Socket Preservation and Sinus Augmentation Using a Medical Grade Calcium Sulfate Hemihydrate and Mineralized Irradiated Cancellous Bone Allograft Composite

It is necessary to have a suitable amount of alveolar bone volume for proper functional aesthetic dental implant placement. Increasing this volume in the edentulous posterior maxilla or immediately after the extraction of a tooth is orchestrated by the careful preservation and stimulation of the wound healing and bone regeneration process. This process can be affected by infection,¹  difficulty during tooth extraction,^2–4  patient age,^3,5  and heavy tobacco use.⁶  The goal is to obtain a ridge with adequate bone volume and minimal postoperative pain at the time of implant placement.

To enhance the bone healing process, surgical treatments and bone regeneration techniques, such as guided bone regeneration (GBR) and sinus augmentation, have been studied. GBR and sinus augmentation focus on regenerating and increasing the amount of hard and soft tissue in a defective site by using a graft material. The graft material enhances bone growth by functioning as a 3-dimensional matrix that facilitates and guides bone repair.^7,8  Because epithelial cells migrate approximately 15 times faster than bone cells, a membrane barrier can be used in conjunction with a bone graft to isolate the surgical site from the oral cavity.⁷  The barrier also maintains the graft and blood clot in place and excludes soft tissue, such as epithelium and gingival corium.^7,9  A nonresorbable synthetic barrier membrane, such as dense polytetrafluoroethylene (dPTFE), has been studied in numerous reports.^10–14  Immediately after a tooth extraction, a blood clot forms within the socket. After a few days, this blood clot contracts and is replaced by granulation tissue proceeded by an increase in fibroblasts. Within a week, osteoclasts then induce bone resorption, and the first signs of remodeling are seen with a vascular network and osteoid. A trabecular pattern then begins to form, and even after 2 months bone formation is incomplete and undergoing remodeling.^4,15–17 

The presence of the buccal plate enhances the overall healing process by containing the graft and providing an area for blood supply. It was thought that bone forms in the socket if the blood clot is stabilized by a membrane barrier and a bone graft was not important for bone formation. However, there are several reports of bone loss, ridge collapse, and insufficient bone to allow for the placement of a dental implant without the use of a bone graft in the extraction socket.^18,19 

A study by Iasella et al¹⁹  showed that when using a bone graft with a collagen membrane for ridge preservation, ridge height and width improved compared with using extraction alone. They showed that the bone width from the ridge preservation group decreased by only 1.2 mm, whereas the width from the control group (extraction alone) decreased by 2.7 mm, more than double the value. The dimensions proved to be more acceptable for the placement of a dental implant, especially in areas where ridge height would affect the esthetic results.

A sinus augmentation predictably increases bone height in the posterior maxilla; an approximate vertical bone height of 10 mm is recommended to support the implant.²⁰  If this distance is <5 mm, it can potentially compromises the success of the implant. Alveolar ridge resorption also can lead to long abutments and crowns, compromising the esthetics of the implant. During the procedure, the sinus is approached either through the lateral wall or subantrally, and a bone graft is placed on the sinus floor.^21–30  The placement of the implant can be immediate,³⁰  delayed,²³  or staged.²¹ 

Various bone graft materials have been studied: autografts, xenografts, demineralized freeze dried bone allograft, mineralized cancellous bone allograft (MICBA), and medical grade calcium sulfate hemihydrate (MGCSH).^{2,15,16,31–38}  Although autografts have osteoinductive and osteoconductive properties, they are only available in limited quantities and have been known to cause harvest site morbidity. Xenografts can cause a host immune response and may be slow to degrade, as seen with certain bovine dental bone grafts.³⁹  MICBAs have the ability to retain 3-dimensional structure, organic matrix, and collagen content.⁴⁰  MICBAs have been used successfully in numerous studies, including GBR,^41,42  sinus augmentation,^21,25,30  and socket augmentation,^43–45 ; however, it is difficult to hold this type of particle-based graft in place without the help of a binder.

