With the increase in the number of implants placed per year, there has been increasing demand for more simplified surgical workflows to improve the patient experience and accelerate treatment outcomes. Guided surgery utilizes the concept of “prosthetically driven treatment planning” and is purported to reduce surgical complications and, thereby, improve treatment outcomes. Some of the main barriers to implementing guided surgery include cost and the complexity of the guided workflow.
As dental implant treatment has become more predictable, the focus has turned toward more prosthetically driven treatment planning, whereby the implant position is dictated by the intended position of the future prosthesis.1 This requires detailed pretreatment planning to ensure a correct 3D implant position is achieved within the alveolar bone relative to the planned prosthetic position. The purported benefits of prosthetically driven treatment planning include improved functional and aesthetic outcomes due to the ideal positioning of the implants. This may also contribute to faster surgery, less intraoperative patient discomfort, reduced bleeding, reduced edema, less postoperative pain, and quicker recovery.
An additional benefit is that the correct positioning of the implant enables the final prosthesis to be optimally designed and makes it possible to devise and fabricate retrievable screw-retained suprastructures, thereby avoiding non-retrievable cement-retained restorations.2
The concept of guided surgery was created to facilitate the most accurate placement of implants.
Guided Surgery
The term “guided surgery” in implant dentistry can be defined as a digital workflow that begins with the acquisition of data regarding the future patient prosthesis and continues with the digital processing of this information through virtual planning software.3 In conjunction with image-guided surgical/prosthetic template production, 3D implant planning software has been employed for many years.4 These techniques were primarily aimed at improving diagnostic, surgical, and prosthetic precision, and simplifying technique-sensitive and operator-dependent surgical procedures.
Within these implant-planning softwares, the DICOM data produced by the CBCT is merged with the STL of the patient’s intraoral situation, which may be acquired by either conventional means, such as impressions and scanning the produced stone model or, in a fully digital workflow, by means of an intraoral scan. The implant is then placed in the correct position within the bone volume (as dictated by the future prosthetic position), and the surgical guide is designed accordingly. The surgical guide produced is then exported from this software as an STL for subsequent fabrication by either additive (printing) or subtractive (milling) means.
The wide availability and decreasing price of 3D printing machines have now made the possibility of in-office fabrication of these guides a reality, thereby reducing the overall cost and turnaround time for the production of surgical guides. The accuracy of this process is the subject of this article.
Assessing Accuracy
The accuracy of guided surgery has been investigated in many studies.5-10 A recent meta-analysis by Tahmaseb et al11 stated that the mean error at the entry point was 1.2 mm, 1.4 mm at the apical point, and a deviation of 3.5 degrees.
The accuracy of the entire procedure is defined as the deviation between the position of the implant in the planning and the position of the implant postoperatively.12 Furthermore, the global deviation is defined as the 3D distance between the coronal (or apical) center of the corresponding planned and placed implants (Figure 1).
Cost Savings
A milled guide is dimensionally stable and usually less brittle than a printed guide. However, the cost of the material and milling machine, plus the material waste that results from the milling process, are drawbacks. Previous workflows involved the outsourcing of surgical guide fabrication to commercial laboratories. The associated time and cost of shipping models and a surgical plan created offsite has proved time-consuming and more costly. The cost of lab-manufactured guides may range from $200 to more than $700, whereas desktop-produced guides may reduce this to as low as $20 per guide.13
Recently developed, affordable, high-quality 3D printers offer an alternative that can produce a guide with limited material waste and minimal polymerization shrinkage.
In-Office Surgical Guide Production
Stereolithography, a rapid prototyping technology, allows the fabrication of surgical guides from 3D printed models for the precise placement of implants.14 The STL file generated from the planning software is exported as an open-source file to the production unit of choice. The most common in dentistry are the digital light processing (DLP) or stereolithography (SLA) variety. SLA printers create objects in sequential layers using ultraviolet light to cure a photopolymerizing resin from its liquid state, an additive manufacturing process. DLP has a similar methodology; however, its projector technology for photopolymerization allows for considerably faster processing times.
