CC
A 37-year-old female is referred by her general dentist for consultation to have tooth #19 extracted. She is interested in a dental implant.
HPI
Tooth #19 has had previous endodontic therapy. Recently, the patient started to have pain while chewing. Endodontic evaluation found a poor prognosis because of root fracture. She denies any swelling or other symptoms.
PMH/PDH/medications/allergies/SH/FS
The medical history is not contributory. The patient has had routine dental care by her general dentist.
Examination
Examination of the temporomandibular joint is within normal limits. (Good range of motion is important in placement of posterior dental implants.) There are no extraoral or intraoral soft tissue lesions, swelling, or masses. Tooth #19 is missing the crown and has a temporary restoration ( Fig. 38.1 ).
Imaging
On the panoramic radiograph, a periapical radiolucency can be seen associated with mesial and distal roots of the endodontically treated tooth #19. The radiolucency appears to be a few millimeters away from the inferior alveolar nerve ( Fig. 38.2 ).
Assessment
Failed root canal therapy and nonrestorable tooth #19 with a periapical abscess.
The patient is interested in a dental implant. The clinical and radiographic findings are fully explained to the patient. The risks, benefits, and alternative treatment considerations are discussed. Alternative options include extracting the tooth without replacement or receiving a bridge or a partial denture. The plan for ridge preservation (with human allograft) and delayed implant placement is presented and accepted by the patient.
Treatment
Under intravenous sedation anesthesia, a sulcular incision is made, and a buccal mucoperiosteal flap is elevated ( Fig. 38.3 A) to visualize and protect the buccal cortical plate. Vignoletti and colleagues report better outcomes when the flap is elevated for alveolar ridge preservation (ARP) than with a flapless technique. Clinical studies by Siu et al. (2022) and a meta-analysis by Lee et al. (2018) found that both flap and flapless alveolar ridge preservation techniques had similar crestal ridge width, height, and percentages of vital bone at 4- to 6-month follow-up, which is in agreement with previous animal studies conducted by Araujo and Lindhe.
A 1702 bur is used under loupe magnification, and the tooth structure is removed from the buccal aspects of the roots under copious sterile saline irrigation (to prevent overheating of the bone, which can lead to further bone loss). In essence, instead of a buccal trough alveolectomy, a buccal odontotomy is performed to keep the buccal cortical bone fully intact. The crown and the roots are sectioned from buccal to lingual ( Fig. 38.3 B).
Next, a periotome ( Fig. 38.3 C) is used on the mesial and distal of each root to loosen the segment ( Fig. 38.3 D). The roots are completely removed ( Fig. 38.3 E), and the granulation tissue in the apex is fully cleaned with a curette. Throughout the process, care is taken not to damage the cortical buccal plate. The extraction site is irrigated with copious sterile saline. A round bur is used to decorticate the inside of the socket to induce bleeding. This leads to better early vascularization and release of osteoprogenitor cells. At this time, no human clinical trials have been conducted to study the benefit of decortication. Several case reports and clinical studies have found success with this approach, but other studies found no improvement.
