This could be impacted by habits such as finger sucking, nail biting, pacifier and tongue thrusting
Dental factors – size of the teeth in relation to the jaw, early loss of teeth could result in spacing or mesial migration causing crowding, abnormal eruption path or timings, extra teeth (supernumeraries), or too few teeth (hypodontia)There is not one single cause of malocclusion, and when planning orthodontic treatment it is often helpful to consider the above factors and the impact they have played on malocclusion. These can also be influenced by oral habits and pressure resulting in malocclusion. Behavioral and dental factors
In the active skeletal growth, mouthbreathing, finger sucking, thumb sucking, pacifier sucking, onychophagia (nail biting), dermatophagia, pen biting, pencil biting, abnormal posture, deglutition disorders and other habits greatly influence the development of the face and dental arches. Pacifier sucking habits are also correlated with otitis media. Dental caries, periapical inflammation and tooth loss in the deciduous teeth can alter the correct permanent teeth eruptions. Primary vs. secondary dentition
Malocclusion can occur in primary and secondary dentition. In primary dentition malocclusion is caused by:

Underdevelopment of the dentoalvelor tissue. Over development of bones around the mouth. Cleft lip and palate. Overcrowding of teeth. Abnormal development and growth of teeth.In secondary dentition malocclusion is caused by:

Periodontal disease. Overeruption of teeth. Premature and congenital loss of missing teeth. Signs and symptoms
Malocclusion is a common finding, although it is not usually serious enough to require treatment.
The overjet is reduced or reversed. Canine relationship by Ricketts
Class I:
Mesial slope of upper canine coincides with distal slope of lower canine
Class II:
Mesial slope of upper canine is ahead of distal slope of lower canine
Class III:
Mesial slope of upper canine is behind to distal slope of lower canine

Crowding of teeth
Crowding is defined by the amount of space that would be required for the teeth to be in correct alignment. It is obtained in two ways. 1) by measuring the amount of space required and reducing this from calculating the space available via the width of the teeth. Or 2) by measuring the degree of overlap of the teeth. The following criterion is used:0-4mm = Mild crowding
4-8mm = Moderate crowding
>8mm = Severe crowding

Causes
Genetic (inheritance) factors, extra teeth, lost teeth, impacted teeth, or abnormally shaped teeth have been cited as causes of crowding. Ill-fitting dental fillings, crowns, appliances, retainers, or braces as well as misalignment of jaw fractures after a severe injury are also known to cause crowding. Tumors of the mouth and jaw, thumb sucking, tongue thrusting, pacifier use beyond age three, and prolonged use of a bottle have also been identified.Lack of masticatory stress during development can cause tooth overcrowding. Children who chewed a hard resinous gum for two hours a day, showed increased facial growth. Experiments in animals have shown similar results.