Selvig, KA. Ultrastructural Changes in Cementum and Adjacent Connective Tissue in Periodontal Disease. ACTA Odont. Scand. 24:459, 1966

Aims

The purpose of this investigation was to study at the ultrastructural level the pathologic changes which take place near the root surface in periodontal disease in humans. More specifically, the study was designed to answer the following questions:
1. Can the alterations of the connective tissue fibers near the cementum surface which result in complete loss of their attachment to the tooth in periodontal disease be more precisely characterized at the ultrastructural level ?
2. Do any structural alterations take place within the cementum during this process?

Materials and Methods

• Human teeth which were involved to varying degrees in chronic, destructive periodontal disease were obtained. Cementum was examined by microscopy and electron microscopy.
• Starting with the most apical region, the following zones could be distinguished:
  I) Intact connective tissue fibers attachment to cementum in the apical and middle regions of the periodontal membrane
  II) Partial destruction of the connective tissue fibers. This zone was encountered 0.5 to 1 mm beneath the epithelial attachment and extended to within a small distance from the most apically located epithelial cells.
  III) Complete destruction of the connective tissue fibers in a narrow zone immediately beneath the epithelial attachment.
  IV) Epithelium lining the cementum
• The region of altered cementum was zones II, III, and IV

  Zone I - fibrils ranged in diameters from 500 to 800 A, but thinner fibrils were occasionally present. The individual fibrils were separated by a distance of 200 to 500 A. Collagen fibrils could be traced from the periodontal membrane into the calcified tissue, where they became masked by mineral crystals and ground substance deposited within and around them. The cementum included in the sections was of the acellular variety in all specimens.

  Zone II - (Partly destroyed connective tissue fibers attachment) This was observe some distance from the cementum rather than at the surface of the hard tissue. This change consisted of a slight increase in size of the interfibrillar spaces. Collagen fibrils less than 500 A in diameter could be observed. Bundles of thin fibrils which differed from the typical collagen fibrils in several respect were apparent between the collagen fibrils. The distance between the component fibrils increased to 1000 A or more. The tissue space between the loose bundles of collagen fibrils contained varying amounts or granular or fibrillar debris. In the more extensively altered regions, however, all structural elements seemed to loose their functional orientation. The number of intact fibrils attached to the cementum decreased rapidly toward the cervical direction, leaving the cementum surface denuded.

  Zone III - (Completely destroyed connective tissue fiber attachment) This is just below the most apical cells of the epithelial attachment no collagen fibrils or microfibrils could be traced from the periodontal membrane into the cementum. Granular and agranular leukocytes as well as unidentifiable cells were abundant in this region. In some of the specimens the denuded cementum surface had a wavy to smooth outline, in others the surface appeared more irregular.

  Zone IV - (Epithelial lining the cementum) The epithelial cells were identified by the presence of desmosomes and intracellular tonofilaments. The cemental surface of the extreme apical epithelial cells were closely adapted to the root surface; this space contained some granular material but no recognizable fibrils.

• (Ultrastructural changes within the cementum) 4 of 9 specimens had dissolution of the connective tissue fibers and their attachment to the cementum. These changes included a decreased electron density due to reduction in number and size of the mineral crystals, as well as loss of typical collagen structure in the affected zone. The remaining crystals at the surface of the calcified tissue were smaller than those found in deeper regions of the cementum. In some sections the mineral crystals were densely packed in a 0.1 to 0.5 micron wide layer at the surface of the hard tissue, while the subjacent layers were almost devoid of crystals. The process of cementum alteration did not reach the cemento-dentinal junction in any of the specimens studied. The specimens which showed alterations of the cementum below the level of the epithelial attachment also exhibited similar alterations of the hard tissue adjacent to the pocket epithelium.

Summary

The breakdown of the periodontal fibers was characterized by separation of the component fibrils followed by a longitudinal spitting of the collagen fibrils. This process was initiated some distance from the cementum surface. Concurrently with the alteration and reduction in number of the collagen fibrils, non-striated microfibrils appeared in increasing amounts. The most advanced stage of collagen degradation was seen immediately adjacent to the epithelial attachment, where the intercellular space contained bundles of non-striated filaments and granular debris but no typical collagen fibrils. Alterations were also found within the cementum in some of the specimens examined. These changes consisted of removal of mineral crystals. Whether the amorphous ground substance of the cementum matrix was also removed could not be definitively ascertained.

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