In many of my presentations, I often state that we are the architects and engineers of the oral cavity. This has been a common theme throughout my career on the podium and in many publications regarding dental implant reconstruction. Let’s put this concept in perspective. If you were building a new dental office and found a building with lots of space within 4 walls, would you start moving equipment into the space, running wires and pipes, hanging lights, dividing the space with new walls and doors, and so on without a plan? Of course, you would have an architect and an engineer review the necessary specs to create a blueprint that guides the office build-out with a full understanding of where the lights, inner walls, doors, windows, and everything else should go. This blueprint is, in fact, required in most, if not all, municipalities. So why do many dentists feel that, when patients present with the need for dental reconstruction, a similar plan is not essential to achieve successful outcomes? If we are truly the architects and engineers of the oral cavity, then it is absolutely necessary to create a blueprint to guide the process!
GUIDELINES FOR IMPLANT PLACEMENT
The dental literature is replete with guidelines for implant placement. Many of these protocols were based solely on 2-D panoramic or periapical radiology. How close should an implant be placed next to a natural tooth? The rule of thumb seems to be 1.5 to 2.0 mm. Where are we measuring from, and how are we making this assessment? How close should an implant be placed next to another implant? How do we measure these distances before the implant is placed? Can we state, with certainty, that a periapical or panoramic radiograph can provide us with an accurate assessment about the reality of the anatomy for each individual patient presentation, or is there something better that can provide this information more accurately?
Can we, as clinicians, actually agree where an implant should be placed within a potential receptor site? As I previously stated as a personal philosophy of mine, the “goal of implant dentistry is not the implant, it’s the tooth that we replace.” This means that patients are not coming to us for implants; they are coming to us to replace what is missing. Besides, what is missing has not changed—it is still the clinical crown, root, bone, and surrounding soft tissue—but our patients just really want teeth! We have both the technologies and the ability to replace most all of these missing structures through guided soft- and hard-tissue regeneration and grafting, and when it is beyond biology to replicate nature, we can often use the expertise of the dental laboratory technician to simulate missing structures with prosthetic solutions. However, does technology allow clinicians to better appreciate both surgical and prosthetic outcomes before the scalpel touches the patient?
The desired morphology, function, and aesthetics of the proposed tooth replacement should ideally dictate the position of the implant. The implant must also be sufficiently fixated within the alveolus to limit micromovement and surrounded with adequate bone volume to achieve osseointegration. In my opinion, sufficient bone volume is essential for long-term functional success. Therefore, we need an objective measurement of implant stability to provide clinicians with confidence to know when to load an implant with either a transitional or definite restoration. One such digital tool based on resonance frequency analysis—that has been validated by more than 800 scientific publications—provides an implant stability quotient (ISQ) at the time of placement, at uncovering, at the time of loading, or to monitor implant’s continually osseointegration.
Implant and Abutment Design Considerations
The design of the implant and the abutment connection plays a significant role in the vertical positioning of the implant as it relates to the crestal height of the bone and soft tissue. Certain implants are designed to be placed subcrestal, while others are designed to be placed at, or above, the alveolar crest. The variety of stock or custom abutments produced and sold by implant manufacturers must match the surgical protocol and emergence profile to achieve soft-tissue maturation and ideal aesthetic result. If a stock abutment cannot deliver the desired result, patient-specific CAD/CAM abutments can be utilized. Today, there seems to be a paradigm shift back to screw-retained over cement-retained restorations, especially for full-arch CAD/CAM monolithic or hybrid implant-supported prostheses. Is it possible to predict which abutment or restorative option (cement- or screw-retained) could be used for a given case in advance of the surgical intervention?