Once the object (surgical guide or model) is created, the support structures are removed, any residual uncured resin is removed, and the object is then subjected to further photopolymerization to ensure complete curing.
Case Report
This case report documents the use of a surgical guide for accurate implant placement to allow the use of the patient’s existing crown as an interim immediate restoration.
The patient presented to the referring dentist complaining of a fracture of tooth No. 8 (Figure 2). The tooth was deemed unrestorable, and the patient was referred for implant-supported tooth replacement.
Following the acquisition of intraoral scans (Medit i700 intraoral scanner) and CBCT imaging (Planmeca), the case was digitally planned using Blue Sky Bio software (Figures 3 and 4). The STL model of the guide was exported to the 3D printer (Ackuretta SOL) (Figure 5) and printed using Rodin Surgical Guide resin (Pac-Dent) (Figure 6). Rodin Surgical Guide resin is a FDA-registered medical device that has been successfully tested for biocompatibility. It exhibits high-strength mechanical properties and is specifically formulated for the fabrication of maxillary and mandibular arch custom surgical guide appliances. As a highly filled resin, it maintains dimensional stability during autoclaving for disinfection and sterilization. It is also resistant to chemicals, shatter-resistant, and odorless.
Rodin Surgical Guide resin requires a CAD/CAM-generated design that is then printed on a validated 3D printer and post-processed in a validated light curing device to ensure optimum biocompatibility.
The guide was processed according to the manufacturer’s instructions:
“Upon completion of the print, it is removed from the build platform and washed in 99% IPA in a vortex or ultrasonic bath for 5 minutes. Then, it is moved to a secondary vortex or ultrasonic bath with fresh 99% IPA for an additional 5 minutes. Note: Do not expose the printed guides to IPA for longer than a total of 10 minutes, to prevent material strength loss.
Compressed air is used to remove excess IPA and/or residual uncured resin. These steps are repeated until the restoration is thoroughly clean, leaving a shine-free, matte finish. Post-curing of the guide is carried out in a validated light-curing device following recommended time and temperature schedules, if applicable. Note: Post-curing must be performed to be in compliance with the FDA” (Figure 7).
Surgical Procedure
After removal of the fractured portion of the crown (Figure 8), the precise fit of the surgical guide was confirmed. The remaining root was then prepared in partial-extraction therapy fashion whereby the buccal (facial) portion of the root is left in situ in order to maintain hard-/soft-tissue dimensions (Figure 9).
Once the tooth was prepared, the guide was again placed (Figure 10), and the Universal Guided Surgery Tool (Southern Implants) was used to place a 4.0- x 13-mm implant with excellent primary stability (Figure 11). The resultant implant placement allowed the patient’s pre-existing crown to be prepared for use as an interim immediately loaded temporary crown (Figures 12 to 14).
Healing throughout the integration period was uneventful, and a definitive screw-retained zirconia crown was delivered at 3 months (Figure 15). The correct anatomical contours of the temporary and definitive crown and the ability to utilize the patient’s existing restoration as a temporary crown illustrate the accuracy of the surgically guided process.
CONCLUSION
Utilization of a fully guided, digital workflow can provide highly accurate and predictable clinical results and improved outcomes for our patients.
