Pain in the face felt only on ascent is most likely due to pressure affecting the:

Pain in the face experienced only during ascent is most likely attributable to changes in atmospheric pressure affecting the sinuses. As an aircraft ascends, the decrease in external air pressure can cause the air trapped in the sinuses to expand. If the sinus openings are blocked or do not equalize pressure effectively, this can lead to a buildup of pressure within the sinus cavities, resulting in discomfort or pain.

While dental issues can sometimes cause facial pain, they are not typically associated solely with changes in altitude or pressure. Pressure changes would not specifically target the teeth unless there was an existing condition that makes the teeth sensitive to such changes. In contrast, pressure variations during ascent are more directly related to the sinuses and their ability to ventilate properly.

The ears are also affected by pressure changes, often resulting in "ear barotrauma" or discomfort due to the inability to equalize pressure in the middle ear, particularly during descent. However, the question specifies pain in the face, which aligns more with sinus pain than ear pain.

The nose experiences pressure changes as well, but interference or pain primarily manifests in the context of sinus involvement. Therefore, the conditions of the sinuses are more apt to explain facial pain in this scenario.