A mineralized corticocancellous allograft was prepared with the use of leukocyte, and platelet-rich fibrin (L-PRF) to make “sticky bone.” As described by Cortellini et al., two 9-mL glass-coated plastic tubes (red cap) and one 9-mL plastic tube without coating (white top) were collected from the patient. These were centrifuged immediately at 408 g RCF. The centrifugation was interrupted after 3 minutes, and the white cap tube was removed. The remaining red cap tubes were centrifuged for 9 additional minutes (completing the cycle of 12 minutes). Immediately after removing the white cap tube, the yellow liquid (liquid fibrinogen) above the red blood cell layer was collected with a sterile syringe. The red cap tubes were removed after completion of centrifugation (12 minutes), and the L-PRF membranes were prepared following the protocol described by Temmerman et al. The PRF clot was transformed into a membrane by gentle compression in the PRF box. These membranes were sliced into small fragments using scissors and mixed with the graft particles. The liquid fibrinogen was then added. After gentle modeling, the graft was ready to use. Fig. 38.3 F to I describe this process. Alveolar ridge preservation through grafting reduces the amount of horizontal and vertical bone resorption after tooth extraction by providing a scaffold for additional bone to regenerate and fill the space. L-PRF can be used as a grafting material in alveolar ridge preservation because of its high concentration of platelets, leukocytes (white blood cells), and lymphocytes (T cells, B cells, natural killer cells), which contribute to developing a strong mesh matrix that releases growth factors and proteins to help stimulate the wound healing and cell proliferation process. Studies of the changes in bone height and width found improved soft tissue healing, increased bone formation, and slightly reduced loss of alveolar width in the PRF group. Clark et al. (2018) conducted a randomized clinical trial of PRF and allografting on ridge preservation and found that PRF+ allografting demonstrated significantly less ridge loss both for height (1 ± 2.3 mm) and width (1.9 ± 1.1 mm) compared with spontaneous healing (3.8 ± 2.0 mm height). The combination was superior to both PRF (1.8 ± 2.1 mm height) and allograft (2.2 ± 1.8 mm height) placement alone as well. However, studies of changes in bone volume found little difference in outcomes between grafting with L-PRF and normal healing with blood clotting. In addition, studies of new bone percentage and bone density both saw improvement in the PRF treatment groups. Although there may not be significant difference in bone loss after tooth extraction, L-PRF can provide overall ARP benefits for many patients.
The bone is grafted in the extraction socket ( Fig. 38.3 J). A 5-mm subperiosteal pocket is made on the buccal and lingual to allow the membrane to be tucked underneath the flaps. Studies have demonstrated a statistically significant difference in favor of use of membrane (Lekovic and colleagues). In the current case, a nonresorbable, high-density polytetrafluoroethylene (d-PTFE) membrane is chosen and used to cover the graft. d-PTFE membrane does not need primary closer over it; this minimizes displacement of the keratinized tissue, which is beneficial for keeping better-attached gingiva around the future implant. d-PTFE has extensive cardiovascular applications in heart valves and vascular grafts. It does not induce secondary inflammation. The flaps are sutured closed ( Fig. 38.3 K).
After recovery, the patient was discharged to her husband. She was provided detailed instructions and prescribed amoxicillin (500 mg) three times per day for 3 days. The d-PTFE membrane will be removed in 3 weeks, and the site should be ready for placement of the dental implant in 4 months.
Complications
The main complication of ARP is infection (which also causes loss of graft). Fortunately, infections are rare (appearing in <5% of cases); however, when they occur, removal of the graft material typically is required. Optimizing the patient’s oral hygiene and appropriate use of perioperative antibiotics may help decrease the incidence of infection. Most often, teeth removed during the extraction are very compromised and endodontically treated. Therefore, it is common for the roots to break into small segments. Remnants of roots accidentally left in place can lead to delayed infection or can compromise the future implant.
Periotomes can be driven into adjacent vital structure, such as the inferior alveolar nerve or sinus cavity, or can damage the adjacent teeth. It is essential that the periotomes be navigated with the utmost care and control. Copious irrigation is mandatory during the odontotomy to minimize heat generation. Excessive heat can damage the buccal plate and lead to unfavorable bone resorption.
Tension-free closure of the flap and appropriate use of membrane can reduce the incidence of flap retraction or dehiscence and subsequent loss of grafted bone granules. Wound healing can be compromised secondary to pressure applied by a removable partial denture. All attempts should be made to minimize pressure on the grafted site from a removable prostheses. Patients need to be taught to modify their diets to avoid function on the surgical site for 4 weeks and to undertake appropriate hygiene measures.
