A universal standard o f behaviour-oriented propensity for effective periodontal treatment has not been established. Perhaps it is quite difficult due to variation o f periodontal disease progression in different groups o f population. To define broad guidelines for appropriate behaviour propensity for effective periodontal treatment need based on the data o f the present Thai study population, the actual results o f association between periodontal conditions and behaviour-related risk factors was taken into consideration in combination with results from in the literature review. An acceptable target o f periodontal status was set as having 2 or less sextants with pockets. This level was modified from WHO’s suggestion for acceptable levels o f periodontal status in 35-44 years population, as ‘less than 7 teeth with pockets >4.5 m m ’ (WHO, 1982).
Table 8.1 presents results o f the analysis from the present study o f the relationship between major behavioural factors and periodontal pockets. The mean number o f sextants affected, percent of subjects affected and odds ratio o f any pockets, 3 or more sextants with pockets, and deep periodontal pockets were used as outcomes for comparison with the risk variables. Results show that plaque score (Greene and Vermillion, 1964), either at cut-off points o f 0.6
or 0.8, and current smoking were strongly associated with the presence o f periodontal pockets. While no significantly association was found for frequency of toothbrushing, past smoker, number o f cigarette per day and last dental visits. Number o f dental visits (more than 2 times) during the past two years had the adverse association with deep periodontal pockets.
Table 8.1 Associations between periodontal pockets and behaviour-related variables in 501 Thais
Independent variables
Periodontal pockets Periodontal pockets ^3 sextants Deep periodontal pockets
Mean sextants affected % Subjects affected Odds
Ratio Meansextants affected
% Subjects affected
Odds
Ratio sextantsMean affected % Subjects affected Odds Ratio Plaque score ^ 0.6 2.6 82.2 4.6*** 0.5 48.5 4 4*** 0.2 12.9 2.3** > 0 .6 4.3*** 95.5** 0.8*** 80.7*** 0.6*** 25.7** ^ 0.8 2.9 84.2 6.0*** 0.5 53.5 4.6*** 0.3 14.9 2.1** > 0 .8 4.5*** 97.0*** 0.8*** 84.2*** 0.6*** 27.1**
Tooth brushing ^ 1 times/day 4.0* 94.5 0.5 0.7 71.6 0.9 0.6 26.1 0.7
frequency ^ 2 times/day 3.6 89.5 0.7 68.6 0.4 18.8
Current smoker Yes 4.8*** 97.2* 4.0* 0.85*** 86.0*** 3.2*** 0.9*** 35.5** 2.6***
No 3.4 89.6 0.65 65.4 0.3 17.6
Past smoker Yes 3.8 93.9 1.9 0.7 69.7 1.2 0.3 18.2 1.0
No 3.4 89.2 0.7 65.0 0.3 17.5
Number o f ^ 10 4.9 98.0 0.2 0.9 87.8 0.7 0.6 28.6 1.4
cigarette/day ^ II 4.6 91.9 0.8 83.8 0.8 35.1
Last dental visit More than 2 yrs 3.8 90.8 1.3 0.7 71.0 0.8 0.4 21.6 0.9
Within last 2 yrs 3.6 92.6 0.7 65.6 0.6 20.5
Number o f O-I 3.6 91.8 1.3 0.7 65.9 0.9 0.4 15.3 2.4*
dental visit in ^ 2 3.5 93.5 0.6 63.0 0.9* 30.4*
past 2 yrs
' p< 0.5 * *p<0.01 ***p<0.001
Further analysis showed that the mean plaque score o f people who did not have any periodontal pockets was 0.51, with a 95% confidence interval o f 0.41 to 0.60. While the mean plaque scores o f people who have 1, 2, 3, 4, 5 and 6 sextants with periodontal pockets were 0.65 (Cl 0.53-0.77), 0.71 (0.60-0.82), 0.79 (0.68, 0.90), 0.80 (0.71, 0.90), 1.0 (0.92, 1.09), and 1.17 (1.09, 1.25) respectively. To define an appropriate cut-off point, the sensitivity and specificity o f cut-off points from 0.1 to 1.0 o f plaque scores in detecting the subjects who have 3 or more sextants with pockets were calculated (Table
8.2).
There was an increase of specificity, but a decrease in sensitivity when the cut o ff point was increased from 0.1 to 1.0 (Table 8.2). There was the same number o f subjects for the cut-off points of 0.2 and 0.3; 0.5 and 0.6; and 0.7 and 0.8. Thus, only the higher o f the two cut-off points was included in the selection.
Since no general rules exist for satisfactory sensitivity and specificity, a graphical approach of the Receiver Operating Characteristic (ROC) curve was applied to decide the ‘best’ cut-off point in relation to the optimum o f both sensitivity and specificity. This approach is to plot the sensitivity versus 1- specificity for each cut-off point. On the assumption that the ‘cost’ o f a false negative results is the same as that of a false positive result, the best cut-off point is that which maximizes the sum of the sensitivity and jspecificity, which is the point nearest the top left-hand comer (Altman, 1991). ROC curve showed that plaque level at 0.8 should be the best cut-off point for predicting subjects with 3 or more sextants of periodontal pockets (Figure 8.1). In other words, based on this study population, having a plaque score under 0.8 could
be recognized as a criteria for acceptable behavioural propensity for effective periodontal treatment. This group represents the lower 55th percentile o f the distribution o f plaque scores.
In the step-wise logistic regression analysis, three behavioural-oriented variables showing bivariate associations with periodontal pockets. They are plaque score (at cut-off point o f 0.8), current smoking and number o f dental visits in past 2 years. The three were tested by logistic regression for predicting periodontal pockets with 3 sextants or more. The results indicated that both plaque level at cut-off point o f 0.8 and current smoking emerged as predictors in the regression model, while number o f dental visits was not included. The model predicted 73.6% o f cases. Odds ratio o f smoking was 3.6 which is lower than the odds ratio o f plaque level (4.6). The logistic regression confirmed that, based on the results from this study, smoking has a direct effect on periodontal destruction, independently o f oral hygiene.
Based on the above estimations, which is similar to what found in reviewed studies, the suggested Effective Periodontal Treatment Need approach defines people who are non-smokers with a plaque index o f 0.80 or lower as having acceptable behavioural propensity for periodontal treatment. This criteria was used in integrating propensity to generate the data for an exploratory estimate o f Effective Periodontal Treatment Need in the study population.