Nicholas Caplanis, Jaime L. Lozada and Juan Mesquida

Chapter Outline

Alveolar Bone Healing after Tooth Extraction

The healing of an extraction socket after tooth removal has been well studied in both animals and humans.⁶ Studies in animals demonstrate that during the process of healing, a series of events occurs. It begins with the formation and maturation of a blood clot and proceeds to infiltration of fibroblasts to replace the coagulum and eventual establishment of a provisional matrix that allows for bone formation. In an experimental animal study, Araujo and Lindhe² noted that resorption of the buccal and lingual plates occurred after tooth removal. This resorption occurred in two phases. In phase I the bundle bone was resorbed and replaced with woven bone, leading to a substantial vertical reduction of the crest. In the second phase, resorption occurred from the outer surfaces of both bone walls. This ultimately led to a loss of ridge width. In a follow-up study by the same authors,⁷ the effect of flap elevation on alveolar ridge dimension was examined. The authors concluded that flap elevation had very little or no effect on the alveolar process. These studies suggest that alveolar ridge resorption is a physiologic outcome directly caused by tooth removal.

In a study by Schenk and Hunziger,⁸ the alterations seen after tooth extraction were attributed to a decreased blood supply to the alveolus, which led to osteocyte cell death and necrosis of the surrounding tissue. In a further phase of healing, the necrotic bone may be gradually eliminated through surface resorption by osteoclasts in the periosteum. Additional factors related to these alveolar bone changes may be an adaptation to continued lack of function at the extraction site and tissue adjustment to meet genetically determined demands on ridge geometry in the absence of teeth. In a human study by Schropp et al.,⁹ bone and soft tissue dimensions were examined after tooth extraction. The authors found that the width of the alveolar ridge was reduced by 50% during the 1-year observation period. Most of these changes (approximately two thirds), occurred within the first 3 months after tooth extraction.

These studies suggest a need for procedures that can minimize alveolar bone and soft tissue changes after tooth extraction when esthetics, function, and long-term maintenance require minimal changes. This is especially evident in the esthetic zone.

Scientific Validation for Site Preservation

In a 6-month randomized, controlled, blinded clinical and histologic study in humans, Iasella et al.¹⁰ examined 24 patients who underwent extraction and then implant placement.¹⁰ The aim of the study was to determine whether ridge preservation procedures would prevent postextraction resorption. Tetracycline-hydrated, freeze-dried bone allograft (FDBA) was placed in extraction sockets, and the grafts were covered with a collagen membrane. The authors concluded that ridge preservation improved ridge height and width dimensions compared with extraction alone. The mean width of preserved sites decreased by 0.8 mm, compared with a decrease of 2.7 mm in nonpreserved sites (a statistically significant finding). Most of the resorption was noted on the buccal aspects, and maxillary sites lost more width than did mandibular sites. Vertically, the preserved sites gained approximately 1 mm, compared with a loss of 1 mm in nonpreserved sites. A height difference of 2.2 mm was reported, which was statistically significant. However, the study also revealed a disadvantage of site preservation: the use of FDBA resulted in less bone by volume in the extraction defect, approximately 28% in the preserved sites compared with 54% in the nonpreserved sites. This was predominantly the result of the presence of residual graft particles.

In a 6-month split mouth study in the dog using bovine collagen (Bio-Oss), Araujo and Lindhe¹¹ histologically noted better dimensional integrity of the alveolar process compared with nonpreserved sites. The authors found that the bovine collagen served as a scaffold for tissue modeling. However, as in the study by Iasella et al., the procedure did not enhance bone volume. Araujo and Lindhe¹¹ concluded that placement of a biomaterial in an extraction socket may modify modeling and counteract marginal ridge contraction that naturally occurs after tooth removal.

In a histomorphometric evaluation of mineralized cancellous allograft (Puros) covered by a bioabsorbable collagen dressing in human extraction defects, Wang and Tsao¹² noted favorable bone growth in the extraction defects.

These studies suggest that the benefits of site preservation procedures are not material specific. Multiple graft materials have been used successfully for site preservation. However, some materials may work better than others.¹³ The benefits of adding a graft material to a fresh extraction socket derive from an alteration in healing through the occupation of space by the graft material, which improves clot stability and reduces clot shrinkage and contraction.

Surgical Techniques for Minimally Invasive Tooth Extraction

Site preservation has been shown to significantly improve alveolar ridge height and width by minimizing physiologic alveolar shrinkage associated with tooth removal.14 However, the surgical procedure for removing a tooth can easily lead to a much more significant amount of tissue loss in a matter of minutes. Fracture of the alveolus, bone removal with the extracted tooth, and trauma to the soft tissues all are complications related to exodontia that can lead to significant hard and soft tissue deficits. This type of damage is also extremely difficult to repair predictably. Therefore, preventing such trauma and performing minimally invasive extractions are critical for sites that require minimal alveolar changes after tooth removal. Minimally traumatic tooth extraction should be considered the first step for successful site preservation. The following procedures are beneficial for all extraction sites but crucial in the esthetic zone¹⁵: