Digital Workflow Case Report
John Weston, DDS, FAACD
This case report illustrates how a digital workflow is used in a multi-specialty practice that includes both a general dentist and an oral surgeon. (For additional case images, please visit dentalaegis.com/go/id1140.)
A 45-year-old man presented with a fractured second mandibular molar. The tooth was subsequently extracted, and the site was grafted.
Approximately 5 months post-surgery, the patient was scanned using cone-beam computed tomography to determine the confines of the bone at the healed extraction site. After deciding where the implant should be placed to optimize the long-term health of the implant and satisfy the patient’s occlusal requirements with the restorative dentist, the surgeon placed a 10-mm Straumann Bone Level regular platform implant (Straumann Dental, www.straumann.us/en). Placing the implant at the bone level increases the number of restorative options and enables more precise positioning of the margin with a custom abutment. The implant was covered with a healing cap and allowed to osseointegrate for 3 months (Figure 1).
Submitting Digital Data
Like other digital workflows for implants, the Straumann system employs scan bodies that are seated into the implant and hand-tightened to approximately 15 Ncm. These scan bodies have a flat surface that must be oriented toward the buccal. They provide information to the software about the depth, angulation, and rotational position of the implant.
Removal of the healing cap revealed healthy soft tissue, and with the scan body in position an intraoral digital impression scan was taken using a 3M scanner. The scan body was then removed, the healing abutment replaced, and the opposing arch and bite were scanned digitally. The system then virtually articulated the digital models and combined the two images to replicate the proper occlusion of upper and lower arches (Figure 2).
Using the on-screen interface, the restorative dentist filled out a prescription form. It provides information to the laboratory about the implant that was used and the material desired for the abutment (zirconia in this case), crown material and design (cement-retained, lithium disilicate), and the shade and finishing opacity, occlusal staining, surface glaze, and texture.
The files and prescription were transmitted electronically to the laboratory, where the definitive zirconia abutment and crown were virtually designed and milled. The files shown in Figure 2 were also used to print a stereolithographic 3D resin model. An implant analog was placed in this model, along with the abutment and crown. The model was delivered to the restorative dentist 1 week after the intraoral scans were obtained from the patient. The restorative dentist examined the restoration on the model to verify the fit and become familiar with the proper orientation for seating the abutment and crown.
Figure 3 shows the zirconia abutment and crown on the digital model. Note how the margin is precisely positioned at the tissue level. This ensures the ability to easily visualize and remove any excess cement, which can be removed easily and thoroughly, alleviating any concern about retained cement increasing the risk of peri-implantitis.
The patient returned, and the healing cap once again was removed. After rinsing with chlorhexadine gluconate, the definitive abutment was connected to the implant and hand-tightened, and the crown was tried in. Minor tissue blanching is normal when the abutment is being tightened into position. The abutment was torqued to 35 Ncm and the screw-access hole was filled with teflon tape (Figure 4). The crown was then luted in a traditional style with dual-cure resin cement. With the final position of the margin precisely at the tissue level, cement clean-up was easy and predictable (Figure 5).
This digital workflow significantly simplified the process, shortening the steps and time required for replacing this patient’s fractured second molar. In the past, implant restorations required the capture of an implant-level polyvinyl siloxane (PVS) impression, followed by an abutment impression for a custom design. Using a stock abutment created potential complications, including excess cement potentially making its way deep around the implant, causing the implant to fail. The alternative of using screw retention instead of cement was often unsightly and required careful management.
In contrast, this digital workflow makes it possible to avoid the problems associated with using stock abutments and cement retention, requires just two appointments, and is more comfortable for the patient.
About the Author
John F. Weston, DDS, FAACD
Owner and Director
Scripps Center for Dental Care
La Jolla, California