The “Combo Technique”: A Case Series Introducing the Use of a d-PTFE Membrane in Immediate Postextraction Guided Bone Regeneration

Ridge preservation or guided bone regeneration (GBR) in postextraction sockets aims to establish adequate bone availability to allow for implant placement. According to the American Academy of Periodontology, ridge preservation is defined as “a surgical procedure aimed at preventing ridge collapse and preserving ridge dimension after tooth extraction, typically done for purposes of implant site development,” whereas GBR is defined as “the surgical augmentation of a resorbed ridge.”¹ 

Traditionally, these procedures depend on the use of bone replacement grafts in combination with membranes that act as barriers to prevent the downgrowth of epithelium²  and facilitate the repopulation of the defect with cells capable of increasing the osteogenesis potential.³  Membranes can be broadly classified as nonresorbable and resorbable.⁴  Whereas resorbable membranes are associated with less postoperative complications, nonresorbable membranes provide superior space maintenance.⁵ 

Following tooth extraction, without ridge preservation, approximately 5–7 mm of the horizontal and 1 mm of the vertical bone is lost.^6–8  This observed bone remodeling occurs primarily within the initial 3 months, but it can continue up to 12 months after extraction and may compromise the functional and esthetic treatment outcome. Therefore, it is of paramount importance to preserve the bone dimensions or predictably augment the alveolar ridge following the physiologic bone remodeling caused by a tooth extraction.

However, after tooth extraction and due to the soft tissue dehiscence, 2 options are available: to achieve primary closure over the regenerating defect by flap reflection and advancement or to accept healing via secondary intention and leave exposed a collagen membrane covering the bone graft.

Establishing primary closure usually requires the use of periosteal and vertical releasing incisions or release of the lingual flap^9,10  to facilitate flap advancement,¹¹  thus increasing postoperative morbidity. The local anatomy is also distorted with translocation of the mucogingival junction, and the amount of keratinized tissue is reduced. Furthermore, extraction sockets subjected to full thickness flap coverage present increased resorption of the buccolingual width and less keratinized tissue width compared with the sites healing with secondary intention.¹²  At the same time, full-thickness flap coverage results in reduced resorption of the vertical bone height buccaly.¹² 

On the other hand, detrimental can be the effects of membrane exposure, primarily for nonresorbable membranes, because infection can disturb bone formation.¹³  Early exposure causes an increase in bacterial count, graft exposure, and membrane degradation by hydrolysis.¹⁴  Non–cross-linked or low–cross-linked membranes, if exposed to the oral environment, become ineffective to act as barriers to the epithelium. Oh et al, in 2003, demonstrated that membrane coverage is an important determinant of GBR success, as sites that experience membrane exposure present with less linear bone fill and bone to implant contact after 16 weeks of healing compared with sites with no membrane exposure.¹⁵ 

An alternative is the use of a dense polytetrafluoroethylene (d-PTFE) membrane. The d-PTFE membrane presents with a nanoporous, textured surface that enhances its stability in the tissue and facilitates its removal a few weeks after placement. Furthermore, it is established that a surface roughness from 10 to 100 μm promotes adhesion of bacteria.¹⁶  The d-PTFE membranes, with a pore size of less than 0.3 μm, are therefore expected to be impervious to bacteria,¹⁷  protecting the underlying bone graft material. Therefore, the d-PTFE membrane may be left exposed in the oral cavity with a reduced risk of complications, such as infection and loss of bone graft material. Although the d-PTFE membrane can be used alone for ridge preservation, the exposed d-PTFE membrane usually needs to be removed in 4–6 weeks. In large defects with significant deficiencies, for instance, dehiscence of buccal or lingual plates, a long-standing barrier protection of primary closure over a resorbable membrane is desired.

In this series of case presentations, the authors introduce a novel technique for immediate postextraction GBR, the “combo technique,” using the combined use of a collagen membrane over the bone dehiscence and socket and a d-PTFE membrane at the place of soft tissue dehiscence in type I, II, and III extraction sockets.¹⁸  The d-PTFE is removed 4–6 weeks postoperatively.

