**3. Recipient site classification and defect analysis**

The importance of alveolar bone defect analysis and classification is to determine the best regenerative treatment for each specific defect. This is more obvious when an evidence-based decision is made according to all data presented in the literature. Parameters which can describe alveolar bony defects are:


**Distraction osteogenesis and guided bone regeneration** are brilliant concepts which work basically by modifying normal bone healing process. Soft callous enlarging guidance is the key element in distraction osteogenesis and space maintaining for relatively slow growing hard tissue is the fundamental of guided bone regeneration techniques. This chapter introdu‐ ces methods of bone reconstruction and regeneration in oral and maxillofacial surgery. Indeed the knowledge of exact indications and advantages of each method is invaluable for the

The fundamental bony skeleton of the jaws consist of a mandible and two maxillary bones. Because of the functional aspect of these structures and their atrophic changes during aging, anatomical features have specific importance to distinguish defects and determine the proper treatment plan. The quantity and quality of bone in the alveolar process and adjacent structures are the key elements of this issue. The anatomical knowledge of these structures is also a

**The alveolar bone of mandible and maxilla** is a functional bony process which harbors teeth in a dentate human. After tooth loss, this bony structure loses its dimensions both vertically and horizontally [3]. After atrophic sequences, the maxillary alveolar arch diameter decreases, despite the fact that the mandibular alveolar arch enlarges in diameter and a pseudo-class III

The quality of edentulous alveolar bone is classified to D1, D2, D3 and D4 based on cortical

**D1** demonstrates the thickest cortical bone and the most dense trabecular part and is usually

determinant factor when using them as donor sites for reconstruction.

relation may appear in severe atrophic alveolar ridges (Figure 1).

**Figure 1.** A, The atrophic changes of mandible. B, The atrophic changes of maxilla.

bone thickness and density of trabecular bone respectively.

located in anterior mandible;

surgeon.

**2. Anatomy of the skeleton**

514 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2


Anterior and posterior parts of the mandible and maxilla have different bone qualities; hence they have different regenerative capacities [7]. The length of the defect affects the degree of vascularization. In vertical defects with no sufficient width to accept implants, the augmenta‐ tion procedure becomes complicated because both dimensions require restoration [8]. It has been suggested that a wide bony defect base has greater capacity for bone regeneration compared to a narrow base defect [7]. The number of surrounding bony walls around the defect is mentioned in the literature as stabilization for the initial blood clot [8].

Different classifications to describe alveolar ridge defects have been documented [9-11]. Seibert et al. classified the defects of the alveolar ridge based on dimension in which the resorption had occurred: horizontal defects (class I, 33%), vertical defects (class II, 3%) and the most common variant mixed horizontal and vertical defects (class III, 56%) [10].

Some similar classifications were suggested by other investigators according to the morphol‐ ogy of the alveolar bone defects. A classification published by Wang and Al-Shammari, the defects were subdivided in: horizontal, vertical, and combined [12]. Each group was further classified based on the amount of the deficiency.Studer (1996) documented the first quantita‐ tive classification of alveolar defects based on predicting need to reconstruct deficiencies, with classes defined as < 3 mm, 3–6 mm and > 6 mm [8].

**Figure 2.** A, Interdental partial edentulism. Class A: two-wall defect. The arrows show the defect walls. B, Free end partial edentulism. Class B: one-wall defect (arrow).

The Cologne classification of alveolar ridge defects uses orientation of the defect (horizontal, vertical, combined and sinus area) reconstruction needs associated with the defect (small: < 4 mm, medium: 4-8 mm large: > 8 mm) [8].Khojasteh et al. in 2013 in a literature review stressed the clinical importance of recipient site characteristics for vertical ridge augmentation con‐ cluded that information regarding the characteristics of the initial vertical defect is not comprehensively incorporated in most of the studies [8]. They proposed a classification with regard to the number of surrounding bony walls (A: Two-wall defects, B: One-wall defects, C: A defect with no surrounding walls) and width of defect base (I: A bony defect with a base width of 5 mm or more, II: A bony defect with a base width of 3 mm or more, but less than 5 mm, III: A bony defect with a base width less than 3 mm, (Figure 2).
