Which of the following factors does not influence the need for orthodontic treatment?

The need for orthodontic treatment is influenced by a variety of factors related to the structure of the mouth and teeth, as well as external conditions. Genetics plays a significant role, as hereditary traits can dictate the alignment and spacing of teeth. Environmental factors, such as thumb sucking or prolonged use of a pacifier, also impact dental alignment as they can alter the positioning of teeth during crucial growth periods.

Developmental issues, including variations in jaw size or tooth development abnormalities, are critical considerations because they can create misalignments that require orthodontic intervention.

In contrast, personal hygiene practices, while very important for overall dental health, do not directly influence the structural alignment of teeth. Good hygiene can prevent dental issues but does not alter the underlying anatomical factors that create a need for orthodontic treatment. Therefore, personal hygiene practices are the correct choice as they do not influence the need for orthodontic treatment in the same direct manner as the other factors.