Histological assessment of periodontally involved cementum

Contamination of periodontally involved cementum by bacterial substances such as lipopolysaccharide (LPS) is considered a major reason for root planing. The purpose of the present study was to investigate the presence and location of lipid and polysaccharide within involved cementum as compared with uninvolved cementum. Frozen sections were prepared from the decalcified roots of 36 periodontally diseased and two control teeth. Serial sections were stained for either lipid (Oil-Red-O) or polysaccharide (Alcian Blue - PAS) and also with haematoxylin & eosin (H & E) or Huberstone's gram stain. Specimens of involved and uninvolved cementum were then examined under the light microscope for assessment of differences. Involved cementum from 12 of the periodontally diseased teeth exhibited strongly PAS-positive stained processes penetrating 3-7 mum into the surface of cementum from overlying plaque. Such processes were not observed in uninvolved cementum, suggesting a possible bacterial origin. Lipid granules were noted in only one involved specimen where they were situated up to 10 mum beneath the cemental surface. Similar granules were observed within plaque deposits but never in uninvolved cementum, again suggesting a possible bacterial origin. H & E and gram-stained specimens revealed the presence of microbial deposits in surface defects and within defects at the cemento-dentinal junction (CDJ), as well as penetration of micro-organisms into cementum in the absence of any surface defects. The results indicate that although lipid and polysaccharide of possible bacterial origin may be present within the 10 mum surface zone of involved cementum, the finding of microbial deposits down to the level of the CDJ suggests that all periodontally involved cementum should be removed during root planing, in order to achieve a root surface free of bacterial contamination.