July 2, 2019
by Jim Yeganegi, BSc, DMD
The goal of the implant surgeon is to place an implant in the ideal position, that will support a prosthesis with the best long-term prognosis, while managing important anatomical landmarks. With the aid of Cone Beam CT scans the implant surgeon is able to evaluate, in three dimensions, the ridge, important anatomy, as well as to pre-plan ideal implant positioning. Advances in CT Scans, Soft Tissue Scans, and Dynamic Surgical Navigation allow the surgeon to better serve the patients’ implant needs. The following case presentation demonstrates the incorporation of dynamic surgical guidance (Inliant Surgical Navigation System) in preparing the osteotomy and manipulating the maxillary sinus floor to allow placement of the preferred implant size in the posterior maxilla following extraction, site development and healing of tooth 16.
Methods and Rationale
The posterior edentulous maxilla poses different challenges in selecting, preparing and placing implants that will have good long-term success. These challenges include: lower density, poorer quality bone (D4 Misch classification), pneumatization of the maxillary sinus, and crestal bone resorption following tooth extraction. The residual bone, visibility and access during osteotomy preparation are limited. Wider and longer-bodied implants are preferable. The maxillary sinus is often utilized through either a lateral window approach or a crestal approach to separate the schneiderian membrane, allowing placement of implant(s) with/without grafting. Most recently, the Hiossen CAS Kit (Osstem Implant Company) has provided functionality, efficacy, and science for crestal approach sinus lifts/bumps in the posterior maxilla. CAS Kit utilizes parallel drills with measured stops to incrementally approach the sinus floor and allow penetration without perforating the schneiderian membrane.
There is often some individual variance in the residual ridge height measurements, and the incline and anatomy of the sinus floor (dependent on who is evaluating and interpreting the CBCT). If the surgery is begun with a pre-determined vision of penetrating the sinus floor at “X” millimetres, the reality of the procedure often proves otherwise. Slight changes in angulation, on any plane, can result in a delayed or premature penetration of the sinus floor from the preplanned CT scan (Figs. 1A & 1B). This is the reality of free-hand oral osteotomies and even more challenging at the level of the sinus floor.
The Inliant surgical navigation system allows pre-planning the implant position (Figs. 2A & 2B) and visualizing the drill in real time during surgery. This technology greatly reduces angulation variance and permits the visualization of the drill tip with respect to the sinus floor (regardless of sinus floor slope, inclines, bony septum, or other anatomical features). Thus, sinus floor “penetration” involves no guess work and less stress.
The patient presented with “pain and swelling in the upper right back tooth” indicating tooth 16. She had no sensitivity to thermal stimulus; however, she felt her tooth “was swollen, and it hurt when she attempted to chew on it”.
No facial asymmetry, edema or lymphadenopathy were noted. TMJ function and range appeared normal.
Hard and soft tissues were normal with the exception of the buccal marginal gingiva (noticeably inflamed and tender) around tooth 16. Pressure in the region generated some exudate. Probing depths in the URQ were 1-4 mm except for 8 mm on the MB aspect of 16. No mobility was noted. A periapical radiograph was taken (Fig. 3).
Diagnosis and Treatment Options
The patient was informed about the low-grade infection around 16 where bone had been compromised. Treatment options (retreatment, a three-unit bridge, and an implant) were discussed, and an endodontist was consulted. The merits, procedures, long-term prognoses, and costs were reviewed.
Endodontic examination revealed an internal MB fracture and an untreated second mesial canal; extraction was the only option. The patient decided on an implant placement.
Tooth 16 was sectioned and extracted atraumatically. The socket exhibited a four-wall bony defect with dehiscence of the mesial buccal plate. The socket was completely debrided and the bone sterilized and conditioned using a laser. A resorbable collagen membrane isolated the defect. The socket was grafted with particulate allograft (50/50 corticocancellous bone), overlaid with a non-resorbable PTFE membrane, and allowed to stabilize for four weeks. This technique provides granulation and maturation of a zone of keratinized tissue over the ridge crest for eventual coverage of the implant/prosthesis.
The patient was seen four weeks following grafting and had no post-operative complications. Soft tissue formation had begun underneath the protective PTFE membrane (Fig. 4).
