…Horizontally Screw Retained PFM Fixed Partial Denture
By Jeff Benson, DDS
A 65 year old male lost teeth #’s 8 and 9 many years ago and waxed bridge from #6-11 was placed. The #6-11 bridge eventually failed, likely due to a combination of a deep overbite and bruxism. In the pretreatment photo (figure 1), note the gum line fractures of #’s 6, 7, 10 & 11, palatal contact of the lower anterior teeth and loss of bony ridge both vertically and facially. With minimal tooth structure remaining, and with the failure of the previous bridge in mind, it was agreed that an implant supported prosthesis would o er the best outcome for the patient. Implants were placed in #6, 7, 10 and 11 positions.
In order to accommodate both the ridge form and the deep overbite, the lateral implants needed to be angled farther to the facial than ideal, resulting in screw holes which would have exited through the facial surfaces of those restorations. After extensive consultation with the patient and the dental laboratory, an implant supported, CAD/CAM generated, titanium bar mesostructure with a porcelain fused to metal superstructure were chosen to address the overbite, bruxism and screw exit issues. It was anticipated that the parent’s bruxing habit might lead to porcelain damage in the future, so horizontal set screws were employed to make the PFM superstructure easily retrievable for porcelain repairs.
A verification jig (fig 3) was fabricated on the master cast and seated in the mouth (fig 4) to confirm the accuracy of the master cast. A diagnostic mockup (fig 5) was fabricated and tried in the mouth to determine the proper tooth positions for the restoration and to guide the design of the bar. Panthera Dental designed the bar digitally (fig 6) and, once it was milled, the bar was tried in the mouth to verify fit. A new wax mockup which clipped onto the bar was tried into the mouth, and after some minor adjustments, was approved by the patient and the clinician. Once approved, this mockup served as a guide for the fabrication of the overlying PFM framework.
A resin and wax pattern of the PFM superstructure was fabricated directly on the bar (fig 9) and cast with great care to ensure accurate fit around the horizontal set-screws which would secure the superstructure to the bar (fig 10). Once the fit of the superstructure to the bar was conformed, the mockup was used to guide the application of porcelain to create a functional and esthetic simulation of hard and soft tissues with porcelain extending into the ridge defect above #8-9 for esthetics and proper lip support (fig 11 & 12). Particular care was taken to ensure cleanse ability with dental floss and WaterPik. A maxillary night appliance was fabricated to minimize the risk of porcelain fracture due to parafunction.
The final restoration is shown in the mouth (fig 13).
Dentistry by John Keller DDS.
Implant Surgery by Bill Wilke DDS, MS Laboratory Services by Renstrom Dental Studio
- Pretreatment Consultation: Rick Aeziman
- Metalwork: Lori Johnivin, CDT.
- Mockups: Deanna Beckman and Lori Johnivin, CDT
- Porcelain: Todd Larson