This technique offers the advantages of maintaining an intact collagen membrane that supports the site for the entire regenerating period while avoiding the need for obtaining primary closure. It provides excellent bone dimensions and keratinized tissue formation without the soft tissue distortion associated with primary closure.

1. After tooth extraction, the socket is debrided and granulation tissue is removed.

2. The bone graft is hydrated and gently packed in the socket.

3. A collagen membrane is secured over the socket and graft.

4. A d-PTFE membrane is placed over the collagen membrane at the site of soft tissue dehiscence and left to heal exposed.

5. The postoperative regimen includes amoxicillin 500 mg 3 times a day, or in the case of allergy, clindamycin 300 mg for 7 days and chlorhexidine 2 times a day for a minimum of 2 weeks.

6. The d-PTFE membrane is atraumatically removed 4–6 weeks postoperatively.

A 68-year-old female patient, American Society of Anesthesiologists (ASA) 2, presented with partial edentulism of #30 and #31 and questionable prognosis for #29 even after nonsurgical periodontal treatment. Tooth #29 was extracted trying to preserve the integrity of the bony walls of the socket, and a full-thickness flap was reflected buccal and lingual of #28 extending distal to #29 and #30. The sites #29, #30 were subjected to GBR in preparation for implant placement at #29, #30 (Figure 1a). The socket of #29 was carefully debrided, and at the site of #30, corticotomies were prepared with a round carbide bur 1/2 under sterile saline irrigation. The sites #29, #30 were packed with allograft, a resorbable collagen membrane was secured over the graft using continuous periosteal strapping sutures,¹⁹  and a nonresorbable d-PTFE membrane was placed over the collagen membrane at the site of the soft tissue dehiscence due to the extraction of #29. With the use of 4-0 PTFE sutures (horizontal mattress and single interrupted), primary closure was obtained at site #30, and at site #29, the d-PTFE membrane was left transmucosally (Figure 1b). The postoperative regimen included amoxicillin 500 mg 3 times a day for 7 days and chlorhexidine 2 times a day for a minimum of 2 weeks.

The d-PTFE membrane was removed after 4 weeks atraumatically (Figure 1c). On removal of the d-PTFE membrane, immature connective tissue proliferation was observed that reached complete maturation and epithelialization by 8 weeks, becoming a wide zone of keratinized tissue.

After 3 months of healing, a cone beam computed tomography scan was obtained for the mandible and showed buccolingual widths of 12.8 mm at #29 and 10.8 mm at #30 and available height superior to the inferior alveolar nerve canal of 16 mm at both #29 and #30 (Figure 1d). Two bone level SLActive implants were placed (for #29: 4.1 × 12 mm; for #30: 4.8 × 12 mm) with adequate primary stability (30 Ncm), and healing abutments were seated on both implants (Figure 1e and f). After 3 months, implants #29 and #30 were restored with a screw-retained prosthesis (Figure 1g and h), and after 18 months, stable bone levels are noted for #29 and #30 (Figure 1i).

A 51-year-old male patient, ASA 2, presented with prosthetically deemed unrestorable #23, #24, #25, #26 due to caries, periapical lesions, and inadequate restorative space. The teeth were extracted after a full-thickness flap elevation buccal and lingual extending from #22 to #27, and the sites were grafted in preparation for implant placement at #23, #26 (Figure 2a). The sockets were debrided, and corticotomies were prepared under sterile saline irrigation with a round carbide. The sites were packed with allograft, a resorbable collagen membrane was secured over the graft using continuous periosteal strapping sutures,¹⁹  and a nonresorbable d-PTFE membrane was placed over the collagen membrane. After periosteum release incisions, the flaps were approximated with the use of 4-0 PTFE sutures (horizontal mattress and single interrupted), and the d-PTFE membrane was left transmucosally (Figure 2b). The postoperative regimen included amoxicillin 500 mg 3 times a day for 7 days and chlorhexidine 2 times a day for a minimum of 2 weeks.

The d-PTFE membrane was removed after 6 weeks atraumatically (Figure 2c). On removal of the d-PTFE membrane, immature connective tissue was noted that became a wide zone of keratinized tissue by 8 weeks (Figure 2f).

