composites, recent studies indicate that this classification is not always valid. In recent years, a significant expansion of the range of clinical resin composite families has occurred, each with varying degrees of validation through in vitro and clinical studies. As a result, new resin composites with distinct structures, viscosities, and clinical indications have emerged. Despite this progress, a formal classification of the clinical features of all resin composites is still lacking, leading to terminological inconsistencies in research and potential confusion among clinicians. This brief review, supported by an exhaustive search of the dental literature, proposes a new clinical classification system for resin composites based on their key clinical features to help clinicians and researchers easily identify the key clinical characteristics of formulations. This modular classification, encompassing eight main families and 14 characteristics, is particularly suited to future developments, as current trends aim to simplify procedures by integrating multiple formulations into single products.
... DOC is a key parameter of DRCs, directly impacting their curing effectiveness. A notable feature of BF-DRC is its ability to deliver incremental fillings of 4 mm to 5 mm in a single treatment session, thereby reducing the clinical operation time [30]. Insufficient curing depth can cause more material to leach from poorly cured resin at the base of the filling, potentially irritating soft tissues and dental pulp, promoting bacterial growth, and triggering allergic reactions [31]. ...
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This study aimed to enhance the performance of dental resin composites (DRCs) by increasing the content of inorganic fillers while addressing potential health risks associated with Bisphenol A (BPA). To achieve this, the BPA-based resin monomer Bis-GMA was replaced with BPA-free Bis-EFMA. The study then explored the impact of varying inorganic filler contents on the physiochemical properties of Bis-EFMA-based bulk-fill dental resin composites (BF-DRCs). Four distinct Bis-EFMA-based BF-DRCs were formulated, each with different inorganic filler contents ranging from 70 wt% to 76 wt%. The study tested the depth of cure (DOC), double-bond conversion (DC), water sorption (WS), solubility (SL), and cytotoxicity of the system. It notably investigated the effects of increasing filler content on mechanical properties through flexural strength (FS), flexural modulus (FM), Vickers microhardness (VHN), and wear resistance, as well as the impact on polymerization shrinkage, including volumetric shrinkage (VS) and shrinkage stress (SS). To assess the commercial application potential of Bis-EFMA-based BF-DRC, the research used the commercially available BF-DRC Filtek Bulk-Fill Posterior (FBF) as a control. The results indicated that a higher filler content did not affect the DOC of Bis-EFMA-based BF-DRCs. Inorganic fillers at higher concentrations significantly enhanced overall mechanical properties while significantly reducing volumetric shrinkage (VS; p < 0.05). When the concentration of inorganic fillers in the resin system reached 76 wt%, most of the performance of the Bis-EFMA-based BF-DRC surpassed that of the commercial control FBF, except for FS, FM, and SS. These findings highlight the potential of Bis-EFMA-based BF-DRC as a long-term restorative material for dental applications.
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Purpose To evaluate the effect of thermo mechanical cycling on gingival microleakage of bulk fill composite versus conventional one. Patients and methods A total of 32 noncarious human premolar teeth were mounted in acrylic blocks (only roots were embedded). Class II cavities were prepared with the following dimensions the occlusal cavity was 3 mm in depth and 2 mm in width buccolingually, the dimensions of the proximal box were as follow, the gingival wall was 1 mm above the cemento-enamel junction, the axial wall height was ~3 mm, the axial wall depth was 2 mm. Specimens were randomly divided into two equal groups (16 each) according to the restorative material, for group I tetric N-ceram composite was used and for group II tetric N-ceram bulk fill composite was used. Half of the specimens in each group were then subjected to 500 thermal cycles from 5 to 55°C with 30 seconds(s) dwell time, and 20 s transfer time and then subjected to 120 000 cycles of loading with a force of 60 N, frequency of 2 Hertz and displacement of 1 mm by using a chewing simulator machine, The other half of the specimens were left without thermal or load cycling. All surfaces of the teeth except 1 mm around the margins of restoration were sealed with two layers of nail polish. Then, the teeth were immersed in 0.5% basic fuchsin solution for 48 h. All specimens were then sectioned in the mesio-distal direction through the center of restorations using isomet saw to detect dye penetration by the stereomicroscope. The recorded data was collected, tabulated, and statistically analyzed using SPSS version 26. Results There were no significant differences among the gingival microleakage of both types of composite in both unloaded and loaded groups. Conclusions Thermal and load cycling did not affect the gingival microleakage of class II cavities restored with composite by bulk filling technique or those restored with the incremental technique.
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The first seconds of light curing are crucial for the development of most properties of dental composites, especially for the 3s high-irradiance curing. This study investigated the influence of rapid high-irradiance curing on temporal development of temperature, transmittance and conversion of bulk-fill composites. Four materials were tested: Filtek One (FO), Tetric PowerFill (PFill), Tetric PowerFlow (PFlow) and SDR flow+ (SDR+) and cured with three curing units (LCU): Valo Cordles, Bluephase PowerCure and Translux Wave in 3s (3 W/cm²), 10s (1 W/cm²) and 20s (1 W/cm²) curing protocols. Light transmittance was measured at 2 and 4 mm, while temperature rise and polymerisation kinetics were evaluated at 4 mm depth during 5 min. Both light transmittance and temperature rise were greatest for SDR+ > PFlow > PFill > FO. The 20s curing protocol resulted in the highest degree of conversion (DC) for all materials and LCUs, but also contributed to the greatest temperature rise. Rapid curing with the 3s protocol caused the lowest temperature rise and the shortest time to reach maximum temperature. The polymerisation and temperature kinetics were strongly dependent on the material. The DC of PFill was statistically similar for 3s, 10s or 20s curing with BPC. Rapid curing is only recommended for materials developed for this purpose.
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Lasers and light-emitting diodes are used for a range of biomedical applications with many studies reporting their beneficial effects. However, three main concerns exist regarding much of the low-level light therapy (LLLT) or photobiomodulation literature; (1) incomplete, inaccurate and unverified irradiation parameters, (2) miscalculation of ‘dose,’ and (3) the misuse of appropriate light property terminology. The aim of this systematic review was to assess where, and to what extent, these inadequacies exist and to provide an overview of ‘best practice’ in light measurement methods and importance of correct light measurement. A review of recent relevant literature was performed in PubMed using the terms LLLT and photobiomodulation (March 2014–March 2015) to investigate the contemporary information available in LLLT and photobiomodulation literature in terms of reporting light properties and irradiation parameters. A total of 74 articles formed the basis of this systematic review. Although most articles reported beneficial effects following LLLT, the majority contained no information in terms of how light was measured (73 %) and relied on manufacturer-stated values. For all papers reviewed, missing information for specific light parameters included wavelength (3 %), light source type (8 %), power (41 %), pulse frequency (52 %), beam area (40 %), irradiance (43 %), exposure time (16 %), radiant energy (74 %) and fluence (16 %). Frequent use of incorrect terminology was also observed within the reviewed literature. A poor understanding of photophysics is evident as a significant number of papers neglected to report or misreported important radiometric data. These errors affect repeatability and reliability of studies shared between scientists, manufacturers and clinicians and could degrade efficacy of patient treatments. Researchers need a physicist or appropriately skilled engineer on the team, and manuscript reviewers should reject papers that do not report beam measurement methods and all ten key parameters: wavelength, power, irradiation time, beam area (at the skin or culture surface; this is not necessarily the same size as the aperture), radiant energy, radiant exposure, pulse parameters, number of treatments, interval between treatments and anatomical location. Inclusion of these parameters will improve the information available to compare and contrast study outcomes and improve repeatability, reliability of studies.
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Objectives: To investigate a bulk-fill flowable base composite (Surefil SDR Flow) in terms of cuspal flexure and cure when used in incremental or bulk techniques. Methods: Mesio-occluso-distal cavities (4 mm deep, 4 mm wide) were prepared in 24 extracted molars. The slot-shaped cavities were etched, bonded, and restored in 1) two 2-mm increments Esthet-X HD (control), 2) two 2-mm increments Surefil SDR Flow, or 3) 4-mm bulk Surefil SDR Flow (N=8). The teeth were digitized after preparation (baseline) and restoration and were precisely aligned to calculate cuspal flexure. Restored teeth were placed in fuchsin dye for 16 hours to determine occlusal bond integrity from dye penetration. Extent of cure was assessed by hardness at 0.5-mm increments through the restoration depth. Results were analyzed with analysis of variance and Student-Newman-Keuls post hoc tests (α=0.05). Results: Surefil SDR Flow, either incrementally or bulk filled, demonstrated significantly less cuspal flexure than Esthet-X HD. Dye penetration was less than 3% of cavity wall height and was not statistically different among groups. The hardness of Surefil SDR Flow did not change throughout the depth for both incrementally and bulk filled restorations; the hardness of Esthet-X HD was statistically significantly lower at the bottom of each increment than at the top. Conclusions: Filling in bulk or increments made no significant difference in marginal bond quality or cuspal flexure for the bulk-fill composite. However, the bulk-fill composite caused less cuspal flexure than the incrementally placed conventional composite. The bulk-fill composite cured all the way through (4 mm), whereas the conventional composite had lower cure at the bottom of each increment.
