In the final part of this series (see Part I and Part II) on this specific case involving severe trauma, I'll discuss how prosthetic re-creation of the gingival aspect of the restoration presents a considerable challenge in regards to shade matching.
Composite resin available in gingival shades provides the opportunity to characterize the prosthetic tissue with layering techniques if desired. Composite improves the ability to control the contours and color of the gingival aspect, especially when the area is large. It minimizes the firing cycles of the restoration to protect the characterized porcelain teeth and allows for repair when necessary (Coachman IJRPD 2010). Composite resin materials available in gingival shades include GC's 'Gardia Gum' and Shofu's 'Ceramage'.
The original plan was to cement individual restorations on a framework to keep the crown and bridge separate from the prosthetic gingival structures. After consultation with The Winter Lab, the restorative plan was changed to porcelain restorations fused to the metal substructure with a combination of pink porcelain and red composite resin for the prosthetic gingival tissue.
The porcelain fused to the cast metal framework provided the opportunity for optimal color, proportion and character of the teeth. Pink porcelain was applied to the intaglio surface of the restoration as well as to the prosthetic free gingival margin area. Gingival shaded composite resin was applied between the free gingival margin area and the intaglio surface to provide the reddish appearance to the gingival aspect of the restoration.
The definitive restoration was designed as a hybrid screw-retained/cement-retained prosthesis in the maxillary anterior, and a cement retained prosthesis for the mandibular anterior. The maxillary prosthesis required a significant anterior cantilever to create the appropriate tooth arrangement and facial support. The cement-retained feature allowed adjustments for distortion of the framework as a result of the firing cycles required of the ceramic material. The screw-retained feature allowed for removal following cementation to ensure complete removal of the resin cement at the level of the intaglio surface of the restoration and the adjacent soft tissue (Agar JPD 1997).
The soft tissue contours created by the provisional restoration were duplicated to facilitate construction of the convex intaglio surface of the definitive restoration. The definitive abutments retained the indexed internal connections to limit the stretching and bending forces on the abutment screws. Non-indexed abutments for the Nobel Replace Select dental implant do not have an internal component; therefore the abutment screw would be the 'weak point' of the cantilevered prosthesis (Boggan JPD 1999). The process to construct a definitive restoration was based on three key elements:
- The initial diagnostic set-up transferred intra-orally in bis-acrylic to visually demonstrate the considerations related to tooth arrangement.
- The diagnostic set-up with teeth in wax to coordinate the contours of the interim prosthesis with the soft tissue support of the upper lip.
- The design of the provisional restoration to influence tissue contour allowing for a hygienic intaglio surface with an appropriate seal to accommodate for speech sounds and allow for the evaluation of prosthetic tooth and tissue color as well as contacts with adjacent teeth.
Intra-oral adjustments were made to the definitive prosthesis to provide broad contacts in protrusive and lateral movements while maintaining bilateral simultaneous posterior tooth contact at maximum intercuspal position. An acrylic occlusal guard was made to fit the upper arch to protect the prostheses while the patient is asleep.
The overall prognosis of the definitive restoration is good due to the solid natural tooth support in the posterior and the cleansability of the prostheses. Recall visits will evaluate oral hygiene and structural integrity of the dental implant supported fixed prosthesis particularly in the area of the screw access openings (Karl JPD 2007).
Coachman C, et. al. Prosthetic gingival reconstruction in fixed partial restorations. Part 3: Laboratory procedures and maintenance. International Journal of Periodontics and Restorative Dentistry 2010; 30: 19-29.
Agar J, et. al. Cement removal from restorations luted to titanium abutments with simulated subgingival margins. Journal of Prosthetic Dentistry 1997; 78: 43-47.
Boggan RS, et. al. Influence of hex geometry and prosthetic table width on static and fatigue strength of dental implants. Journal of Prosthetic Dentistry 1999; 82: 436-440.
Karl M, et. al. In vitro effect of load cycling on metal-ceramic cement- and screw-retained implant restorations. Journal of Prosthetic Dentistry 2007; 97(3): 137-140.
Douglas G. Benting, DDS, MS, FACP, Spear Visiting Faculty. [ www.drbenting.com ]