Caries increment over A 3-Year Period in Adolescent

Children in Riyadh, Saudi Arabia

 
A longitudinal epidemiological study was carried out to correlate caries increment with base-line DMFT, frequency of sugar consumption and oral hygiene in Riyadh children. A 3-day dietary diary was obtained from 12-13-year-old children prior to an initial dental examination and interview in 1989, while the final dental examination took place three years later. Information was also obtained on the children's oral hygiene practices. Caries increment was significantly higher in girls than boys (p < 0.01) and, on the average, approximately one tooth per child succumbed to caries each year. Although there was a statistically significant relationship between the base-line DMFT and caries increment, regression analysis showed that baseline DMFT could not be used to predict future caries experience. In addition, there was no association between frequency of sugar consumption and caries increment. Contrary to expectation, the children who practiced oral hygiene three or more times a day experienced significantly higher caries increment than those who did not practice any Form of oral hygiene. As caries increment was relatively low, an annual check-up fof caries would appear adequate for most of the children.
 

Sugar forms a considerable part of the traditional  diet in Saudi Arabia, an oil rich country, situated  between the Red Sea and the Arabian Gulf.  Concomitant with the rapid economic development  in the Kingdom within the past few decades has  been importation of substantial quantities of sugar  each year. A study of the dietary habits in Riyadh  school children showed that many of their meals  contained sugar while school snacks commonly  included soft drinks, cakes and chocolates.¹ It is  therefore to be expected that caries experience in the  Kingdom would be on the increase.

Previous studies of caries experience in the  Kingdom, such as those by Al-Shammery et al² and  Al-Khateeb et al³, were cross-sectional and provided  no information on caries increment. As far as is  known, there has been no reported longitudinal  study of caries experience in an Arab community.  In fact, such studies are relatively few anywhere in  the world.⁴

Previously, we described caries experience in  12-13-year-old school children¹ sampled from  Riyadh metropolis in 1989. We have followed up  these children for a period of three years with the  aim of determining their caries increment. In this  report, we describe the correlation between caries  increment and baseline DMFT, frequency of sugar  consumption and oral hygiene practices in these  children.

A detailed description of the sampling, dietary  data collection and clinical examination has been  reported elsewhere.¹

The children's dentitions were examined for dental  caries under natural lighting conditions. Caries  diagnosis was predominantly by the visual method,  carious lesions being recorded at the cavitation stage.  From the DMFT obtained for each of the subjects in  1989 and three years later in 1992, caries increment  over the 3-year period was calculated.

The initial dental examination in 1989 was done  by one examiner.¹   However, for social reasons, an additional examiner participated in the final  examination in 1992 so as to provide a male  examiner for boys and a female examiner for girls.  To calibrate the two examiners, they both examined  30 subjects prior to the final dental examination in  1992. In addition, the examiners each repeated  caries diagnosis in 35 subjects during the course of  the dental examination in 1992. The data were  analyzed using the statistical analysis system (SAS).

Essentially, all the 342 Saudi  children aged 12-13 years in 10 randomly selected  schools in Riyadh metropolis were included in the  sample. Informed consent for the work was obtained  from the school headmasters and headmistresses. A  3-day dietary diary was obtained from each of the  342 children, and from the data obtained, the children  were categorized according to their frequency of  sugar consumption as follows: low, if sugar  consumption was not more than once a day;  medium, if sugar consumption was 2-3 times a day;  and high, if sugar consumption was 4 or more times  a day. At an interview carried out on the fourth day,  uncertainties about the dietary diary were clarified  and information was obtained from the children on  their oral hygiene practices. The children were then  grouped into those who cleaned their teeth once,  twice or three or more times a day.

Inter-examiner reproducibility between the first and  the second examiners gave a kappa statistic of 0.91  while intra-examiner reproducibility, during the final  examination, gave values of 0.87 and 0.89, respectively.

Three hundred and nine out of the 342 children  who completed the 3-day dietary diary in 1989 were  available three years later for the final dental  examination (Table 1), giving an attrition rate of  9.6% over the 3-year period. Thus only the 309  children with complete dietary and clinical data  were included in the analysis. The mean base-line  DMFT for the 309 12-13-year-old children in 1989  was 1.95, 36.2% of them being caries-free (Table 2).  Although the mean base-line DMFT was higher in  girls than boys, the difference was not statistically  significant (p > 0.05).

Caries increment over the 3-year period varied  between 0 and 12 DMFT, the mean being 2.85  DMFT, indicating that on the average,  approximately one tooth per child succumbed to  caries each year (Table 3). Furthermore, caries  increment was significantly higher (p < 0.01) in girls  than in boys (Table 4).

Table 5 shows a cross tabulation between caries  increment and the base-line DMFT recorded in  1989. Chi square test showed that there was a  statistically significant relationship between the  base-line DMFT and the caries increment (p < 0.05).  However, regression analysis revealed that the  relationship was not linear, the p value for the slope  being 0.9328. A vast majority of the children  consumed sugar 2-3 times a day (Table 6) and  analysis of variance showed that there was no  statistically significant relationship between the  frequency of sugar consumption and caries  increment (p > 0.05). Furthermore, there was no  significant difference between the frequency of  sugar consumption in the boys and girls.

Contrary to expectation, caries increment was  lowest (1.70 ± 2.11) in those who did not practice  any form of oral hygiene and highest (3.44 ± 2.85)  in those who practiced oral hygiene three or more  times a day (Table 7). Analysis of variance showed  that this inverse relationship between caries  increment and frequency of oral hygiene was  statistically significant (p < 0.01). In contrast, the  relationship between the frequencies of sugar  consumption and oral hygiene (Table 8) was not  statistically significant (p > 0.05). About 53% of the  children used tooth brush/paste for their oral  hygiene, 15% used tooth brush/miswak and about  11% used miswak only (Table 9).
 

Children aged 12-13 years were selected for this  study because, at this caries active age, the effect of  sugar consumption and/or oral hygiene practices on  caries increment is most likely to be manifested  clinically. In addition, the 3-year study period is in  line with the recommendation by Rugg-Gunn et al,⁴  being considered adequate to allow caries increment  large enough for correlation with the various  independent variables. Furthermore, Saudi children  attend the intermediate school at ages 12-15 years,  before  proceeding   to  the  high   school.     Hence attrition rate of the cohort was not greatly affected  by movement from one level of educational  establishment to another (Table 1). The attrition rate  of 9.6% over the 3-year period is lower than the rate  of 12.9 over a period of one and one-half years  reported by Leverett et al⁵ in New York State, USA.

Caries diagnosis was mainly by the visual method  and this has been validated by several workers.⁶ For  logistic and ethical reasons, radiographs were not  used. It is unlikely that this had a significant effect  on the result of our statistical analysis. For example,  the inclusion of radiological variables did not  substantially increase the quality of prediction of  caries increment in a 4-year longitudinal study  carried out in Zurich, Switzerland.⁷

There is no perfect method available for  collecting data on sugar consumption,⁸ and the  reliability of the various methods remains a vexed  question. Nevertheless, the choice of method  depends on a number of factors: size of sample,  financial resources, availability of trained personnel,  educational level of the subjects, national  characteristics and special food habits.⁸ We utilized  a 3-day dietary diary supported by an interview  because, considering the sample size, among other  factors, this method was practical⁴ and economical.⁹  The dietary data collection was not repeated later in  the study (as originally planned) because we  perceived a change in the children's dietary habits  and/or reporting as they became aware of the nature  of the caries research.¹

The 3-year caries increment of 2.85 DMFT (0.95  per annum) is low when compared with the 2-year  increment of 2.2 DMFT (1.1 per annum) recorded  for 11-12- year-old English children⁴ and annual  value of approximately 1.5 for Icelandic children.¹⁰  It is, however, in agreement with an annual caries  increment of less than one DMFT in the  non-fluoridated (0.2 ppm) communities of Michigan,  USA.¹¹ As caries experience in Riyadh children is  moderate (mean base-line DMFT was 1.95) and, on  the average, caries increment is less than one DMFT  per year, an annual dental check-up for caries would  appear adequate for most of the children.

Slightly higher caries incidence in girls than boys  has been reported,¹²¹³ but the difference observed in  our study was surprisingly large (Table 4) and could  not be explained from our data. Inter-examiner  variability during the final dental examination  cannot explain satisfactorily this large difference

because inter-examiner reproducibility between the  male and female examiners gave a kappa statistic of  0.91. A possible explanation might be high tea  consumption in boys and not in girls, as has been  reported in Syria,¹⁴ a neighbouring Arab country.  Tea has a high fluoride concentration¹⁵ and may lead  to lower caries incidence in boys compared with  girls. It is also possible that adolescent girls  consume more sugar than similarly aged boys; this  needs to be clarified by future research.

The lack of association between the frequency of  sugar consumption and caries increment in 12-13  year-olds observed in this study was also reported by  Rugg-Gunn et al.⁴ who observed a stronger  correlation between caries increment and the amount  of sugar intake rather than frequency of sugar  consumption. Furthermore, such a poor correlation  has been attributed to the errors inherent in the  manner of dietary data collection in epidemiological  studies of this nature,¹⁶¹¹ In fact, decayed pit and fissures  contributed 78.9-93.4% of the carious lesions in the  Riyadh children. Hence it is likely that most of the  incremental carious lesions affected pits and fissures,  rather than smooth surfaces. This needs to be  confirmed by future studies, as the finding would be  useful for preventive programme planning.

Various workers have attempted to use past caries  experience as a predictor of caries increment.^17,18  Koch¹⁷ showed that if the subjects were categorized  into high and low caries groups according to their  DMFS smooth surfaces, past caries experience could  be used to predict caries increment in about  two-thirds of the subjects; but when all previously  carious surfaces were considered, past DMFS was of  predictive value in only 25% of the subjects. Thus,  even though there was a statistically significant  relationship between the base-line DMFT and caries  increment in the present study, base-line DMFT was  of little caries predictive value.

Precavitation lesions were excluded from our  caries diagnosis and the effect of this on the  predictive power of the base-line DMFT is  uncertain. While Seppa and Hausen¹⁹ concluded  that the inclusion of precavitation lesions added little  to the predictive power of conventional DFS scores,  Klock and Krasse²⁰ and van Palenstein Helderman et al.²¹ held a contrary view. Future studies should  therefore include precavitation lesions to throw  some light on this controversy.

The inverse relationship between the frequency of  oral hygiene and caries increment was unexpected.  The fact that caries increment was highest in those  who practiced oral hygiene most frequently  underscores the interplay between various factors in  caries aetiology. For example, the use of fluoridated  toothpastes by some of the children might  complicate the relationship between frequency of  oral hygiene and caries increment. Besides, the  frequency of oral hygiene may not necessarily  reflect the state of oral cleanliness. insufficient variability in the  pattern of sugar consumption amongst children in  modern society and the predominance of pit and  fissure caries in communities with relatively low  caries experience.
 

We are grateful to the Ministry and Board of  Education, Riyadh for giving us permission to visit  the Riyadh schools. We thank the headmasters and  headmistresses of the various schools for their  cooperation. This work was supported by King  Saud University, College of Dentistry Research  Center Grant No. 1040.