Double-up Technique for Correction of Ridge Contour Deficiencies

Double-up Technique

Indications and Contraindications

Indications for what the authors call the "double-up" technique include buccal ridge contour defects on implant sites, contour defects composed of either thin soft tissues (<1 mm) or thin buccal bone (<2 mm), or the combination of thin bone and soft tissues. Contraindications are alveolar bone dehiscence defects that can lead to inadequate bone coverage of the dental implant. The ossifying properties of the ribose-based cross-linked multilayered dual soft- and hard-tissue absorbable scaffold, or "dual absorbable scaffold" (DAS), used in this technique require residual alveolar bone to promote bone thickening; therefore, this type of defect would need conventional guided bone augmentation procedures.

Site Assessment

Sites for contour augmentation ideally must show a concavity when observed from an occlusal view. It is important to have adequate ridge contours on adjacent areas. Limited gains should be expected if minimal or no discrepancies from adjacent ridge contours are observed. Also, bone thickness and ridge concavities can be further confirmed after flap elevation and implant placement.

Radiographic Evaluation

Preoperative periapical radiographs must show optimal crestal bone levels on the dental implant site to be treated. A cross-sectional image obtained with cone-beam computed tomography (CBCT) should confirm minimal bone thickness of 1 mm on the implant site to be treated.

Surgical Procedure

The procedure is conducted as follows: After administration of local anesthesia, a crestal incision is made to the osseous crest. Full-thickness flap elevation is performed to expose the contour ridge defect; the flap must be elevated to create a pouch, where the DAS (Ossix^® Volumax, Datum Dental Ltd., datumdental.com) will be placed. The dual absorbable scaffold is folded in half and placed on the buccal aspect of the implant. The rationale for folding the material is to maximize volume and the ossifying properties of the inner layers of the material. The fold should always be on the osseous crest to maximize the tissue expansion properties of this multilayered absorbable scaffold. While folding the scaffold material is not suggested by the manufacturer, the authors know of no contraindications to folding it and have experienced good success with this technique.

Next, a healing abutment or provisional restoration is placed on the implant. Submerging the implant is not recommended because a second surgical intervention may interfere with the process of DAS replacement and ossification. Flap margins should demonstrate passive approximation, without tension, as flap tension may compress the material and reduce volume.

Suturing is done with either non-absorbable or long-lasting absorbable sutures (Glycolon^™, Osteogenics, osteogenics.com). Simple interrupted sutures should have knots placed away from the incision line. A postoperative appointment for suture removal (non-absorbable sutures) should occur at 14 days. Final restorative procedures are done after 12 weeks.

Case Presentations

Case 1

A 28-year-old female patient received a 3.6 mm x 13 mm dental implant (Astra Tech EV, Dentsply Sirona, dentsplysirona.com) to replace her missing maxillary right second premolar in a two-stage approach. A significant ridge contour defect was observed at the time of implant uncovery (Figure 1). Following local anesthesia administration via infiltration of 2% xylocaine with 1:100,000 epinephrine, a crestal incision was carried out to expose the dental implant. After full-thickness flap elevation, a thin (<2 mm) buccal plate was observed (Figure 2).

The DAS was gently hydrated in a sterile saline solution, folded, and placed on the buccal aspect of the dental implant (Figure 3 and Figure 4). The fold was placed at the level of the osseous crest to maximize the tissue expansion properties of this multilayered scaffold. A healing abutment was connected to the dental implant, and flaps were approximated without tension and secured with single interrupted non-absorbable sutures (Figure 5). A regularly scheduled postoperative appointment 2 weeks after the double-up contour augmentation procedure revealed adequate wound healing (Figure 6). The patient reported minimal to no discomfort during the initial healing period.

The patient returned at 12 weeks (Figure 7), at which time the healing abutment was replaced with a provisional restoration. Final restorative procedures were initiated 4 weeks later, when ideal ridge contours for optimal restorative treatment were observed. The patient returned 12 months after the double-up contour augmentation, and CBCT images (Figure 8, left) showed increased buccal bone thickness (3 mm) compared to what was clinically observed at the time of implant uncovery (<2 mm). Additional CBCT images obtained at 36 months showed further maturation and mineralization of DAS and stable bone thickness (Figure 8, right). Clinical images at 36 months revealed optimal tissue health and contours and soft-tissue maturation (Figure 9 and Figure 10). The implant has been in function for more than 48 months at the time of this writing.

Case 2

A 65-year-old healthy female patient received a 4.6 mm x 10.5 mm tissue-level dental implant (BioHorizons, biohorizons.com) to replace her missing mandibular right first molar. The implant was placed with an insertion torque value of 35 Ncm in a single-stage approach with the placement of a healing abutment. Preoperatively, a buccal ridge contour deficiency was observed (Figure 11). This was further confirmed at the time of implant placement when although the implant was fully surrounded by bone, the buccal bone was very thin (~1 mm) and in need of augmentation (Figure 12 and Figure 13).

The DAS was trimmed, folded, and adapted to the deficient buccal bone (Figure 14). As in case 1, the fold was placed at the level of the osseous crest. Primary closure was achieved around the healing abutment, without tension, using single-interrupted non-absorbable sutures with the DAS completely submerged under the buccal flap (Figure 15). The patient was seen for a postoperative visit 2 weeks after surgery and reported minimal to no discomfort.

