Effects of population based preventive programs on oral health conditions

Introduction

World Health Organisation (WHO), in collaboration with the Fédération dentaire internationale (FDI) and the international dental associations, has established goals for the level of oral health to be attained by the year 2000 in selected indicator age groups of children and adults. Computer-based epidemiological systems are recommended for monitoring progress towards these goals. In a publicly funded health system, a computerized analytical and oral epidemiological system allows regular evaluation of the total effect of the national dental care and dental insurance systems on the oral health status and treatment needs of the population. At the same time, it offers an efficient mean of quality control at the regional level, allowing chief dental officers to continuously evaluate the efficiency of their preventive programs at surface, tooth and individual levels, as well as on their patients as a group.

In the classical study « Natural History of Periodontal Disease » by ^{Löe et al. (1978)}, it was shown that 40-year-old tea-workers in Sri Lanka, receiving no dental care, lost three times more probing attachment than a randomized sample of Norwegian academics receiving regular dental care. Despite differences in race and educational level, regular dental care seemed more likely to prevent loss of periodontal attachment than no dental care at all. However the quality of regular dental care may vary, and regular dental care is no guarantee for prevention or control of periodontal disease. This is exemplified in a controlled 6-year longitudinal study in adults (^{Axelsson and Lindhe, 1981}). The subjects in the control groups were offered conventional dental care once a year, irrespective of predicted risk and treatment needs. On the other hand, in the test groups the subjects were recalled by a dental hygienist, 4-6 times per year, for needs-related oral hygiene education, professional mechanical tooth cleaning (PMTC) and debridement. While the control groups continued to develop caries and loose more probing attachment, but at individual rates, in the test groups no further attachment loss was observed and very few new caries lesions developed.

On the basis of this study, a needs-related preventive program was designed for the adult population of the County of Värmland, Sweden. A comprehensive computer-aided analytic epidemiological program was designed to evaluate the effect of this program.

Material and methods

Material

During the first three months of 1988, four well-calibrated examiners conducted a baseline examination on a randomized sample of 1.091 35-, 50-, 65-and 75-year-olds : 50 % from rural areas and the remainder from urban areas of the County of Värmland. The number of 50-year-olds was increased to 426, because a longitudinal analytical epidemiological study was scheduled for this age group. Ten years later, early in 1998, new randomized samples of almost 600 35-, 50-, 65- and 75-year-olds were examined, and 314 of the 50-year-olds from 1988 were re-examined after 10 years, at the age of 60 years.

Epidemiological variables and methods

The new comprehensive computer-aided analytic epidemiological included many detailed clinical variables on function of the teeth, prevalence of oral diseases, treatment needs, etiological factors, external and internal modifying risk indicators and risk factors, etc. ^{Table I} shows in ranking order, the clinical variables included in the new oral epidemiological system, and etiological and modifying factors.

Initially, all randomly selected individuals received written information about the epidemiological study. This was followed by a telephone call to determine the number of edentulous individuals selected, to collect data about dental care habits, and to make an appointment for clinical examination. For people refusing to participate, the reason was noted. The examinations were conducted at Public Dental Health Clinics throughout the County of Värmland. Prior to the clinical examination the participant filled in a written questionnaire covering oral hygiene habits, dietary and smoking habits, general health status and medication, socio-economic background, knowledge about the etiology and prevention of oral diseases, etc. In addition, full mouth radiographs were taken and developed. The examining teams, four in all, comprised one dentist and one dental assistant. Each team used a portable personal computer for direct input of clinically diagnosed epidemiological data.

Results

Cross-sectional studies (1988 and 1998)

Edentulousness

The percentage of edentulous 50-, 65-and 75-year-olds decreased from 4, 17 and 30 % to 1, 7 and 16 % (^{fig. 1}).

Number of teeth

The number of teeth (3^rd molars excluded) increased from 26.4, 22.8, 16.9 and 14.5 to 27.0, 25.6, 20.7 and 17.6 teeth in 35-, 50-, 65- and 75-year-olds respectively (^{fig. 2}).