MGCSH is a bone graft binder material that has been used for >110 years.⁴⁶  It is completely bioabsorbable⁴⁷  and osteoconductive,⁴⁸  and it stimulates the formation of blood vessels⁴⁹  and does not cause an inflammatory response.³¹  As a binder, MGCSH can be used in combination with any type of particle-based bone graft material to improve handling characteristics, enhance graft particle containment, and increase bone formation; significantly more bone formed in defects grafted with a combination of allograft and calcium sulfate vs allograft alone.^50–52 

When MGCSH degrades, it causes a temporary local drop in pH, resulting in the demineralization of the surface layer of existing bone. This demineralization causes the expression of bioactive molecules and the release of growth factors such as fibroblast growth factors, transforming growth factors, and bone morphogenetic proteins.^37,53  The formation of calcium phosphate, and increase in angiogenesis, and the release of growth factors stimulate the growth of bone in defects filled with MGCSH.

In this case series, MICBA (Rocky Mountain Tissue Bank, Aurora, Colo) was mixed with MGCSH (DentoGen, Orthogen, LLC, Springfield, NJ) for the regeneration of bone in the socket and sinus after tooth extraction. A nonresorbable dPTFE membrane barrier (Cytoplast, Osteogenics Biomedical Inc, Lubbock, Tex) was used to stabilize the graft materials and to prevent soft tissue ingrowth into the socket and sinus cavity.

A 77-year-old woman presented with a complaint of a loose maxillary bridge on teeth #3–5. She takes medication to regulate her blood pressure and early stage Alzheimers. She has mild dry mouth that is secondary to the antihypertensive medications. According to the clinician's knowledge, none of these medications affect the normal wound healing process. The patient's dental history and clinical and radiographic examinations revealed that dental implants were placed and restored in tooth #6 approximately 2 years earlier (Figure 1a and b). Tooth #5 was attached to the dental implant restoration of tooth #6 by use of an acid-etched bridge wing. Contact was debonded from the bridge by erosion. The cement had washed out over time due to recurrent decay. There was an existing bridge that exhibited gingival recession. As the recession allowed the root to be exposed below the margin of the existing bridge, it was more prone to recurrent decay. The patient complained of a constant dull ache in that area. Using a plastic-tipped forceps bridge, 3-4p-5 was easily removed to reveal that teeth #3 and #5 had 3+ severe mobility (Figure 2a). Severe mobility is described as having >1 mm of displacement in a facial-lingual direction combined with vertical displacement. Before surgery, the entire mouth was scaled and root planed using local anesthesia, 4% articaine with 1:200 000 epinephrine (Septodent, Lancaster, Pa). A sulcular incision was then made using a #15 blade, and a full thickness mucoperiosteal flap was reflected. Luxators and elevators were then used. A maxillary extraction forceps was used to remove the tooth and root. The wound was curetted using a Lucas curette. Tooth #3 required sectioning of the roots before removal, and a cystic structure was removed in pieces attached to the tooth at the apex (Figure 2b). Tooth #5 also had an apical cystic structure removed. Cysts were not sent for biopsy and were consistent with clinical presentation of a dental cyst of periapical origin.

Socket defects #3 and #5 were debrided of all granulation tissue. MGCSH was mixed with MICBA at a ratio of 1:1 to form the bone graft composite. The composite bone matrix was grafted into the socket defects using a spatula (Figure 3a). The defects were loosely packed with composite bone graft mix and closed with a dPTFE membrane barrier (Cytoplast, Osteogenics Biomedical) using nonresorbable sutures to reposition the full thickness mucoperiosteal flap (Figure 3b). The periodontal therapy instituted to prevent contamination of the implant and graft sites was by oral hygiene instruction. The patient was given a script of Peridex 0.12% solution and rinsed with a capful 3 times a day for 2 weeks. The preoperative periapical digital radiographs of the socket defect were compared with those of the postoperative periapical digital radiographs of the grafted site immediately after surgery (Figure 4a) and at 6 months (Figure 4b). Periodontal pocket charting also was done. After 1 month, the dPTFE membrane barrier was removed by first irrigating the area with Peridex 0.12%. The sutures and membranes were then removed. The graft site was completely covered with a keratinized soft tissue seal and was observed to be healing well. At the 4-month postoperative time point, examination revealed keratinized soft tissue (Figure 5). Probing of the surgical site revealed that the bone had the feel of a thin cortical plate surrounding a dense trabecular area. Radiograph inspection at 6 months after socket grafting showed bone density comparable with that of the surrounding bone, an indication of bone regeneration at the grafted site (Figure 6). At this time, radiographic measurements using a 5-mm radiographic marking ball (Salvin Dental Supplies, Charlotte, NC) were made between the floor of the sinus and the crest of the ridge were made. It was evident that more bone height was needed to accommodate the implants; therefore, a subantral sinus lift was performed at the same time with the placement of the implant.