After 4 months of healing (Figure 16 and Figure 17), the dental implant was deemed to be osseointegrated and was subsequently restored with a screw-retained crown by the patient's referring dentist. At 1 year, sustained contour augmentation with healthy appearance of the peri-implant soft tissues was evident (Figure 18). Periapical radiographs taken at 1 year revealed stable interproximal bone levels and increased density of bone around the dental implant (Figure 19). The implant has been in function for almost 2 years without any complications at the time of this writing.

Discussion

Tooth loss is known to lead to atrophy of the edentulous ridge.^1,2 A significant amount of bone resorption occurs in the first 6 months following tooth extraction, and this can negatively influence the remaining volume of bone available for dental implant placement.^3-5 This loss of dimension and structure can present challenges regarding optimal function and esthetic reconstruction of the residual ridge.⁶ Furthermore, the reduction in alveolar ridge height and width may prevent optimal, prosthetically driven implant placement, thereby compromising the esthetic and functional result.⁷

Implant site preservation has become the standard of care for the management of extraction sites to avoid or limit alveolar ridge atrophy following tooth extraction.^8-12 Multiple techniques and materials have been studied for their ability to enhance bone healing and bone-forming capacity in extraction sockets and have shown consistency in maintenance of alveolar ridge dimension for optimal implant placement and in preventing the need for additional bone augmentation procedures during implant placement.^13-15 Alveolar bone, however, may undergo additional remodeling after implant placement, resulting in further contraction of the buccal plate in a lingual direction.¹⁶ This additional contraction of the buccal plate in the lingual direction may adversely affect ideal bone coverage of the dental implant and/or create an unfavorable alveolar ridge contour for an otherwise esthetic restoration with natural anatomic contours. Additionally, having a buccal bone shelf width of less than 2 mm has been shown to increase the risk of peri-implant soft-tissue dehiscences and crestal bone loss, which in turn can increase the risk of peri-implant diseases.^17,18 Hence, contour ridge augmentation may be indicated at the time of uncovery of the dental implant or before final restorative procedures.

Current options for contour augmentation are to either perform an additional bone augmentation procedure if implant bone coverage has been compromised or augment soft tissue if the implant still presents with adequate bone coverage and the deficiency is limited to soft-tissue thickness. Soft-tissue contour deficiencies are treated with either autologous free gingival grafts or subepithelial connective tissue grafts, or with allograft-derived acellular dermal matrices or collagen-based soft-tissue matrices. Despite the proven efficacy of autologous soft-tissue grafting procedures, these techniques are limited by tissue availability and cause patient morbidity and additional discomfort in donor areas.¹⁹

Based on the limitations of autologous tissue use, novel mucogingival technologies such as dermal substitutes, growth factors, and other biomimetics have been considered as alternative or adjunctive treatments. The goal of the use of these technologies is to repair mucogingival tissue and restore function and esthetics in a site-appropriate manner while reducing patient morbidity. Among these material options, the ribose-based cross-linked multilayered dual soft- and hard- tissue absorbable scaffold (ie, DAS) offers such qualities as unlimited supply, stable space maintenance for development of additional soft-tissue thickness, optimal esthetic outcomes, and the unique ability to also provide an ossifying matrix for additional bone gain and thickening. Collagen is the most common component of oral tissues and is easily remodeled during wound healing. In order to prolong durability of collagen biomaterials and maximize space maintenance during wound healing after augmentation procedures, the process of cross-linking the collagen fibrils is performed.^20,21 However, toxic cross-linking agents such as glutaraldehyde can compromise the stability of the collagen matrix and interfere with the formation of new tissues.²²

A defining feature of DAS is that it is the only soft-tissue scaffold to use ribose, a natural and nontoxic sugar, to cross-link collagen fibrils in a way that mimics the naturally occurring glycation process in the human body. This results in the production of a unified matrix of cross-linked porcine collagen with optimized durability and biocompatibility for promoting natural tissue growth. This is the only collagen cross-liking technology with reported evidence of ossification.^23,24 Hence, DAS offers unique advantages for contour augmentation of implant sites. While this multilayered construct is designed to create and maintain volume for soft-tissue thickening, the inner layers that are in contact with the buccal bone plate may also create a favorable environment for migration, attachment, and subsequent proliferation of osteoblasts from adjacent areas, resulting in buccal plate thickening.

Conclusion

The double-up technique using the dual absorbable scaffold as described offers a safe, simple, predictable method for the correction of ridge contour defects with stable long-term outcomes. Future studies are needed to confirm these findings.

Disclosure

The authors have lectured for Datum Dental. Dr. Neiva has also conducted research for and received honoraria from Datum Dental and Dentsply Sirona.

About the Authors

Rodrigo Neiva, DDS, MS
Chairman and Clinical Professor, Department of Periodontics, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

Vinay Bhide, DDS, MS
Clinical Instructor and Lecturer, Department of Periodontology, Faculty of Dentistry, University of Toronto, Toronto, Canada; Adjunct Assistant Professor, Department of Periodontics, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania