Frontal resorption refers to the normal bone remodeling process occurring in the alveolar bone during orthodontic treatment and is not considered a side effect. In contrast, heavy orthodontic forces can cause undesirable outcomes such as root resorption, increased tooth mobility, and pain due to damage to the periodontal ligament and surrounding tissues. These effects result from excessive stress that exceeds the biological threshold, leading to pathological changes. Therefore, frontal resorption is a physiological response, not a side-effect of heavy force application.

Reference: Proffit, W.R. Contemporary Orthodontics, 6th Edition.