Discussion
Preservation of hard and soft tissue at the time of extraction is essential in achieving better esthetic and long-term results for dental implants. The alveolar process is a tooth-dependent tissue. The shape and volume of the ridge is dictated by the tooth shape, axis, anatomy, and position. After dental tooth extraction, bone remodeling and shrinkage often occur because the alveolar process and bundle (lamellar) bone that support the teeth resorb. Most of the resorption (typically in an apical and lingual direction) takes place in the first 3 months; however, changes are seen up to 1 year after surgery, resulting in approximately 50% reduction in the buccolingual dimensions of the alveolar ridge, according to Schropp and colleagues.
The process of wound healing after extraction involves four main stages: hemostasis and coagulation, inflammation, proliferation, and modeling and remodeling. Hemostasis and coagulation occur in the first 24 hours after extraction when a blood clot fills the socket. The clot consists of red and white blood cells and platelets in a matrix of fibrin. The clot has two functions, to protect the denuded tissues and to serve as a provisional matrix for cell migration. Next, after 2 to 3 days, inflammatory cells (neutrophils and monocytes) migrate to the site and cleanse the wound of bacteria and necrotic tissue through phagocytosis. As healing progresses, macrophages migrate into the area and continue debridement but also release growth factors. These growth factors promote the proliferation of fibroblasts (produce collagen) and endothelial cells (produce blood vessels), and granulation tissue forms (cellular and vascular rich tissue). After 14 to 21 days, the proliferative phase occurs marked by rapid deposition of a provisional collagen matrix and subsequent woven bone. Woven bone is a type of provisional bone that is not capable of load bearing and needs to be replaced with a more mature bone type. The proliferative phase is also marked by development of the primary osteon when bone completely surrounds individual blood vessels. Last, at around 30 days after the tooth extraction, the modeling and remodeling phase occurs. This involves replacing woven bone with lamellar or bone marrow and takes several months. The final phase of healing is quite variable among individuals and the degree of modeling (changing shape and height of bone) versus remodeling (bone changes without alterations in shape or architecture of bone) varies as well.
A systematic review conducted by Moslemi et al. (2018) found that addition of a growth factor called recombinant human bone morphogenetic protein 2 (rhBMP-2) to an absorbable collagen sponge (ACS) is more effective in preserving the alveolar ridge compared with ACS alone, especially in cases with more than 50% buccal bone dehiscence. These results are likely because of rhBMP-2’s ability to stimulate angiogenesis (blood vessel formation) and stem cell proliferation, migration, and differentiation. However, the cost-to-benefit analysis of ridge preservation with rhBMP-2 must be carefully considered because the research results do not necessarily translate to improved clinical outcomes.
In addition, Tonetti et al. conducted a study to compare spontaneous bone healing to ARP with bone grafting alone after extractions. They found that 1.5 to 2.4 mm of horizontal, 1 to 2.5 mm vertical buccal, and 0.8 to 1.5 mm of vertical lingual ridge resorption can be avoided using ARP via bone grafting. A systematic review by Vignoletti and colleagues reports that the changes in the horizontal dimension have benefited the most by the ARP techniques evaluated. They found the bone loss in the horizontal dimension to be the most important consequence during the first 3 to 6 months of healing after tooth extraction; this loss ranged from −0.16 to −4.50 mm. The results of their meta-regression analysis of nine studies concluded that some degree of bone modeling and remodeling occurs after tooth extraction; however, different ridge preservation procedures resulted in significantly less vertical and horizontal alveolar bone contraction. This review could not make a recommendation for the type of biomaterial or surgical procedure used, but the use of barrier membranes and flap (rather than flapless) surgical procedures demonstrated better results. In conclusion, these researchers found a difference (D) of −1.47 mm in height and −1.83 mm in width, with more significant bone loss seen in the control group without bone grafting. A study by De Angelis et al. (2022) used digital three-dimensional models to compare the quantity of bone filling extraction sockets in ARP with a bovine graft compared with standard healing. They found a significant different ( P = .004) in bone loss between the standard (106.41 ± 24 mm 3 ) and ARP groups (62.66 ± 17.5 mm 3 ), supporting the use of bone grafting for ARP.
