Digital Implant Planning and Surgical Guides: Tools for Clinical Success

With pioneering dental practitioners having learned from mistakes and failures in the past, digital planning and guided implant surgery are no longer luxury items for a chosen few. They have become necessities for successful implant dentistry and are now widely available. The rapid evolution of digital dentistry applications such as digital planning, designing, and manufacturing and the ease of access to information and training have helped clinicians adopt these technologies and applications into their daily practice. This "technological race" has caused manufacturers to develop a wide range of hardware and software products in a relatively short time, leading to lower costs and greater accessibility. In addition, most manufacturers have changed their branding and privacy policies, making software and outcome files more compatible and interchangeable among different brands. The integration of systems, including digital radiographs, CBCT, extra- and intraoral scanners, design software, and the resulting files (eg, digital wax-ups), has become commonplace for interdisciplinary treatment planning and prosthetically driven implant placement.

A pillar of digital implant planning and prosthetically driven implant placement is the acquisition of intraoral 3D images, ensuring that all anatomical structures are clearly captured in both the maxilla and mandible. This acquisition can be made with either extraoral laboratory-based scanners from analog impressions or physical models, or IOS. IOS have become popular because they are easy to use, allow rescanning of areas that may have faults without having to remake the entire impression, and provide a significantly more comfortable patient experience.^1,2 In addition, the scan files can be stored digitally and are easily accessible for any future use.

While there may be slight differences among the many brands of IOS systems, studies indicate that the accuracy and trueness of the commonly available IOS are within acceptable limits for clinical use.^3,4 Among the factors that influence scan results are the need for anti-reflective powder coating with some systems and proper following of the recommended scan pattern, which can vary among systems.⁵

The intraoral scans are used to digitally plan and design the restorations, which guide the final implant position. A variety of prosthetic restoration design software is available today; most software requires a license purchase, however some software is license-free.

Once the digital wax-up is complete, the design file, usually in STL format, is integrated into the information from the CBCT for surgical planning. The digital wax-up files provide a significant amount of additional information and can be used to design other digital guides for additional treatment steps, such as crown lengthening, preparation design, orthodontics, mock-ups, and provisional and definitive restorations.

CBCT is paramount for implant planning.⁶ It facilitates exact determination of anatomical structures and with that, proper implant selection and 3D implant placement. Digital imaging and communications in medicine (DICOM) files are obtained from the CBCT. These are needed for successful integration with the IOS files. A software is needed with the capacity to integrate and align both the DICOM and STL files; example software systems include exoplan (Exocad), Implant Studio (3Shape), Simplant (Dentsply Sirona), and NobelClinician (Nobel Biocare). The implant planning software should be able to design tooth- or tissue-supported guides and not be limited to bone-supported guides. Other considerations for choosing an implant planning software include cost, available implant libraries, integration with IOS, additional applications besides implant planning (eg, bone reduction), and the ability to modify implant and drill parameters.⁷

The integration of STL and DICOM files enables the determination of various parameters, such as the panoramic curve, and facilitates selection of the implants, which will determine the sleeve size (length and diameter) and height (distance between sleeve and implant platform) of the surgical implant placement guide. In the partially edentulous jaw, at least two teeth are recommended to support and stabilize the surgical guide. The guide will be fabricated for export, and the final implant position can be imported back into the dental system software to facilitate fabrication of provisional prostheses or custom healing abutments. The design files can be saved for definitive restoration fabrication in the future.

There are currently two options to fabricate digitally designed surgical guides: additive manufacturing such as 3D printing and subtractive machining such as milling. 3D printing is popular because of a wide variety of available printers and materials and their relatively low cost. Different materials have different printing parameters, which can affect precision and mechanical properties of the surgical guides. It is, therefore, important to closely follow manufacturers' recommendations for 3D printing and post-processing parameters.⁸

After fabrication of the surgical guide, implant-specific sleeves are incorporated into the guide, although sleeveless guided surgery systems are also available. Before the surgical procedure itself, proper fit and seating of the surgical guide must be verified. During the procedure, the drilling sequence specific for the selected implant system must be followed exactly. Note that guide sleeve kits are specific to each implant system; therefore, familiarity with the selected implant system and its specific drill sequence is essential.

A major advantage of digital dentistry is the ease of communicating with colleagues and laboratories. Many clinicians collaborate with a digital planning or smile design center to delegate some of the steps of the digital workflow to an outside entity.

(For a step-by-step protocol of the digital workflow, see below.)

Prosthetically driven implant placement in terms of ideal position, angulation, and depth is nearly impossible without guided surgery. Even with surgical guides, the average deviation of the final implant position compared to the planned one can be more than 1 mm.⁹ The main reasons for this distortion are inaccuracies during the intraoral scan and in the CBCT image. It is important to check the STL file from the IOS and make necessary corrections when inaccuracies are detected. The same applies to the CBCT, where, for example, metal-related artifacts could lead to excessive noise and less accurate stitching. Removing and provisionalizing failing metal restorations before making the CBCT may reduce noise and lead to a cleaner stitching between the different image layers. Closely following proper protocols for 3D printing and post-processing can further reduce inaccuracies.

Julian Conejo, DDS, MSc
Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

Pablo J. Atria, DDS, MSc
Department of Biomaterials, Universidad de Los Andes, Santiago, Chile; Grossman School of Medicine, New York University, New York, New York

Daniel Schweitzer, DDS
Private Practice in Radiology, Santiago, Chile

Markus B. Blatz, DMD, PhD
Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

Step-by-Step Protocol

1. Make IOS (upper and lower jaw, buccal views) and export as STL file.

2. Create digital wax-up with ideal morphology of missing teeth, export as STL file.

3. Make CBCT(avoid patient movement and extensive metal restorations), export as DICOM file.

4. Merge all digital files inside implant planning software and confirm quality of correlation.

5. Select implant from library and virtually place in ideal relation to digital wax-up. Determine if bone or soft-tissue grafts are needed.

6. Assure compatibility between surgical kit, implant system, and sleeves/holes in surgical guide before manufacturing.

7. Mill or print provisional restoration from the digital wax-up. A custom healing abutment can be fabricated to shape an ideal emergence profile.