**2. Aging - tooth loss - bone loss**

Edentulous patients are in need of wearing some kind of prosthodontic replacement to establish lost oral function caused by tooth loss. It occurs because of biologic disease processes and age-related changes, such as dental caries, trauma, periodontal conditions and diseases, as well as poor oral hygiene and oral cancer [8, 9]. Total tooth loss is not only reflected in patients' inability to chew and speak but to their social behavior and self-image and it has a complex and multidimensional impact on oral health related and general quality of life [10, 11].

A large number of studies have already proven that bone loss represents an ongoing process following tooth loss [12, 13], affecting the mandible four times more than the maxilla [14]. This particularly affects the patients who become completely edentulous and creates a large problem for their future maintenance (**Figure 1**).

For the purpose of better understanding of the existing conditions, analysis of the edentulous jaws, easier diagnosis and therapy determination the American College of Prosthodontists (ACP) has developed a classification system for complete edentulism helping prosthodontists determine appropriate treatments for their edentulous patients [15]. This classification consists of four categories, the first representing an uncomplicated clinical situation with ideal or minimally compromised bone height, inter-jaw relationship, residual ridge morphology and muscle attachments and the fourth, representing the most complex and severely compromised oral conditions significantly negatively affecting the prosthodontic outcome [16].

#### **Figure 1.**

*Current condition of the edentulous maxilla and mandible caused by years of toothlessness. The height of the frontal mandibular bone has been measured to evaluate the possibility of implant placement.*
