With respect to treatment planning for tooth replacement using implants, what would you consider to be the most important things to consider?
There are several important factors in treatment planning patients for implant replacement. It starts with a thorough diagnosis of the existing conditions. A complete medical history is taken to assess the patient’s health and evaluate any impact this may have on implant therapy. This may include conditions that affect dental implant healing, such as diabetes, immunosuppressive diseases, irradiation of the jaws, and smoking. Also, some drugs have been found to negatively influence bone healing, including bisphosphonates (osteoporosis, cancer), selective serotonin reuptake inhibitors (depression), proton pump inhibitors (acid reflux), and chemotherapy (cancer).
The radiographic examination should include periapical films of the remaining dentition and cone beam computed tomography (CBCT) (CS9300 [Carestream Dental]; Green CT 2 [Vatech America]) of the edentulous areas and/or sites planned for removal of teeth.
|Figure 1. Periapical radiolucency, revealing palatal root resorption.|
|Figure 2a. The lesion destroyed the palatal cortical plate.||Figure 2b. The axial view further confirms the palatal defect.|
The clinical examination should include an oral pathology screening, a TMJ and occlusal evaluation, a periodontal assessment, and the evaluation of any teeth for decay and the integrity of existing restorations. Mounted study casts are useful for more complex cases that require comprehensive planning and diagnostic wax-ups. These study casts can be digitized using a laboratory scanner (D2000 [3Shape]; T500 [Medit]). The stereolithography (STL) file of the model can be integrated with the CBCT scan for virtual planning of the implant surgery. Currently, we more often use an intraoral scan (TRIOS Intraoral Scanner [3Shape]; i500 [Medit]) of the dentition to create the STL file directly. The laboratory team can then perform a virtual digital wax-up to provide the patient, clinician, and themselves with a “blueprint” of the desired treatment outcome.
Treatment that will involve aesthetics should include full facial and intraoral photos. The lip position at rest and in a full smile are critical to planning for ideal dental aesthetics. Dynamic facial movements can be best captured with videography. Facially generated treatment planning helps ensure that implant replacement will integrate properly into the patient’s overall appearance. Digital technology allows us to utilize preoperative photos and/or intraoral scans with computer planning software (DSD Digital Smile Design) to virtually design the smile. It can also be used to print mock-up prototypes for chairside try-in prior to treatment.
Once the clinician has collected all the pertinent history and diagnostic information, the planning can begin. It is imperative to determine the desired outcome and to begin with the end result desired in mind. Our goal as dentists is to restore our patients back to proper contour, comfort, function, aesthetics, and health. However, it is important to determine the patient’s chief complaint and understand his or her expectations of implant replacement. A better smile? Improved chewing function? Shortest treatment? Lowest cost? The goal may be different for the replacement of anterior teeth in the aesthetic zone vs posterior partial edentulism. A prognosis is determined for the remaining dentition to assess the span for replacement. Implant dentistry is a prosthetically driven discipline; the planned prosthesis drives all of our clinical decisions. Backward planning requires that we first determine the type of prosthesis: fixed or removable? Cement- or screw-retained? Individual attachments or bar-overdenture? Individual crowns or a fixed partial denture (bridge)? Once we have determined the type of prosthesis, we must evaluate the available bone for implant placement in the desired locations for prosthetic support. This will determine if bone augmentation is needed for site development or if alternative locations can be considered.
|Figure 3a. A 3-D volumetric rendering of the mandible with several teeth missing.|
|Figure 3b. The merging of an optical scan with the CBCT dataset.||Figure 3c. Using “selective transparency” to visualize the nerve, implants, and virtual teeth.|
|Figure 4a. A realistic implant and abutment (yellow) projecting through the body of the virtual tooth helps accurate planning.||Figure 4b. Advanced “clipping” functionality can virtually slice through the various layers of the 3-D data.|
In some cases, we may consider different approaches, such as short, narrow, or tilted implants, to avoid the need for bone augmentation. In other cases, the removal of teeth may be preferred, especially when their long-term prognosis is in question. Once the clinician has determined the number, type, and location of the implants, a definitive plan for execution can be developed. It is often helpful to sequence the treatment plan into phases for better patient communication.
