Despite decades of well-established nonsurgical and surgical protocols and techniques, the treatment of deep intraosseous lesions still represents a challenge for clinicians. Therefore, the purpose of this textbook is to present simplified procedures that can be used to treat even the most difficult clinical scenarios. Both surgical and nonsurgical regenerative treatment options are presented and discussed in great detail, including types of instruments and regenerative materials to use, patient and defect evaluation, and step-by-stop protocols for various evidence-based procedures. Detailed clinical photographs and radiographs accompany each discussion to demonstrate the ideal initial situation for each method and the impressive results that can be achieved by following it, and many of the surgical sections also feature video content of procedures on real patients. A significant portion of the book is devoted to the single-flap approach, a technique developed and refined by the authors over many years to simplify surgical treatment while providing the best results for the patient. Both students and experienced professionals will find this atlas a welcome reference when encountering periodontally involved teeth.