A Simplified Approach to Implant Placement
A case in the posterior maxilla with crestal sinus augmentation.
By Gregori M. Kurtzman, DDS; Douglas F. Dompkowski, DDS
Implant placement in the posterior maxilla often creates a challenge resulting from inadequate bone height because of close proximity to the sinus. After tooth loss in the posterior maxilla, the maxillary sinus enlarges over time and can make of implant placement more complex when combined with crestal resorption. It is not uncommon to have the sinus invaginate around the roots of molars and, less frequently, the premolars prior to extraction. Maxillary sinus augmentation becomes necessary to provide adequate bone height volume to place implant fixtures.
First reported by Boyne in 1980,1 maxillary sinus augmentation with various bone graft materials has become routine over the past 15 years. Various studies have reported highly successful implant survival rates when placed into an augmented sinus.2-4 Transalveolar sinus floor elevation or subantrial augmentation, first described by Tatum5 and later modified by Summers,6-8 uses a series of osteotomes with a mallet to create an osteotomy and fracture the sinus floor while simultaneously elevating the Schneiderian membrane. Once manipulated, the membrane is lifted and the sinus is augmented using a series of bone graft materials to create greater height and expand the bone volume available for implant placement.
Various studies report that when 5 mm of residual alveolar bone is present, simultaneous implant placement can be performed and achieve adequate primary stability.7,9-10 However, when there is less than 5 mm of residual alveolar bone height, a delayed 2-stage approach has been recommended.11-12 The most common intraoperative complication of sinus elevation is the tearing of the Schneiderian membrane, which could allow for bacterial contamination of the graft or dispersion of the graft into the sinus cavity. In this article, a crestal-approach sinus augmentation procedure will be highlighted using safe side/end-cutting drills with vertical stoppers combined with hydraulic pressure for membrane elevation using the Crestal Approach Sinus Kit (CAS-KIT) from Hiossen (www.hiossen.com).
Internal Sinus Lift Technique
The CAS-KIT consists of a set of safe end drills, metal stoppers, depth gauge, hydraulic lifter, bone graft carrier, condenser, and bone spreader.
Initiation of the procedure is with a 2-mm twist drill with a stopper set for the desired osteotomy length, stopping 1 mm to 2 mm inferior to the sinus floor. Osteotomy preparation continues using the CAS-Drill diameters of 2.8 mm through 4.1mm, at 400 to 800 rpm, using the metal stopper on each drill. The slower drill speed diminishes possible tearing of the membrane when the end of the drill contacts the tissue, and allows better tactile feel to the surgeon. The length of preparation can be altered at this point to gently enter the sinus cavity, pushing up a conical bone chip at the center of the safe end drill.
A drill stop is selected and placed in the CAS-Drill as the site is prepared to the depth of the available bone inferior to the maxillary sinus (Figure 1). The drill stop is transferred to subsequent CAS-Drills as the diameter of the site is enlarged. Autogenous bone is harvested from the drill, which is designed to collect bone during the drilling process and is mixed with the graft material to seed it with osteoblastic cells and other progenitors of bone (Figure 2). Next, a combined depth gauge/sinus probe is used to check the depth of the osteotomy and begin sinus membrane elevation. The apical end of the instrument is convex and wider then the shaft of the instrument to decrease accidental puncture of the membrane. The hydraulic lifter provided in the kit is used to introduce 1 cc of sterile saline into the sinus cavity, lifting the membrane with hydraulic pressure (Figure 3). A carrier is used to place the graft material into the osteotomy (Figure 4). Bone graft material is then packed into the osteotomy and is pushed into the sinus with a bone condenser that also has the metal stopper attached to prevent forcing the graft through the elevated membrane (Figure 5 and Figure 6). A rotary bone spreader with a stop is introduced into the site and at 20 to 30 rpm is used to evenly distribute the bone, further elevating the sinus (Figure 7). After the desired augmentation height is achieved, the implant is placed (Figure 8, Figure 9, Figure 10 and Figure 11).
