Use of a decalcified cortical bone plate to aid in lateral ridge augmentation
This article is by Arun K. Garg, DMD; Gregori M. Kurtzman, DDS; Renato Rossi Jr., DMD, MSc, PhD; and Maria del Pilar Rios. DMD. MSc. PhD
Significant resorption may occur following extraction and is a common clinical problem. This may be more prominent in the anterior maxilla due to the lower density of that bone compared to the mandibular arch. How much resorption occurs relates to a multitude of factors, including the patient’s age, healing ability, medical health and reason for extraction (perio, endo, trauma or a combination of these). Additionally, bone maintenance relates to stimulation of the bone through function related to load transmission through the teeth (or implants). But, when that stimulation is removed via extraction of the teeth, the surrounding bone atrophies (resorbs). Some patients will demonstrate minimal bone loss, while others will present with significant bone loss over time.
Bone loss occurs more significantly in lower-density bone than in bone that has a higher density. As the buccal/facial bone of both arches is less dense than the lingual plate, the facial/buccal aspects will demonstrate more bone loss than the lingual/palatal aspects. The anterior maxilla (premaxilla) specifically in the area of the central and lateral incisors is more prone to bone loss following extraction. This relates to the lower density of the facial bone, typically thinner bone over the facial aspect of the teeth with possible dehiscences and fenestrations that naturally can be present as well as the concavity in the vestibule related to the trajectory of bone present.
Resorption related to extraction or even periodontal disease over a period of time necessitating extraction may leave the area insufficient to house implants that are planned to replace the missing teeth. This will require an increase in the width of the ridge in the facial-palatal dimension to provide bone volume through osseous grafting and permit implant placement. Frequently this situation will require a two-stage approach with osseous grafting being performed, allowed to heal and mature, then later placement of the implants when adequate bone volume is present to allow primary stability of the implants during their healing phase. The techniques to be described may also be used when there is sufficient ridge width crestally to place the implants but a fenestration presents at placement exposing a portion of the apical half of the implant.
A 52-year-old male patient presented missing the left central and lateral maxillary incisors with a desire to have implants to replace the missing teeth and a fixed prosthetic approach. The patient indicated that the teeth had been extracted eight years before, and clinical examination noted a deficient facial aspect of the ridge at the extraction sites and healthy soft tissue (Fig. 1). A cone-beam CT (CBCT) was taken and evaluated. Cross-sectional views of the edentulous space confirmed inadequate width of the ridge in the facial-palatal dimension to house implants at the adjacent sites (Fig. 2). The patient was informed of the clinical findings and a discussion on augmenting the site with an osseous graft would be necessary for implant placement. As insufficient bone would not permit simultaneous implant placement at the time of grafting, the patient was informed that a healing period of four to six months would be needed between graft placement before implants could be placed. This would then be followed by a four- to six-month period to allow the implants to osseointegrate before any restoration could be placed on the implants. The patient agreed to treatment and was appointed.
The patient presented for the first phase of treatment, ridge augmentation by lateral grafting. Following review, the written consent form was signed by the patient. Blood was drawn from the patients left antecubital fossa to fill four glass tubes (Becton, Dickinson and Co., Franklin Lakes, N.J.) to be utilized to prepare the most current 2018 variations of the original Platelet Rich Plasma (PRP). Two tubes were placed into a PRP centrifuge (MedEquip Dental Supplies, Jupiter, Fla.) and spun for three minutes at 3,500 rpm. The short centrifuging time does not allow the blood in the tube to fully clot, but it pre-clots the blood. While the blood was being centrifuged, local anesthetic were administered for local infiltration at the maxillary facial edentulous area and at the posterior buccal right, with addition to an IAN block in the lower right. Two tubes were placed in a separate centrifuge for 12 minutes at 1,500 rpm.
A #15 scalpel was utilized to create a vertical releasing incision between the right canine and lateral incisors and also between the left first and second premolars. These were connected by a facial sulcular incision medial to the vertical releasing incisions and a midcrestal incision at the edentulous area. A full thickness flap was elevated extending past the mucogingival junction to exposure the deficient area as well as bone covering the roots of the adjacent teeth (Fig. 3). A thin ridge with a notable concavity at the edentulous area was confirmed correlating with what was accessed on the CBCT exam. A three sided 1.2 mm bur from MedEquip Dental Supplies in a surgical handpiece was utilized to create multiple decortication points through the cortical bone to the underlying cancellous bone (Fig. 4). This is performed to allow endosteal osteoblasts from the cancellous bone to interact with the graft, grow bone around and within the particulate graft particle, and to accelerate vascularization of the graft and incorporation to the osseous bed.
