Session 1 Single Implant Guided Surgery — Module 23 Notes

Module 23: Single Implant Guided Surgery — Comprehensive Notes

• Focus: Guided surgery for single implant cases (crown and bridge), not full-arch implants. Covers when it’s appropriate, pros/cons, limitations, and the general workflow (in-office design/3D printing vs. lab-assisted workflows).
• Distinction from full-arch guided surgery: Single-implant guides are less technique-sensitive than full-arch guides but still require understanding of planning, fabrication, and execution.
• Overall aim: Understand rationale, workflow, and practical nuances to achieve predictable prosthetically driven implant placement.
• Audience consideration: Even with guides, the clinician must remain a critical thinker and not rely solely on guided systems.

Objectives

• Understand the rationale for guided surgery in single-implant cases.
• Identify pros and cons of guided surgery.
• Recognize limitations and potential pitfalls; guided surgery is not a panacea.
• Understand the workflow and the parts needed to bring guided surgery into a practice (in-house vs lab-assisted).
• Review examples and case reviews to illustrate concepts and outcomes.

Key Concepts and Rationale for Guided Surgery

• Analogy: Guided surgery is like GPS in a car. It helps navigate, avoid anatomy, and angle implants correctly, but it doesn’t drive the car by itself.
• Core benefits:
  • Increases accuracy in implant placement by translating digital plans to the mouth.
  • Helps plan emergence and prosthetic considerations (emergence profile, spacing, angulation).
  • Potential for streamlining restorative workflow (planning with end in mind).
• Brain-guided planning vs. guided execution:
  • Brain-guided: Plan and verify placement using CBCT, measurements, and wax-ups.
  • Guided execution: Use a physical guide to bring the plan to life in the mouth.
• Strategic considerations:
  • Start with the end in mind (prosthetic-driven planning).
  • Evaluate whether a guided approach is appropriate for the case (e.g., posterior angulation issues, need for precise emergence, etc.).
  • Consider grafting needs and bone support when planning implant position.

When and Why to Use Guided Surgery

• Reasons to use guided surgery:
  • Improved accuracy in implant placement.
  • Ability to translate a digital plan to the mouth with physical guides (sucker-down style guides that seat over existing teeth or flanges).
  • Potentially faster restorative timelines when used in streamlining workflows (e.g., same-day or same-visit planning with temporaries).
  • Ability to plan for prosthetic-oriented outcomes (paralleling contacts, proper emergence, screw-retained crowns to minimize cement-related issues).
• Practical workflow advantages:
  • In-office printing/milling reduces lab time and total treatment time.
  • Clear communication with the lab/assistants to ensure adequate guides and windows.
  • Ability to use premade temporaries or stents designed from the plan to improve chairside efficiency.
• Important caveat: Guided surgery requires proper planning and execution; misfits, poor seating, or unanticipated anatomy can still cause problems.

Limitations and Downsides

• Limitations:
  • Not perfect: There are always small deviations (a few percent or a few degrees).
  • Misfits or poor seating can lead to incorrect implant angulation or depth.
  • Not all cases are suitable (e.g., extreme undercuts, lack of stable teeth for guide seating, very narrow ridges).
• Downsides:
  • Reduced tactile feedback during drilling, which can affect bone quality assessment in real time.
  • Additional cost and time for guide design/production (though in-office options are increasingly affordable).
  • Potential for reduced visibility and irrigation challenges within a guide.
• Practical implications:
  • Ensure guide seating is fully seated before drilling (use windows to verify seating).
  • Do not rely solely on the guide in cases requiring manual adjustment or when anatomical concerns persist.
  • Plan for contingencies (e.g., a pilot guide, non-guided steps if seating fails).

The General Workflow (Overview)

• Components often required for guided surgery:
  • CT data (CBCT) for planning.
  • STL model of the soft tissue/digital model of the mouth.
  • Software to merge CBCT and STL and to plan the implant positions and guide design.
  • A 3D-printed or milled surgical guide.
• Common software and platforms:
  • Acteon AIS 3D (used in the course demonstrations).
  • Labs may use 3Shape, Exocad, Blue Sky Plan (free version exists; charges apply on export).
  • Other CBCT-integrated software (e.g., Sorona, Planmeca, Planmeka) with built-in guide functionality.
• Data flow (the “equation” for guided surgery):
  • CT data + STL model (soft tissue/digital mouth) + software merge → surgical guide output.
  • In practice: CBCT + digital impression/model + prosthetic plan (wax-up) → guide fabrication.
• Practical steps in a typical in-office workflow:
  1) Obtain CBCT and a digital model (or scan a physical model to produce an STL).
  2) Overlay the digital model with the CBCT data using identifiable hard-tissue markers (cusps, cusp tips, line angles).
  3) Create a wax-up or digital wax-up to define the intended tooth position and emergence.
  4) Plan implant positions relative to the planned crown (prosthetically driven planning).
  5) Create a plan that includes undercut mitigation and guide seating paths (block out undercuts).
  6) Generate the surgical guide with appropriate windows and seating surfaces.
  7) Print/mill the guide and verify fit; place any windows to confirm seating intraoperatively.
  8) Perform guided drilling and implant placement; use depth stops and sleeves for accuracy.
  9) Restore with appropriate prosthetic options (screw-retained vs cement-retained) based on plan.
  10) Postoperative assessment and timely restoration.

Prosthetically Driven Implant Planning: Magnitudes and Steps

• Magnitude 1: CT alone
  • Use CBCT rendering to get a rough arch location and measure distances (e.g., distance back from canines to osteotomy sites).
• Magnitude 2: Add a physical model (patient model)
  • Provides better visualization of ridge morphology, tissue thickness, and ridge width; improves planning accuracy before a guide is made.
• Magnitude 3: Wax-up
  • Overlay the wax-up onto the CBCT to align implant positions with planned prosthetic teeth; helps ensure implants align with anticipated crown positions.
• Magnitude 4: Guide creation
  • Create a physical guide that will hold drills in the planned positions and angulations; includes windows to verify seating.
• Illustration example (case): An overdenture case with pneumatized sinuses where a guide allowed placing implants back toward the sinuses while avoiding other anatomy and a preexisting broken mini-implant fixture.

Specific Case Illustration Highlights

• Example 1: Overdenture patient with pneumatized sinuses and a broken mini-implant at site 5
  • Plan: Get as far posteriorly as possible toward the sinuses while staying forward from ANS and avoiding the broken implant site.
  • Outcome: Guided placement allowed precise overlay of plan in the mouth; awareness of anatomy (inferior alveolar nerve, vessels, sinuses) and undercuts.
• Example 2: Posteriors with angulation issues
  • Comparative outcomes: Could use a screw-retained crown with a guide; alternatively a cement-retained crown requiring custom abutment due to angulation; guided approach can improve predictability.
• Example 3: Cleft palate patient with limited bone in anterior region
  • Guided planning can help place implants in an improved position; bone grafting may be needed; emergence considerations are critical.
• Example 4: GBR case (Kalina)
  • GBR on #10, then placement of narrow implants (e.g., 3.0 x 10.5 mm) due to root proximity; CBCT planning helps avoid buccal plate compromise.
• Example 5: Edentulous case with resorption (top left & bottom cases)
  • Digital wax-up overlay used to plan implants; CT-based planning helps avoid buccal bone perforation; guide seating verified with windows.
• Example 6: Beam hardening artifact explanation
  • Postoperative CT may appear to show no bone due to beam hardening; CT slices can misrepresent bone presence, but clinical evaluation and intraoperative findings confirm bone presence.
• Example 7: Premade temporaries and lab integration
  • Labs can design immediate temporaries or stents based on the guide plan, enabling chairside pickup and smoother provisional restoration.

The Mechanics of the Guided Kit and Drill Protocols (BioHorizons Example)

• Guided surgery kit components:
  • Sleeve color-coding corresponds to implant size (e.g., yellow, green, blue).
  • “Keys” or “spoons”: Narrow the interior diameter of the guide sleeve to match the drill diameter.
  • Drill lengths available: 17 mm, 21 mm, 24 mm, 28 mm (length depends on offset and implant selection).
  • Offsets: The critical measurement from the top of the sleeve to the bottom of the implant that determines drilling depth.
  • Offsets example: If offset = 22.5 mm and the key thickness = 1.5 mm, the drill length used = 24 mm (22.5 + 1.5 = 24).
• Depth stops and SP (stop position):
  • SP1, SP2, SP3, SP4 denote how deep the implant is driven through the guide before it bottoms out on the sleeve.
  • In practice, SP2 may be selected to achieve the desired depth when using a 24 mm drill with a 22.5 mm offset plus 1.5 mm key.
• Insertion driver and SPs:
  • Fully guided placement uses an insertion driver with four notches (SP1–SP4).
  • SP2 example: placing the implant deeper through the guide so the depth is corrected in the plan.
• Guided kit types:
  • Keyed kit: Uses separate keys to narrow the sleeve diameter; allows a full-length drill protocol with larger diameters.
  • Keyless kit: Used for shorter implants; the shank geometry itself engages the sleeve; reduces need for multiple drill lengths for short kits.
  • Short implants in BioHorizons: The tapered short kit uses a dedicated set of drills and sleeves; fewer length variations are needed.
• Other guide-related tools:
  • Tissue punches accompany guided kits to initiate osteotomy with minimal tissue trauma; punch slides through the sleeve.
  • Windows: Windows can be added to guide to visually confirm seating and alignment during drilling.
• Drill technique considerations:
  • Use slow, steady drilling with irrigation; pull the drill out slightly (2–3 mm) for irrigation cooling between passes.
  • Wider diameter drills used with caution; ensure adequate irrigation to avoid overheating and bone necrosis.
  • The cue: do not fully unscrew the drill while irrigation continues; avoid scraping or pushing bone chips away with uncontrolled torque.

