June 10, 2019
by Bao-Thy N. Grant, DDS
Dental implant therapy has made progress toward a truly digital workflow via cone beam computed tomography (CBCT) imaging and fabricated physical guides.1,2 The latest development, however, toward an ultimately digital implant therapy workflow is robotic assistance. Robotic assistance has spread across many medical surgical disciplines with strong evidence for its utility in augmenting and enhancing surgical capabilities.3-5 The first FDA-cleared robotic device for dental surgery, Yomi (Neocis, Inc.), is commercially available and in clinical use in the United States.
With Yomi-Enabled Surgery (“YES”), the procedure is planned virtually on the patient’s CBCT scan based on restorative goals, similar to other digitally-driven procedures. In contrast to such procedures, Yomi also offers novel assistance in the form of robotic guidance called haptics. Haptic guidance provides directional and proportional feedback forces to the surgeon, which the surgeon experiences via Yomi’s robotic guidance arm that prevents deviation from the virtual plan. Notably, the robotic guidance arm does not move until a force is applied by the surgeon. Unlike with a static guide, the digital nature of the plan and guidance enables the surgeon to modify the planned implant position at any time. The surgeon fully controls initiating and pausing drilling and can modify the plan at any time or go into a completely freehand operation.
This article introduces “YES” for dental implant therapy, including two case reports from early clinical experience of a board-certified oral and maxillofacial surgeon at the Center for Oral Reconstruction & Education, a full-scope oral and maxillofacial surgery private practice in Orange, California, USA. These case studies demonstrate the ability of Yomi-Enabled Surgery to achieve highly accurate implant placement and suggest an important future role in private practice oral surgery.
At the Center for Oral Reconstruction & Education, the following Yomi procedural workflow has been established, melding the manufacturer’s training protocols with the center’s mission for providing exceptional patient care. The Yomi surgical plan may be designed in advance or on the same day as the implant placement procedure. Yomi Plan, an integrated planning software, accepts DICOM files from CBCT scanners as well as STL files from intraoral scanners, to allow for prosthetically-driven treatment planning. In preparation for the surgical procedure, an intraoral splint is affixed to patient dentition contralateral to the surgical site (Fig. 1). This splint provides a fixed location from which the patient DICOM file is first registered to the Yomi system and then tracked intraoperatively. An array of materials may be used to line the splint for mechanical retention; bisacryl was used in the cases reported here. A fiducial array is magnetically attached to the intraoral splint and a DICOM image is obtained of metal beads embedded on the fiducial array and of the surgical area (Fig. 2).
Intraoperatively, the Yomi system extends laterally over the patient. A patient tracking arm connects to the intraoral splint, monitoring patient motion (Fig. 3). If the patient moves during the surgical procedure, the system responds to maintain the accuracy of the drill placement. To confirm system accuracy prior to the procedure, a landmark point on the virtual plan is verified by placing the drill tip on the chosen anatomical landmark.
Osteotomy preparation and implant placement may then proceed with Yomi guidance (Fig. 4). Haptic guidance is delivered via the robotic guidance arm that holds and stabilizes the implant handpiece. As the user moves the drill toward the site of surgery, the robotic guidance arm permits the motion; as the user moves the drill away from the site of surgery, the robotic guidance arm resists. When the planned angulation, location, and depth are achieved, the robotic guidance arm retains (“locks”) the handpiece on plan, preventing unplanned deviation from the desired angulation, location, or depth. On the monitor, the positions of the handpiece and patient 3D image are updated in real time to provide additional visual navigation and visual confirmation as needed (Fig. 5).
At the end of the robotic portion of the case, the patient tracker arm is removed. The intraoral splint may be removed via gentle rocking or by cutting through the bridges in the seam overlaying a contrast-colored splint insert. At this point, a postoperative CBCT scan may be obtained as desired.
For the cases in this report, analysis was performed to assess deviation between the preoperative plan and the implant location on the CBCT, using methodologies outlined by the 2018 ITI Consensus Reports Working Group.2
The following Yomi case studies are examples of early clinical experience at the Center for Oral Reconstruction & Education, a full-scope oral and maxillofacial surgery private practice in Orange, California, USA.
Case Study 1: Immediate Implant Placement Following Molar Extraction
This case study reports immediate implant placement following extraction for a 65-year-old male patient who presented complaining of a fractured symptomatic molar. Clinical and radiographic evaluation revealed that the crown of endodontically-treated tooth #19 had fractured, leaving non-restorable decayed root tips. Inflamed gingival biotype was also noted. Furcation bone loss was observed but adequate thickness for implant placement was noted between the molar roots.
