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Dynamic Navigation for Precision Crestal Approach Osteotomy Near the Maxillary Sinus Floor - Case study

Mar. 14, 2021

Courtesy ofNavigate Surgical Technologies Inc.

INTRODUCTION

The goal of the implant surgeon is to place the implant in the ideal position, to support the prosthesis for 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 dimension, the ridge, important anatomy, as well as pre-plan implant placement in the most ideal position. Advancements in technology such as CT Scans, Soft Tissue Scans, and Dynamic Surgical Navigation allow the surgeon to better serve the implant needs of his/her patients. The following is a case presentation on how I incorporate dynamic surgical guidance, using the Inliant Surgical Navigation System, in preparing the osteotomy and manipulating the maxillary sinus floor to allow placement of my preferred implant size for the posterior maxilla following extraction, site development and healing of the upper right first molar (Tooth #16).

METHODS AND RATIONALE

It is my personal preference to place a wider and longer fixture in the posterior maxilla where bone quality and density is considered less than ideal and where the highest incidences of implant failures occur. While it has been shown that short implants function and have predictable long-term success, this is likely a reflection of shorter implants used in the posterior mandible where bone quality and density are favorable for allowing good initial stability and long-term support for the implant and prosthesis. The posterior edentulous maxilla poses different challenges in choosing, preparing and placing implants that will have good long-term success. The posterior maxilla is generally comprised of lower density and poorer quality bone (D4 Misch classification).

Pneumatization of the maxillary sinus as well as crestal bone resorption following tooth extraction limit the residual bone, visibility and access during osteotomy preparation. My personal choice is to place wider and longer-bodied implants in order to increase bone-to-implant contact. As such, in nearly all of my posterior maxillary implant placements I utilize the maxillary sinus through either a lateral window approach or crestal approach to separate the schneiderian membrane, allowing placement of implant(s) with or without graft. The crestal approach osteotomy can be done using many different tools and surgical kits. My personal experience began with the use of osteotomes manually approaching and penetrating the sinus floor, progression to the use of tapered compressing drills (MIS sinus and bone compression kit). For the past four years I have used the CASKIT from HiOssen (Osstem Implant Company). The functionality, efficacy and science behind this wonderful kit are topics for another presentation, but this is the sole modality by which I do crestal approach sinus lift/bumps for the posterior maxilla. The system is designed to use parallel drills with measured stoppers (resting against the ridge crest) to incrementally approach the sinus floor and allow penetration without perforating the schneiderian membrane. When the surgeon evaluates, interprets the Cone Beam CT Scan and does his/her measurements of the residual ridge height prior to sinus floor penetration, there is often some variance in the measurements based on the person manipulating the scan, and the incline and anatomy of the sinus floor.

When the surgeon initiates surgery with a pre-determined vision of penetrating the sinus floor at “X” milimeters, he/she soon realizes the reality of surgery proves otherwise and this can be confusing and frustrating during surgery. These variances are often the result of the position and preparation of the osteotomy when approaching the sinus floor. Slight changes in angulation in any plane can result in a delay or premature penetration of the sinus floor from the anticipated, preplanned CT scan (Figures 1a-1b). This is the reality of free-hand osteotomies in any area of the mouth and most certainly can be challenging when one is trying to approach and penetrate the sinus floor.

Using the Inliant dynamic navigation technology, I am able to pre-plan the implant position and, during surgery, visualize the drill, “in real time”, as it moves through the planned osteotomy. This sharply reduces the variance in angulation and allows me to visualize the relationship of the drill tip to the sinus floor regardless of slope of the sinus floor, inclines, bony septum, or other anatomical features of the sinus. Thus, the moment of sinus floor “penetration” involves far less guess work and stress during the surgery.

THE CASE

The patient presented with a chief concern of “pain and swelling in the upper right back tooth”. She had no sensitivity or reaction to thermal stimulus; however, she felt her tooth “was swollen and hurt when she attempted to chew on it”. She points to tooth #16 as the source of her pain.

EXTRA-ORAL EXAM

No facial asymmetry, edema or lymphadenopathy were noted. TMJ function and range appeared normal.

INTRA-ORAL EXAM

There were no visible failing restorations, or cracked/fractured teeth in quadrant one. The soft tissues were normal in appearance with the exception of the buccal m

arginal gingiva, around tooth #16, which was noticeably inflamed and tender to touch. Some exudate was expressed on application of pressure in the region. Probing depths were in the range of 1-4mm throughout the quadrant with the exception of the mesiobuccal aspect of #16 which probed 8mm. No mobility was noted on any of the teeth within the quadrant. With the patient’s consent, a peri-apical radiograph of the region was taken. Review of the radiograph revealed an area of radiolucency around the mesial root. The tooth showed to have previous endodontic treatment. There was no sign of recurrent caries or marginal failure, either clinically or radiographically.

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DIAGNOSIS AND TREATMENT OPTIONS

I explained to the patient that the pain and swelling were due to a low-grade infection around the base of the tooth. I showed her the area of “darkness” (radiolucency) around the root and explained that the bone in this region had been compromised and the pain and swelling were due to pressure build up around the base of the tooth. We discussed the options of consulting with an endodontist regarding the viability of endodontic retreatment, removing the tooth and replacing it with a three unit fixed bridge, or replacing it with a dental implant. The merits, procedures, long-term prognosis and costs of these treatment options were reviewed.

