Final answer:
Mouth breathing is the non-nutritive habit that can cause narrowing of the maxilla. This occurs due to improper tongue positioning affecting maxillary development, unlike bruxism or tongue thrusting.
Step-by-step explanation:
The non-nutritive habit that may result in the narrowing of the maxilla is C. Mouth breathing. Habitual mouth breathing can lead to alterations in the normal development of the facial bones, particularly the maxilla. This happens because the proper positioning of the tongue during nasal breathing stimulates
the transverse development of the maxilla. When an individual breathes through the mouth chronically, the tongue does not rest in the proper position against the palate, potentially resulting in a high, narrow palate, and a narrowed maxilla over time.
Bruxism is commonly associated with teeth grinding but does not directly cause narrowing of the maxilla. Tongue thrusting, while it can alter dental alignment, generally does not result in maxillary narrowing. The action of the masseter is b. chewing, which is the process of mastication, while mechanical digestion begins in the mouth with the action of the teeth and the grinding motion of the jaw.