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Geometric factors affecting dentin bonding in root canals: a theoretical modeling approach
Franklin R Tay1, Robert J Loushine, Paul Lambrechts
1Faculty of Dentistry, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
Journal of Endodontics
|July 27, 2005
Summary
The cavity configuration factor (C-factor) significantly impacts the bonding of root-filling materials. High C-factors, influenced by sealer thickness, create unfavorable conditions for adhesion, potentially leading to debonding and leakage.
Area of Science:
- Dental Materials Science
- Biomaterials Engineering
- Restorative Dentistry
Background:
- Polymerization of dental materials causes volumetric shrinkage, generating stress.
- This shrinkage stress can lead to debonding, reduced retention, and microleakage at the tooth-material interface.
- The cavity configuration factor (C-factor) quantifies the ratio of bonded to unbonded surface areas, influencing stress distribution.
Purpose of the Study:
- To investigate the influence of cavity configuration factor (C-factor) and sealer thickness on the bonding of adhesive root-filling materials.
- To analyze the relationship between C-factor, shrinkage stress (S-factor), and the overall success of root canal obturation.
- To compare the bonding challenges in root canals with those of indirect intracoronal restorations.
Main Methods:
- Utilized a truncated inverted cone model to simulate root canal geometry.
- Calculated C-factors across a range of sealer thicknesses (1-500 micrometers) in a standardized root canal preparation.
- Examined the interplay between C-factor and S-factor to predict bonding outcomes.
Main Results:
- C-factors in bonded root canals showed a negative correlation with decreasing sealer thickness, ranging from 46 to 23,461.
- A C-factor of 32 was calculated for a canal filled solely with sealer.
- High C-factors (>954) with thin sealer (<25 micrometers) were partially offset by increased bonding area and reduced shrinkage volume, but overall bonding remained unfavorable.
Conclusions:
- The geometry of root canals presents highly unfavorable conditions for bonding adhesive root-filling materials due to high C-factors.
- Sealer thickness is a critical variable; thinner sealers lead to higher C-factors and potentially greater shrinkage stress.
- Bonding of adhesive materials in root canals is significantly more challenging compared to indirect intracoronal restorations with similar resin film thicknesses.