Geometric factors affecting dentin bonding in root canals: a theoretical modeling approach.
Cavity configuration factor (C-factor) is the ratio of the bonded surface area in a cavity to the unbonded surface area. In a box-like class I cavity, there may be five times more bonded surface area than the unbonded surface area. During polymerization, the volume of monomers is reduced, which creates sufficient shrinkage stresses to debond the material from dentin, thereby decreasing retention and increasing leakage. The important variables influencing bonding adhesive root-filling materials to canals was examined using a truncated inverted cone model. C-factors in bonded root canals exhibit a negative correlation with sealer thickness. For a 20 mm-long canal prepared with a size 25 file, calculated C-factors ranged from 46 to 23,461 with decreasing sealer thickness (500-1 microm), compared to a C-factor of 32 when the canal was filled only with sealer. As the thickness of the adhesive is reduced, the volummetric shrinkage is reduced, which results in a reduction in shrinkage stress (S-factor). C-factors above 954 calculated with sealer thickness smaller than 25 microm are partially compensated by increases in bonding area and decreases in shrinkage volume. However, the interaction of these two geometrically related factors (C- and S-factors) predicts that bonding of adhesive root-filling materials to root canals is highly unfavorable when compared with indirect intracoronal restorations with a similar resin film thickness.
Tay
Franklin R
FR
Faculty of Dentistry, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
Loushine
Robert J
RJ
Lambrechts
Paul
P
Weller
R Norman
RN
Pashley
David H
DH
D017609:Barium Compounds; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D001840:Dental Bonding; D018772:Dental Marginal Adaptation; D003799:Dental Stress Analysis / Q000379:methods; D003804:Dentin; D006801:Humans; D007180:Incisor; D008689:Methacrylates; D008962:Models, Theoretical; D012387:Root Canal Filling Materials; D012389:Root Canal Obturation; D012822:Silicon Dioxide
C121035:Aeliteflo; D017609:Barium Compounds; D003188:Composite Resins; D008689:Methacrylates; D012387:Root Canal Filling Materials; C486893:epiphany sealer; C486892:resilon sealer; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide