A Re-analysis of Caries Rates in a Preventive Trial using Poisson Regression Models

Abstract

The analysis of caries incidence in clinical trials has several challenging features: (1) The distribution of the number of caries onsets per patient is skewed, with the majority of patients having few or no cavities; (2) the number of surfaces at risk varies (i) over time and (ii) between patients, due to eruption and exfoliation patterns, dental diseases, and treatments ; (3) surfaces within a patient differ in their caries susceptibility, and (4) caries onsets within a patient are correlated due to shared host factors. Recent statistical developments in the area of correlated data analyses permit incorporation of some of these characteristics into the analyses. With Poisson regression models, the expected number of caries onsets can be related to the number of surfaces at risk, the time they have been at risk, and surface- and subject-specific explanatory variables. The parameter estimated in these models is an epidemiological measure of disease occurrence: the disease incidence rate (caries rate) or the rate of change from healthy (sound) to diseased (carious). Differences and ratios of these rates provide standard epidemiological measures of excess risk. To illustrate, Poisson regression models were used for exploratory analyses of the Ylivieska xylitol study.

Keywords

Dental Caries Models Statistical,Xylitol

Get full access to this article

View all access options for this article.

References

Breslow NE (1984). Extra-Poisson variability in log-linear modeling . Appl Statist 33:38-44.

Breslow NE , Day NE (1980). Measures of disease. In: Statistical methods in cancer research. Vol. 1. The analysis of case-control studies. Lyon: IARC Scientific Publications, 66.

Campbell MJ , Machin D. , D'Arcangues C. (1991). Coping with extra-Poisson variability in the analysis of factors influencing vaginal ring expulsions. Stat Med 10:241-254.

Carlos JP , Gittlesohn AM (1965). Longitudinal study of the natural history of caries. II. A life-table study of caries incidence in the permanent teeth. Arch Oral Biol 10:739-751.

Carlos JP , Senning RS (1968). Error and bias in dental clinical trials. J Dent Res 67:142-148.

Case RAM , Lea AJ (1955). Mustard gas poisoning, chronic bronchitis, and lung cancer. An investigation into the possibility that poisoning by mustard gas in the 1914-18 war might be a factor in the production of neoplasia. Br J Prev Soc Med 9:62-72.

Cornfield J. , Mitchell S. (1969). Selected risk factors in coronary heart disease. Possible intervention effects. Arch Environ Hlth 19:382-394.

Espeland MA , Murphy WC , Leverett DH (1988). Assessing diagnostic reliability and estimating incidence rates associated with a strictly progressive disease: Dental caries . Stat in Med 7:403-416.

Glass RL , Alman JE , Fleisch S. , D'Agostino RB (1972). The appropriateness of analysis of variance to the statistical analyses of dental clinical trials. Arch Oral Biol 17:633-643.

10.

Grainger RM , Reid DBW (1954). Distribution of dental caries in children. J Dent Res 33:613-623.

11.

Isokangas P. , Alanen P. , TieksoJ, Makinen KK (1988). Xylitol chewing gum in caries prevention: a field study in children. J ADA 117:315-320.

12.

Isokangas P. , Alanen P. , TieksoJ, Makinen KK (1989). Long-term effect of xylitol chewing gum on dental caries. Community Dent Oral Epidemiol 17:200-203.

13.

Kelsey JL , Thompson WD , Evans AS (1986). Biological and statistical concepts. In: Methods in observational epidemiology. Monographs in epidemiology and biostatistics. Vol 10. Oxford University Press, 23-45.

14.

Kleinbaum DG , Kupper LL , Morgenstern H. (1982). Epidemiologic research. Principles and quantitative methods. New York: Van Nostrand Reinhold Company.

15.

Liang KY , Zeger SL (1986). Longitudinal data analysis using generalized linear models. Biometrika 73:13-22.

16.

Marriott FHC , editor (1990). A dictionary of statistical terms. Essex: Longman Scientific and Technical.

17.

McCullagh P. , Nelder JA (1989). Generalized linear models. 2nd ed. London: Chapman and Hall .

18.

Reed GF , McHugh R. (1979). The estimation of dental caries incidence in the presence of diagnostic error. Biometrics 35:473-478.

19.

Sherwin R. , Kaelber CT , Kezdi P. , Kjelsberg MO , Thomas HE (1981). The multiple risk intervention trial (MRFIT). II. The development of the protocol. Prev Med 10:402-425.

20.

US Department of Health and Human Services ( 1990). New findings/ new directions. In: Broadening the scope. National Institute of Dental Research, 134.