Darkfield microscopy of subgingival plaque of an urban black population with poor oral hygiene.

A low socio-economic community residing in Crossroads, Cape Town, consists of people who originated from the Eastern Cape areas of the Ciskei and Transkei. These individuals have had virtually no dental care, with the exception of emergency treatment for pain. A darkfield microscopic study of a random sample of 52 individuals was undertaken to determine the predominant morphological forms in the subgingival plaque of this population. Spirochetes were found to constitute 42.1% and motile rods, 7.7%, of the total darkfield microscopic count. Clinical assessment of the periodontal status of 100 individuals revealed the following mean values; plaque index (PI) = 1.44, gingival index (GI) = 1.31, probing depth (PD) = 2.35 mm and loss of attachment = 0.64 mm. Subgingival calculus deposits were present in 42% of the group and little or no mobility of the teeth was evident. Poor oral hygiene resulted in 90% of the tooth surfaces of the sampled population in Crossroads being covered with plaque, yet these individuals appear to be resistant to periodontitis. The high proportions of spirochetes and motile rods found in the subgingival plaque of this group were not indicative of periodontitis and therefore, fail to confirm the findings of other investigators.