Alveolar bone loss occurs after extraction with loss of a premolar or anterior tooth; the residual supporting alveolar bone loss averages 1.53 mm of crestal bone height and 3.87 mm of buccolingual width, with most of the bone loss occurring at the facial plate. Socket preservation does not completely preserve the original ridge contours but can be an effective means of reducing bone loss following extraction. Attempts to rebuild the alveolar ridge structure after tooth loss often employ the concept of guided bone regeneration, a technique-sensitive procedure that routinely involves placement of particulate bone with or without fixation screws and either a resorbable or a nonresorbable membrane. We present a novel technique for stabilizing a resorbable membrane and underlying particulate graft allowing for predictable bone grafting across multiple edentulous sites.
It is commonly accepted that alveolar bone loss occurs after extraction. Following the loss of a premolar or anterior tooth, the residual supporting alveolar bone loss averages 1.53 mm of crestal bone height and 3.87 mm of buccolingual width, with most of the bone loss occurring at the facial plate.1–3 Alveolar ridge resorption shows a temporal pattern; 50% of the alveolar width resorption is reported at 12 months, and approximately two-thirds of this resorption occurs within the first 3 months.4 Socket preservation does not completely preserve the original ridge contours but can be an effective means of reducing bone loss following extraction. Yet, no socket preservation techniques have been shown to completely preserve the original ridge contours.2 Attempts to rebuild the alveolar ridge structure after tooth loss often employ the concept of guided bone regeneration (GBR).
GBR is a technique-sensitive procedure that routinely involves placement of particulate bone with or without fixation screws and either a resorbable or a nonresorbable membrane. The technique aims to regenerate lost alveolar structure, either for implant-site development or for prosthetic purposes.5 Implants placed into regenerated sites present with similar survival rates as those placed in native bone.6–8
When performing GBR, resorbable membranes have several advantages over nonresorbable membranes for ridge augmentation. Resorbable membranes do not require a second surgery for membrane removal, and they provide decreased patient morbidity. In contrast, some nonresorbable membranes provide enhanced mechanical stability and may be advantageous in the treatment of challenging defects lacking adjacent bone support.1 A study comparing resorbable and nonresorbable membranes noted that resorbable membranes lack stability, which may lead to graft migration, membrane collapse, and insufficient bone formation.5 Multiple other studies conclude that nonresorbable, stabilized membranes present excellent results but have higher rates of membrane exposure during the healing time and require extensive surgical procedures for membrane and tack or screw retrieval.9 Grafting of the buccal-crestal aspect of the implant site can be particularly challenging as external pressure from the flap or occlusal forces may displace the graft laterally and apically, resulting in deficient bone in the desired region. Urban et al10 reported that different techniques using nonresorbable or resorbable membranes with cortical bone pins were able to achieve a more predictable outcome than when pins were not utilized. In a more recent publication, a technique was reported using 2 resorbable vertical mattress sutures to stabilize a resorbable membrane in a single implant site.10 However, there remains no predictable means of achieving bone formation at multiple adjacent edentulous sites without the need for a secondary retrieval surgery. It has been demonstrated in the absence of postoperative complications that results are similar with regard to horizontal thickness and vertical defect fill at 6 months.11
We aim to present a novel technique for stabilizing a resorbable membrane and underlying particulate graft allowing for predictable bone grafting across multiple edentulous sites. The use of both resorbable sutures and membrane eliminates the need for a retrieval surgery, thereby minimizing the associated risk and comorbidities of this secondary surgery.
Following graft placement, with or without simultaneous implant placement, a resorbable membrane is sutured apical to the flap edge to the interior of the lingual flap, with the membrane extending out of the flap (Figure 1). A simple interrupted suture using resorbable suture material is utilized, placing the knot on the interior of the flap adjacent to the membrane. The membrane is placed over the graft material and tucked under the buccal flap. The suture needle then enters the lingual flap superior to the sutured membrane on its interior surface and is looped through the tissue and reenters the flap through the exterior surface (Figure 2). A knot is tied at the interior of the lingual flap to stabilize the suture. The needle is carried over the membrane and through the interior surface of the buccal flap and is looped back through the exterior surface of the buccal flap (Figure 3). Tension is kept on the suture to stabilize the underlying membrane and contained graft material. The needle reenters the interior of the lingual flap and the process is repeated, working from the distal portion of the flap to its mesial extent (Figure 4). The final continuous periosteal strapping suture (CPSS) knot should be tied to the first knot (on top of the collagen membrane), and the flap is closed (Figure 5).