When restoring the posterior mandible, the desired drill angulation (e.g., to ensure placement at a safe distance from the inferior alveolar nerve) may be difficult to maintain because of challenging access and limited visibility.6 However, surgical guides with the longer drill channels necessary to reduce angle deviations may further restrict access to the surgical site.7,8 Additionally, immediate implant placement into a molar extraction socket is generally recognized as a more complex procedure in comparison with implant placement in a healed ridge of adequate bone quality.9,10 Due to these known challenges, robotic guidance was recommended for the surgical extraction of tooth #19 with ridge preservation in order potentially to enable immediate implant placement. The patient was advised that the site would be evaluated after extraction and that implant placement might need to be delayed.
The Yomi intraoral splint was attached and a DICOM image obtained as described above. A 4.8×8 mm implant (Straumann Bone Level RC) was planned at the site of broken tooth #19 (Fig. 6). The surgeon planned for implant placement in the bony furcation between the mesial and distal roots.9 The inferior alveolar nerve was identified and determined to be a safe distance from the apex of the implant. Low bone density and probable crestal bone loss were noted at the buccal and lingual aspect of the planned implant location1, highlighted in red on the virtual implant. Bone grafting was therefore planned for this location.
The patient was placed under IV deep sedation and local anesthesia was administered to the surgical area. A sulcular incision was made around the fractured tooth and a mucoperiosteal flap was elevated minimally. Bone quality was probed and determined to be type II.11 Prior to extraction, the implant site was prepared with Yomi robotic guidance. The 2.0, 2.2, 2.8, and 3.5 mm diameter drill series progressed in the prescribed fashion through the remainder of broken tooth with the drills at slow speed and copious irrigation. The root tips were then extracted and removed from the osteotomy and the site was curetted free of granulation tissue. The 4.2 x 22 mm bit was then drilled and the dental implant was rotated into place with good stability, torque value >35 N-cm. A 6.5 x 4 mm healing abutment was placed and an allograft (Puros, Zimmer) was placed in the socket surrounding the implant to improve ridge contour and cover the exposed threads. The tissues were adjusted and reapproximated with 4-0 chromic gut. A low-resolution postoperative CBCT scan was taken, showing the implant was placed according to plan in the extraction socket (Fig. 7). In subsequent quantitative analysis, deviation from plan was confirmed to be sub-millimetric at both the apex and crest of the implant. Three months postoperatively, gingival tissues were pink and healthy (Fig. 8), and the implant appeared to be clinically and radiographically ready to restore (Fig. 9).
Case Study 2: Robotic Guidance to Sinus Floor for Modified Summer’s Sinus Lift
The patient was a 42-year-old female who had initially presented with an endodontically-failed tooth #14 and a palatal root visible in the maxillary left sinus (Fig. 10). The tooth had been deemed non-restorable due to recurrent decay. The tooth had been extracted and ridge preservation performed using an allograft. After the site healed for five months, while adequate gingival biotype was present, the CBCT scan revealed adequate bone width but inadequate bone height in the area of #14. To build the height necessary for implant placement, a modified sinus augmentation via Summer’s technique was planned for the left maxillary sinus. While the Summer’s sinus floor elevation technique with osteotome may be more straight-forward and less invasive than access through the lateral wall of the sinus, sinus membrane rupture is a concern with this technique.12,13 To reduce the risk of membrane rupture, Yomi-Enabled Surgery was employed to provide robotic guidance precisely to the sinus floor.
Yomi case preparation proceeded as outlined above. In the Yomi Plan software, a 4.1 x 8 mm implant (Straumann BL RC, Straumann) was planned at first molar #14 (Fig. 11). A deep red color was observed on the apex of the virtual implant, corresponding to very low CBCT voxel values surrounding the virtual implant in that area and indicating that an 8 mm implant thus would be in the sinus cavity.
In order to guide the drill tips precisely to the floor of the sinus, the virtual plan was modified for a 6 mm osteotomy (Fig. 12). The surgeon then planned to gently elevate the sinus floor, place the bone graft, and then place the 8 mm implant with the superior 2 mm in the newly-grafted sinus.
Intraoperatively, a tissue punch was used to remove a plug of tissue at the crest of the ridge at the surgical site. The bone quality was II.11 Using robotic guidance, the implant site was prepared using 2.0, 2.2, 2.8, and 3.5 mm diameter drills per the manufacturer’s protocol with copious irrigation. Robotic guidance provided depth control, halting osteotomy preparation at the planned depth of 6 mm at the sinus floor. Osteotomes were then introduced, progressing up in size while gently elevating the sinus floor. A xenograft (Bio-Oss, Geistlich) and allograft (Puros, Zimmer) were placed in the site and manually tapped superiorly with osteotomes. A dental implant (BL RC 4.1 x 8 mm, Straumann) was then rotated into place with robotic guidance to a depth of 6mm, then hand torqued the last 2 mm for a final depth of 8 mm. Implant stability was confirmed with a torque value measured at 35 N-cm. A 5 mm x 4 mm healing abutment was placed. Analysis of postoperative CBCT images with respect to the preoperative virtual plan revealed implant placement that was within 1 mm of the planned location at both the implant crest and apex (Fig. 13). Restoration was planned for four months postoperative with temporization of implant #14 to develop the gingival architecture. Examination at 10 weeks follow-up revealed excellent soft-tissue healing (Fig. 14).
