Purpose and problems of periodontal disease classification.

There has been a debate on the diagnosis and classification of periodontal diseases since dentists first became interested in periodontology. In this respect, periodontology is not unique; comparable discussions can be encountered in many fields of medicine, especially in complex diseases. Diagnosis is defined as the act of identifying a disease from its signs and symptoms, whereas classification is defined as the act or method of distribution into groups. The present article deals with the periodontal condition which is clinically characterized by three symptoms: loss of connective tissue attachment, loss of alveolar bone support, and inflamed pathological pockets. On the basis of these three symptoms one diagnostic name for this condition would be appropriate, e.g. destructive periodontal disease. However, if age, distribution of lesions, degree of gingival inflammation, putative rate of breakdown, response to therapy, etc., are also taken into account, numerous diagnostic names are needed. In order to be able to communicate about patients, clinicians have always felt the need for diagnostic names and classifications for these diseases, preferably on the basis of putative etiologic factors. At present, controversies about definitions of diseases continues, not only in the periodontal field but also in medicine. An interesting contribution to the discussion on disease terminology is a paper by Scadding (31) entitled: Essentialism and nominalism in medicine: logic of diagnosis in disease terminology . In this paper the clear distinction between these two types of definitions is highlighted. The essentialistic idea implies the real existence of a disease. Essentialist definitions typically start X is ... , implying a priori the existence of something that can be identified as X. Thus the doctor’s skills consist in identifying the causal disease and then prescribing the appropriate treatment. In relation to this, Scadding states: The essentialist s hankering after a unified concept of diseases as a class of agents causing illness, is mistaken and misleading for several good reasons: many diseases remain of unknown cause; known causes are of diverse types; causation may be complex, with interplay of several factors, intrinsic; and, more generally, an effect – the disease – should not be confused with its own cause’.