An informed consent discussing the procedure planned and any potential complications was reviewed with the patient prior to their signing the authorization form. Horizontal ridge augmentation utilizing a CPSS technique is initiated after achieving profound anesthesia in the area that will be grafted. Initiation of the procedure begins with a midcrestal incision within the keratinized gingiva utilizing a 15c and 12b scalpel followed by papilla-sparing incisions, if possible (Figures 6 and 7).12 Vertical releasing incisions are required to facilitate proper flap reflection and are extended into the vestibule beyond the mucogingival line. A full-thickness flap is reflected on the buccal and lingual aspects. Approximately 10 to 20 intermarrow penetrations are made into the osseous recipient bed using either a #1/2 or #2 round bur under copious saline irrigation, being careful to avoid adjacent structures (Figure 8). Intramarrow penetrations have been shown to increase new bone formation13 and are considered to be the result of some combination of enhanced angiogenesis,14 a localized increase in bone morphogenic proteins.15 and/or a regional acceleratory phenomenon response to the induced cortical bone trauma.16–18
In order to achieve tension-free soft-tissue primary closure, a scalpel is used to place a periosteal releasing incision ∼5 mm apical to the mucogingival junction and coronal to the desired depth of the membrane by ∼3 mm. This step is critical to allow proper flap advancement and facilitate tension-free, primary closure of the wound. A trimmed, rehydrated, resorbable, cross-linked collagen membrane (Biomend Extend, Zimmer Biomet, Palm Beach Gardens, Fla) is then loosely secured to the lingual flap for ease of handling using 1 to 3 horizontal mattress sutures placed at least 5 mm from the wound margin (4-0 coated Vicryl with FS-2 needle, Ethicon, Somerville, NJ). The reconstituted bone graft (Puros Allograft Particulate, Zimmer Biomet) is mixed in a 4:1 ratio with calcium sulfate (CaSO4; Ace Surgical, Brockton, Mass), the CaSO4i s used as a binder. The bone graft is subsequently placed into the recipient site. About a fourth of the graft is retained for placement toward the end of the procedure. The membrane is adapted over the buccal aspect of the graft while remaining secured to the lingual flap (Figure 9).
Then, CPSSs are placed using a 4-0 resorbable suture with an FS-2 needle (Vicryl Coated, Ethicon). Suturing is initiated on the distal aspect of the lingual flap and coronal to the secured membrane. The suture needle is first passed through the periosteum and connective tissue exiting out the epithelium of the lingual flap. The needle is then reversed back through the same lingual flap ∼3 mm to the mesial aspect, but this time first passing through the epithelium and exiting out the periosteum. A simple surgeon's knot is then tied and a short tail is left behind for future knot placement. After ensuring that the membrane is adapted over the graft, the needle is advanced toward the depths of the buccal flap in the same mesiodistal plane as the initial knot on the lingual flap. The needle penetrates the periosteum coronal to the tucked membrane and apical to the periosteal releasing incision. The needle is advanced in a distomesial direction passing from periosteum to connective tissue back through periosteum, emerging mesial to the initial penetration point. The needle is then advanced again toward the lingual flap, mesial to the initial knot, in a horizontal mattress fashion passing through periosteum to connective tissue to epithelium and back through the epithelium and exiting out the lingual flap periosteum. This technique is continued, alternating between the lingual and buccal flaps, which amounts to a horizontal running internal mattress suture, until the mesial aspect of the membrane is reached. With each pass, tension of the suture should be ensured to achieve firm adaptation against the membrane and the underlying graft. It is critical to ensure that needle entry and exit points on the buccal flap remain apical to the periosteal releasing incision to ensure continued tension on the sutures during flap advancement. After the last penetration of the buccal flap, the remaining allograft-CaSO4 mixture is tucked under the membrane to overbulk the buccocoronal aspect of the site as needed, and a final surgeon's knot is placed using the tail of the suture thus terminating the continuous suture (Figures 10 and 11). In an anatomically sensitive area, such as the mandibular premolar area where the mental nerve exits the mental foramen, the strapping suture should follow the coronal aspect of the periosteal release at least 5 mm coronal to the mental foramen.
After completing the CPSS, the tension-free flap is carefully approximated and sutured with the surgeon's choice of suture material utilizing a combination of horizontal mattress sutures and single interrupted sutures to achieve primary closure (Figure 12). The patient returns for a postoperative check 2 weeks after surgery, and the incision line is closed with no evidence of inflammation or membrane exposure noted. Six months after graft healing, Cone-beam computerized tomography (CBCT) slices demonstrate the increased width achieved with the original facial plate, showing a slightly greater radiopacity as compared to the overlaying mature graft (Figure 13).
In a demonstrated case (Figures 14 through 20), the lower second premolar was planned for extraction due to severe periodontal disease that resulted in loss of the buccal plate and Class III mobility. The treatment plan included implant placement at sites #29 and #31 and subsequent restoration with a 3-unit implant-supported fixed bridge. Preoperative cone-beam computed tomography (CBCT) demonstrates the lack of buccal plate and inadequate ridge width to accommodate prosthetically driven implant placement (Figure 14). Following full-thickness flap elevation and atraumatic extraction of the second premolar, evaluation of the site revealed a deficient ridge width due to loss of the buccal plate (Figure 15). In order to perform GBR in this anatomically sensitive region, the mental nerve was first identified followed by the GBR technique utilizing CPSS, with special care taken to not apply tension or pressure on the adjacent mental nerve (Figure 16). In the region of #31, vertical bone growth was indicated, and tenting screws were utilized. The patient returned for a postoperative check 2 weeks after surgery, which revealed that primary closure was maintained and there were no signs of edema/erythema or clinical evidence of inflammation. Six months after GBR, CBCT demonstrated the increased ridge width that was achieved with the CPSS technique (Figure 17). A subsequent reentry surgery for implant placement at the site of #29 demonstrated conversion of the narrow atrophic ridge into a wide ridge that was able to accommodate a prosthetically driven implant placement (Figures 18 through 20). Without grafting, this patient would have required small-diameter implants and/or compromised implant angulation.
Horizontal ridge augmentation of atrophic alveolar ridges for dental implant placement has been successfully performed with both resorbable and nonresorbable membranes. Multiple authors support the use of various means for membrane and underlying graft stabilization. However, most fixation techniques involve nonresorbable materials, such as tacks or screws, that later require a secondary surgery for their retrieval.19,20 A technique utilizing periosteal vertical mattress sutures (PVMSs) for fixing the membrane and stabilizing the bone graft was recently proposed for single implant sites by Urban et al.10 Similar to the PVMS technique, the CPSS technique minimizes the risks and comorbidities observed with the use of fixation screws or pins through the use of resorbable sutures for membrane fixation and graft stabilization. However, the CPSS technique has been used successfully across multiple adjacent implant sites to optimize implant-site development by minimizing apical and lateral graft migration.
Urban et al10 reviewed the PVMS technique and concluded that the tensile strength of the suture, the lack of apicocoronal stabilization, and the duration of fixation may be limiting factors for that technique. The tensile strength of the resorbable suture material decreases over time, and consequently, the resultant strength of the membrane fixation and graft stabilization can be affected. The suture's tensile strength is approximately 50% to 60% of its initial strength after 1 week and approximately 20% to 30% after 2 weeks in vivo. This means a loss of three-quarters of its tensile strength over the first 2 weeks. In comparison, coated Vicryl, according to the manufacturer, sustains 75% tensile strength after 2 weeks and 25% after 4 weeks. Even with no evidence in the literature for the amount of time required for membrane fixation, it may only be necessary for the initial weeks of healing until a preliminary bone matrix is established. An additional limitation of the PVMS technique is that it is only possible to fix the membrane by means of a linear-guided suture, thus resulting in possible migration of the particulate graft material in an apicocoronal direction. Therefore, for multiple ridge defects the use of pins is still recommended according to the authors because the PVMS technique may not provide sufficient graft stabilization for multiple site defects. The time of fixation is also limited by the biodegradation period of the resorbable suture material by hydrolysis, which initially leads to loss of tensile strength and later to loss of mass. The suture material used in the case shown was Monocryl (clear) 6-0 (Ethicon), a monofilament resorbable copolymer of glycolide and epsilon-caprolactone. According to the manufacturer, the time for complete resorption is between 91 and 119 days, whereas the complete resorption time for coated Vicryl is 56–70 days (see http://academicdepartments.musc.edu/surgery/education/resident_info/supplement/suture_manuals/absorbable_suture_chart.pdf). In contrast to the PVMS technique, the CPSS technique allows for proper apicocoronal fixation of the graft due to the stringent fixation of the periosteum to the apical portion of the membrane, but in contrast to the PVMS technique, the CPSS technique utilizes a suture material that maintains its tensile strength for a longer period of time, which may be crucial for membrane and graft stabilization.
The procedure presented here is an alternative to different GBR membrane stabilization techniques that have been reported in the literature. The technique is limited by the tensile strength and resorption rate of the suture utilized. Nevertheless, the technique was found to have excellent, predictable clinical results and minimal rates of complications. Future studies should focus on comparing the CPSS technique with other membrane fixation techniques, such as screws or tacks.
The authors declare no conflicts of interest.