Advances in Dental Research

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Root Caries in Scandinavia in the 1980's and Future Trends to be Expected in Dental Caries Experience in Adults O. Fejerskov, V. Baelum and E.S. Østergaard ADR 1993 7: 4 DOI: 10.1177/08959374930070010501 The online version of this article can be found at: http://adr.sagepub.com/content/7/1/4

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ROOT CARIES IN SCANDINAVIA IN THE 1 9 8 0 ' S AND FUTURE TRENDS TO BE EXPECTED IN DENTAL CARIES EXPERIENCE IN ADULTS O. FEJERSKOV V. BAELUM1

E.S. 0STERGAARD1 Departments of Oral Anatomy, Dental Pathology and Operative Dentistry, and ^eriodontology and Oral Gerontology Royal Dental College, Faculty of Health Sciences University of Aarhus Vennelyst Boulevard DK-8000 Aarhus C, Denmark Adv Dent Res 7(1):4-14, July, 1993

Abstract—The large variety of diagnostic criteria used adds some uncertainty to comparisons of recent clinical and epidemiological data on root caries in Scandinavia. Nevertheless, it is apparent that the prevalence of frank carious cavities on the root among 60+-year-olds is about 3040%. When inactive and recurrent lesions and fillings are included, the prevalence is almost 100% in 60+-year-olds. At this age, the mean number of root surface fillings is about 7, and the mean number of active caries lesions ranges from 0.9 to 3.4. The degree of gingival recession does not appear to be a direct measure of root caries risk in a population. When the number of teeth at risk is accounted for, the age-dependent increase in prevalence of root caries is very weak. Therefore, comparisons of root caries prevalence between populations are meaningful only when information on number of teeth present and teeth at risk is also available. Recent studies from various parts of the world have demonstrated that caries is ubiquitous in all populations and that caries progression continues throughout life. The impact of this on trends in prevalence and incidence of dental caries in adults is discussed in the light of what is known about the natural history of dental caries.

Based on a paper prepared for a symposium on "Changing Trends in Adult Dental Disease71

I

n the beginning of the 1980's, data on root caries were very sparse (for review, see Nyvad and Fejerskov, 1982; Fejerskov and Nyvad, 1986). During the last decade, however, an increasing number of studies has dealt with this disease entity, epidemiologically (Beck, 1990), microbiologically (Bowden, 1990; Nyvad, 1993), and from a histopathologic (Fejerskov and Nyvad, 1992, 1993) point of view. Several factors could explain this increased interest in rootsurface caries. First, there has been a substantial decline in caries among children in a large number of countries (Glass, 1982). Second, there is a growing appreciation that, in the future, more people will enter old age with a greater number of teeth retained. A large number of these retained teeth will be periodontally involved (Hugoson et al. 1992), and more root surfaces will be exposed, due to the gradual recession of the gingival margin in untreated patients (Baelum et al., 1986, 1988a,b). Likewise, periodontal surgery often results in exposure of root surfaces (Ravald and Hamp, 1981), and periodontal patients are very prone to development of new root-surface lesions (Ravald, 1992), despite extensive prophylaxis. A final reason for the increased interest in root caries is the claim that root caries is qualitatively different from coronal caries. In addition to the obvious topographical difference, the composition and structure of root surfaces are different from those of enamel. The mineral content of the root surface is lower and the crystal size is substantially smaller than that of enamel, resulting in root surfaces having a greater solubility than coronal surfaces (Hoppenbrouwers et al., 1987), and in vitro and in vivo studies indicate that caries lesions develop more rapidly on root surfaces (Phankosol et al, 1985; Ogaard et al, 1988; Nyvad et al, 1989). Some studies have suggested that the microbial flora associated with root caries is very different from that characteristic of enamel caries (Keyes and Jordan, 1964; Jordan and Hammond, 1972), but recent studies indicate that this does not seem to hold true (Ellen et al, 1985; Keltjens, 1988; Bowden, 1990; Nyvad and Kilian, 1990). While the compositional and structural differences between enamel and root surfaces will, of course, in and of themselves result in different clinical and histological manifestations of caries lesions (Fejerskov and Nyvad, 1986; Nyvad and Fejerskov, 1986; Schupbach etal, 1989), there is no a priori reason why different signs and symptoms should necessarily imply that the disease processes leading to the lesions are different. From a public health viewpoint, it is of major importance to know whether root caries is a disease entity basically different from coronal caries. Hence, if the caries process is essentially the same on coronal and root surfaces, it should be expected to respond to the same preventive measures in a similar way,


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ROOT CARIES IN SCANDINAVIA

regardless of its topography on the tooth. The purposes of this presentation are, first, to review recent clinical and epidemiological data on root caries in Scandinavia; second, to present a concept of dental caries initiation and development which provides a simple and concise explanation for a variety of phenomena that hitherto have required difficult and complex explanations; and, finally, to apply this concept to current clinical and epidemiological knowledge to discuss the expected future trends and their implications, with particular emphasis on root caries.

5

PREVALENCE AND SEVERITY OF ROOT CARIES IN SCANDINAVIA When data from different studies are compared and in particular when the evidence of changing trends in the occurrence of root caries is evaluated, difficulties arise because most available data are cross-sectional and have been collected in rather different ways, with use of a rather large variety of diagnostic criteria and definitions. Table 1 presents different criteria for recording root caries used in epidemiological studies in

TABLE 1 DIAGNOSTIC CRITERIA USED IN ASSESSMENT OF ROOT CARIES IN VARIOUS STUDIES IN SCANDINAVIA Kirkegaard e/a/. (1986) Lesions larger than 2-3 mm2 which are obviously soft when probed. Lesions along E/C junction recorded only if no more than 1/2-1 mm of enamel was involved. Relationship of lesions to restorations not recorded. Fillings recorded separately only if confined to root. Vehkalahti(1987) The unequivocally detectable lesion was obviously soft. More than half the lesion should be located on cementum. No fillings and no secondary caries lesions recorded. Salonen etal. (1989) A softened area or cavitation on the root which might involve adjacent enamel or restorations. An explorer could easily be inserted into the carious area with moderate finger pressure. Fure and Zickert (1990) Discrete, well-defined, and discolored area located either on the cemento-enamel junction or wholly on the root surface. Explorer enters easily and displays some resistance to withdrawal. Arrested caries: well-defined, discolored area which appeared hard and smooth. Restorations confined strictly to the root surface or extending into it were recorded as fillings. Secondary caries adjacent to fillings recorded. Fejerskov g/a/. (1991) Active lesion: Any root surface area that is well-defined and shows a yellowish or light-brown discoloration. The lesion is softened or of leathery consistency when probed with moderate pressure and may be covered by plaque. Inactive lesion: Any root-surface area that is well-defined, dark-brownish or black. The surface is smooth and shiny and appears hard when probed. In both active/inactive lesions, cavity formation may appear. Fillings recorded which are thought to be primarily a result of root treatment. Recurrent caries is recorded as active caries. 0stergaard(1987) Active lesion (as per Fejerskov et aL, 1991) Inactive lesion (as per Fejerskov et aL, 1991) Fillings with secondary caries classified as active/inactive. All fillings involving root surfaces are recorded. Gustavsen et al. (1988) A caries lesion being defined as an area softer than the surrounding tissue, with or without a cavity. The recording dentists were asked to use their clinical judgment. Caries encompassing both the coronal and root parts was registered as root caries. Fillings on the crown had to extend > 3 mm onto root surface to be scored as root filling. No information concerning recurrent caries. Downloaded from adr.sagepub.com by guest on July 14, 2011 For personal use only. No other uses without permission.

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TABLE 2 PREVALENCE OF ROOT CARIES LESIONS AND RESTORATIONS ON ROOT SURFACES, AND THE MEAN NUMBER OF TEETH WITH CARIES AND RESTORATIONS ACCORDING TO AGE AMONG 2112 DENTATE DANES [from Kirkegaard et al. (1986)] Mean No. of Teeth Mean No. of Teeth % with Root with Restorations with Root Caries % with Restorations Caries Lesions Age Groups (years) 16-19

0.5

-

0.0

-

20-29

1.0

-

0.0

-

30-39

7.7

0.6

0.2

0.0

40-49

15.1

2.9

0.4

0.0

50-64

26.5

10.3

0.7

0.1

65-81

41.9

11.3

1.0

0.2

Scandinavia during the 1980's. The assessments vary, from recording distinct carious cavities only, to a complete characterization of the status of the root surface, and it is thus clear that comparisons should be done with great prudence. A further complication inherent in comparisons of data originating in different populations is the impact of tooth loss. As an example, the Danish national oral health survey, carried out in 1981-82 (Kirkegaard et al, 1986), revealed that, in individuals after the age of 40 years, there was a rapid increase in tooth loss (Fig. 1), and that 59.4% of the population over the age of 65 was edentulous. Only 11.4% in this older age group had more than 20 teeth present. It is likely that persons who retain their teeth into old age represent a rather "healthy" subgroup of the entire population which, in turn, may distort our interpretation of epidemiological data. A further problem relating to the levels of tooth mortality is the selective loss of certain tooth types, i.e., molars are lost before premolars, etc. (Fig. 2). Unless all teeth can be considered equally at risk for root caries, such selective tooth loss may distort estimates of prevalence and severity. Despite these difficulties, some information may nevertheless be gleaned from the epidemiological studies of root caries carried out in Scandinavia during the last decade. TABLE 3 PREVALENCE OF ROOT CARIES ACCORDING TO AGE AND SEX AMONG 5028 ADULT DENTATE FINNS [according to Vehkalahti (1987)] Age Group Root Caries Prevalence (%) (years) Men Women 30-39

11

7

40-49

19

11

50-59

28

16

60-69

33

15

>70

32

27

The prevalence of root caries lesions among 20-29-year-old Danes was 1 %, increasing to 26% among 50-64-year-olds, and to 42% among 65-81 -year-olds (Table 2). The average number of teeth with root caries lesions or fillings ranged between 0.0 and 1.2 (Kirkegaard et al, 1986). Overall, the average number of teeth with root-surface lesions was 0.38. The prevalence of root caries in Finnish adults, as assessed in the national dental survey (Table 3), ranged from 7-11% among 30-39-year-olds and from 27-33% in the oldest age group, with men being more frequently affected than women (Vehkalahti, 1987). Overall, the mean number of teeth with root caries lesions was 0.32. % PERSONS 100

80-

60-

40-

20-

16-19

20-29

30-39

40-49

50-64

65-81

AGE IN YEARS EZH 20-32 TEETH

HI1-19 TEEETH

• B o TEETH

Fig. 1—Frequency distribution of all subjects in the respective age groups by number of teeth present. From Danish National Dental Survey (Kirkegaard et al., 1986).


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While the prevalence and severity of root caries thus seem to be quite similar in Finland and Denmark, data from Sweden have indicated a much higher prevalence and severity. Hence, an oral health survey conducted among 967 20-79+-year-old Swedes (Salonen et al., 1989) indicated a very high prevalence of root caries in all age groups (Table 4), ranging from 15 to 80% depending on age. In the youngest age group, root caries lesions comprised 8% of all carious surfaces, increasing to 51 % in the 40-49-year-olds and to 95% in the oldest age group. The mean number of root surfaces affected by caries lesions, as estimated from these data, ranged between 3 and 5 surfaces for individuals above the age of 50 years. These high estimates exceed those reported from a selected group of 60-80-year-old Danes (Fejerskov et al., 1991), in whom rather detailed examination criteria were used (Table 1). The prevalence of active root caries lesions among these older Danes was 60%, but when inactive lesions and fillings were included, there was a 100% prevalence. It should be appreciated, however, that this selected group had on average 20 teeth present (Fejerskov etal., 1991), as compared with 12-5.3 teeth in the comparable age group in the representative sample of the Swedish population (Salonen et al., 1989). Hence, the Danish group might represent a fraction of the population which is less at risk to caries than the Swedish sample. Moreover, the high estimates of both prevalence and severity obtained among Swedes in the study by Salonen et al. (1989) may, to some extent, be the result of the inclusion of caries lesions adjacent to restorations (recurrent caries) in the recordings. Finally, softened root areas were included and were defined as "initial root caries" if the examiner did not judge it necessary to make a restoration. From the data presentation, it is not possible, however, to judge the relative contributions of these types of lesions to the entire caries scores. Recently, the prevalence of root caries was assessed in a group of randomly selected 55-, 65-, and 75-year-old urban Swedes (Fure and Zickert, 1990). Root caries was recorded as seen in Table 1. When the slightly different age groupings are taken into account, the results corroborate those of Salonen et

al. (1989), in that the prevalence of root caries (including fillings) was high (Table 5), ranging from 85-93%, and the prevalence of frank caries lesions reached 65-68% among 65and 75-year-olds, respectively. However, persons in the older age groups in this study had substantially more teeth present (Table 5) than did similar persons in the study by Salonen etal. (1989). A further characteristic of the elderly Swedish persons studied by Fure and Zickert (1990) was a high treatment frequency (and accompanying recurrent caries) (Table 5). Although not statistically significant, men had a higher number of carious lesions than women, whereas women had more fillings. Root caries in elderly Danes was studied by 0stergaard (1987), who examined two groups of 60- and 70-year-olds in the Aarhus municipality. Of the total target sample, consisting of 600 60-year-olds and 500 70-year-olds, 61% and 55%, respectively, participated. Of the participants, 21% and 41% were edentulous. Root-surface caries was recorded as described by Fejerskov and Ny vad (1986) and by Fejerskov et al. (1991). The mean number of active lesions (0.9) found in these two cohorts of elderly Danes (Table 6) was similar to that found in the 65- and 75-year-old Swedes (Fure and Zickert, 1990) and was in accordance with the observations in the two older age groups in the Danish National Survey (Table 2). Although the mean number of active lesions was low, active lesions were REMAINING TEETH IN PERCENT

TABLE 4 PREVALENCE OF ROOT CARIES LESIONS AND THE MEAN NUMBER OF SURFACES AFFECTED AMONG 750 SWEDISH ADULTS [according to Salonen et al. (1989)] Age Group Prevalence of Mean Number (years) Root Caries of Surfaces 20-29

15.5

0.2

30-39

41.0

1.0

40-49

54.7

2.1

50-59

71.8

3.4

60-69

78.8

3.0

70-79

65.1

3.4

>79

80.0

4.8

1 00

Fig. 2—Teeth remaining in 60- and 70-year-old Danes according to tooth type.


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TABLE 5 MEAN NUMBER OF ROOT SURFACES WITH PRIMARY, SECONDARY, AND ARRESTED CARIOUS LESIONS BY AGE AND GENDER (SD in parentheses). PREVALENCE FOR ALL LESIONS AND CARIES ALONE [from Fure and Zickert (1990)] Prevalence Age Mean Number Arrested Secondary Primary (caries + N of Retained Group Caries Caries Caries Fillings fillings) (caries) Teeth m w m w m w m w w m 55

65

75

88

72

48

21.5

23.1

17.7

18.7

14.6

17.3

Total

0.6

0.2

1.3

0.7

0.7

0.2

6.9

7.3

(1.8)

(0.6)

(4.2)

1.4)

(2.1)

(0.5)

(7.0)

(6.4)

0.9

0.4

1.8

3.5

1.2

0

6.9

8.3

(2.0)

(1.1)

(3.5)

(5.3)

(6.2)

(0)

(7.4)

(7.3)

0.8

0.6

2.8

3.0

0.7

0.1

7.7

11.8

(2.5)

(1-1)

(5.5)

(5.9)

(1-7)

(0.4)

(8.6)

(10.8)

0.8

0.4

1.8

2.2

0.9

0.1

7.0

8.9

(2.0)

(0.9)

(4.1)

(4.5)

(4.1)

(0.4)

(7.8)

(8.3)

nevertheless found in about 12% of the dentate individuals (Table 6). When, however, recurrent caries was included, about 35-40% of the dentate older Danes were affected. Only when inactive caries lesions were also included did the prevalence figures (about 63-67%) reach the same order of magnitude as those of Salonen et al. (1989) in similar age groups. From the above, it is apparent that the dental health care systems in Sweden and Denmark result in a high number of fillings involving root surfaces. This pattern is also striking when compared with results obtained in Norway among 955 persons, aged 50-70+ years, who were examined by private practitioners (Gustavsen et al, 1988) (Table 7). The mean number of filled root surfaces was about 7.0, whereas the mean number of carious root surfaces (diagnostic criteria; see Table 1) was around 1.8 (Table 7).

ROOT-SURFACE CARIES IN RELATION TO AGE, GINGIVAL RECESSION, TOOTH LOSS, AND PAST CARIES EXPERIENCE It is apparent, from the above review of recent epidemiological studies of root caries in Scandinavia, that the prevalence and severity of root caries increase with increasing age (Kirkegaard

85

37

93

68

90

65

et al, 1986; Gustavsen et al, 1988; Salonen et al, 1989). It is possible, however, that this age-dependent increase is a reflection of more surfaces becoming exposed to or at risk of root-surface caries with increasing age, rather than being an effect of age itself. Certainly, in populations with limited access to dental health care, loss of periodontal attachment, which increases considerably with age, is frequently accompanied by recession of the gingival margin (Baelum et al, 1986, 1988a,b). Although claims have been made that Scandinavian populations do not suffer from gingival recession to any major extent, several studies have demonstrated that elderly Scandinavians do indeed experience gradual gingival recession. Hence, almost all (92-95%) elderly Danes have one or more surfaces at risk (Table 6), and about 20-60% of the surfaces may be affected (Figs. 3 and 4). Moreover, all types of surfaces are affected, and gingival recession seems to occur with a characteristic intra-oral distribution pattern (Figs. 3 and 4). Data from Norway (Table 7) and Sweden (Table 8) indicate similarly high, or even higher, proportions of surfaces with recession in the elderly age groups. Fig. 5 demonstrates the relationship between the number of teeth at risk of root caries, i.e., with gingival recession, and the occurrence of active root caries lesions in two different cohorts of elderly Danes. It is

TABLE 6 THE PERCENTAGE DISTRIBUTION OF 60- AND 70-YEAR-OLD DANES ACCORDING TO STATUS OF ROOT SURFACES (> 1 surface affected) [from 0stergaard (1987)] % with % with % with % with Age % with Inactive Active Recurrent Sound/ Mean Number of in Years Number Recession Lesions Lesions Lesions Filled Active Lesions 60

286

95.1

27.9

10.3

24.6

37.1

0.88 (SD 1.68)

70

163

92.6

27.2

13.2

26.5

22.1

0.89 (SD 1.48)


VOL. 7(1)


, SURFACES WITH RECESSION - 60-YEAR-OLDS

% SURFACES WITH RECESSION - 70-YEAR-OLDS

100

100 -BUCCAL

—I— LINGLJAL

~%~ APPROXIMAL

r

BUCCAL

—I—LINGUAL

-%~ APPROXIMAL

80-

MAXILLA

MAXILLA 60-

40-

40-

20-

20-

8

20-

7

^

6

5

4

3

1

2

^ "

^

X

40-

N,

^ *

60-

80-

MANDIBLE r\c\ -

80-

100

Figs. 3 and 4—The intra-oral distribution of gingival recession according to type of tooth surface in 60- and 70-year-old Danes. apparent from the Fig. that when the number of teeth at risk is accounted for, there seems to be no age-dependent increase in prevalence of active root caries lesions. However, the occurrence of recession is not in itself a measure of the risk of root-surface caries in a population. Hence, in adult Chinese with poor oral hygiene (Luan et al., 1989), virtually all surfaces in the older age groups of this population are at risk, i.e., exposed, but the occurrence of caries in these roots is quite low (Fig. 6). The Norwegian data provided by Gustavsen et al. (1988) (Table 7) demonstrate a much lower occurrence of gingival recession, with 45-65% of the surfaces being affected, but this recession is associated with a much higher occurrence of root caries. Hence, the Root Caries Index (RCI) values provided indicate that about 25% of the surfaces at risk had root-surface lesions (Gustavsen etai, 1988). From the data of Fure and Zickert (1990) (Table 8), it may be seen that about 56-71% of the surfaces had recession, i.e., were at risk. Even though these figures were higher than those reported in the Norwegian study (Gustavsen et al., 1988), the RCI values ranged between 13% and 22%, i.e., slightly lower than those reported in the Norwegian study. An analysis of the relationship between the number of teeth at risk of root caries and the mean number of teeth with root caries in the two Danish 60- and 70year-old age cohorts examined by 0stergaard (1987) (Fig. 7) reveals that the number of teeth with root caries lesions increases as a function of the number of teeth at risk only to a certain level

(10-17 teeth at risk), after which a further increase in the number of teeth at risk seems to be associated with a decline in the caries experience (Fig. 7). This observation is in accordance with the observations of Kitamura et al. (1986) and Beck (1990). The % PERSONS WITH ACTIVE ROOT CARIES 100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 192021 22232425 NUMBER OF TEETH AT RISK (RECESSION) "

60-YEAR-OLD

60-YEAR-OLD

*

70-YEAR-OLD

70-YEAR-OLD

Fig. 5—Prevalence of active root-surface caries lesions in relation to number of teeth at risk in 60- and 70-year-old Danes. Points connected by lines indicate values obtained by calculation of a moving average function of 5 observations, while unconnected points demonstrate the original observations.


10

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latter author found that individuals with less root caries reached age 65 with many teeth retained, as compared with those with fewer retained teeth. Those elderly who had nine or fewer teeth were experiencing new lesions (Beck, 1990). These findings indicate that simple comparisons of root caries prevalence between populations may be of limited value if no information is available on numbers of teeth present. ROOT CARIES 20-29 YR

4049 YR

30-39 YR

60-69 YR

50-59 YR

70+YR

BUCCAL

100 80 60"

87654321

8765432 1

1993

The above findings are not surprising, however. It is widely agreed that, up to the age of about 60 years, teeth are predominantly lost as a result of caries (Ainamo et al., 1984; Baelum and Fejerskov, 1986; Bouma et al,. 1987; Baelum et al., 1988a; Chauncey et al., 1989). Therefore, the more teeth retained, the more likely it is that the individual has had a low caries progression rate. Moreover, there is a positive association between the individual' s past caries experience (coronal caries) and the risk of developing root caries, as is apparent from the studies of Vehkalahti (1987) and 0stergaard (1987). In this context, it should also be remembered that Ravald et al. (1986) observed a positive correlation between baseline root-surface caries scores in 31 periodontally treated patients and their rootsurface caries scores 8 years later. Finally, Scheinin et al. (1992) have also recently demonstrated that past root caries experience yielded by far the highest odds ratio for new lesion development in a Finnish population.

87

THE RELATIVE ROLES OF ORAL HYGIENE AND FLUORIDES FOR TREATMENT AND PREVENTION OF ROOT CARIES

20 4060

In a series of papers, Ravald (1992) and collaborators have studied the effects of fluoride treatments and oral hygiene regimens on root-surface caries increments in periodontal patients. Hence, Emilson et al. (1992) studied the effects of a treatment regimen comprised of 6-10 episodes of extensive oral hygiene instruction, frequent polishing of the root surfaces with a fluoridated toothpaste, applications of Duraphat fluoride varnish, daily brushing with a fluoridated toothpaste, and consumption of lozenges containing 0.75 mg sodium fluoride and 200 mg Xylitol twice daily during a 12-month period, e.g., an extremely intense and "vigorous" treatment regime! The results demonstrated that, over a 12-month period, 54% of 46 active buccal root-surface lesions were converted into inactive lesions, whereas only 8-27% of active approximal lesions were considered inactive after 12 months. Ravald and Birkhed (1992), in a two-year clinical trial, exposed three groups of periodontally treated patients with root caries to extensive fluoride regimes, and, despite an "enormous exposure of fluoride" of the individuals, 246 new surfaces became involved (decayed or filled) in 99 patients. Moreover, 30% of these lesions were recorded as active lesions, although 40% of these active lesions occurred in relation to fillings.

80 100 INTERPROXIMAL

LINGUAL

10080 6040 20 ,87654321

87654321

87654321

87654321

8 7 6 5 4 3 2 1

87654321

20406080100•

EXPOSED; N O ROOT LESION

ROOT CARIES LESION

Fig. 6—The distribution of root-surface caries lesions according to age, tooth type, and surface in adult Chinese. Note a very low RCI. From Luan et al. (1989).

TABLE 7 ROOT CARIES AND FILLINGS IN RELATION TO SURFACES AT RISK IN 50-70+-YEAR-OLD NORWEGIANS [from Gustavsen et al. (1988)] % Surfaces Mean Number of Age in with RCI Surfaces with: Years N Recession % Caries Fillings 50-59

449

45.0

23.6

1.8

7.0

60-69

345

55.8

25.5

1.7

7.7

70+

161

65.6

24.7

1.8

6.2


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11


MEAN NUMBER OF TEETH WITH ACTIVE ROOT CARIES

TABLE 8 ROOT SURFACES AT RISK AND PERCENTAGES OF THESE WITH CARIES LESIONS (RCI) [from Fure and Zickert (1990)] % Surfaces Age in with Recession RCI %in Years Men Women Men Women

0,5 -

0 1

2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 19 20 2 1 2 2 2 3 2 4 2 5 NUMBER OF TEETH AT RISK (RECESSION) 60-YEAR-OLD

60-YEAR-OLD

70-YEAR-OLD

70-YEAR-OLD

Fig. 7—The mean number of teeth with active root-surface caries lesions in relation to number of teeth at risk in 60and 70-year-old Danes. Points connected by lines indicate values obtained by calculation of the moving average function of 5 observations, while unconnected points demonstrate the original observations. These results could indicate that fluoride is not as effective on root surfaces as one might expect based on studies demonstrating a negative association between root-surface caries experience and exposure to topically applied fluoride (Ripa et al., 1987; Jensen and Kohout, 1988) or fluoride given in water supplies (Brustman, 1986; Burt et al., 1986; Hunt et al., 1989; Stamm^a/., 1990). However, the somewhat limited success in Ravald and Birkhed's (1992) and Emilson et al.'s (1992) studies should be considered from the point of view that their prophylactic regimes focused on an overall improvement of oral hygiene based on a periodontal preventive regime (Ravald and Hamp, 1981) and did not aim at selectively removing microbial deposits from stagnation sites on the tooth surfaces other than along the gingival margin. Thus, from a comparison of their data from 1976 (Ravald and Hamp, 1981) with those obtained eight years later (Ravald, 1992), it is apparent that the new root caries lesions developed at exactly those sites where plaque removal was particularly difficult, i.e., along the cemento-enamel junction and along the margins ofexistingrestorations.Only 11 outof 157 new lesions that had developed during the eight-year period had developed along the gingival margin, where the patients had been particularly instructed in removing dental plaque (Ravald, 1992).

APPRECIATING THE NATURE OF DENTAL CARIES MAY HELP TO EXPLAIN CHANGING TRENDS IN PREVALENCE AND INCIDENCE AMONG ADULTS Dental caries as we define it, whether occurring on root or coronal surfaces, is "A dynamic process taking place within a microbial deposit covering a tooth surface at any given site in such a way that over time the outcome of this process is a disturbance of the equilibrium between the hard tissue (enamel, dentin, cementum) and the immediately surrounding fluid, such that a net loss of mineral occurs." According to this concept of dental caries, the presence of

55

63.6

56.4

12.6

14.9

65

68.5

71.2

16.1

16.1

75

57.8

69.1

21.1

21.8

microbial deposits on the tooth surface is the only necessary etiologic factor, whereas all other biological factors known to influence the disease outcome should be considered determinants rather than causes (Fejerskov and Manji, 1990). The definition implies, moreover, that caries should not be considered a disease mainly of childhood, as has been suggested (Dunning, 1979; Silverstone etai, 1981). Rather, one would expect adults to have caries incidence rates of a magnitude similar to that experienced by children. Recent studies have demonstrated that adults do indeed experience such caries increments (Glass et ah, 1987; Hand et al., 1988; Manji et al. 1989, 1991a; Luan et al., 1989). The variations observed between and within populations in caries prevalence and incidence can be ascribed to the effects of the many factors (determinants) which influence the disease (Beck et al., 1986; Fejerskov and Manji, 1990). It is widely agreed that the many determinants of dental caries—e.g., salivary flow rate, buffer capacity of saliva, number of salivary mutans streptococci, oral hygiene, etc.— have very complex interrelationships (Beck et al., 1986). Hence, this complexity could be one explanation why no single factor—whether alone or in combination with other factors— has so far appeared to be a useful predictor of the development of new root-surface caries lesions in adults (Ravald et al., 1986). While it could also be argued that this "failure" results from the fact that not all important determinants have been identified, the question is whether we should even expect to be able to predict, on an individual basis, the development or progression of a dental caries lesion by measuring these single determinants. Hence, even if the perfect deterministic model of dental caries initiation and progression could be developed and all important determinants identified, we would nevertheless be faced with the issue of lack of accuracy and precision inherent in all assessments (Manji et al., 1991b). The concept of dental caries presented above allows for prediction of outcomes (increase or decrease in dental caries) on a population basis if the values of an important determinant factor are changed over time or differ between two populations. As an example, it is today well-established that fluoride exerts its predominant cariostatic effect by influencing the physico-chemical dynamic processes occurring during lesion development—the "topical effect" (Larsen, 1975; Fejerskov et al., 1981; ten Cate and Duijsters, 1983; Featherstone and ten Cate, 1988). Therefore, it is expected that an increase in


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fluoride exposure of adults and elderly will—in and of itself—diminish the rate of caries lesion progression, resulting in fewer lesions with cavitation. This certainly is also the case, as evident from the observations of substantially fewer root caries lesions among adults living in fluoridated communities relative to low-fluoride communities (Burt et al, 1986; Stamm et al, 1990). Moreover, the incidence rate of both coronal and root caries in the elderly is lower in people who have been residents in areas with higher water fluoride concentrations relative to that seen in elderly who have lived for many years in low-fluoride areas (Hunt et al, 1989). However, the data from the longitudinal studies by Ravald and co-workers (Ravald, 1992) do convincingly demonstrate that unless dental plaque is selectively removed at sites at risk, root-surface caries may develop even under high fluoride exposure. Again, this emphasizes the very central role played by the microbial deposits on the root surfaces for caries development.

FUTURE TRENDS EXPECTED IN DENTAL CARIES EXPERIENCE IN ADULTS There is presently much speculation on the future need for dental health care as a result of the steady decline in caries experience among children during past decades. Claims such as "caries is on the increase again" and "caries will now appear much more severely in adults" are regularly perpetuated among the dental profession. This, in turn, influences political decisionmaking when funds are allocated to dental schools, dental research, dental public health programs, etc. Based on our current knowledge about the nature of dental caries, biologically and epidemiologically, it seems to us justified to suggest the following future trends in changes of oral health conditions and related need for traditional operative dental treatment among adults: Although today' s children have a very low caries experience, it is confusing or even misleading to talk about "caries-free generations". The percentage of so-called "caries-free" children has increased in each age cohort, but "caries-free" means free from obvious carious cavities in need of operative treatment— not necessarily free from disease. Consequently, the experience in Denmark, for example, where there has been a considerable caries decline among children over the past three decades (Fejerskov et al, 1982; Helm and Helm, 1990), should not be considered a signal that the disease is about to be eradicated. Rather, it demonstrates that the many determinants influencing the disease have changed, i.e., improved oral hygiene, topical fluorides, changes in types of snacks, etc., resulting in an overall very slow caries progression rate. A slow but ongoing caries progression means that as the cohorts grow older and become the adults, they will nevertheless experience a caries increment, even though they maintain stable life-style conditions. A 100% prevalence of dental caries may not be reached until very advanced ages, if at all. The crucial point is that dental caries is being postponed rather than eradicated. The consequence of this is that the age-specific manifestations of caries are expected to change. As an example, we are to some extent already seeing an increasing number of young adults who present approximal and, in particular, occlusal caries

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lesions that are very difficult to diagnose because of little obvious surface damage, but which subsequently appear to be penetrating deep into the dentin. Since the hitherto-extensive tooth loss in adult European populations has most likely been a result of dental caries (Bouma et al., 1987; Ahlquist et al., 1986) combined with factors such as accessibility, tradition for, attitudes to, and quality of dental health care, it must be foreseen that the delay in caries development will result in older people retaining an increasing number of teeth throughout life. This expectation, combined with the ongoing demographic change toward the elderly becoming an increasingly large fraction of the European populations, presents a situation in which many more elderly will have many more teeth present. Although improved oral hygiene among adults may, in the future, diminish the extent of attachment loss—and thereby gingival recession (Baelum et al, 1988a,b; Fejerskov et al, 1991)—with age, recent Scandinavian studies have demonstrated that the immediate impact of more elderly retaining more teeth is an increased prevalence and severity of periodontal breakdown (Hugoson et al, 1992). Therefore, the majority of teeth in most elderly people will exhibit exposed root surfaces, and consequently the total number of sites at risk for root-surface caries in adults and elderly will increase substantially. With this scenario before us, it is very important to appreciate that root caries, like coronal caries, can be arrested (Nyvad and Fejerskov, 1986), and that the initiation and progression of lesions can be controlled by proper oral hygiene combined with the application of topical fluorides. The prevalence of root caries lesions reaching cavitation in future older populations may therefore not necessarily increase above present-day levels. Despite the ubiquity of dental caries in all populations (Manji et al., 1991a), application of our knowledge about dental caries in the diagnosis, prevention, and treatment of caries may enable us to control root caries so that the majority of the lesions may be dealt with by non-operative treatment means. The present poor state of oral hygiene in the majority of the world's populations makes these populations susceptible to an increase in root-surface caries lesions if the determining factors, such as dietary habits, change in a negative direction. Some of the determining factors are highly influenced by the life situation of the individual, and the root caries situation among adults and elderly can therefore be expected to deteriorate quite rapidly if major negative life events occur (unemployment, retirement, death of relatives, loneliness, etc.). At present, root-surface caries does not really present a serious problem in Scandinavia (Vehkalahti, 1987; Kirkegaard et al, 1986; 0stergaard, 1987), the USA (Miller et al, 1987; Graves et al, 1992), and China (Luan et al, 1989). However, we should expect the need for oral health supervision to increase in the elderly so that root caries will not become a matter of major oral health concern in the future.

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