**1. Introduction**

Bone resorption of the maxilla related to tooth loss: The alveolar bone resorption that occurs after tooth extraction is a gradual, inevitable, and irreversible physiological phenomenon. According to studies, this resorption leads to a loss of bone height and thickness of up to 40% and 60%, respectively. The maximum resorption occurs within 3 months to 1 year after extraction, with two-thirds occurring in the first 3 months [1–3].

In the region of single-rooted teeth, resorption occurs mainly in a horizontal direction, while in the region of multi-rooted teeth, it predominantly occurs vertically

#### **Figure 1.**

*Single-rooted tooth (1): Bone resorption with a predominant horizontal direction (red arrow). In multi-rooted teeth (2), resorption mainly occurs in a vertical direction, both in the lower level of bone (black arrow) and in the upper level due to pneumatization of the maxillary sinuses resulting from the loss of root support (blue arrow).*

#### **Figure 2.**

*Clinical view, panoramic radiograph, and CT scan: Centripetal resorption of the upper alveolar crest, resulting in an anteroposterior displacement of the upper crest relative to the lower crest and an inverted maxillary relationship in the direction of an Angle class III.*

*Particulate Allografts (DFDBA) Combined with Platelet Concentrate: An Effective… DOI: http://dx.doi.org/10.5772/intechopen.112929*

(**Figure 1**) [1–3]. In the posterior part of the maxilla, this bone resorption is accompanied by a centrifugal pneumatization of the maxillary sinuses that increases with age [4]. The result of this phenomenon is a significant reduction in residual sub-sinus bone height, which may compromise implant placement in this area.

In a retrospective study of 248 edentulous patients, it was observed that less than half of the maxillae of patients over 65 years old have a bone height greater than or equal to 6 mm [4]. Post-extractional resorption can lead to a situation of bone volume loss that may compromise the implant treatment plan. Moreover, in some cases, it results in a modification of the relationships between the bone ridges due to centripetal resorption in the upper maxilla (**Figure 2**), which leads to an unfavorable situation in terms of biomechanics and esthetics.

It has been shown that post-extraction bone volume loss results from two phenomena: loss of the fasciculated bone [2, 3] and colonization of the upper third of the dental alveolus by connective tissue which has the effect of reducing the available space for bone healing [2–4]. There is currently a consensus on the need to perform post-extraction bone filling immediately after extractions to achieve the most optimal bone preservation [1–3, 5, 6], in order to minimize the bone loss that follows dental extractions and to ensure the best possible bone conditions for patient implant rehabilitation. When there is insufficient sub-sinus bone height, it is necessary to resort to a maxillary sinus graft prior to implant placement in this area [7, 8].