Step-by-Step: From Planning to Guide to Implant Placement

• Step 1: Data collection
  • Acquire CBCT and obtain a digital or scanned soft-tissue model (STL).
  • Use an open bite or bite registration technique if needed to align skin markers and occlusion data.
• Step 2: Overlay and alignment
  • Import CBCT and STL into planning software; align using hard-tissue markers (cusps, cusp tips, cusp line angles).
  • Use “assisted” or best-fit functions to achieve precise overlay when possible.
  • Verify alignment by examining sagittal, axial, and coronal slices to ensure the STL envelope matches CBCT anatomy.
• Step 3: Prosthetic planning (wax-up)
  • Create a wax-up or digital wax-up for the intended tooth positions; this guides implant positions relative to emergence and occlusion.
  • Consider occlusal scheme, crossbite, super-eruption, and adjacent tooth relationships.
• Step 4: Magnitude progression
  • Combine CT data with model data and wax-up to finalize the implant plan (position, angulation, emergence path).
• Step 5: Guide design and seatability
  • Create a guide that spans from adjacent stable teeth and includes windows to confirm seating.
  • Block out undercuts to ensure the guide seats properly (undercuts in maxilla anterior or premolar regions can cause seating issues).
• Step 6: Guide fabrication
  • Export STL from planning software; print or mill guide (in-office or lab-provided).
  • Place sleeves in the guide prior to curing in resin; ensure sleeves sit flush with guide.
• Step 7: Surgical procedure
  • Verify guide seating intraoperatively using windows and tissue handling; reflect tissue to expose implant site while preserving flap design.
  • Drill with proper drill sequence and irrigation; use depth stops and SP settings to achieve planned depth.
  • Place implant to planned depth, ideally maintaining emergence and parallelism with adjacent teeth.
• Step 8: Verification and restoration
  • Confirm implant position with ISQ readings (e.g., ISQ ~ 78–79 indicating good primary stability).
  • Place healing abutment or temporary restoration according to plan; in many cases, cement-retained restorations are planned to minimize surface complications, though screw-retained options can be preferable for precise retention.
  • Consider provisional adjustments or staging if bone grafting or GBR was performed.

Practical Considerations: In-Office vs Lab, and Selection of Tools

• In-office milling/printing vs lab fabrication:
  • In-office milling/printing reduces wait times and can improve case turnaround, enabling same-day temporaries in some cases.
  • Labs provide expertise in wax-ups, guided-stent design, and fabrication; important if you rely on a lab’s workflow for precise windows and anchor teeth.
• Software considerations:
  • Acteon AIS 3D, Blue Sky Plan (free with export charges), 3Shape, Exocad, Planmeca/Planmeka, and other CBCT-integrated tools offer guide design features.
  • Each software has different workflows for overlay alignment, wax-up import, and guide export.
• Model and STL considerations:
  • You need a robust soft-tissue model (STL) and a CBCT dataset; you’ll often use a model scan or intraoral digital impression to create STL.
  • For occlusion matching, you may need bite registration data or open bite references to ensure accurate overlay.

Drilling Techniques and Execution Details

• Drilling steps (guided):
  • Pilot drilling with a 2.0 mm diameter drill (2x) to start the osteotomy; maintain irrigation.
  • Widen osteotomy with subsequent drills (e.g., 2.0x17, 2.0x21, 2.0x24, etc.) depending on depth needed and bone quality.
  • Final drill aligned with plan for dense bone: use a final osteotomy drill for optimal diameter while preserving bone.
  • If posterior dense bone or implant length constraints exist, additional steps (e.g., using osteotomes) may be used to preserve buccal plate (densification technique).
• Depth control:
  • Drills have depth stops; the depth stop must be aligned with the stop position on the sleeve to ensure accurate final depth.
  • The SP (stop position) selection and the use of a depth stop ensure that the implant penetrates to the intended depth through the guide.
• Tissue considerations during drilling:
  • Tissue punches may be used to access bone while the guide holds tissue back, reducing flap trauma.
  • Avoid overheating; ensure adequate irrigation and gentle drilling technique to protect bone vitality.

