Tooth wear occurs during normal mastication. Pathologic wear, including abrasion and erosion, may also take place. Formation of reactionary and reparative dentin and obturation of dentinal tubules are biologic responses that compensate for the loss of tissue. Physical trauma to teeth will affect the blood supply to the pulp. Extensive physical trauma may result in the formation of mineralized, often bonelike tissue in the pulp chamber. Minor trauma, such as that associated with orthodontic tooth movement, may exert transient effects on the pulp or it may result in permanent structural changes. No experimental data involving restorative work on traumatized teeth have been published, but available evidence suggests that special care may be necessary in the restoration of such teeth because their reaction patterns may differ from those in nontraumatized teeth.