Periodontal attachment loss (PAL)

The mean loss of probing attachment loss measured mesiobuccally, mesiolingually, buccally, distobuccally and lingually decreased from 0.9, 1.8, 2.4 and 2.9 mm to 0.8, 1.5, 1.8 and 2.2 mm in the 35-, 50-, 65- and 75-year-olds respectively (^{fig. 3}). ^{Figure 4} shows the frequency distribution ( %) of individuals with mean mesiobuccal and mesiolingual PAL of 0-1, 1.1-2, 2.1-3, 3.1-4, 4.1-5 and > 5 mm in the four age groups in 1988 and 1998. The frequency distribution of mesial sites with 0, 1, 2-3, 4-6 and > 6 mm PAL in 35-, 50-, 65-and 75-year-olds 1988 and 1998 is shown in ^{figure 5} .

Community periodontal index of treatment needs (CPITN)

The percentage of sextants with highest CPITN score of 0, 1, 2, 3 and 4 or edentulous (M) sextants in the four age groups in 1988 and 1998 is presented in ^{figure 6} . ^{Figure 7} shows the frequency distribution of all sites (mesial, buccal, distal and lingual) according to CPITN scores 0, 1, 2, 3 and 4 as well as missing (M) sites in 1988 and 1998. The percentage of individuals with 0, 1, 2-3, 4-6, 7-12 and > 12 sites with CPITN score 4 (periodontal pocket depth > 5 mm) in the four age groups in 1988 and 1998 respectively is shown in ^{figure 8} .

10-year longitudinal study

Tooth loss

The mean number of teeth lost from age 50 in 1988 to age 60 in 1998 was < 0.7 per individual. ^{Figure 9} shows the frequency distribution ( %) of individuals who lost 0, 1, 2, 3, 4, 5, 6, 7 and > 7 teeth during the 10-year-period : > 65 % lost no teeth and > 20 % lost 1 tooth. As shown in ^{figure 10} , smokers (SM) lost 1.2 teeth (n = 62) and non-smokers (NSM) 0.5 (n = 125 ; p = 0.018). Tooth loss in subjects with high plaque values (HPI = > 40 % ; n = 75) was 1.0, and 0.4 in those with low plaque values (LPI = < 10 % ; n = 84 ; p = 0.03). Tooth loss was similar in males (M, n = 141) and females (F, n = 173) : 0.7/0.6 teeth (NS), and for those with low and high educational levels (LE, n = 136 ; HE, n = 178 : 0.8/0.6 teeth ; NS). Rural (RUR) and urban (URB) residents experienced similar loss of teeth : 0.6/0.7 (NS). With respect to dental attendance habits, tooth loss for regular (RDC, n = 306) and irregular attenders (IRDC, n = 7) was 0.6 and 2.7 respectively (NS).

Periodontal attachment loss

The mean PAL per individual per 10 years was 0.1 mm. The percentage of subjects with 0, 1, 2, 3, 4, 5, 6 and > 7 mesial sites exhibiting > 2 mm PAL was 24 %, 24 %, 17 %, 11 %, 9 %, 5 %, 3 % and 7 % respectively (^{fig. 11}). Only between smokers (SM) and non-smokers (NSM) were there significant differences in the mean number of mesial sites with > 2, 3 and 4 mm PAL (^{fig. 12}).

CPITN

At 50 as well as at 60 years of age, periodontal treatment needs, based on CPITN scores, were minor (^{fig. 13}) : in 1988, > 65 % of subjects had no pocket depths > 5 mm (CPITN = score 4) and this had further improved in 1998 (^{fig. 14}).

Discussion

Cross-sectional studies (1988 and 1998)

Edentulousness

One of the WHO global oral health goals for the year 2000 is that the percentage of edentulousness in 35-44 and 65-year-olds should be reduced by 50 % and 25 % respectively, from the levels in 1969. In the County of Värmland, edentulousness is non-existent in 35-44-year-olds and only 1 % in 50-year-olds, and declined in 65-year-olds by about 60 %, from 17 % to 7 %, in the 10 years from 1988 to 1998. Estimations based on these data indicate a further decline during the next 10 years, from 1998 to 2008, to about 0 %, 2 % and 8 % in 50-, 65- and 75-year-olds respectively.