TREATMENT PROPOSAL

Following consultation with an endodontist it was determined that the long-term prognosis for the tooth was hopeless due to an internal fracture within the meisobuccal root as well as an untreated second mesial canal. The patient was advised that extraction of the tooth was necessary. After considering the different treatment options the patient had decided to proceed with implant placement as she had other implants placed in the past and was familiar with the procedures and long-term results. Prior to the extraction appointment I had discussed the bone loss around the mesiobuccal root and had advised her that the likelihood of doing an immediate placement following extraction was very limited and the likely scenario would be complete debridement and sterilization of the socket, with site development via grafting the buccal defect of the socket and allowing the soft tissue across the ridge crest to develop. Once this was completed then we would plan our implant placement.

TREATMENT RENDERED

The patient was seen for the extraction of tooth #16. Under local anesthesia, the existing PFM was sectioned and removed. The tooth was then sectioned and atraumatically extracted. Evaluation of the socket confirmed the preoperative symptoms/findings of a 4 wall bony defect with dehiscence of the buccal plate around the mesial root of the tooth. At this time the socket was completely debrided of soft tissue with the aid of hand instruments, a surgical handpiece and large round bur and finally a laser to sterilize and condition the bone.

Following socket preparation, the buccal tissue was tunnelled off of the buccal bone so the boundaries of the dehiscence could be visualized. The palatal marginal tissue was tunnelled off the crestal bone to allow some mobility of the tissues. A piece of long-lasting resorbable collagen membrane was shaped to cover the defect and beyond its boundaries. The membrane was tucked into the buccal tunnel to isolate the defect from the periosteum and soft tissue.

The socket was then grafted with particulate allograft (a mix of 50/50 corticocancellous bone). Finally, the graft was overlaid with a piece of non-resorbable PTFE membrane shaped to cover the socket and extend buccally/palatally far enough to be tucked under the marginal tissues and ensure that the proximal boundaries were at least 1.5mm away from the roots of the adjacent teeth. The membrane, tucked under the tissues and covering the graft, was then secured with various suture techniques to stabilize it for a period of 4-6 weeks. This is a double membrane technique which is a viable treatment option, using two different membranes to cover the bony defect and the graft, while allowing soft tissue maturation beneath the latter. The advantage of this technique is the eventual granulation and maturation of a zone of keratinized tissue over the ridge crest, thus maintaining a suitable zone of attached tissue for coverage of the implant/prosthesis later on.

Four weeks following extraction and grafting the patient was seen and she reported no complications post operatively. The PTFE membrane was removed and soft tissue formation had begun underneath which now served to cover and protect the graft. The patient was seen again four months post-operatively. The soft tissue profile was excellent with a fully matured zone of attached keratinzed mucosa across the ridge. At this time an Inliant fiducial was made chairside, taking approximately 3-4minutes, and a CBCT scan taken with fiducial in place, to evaluate the results of the grafting, the residual ridge height and to aid in the implant planning.

INTERPRETATION OF CBCT AND SURGICAL TX PLANNING

Evaluation of the CBCT scan revealed a well healed socket with complete resolution of the buccal dehiscence. Typical of this region, a thin buccal cortical plate was visible throughout the edentulous space and a thicker palatal cortical plate was noted with abundant cancellous bone at the core. Given the nature of the bone in this region of the mouth, and that it was a grafted socket the expectation is that of low density and less than ideal quality bone (D4). The residual bone height (RBH) from ridge crest to the sinus floor was measured at 9.2mm. Ridge width in the buccal-palatal dimension was 8.9mm and interdental (CEJ to CEJ) space was 12.3mm. The sinus anatomy was unremarkable, with a normal membrane (non visible), no pathology and a narrow lateral to medial wall dimension.

My choice of implant for the site was a HiOssen ET III 5 X 10mm. Given the RBH of 9.2mm and favorable sinus anatmoy, the surgical plan would be to use dynamic navigation to approach the sinus floor, with the Crestal Approach Kit (CASKit) from HiOssen. This kit is designed to incrementally approach and penetrate the sinus floor. Once penetration is achieved, saline is injected slowly, using hydraulic pressure, to separate the schneiderian membrane from the bony walls. Depending on the amount of lift needed, the operator then can determine if he/she will introduce graft, blood products or simply place the implant and allow the implant apex to tent the membrane. In this particular case, because we were merely lifting the membrane by only 1-3mm, the plan was to introduce PRF into the lifted space and then place the implant.

The challenges with such surgery using free hand technique are maintaining complete control of the osteotomy in soft/grafted bone, blindly approaching the sinus and anticipating the “moment of penetration.” There are variances in how one angulates the handpiece, using landmarks in preparing the osteotomy. These can have an effect on when and how the sinus is penetrated and the final osteotomy/implant positions. By using the Inliant system one can pre-plan the osteotomy, and in real-time visualize the osteotomy drill approach the sinus floor in the position/angulation that is determined to be ideal by the operator. Care and traditional protocol are still used to ensure penetration, and integrity of the membrane.

“Once the planning was completed I was able to show the patient, using the Inliant software, the surgical plan, final implant position in relation to the sinus walls, and the adjacent teeth. The visual review is a great aid in helping patients understand our methodology, reasoning and approach to the recommended treatment. This ultimately results in a more informed, less apprehensive patient with higher case acceptance.”

SURGICAL APPOINTMENT

The patient presented for surgery having taken the premedication regiment and a review of the procedure was completed prior to blood draw. Once blood draw was completed, the processing of PRF was immediately initiated and the patient anesthetised. Extra and Intra-Oral scrub with a sterile rinse was completed. The surgical site and soft tissue profile was examined and deemed to be healthy and suitable for surgery. Given the soft tissue profile and zone of keratinized tissue was abundant across the ridge, the surgery would be performed without an incision and elevation of a flap.

Dynamic Navigation for Precision Crestal Approach Osteotomy Near the Maxillary Sinus Floor - Case study

DIAGNOSIS AND TREATMENT OPTIONS

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