In the specific cases outlined in this report, Yomi robotic guidance assisted with implant placement immediately after molar extraction and in conjunction with a modified Summer’s sinus lift, obtaining accuracies in line with those reported for surgical guides.2 While printed surgical guides are commonly used to help secure implant placement, Yomi’s fully digital workflow provides intraoperative conveniences that include direct visualization of the surgical site, access for instrumentation and irrigation, the ability to readily perform same-day guided surgery, and the flexibility to adjust the plan intraoperatively and continue with the procedure with guidance. Additionally, a key step of each Yomi procedure is verification of end-to-end system accuracy through alignment of an anatomical landmark with a virtual landmark. This verification is not readily available with printed surgical guides. Therefore, Yomi’s haptic robotic guidance may provide the surgeon with practice efficiencies relative to fabricated surgical guides while supporting precise implant placement.
As noted in the first case, Yomi haptic guidance helped obtain accurate implant placement into the bony furcation of an extraction socket with irregular topography. Maintaining the desired angulation in posterior edentulous sites can be difficult when operating freehand due to limited access, and the bulk of printed surgical guides can be an impediment to site access, whereas Yomi demonstrated the capability to provide digitally-guided access to the planned site and maintain the implant placement on plan. In the second case, Yomi guidance helped to realize the benefits of the less invasive Summer’s sinus lift while mitigating the risk of membrane tear by providing real-time haptic guidance relative to the virtual plan. The Yomi robotic guidance provided depth control, halting osteotomy preparation at the sinus floor, while allowing the surgical site to be directly visualized throughout the procedure.
Surgical robotics is no longer a future concept but rather a dynamic surgical field with thousands of medical robotic systems in use worldwide. Moreover, surgical robotics is progressing to address an increasingly diverse array of procedures and is now emerging in oral surgery. In medical literature, robotic assistance has been reported to enhance surgical precision, increase the quality of life of the surgeon through surgical endurance, and to support the surgeon with real-time guidance and warnings.3-5 Yomi-Enabled Surgery brings surgical robotics into dental implant therapy with drill guidance to augment the precision of the surgeon’s unassisted hand. We see this guidance as valuable, for example, in arriving at the surgical areas where the inferior alveolar nerve or maxillary sinus is present, especially in difficult cases of atrophy. The greater vision is to introduce predictable capabilities through robotic assistance that are not consistently possible during a conventional surgery.
When considering implementing robotics in our surgical practice, we were cautious that introducing novel technology should not induce undue uncertainties but rather make it easier to operate. When initially evaluating the technology, we perceived clinical value in the potential to perform proper dynamic planning with predictable outcomes. During our clinical experience, the capabilities of the robotic software augmented the expertise of the oral surgeon in planning and executing the case. This synergistic relationship allowed for a comforting and transparent discussion with patients that enhanced their confidence in their care. We believe that surgical robotics, as an extension of the surgeon’s hand, will become the standard, rather than the exception, for surgical procedures with treatment for a wide range of conditions.
Advancement in dental implant therapy is marked by an embrace of digital technology that has improved the oral health, oral function, and quality of life of patients. Robotic surgery has been associated with unprecedented technological growth across many medical specialties. We believe that as oral surgeons embrace robotic surgery, through case planning accuracy, surgical precision, surgeon comfort, patient safety, and transformed surgical techniques, we can enhance patient care in our field.
Oral Health welcomes this original article.
Disclosures: The author received no financial support or in-kind donation from any company in relation to this case report.
About The Author
Bao-Thy N. Grant, DDS is a Board Certified Oral and Maxillofacial Robotic Surgeon and owner of the Center for Oral Reconstruction & Education (CORE), a full scope oral and maxillofacial surgery private practice in Orange, California. Dr. Grant completed her undergraduate degree in Business and her Doctor of Dental Surgery (D.D.S.) from the University of Southern California. She completed her postgraduate residency in Oral & Maxillofacial Surgery at Montefiore Medical Center/Albert Einstein College of Medicine. Dr. Grant is also on staff at St. Joseph Hospital of Orange and Children’s Hospital Orange County. She is currently the Oral and Maxillofacial Surgeon for the Anaheim Ducks NHL team.