Postoperative Considerations and Artifacts

• Postoperative imaging:
  • Beam hardening can create apparent gaps or absence of bone on CT, particularly around implants; correlate with clinical findings.
  • Postoperative CT may show less radiopaque bone due to artifact; use clinical assessment and intraoperative feedback to confirm stability and position.
• Healing and restoration plans:
  • For some cases, primary closure and healing abutment placement are planned; future uncovering or soft tissue grafting may be scheduled.
  • Consider provisional restorations to guide soft tissue contours and emergence profile.
• Complications and salvage:
  • If guide seating fails or misalignment occurs due to poor seating or patient factors (limited mouth opening, severe undercuts), you may need to switch to non-guided placement.
  • Guided systems can complicate protocols if the guide is not properly seated or if dramatic bone undercuts exist.
  • Be aware of potential for cantilevered or misaligned prosthetics if planning assumptions were off; contingency plans with the lab are essential.

Practical Tips and Takeaways

• Always start with the end in mind: plan the crown/bridge outcome and ensure implant positions support that outcome.
• Use wax-ups to anchor implant planning to the final prosthesis; overlay wax-ups onto CBCT data for accurate alignment.
• Ensure robust seating of the guide: plan for windows and seating checks; verify with multiple views (anterior/posterior, distal, etc.).
• Block out undercuts to ensure the guide seats correctly over the arch.
• Be mindful of anatomy: nerves, vessels, sinuses, nasal canal, and undercuts; plan to avoid critical structures.
• Understand your kit: know the meaning of SP positions, the offset, the sleeve diameter, and the drill lengths; know how to select the correct drill sequence for the planned implant and bone density.
• Manage expectations: guided surgery is not perfect; anticipate small deviations and have a plan for contingencies.
• Ethical/practical implications:
  • Ensure patient safety by not over-reliance on guides where anatomy or seating is uncertain.
  • Communicate limitations and alternatives clearly to patients.

Formulas, Numbers, and Quantitative References (LaTeX)

• Emergence guidance:
  • Emergence from crest: $3\text{ mm} \leq \text{emergence depth} \leq 4\text{ mm}$ (apical to the free gingival margin).
• Plan-to-guide offset example:
  • Offset example: $\text{offset} = 22.5\ \text{mm}$
  • Key thickness: $\text{key thickness} = 1.5\ \text{mm}$
  • Drill length: $L = \text{offset} + \text{key thickness} = 22.5 + 1.5 = 24\ \text{mm}$
• Available drill lengths (example set): $L \in {17,\ 21,\ 24,\ 28}\ \text{mm}$
• Implant example dimensions (from kit): $\text{implant diameter} = 4.2\ \text{mm}, \ \text{implant length} = 10.5\ \text{mm}$
• Guided kit depth stops: SP positions (SP1, SP2, SP3, SP4) determine final depth through the sleeve; final position is when the implant bottoms on the sleeve.
• ISQ stability readings (illustrative): $ISQ \approx 78\text{--}79$ (high stability implies potential for immediate or early loading strategies).
• Drill diameters and sequences (representative): 2.0 mm diameter drills with various lengths (e.g., 17, 21, 24, 28 mm); depth stops and sleeves control vertical depth.

Summary

• Single-implant guided surgery can improve accuracy and streamline prosthetic-driven implant placement when used with proper planning and execution.
• The workflow integrates CBCT data, STL models, wax-ups, and guide fabrication to translate a digital plan into a precise surgical guide.
• A thorough understanding of the equipment (sleeves, keys, SP stops, depth stops, and drills) and a disciplined drilling technique with irrigation are essential for success.
• Practical case examples illustrate how guided surgery supports complex scenarios ( GBR, narrow ridges, angled implants, and interim restorations) while highlighting potential limitations and the need for contingency planning.
• A successful guided approach requires collaboration with labs or in-house capabilities, clear communication of plans and requirements, and a realistic appraisal of when guided surgery is most advantageous.

End Note

• This module includes quizzes (target: 7/10 or better) and emphasizes reviewing the content and rewatching as needed. The subsequent module will discuss full-arch guided surgery and its differences from single-implant guides.