The healing process of post-extraction sockets is related to a series of biological events, including the formation of a coagulum replaced over time by:
- A provisional connective tissue matrix,
- Woven bone,
- Lamellar bone and bone marrow.1
The development of the alveolar process is directly related to the presence of the natural dentition, and it follows different degrees of atrophy after tooth extraction. Mainly, the limited supply of cells coming from the periodontal ligament causes resorption of bundle bone. Also, when the cortical bone plate is thinner, the alveolar bone is resorbed crestally and more on the buccal than lingual side.2 Clinically this physiological remodeling results in horizontal and vertical ridge resorption.
Ridge Preservation: An all-in-one approach
What are the solutions for retaining proper bone volume? When an alveolus with three bony walls is 100 % intact, and the fourth wall displays no more than 20 % bone loss, and not exceeding 1-1.5 mm vertical loss3, Ridge Preservation preserves the ridge volume within the bony envelope existing at the time of extraction.4
Clinical findings demonstrate that Ridge Preservation preserves the volume of the alveolar ridge predictably according to a biological compensation mechanism. The placement of a proper biomaterial in an extraction socket promotes bone modeling and compensates for marginal ridge contraction.5 The physiological resorption of bundle bone and the likely loss of the original buccal plate cannot be avoided. However, proper biomaterial bone regeneration occurring within the alveolus creates a new volume of crest comparable to pre-extraction volumes. Therefore, technically, Ridge Preservation does not conserve the alveolus but rather preserves the volume of the alveolar ridge.
Slowly resorbing biomaterials seem to be most effective in maintaining the initial three-dimensional volume of the ridge.6 With an intact socket, it is advisable to use a flapless approach to optimize results. Indeed, the elevation of a mucoperiosteal flap triggers a sequence of different biological phenomena and a transient hypoxia phase at the cortical level, which activates osteoclasts and subsequent bone resorption.7
Filling biomaterial: After extraction, the alveolus should be debrided and thoroughly rinsed with saline to decontaminate the site, before filling with a biomaterial. (Fig. 1) The ideal biomaterial must be biocompatible, osteoconductive and provide slow resorption to compensate for inevitable remodeling of the bundle bone. The deproteinized bovine bone mineral possesses these characteristics: It preserves on average 93 % of the initial crest volume at four-months follow-up, the alveolus volume is virtually preserved, and histologically it consists of approximately 26 % new bone and 18 % residual bovine bone granules.3
Protective biomaterial: Typically, after the placement of the filling biomaterial, the extraction socket is sealed using a resorbable collagen membrane or, more recently, a tridimensional collagen matrix (Geistlich Mucograft® Seal). (Fig. 1) The thick, double-layer, porcine-derived, collagen matrix efficaciously protects the underlying bone graft and promotes secondary healing of soft-tissues without the risk of infection. The smooth and dense outer layer of the collagen matrix limits bacterial penetration and encourages the migration of epithelial cells. Full closure of the soft-tissue usually occurs between the third and fourth week following extraction.
Implant: Four to six-months after Ridge Preservation an osseointegrated implant can easily be inserted into a preserved bone ridge, with appropriate crest volume and ideally healed soft-tissues.8(Fig. 1) A bone crest preservation technique is applied to maintain the pre-existing hard and soft-tissue anatomy, provide a stable crest volume and optimize functional and aesthetic results that simplify clinical procedures.