Early interproximal carious lesions typically begin gingival to the contact area because this region has thinner enamel and is less self-cleansing than the actual contact point. Plaque accumulation is more likely in this gingival embrasure, where access for cleaning is limited and enamel rods are more susceptible to acid demineralization. The contact area itself is tightly adapted and less prone to initial decay. Recognizing this helps clinicians target early intervention and prevent lesion progression.

Reference: Fejerskov & Kidd, Dental Caries: The Disease and Its Clinical Management, 3rd Edition.