Utilization of Demineralized Bone Matrix to Restore Missing Buccal Bone During Single Implant Placement: Clinical Report

Bucco-lingual width is commonly a limitation when considering implant placement. Bone and soft tissue regeneration is often indicated to provide sufficient bucco-lingual width for the placement of dental implants. Simultaneous implant placement and bone grafting can be difficult due to availability of graft materials and whether primary closure is obtainable. When considering simultaneous implant placement and buccal bone augmentation, a bucco-lingual bone width of 3 mm or more remaining is required to have sufficient bone support to provide primary stability for the implant.¹  Several techniques enable one to achieve this. For instance, a type of alveolar ridge augmentation, ridge splitting, is a viable procedure especially in the case of a long-span edentulous ridge.^2,3  However, in the case of single tooth implant when there are adjacent teeth on each side of the implant site, ridge splitting can compromise the periodontal health of the adjacent teeth.⁴  Buccal bone grafting with single implant placement will be a more effective technique.

Numerous types of grafting materials can be used to graft the buccal area of the implant. The ideal material would have properties similar to the patient's bone. Autograph, a graft from the same patient, is considered a gold standard. However, it requires a donor site surgery, which is not always available or acceptable for the patient. Without autograft, commercially available bone grafting materials including xenograft, allograft, and synthetic materials can be used. A xenograft, a graft form of another species, could, in theory, eliminate transmission of human diseases. However, concerns have been raised on the process of elimination of animal-born disease agents such as prions.^5–7  The major problem with the use of xenograft is antigenicity, as the body will recognize it as a foreign body. Many commercially available xenografts have often gone through heat treatments and or chemical processes that eliminate all organic materials and leave only inorganic materials behind. Depending on the graft preparation and treatments, xenograft materials range from scaffold osseous-like structure to glass-like materials.^5,8–10  Xenografts retain only osteoconductive properties, not osteoinductive ones. An allograft, a graft from a human donor, is biocompatible and there are little to no problems with labeling the graft as a foreign body since it is from the same species. However, some major problems with the use of allografts are worries about infectious transmission, immune response problems, and there is a need to reduce antigenicity so that the patient does not reject the graft. At the same time, allografts have a potential of maintaining human biological factors allowing both osteoconduction and osteoinduction.^11,12 

Puros demineralized bone matrix (Puros DBM) is a type of allograft that maintains osteoinductive as well as osteoconductive properties, allowing the regeneration of bone.^13,14  Puros DBM is easy to handle and contains scaffolding elements such as collagenous and noncollagenous proteins. Puros DBM is composed of 100% human DBM, active DBM (noncollagenous proteins), carrier DBM (collagenous protein matrix), cortico-cancellous bone (in some variations), and water.¹⁵  Puros DBM is made through several steps: screening, testing, and processing. First, the donor and all close-biological living relatives are screened and tested for potential hazards of infectious transmission of human immunodeficiency virus, hepatitis C virus, syphilis, and so on.¹³  The achieved bone is then ground down and demineralized into the resulting DBM powder. Stage 1 includes a 28-day rat assay¹⁴  that tests the osteoinductive potential of the DBM powder before it is mixed with the DBM carrier, sterile water, and cortico-cancellous chips. Stage 2 consists of a proprietary process to make the DBM Carrier, which allows easier handling and forming into the surgical site. Puros DBM has been shown to provide a successful delivery and containment at the surgical site.¹⁵  Here, we present the technique where we placed a single endosseous implant with simultaneous buccal bone grafting using allograft demineralized bone matrix to regenerate part of the buccal alveolar bone.

A 38-year-old Hispanic American female presented to the University of North Carolina at Chapel Hill Dental Clinic with a missing #20 since childhood. The patient was reported to be healthy and was taking no medication except for daily vitamin supplements. Clinical examination showed loss of buccal portion of residual bone and soft tissue in the area of #20 (Figure 1a).

The preoperative cone-beam computerized tomography (CBCT) scans showed the lack of buccal bone at the cervical portion of #20 site (Figure 1b and c). In silico implant planning, Simplant 15 (Dentsply, York, Pa), was used to create the 3-dimensional osseous model of the patient's maxilla and mandible. Inferior alveolar canals were located. A radiopaque denture tooth replacing #20 was used to define the position of definitive restoration (Figure 1b and c). An implant fixture, 4.1 mm × 10 mm, tapered screw vent (TSV) Zimmer implant (Zimmer Biomet, Palm Beach Garden, Fla) was chosen. The desired positioning and angulation of the implant fixture was determined. Buccal resorption of the alveolar ridge was noted. A plan for grafting at implant placement visit was made.

Treatment amoxicillin (500 mg 4 times a day for 1 week) and 0.12% chlorhexidine mouthrinse (twice a day for 2 weeks) was prescribed. The patient started using the antibiotics and mouthrinse a day before the surgery. Crestal incision was made slightly lingual on the edentulous ridge to accommodate space for an implant and graft material. A sulcular incision was made on the proximal and facial of adjacent teeth #19 and #21. A full-thickness flap was used. The implant was placed using serial drills per manufacturer's recommendation (Figure 2a through c). After the last drill was used, a bone tapping was performed to create treads for the implant fixture (Figure 2d). This bone tapping was used to ensure the angulation and position of the implant fixture.^16–18  A 4.1 mm × 10 mm taper-screwed type endosseal implant, TSV (Zimmer Biomet) was placed. The implant appeared to have good primary stability at ∼50 Ncm. However, there was approximately one-third of the implant fixture in the buccal area exposed (Fig 2e through h). After implant placement, the custom healing abutment (Fig 2i and j) was fabricated using a prefabricated provisional abutment (Temporary Abutment, Zimmer Biomet) and bis-acryl resin (Integrity, Dentsply). A straight and slightly concave emergence profile of the abutment was created. The healing abutment was placed using hand-tight pressure. Three small releasing incisions, ∼2–3 mm in length, were made at the mesiobuccal, midbuccal, and distobuccal areas of the flap to create space for graft material. Demineralized bone matrix graft material (Puros demineralized bone matrix with bone chips, Zimmer Biomet) was used to graft the buccal portion of the implant (Figure 2k). Vertical mattress sutures were used to approximate the mesiobuccal and distobuccal corners of the flap. Three single interrupted sutures were used to provide closure of the flap mesially, distally, and facially (Figure 2l and m). Postoperative instruction was given. The patient was instructed to continue antibiotics for 1 week and to continue using chlorhexidine mouthrinse for 2 weeks.

The patient came back for a 1-week, 4-week, and 3-month postoperative visit. (Figure 3a through c) At the 4-month visit, an implant fixture-level final impression was made using an impression transfer (fixture mount, Zimmer Biomet), and polyvinylsiloxane (Extrude, Kerr Dental, Orange, Calif). The custom abutment was fabricated using CAD/CAM zirconia (Atlantis, Dentsply). Lithium disilicate definitive crown was fabricated, inserted, and luted with resin cement (Rely Unicem, 3M ESPE, St Paul, Minn; Figure 3d through g). The patient came back for postinsertion visits at 2 weeks, 1 month, 6 months, 1 year, and 2 years. After 2 years of function, small volume CBCT scans were taken to evaluate the buccal bone (Fig 4a through e).

Loss of a tooth for a period of time can result in residual ridge resorption that may not be ideal for an implant placement. This case report demonstrates the use of allograft DBM and Puros DBM with bone chip, in conjunction with the placement of a taper-screwed implant. The main advantages of DBM include (1) providing a biocompatible framework for cells to grow or for osteoconduction, (2) having an intrinsic growth factors for bone and vascularization, and (3) having great handling property, or, in other words, ease of use.^14,19  Furthermore, DBM is generally radiolucent and therefore simplifies the evaluation of new bone formation, as seen in the case after 2 years after function (Figure 4d, e, and f). Our regeneration was similar to a previous study by El-Chaar who has shown bone regeneration in the case of socket preservation with Puros DBM.¹⁹  To maximize facial bone regeneration in terms of horizontal and vertical bone gain, ideally, operators would place a barrier membrane between the soft tissue and the graft material. The barrier membrane would have prevented soft tissue invagination and therefore enhanced the bone gain. The barrier membrane option was presented to the patient. However, because of the financial concern, the patient declined the option of adding a barrier membrane.

In this case, we used a custom healing abutment fabricated using a provisional abutment and bis-acryl resin.¹⁸  A custom healing abutment provides concave to straight emergence profile and close to ideal round cross-sectional contour for mandibular second premolar. More importantly, the custom abutment provides a space for the graft material without overclosure or repositioning of the flap. This allows a similar tissue contour, especially in the new free gingiva and attached gingiva, and therefore provides optimal soft tissue esthetics.²⁰  We chose to use bis-acryl resin because of its radiopacity, and because it can be seen in radiograph. Excess material can be seen and removed if needed.

Computer-aided in silico planning can be useful not only in the selection of an implant fixture, and planning of implant positioning and angulation, but also in planning for grafting volume and space needed for grafting material. We utilized the in silico planning to evaluate the amount of needed graft material as well as to design the custom healing abutment. Custom CAD/CAM fabrication of a custom healing abutment or definitive abutment also can be done with prior in silico planning.

This clinical report demonstrates a combination of the use of computer-aided implant planning, demineralized bone matrix, and a custom healing abutment in the case of a single implant with insufficient bucco-lingual bone. Optimal esthetics and functional outcomes are shown with careful treatment planning as well as surgical and prosthodontic execution.

Abbreviations

CBCT

cone beam computerized tomography

DBM

demineralized bone matrix

There was no direct compensation for this review and Zimmer Biomet has no role in the writing and publication of this manuscript. However, author SB is a Zimmer Biomet Institute lecturer. In addition, Zimmer Biomet does not directly support salary for any authors; however, Zimmer Biomet was supporting the work of author SB through unrestricted research and educational grants.

The authors thank the members of the University of North Carolina at Chapel Hill Department of Prosthodontics where clinical work was done. The work of author SB was partly supported by the National Institutes of Health (NIH) grant HL092338, and the University of North Carolina at Chapel Hill Junior Faculty Award.