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Practical How To

How can I use CBCT and barium markers when placing temporary implants?

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By Dr. Robert Waugh

When it comes to the placement of temporary implants (TADs) in difficult areas, CBCT technology and radiopaque markers provide the diagnostic views necessary for 3D treatment planning and treatment sequencing in cases involving the temporary replacement of a missing maxillary lateral incisor. My overall treatment sequence is best described and executed as a three-stage plan, including appointments for:

  1. A focused-field 3D CBCT scan of the patient’s anterior maxilla while wearing a flipper prepared with a barium-laced acrylic marker;
  2. TAD placement and analogue impressions; and
  3. Delivery of an acrylic pontic over the TAD to restore the space for the missing lateral. 

The focus of this post deals largely with the first of these three steps, explaining the diagnostic advantage of combining 3D CBCT and a barium marker.

For my patients with congenitally missing anterior teeth who are approaching the final stage of orthodontic treatment with open space(s) planned for eventual prosthetic replacement, I schedule a consultation to review treatment options. Generally, these options include (1) single tooth implants for my non-growing patients or (2) non-integrating miniscrew TAD replacement for growing patients. 

Given that most of my patients are still growing when they finish treatment, there is a demand for temporary implants to serve as a fixed option until the patients reach an age where a definitive implant can be placed and permanently restored.  Once the recommendations, limitations, and risks of interim TAD-based anterior tooth replacement have been understood and accepted, I remove the braces and place an Essix retainer containing an acrylic pontic.

At this point, I take a second impression for the fabrication of a modified flipper appliance (acrylic removable partial denture).  The modified flipper is initially an acceptable solution to the patient for esthetics and retention, although a non-removable replacement is highly anticipated for the next few years ahead of the eventual implant restoration.

The acrylic appliances used in my orthodontic practice are fabricated by Master Dental, a dental prosthetics lab located in Athens, GA. The lab technician modifies the appliance by preparing a 2mm diameter hole over the highest point of the alveolar ridge, centered in the space for the missing tooth.  The hole is then filled with a plug of acrylic mixed with barium sulfate to create a radiopaque three-dimensional cylindrical marker for the scan (figure 1).

 

3D cylindrical marker for scan

Figure 1: 3D cylindrical marker for scan

Once I receive the modified flipper and it’s positioned in the patient’s mouth, I take a high-resolution, focused-field scan of the patient’s anterior maxilla using my CS 9000C 3D system. Then, using Carestream Dental’s 3D imaging software, I am able to easily locate the radiopaque acrylic marker on the 3D volume, which provides a reference for diagnostic length and width measurements (figure 2) as well as for the simulation of the virtual insertion of the TAD (figure 3).  The appliance thickness or marker height predictably references the occlusal clearance of the TAD head and measurements can clearly show the soft-tissue thickness, which is located spatially between the apical limit of the marker and the height of the bony alveolar ridge. 

Figure 2: Diagnostic length and width measurements on 3D volume

Figure 2: Diagnostic length and width measurements on 3D volume

 
Figure 3: Simulation of the virtual TAD insertion

Figure 3: Simulation of the virtual TAD insertion

Then, I obtain an accurate measurement for the precise selection of the ideal TAD dimensions—using the software’s Curved Slicing tab—as well as virtually place the TAD on the 3D surface volume to create custom implants for the simulation of the intended labio-lingual position and axial inclination of the TAD(s) (figure 4).

Figure 4: Virtual placement of the TAD on the 3D surface volume

Figure 4: Virtual placement of the TAD on the 3D surface volume

When the treatment is complete, I can schedule a second appointment to transfer the virtual TAD plan to the actual placement of the TAD.  I remove the barium acrylic markers with a small bur, leaving a cylindrical 2mm hole in the flipper indicating the area of intended TAD placement. Next, I use a soft-tissue pen or marker intraorally through the holes to stain the exact position for the operator to begin TAD insertion. 

After removing the flipper, I place the TAD without the use of a guide to its intended vertical dimension. Generally, I take a PVS impression of the upper arch along with an alginate impression of the opposing lower arch. Then, I pour the maxillary impression after positioning a dummy or discarded TAD as an analogue for fabrication of the processed acrylic pontic. Finally, I widen the holes left on the flipper to fit over the TADs and release the patient with the modified flipper.

The third—and final—step in this process involves the trial fit and cementation of the acrylic pontic.  I have a final Essix retainer made over the entire upper arch for retention. By providing relief around the miniscrew and pontic, this ensures an easy path of insertion and removal for the retainer that does not strain the restoration.

Making a difficult procedure easier for patients and practitioners requires the right materials and technologies.  I have found the creative use of CBCT technology to be an extremely valuable tool in developing predictably successful clinical procedures for my patients.

 

About Robert Waugh, DMD, MS
Dr. Robert Waugh has practiced orthodontics full time in Athens, Georgia since 1989 and is an Assistant Professor at Georgia Health Sciences University (USA) College of Dental Medicine's Orthodontic Residency program.  Dr. Waugh has served as President of the Georgia Association of Orthodontists and is a member of the International and American Colleges of Dentists.

For more information on the CS 9000C 3D and how it can help with complex orthodontic procedures, please visit carestreamdental.com

 

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