Number of teeth

From 1998 to 1988, the mean number of remaining teeth in 35-, 50-, 65- and 75-year-olds increased by 0.8, 2.8, 3.8 and 3.1 respectively. For reference, the mean number of teeth in randomized national samples of 50-year-olds increased by only 1.7 teeth per individual from 1974 to 1985 (^{Håkansson, 1978} ; ^{Håkansson, 1991}). Excluding third molars, the fully dentate adult has 28 teeth.

Estimates based on the data from the two cross-sectional studies from 1988 and 1998, and the data from the 10-year longitudinal study indicate that during the next 10 years the mean number of remaining teeth in 65- and 75-year-olds will increase, to 25 and 20 respectively.

Periodontal attachment loss

From 1988 to 1998, the mean PAL for all tooth surfaces declined by about 25 % in the 65- and 75-year-olds. For the following 10-year period, estimates based on the data from our longitudinal study indicate continued improvement in average PAL, to < 1 mm, 1.6-1.7 mm and < 2 mm for 50-, 65- and 75-year-olds respectively. In order to exclude iatrogenic PAL, particularly on the buccal but also on lingual surfaces, the frequency distribution of PAL on the mesial surfaces is presented at individual (^{fig. 4}) as well as site (^{fig. 5}) levels.

CPITN

WHO recommends the use of CPITN at individual and sextant levels for estimating periodontal treatment needs in population surveys (^{Ainamo et al., 1982} ; ^{Cutress et al., 1987}). To date 200-300 surveys have been undertaken in more than 100 different countries. At both individual and sextant level, the most frequent findings from almost 100 CPITN surveys of 35-44-year-olds, in more than 50 countries, were calculus and shallow pocketing (score 2-3). With few exceptions, both the percentage of subjects and the mean number of sextants per subjects with score 4 were low (^{Miyazaki et al., 1991}). As shown in ^{figure 6}, score 4 was recorded in only 2-3 % of the sextants in our 35-year-olds. In this context, it is important to recognize that using the highest CPITN score at individual, sextant and even at tooth level, according to the hierarchical principle, grossly overestimates periodontal treatment need. We therefore evaluated and compared CPITN scores at sextants as well as surface levels. In analogy with DMFT (Decayed, missing, filled, teeth) and DMFS (Decayed, missing, filled, surface) indices in caries epidemiology, we stratified sextants, and sites as CPITN score 1, 2, 3, 4 or missing. Edentulous sextants and lost teeth will have had no periodontal treatment needs for several years. By using CPITN at site level and excluding missing sites, « true » periodontal treatment needs can be evaluated in individuals as well as in groups and populations. ^{Figure 6} shows the frequency distribution of CPITN scores 0-4 and missing, at sextant level. For comparison, ^{figure 7} shows the frequency distribution of sites, diagnosed according to CPITN score 0-4 and missing, representing « true » periodontal treatment needs. At sextant level, treatment needs are overestimated, even when edentulous sextants are excluded. An unexpected finding was that only 2-3 % of all sites in 75-year-olds have a CPITN score of 4 (^{fig. 7}), and almost 60 % had not a single site with CPITN score 4 (^{fig. 8}), reaffirming the high quality of our dental care system. In order to plan an efficient preventive strategy, it is also essential to have data on the pattern of disease in the dentition at surface level. As already stated, score 4 was almost negligible and score 3 was limited mainly to the mesial and distal surfaces of the maxillary molars, i.e. the « key-risk » surfaces. The approximal and lingual surfaces of the mandibular incisors had the highest percentages of score 2, indicating supragingival calculus requiring removal.

Risk indicators

The most important external modifying risk indicators for tooth loss and PAL was irregular dental care, smoking and low educational level (^{Axelsson et al., 1988} ; ^{Axelsson et al., 1998} ; ^{Paulander et al., 2000}). Further evaluations on risk indicators are under progress.

10-year longitudinal study

Tooth loss

From 1988 to 1998, the average tooth loss was < 0.7. For reference, in a national, randomized sample of the same age, tooth loss from 1974 to 1985 was 2.5-3 (^{Håkansson, 1991}). From 1972-1987, adults of the same age on a needs-related preventive program, visiting a dental hygienist 1-4 times a year, lost only 0.2 tooth per individual per 15 years (^{Axelsson et al., 1991}). The major external risk factors associated with tooth loss were smoking, high plaque scores and irregular dental care (^{fig. 10}).

Periodontal attachment loss

PAL was only 0.1 mm/ind./10 years. For comparison, data from the Natural History of Periodontal Disease showed that the mean annual PAL was 0.1 mm in Norwegian adult academics receiving regular dental care and 0.25 mm in Sri Lankan tea-workers receiving no dental care (^{Löe et al., 1978} ; ^{Löe et al., 1986}). The above 15-year longitudinal study by ^{Axelsson et al. (1991)} showed that irrespective of age, it is possible to control and prevent further PAL. Adopting 2 mm at site level as a « threshold » for true PAL, almost 25 % of the subjects did not exhibit a single such site and another 25 % only one site (^{fig. 11}). Further evaluation of risk factors for PAL is in progress. Preliminary data show that smoking is a significant risk factor (^{fig. 12}). This is an agreement with two other recent longitudinal studies (^{Norderyd et al., 1999} ; ^{Machtei et al., 1999}).

CPITN

Only about 2 % of the sites had a CPITN score of 4 already in 1988. However CPITN score 2 (= calculus or other plaque retentive factors to be removed) declined significantly from 1988 to 1998, i.e. improvement attributable to non-surgical periodontal treatment. As a consequence, the percentage of sites with 4-5 mm pockets (CPITN score 3) was reduced (^{fig. 13}). Between 65-70 % of the subjects had no single site with > 5 mm pockets (CPITN score 4), and only 2 % had 7-12 such sites (^{fig. 14}), indicating that the 60-year-olds in 1998 had been well-maintained for the past 10 years.

Conclusions and future perspectives

Analytic epidemiological data from 1988 and 1998, in randomized samples of 35-, 50-, 65- and 75-year-olds in the County of Värmland, Sweden, have shown that during a 10-year period, well-organized dental care and preventive programs can significantly improve oral health, particularly periodontal status, in the whole population, i.e. irrespective of age. The earlier 15-year longitudinal study by ^{Axelsson et al. (1991)}, also conducted in the County of Värmland, showed that further improvement in oral health can be achieved by more systematic grouping according to risk, and needs-related programs involving as much of the adult population as possible. Thus, in 1998 an updated needs-related preventive program was introduced for adults in the County of Värmland.

Most adult patients in the Public Dental Service (about 50 % of the adults) have also been grouped, on a scale of 0 to 3, for general risk (compliance, general health, etc.), periodontal risk, caries risk and iatrogenic risk. ^{Figure 15} shows the frequency of periodontal risk scores 0-3. In the year 2000, a baseline examination of the oral health status of all adult patients at the clinics will be conducted, to be followed by annual examinations. The computer-aided analytic epidemiological system to be used will be a very powerful tool for quality control, and indirectly for further promotion of oral health status. This has been our experience of the computer-aided epidemiological system introduced in 1979, for annual evaluation of needs-related preventive programs in children and young adults, involving almost 100 % of 3-19-year-olds. The goals for the subjects following this program from birth to the age of 19 years are :

- no approximal fillings ;

- no occlusal amalgam fillings ;

- no approximal loss of periodontal attachment ;

- to motivate and encourage individuals to assume responsibility for their own oral health (^{Axelsson et al., 1993}).

It is hoped that by 2000 these goals will be attained for 20-year-olds. As an example of improvements achieved to date, the mean DFS (Decayed, filled, surfaces) in 19-year-olds has decreased from 23 in 1979 to about 2 in 1998, with < 1 filling involving approximal surfaces.

Demande de tirés à part :

Per AXELSSON, Department of Preventive Dentistry, Public Dental Health Service, Älvgatan 47, S-652 30 KARLSTAD SUÈDE. E-mail : per.axelsson@karlstad.mail.telia.com

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