Another important aspect in planning for implant replacement is to determine the type of provisional replacement of missing teeth during the treatment phases. Removable options may include an acrylic partial or full denture, an Essix retainer, or an overlay prosthesis (Snap-On Smile [DenMat]). If a patient desires a non-removable provisional replacement, they may consider a bonded bridge, a temporary fixed bridge, or an immediate-load implant prosthesis. In many cases, a fixed provisional prosthesis is preferred as it can eliminate undesirable loading of healing bone grafts and implants. It may also help guide healing of the soft tissue and aid the clinician in the design of the final prosthesis.
What are the latest technologies that are proving to be the most beneficial to treatment planning implants?
There are several technologies that can improve the planning and delivery of dental implant treatment. As previously discussed, CBCT is essential for imaging of the jaws for possible implant sites. CBCT provides the clinician with a true 3-D assessment of the patient’s existing anatomical presentation. The scanning software allows visualization of the quantity, quality, and volume of bone available for implant placement as well as vital anatomic structures, such as the mandibular canal or maxillary sinus. It also is helpful in evaluating deficient ridges that will require bone-augmentation procedures. The clinician can select the optimal method of site development, such as ridge expansion, guided bone regeneration, or block grafting.
Figure 1 reveals a radiolucent area surrounding a maxillary bicuspid (green arrows), with palatal root resorption and significant bone loss in the cross-sectional slice. This could not have been diagnosed with a 2-D periapical radiograph. This finding on the scan may result in altering the proposed treatment plan from an extraction and immediate implant placement to an extraction and bone grafting with a membrane for delayed implantation. Figure 2 depicts a similar presentation in a maxillary lateral incisor when the patient became symptomatic one year after root canal therapy. The periapical radiograph seemed to indicate that the periapical radiolucency had diminished; however, the cross-sectional CBCT image told a different story: The periapical lesion had extended through the palatal cortical bone, as clearly seen in Figure 2a, as well as in the axial view in Figure 2b.
|Figures 5a and 5b. The use of manufacturer-specific SmartPegs (Osstell) provide objective measures of implant stability using resonance frequency analysis digital technology with implant stability quotient values.|
The CBCT scan, combined with interactive implant planning software (Simplant [Dentsply Sirona]; BlueSky Plan [BlueSkyBio]; R2Gate [MegaGen Implants UK]), is essential for successful treatment planning. It is critical to include prosthetic information in this analysis. The diagnostic wax-up of the planned prosthetic tooth positions can be made into a scanning appliance. The patient can wear the radiopaque appliance during the CBCT scan (or radiopaque fiducial markers can be attached to the appliance). A second and separate scan is then taken of the diagnostic appliance. This dual-scan approach, along with the use of planning software, allows the clinician to determine the relationship between the desired tooth position and the underlying bone. In certain other cases, such as a missing single tooth or several adjacent teeth, applications in the planning software permit the lab team or clinician to use a library of virtual teeth that can be digitally modified to fill the space.
Figure 3a shows a volumetric rendering of a mandible missing several posterior teeth. The ability to combine anatomic and prosthetic data sets has dramatically increased our diagnostic and planning accuracy. An intraoral optical scan, or digitization of a stone cast merged with the CBCT scan data, is seen in Figure 3b. The digitization of the existing teeth provided improved surface accuracy for the precise arrangement of virtual teeth (white) and the positioning of 2 simulated dental implants.
Dr. Ganz has coined the term selective transparency to describe the ability of the software to differentiate objects, in terms of opacity, to help visualize the relationship between the nerve, the virtual and actual teeth, and the position of the implants (Figure 3c). Advances in software applications allow us to virtually “slice” through the optically scanned model (pink) and the bone to finalize the ideal positioning of the implant(s) (Figure 4). Once the diagnosis and treatment planning phase has been completed, the information can then be shared with the patient, the dental laboratory technician, and all members of the implant team. At this point, the surgery can be performed freehand using a conventional surgical template, a static computer-generated surgical guide (Simplant; BlueSky Plan; R2Gate), or dynamic navigation (X-Guide [X-NAV Technologies]).
After a dental implant has been placed, how can we determine its stability within the bone?
Insertion torque measures the friction of the implant as it goes into the osteotomy at that moment in time. Without a calibrated torque wrench, most clinicians can only provide a subjective value of rotational stability. A more objective measurement comes from an accepted technology known as “resonance frequency analysis” (RFA) (Osstell IDx [Osstell]; Mega ISQ IDS [MegaGen Implants UK]), which provides a value in terms of the implant stability quotient (ISQ). This provides a baseline value at the time of implant insertion, allowing for greater confidence in knowing whether an implant can be immediately loaded, or if it is better to wait and use a delayed loading protocol. The implant can be measured again at 8 to 12 weeks, as this technology is a nondestructive tool that can be reliably repeated over time to monitor the progress of osseointegration. A manufacturer-specific SmartPeg (Osstell), once secured to the implant, objectively measures implant stability with the RFA device. This provides an ISQ value that can be entered in the patient’s chart, recording the level of stability each time a measurement is taken (Figure 5). The use of RFA is supported by almost 900 articles in the literature.
Has the high success rate found with dental implants changed your treatment planning strategies?
Dental implant treatment has become predictable and is often the preferred approach for the replacement of teeth. There is no question that dental implants can reduce bone loss over time in patients wearing a denture. In fact, the mandibular 2-implant supported overdenture has become the first treatment of choice in the edentulous patient. Studies have also shown that the longevity of a dental implant crown is better than a 3-unit fixed partial denture (bridge) on natural teeth. An implant crown also improves the prognosis of the adjacent teeth compared to a bridge. This is especially true in the caries-susceptible patient. Many prescription medications cause xerostomia, making implant-supported prosthetic options the preferred choices over conventional crowns and bridges. In selected teeth, where the endodontic or periodontal therapy has failed, or the prognosis is questionable, implant replacement is often the preferred option. There may be other times when maintaining a compromised tooth can offer a potential advantage, as long as its maintenance does not compromise the site for future implant placement. Postponing intervention may offer other improved implant solutions in the future.
Improvements in the predictability of bone regeneration have also impacted treatment planning. In the past, many patients were told that they were not candidates for implant therapy due to poor bone volume. Now, in most cases, experienced surgeons can augment the deficient ridge to allow implant placement. As an alternative, short implants may be used to avoid the need for vertical bone augmentation to place longer implants. Growing evidence is showing that this may be the preferred choice since it reduces costs, treatment length, and morbidity.
Many patients present with some missing teeth and compromised remaining teeth. Do we save questionable teeth, or should we include their replacement into the final prosthesis? In patients with a high caries index, the choice is often better to extract the teeth. In partially edentulous patients with chronic periodontitis, the decision may be more complex. The clinician should at least consider the option of removing compromised teeth for a complete implant prosthesis. This can often simplify the plan, expedite treatment, and reduce costs when compared to addressing the future loss of teeth. It can also provide the option of an immediate implant-supported provisional prosthesis. However, this irrevocable decision should be made on a case-by-case basis with no guarantee that the implant option will offer the patient life-long results or completely avoid any future dental problems.
Although high implant success rates are often reported in the literature, both clinicians and prospective patients should be cautioned that these results do not always mirror the outcomes seen in clinical practice. It is important that dentists recognize that some implant cases are more complex and require a healthy and committed patient as well as a clinician with advanced education, training, and skills to achieve a successful long-term result.
Dr. Ganz received his specialty certificate in Maxillofacial Prosthetics/Prosthodontics, which led to a focus on the surgical and restorative phases of implant dentistry and to contributing to 15 implant-related textbooks. He is a Fellow of the Academy of Osseointegration, a Diplomate of the International Congress of Oral Implantologists, president of the Digital Dentistry Society, and co-director of Advanced Implant Education. Dr. Ganz is on the faculty of the Rutgers School of Dental Medicine and maintains a private practice in Fort Lee, NJ. He can be reached via email at email@example.com.
Disclosure: Dr. Ganz reports no disclosures.
Dr. Misch practices as a dual specialist in Sarasota, Fla. He has postgraduate certificates in prosthodontics, oral implantology, and oral and maxillofacial surgery, and is board certified by the American Board of Oral and Maxillofacial Surgery. He is a clinical associate professor at the University of Florida, the University of Alabama, and the University of Michigan in the departments of periodontics and prosthodontics. Dr. Misch is an assistant editor of Implant Dentistry and is on the editorial boards of several other distinguished dental journals. He can be reached via email at firstname.lastname@example.org.
Disclosure: Dr. Misch is a consultant for BioHorizons, Dentsply Sirona, Orapharma, and Geislich Biomaterials.