REFERENCES
1. Katsoulis J, Pazera P, Mericske-Stern R. Prosthetically driven, computer-guided implant planning for the edentulous maxilla: a model study. Clin Implant Dent Relat Res. 2009;11(3):238–45. doi:10.1111/j.1708-8208.2008.00110.x
2. Brandt J, Brenner M, Lauer HC, et al. Accuracy of a template-guided implant surgery system with a CAD/CAM-based measurement method: an in vitro study. Int J Oral Maxillofac Implants. 2018;33(2):328–34. doi:10.11607/jomi.5799
3. Ganz SD. Three-dimensional imaging and guided surgery for dental implants. Dent Clin North Am. 2015;59(2):265–90. doi:10.1016/j.cden.2014.11.001
4. Bencharit S, Staffen A, Yeung M, et al. In vivo tooth-supported implant surgical guides fabricated with desktop stereolithographic printers: Fully guided surgery is more accurate than partially guided surgery. J Oral Maxillofac Surg. 2018;76(7):1431–9. doi:10.1016/j.joms.2018.02.010
5. Vercruyssen M, Coucke W, Naert I, et al. Depth and lateral deviations in guided implant surgery: an RCT comparing guided surgery with mental navigation or the use of a pilot-drill template. Clin Oral Implants Res. 2015;26(11):1315–20. doi:10.1111/clr.12460
6. Kramer FJ, Baethge C, Swennen G, et al. Navigated vs. conventional implant insertion for maxillary single tooth replacement. Clin Oral Implants Res. 2005;16(1):60–8. doi:10.1111/j.1600-0501.2004.01058.x
7. Siessegger M, Schneider BT, Mischkowski RA, et al. Use of an image-guided navigation system in dental implant surgery in anatomically complex operation sites. J Craniomaxillofac Surg. 2001;29(5):276–81. doi:10.1054/jcms.2001.0242
8. Scherer U, Stoetzer M, Ruecker M, et al. Template-guided vs. non-guided drilling in site preparation of dental implants. Clin Oral Investig. 2015;19(6):1339–46. doi:10.1007/s00784-014-1346-7
9. Younes F, Cosyn J, De Bruyckere T, et al. A randomized controlled study on the accuracy of free-handed, pilot-drill guided and fully guided implant surgery in partially edentulous patients. J Clin Periodontol. 2018;45(6):721–32. doi:10.1111/jcpe.12897
10. Pettersson A, Kero T, Söderberg R, et al. Accuracy of virtually planned and CAD/CAM-guided implant surgery on plastic models. J Prosthet Dent. 2014;112(6):1472–8. doi:10.1016/j.prosdent.2014.01.029
11. Tahmaseb A, Wu V, Wismeijer D, et al. The accuracy of static computer-aided implant surgery: A systematic review and meta-analysis. Clin Oral Implants Res. 2018;29 Suppl 16:416–35. doi:10.1111/clr.13346
12. Van Assche N, Quirynen M. Tolerance within a surgical guide. Clin Oral Implants Res. 2010;21(4):455–8. doi:10.1111/j.1600-0501.2009.01836.x
13. Deeb GR, Allen RK, Hall VP, et al. How accurate are implant surgical guides produced with desktop stereolithographic 3-dimentional printers? J Oral Maxillofac Surg. 2017;75(12):2559.e1-2559.e8. doi:10.1016/j.joms.2017.08.001
14. Lal K, White GS, Morea DN, et al. Use of stereolithographic templates for surgical and prosthodontic implant planning and placement. Part I. The concept. J Prosthodont. 2006;15(1):51–8. doi:10.1111/j.1532-849X.2006.00069.x
ABOUT THE AUTHOR
Dr. O’Dowling graduated from University College Cork, Ireland, in 2006, where he was awarded the Noel Hayes Award for Oral Surgery and the British Undergraduate Society Award for Restorative Dentistry, and he was accepted as a member of the Student Clinicians of the American Dental Association for his project work on molar/incisor hypomineralisation. He has worke
d in private practice in Ireland, and in Queensland and Perth, Australia. During this time, he has continued to advance his knowledge in implant surgery and prosthetics and completed his MSc in Oral Implantology in 2018 from Goethe Dental School (Frankfurt, Germany). He is a Diplomate of both the International Congress of Oral Implantologists and the American Board of Oral Implantology/Implant Dentistry and a Fellow of the American Academy of Implant Dentistry. Dr. O’Dowling maintains a keen interest in all aspects of implantology, ranging from simple implant placement to advanced techniques such as partial extraction therapy, autogenous bone plates, and sinus augmentations. His current focus is the simplification of full-arch restorative protocols utilizing digital techniques and 3D printing. He can be reached at daveodowling83@gmail.com.
Disclosure: Dr. O’Dowling reports no disclosures.
