Table 3.

Hill’s criteria of causation applied to malocclusion and its association with breastfeeding and bottle feeding.

Criteria	Definitions	Causal Relationship between Bottle Feeding/Breastfeeding and Malocclusion
Strength	How strong is the association between the cause and the effect?	It seems that prolonged breastfeeding can protect against malocclusion or favour normal occlusion The evidence related to the association between malocclusion and bottle feeding is weak; the studies reported divergent findings
Consistency	The association is consistent when results are replicated in studies in different settings using different methods	The studies were conducted among children from different countries and different methods were applied
Specificity	The cause leads to a single effect. The more specific an association between a factor and an effect is, the bigger the probability of a causal relationship	Despite the lack of evidence, the majority of studies linked bottle feeding to some type of malocclusion
Temporality	The cause precedes the effect	It seems that the cause (bottle feeding) occurs before the effect (malocclusion), but the studies did not conduct an initial dental examination in order to prove that the outcome of interest was not present at the start of study
Biological gradient	Also known as dose response. Greater exposure should generally lead to greater risk of the disease/ effect	Despite the lack of evidence, it seems that longer breastfeeding duration favours normal occlusion It seems prudent to interrupt bottle feeding as soon as possible until further evidence is obtained
Plausibility	The effect must have biologic plausibility	The habit of sucking an object such as a bottle which is related to feeding habits, involves patterns of muscle contraction in the orofacial region and may cause malocclusion
Coherence	Coherence between epidemiological and laboratory findings increases the likelihood of an effect	There were no studies indicating a credible level of coherence
Experimental evidence	Experimental or semi-experimental evidence exists to support the causation hypothesis	There were no studies demonstrating malocclusion in the animal model
Analogy	The effect of similar factors may be considered	There were no studies demonstrating malocclusion in the animal model