August 6, 2019
by Arun K. Garg, DMD; Gregori M. Kurtzman, DDS
Challenges to implant placement in the posterior maxilla may be related to the maxillary sinus. The sinus may pneumatize (enlarge) related to sinus issues, patient age, how long the site has been edentulous or related to periodontal bone loss associated with the tooth that will or has been extracted.1> Hence, crestal bone height may be diminished superiorly related to enlargement of the sinus, inferiorly related to periodontal bone loss or a combination of these two processes. Thus, implant placement is complicated due to insufficiently available bone to house an implant. Short implants have been advocated for these clinical situations but sufficient height may not be present to even place these short implants or may not be the approach desired due to load issues when the planned prosthetics is completed.
Two approaches to increase crestal bone height have been reported in the literature. The lateral sinus augmentation pioneered by Hilt Tatum in 1974, was first reported in 1980 by Boyne.2 A complex technique required surgical skill with utilization being applied to any crestal remaining height from paper thin to varying residual thicknesses. The other technique, first reported in 1994 by Summers, used a crestal approach to simplify the surgical aspect of elevating the sinus. This could be used when there was sufficient height to stabilize the implant at placement, but additional height was needed to encompass the implant within bone3
The crestal approach, requires sufficient bone height to stabilize the implant as the implant is required in this technique to tent up the sinus membrane and allow the graft to mature into host bone encompassing the entire implant. It has been suggested a minimum height of 4 mm is required to achieve that goal.4,5
There is some consensus that a 4 mm increase in height can be achieved with the crestal approach.6,7 Yet, other authors stating that greater height increases are possible to an achievable 10 mm gain.8 When less available initial crestal height presents, a lateral sinus augmentation should be considered a more predictable approach. The crestal approach works well in single or two adjacent sites, but may not be suitable when more than two adjacent implants are planned that require a height increase in bone at each site. The crestal sinus augmentation approach has demonstrated clinical success of over 93% as has been reported.9 Typically, when multiple adjacent sites are being sinus grafted they will require graft placement medial to where the implants are positioned. This will require elevation of the sinus membrane medially which can not be performed through the crestal osteotomy.
The crestal sinus approach can be performed in an edentulous healed site or at the time of extraction when implant stability can be achieved simultaneous with sinus augmentation. The treatment planning begins with determination of residual ridge height between crest and sinus floor radiographically. A measurement is taken with an instrument on the radiographic film or with software when a digital radiograph has been taken. The resulting height will determine how deep the initial (pilot) drill will be taken to avoid potentially tearing the sinus membrane. The authors recommend that 2 mm be deducted from the determined height to avoid potential contact of the tip of the pilot drill with the sinus membrane. If for example, the height measures 7 mm, that depth for the pilot drill be set at 5 mm. Traditional osteotomy burs are not suited for sinus elevation procedures as the tip of the drill, although well suited for bone cutting will tear the sinus membrane when it contacts it. Thus, safe ended osteotomy drills are required that will bump up the membrane (elevate it) when contacting the delicate structure during site preparation. These sinus drills although safer than traditional drills, should be limited in how high they are taken past the sinus floor to avoid creating tension in the sinus membrane and subsequent tearing with further advancement. Thus, a physical stop on the drill ensures that accidental advancement is not possible due to free-handing drill depth.
Sinus Crestal Approach Kit
The Sinus Crestal Approach kit (ImplantVision, Miami, FL) contains all the tools required for a crestal sinus elevation from site preparation to graft placement into the elevated sinus prior to implant insertion (Fig. 1). Having all the necessary tools in a single kit allows the practitioner to improve surgical treatment efficiency and have the items easier to access during treatment.
An edentulous site to be treated, the initial osteotomy is made with a pilot drill (guide drill, Fig. 2 left) resulting in a 2 mm osteotomy. As recommended previously depth should be 2mm shy of the measured sinus floor. Depth stoppers can be used on the guide drill to improve depth accuracy. When a thin ridge is present and a starter is desired to prevent jumping of the guide drill with the crest, a diamond reamer may be used. These diamond reamers are a ball diamond available in three diameters (Fig. 2 right). If crestal sinus elevation is to be performed at an immediate extraction site, following tooth extraction the socket is cleaned of residual soft tissue with the diamond reamers. This eliminates any soft tissue that may hamper osseous contact with the implant surface. These diamond reamers may also be used for osteotomy preparation. The diamond reamers are run in the surgical handpiece at 800-1,200 rpm.
Following initial site preparation, the site diameter is enlarged to less than the diameter of the implant planned for the site. This will allow the implant to exert some osseocompression upon placement and improve initial stability especially in the less dense bone of the posterior maxilla. To achieve this SD reamers are utilized (Fig. 3 left). These drills have a safe tip designed to elevate the sinus upon contact with it and avoid tearing the delicate membrane (Fig. 3 right). Length stoppers are provided in the kit and their designation indicates the depth the drill may enter the bone before the stopper prevents further advancement (Fig. 4). These start at 3 mm and increase in 1 mm increments to a maximum of 12 mm. The stoppers may also be used on the guide drill and hand instruments to guide depth when they are used. The SD reamer drill with stopper may also be used to verify osteotomy depth in relation to the sinus floor by placement off the handpiece into the site and a radiograph taken.
