Yes,breathing through the mouth can produce throat dryness and soreness & Sinus drainage (post nasal drip) may cause a sore throat
A sore throat (or throat pain) is pain or irritation of the throat. A common physical symptom, it is usually caused by acute pharyngitis (inflammation of the throat), although it can also appear as a result of trauma, diphtheria, or other conditions. A sore throat may cause mild to extreme pain.
A sore throat is pain anywhere in the oropharynx. Medicine
Post-nasal drip (PND, also termed upper airway cough syndrome, UACS, or post nasal drip syndrome, PNDS), occurs when excessive mucus is produced by the nasal mucosa. The excess mucus accumulates in the throat or back of the nose. It is caused by rhinitis, sinusitis, gastroesophageal reflux disease (GERD), or by a disorder of swallowing (such as an esophageal motility disorder). It is frequently caused by an allergy, which may be seasonal or persistent throughout the year.]medical citation needed[
However, other researchers argue that mucus dripping down the back of the throat from the nasal cavity is a normal physiologic process that occurs in healthy individuals. Post nasal drip syndrome as a concept has been challenged due to a lack of an accepted definition, a lack of any pathologic tissue changes and no available biochemical tests. The term has been described as a "pseudo-syndrome" (i.e. not a real medical condition) which serves as a catch-all, waste basket term that is unhelpful. Health
Nasal congestion is the blockage of the nasal passages usually due to membranes lining the nose becoming swollen from inflamed blood vessels. It is also known as nasal blockage, nasal obstruction, blocked nose, stuffy nose, or plugged nose.
Nasal congestion has many causes and can range from a mild annoyance to a life-threatening condition. The newborn infant prefers to breathe through the nose (historically referred to as "obligate nasal breathers"). Nasal congestion in an infant in the first few months of life can interfere with breastfeeding and cause life-threatening respiratory distress. Nasal congestion in older children and adolescents is often just an annoyance but can cause other difficulties.
Throat irritation can refer to a dry cough, a scratchy feeling at the back of the throat, or a sensation of a lumpy feeling or something stuck at the back of the throat.