A 64-year-old man presented with dislodgement of the crown on tooth No. 13 and a fracture below the gingival margin to the crestal bone. The tooth was deemed restoratively hopeless. Preoperative radiographs revealed a bone height of 11 mm available for implant placement but a length of 13 mm was treatment planned (Figure 12). The patient had a history of heavy bruxism. Sinus augmentation of 2 mm to 3 mm above the implant length was desired in this case at a location where the sinus floor was beginning to ascend to form the anterior wall.
Septocaine® in a 4% solution with 1:100,000 epinephrine (Septodont, www.septodont.com), was locally administered as an anesthetic. A sulcular incision was made on the lingual aspect of the crest and a full-thickness flap was elevated to expose the fractured root. A bone-cutting bur was then used to create an osteotomy along the mesial and distal surfaces of the root. This allowed for osteotomy and troughing at the expense of the residual dilacerated root facilitating elevation, luxation, and extraction to be performed atraumatically.
Based on measurements of the residual root’s cervical width and length, it was planned for placement of a 5-mm wide implant with a 13-mm length. This would allow the implant to engage native bone beyond the residual root’s width and length. Preparation of the site would be to within 2 mm of the measured sinus floor. A 2-mm twist drill with a 9-mm stop was used in an electric surgical handpiece to create the initial osteotomy in the desired implant position. Following this, a series of osteotomies were performed using the 2.8-mm, 3.3-mm, and 3.8-mm diameter drill with the 9-mm vertical stop. The 10-mm and 11-mm vertical stops were then used to create an in-fracture of the sinus floor.
The hydraulic lifter with 1 mm of sterile water was introduced into the osteotomy to elevate the membrane from the bone, creating space for bone graft material. Allograft particular material (AlloOss™, ACE Surgical Supply, ) was combined with autogenous bone and enamel matrix protein derivative (Emdogain, Straumann USA, www.straumann.us). This combination of graft material was put into the osteotomy and pushed into the sinus with the bone condenser. A 3-mm rotary bone spreader was used at 20 rpm to evenly distribute the graft and further elevate the sinus. The sinus was elevated 5 mm in vertical height and the implant, a 5-mm x 13-mm Hiossen HG III was then placed. A cover screw was placed and then the flap was repositioned and the site was closed with silk 3.0 interrupted sutures (Figure 13 and Figure 14).
During the past 35 years, sinus lift procedures have become a common and predictable surgical procedure for implant placement into the atrophic posterior maxilla. Traditional procedures include the lateral wall approach and the subantrial augmentation. However, the risk of tearing the Schneiderian membrane is a common complication of these procedures that requires intra-operative management for successful implant survival. Repairing the torn membrane may include suturing the torn membrane, placement of a collagen barrier, or, in cases of a large tear, abandoning the implant surgical procedure for reentry at a later date after reestablishment of membrane integrity.
A safe, crestal-approach sinus augmentation has been described using the CAS-KIT in which the clinician may perform sinus-lift procedures with increased safety and without the risk of membrane tear. Using a series of safe end/side-cutting burs designed to prepare the site in a manner where a small conical bone chip from the sinus floor is pushed into the sinus during the final osteotomy, various vertical stops ranging from 2 mm to 12 mm are incorporated onto the burs and other instruments allowing for preparation of the site 1 mm to 2 mm below the sinus floor. The final osteotomy is made by switching the vertical stop to one slightly deeper that penetrates through the sinus floor, pushing a small conical bone chip superiorly into the sinus. A hydraulic lift using 1 cc of sterile water/saline is introduced after the sinus floor is elevated, gently elevating the sinus membrane. Bone graft material can then be introduced through the osteotomy in succession using the condenser and rotary bone spreader to evenly distribute the graft material. Once the desired bone height is achieved via the augmentation, the implant can be placed. This technique may be used for single sites or adjacent sites.
Subantrial sinus elevation has lower surgical complications then the traditional lateral window approach. Using the CAS-KIT, clinicians can predictably incorporate sinus augmentation into their implant surgical regime. The CAS-KIT provides an alternative, lower-risk method for sinus lift when compared to the traditional methods of lateral wall or crestal augmentation via osteotome use.
Dr. Dompkowski teaches surgical implantology for Hiossen and has received financial compensation from the company for such teaching.
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About the Authors
Gregori M. Kurtzman, DDS
Silver Spring, Maryland
Douglas F. Dompkowski, DDS