After 3 months of healing, a cone beam computed tomography scan was obtained for the mandible that demonstrated buccolingual width of 7 mm and adequate available height (Figure 2d). Two bone level SLActive implants were placed (for #23: 3.3 × 14 mm; for #26: 3.3 × 14 mm) with adequate primary stability (30 Ncm; Figure 2e). After 3 months, second-stage surgery was performed for implants #23 and #26, and a few weeks later they were restored with a screw-retained bridge prosthesis (Figure 2f). Twelve months later, stable crestal bone levels were observed for #23, #26 (Figure 2g).

A 48-year-old male patient, ASA 1, presented with periodontal disease, severe horizontal bone loss for #30, #31, and class 2 mobility (Figure 3a). After initial periodontal treatment and due to poor prognosis, the teeth were extracted trying to preserve the integrity of the bony walls of the socket, and the sites were subjected to GBR in preparation for implant placement at #30, #31 (Figure 3b). The sockets were debrided, the sites were packed with allograft, a resorbable collagen membrane was secured over the graft, and a nonresorbable d-PTFE membrane was placed over the collagen membrane at site #31 and a collagen sponge at site #30. The membranes were secured with the use of 4-0 PTFE sutures and Vicryl 4-0 (cross horizontal mattress and single interrupted), and the d-PTFE membrane was left exposed (Figure 3b). The postoperative regimen included amoxicillin 500 mg 3 times a day for 7 days and chlorhexidine 2 times a day for a minimum of 2 weeks.

The d-PTFE membrane was removed after 6 weeks atraumatically (Figure 3c). When the d-PTFE membrane was removed, immature connective tissue was noted that become keratinized gingiva by 8 weeks after extraction (Figure 3f).

After 3 months of healing, a cone beam computed tomography suggested a buccolingual width of 9 mm at #31 and 8 mm at #30 and 8–10 mm of available height (Figure 3d). Two bone level implants were placed (for #30: 4.7 × 10 mm; for #31: 4.1 × 8 mm) with adequate primary stability (30 Ncm; Figure 3e). After 3 months, second-stage implant surgery was performed for implants #30 and #31, and a few weeks later they were restored with two screw-retained crowns (Figure 3f and g). Twelve months later, stable crestal bone levels were observed for #31, where the d-PTFE membrane was placed, whereas remodeling was observed mesially of #30, where a collagen sponge was used (Figure 3h).

A 73-year-old male patient, ASA 2, presented with a sinus tract, probing pocket depth of 10 mm and bleeding on probing on the labial aspect of #8, which was endodontically treated 2 years before the consultation. In addition, class 2 mobility was noted, and the radiographic examination revealed periapical pathology, root resorption, and loss of the lamina dura. Following local anesthesia, #8 was extracted to try to preserve the integrity of the bony walls of the socket with the use of periotomes and extraction forceps (Figure 4a). Granulation tissues were removed, and the socket was irrigated with saline. Due to the absence of the labial bone, the site was prepared for a delayed implant placement using an allogenic bone graft and a collagen membrane secured under the buccal and lingual flap to avoid reflection, which was covered by a nonresorbable d-PTFE membrane (Figure 4b). The membranes were secured with two crossed horizontal mattress sutures and a single interrupted 5/0 Vicryl suture (Figure 4c). The postoperative regimen included amoxicillin 500 mg 3 times a day for 7 days and chlorhexidine 2 times a day for a minimum of 2 weeks.

The d-PTFE membrane was removed 6 weeks after the extraction, and uneventful healing was noted (Figure 4d).

After 7 months of healing (Figure 4e), adequate bone was available (Figure 4f) for a 3.6- × 13-mm bone level implant that was placed with a torque of 25 Ncm, and submerged healing was decided (Figure 4g). Four months later, second-stage implant surgery was completed, the bone level was stable, and a healing abutment of 4.5 mm height was placed until the fabrication of the cement-retained implant restoration. One year after its placement, the crestal bone levels around the implant remain stable (Figure 4h).

In this report, the “combo technique” for immediate postextraction GBR is introduced. This technique uses a resorbable collagen membrane and a d-PTFE membrane at the site of soft tissue dehiscence that is removed a few weeks postoperatively.

