An Ultrastructural Study of Bacterial Invasion and Tissue Breakdown in Human Experimental Root-surface Caries

Abstract

This study describes the structural features of the interface between microbial deposits and root cementum in actively progressing root-surface caries lesions developed experimentally in six elderly individuals. A total of 18 specimens was examined by microradiography, and a further 18 by light and transmission electron microscopy after intra-oral periods of one, two, and three months. All specimens showed various degrees of subsurface dissolution of mineral and bacterial invasion of the cementum. Although the microradiographic pattern of mineral loss was subsurface in nature, transmission electron microscopy showed dissolution of crystals in the outermost layers of the cementum, with a distinct gradient inward. Bacterial invasion occurred along the borders between bundles of relatively well-mineralized extrinsic collagen fibers in which the characteristic cross-banding remained intact. The pattern of bacterial invasion was influenced by the incremental lines and the cemento-dentinal junction. The invading bacteria were almost exclusively Gram-positive, of various shapes, and possessed thick, moderately electron-dense cell walls and electron-lucent "vacuoles" in the cytoplasm. It is concluded that because of pronounced mineral loss of the outermost cementum, accompanied by bacterial invasion, the surface of an active cementum caries lesion, as observed by transmission electron microscopy, is not identical to that seen in microradiograms.

Relationship between Mineral Distributions in Dentine Lesions and Subsequent Remineralization in vitro

“…The mineral distribution in active advanced dentine lesions (natural dentine caries), so-called 'softened' type, is quite different from the subsurface type of lesion [Schüpbach et al, 1990]. Finally, degradation of the organic matrix leads to the destructive phase of the dentine caries process [Schüp-bach et al, 1989;Nyvad and Fejerskov, 1990].…”

How ‘Clean’ Must a Cavity Be before Restoration?

“…The dentine in such lesions is infected at a relatively early stage in lesion progression [Nyvad and Fejerskov, 1990]. Despite this, active lesions can be converted to inactive lesions over a period of months by regular cleaning and fluoride application [Nyvad and Fejerskov, 1986].…”

Análise do selamento marginal de restaurações realizadas após remoção de cárie radicular com o laser de Er, Cr:YSGG

“…Pesquisas têm mostrado que as lesões de cárie radicular envolvem tanto a desmineralização quanto a destruição da matriz orgânica da dentina (FRANK, 1990;FEJERSKOV, 1990;LUTZ, 1990). Alguns pesquisadores sugeriram que as fases orgânica e inorgânica são rompidas simultaneamente nas cáries radiculares (FRANK, 1990;FRANK;STEUER;HEMMERLE, 1989;).…”

“…Alguns pesquisadores sugeriram que as fases orgânica e inorgânica são rompidas simultaneamente nas cáries radiculares (FRANK, 1990;FRANK;STEUER;HEMMERLE, 1989;). Outros acreditam que a destruição ocorre em duas fases: uma, em que há a dissolução da porção mineral da dentina por ácidos, seguida pela invasão bacteriana e rompimento ou colapso do colágeno (KATZ; PARK; PALENIK, 1987;FEJERSKOV, 1990;LUTZ, 1989 VAN STRIJP et al, 2003).…”