The approach used to remove the tooth and preserve the site substantially affects the quality of the bone and soft tissue at the time of implant placement. The rationale behind extraction site preservation with bone grafting is to provide a stable environment for osteoconduction to take its natural course. Allograft used in this case is just a scaffold, which still requires the natural turnover of bone as the adjacent osteocytes migrate from the native tissue to lay new vital bone within the graft and ultimately replace it. This cannot effectively take place without having healthy and vital neighboring bone. The ultimate goal is preservation of the soft tissue volume and architecture at the site by having a stable bony foundation to support it.
There is no one graft material that can be recommended over others for every case. An understanding of the physical and biologic properties of the graft material and individualization of treatment planning are necessary in choosing the most appropriate material in each case.
Graft material classification
Bone grafting is a technique designed to aid alveolar ridge augmentation and reduce bone loss after tooth extraction by providing a scaffold to enhance hard and soft tissue growth. Bone grafting with different materials is a form of tissue engineering designed to repair and improve structural deficiencies. For engineering functional tissues capable of providing long-term clinical benefit, the tissue cells must have sufficient spatial and temporal signals to promote growth, differentiation, and synthesis of an extracellular matrix (ECM) capable of supporting structural, functional, and mechanical needs. Tissue engineering approaches are based on cells, the ECM, and signaling systems. Biomaterials are central to tissue engineering in ridge augmentation and different scaffold materials have been developed as ECM analogues to support cell attachment and provide cues for spatial and temporal bone development (induction).
The potential benefits of the different materials and techniques used for ARP are still debatable, and very few well-designed studies address these issues. No scientific guidelines have been established with regard to biomaterials or surgical techniques to date. Several studies have compared different methods of grafting for ARP, including autologous, allograft, xenograft, and alloplastic materials, generally showing similar results. In particular, xenografts and allografts were associated with superior ridge preservation. It is the authors’ opinion that the technique used at the time of extraction to keep the buccal bone intact is the most important step taken, when possible. Araujo and Lindhe also report that resorption of the buccal bone plate is a main cause of the bone loss. The buccal plate generally experiences greater bone modeling and resorption than the lingual because the buccal crest is made of bundle bone, and the lingual is made of both bundle (alveolar) and cortical (stronger, compact) bone.
Autograft
Autograft refers to viable cortical or cancellous bone grafting when the source of the graft is the patient. This is the gold standard, and it has osteoconductive, osteoinductive, and osteogenesic benefits. Autogenous grafts include cortical, cancellous, and corticocancellous bone with cancellous bone providing rapid revascularization and integration in the socket. However, a second surgical site usually is required to obtain the bone from sites such as the symphysis, external oblique ridge, maxillary tuberosity, edentulous ridges, and exostoses, and this can lead to increases in morbidity and recovery time for the patient. At times, it is possible to simply harvest bone from adjacent bony tissue without a significant increase in morbidity.
Allograft
Allograft refers to bone graft from cadavers in the same species. These are available from licensed tissue banks. The cadavers are screened for malignancy, hepatitis B and C viruses, HIV, and lifestyle factors that may place the donor at a higher risk category for transmittable diseases. The bone is obtained in an aseptic setting in the operating room. Patients should be advised of the remote possibility of disease transmission despite the lack of any documented cases. The patient’s religious preference also needs to be considered. The graft material is available in the demineralized freeze-dried bone allograft form, mineralized freeze-dried form, or a mixture of the two forms. It can also be selected in cortical or cancellous forms. These differ in the time it takes for the grafted bone to remodel and be replaced by the patient’s own vital bone. (The process of turnover starts with osteoblasts surrounding the graft particles with formation of osteoid (nonmineralized bone) around the particles with osteoclasts starting to resorb the particle. As the process continues (over a few months), the particles are turned over with the replacement of the graft particles with host bone. In general, demineralized bone is remodeled faster, and mineralized cortical bone takes longest to turn over. Therefore, the surgeon’s understanding of these properties is important in choosing the right graft for a particular case ( Table 38.1 ).