The added use of the d-PTFE membrane prevents the early degradation of the collagen membrane and serves as a barrier. The barrier effect of the PTFE membrane to the epithelial proliferation was investigated by Laurito et al.²⁰  A d-PTFE membrane in combination with hydroxyapatite was used in extraction sockets. After 28 days of healing, the membrane was removed atraumatically, and a biopsy of the healing site was obtained. Dense connective tissue was noted beneath the PTFE membrane with no epithelial migration, thus confirming the role of the PTFE membrane as a barrier to the epithelial proliferation.

When it comes to the effectiveness of the d-PTFE membrane in ridge preservation, Walker et al²¹  using cone beam computed tomography concluded that the use of the d-PTFE membrane resulted in improved retention of the height of the buccal plate compared with natural healing. However, a significant difference in ridge preservation width was not observed. In contrast, Sun et al²²  concluded that the combined use of d-PTFE membrane and allograft resulted in superior preservation of the ridge width 1 mm below the crest compared with natural healing of both molar and nonmolar sites. In addition, the combined use of the biomaterials resulted in a significantly reduced need for bone augmentation at the time of implant placement.

In terms of bone formation in extraction sockets using allograft and a d-PTFE membrane, Cheon et al,²³  using histology, reported 28% new bone, 27% residual graft particles, and 43% fibrous tissue. In addition, implants placed in the healed sites presented minimal alveolar crest changes after 1 year in function. In the same line, Borg et al²⁴  demonstrated that the combination of mineralized freeze-dried bone allograft (FDBA) and demineralized freeze-dried bone allograft (DFDBA) along with a d-PTFE membrane resulted in significantly increased vital bone (36%) compared with defects treated solely with FDBA. In addition, the bone graft combination resulted in reduced presence of residual graft particles (18% vs 27%). With the use of anorganic bovine bone mineral, Bakhshalian et al²⁵  observed 40.1% bone and 12% residual graft after a mean of 21 weeks. Furthermore, the healing time was not found correlated with the new bone or the residual graft material. Similarly, Min et al²⁶  concluded that the combination of anorganic bovine bone and d-PTFE membrane in postextraction sockets results in 37% vital bone and 12% residual graft. Similarly to what Bakhshalian et al²⁵  reported, the percentage of vital bone formation was not correlated with the healing time. Finally, the use of hydroxyapatite in combination with a d-PTFE membrane resulted histomorphometrically in 25% new bone, 28% soft tissue, and 15% graft particles.²⁷ 

It is evident from the above that the d-PTFE membrane can successfully act as a barrier when used immediately after extraction, whereas its use simultaneously results in preservation of the alveolar ridge availability, supporting the new bone formation in the extraction socket. This technique is only appropriate for use when at least 1 bony wall is present and has not been used for vertical ridge augmentation.

Future investigations should compare the long-term dimensional bone and soft tissue alterations after extraction and patient-reported outcomes following the d-PTFE membrane “combo technique” in immediate postextraction GBR with conventional GBR or ridge preservation after extraction using a powered randomized clinical trial design and performing histologic assessment of the bone formation. In addition, further studies should evaluate the degree of osseointegration and alveolar ridge resorption following implant placement.

Despite the limitations of the current investigation, such as the lack of a control procedure, the lack of random allocation to treatment, and the convenience sample used for this case series, the use of a d-PTFE membrane over a collagen membrane in postextraction sockets prevents the early degradation of the resorbable membrane and preserves its integrity. It can thus serve as a viable alternative to healing by primary intention. At the same time, the use of a d-PTFE membrane prevents the translocation of the mucogingival junction and the distortion of the local anatomy resulting from full-thickness flap reflection and coronal advancement to achieve primary closure while creating a wide zone of keratinized gingiva.

Abbreviations

ASA:

American Society of Anesthesiologists

DFDBA:

demineralized freeze-dried bone allograft

FDBA:

mineralized freeze-dried bone allograft

GBR:

guided bone regeneration

PTFE:

polytetrafluoroethylene

The authors declare no conflicts of interest.