CBCT analysis is a tool that has made the practicing dental implant surgeon more proficient and efficient, whether he/she be a general dentist or specialist. As the cost of the equipment has come down, more and more practitioners are incorporating the CBCT into their private offices. For those who prefer not to own it, there are plenty of places to refer your patient for this incredible diagnostic evaluation in three dimensions, including mobile units that will actually come to your office. Here we will discuss the use of CBCT diagnosis, treatment planning and its use for accurate surgical placement of maxillary posterior dental implants on a 53 yearold male with no medical contraindications. His severe class 3 malocclusion has created functional concerns and collapsing on his arches. (Figure 2) Along with the esthetic compromises, he would like an improved quality of life and ability to chew better.
Our modern endosseous dental implants have been placed clinically for over 35 years now. However, without proper evaluation of the available hard tissue, errors can be made in our surgical treatment. Figure 1 illustrates the improper angulation placement of a posterior mandibular dental implant on a non-related clinical case. This could have been prevented with CBCT diagnosis. There are also times when the CBCT analysis determines that there is inadequate bone for placement, where a referral may be appropriate.
Our patients are aware of their dental insufficiencies. As dental professionals, we must keep up with modern techniques and the innovative materials available to us. These tools help us to educate and instruct the patient as to the benefits and risks or our procedures. Being able to visualize the final case prior to any surgical intervention is an art that comes with years of experience. However, with the advent of CBCT analysis and digital design, we have become very equal in our diagnostic abilities. Proper planning of cases we choose to do in our office is the most critical aspect of today’s implant surgical protocol. A “tooth up,” or “tooth down” approach allows for design of the prosthetics prior to any surgical intervention. Taking this method of treatment creates a situation where each final prosthesis is ideal, eliminating the chance of improper or inadequate placement. Here 3DDX (3D Diagnostics, Boston, MA) helped to determine crown formation and then implant angulation and depth in the available hard tissue.
Diagnostic treatment planning is only limited by the viable anatomy presented. Large maxillary sinuses may inhibit placement of dental implants in the posterior maxilla without more involved surgical intervention. The advent of cone beam computed tomography diagnosis has aided the practitioner in determining the type, number, position and angulation of potential implants.
A pre-operative CBCT scan, using the PaX i3D Green Machine Imaging System (Vatech America Inc., Fort Lee, NJ) shows the axial, sagittal and coronal planes. The axial plane is the plane parallel to the ground, thus dividing the face from top to bottom. The sagittal plane is one perpendicular to the ground, diving the face from right to left and is most useful to evaluate the amount of available bone height and width facial to palatal. Finally, the coronal plane, shows the plane perpendicular to the ground, dividing the face from front to back. When considering dental implant placement to replace missing maxillary bicuspids and molars several options are considered depending on the actual amount of bone available for implant placement. Here a relatively invasive Caldwell Luc procedure was created. A window was made on the facial aspect of the missing teeth and the sinus filled with allograft material (1) After approximately 6 months of healing, the graft converts to bone allowing for more acceptable implant placement. The Schneiderian membrane was elevated without complication. (2,3)
Figure 3 indicates CBCT analysis showing the lack of adequate hard tissue in the posterior maxilla, as the floor of the sinus fell following extraction of the posterior teeth years ago. We understand that as teeth are lost, bone will shrink both palatally and apically. But the tooth roots also acted like tent poles holding up a circus tent. Once those “tent poles” were removed the sinus floor collapses resulting in a large maxillary sinus cavity.
As our engineered implants and the surgical and prosthetic components are more precisely manufactured, the resulting successes with dental implants is amazing.
During the process of integration of the grafted sinus material, transitional crowns were fabricated on the maxillary anterior natural teeth to determine whether the patient could tolerate the increases vertical dimension of occlusion to improve his esthetics and function (Figure 4). Prior to surgical placement of our dental implants, we attempted to visualize proper final tooth shape and position and the placement of the dental implants to maximize emergence profile. Figure 5 demonstrates the proper spacing of our dental implants in the teeth #3-5 edentulous sites. Simple mathematics was used to determine ideal shape and emergence of each missing tooth. Placement of dental implants has to follow specific rules to be successful. There must be at minimum 2mm between a natural tooth periodontal ligament and the outside surface of our dental implant. Implants must be minimally 3 mm apart. Here we wanted to design a 6mm wide first bicuspid tooth, a 7mm wide 2nd bicuspid tooth and a 9mm wide first molar tooth. Since there was adequate edentulous space for three eventual implant retained crowns, we are able to virtually design the prosthesis and then determine the spacing of our dental implants using our computer software (3DDX, Boston, MA).
Because there was no sufficient bone to support dental implants in the right and left posterior quadrants, relatively invasive Caldwell Luc procedures were done. A window was made on the facial aspect of the missing teeth and the sinus filled with allograft material (1) After approximately 6 months of healing, the graft converts to bone allowing for more acceptable implant placement. The Schneiderian membrane was elevated without complication. (Figure 6)
Figure 7 illustrates how a digital design was made with the help of 3DDX (Co-Diagnostics) software. Idealized crown fabrication was tooth using a “tooth- up” approach is applied.
Now that there was sufficient available bone in the posterior maxillary edentulous sites, 0steotomies for the Hahn dental implant system (Glidewell Lab, Irvine, CA) were completed through fabricate surgical guides and the implants threaded into place. Here, CoDiagnosticX Software (3DDX) was consulted to help design the implant positions and eventually fabricate the final surgical guide. The surgical guide helps in the proper angulation and depth of the implants and is both a tooth born and hard tissue supported. (Figure 8) A reflection of the attached gingiva is made prior to seating of the surgical guide. With this particular design and the use do the Hahn guided surgery kit, the osteotomies are made through the sleeves and the implant is torqued through the guide to proper seat. (Figure 9) The Hahn implants are tapered and feature prominent threads, which ease insertion into the osteotomy site and initial stability. There is a machined collar which helps prevent bone loss around the neck of the implant and also has a cleansable surface. The prosthetic connection is a built- in platform switching helps minimize the resorption that could occur with other systems, where the connection between the implant and abutment is at bone level, by preventing a micro-gap and potential bacterial invagination. The post- operative CBCT illustrates the positioning of the dental implants with appropriate facial and palatal bone (Figure 10)
Following approximately 4 months for integration of the implants, tissue level impressions are made of the dental implants and remaining prepared teeth. (Figure 11) Edentulous spaces are routinely restored using zirconia crowns and bridges (Bruxzir, Glidewell Lab, Irvine, CA) These esthetic, functional and stable devices provide increased chewing ability, excellent wear resistance and improve the quality of life to many of our patients. Precise esthetic crowns are milled using computer software. The crowns are virtually designed and can be evaluated by both the laboratory technician and the dentist. Figure 12 shows the Bruxzir zirconia crowns (Glidewell Lab, Irvine, CA) that are threaded into each implant and onto the prepared teeth. These individual screw retained implant crowns are easy to maintain.
The post-operative periapical radiograph illustrates the final implant position (Figure 13).
Figures 14 and 15 show how the prostheses are evaluated for proper occlusion and the final smile design created to improve esthetics and function to our patient.
Patients have become educated on various dental procedures available to them. Certainly, dental implants have become an important treatment option over conventional fixed or removable appliances. When patients request some type of fixed appliance, implants are considered and the crowns are fabricated, either with prepared custom abutments with custom margins created at or slightly subgingival, and cement on crowns, or screw retained implant crowns. Creating healthy, esthetic smiles with our most modern and innovative methods is the new goal of our profession. Dental implants are just one of the more popular ways of accomplishing this goal. With the advent of internet education, our patients learn about the procedures before they ever see a dentist. Patients are aware of their physical condition, whether it be missing teeth or discomfort, and they search for ways to resolve their problems.
CBCT imaging has become a viable tool to help us in diagnosis and virtual positioning prior to any surgical intervention. The risks and concerns or proper implant placement can be reduced or eliminated. CBCT analysis is embraced by the dental profession as a critical tool in evaluating the predictability of surgical placement of dental implants. Vital anatomy is reviewed and the amount of available hard tissue precisely determined. However, there is much more to dental implant therapy than simply threading in our titanium “sparkplug” into an edentulous area. The final prosthesis needs to be considered and idealized for form and function. This too can be accomplished with our CBCT and digital diagnosing software. Final tooth position can be created and the final implant placement pre-determined before surgery on the patient. Technology has come to our rescue and helps us to practice more efficiently and proficiently. The final result is most important, as our satisfied patients promote our practices and insure our future success.
REFERENCES:
Lee, S, Kang Lee, G, Kwang-bum, P eta al. “Crestal Sinus Lift, a Minimally Invasive and Systematic Approach to Sinus Grafting.” J. Implant Adv. Clinci Dent. 2009: 1, 75-88
Nolan, P, Freeman, K and Kraut, R. “Correlation Between Schneiderian Membrane Perforation and Sinus Lift Graft Outcomes: A Retrospective Evaluation of 359 Augmented Sinus. J. Oral Maxillofacial Surgery. Jan 2014, vol 72, issue 1. 47-52.
Cakur, B.Akif, M et al. “Relationship Among Schneiderian Membrane, Underwood’s Septa and the Maxillary Sinus Inferior Border.” Clinical Implant Dentistry and Related Research. Feb 2013, Vol. 15, Issue 1. 83-87.