An osteotomy was made using the standard osteotome technique, exposing the floor of the sinus.⁵⁴  CollaCote (Zimmer Dental, Carlsbad, Calif) was placed in the superior portion of the osteotomy. A convex osteotome (Nobel Biocare USA, LLC, Yorba Linda, Calif) was introduced into the sinus, lifting the membrane to accommodate the apical portion of the implant. A 1:1 ratio of MGCSH:MICBA was mixed with saline and gently placed in the osteotomy in increments before the MGCSH could set. To monitor the progression of the lift, radiographs were taken at every third increment. Each graft increment introduced into the osteotomy was approximately 1 mm high. This approach ensures that the bone composite graft did not tear the sinus membrane. Anterior and posterior guide pins were put into place to ensure the correct parallel position of the future implants. The crest module of the implant was placed at the level of the crest of bone. The soft tissue was approximately 3 mm and compensates for any retraction of the bone from the crest module of the implant. Socket defect #3 received a NobelReplace Select Tapered Groovy 5.0 × 8-mm implant (Nobel Biocare USA). Socket defect #5 received a NobelReplace Select Tapered Groovy 4.3 × 10-mm implant (Nobel Biocare USA). Both implants were introduced at the same time as the sinus augmentation procedure at a torque of 35 N/cm using a Nobelbiocare hand torque driver. The soft tissue was repositioned with nonresorbable sutures (Cytoplast USP 4-0 PTFE, Osteogenics Biomedical), and a 4-month healing period was allowed until prosthetic restoration was achieved. The final restoration was a NobelProcera zirconia substrate (Nobel Biocare USA) with porcelain overlay 3 unit cemented fixed bridge.

A 63-year-old male patient presented in good health with a complaint of bad breath and gums that were constantly bleeding. Clinical evaluation revealed extensive calculus buildup and crowding of the lower anterior teeth, which attributed to bad breath. Plaque was moderate and generalized with severe focal bone loss (Figure 7a). The patient wanted to maintain as many of his natural teeth as possible; therefore, it was decided that teeth #22 and #27 would undergo periodontal scaling and root planing to save them. Teeth #23–26 were extracted (Figure 7b) as explained in case report 1. MGCSH and MICBA were mixed at a ratio of 1:1 and placed in the multiple-socket defect (Figure 8a and b). The defects were closed with a dPTFE membrane barrier (Cytoplast, Osteogenics Biomedical) using nonresorbable sutures (Cytoplast USP 4-0 PTFE, Osteogenics Biomedical; Figure 9a). A lingual pouch of 2 mm was created to retain the membrane.

After graft placement, examination revealed normal-healing soft tissue at the 3-day, 4-week, and 3-month time points (Figure 9b–d). Periodontal pocket charting was implemented, and periodontal therapy, instituted to prevent contamination of the implant and graft site, was done and reviewed as described in case report 1. Membrane and sutures were removed, as described previously, at the 1-month time point. Teeth #22 and #27 regained their stability. A medical grade computerized tomography (CT) scan (Millburn Medical Imaging, Maplewood, NJ) was performed after 6 months, and it revealed substantial bone growth within the socket defect. Regeneration of bone was observed qualitatively, based on the feel of the bone while performing the osteotomy. Regeneration also was analyzed using a medical CT scan with NobelGuide software (Nobel Biocare USA; Figure 10a–d). During CT scan, the area of measurement was 2 mm in diameter, and after taking 20 sample sites, the averaged Hounsfield unit for tooth #24, #25, and #26 was 641, 712, and 835, respectively.

The quality and quantity of bone in a socket defect are essential for the placement of a dental implant. Bone grafts used with a membrane barrier have been shown to enhance the regeneration of bone and kerantized soft tissue.⁷  In these case studies, MGCSH was mixed with MICBA (1:1) to form a bone graft composite. MGCSH acts as a bone graft and bone-graft enhancer to MICBA.^32,51,55,56  It stimulates the formation of blood vessels,⁴⁹  prevents the ingrowth of soft tissues,⁷  and thereby promotes bone formation. As the MGCSH dissolves, it causes a local increase in Ca⁺ ions that combines with phosphate ions to form calcium phosphate. Local acidity is increased, leading to surface demineralization of the surrounding bone. This demineralization causes the release of growth factors that further stimulate bone formation.^37,49  As MGCSH dissolves, the surface of MICBA is exposed, leading to bone conduction and formation. The two cases in this report are an accurate representation of >60 cases performed by the same clinician. Based on his clinical expertise, CT scans, and radiographs, a similar volume of bone was seen for all cases. An MGCSH:MICBA osteoconductive bone graft composite was successfully used in all cases for maintaining the existing alveolar socket space, increasing the amount of bone volume in the sinus, or both. The composite graft stimulated bone formation in the extraction sockets by preventing the ingrowth of soft tissue and migration of MICBA out of the socket defect. At the 3-month time point, the bone crest resorption did not exceed the first thread of the implants. There was no reported gingival recession or inflammatory response. Based on periapical radiographs, CT analyses, or a combination, extraction sockets had completely healed, and the patients showed no clinical signs of pain or discomfort. Previous researchers used pure MICBA to promote bone formation in both periodontal defects and extraction sockets.^{42,43,45,57,58}  In a case study by Wang et al⁴⁵  a mineralized bone plug was shown to be a “suitable and predictable technique for socket augmentation.” It promoted the regeneration of bone and preservation of the alveolar ridge; at 5–6 months, bone completely filled the socket. The case study by Minichetti et al⁴³  found similar results at 5 months, with normal bone replacement with no foreign body reaction. Histological and clinical analysis demonstrated the formation or remodeling of bone, making it possible for the placement of an implant. Block et al⁵⁷  found that 24 months after implants were restored, bone levels were stable.

Vance et al⁵²  used graft material with and without MGCSH and showed that socket ridge width and height dimensions were preserved with significantly more vital bone when using graft material with MGCSH. As similar trend was seen during a sinus augmentation study by Dellavia et al,²⁴  where they showed an average bone height increase of 260% by 3 months when using a composite of MGCSH and demineralized freeze-dried bone allograft in a delayed sinus lift. Thor et al⁵⁹  showed that when a graft material was not used during a sinus lift, there was just an average increase of 180% in bone height, even after 6 months. Both studies used 11-mm-long dental implants. It also was shown that a pretreatment bone height of ≥5 mm had a survival rate of 96%, whereas a pretreatment bone height of ≤4 mm had a survival rate of 86%.⁶⁰  MGCSH increased the ease of handling by creating a paste of the bone graft material. This paste made it easier to clinically manipulate the material into the extraction socket, as well as keep the graft particle in place. Similar results were seen by other researchers who used MGCSH in combination with other bone graft materials. The combination improved handling characteristics, prevented ridge collapse, and enhanced the quality and quantity of bone formation in periodontal defects and extraction sockets.^19,50–52 

In this surgical case series, MGCSH mixed with MICBA was shown to be an effective bone graft composite. Judging from the periapical radiography and CT scans, the composite graft assisted bone formation and remodeling in the extraction socket, promoting osteointegration of the implants. MGCSH, a cost-effective option, successfully improved MICBA handling characteristics, prevented soft tissue ingrowth, and assisted in the regeneration of bone.

CT

computerized tomography

dPTFE

dense polytetrafluoroethylene

GBR

guided bone regeneration

MGCSH

medical grade calcium sulfate hemihydrate

MICBA

mineralized irradiated cancellous bone allograft