At this time, a chairside Inliant fiducial was positioned for a CBCT to evaluate the grafting, the residual ridge height, and to assist in implant planning.
CBCT Interpretation and Surgical Tx Planning
Evaluation of the CBCT scan revealed a well-healed socket with complete resolution of the buccal dehiscence. Ridge width in the buccal-palatal dimension was 8.9 mm and interdental (CEJ to CEJ) space was 12.3 mm. The sinus anatomy was unremarkable, with a normal membrane, no pathology, and a narrow lateral to medial wall dimension. The implant selected was a Hiossen ET III 5 X 10 mm. Given the residual bone height of 9.2 mm and favorable sinus anatomy, the surgical plan included dynamic navigation to approach the sinus floor, using the Hiossen Crestal Approach Kit (CAS Kit). Since the membrane was to be lifted only 1-3 mm, the plan was to introduce PRF into the lifted space and then to place the implant (Fig. 5).
The Inliant software allowed the demonstration of the surgical plan to the patient resulting in a more informed, less apprehensive patient.
Soft tissue profile, and zone of keratinized tissue was deemed acceptable across the ridge, and the surgery did not require incision or flap elevation. With dynamic navigation, the clinician can visualize the drill penetrating through the soft tissue. After clinical confirmation, a tissue punch removes a collar of tissue to allow for the preparation of the osteotomy with minimal tissue trauma. There is less likelihood of bone resorption as periosteum is not lifted, less post–operative discomfort, and faster healing. The patient was fitted with the same fiducial the scan was taken with, the Inliant system activated, and surgical mode initiated using real-time vision. The pilot drill was then used to penetrate into the bone (Fig. 6).
The CASKit was used to sequentially enlarge the osteotomy and then to progress apically towards the sinus floor. During the initial drilling the twist drill could be visualized drifting distally due to the soft bone. With dynamic navigation as a visual guide, it was easy to correct the osteotomy at this early stage using a side-cutting Lindemann bur (Fig. 7).
The osteotomy was underprepared in width, given the bone quality was D4. A major advantage of free-hand dynamic navigation versus a static guide is that the surgeon can feel the quality of the bone while drilling. As penetration through the sinus floor was felt, an initial visual check for a perforation was followed by Valsalva’s test.
Given the small lift required, PRF membranes were gently placed up the osteotomy into the sinus. The implant was driven into the osteotomy and final positioning was done using a fixture driver. Initial stability values were adequate to allow placement of a healing abutment. There was minimal bleeding at the site and no sutures were used. A post-operative periapical radiograph was taken, and the patient given post-operative home care instructions (Fig. 8).
This patient had previously had anterior implant treatment without dynamic navigation. She reported that the dynamic navigation procedure was faster and smoother. She felt less pressure and pulling than in her previous experience. She was also happy to have no sutures (Figs. 9 & 10).
The patient was seen five months post-operatively for the prosthetic phase. A fixture level impression was taken, and the final prosthesis delivered (Fig. 11).
From an operator standpoint, dynamic surgical navigation allows predictable and consistent implant preparation and placement in an ideal 3-dimensional (mesio-distal, bucco-lingual and apico-coronal) position. The advantages of free-hand drilling include tactile sense of the bone, drill angulation if the patient’s opening is limited, and irrigation to the osteotomy. Inliant surgical navigation offers direct visualization of the drill as it moves through the bone. This allows corrections to be made accurately, and key anatomical structures, such as the sinus floor, to be visualized directly. Where soft tissue profiles permit, surgeries can be flapless, providing less post-operative discomfort, better and faster healing for the patient, and a successful overall experience for both patient and clinician.
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About the Author
Dr. Jim Yeganegi, BSc, UBC, DMD, Tufts, Boston, MA. Upon returning to Vancouver and successfully completing the Canadian Board examinations he began associating with Dr. Arthur Ross. He purchased the practice in 2001. He began his education and training in implant dentistry in 2007. He completed the AAID Maxicourse in Vancouver and completed Part one of the Associate Fellow of the American Academy of Implant Dentistry and is currently challenging Part II Associate Fellow. His passion for Implant Surgery has led him to become the first adopter of the Inliant Surgical Navigation System in Canada.