Comparing Different Imaging Modalities
The 2-D periapical or panoramic imaging modalities provide basic information regarding the region of interest, but are equally diagnostic compared to a 3-D analysis from a cone beam computed tomography (CBCT) scan. Often the trajectory of the clinical crown and roots within the alveolus occur at an angle—a position that is difficult to realize without a cross-sectional slice from a CBCT scan. An implant placed within an immediate extraction socket may therefore be compromised, perforating either the buccal or lingual cortical bone plates, or resulting in an unfavorable restorative position. Hard-tissue grafting or guided bone regeneration may provide the solution when there is insufficient bone to place an implant, to repair a defect, or to support the soft-tissue contour. Can we do better in predicting the bone volume necessary to facilitate implant placement and to avoid surgical and restorative complications?
In the posterior edentate maxillary arch, there is often insufficient bone height for implant placement. In these circumstances, a sinus augmentation procedure may be contemplated. The maxillary sinus may become pneumatized, with thin walls and severely resorbed alveolar anatomy, which is difficult to define with 2-D radiography. We generally have 2 methods when considering the posterior maxilla: (1) the lateral wall access or (2) transcrestal access with immediate implant placement. The anatomical reality reveals that the maxillary sinus can be narrow or wide, contains intraosseous vessels, may contain septa of different configurations, or may contain simple or serious pathology that must be resolved prior to treatment. When approaching a lateral wall fenestration, how does a clinician decide where to enter the sinus, and choose which instrumentation is best to utilize for this surgical intervention? When a transcrestal approach is indicated, how does the clinician understand how to stabilize the proposed implant in terms of available bone height, choose the proper diameter and length of implant, or thread design based upon the quality of the crestal bone? There is one more necessary point to be considered: how much bone do we need to complete the task—1.0 cc, 2.0 cc, 3.5 cc, or more? Would it be desirable to have the patient’s actual maxilla in hand to assess and plan the surgical intervention if possible with an accurate 3-D printed model?
All of the examples mentioned in this Viewpoint are important when considering the evolution of digital workflow as it exists today and its state-of-the-art elements. In my opinion, the proliferation and broad acceptance of CBCT has provided clinicians with the most important diagnostic tool currently available, and sets the foundation for everything that happens next. However, it should be noted that, as with any technology, it must be utilized correctly. Clinicians need to be educated on how to diagnose, followed by a treatment plan, and managing the entire digital workflow through to the final restoration. It is definitely possible to plan an implant placement for either cement or screw retention and export this position to CAD/CAM software to produce custom abutments or prostheses in advance of the surgical intervention.
Advances in Rapid Prototyping Technologies
With current advancements in rapid prototyping available through low-cost 3-D printers, highly accurate models can be generated of the patient’s jaw anatomy, or for the production of surgical guides, aiding in both the diagnostic process as well as lowering the barriers to guided surgery applications. Having a 3-D printed maxilla prior to the procedure helps us to capture the entire sinus volume, septa, thickness of the lateral walls, and the dimensions of the alveolar crest in order to plan grafting intervention. A sinus lift guide can be accurately designed and positioned for the lateral access, or for simultaneous implant placement, to aid the clinician in understanding how much graft volume is required to support the implants for long-term survival. We can also print a mandible to design a harvest guide to specify the ramus donor block graft with the required dimensions and to avoid proximity to the nerve.
CLOSING COMMENTS
It can be stated with certainty that CBCT and interactive treatment-planning software can supply us with an accurate assessment of the reality of anatomy for each patient presentation. Essential vital anatomy can be visualized, taking the guesswork out of the process to improve outcomes while reducing complications. Technology, if used properly, empowers clinicians to better appreciate both surgical and prosthetic outcomes, improve communication to all members of the implant team, and provide the blueprint to confidently execute the plan to the benefit of the patient.
Dr. Ganz graduated from the University of Medicine and Dentistry of New Jersey Dental School (now Rutgers School of Dental Medicine) and then completed a 3-year specialty program in maxillofacial prosthetics at MD Anderson Cancer Center in Houston. He is considered one of the world’s leading experts in the field of computer utilization for diagnostic, graphical, and treatment-planning applications in dentistry. He can be reached via email at drganz@drganz.com.
Disclosure: Dr. Ganz is co-director of the Advanced Implant Education and director of the Ganz Institute of Applied 3-D Implant Reconstruction.
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