Limits...
The dentin organic matrix - limitations of restorative dentistry hidden on the nanometer scale.

Bertassoni LE, Orgel JP, Antipova O, Swain MV - Acta Biomater (2012)

Bottom Line: Research has shown, however, that this interaction imposes less than desirable long-term prospects for current resin-based dental restorations.Finally, we discuss the relation of these complexly assembled nanostructures with the protease degradative processes driving the low durability of current resin-based dental restorations.We argue in favour of the structural limitations that these complexly organized and inherently hydrated organic structures may impose on the clinical prospects of current hydrophobic and hydrolyzable dental polymers that establish ultrafine contact with the tooth substrate.

View Article: PubMed Central - PubMed

Affiliation: Biomaterials Science Research Unit, Faculty of Dentistry, University of Sydney, United Dental Hospital, NSW, Australia. luiz.bertassoni@sydney.edu.au

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MMP-1 as a model for MMP driven collagenolysis. (i) The MMP cleavage site is buried in a narrow cleft at the fibril surface. (ii) MMP access to collagen degradation is thought to require C-telopeptide removal for full enzyme access (top), as illustrated in the bottom image. Removal may not have to result in cleavage, however, it may be possible for the enzyme to squeeze into the cleft if the C-terminal region is moved due to extrinsic events affecting the packing arrangement of the fibril, such as in cases of thermal motion, bending of the fibril or putatively demineralization with strong acids, such as the phosphoric acid conditioner of adhesive systems. (iii) Longitudinal view of collagen molecular packing illustrating the MMP cleavage site (cyan) partially covered by the C-telopeptide region (green). (iv) Higher magnification view of (iii). (Modified from Orgel et al. [62].)
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f0030: MMP-1 as a model for MMP driven collagenolysis. (i) The MMP cleavage site is buried in a narrow cleft at the fibril surface. (ii) MMP access to collagen degradation is thought to require C-telopeptide removal for full enzyme access (top), as illustrated in the bottom image. Removal may not have to result in cleavage, however, it may be possible for the enzyme to squeeze into the cleft if the C-terminal region is moved due to extrinsic events affecting the packing arrangement of the fibril, such as in cases of thermal motion, bending of the fibril or putatively demineralization with strong acids, such as the phosphoric acid conditioner of adhesive systems. (iii) Longitudinal view of collagen molecular packing illustrating the MMP cleavage site (cyan) partially covered by the C-telopeptide region (green). (iv) Higher magnification view of (iii). (Modified from Orgel et al. [62].)

Mentions: The MMP molecule contains one catalytic domain, a flexible bridging component, which links the two “ends” of the molecule, and a substrate recognition C-terminal domain. The molecular model of the collagen–MMP interaction was developed based on the assertion that the active site of the MMP is a groove running across the surface of the catalytic domain [49] (Fig. 6). However, it has been determined that the active catalytic site of the MMP molecule is only 0.5 nm wide [114], and is therefore unable to accommodate the entire diameter of an intact collagen triple helix, which measures roughly 1.4 nm. Therefore, it has been hypothesised that MMPs may first bind to and then locally unwind the triple helix so that each peptide may fit into the active site binding groove, before hydrolysing the peptide bonds of each chain in succession [114]. However, the above mentioned study demonstrated that the entire collagen region where cleavage begins, namely the α2 chain within a narrow solvent-accessible cleft, is located in a region that is fully protected by the C-telopeptide (Fig 6). Therefore, access by MMPs to the cleavage site on the native (unchanged) collagen structure is greatly restricted [49].


The dentin organic matrix - limitations of restorative dentistry hidden on the nanometer scale.

Bertassoni LE, Orgel JP, Antipova O, Swain MV - Acta Biomater (2012)

MMP-1 as a model for MMP driven collagenolysis. (i) The MMP cleavage site is buried in a narrow cleft at the fibril surface. (ii) MMP access to collagen degradation is thought to require C-telopeptide removal for full enzyme access (top), as illustrated in the bottom image. Removal may not have to result in cleavage, however, it may be possible for the enzyme to squeeze into the cleft if the C-terminal region is moved due to extrinsic events affecting the packing arrangement of the fibril, such as in cases of thermal motion, bending of the fibril or putatively demineralization with strong acids, such as the phosphoric acid conditioner of adhesive systems. (iii) Longitudinal view of collagen molecular packing illustrating the MMP cleavage site (cyan) partially covered by the C-telopeptide region (green). (iv) Higher magnification view of (iii). (Modified from Orgel et al. [62].)
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3473357&req=5

f0030: MMP-1 as a model for MMP driven collagenolysis. (i) The MMP cleavage site is buried in a narrow cleft at the fibril surface. (ii) MMP access to collagen degradation is thought to require C-telopeptide removal for full enzyme access (top), as illustrated in the bottom image. Removal may not have to result in cleavage, however, it may be possible for the enzyme to squeeze into the cleft if the C-terminal region is moved due to extrinsic events affecting the packing arrangement of the fibril, such as in cases of thermal motion, bending of the fibril or putatively demineralization with strong acids, such as the phosphoric acid conditioner of adhesive systems. (iii) Longitudinal view of collagen molecular packing illustrating the MMP cleavage site (cyan) partially covered by the C-telopeptide region (green). (iv) Higher magnification view of (iii). (Modified from Orgel et al. [62].)
Mentions: The MMP molecule contains one catalytic domain, a flexible bridging component, which links the two “ends” of the molecule, and a substrate recognition C-terminal domain. The molecular model of the collagen–MMP interaction was developed based on the assertion that the active site of the MMP is a groove running across the surface of the catalytic domain [49] (Fig. 6). However, it has been determined that the active catalytic site of the MMP molecule is only 0.5 nm wide [114], and is therefore unable to accommodate the entire diameter of an intact collagen triple helix, which measures roughly 1.4 nm. Therefore, it has been hypothesised that MMPs may first bind to and then locally unwind the triple helix so that each peptide may fit into the active site binding groove, before hydrolysing the peptide bonds of each chain in succession [114]. However, the above mentioned study demonstrated that the entire collagen region where cleavage begins, namely the α2 chain within a narrow solvent-accessible cleft, is located in a region that is fully protected by the C-telopeptide (Fig 6). Therefore, access by MMPs to the cleavage site on the native (unchanged) collagen structure is greatly restricted [49].

Bottom Line: Research has shown, however, that this interaction imposes less than desirable long-term prospects for current resin-based dental restorations.Finally, we discuss the relation of these complexly assembled nanostructures with the protease degradative processes driving the low durability of current resin-based dental restorations.We argue in favour of the structural limitations that these complexly organized and inherently hydrated organic structures may impose on the clinical prospects of current hydrophobic and hydrolyzable dental polymers that establish ultrafine contact with the tooth substrate.

View Article: PubMed Central - PubMed

Affiliation: Biomaterials Science Research Unit, Faculty of Dentistry, University of Sydney, United Dental Hospital, NSW, Australia. luiz.bertassoni@sydney.edu.au

Show MeSH
Related in: MedlinePlus