Application of zero‑inflated Poisson model with heterogeneous random effects to evaluate the effect of oral health education on pregnant women’s dental caries: A longitudinal experimental study

Abstract

Background: Pregnant women have poor knowledge of oral hygiene during pregnancy. One
problem with the follow‑up of dental caries in this group is zero accumulation in the decayed, missing,
and filled teeth (DMFT) index, for which some models must be used to achieve valid results. The
studied population may be heterogeneous in longitudinal studies, leading to biased estimates. We
aimed to assess the impact of oral health education on dental caries in pregnant women using a
suitable model in a longitudinal experimental study with heterogeneous random effects.
Materials and Methods: This longitudinal, experimental research was carried out on pregnant
women who visited medical centers in Tehran. The educational group (236 cases) received education
for three sessions. The control group (200 cases) received only standard training. The DMFT index
assessed oral and dental health at baseline, 6 months, and 24 months after delivery. The Chi‑square
test was used for comparing nominal variables and the Mann–Whitney U test for ordinal variables.
The zero‑inflated Poisson (ZIP) model was applied under heterogeneous and homogeneous random
effects using R 4.2.1, SPSS 26, and SAS 9.4. The level of significance was set at 0.05.
Results: Data from 436 women aged 15 years and older were analyzed. Zero accumulation in the
DMFT was mainly related to the filled teeth (51%). The heterogeneous ZIP model fitted better to
the data. On average, the intervention group exhibited a higher rate of change in filled teeth over
time than the control group (P = 0.021).
Conclusion: The proposed ZIP model is a suitable model for predicting filled teeth in pregnant women. An educational intervention during pregnancy can improve oral health in the long‑term follow‑up.
Key Words: Dental caries, longitudinal studies, pregnancy, zero inflation

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 Somayeh Ahmadi Gooraji: Pubmed,Google Scholar