This book is dedicated to the phenomenon of invasive cervical resorption (ICR), a complex, detrimental disease that has been the subject of long-standing debate in the endodontic literature. Nowadays, reports of post-bleaching root resorption are uncommon. Tooth whitening has recently become a "hot" topic for both dentists and patients. The walking bleach technique is considered a safe method. And yet, the possibility of ICR occurring as a negative sequela of internal bleaching still exists. The four chapters of this book explore the various facets of this topic. Chapter 1 summarizes the current status of knowledge regarding the ICR in a synthetic manner. Chapter 2 presents three illustrative clinical cases of ICR in the upper anterior teeth, two of which are due to internal iontophoretic whitening with hydrogen peroxide. Chapter 3 discusses the issues related to ICR treatment and its long-term prognosis. Chapter 4 seeks to uncover the deep reasons for ICR and the opportunities for its effective prevention, including the causes of tooth staining and conditions for safe internal tooth whitening. Additionally, other unpublished cases from my practice are included in this book.