Thumb and lip sucking habits are complex neuromuscular patterns considered normal in childhood and abnormal from 3 years of age . The persistence of these habits can affect dentofacial growth , therefore prevalence research in transversal and longitudinal evaluation allows us to understand their impact on child growth and development.
Research in Nigeria , Cuba , Peru  and Italy  found that there was a direct relationship between deleterious habits and malocclusion, as in our study which found a relationship between the habit of atypical swallowing, thumb sucking, mouth breathing and retroposition with the presence of malocclusion. However, contrary to the Italian study, our study did find a relationship between deleterious habits and malocclusion types. Atypical swallowing and mouth breathing were related to vertical malocclusion, mixed breathing related to transverse malocclusion, and atypical swallowing, labial sucking, anteroposition related to sagittal malocclusion. In Spain, another author shows that deleterious habits can initiate, predispose and aggravate dental malocclusions, although they are not the main etiological factor governing their appearance .
Furthermore, according to Fialho and Col.  there is a relationship between non-nutritive sucking habits and anterior open bite, and concluded that the presence of deleterious habits was not determinant for facial morphology. That is why we recommend analyzing facial morphology and looking for an association with deleterious habits. In this study we understand that there are intrinsic factors that can be recognized by the dentist and there are also extrinsic factors (genetics) that can act in isolation or in combination leading to malocclusions.
This study shows the existence of a statistically significant relationship between anterior deep bite with the mixed breathing habit, anterior open bite with the atypical swallowing habit. Jamilian showed that children with the habit of thumb sucking have a greater risk of suffering anterior open bite and posterior crossbite , coinciding with the research carried out in Spain  and India .
It is important to mention that bottle-feeding during weaning is a risk factor, not evaluated in this study, which was strongly associated with anterior open bite, according to the longitudinal study conducted by Moimaz et al. , who monitored sucking habits and nocturnal oral breathing from pregnancy to 30 months of birth.
Our results corroborated the findings of Condori et al. , showing that there is a statistically significant association of transverse malocclusion, such as posterior crossbite, with mouth breathing habit; edge-to-edge bite (transverse) with atypical swallowing habits; mouth breathing and mixed and scissors bite with retroposition posture habit.
In addition, a study in adolescents in Northeastern Brazil showed that deleterious habits cause premaxilla conditions, protrusion of the upper incisors causing anterior open bite and posterior crossbite . The prevalence of posterior crossbite is caused by poor oral habit leading to low tongue positioning during sucking, lack of tongue thrust to the palate mainly causes increased activity of the cheek muscles. This, in turn, leads to altered muscle pressure in the upper arch, resulting in malocclusion. .
It should be noted that Condori et al.  added an anatomical factor to the research and found a direct relationship with maxillofacial alterations, according to the degree of adenoid obstruction caused by adenoid hypertrophy. Likewise, Rossi et al.  defined a direct relationship between the degree of nasal obstruction and its repercussion on the facial, skeletal and dental pattern. However, a strong evidence-based association has not yet been established .
The Class I malocclusion without anterior crossbite was associated with atypical swallowing, however atypical swallowing does not generate a Class I malocclusion but rather, this habit is present in open bites and in Class II malocclusions according to Jimenez , this association may be due to the fact that our sample has a Class I skeletal pattern and there has not been a transition of the swallowing pattern, they remain with childlike swallowing. The Class I malocclusion with anterior crossbite was related to thumb sucking habit, coinciding with a research paper carried out in Brazil . This may be due to a thumb sucking in a horizontal position of the fingers that stimulates a forward sliding of the jaw, just as Jimenez  we found that Class II Div 1 malocclusion was related to atypical swallowing and lip sucking habits (p < 0.05). It was found in the research in agreement with the aforementioned authors that there is no statistically significant association of Class II Div 2 malocclusion with deleterious habits, one possibility is that this malocclusion is influenced by genetics and not by habits.
Class III malocclusion without anterior crossbite was associated with anteroposition posture, the individuals in the sample presented a Class III dental malocclusion that could be due to loss of lower teeth that caused mesialisation of the lower first molars, however, they have a Class I or II skeletal pattern. Class III malocclusion with anterior crossbite had a statistically significant association with retroposition posture. This is explained because in children with Class III malocclusion the angle of cervical lordosis is lower than in children with Class I and Class II malocclusion .
Among the limitations that arose were not registering Graber’s trident with which the intensity, duration and frequency of each deleterious habit can be evaluated and according to that relate it to skeletal changes. In addition, it is recommended to use an index of need for orthodontic treatment for the diagnosis of malocclusions; and since it is a cross-sectional study, it is not possible to know if the habits appeared after having malocclusion. It is not possible to extrapolate the data to all pediatric patient, because the population was children who come to a School of Dentistry in need of care. It is recommended to evaluate vertical, transverse and sagittal malocclusions with vertebral defects and find their correlation. It is also recommended to evaluate age ranges to investigate in which the deleterious habit generates greater malocclusion and in which type of dentition.