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Objective: The mechanical properties of dental resin-based composites (RBCs) are highly dependent on filler characteristics (size, content, geometry, composition). Most current commercial materials are marketed as "nanohybrids" (i.e. filler size <1μm). In the present study, filler characteristics of a selection of RBCs were described, aiming at identifying correlations with physico-mechanical properties and testing the relevance of the current classification. Methods: Micron/sub-micron particles (> or <500nm) were isolated from 17 commercial RBCs and analyzed by laser diffractrometry and/or electron microscopy. Filler and silane content were evaluated by thermogravimetric analysis and a sedimentation technique. The flexural modulus (Eflex) and strength (σflex) and micro-hardness were determined by three-point bending or with a Vickers indenter, respectively. Sorption was also determined. All experiments were carried out after one week of incubation in water or 75/25 ethanol/water. Results: Average size for micron-sized fillers was almost always higher than 1μm. Ranges for mechanical properties were: 3.7<Eflex(water)<16.3GPa, 86<σflex(water)<161MPa and 23.7<hardness(water)<108.3HV0.2/30. Values generally decreased after storage in ethanol/water (Δmax=86%). High inorganic filler contents (>75wt%) were associated with the highest mechanical properties (Eflex and σflex>12GPa and 130MPa, respectively) and lowest solvent sorption (∼0.3%). Significance: Mechanical properties and filler characteristics significantly vary among modern RBCs and the current classification does not accurately illustrate either. Further, the chemical stability of RBCs differed, highlighting differences in resin and silane composition. Since Eflex and sorption were well correlated to the filler content, a simple and unambiguous classification based on such characteristic is suggested, with three levels (ultra-low fill, low-fill and compact resin composites).
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Objective: To evaluate in a randomized controlled study the 5-year clinical durability of a flowable resin composite bulk-fill technique in Class I and Class II restorations. Material and methods: 38 pairs Class I and 62 pairs Class II restorations were placed in 44 male and 42 female (mean age 52.4 years). Each patient received at least two, as similar as possible, extended Class I or Class II restorations. In all cavities, a 1-step self-etch adhesive (Xeno V+) was applied. Randomized, one of the cavities of each pair received the flowable bulk-filled resin composite (SDR), in increments up to 4mm as needed to fill the cavity 2mm short of the occlusal cavosurface. The occlusal part was completed with the nano-hybrid resin composite (Ceram X mono+). In the other cavity, the resin composite-only (Ceram X mono+) was placed in 2mm increments. The restorations were evaluated using slightly modified USPHS criteria at baseline and then yearly during 5 years. Caries risk and bruxing habits of the participants were estimated. Results: No post-operative sensitivity was reported. At 5-year 183, 68 Class I and 115 Class II, restorations were evaluated. Ten restorations failed (5.5%), all Class II, 4 SDR-CeramX mono+ and 6 CeramX mono+-only restorations. The main reasons for failure were tooth fracture (6) and secondary caries (4). The annual failure rate (AFR) for all restorations (Class I and II) was for the bulk-filled-1.1% and for the resin composite-only restorations 1.3% (p=0.12). For the Class II restorations, the AFR was 1.4% and 2.1%, respectively. Conclusion: The stress decreasing flowable bulk-fill resin composite technique showed good durability during the 5-year follow-up. Clinical significance: The use of a 4mm incremental technique with the flowable bulk-fill resin composite showed during the 5-year follow up slightly better, but not statistical significant, durability compared to the conventional 2mm layering technique in posterior resin composite restorations.
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Although photopolymerization has been versatile in various applications, photopolymerization of thick materials still remains a great challenge due to the light-intensity gradient. In this paper, we report a facile and generic method to realize deep photopolymerization using upconversion nanoparticle (UCNP)-assisted photochemistry. Compared to the reported photocuring depth of several millimeters, 13.7 cm of photopolymerization depth combined with about 60% of double bond conversion is obtained with optimal parameters. The thermal effect during UCNP-assisted photopolymerization is comparable to or weaker than that of some reported frontal photopolymerization used for the preparation of dental filling materials and functional polymer composites. The photocured materials using UCNPs as internal lamps exhibit a similar nanoindentation hardness and reduced modulus to those cured under traditional blue LED light. The presented strategy shows great potential applications in ultra-high density data storage and the preparation of biomaterials.