Patterns of alveolar bone loss in the assessment of periodontal treatment priorities.

The main objective of this series of investigations was to develop a model to assess periodontal treatment priorities based on the amount of remaining alveolar bone support. To obtain proper data to generate this model, a cross-sectional and a longitudinal investigation of periodontal disease were undertaken. On radiographs from 531 subjects aged 25-75 years, assessments of alveolar bone level (ABL), i.e. the distance between the cementoenamel junction and the most coronal level of the alveolar bone support, were performed at the approximal surfaces of all present teeth A small proportion of the sample (11%) showed advanced alveolar bone loss (mean ABL greater than or equal to 6 mm). An ABL of greater than or equal to 6 mm was found in 13% of the tooth sites examined. The severity of alveolar bone loss was more pronounced in the maxilla than in the mandible. Incisors showed the highest and molars the lowest frequency of advanced alveolar bone loss. The assessments of ABL were repeated on radiographs taken 10 years later from 194 of the subjects. An average longitudinal tooth loss of 3.8 teeth/subject was noted. Differences in alveolar bone height were calculated. It was observed that 7% of the subjects and 10% of the tooth sites had experienced advanced additional loss of alveolar bone. The mean annual alveolar bone loss varied between 0.07-0.14 mm in ages between 25 and 65 years. 70 year old subjects showed the most pronounced rate of additional bone loss (0.28 mm/year). A subsequent clinical examination revealed an overall high degree of agreement between the radiographic and the probing attachment level determinations. In 92% of the tooth sites with measurable ABL and probing attachment loss the difference between the two assessments was within 2 mm. However, the agreement became poorer with increasing severity of periodontal tissue breakdown. The data on the longitudinal alveolar bone level changes generated age- and tooth type specific "critical" bone loss limits. These described amounts of bone loss beyond which therapeutic intervention must be performed in order to secure proper function of the teeth throughout life. A random sample of 192 industrial employees was examined radiographically and clinically. When traditional criteria were employed to assess the periodontal treatment needs, 100% of the subjects and 70% of the approximal tooth sites examined required therapy. Bleeding on probing together with the described alveolar bone loss limits identified the 40% of the subjects and the 2.5% of the tooth sites which should be given priority with respect to periodontal therapy.