Next, the donor site would be addressed. A vertical releasing incision was created with a #15 scalpel blade between the right mandibular 1st molar and 2nd premolar (Fig. 5). A buccal sulcular incision was made on the first and second molars and continued as a crestal incision in the retomolar area buccal to the crestal midline, and a full thickness flap was elevated to expose the lateral aspect of the mandibular bone (Fig. 6). A mx-grafter (Maxilon, Hollis, N.H.) was utilized to scrape the exposed bone at the external oblique ridge to harvest autogenous bone to be incorporated into the graft to be placed in the maxillary anterior. The harvested bone was placed into a sterile dish (Fig. 7). Cortico-Cancellous 100-850 micron particle size, Particulate graft material (Osteolife Biomedical) was added to the sterile dish to increase the graft’s volume. The previously centrifuged blood taken at the beginning of the appointment, had the buffy coat portion (middle layer) drawn from the tubes and placed into the sterile dish with the harvested autogenous bone and particulate graft (Fig. 8). Following stirring the mixture, it was allowed to site for 10 to 15 minutes to allow completion of the clotting phase. The PRP buffy coat contains high levels of platelets, which will act as a glue to hold the graft into a flexible mass and prevent displacement during initial healing. Additionally, the plasma has high levels of platelet-derived growth factors (PDGF-AB), transforming growth factor (TGF-beta1) and cytokines that can affect inflammation, angiogenesis, stem cell migration and cell proliferation. The flap at the donor site was repositioned and closed with 4-0 interrupted PLA resorbable sutures (Violet, Osteolife Biomedical, Jupiter, Fla.) to achieve primary closure.
A 2-mm-thick piece of Flexo-Plate Plus (Osteolife Biomedical) sized 15 by 30 mm was checked over the site to ensure adequate coverage of the defect and extension beyond its lateral borders (Fig. 9). The Flexo-Plate Plus is a bendable, partially decalcified allograft with a thickness of 0.75 to1.0 mm. The bone matrix composing the Flexo-Plate is ultimately resorbed by the body, eliminating the need for surgical removal of the matrix. This would serve to stabilize the graft to be placed into the facial defect and upon healing become the new facial cortical plate. The plate comes predrilled with holes through the plate on the left and right aspects to accommodate fixation screws. The Flexo-Plate Plus was soaked in saline to make it pliable and more easily adapted to the ridges curvature. This was adapted to the arch and fixated with a single titanium screw on the left distal to the canine and on the right distal to the right central incisor (MedEquip Dental Supplies, Jupiter, Fla.) (Fig. 10). The graft mixture of PRP, autogenous bone shavings and particulate graft had coalesced into a flexible mass in the sterile dish with the consistency of a gummy bear candy and is referred to as “gummy bone” (Fig. 11). This was carried intraorally and packed between the fenestrated facial plate and the stabilized Flexo-Plate to create what would be the new ridge width dimensions when healing had completed (Fig. 12). The graft and Flexo-Plate were covered with a PRP membrane (also referred to by some authors as PRF), which would act as a short-term barrier to prevent soft tissue ingrowth and a source of growth factors while the graft was healing and maturing (Fig. 13). The flap is reapproximated in a tension-free manner, and the margins are fixated with 5-0 Polypropylene sutures in an interrupted pattern (Fig. 14). Post-op instructions were given, and a booklet with instructions was provided to the patient. These instructions included directions to apply the ice bag over the affected area 20 minutes on and 20 minutes off for two to four hours, to help prevent the development of excessive swelling and discomfort; avoid hot liquids and foods during the first 24 hours following surgery and then warm salt water rinses four to five times daily for the next week. The patient was prescribed 24 tabs of Vicodin (5mg hydrocodone bitartrate /30mg acetaminophen) and instructed to take one tablet every six hours for pain. A prescription for a Medrol Dose Pack was also given, and the patient was instructed to take as the pack recommended.
The patient returned after two weeks for suture removal and site healing evaluation. Both the donor and recipient site flaps remained approximated. No gap was noted at the incisions, and healing was progressing with an absence of inflammation. The patient reported he was comfortable and was instructed to continue with warm saltwater rinses for another week to aid in additional soft tissue healing.
At 4.5 months post surgery the patient returned, and the soft tissue over and adjacent to the site demonstrated an absence of inflammation and appeared healthy with palpation of the grafted site feeling dense to the touch (Figs. 15a,b). A CBCT was taken to evaluate graft maturation and alterations to the ridge width as a result of grafting. A CBCT cross-section of the graft revealed incorporation of the graft and dimensional changes to the ridge width that would now allow implant placement (Fig. 16). Local anesthetic (2 percent lidocaine with 1:100,000 epinephrine) was administered to the site via infiltration and a full thickness flap was elevated. The graft was not discernable from the adjacent non-grafted bone and appeared dense to instrument touch and the defect was filled resulting in adequate width for implant placement (Fig. 17). Osteotomies were created to accommodate a 3.7 mm x 13 mm implant (ImplantVision, West Palm Beach, Fla.) at the left central site and a 3.2-by-13-mm implant at the left lateral site and implants were placed and cover screws attached (Fig. 18). The site was closed with 5-0 Polypropylene sutures in an interrupted pattern and the patient dismissed. Restoration of the implants would occur following a three- to five-month integration period. A CBCT taken following implant placement demonstrates adequate thickness of the facial bone at the implant to house the implant and allow long-term stability (Fig. 19).
A frequent occurrence of loss of teeth in the anterior maxilla is loss of the facial plate creating osseous dimensions that will not accommodate implant placement. Resorption of the facial plate may present at time of extraction when the tooth has undergone endodontic, periodontic or structural (vertical root fracture) changes. This is often complicated by natural dehiscences and fenestrations found on healthy teeth that worsen when pathology arises.
Reconstruction of the deficient premaxilla has been proposed with multiple treatment options. These have included the use of cortical blocks retrieved from another site (ramus, illiac crest) and fixated with screws during healing. Titanium mesh has been proposed to cage graft material allowing the ridge to be rebuilt. Ridge splitting has been another treatment advocated to create a ridge that could accommodate implant placement. These approaches have negatives to their use. Cortical blocks require a donor site that increases morbidity and decreases patient comfort during the healing phase. Additionally, should the block not integrate with the recipient bed, separation may result either at time of implant placement or when under restorative function. Some healing resorption has been reported and overbuilding the site may be considered to accommodate that loss of volume during healing. Utilization of titanium mesh requires a second surgery to remove the metal mesh and screws, which is performed when implants are ready to be placed into the healed site. But the main reported complication to use is premature exposure of the mesh. This may necessitate early removal of the mesh decreasing the quality and quantity of bone resulting from the graft that was caged by the mesh. Implant success in areas utilizing titanium mesh to contain grafting does show a high success rate even with the complications typically encountered during the healing phase.
Ridge splitting has been advocated to treat the narrow ridge, but a minimum width of ridge is needed to be able to affectively split it. Resorption occurs in the vertical dimension at the expense of the less dense facial plate. When splitting the ridge, due to the density of the palatal bone expansion occurs in the facial direction. If the ridge has lost significant facial osseous structure, expansion can’t be achieved. Minor complications have been reported to ridge splitting when adequate initial ridge width was present that included wound dehiscence and fracture of the facial plate due to a bad split. But complications were at an equal incidence to block grafted sites.
The technique illustrated in the case presented here is an alternative method that eliminates the need for cortical bone from a donor site and decreases the complications reported with use of titanium mesh to contain the graft. Additionally, width of the residual ridge does not determine if this technique may be used as limits ridge splitting. As cortical fragments are taken from the patient with the bone scrapper and mixed with PRP derived from the patient’s own blood, potential for foreign body reactions is minimized. Stem cells from the patient are able to “kick start” the healing and conversion to bone that has high enough quality to accommodate implant placement after graft healing. Ideally implants should be placed into medullary bone in contact with the majority of its surface as this bone is dynamic and active. Cortical bone is denser but lacks osteoblasts and other bone maintaining cells, which may demonstrate radiographic dense bone on contact with the implant but not be able to respond to changes related to function on the implant as well. Utilization of the flexible bone plate (Flexo-plate plus) from the supplier, eliminates the need for titanium mesh to contain the graft and like a cortical block becomes part of the healed graft. The added benefit of this technique over cortical blocks is the resulting bone for implant placement has a medullary quality and implant placement into it has active bone progenator cells in contact with the implant’s surface. Risk of exposure of the bone plate, unlike titanium mesh, is eliminated, as the body does not identify the bone plate as foreign. The overlaying PRP membranes stimulate soft tissue healing and the stem cells within penetrate into the bone plate, using it as a scaffold to convert it to host bone over time. The gummy bone being sandwiched between the Flexo-plate plus and recipient bed has the added advantage over particulates that it is moldable and does not displace out of the site like is often observed with particulates.
Reconstruction of the atrophic maxilla to accommodate implant placement can be challenging related to deficiencies in bone volume to accommodate the implant. Various techniques have been reported to rebuild the deficient area. The technique described here eliminates some of the potential complications associated with other reported techniques and provides high quality bone that is suitable for implant placement.
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