Several hand instruments are provided in the kit. A depth gauge instrument with millimeter markings allows verification of the osteotomy depth and can be used for measurements of film radiographs to determine crestal height present (Fig. 5A). These include a sensor gauge that is used to explore the apical depth of the osteotomy for contact with the sinus membrane (Fig. 5B). The tip of the sensor gauge is domed to prevent inadvertent puncture of the sinus membrane when exploring the osteotomy. Stoppers may be used on the sensor gauge to increase gauging accuracy when desired. A double ended bone packer with a 1 mm end and a 2.2 mm end that will accommodate the stoppers allows the practitioner to push the graft material apically into the elevated sinus area (Fig. 5C). A bone syringe with a 2.5 mm barrel diameter aids in placement of graft material into the void created by elevation of the sinus membrane (Fig. 5D). It is important that sufficient graft is placed into the sinus void under the elevated membrane to ensure that the placement implant upon healing has its apical portion surrounded by bone.
A 48-year-old male presented with a missing right maxillary molar and a desire to replace the missing tooth of several years with an implant. The buccal aspect of the ridge presented with a slight concavity due to resorption during healing after the molar had been extracted (Fig. 6). A radiograph was taken and it was determined that with sinus pneumatization additional height would be needed for implant placement (Fig. 7). As 5 mm of crestal height was present and initial implant stability would allow a simultaneous crestal sinus lift with implant placement. The patient was scheduled for a crestal sinus augmentation, augmentation of the buccal ridge and implant placement.
Local anesthetic was administered and an incision was placed in the buccal sulcus of the 2nd molar and continued forward as a crestal incision across the edentulous site (Fig. 8). A full thickness flap envelop flap was elevated to exposing the ridge crest (Fig. 9). A 3 mm stopper was placed on the guide drill and the initial pilot hole was created at the center of the edentulous site matching the long axis of the adjacent teeth. A SD reamer of 3.7 mm diameter with a 4mm stopper was used to increase the osteotomy diameter (Fig. 10). The sensor gauge was used to verify that the sinus membrane had been exposed and the membrane was intact, exploring the apical aspect of the osteotomy. The osteotomy was continued with increasing stoppers and finalized with the 11 mm stopper to complete elevation of the exposed sinus membrane (Fig. 11). The sensor gauge again was used to verify the membrane was intact.
Various augmentation materials may be used in both crestal and lateral sinus augmentation procedures. Autologous blood concentrates such as PRP have been reported in the literature as improving graft organization and bone development compared to use of osseous graft materials alone.10-12 The authors have found that mixing the L-PRP (liquid PRP) in with the graft material coalesces the graft into a easier to handle pliable mass. For this case a PRP fibrin clot was used as the sole grafting material. Additionally, the fibroblasts, platelets, cytokines and stem cells improve graft organization and maturation during healing.13-15
Blood was collected from the patient at the start of the surgical appointment and centrifuged. A PRP fibrin clot was removed from the tube (Fig. 12) and transferred to a sterile dish. The liquid portion of the plasma (yellow) was withdrawn from the tube with a syringe (Fig. 13) and added to the cortical cancellous osseous graft material (Osteolife, Miami, FL) in a separate sterile dish and allowed to site during osteotomy preparation. Following osteotomy completion and sinus elevation, the PRP osseous graft mixture was introduced into the osteotomy with the bone packer instrument with the 7 mm stopper on it (Fig. 14). The bone packer was used to compress the graft into the elevated sinus spreading the material laterally as it was pushed superiorly.
An implant (ImplantVision) 4.2 mm x 11.5 mm was placed into the osteotomy using the surgical handpiece (Fig. 15). The implant was placed to be flush with the crest (Fig. 16). The previously created PRP fibrin clot was placed on the buccal aspect of the ridge to bulk out the contour deficiency and create a better blend with the buccal aspect of the adjacent teeth. The flap was repositioned to achieve primary closure over the implant and PRP fibrin clot and secured with sutures (Fig. 17). A Periapical radiograph was taken to document the implant position, depth and relation of the apical portion of the implant and elevated sinus graft around it (Fig. 18).
When sufficient crestal height is present to stabilize the implant but additional crestal height is required crestal sinus augmentation will permit simultaneous sinus augmentation and implant placement at the same surgical appointment. This approach has less post operative issues than lateral sinus augmentation procedures and a simpler surgical procedure. The crestal sinus augmentation kit and technique detailed improves clinical outcome with a decrease in membrane tearing. Practitioners routinely placing single or two adjacent implants in the posterior maxilla should be prepared for the need for increasing crestal bone height through a crestal sinus approach.
About the Author
Dr. Garg is an internationally recognized dental educator and surgeon, who for more that 20 years served as a full-time professor of surgery in the department of Oral and Maxillofacial Surgery and as director of residency training at the University of Miami Leonard M. Miller School of Medicine. He can be reached at firstname.lastname@example.org.
Dr. Kurtzman is in private general dental practice in Silver Spring, Maryland, USA and a former Assistant Clinical Professor at University of Maryland in the department of Restorative Dentistry and Endodontics and a former AAID Implant Maxi-Course assistant program director at Howard University College of Dentistry. He has earned Fellowship in the AGD, American College of Dentists (ACD), International Congress of Oral Implantology (ICOI), Pierre Fauchard, ADI, Mastership in the AGD and ICOI and Diplomat status in the ICOI, American Dental Implant Association (ADIA), International Dental Implant Association (IDIA). He can be reached at email@example.com.