4. Discussion
malocclusions, malocclusion, overjet
Our findings indicated that breastfeeding had an overall protective effect on increased overjet in adolescence, mainly mediated by pacifier use. While breastfeeding did not directly protect against increased overjet, it reduced pacifier use during childhood, lowering the overjet risk in adolescence by half, thus, confirming our hypothesis.Some specific mechanisms may explain our findings. Sucking requires control of many oral myo-functions, which occur concomitantly with increasing and decreasing pressures of a sucking cycle [During pacifier use, the posteriorly acting forces of the buccinator muscle act against the forward acting forces of suckling during breastfeeding and may restrain jaw growth [Pacifier use is also causally associated with weaning. Moreover, it is also a marker of interference with breastfeeding or even if the pacifier is being used as a strategy to start the weaning process [The benefits of breastfeeding and the negative impact of using a pacifier on different types of malocclusions are well established in primary dentition, with several systematic reviews [As far as the authors’ knowledge, this is the first study to investigate the effect of breastfeeding and the mediation role of a pacifier in permanent dentition. Focusing on specific malocclusion measures plausibly associated with sucking movements may be more revealing in studying breastfeeding and malocclusion [Some methodological aspects of our study merit attention and thus should be properly examined. Firstly, the analytical approach employed in the study allows the estimation of the total, direct, and indirect (via pacifier use) effects of breastfeeding on overjet. Although no statistical significance was found (the confidence interval includes the null value) for the direct effect, the direction of the estimated association suggests a protective effect of breastfeeding on overjet. When analyzing the total effect that comprises direct and indirect effects, there seems to be a direct protective effect of breastfeeding; however, it comprises the null value within 95% confidence interval limits. Therefore, it is not prudent to completely rule out a potentially beneficial direct effect of breastfeeding on overjet. More longitudinal studies with larger samples are needed to examine this matter, although we recognize that longitudinal studies with information on oral health across the life course are rare.Some potential study limitations merit discussion, such as the high attrition rate over the cohort time. However, the dropout rate is similar to other birth cohort studies [A central contribution of our study relates to the observed path linking breastfeeding to increased overjet through pacifier use. To properly interpret our findings, one has to bear in mind the counterfactual approach applied in the study, as well as the concepts of natural direct and indirect effects. The effect decomposition approach currently employed allowed us to identify that the breastfed children at 12 months used pacifiers less than those not breastfed at this age. Consequently, the reduction in pacifier use (influenced by breastfeeding) led to a lower overjet presence at age 12 years. Although the indirect effect accounted for approximately 65% of the total effect, a small, though not significant, direct effect of breastfeeding was noted, as previously discussed. Other methodological aspects of this study, such as its population-based longitudinal design, long follow-up period, and use of clinical data, reinforce the robustness and relevance of our findings. Finally, upon assuming the absence of unmeasured confounding (unlikely to occur as indicated by the E-value estimation) and measurement bias (mitigated by the study design and clinical examinations), our estimates may have a causal interpretation.From a clinician perspective, we emphasize the importance of oral health professionals, nurses, and paediatricians working together to support WHO breastfeeding guidelines during individual patient counseling. Previously, a randomized controlled trial demonstrated the effectiveness of home visits for advising mothers about breastfeeding and weaning on the reduction of pacifier use in the first year of life [