Infants and young children frequently engage in unconscious oral habits due to some prepotential reflexes, lack of feeding, and fear or unpleasantness.
A significant association of oral habits with malocclusion has been reported in various studies and the effect of oral habits on cranial maxillofacial growth and development is dependent on the nature, onset and duration of habits.
Digit sucking, a habit occurring in childhood, can be replaced by other activities as the child matures. It includes thumb and finger sucking and may alter dento-skeletal development, leading to malocclusion if persistent over a long period of time. Individuals with this oral habit often display bite marks and deformation of the fingers or thumb.
Thumb sucking displaces the tongue to a low position. The change in the balance between the outward thrust of the tongue on the palate and the inward activity of the muscles of the cheeks can affect the upper arch, which frequently results in protrusion of the upper incisors and the premaxilla, atypical swallowing, anterior open bite, and posterior crossbite.
The posterior teeth may extrude since the placement of the thumb between the upper and lower arch decreases occlusal contact. Downward and backward rotation of the mandible may occur. The malocclusion caused by finger sucking is different from that caused by thumb sucking.
Edge to edge bite or anterior crossbite can be observed in the child with finger sucking since this behavior will guide the mandible to a forward position.
Palatal cribs and arches, giving advice and incentives for changing behavior (known as psychological advice/treatment), and applying a bitter, nasty tasting substance to the children’s thumbs/fingers or combinations of these treatments can be tried to help children break this bad habit.
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Tongue thrust is a condition during swallowing where the tongue gets in touch with any teeth anterior to the molars. The correlation between this habit and malocclusion is probably reciprocal, meaning that tongue habit may cause malocclusion and malocclusion might contribute to the generation of the habit.
Dixit UB stated that children with tongue thrust incline to have lip incompetency, proclination of maxillary incisors, mouth-breathing habit, hyperactive mentalis muscle activity, open bite and lisping, compared with children without tongue thrust.
Tongue thrust may have an influence on oral sensory perception, which can leads to a change in motor activity, exacerbating the degree of malocclusion.
Surgical or orthodontic modification of the oral environment, mechanical restraints or reminders such as cribs, speech therapy, and oral myofunctional therapy can be used to motivate children to give up this habit in individualized manners.
Lip habit includes sucking or biting of the lips or cheeks, among which biting of the lower lip is most common. In patients presenting with lower lip sucking, strong contractions of the lower lip’s orbicularis muscle and the mentalis muscle are induced, leading to proclination of maxillary teeth and retroclination of the mandibular teeth, increased overjet, maxillary generalized spacing, mandibular incisor irregularity, and deepening of the labiomental sulcus.
Upper lip sucking, on the contrary, may cause restriction of the maxillary development and anterior cross bite. It is normal to see constriction of the upper and lower arch, and posterior open bite in patients with cheek sucking and biting. A lip bumper appliance can be used to break this bad habit.
Habitual mouth breathing
Habitual mouth breathing generally occurs with obstruction of the nasal airway caused by various diseases, such as adenoid and palatine tonsillar hypertrophy, rhinitis and nasosinusitis, and hypertrophy of nasal turbinate.
Alteration from nose to mouth breathing pattern affects the position of the tongue and mandible, and causes disruption in the balance of the oral and perioral muscles.54 Anatomic abnormality can appear in oral breathers (e.g., open bite, clockwise rotation of the mandible, increasement in the anterior lower facial height, a narrow maxilla, and a deeper palate).
Children with tonsillar hypertrophy may extend their mandibles forward with the purpose of relieving dyspnea. The tongue will bring the mandible to a forward position, which can also lead to mandibular prognathism and anterior cross bite.
Long-term mouth breathing can also cause gingival drying and result in accumulation of the dental plaque, with hyperplastic gingivitis as a frequent outcome.
Low academic achievement and poorer phonological working memory was even reported by Kuroishi RC in children with mouth breathing, compared to participants with nasal breathing.
Therefore healthcare professionals should take special note of children with mouth breathing and consider the use of vestibular shield.
Unilateral mastication habit
Unilateral mastication habit is a phenomenon where an individual chews exclusively on one side, which can be attributable to pain caused by serious dental caries or inconvenience in chewing due to retained root tips or severely decayed crowns on the unused side. Buccal crossbite is also one reason for this oral habit.
Increased lateral pterygoid muscle size has been described on the chewing side when compared the opposite side by Balcioglu HA, which may be related to the relatively high occurrence of temporomandibular disorder in children with unilateral mastication habit.
Hypertrophy on the chewing side and atrophy of the non-used side can lead to facial asymmetry, unilateral cross bite and deviation of the lower midline.
New appliances have also been introduced to address malocclusion in the deciduous and mixed dentition, including the myofunctional trainer and eruption guidance appliance.
Since these appliances are simple and economical, they are proposed for use in eliminating oral dysfunction, establishing muscular balance, restoring normal overjet and overbite, correcting or decreasing maxillary incisor protrusion and anterior crowding. But the cases must be carefully selected, and the operator should be well trained in their use.
°International Journal of Oral Sciencevolume 10, Article number: 7 (2018)
°Jing Zou / Mingmei Meng / Clarice S Law / Yale Rao / Xuedong Zhou