A Simple Technique to Create Accurate, Esthetic Immediate Implant Provisional Restorations: Hurricane Anti-rotation Wings
Robert J. Stanley II, DDS, PhD, MS
Abstract: Inserting a presurgically fabricated provisional restoration at the time of implant placement can be problematic if and when the provisional does not fit. The 3-dimensional position of the implant in the mouth typically is not as critical as the long-axis rotational orientation of the implant, which is known as "timing." During implant placement, it is often desirable to have one of the implant's internal hexagon flats in a specific rotational position (ie, timing) that enables the use of orientation-specific hexed abutments. Achieving timing with a high level of accuracy, however, is challenging. This article presents a proposed solution to this dilemma that eliminates any concern for implant timing during surgery by transferring the anti-rotation control from the implant's internal hex to the provisional restoration itself via the use of anti-rotational wing(s).
After tooth removal, the nonfunctional provisionalization of immediately placed dental implants provides several advantages over the use of a stock healing abutment or a delayed implant placement approach. The provisional restoration not only helps maintain existing architecture and retain structure created by gap grafting (Figure 1 and Figure 2), but this approach also typically represents a shorter cumulative treatment time for the patient with fewer office visits.1,2
Prior to implant surgery, use of a tooth replacement method that utilizes a prosthodontically driven protocol provides an opportunity for the surgeon to virtually plan an optimized solution and fabricate an immediate provisional restoration. After designing the ideal crown, the next step is to predict the likelihood of implant stability in the fresh extraction site, which can be done through the use of the five-thread guideline (FTG).3 The FTG, a novel guideline for predicting primary stability of dental implants, suggests engaging at least five implant cylinder threads in native bone to ensure primary stability. If the FTG requirement is met, then successful conclusion of this proposed method demands that the implant is placed within 200 µm of the planned 3-dimensional (3D) location, thereby allowing the prefabricated, laboratory-produced provisional restoration to be screwed onto the implant with little to no adjustment needed. To accomplish an accurate and precise 3D implant placement, including rotational orientation, the use of a type 4, dentition-supported surgical guide with timing indexes is recommended.4,5
Slight implant positional errors can usually be managed chairside by making minor adjustments to the prefabricated provisional restoration. However, just a few degrees of implant rotational error with an indexed provisional can render the prefabricated provisional esthetically and functionally unacceptablxse. A prosthetic solution that utilizes a non-indexing abutment (Figure 3) eliminates the need to control for implant timing (ie, the long-axis rotational orientation of the implant). Thus, by rendering the implant timing irrelevant, the rotational position of the prefabricated provisional is able to be established chairside according to the prosthetic treatment plan.
On many dental implants, the component responsible for constraining the rotational orientation of the prosthesis is the implant's internal hexagon, or "hex." This anti-rotation feature also allows the clinician to torque the abutment screw to the manufacturer's specifications while maintaining the correct rotational orientation between the abutment and implant. Without this feature, as is the case with non-indexed abutments, the abutment-to-implant rotational orientation can slip during torquing, resulting in possible esthetic and functional concerns.
This problem can be eliminated by utilizing a non-indexing prosthetic solution in conjunction with an anti-rotation feature. By placing temporary anti-rotation wings on the non-indexed provisional crown, the abutment screw can be tightened without compromising the planned rotational orientation (Figure 4). Once the desired abutment screw preload torque is achieved, the wings can be efficiently removed intraorally with a chairside adjustment kit (Figure 5).
Materials and Methods
Prior to surgery and upon completion of the virtual implant planning session, the anti-rotation wings are virtually added to the provisional crown. They are constructed to create a counterclockwise-resistant torque by resting on the teeth adjacent to the planned implant location. To aid in communication with the laboratory, the wings should be fabricated to resemble the hurricane symbol when viewed from the incisal edge (Figure 6). These wings should not extend from the facial embrasures of the provisional, nor should they make complete intimate contact with the adjacent teeth, but only rest upon them. While having complete contact with adjacent teeth would make the wings stronger, it creates challenges for easy esthetic wing removal chairside after torquing the abutment screw. Thus, the wings ideally should resemble arches, with a single-point contact originating near the line angles of the provisional and inserting near the line angles of adjacent teeth (Figure 7).
Once the wings are designed, the provisional can be milled or printed and luted to a stock non-indexed hybrid titanium base (ti-base) (Figure 8 and Figure 9). During surgery, after the immediate provisional abutment screw is torqued, the base of the wings can be quickly removed and easily polished because the wing's bases will be exposed and readily accessible. A single-wing approach can be implemented if more than one implant is being placed (Figure 10).
Discussion
Prefabricated provisional restorations provide many advantages over other provisional options during tooth replacement therapy. For example, Essix retainers do not allow patients to chew, bonded bridges cannot be used in-between porcelain restorations, and, although custom healing abutments provide excellent healing, they lack patient-demanded esthetics. The implant-retained provisional, on the other hand, is an esthetic temporary solution that is typically well-received by patients, probably because of its similarity to a natural tooth. This provisional option also fulfills prosthetic socket sealing requirements by containing and protecting the graft during the healing phase.1 Utilizing immediate provisionalization not only is advantageous for containing the graft but also helps to maintain both hard- and soft-tissue architecture.6 Maintaining existing architecture typically is easier than having to recreate it, both for the patient and the doctor.7 For example, if architectural collapse occurs, site development will be necessary and can involve hard- and soft-tissue grafting, tissue grooming via custom healing abutments or provisionals, and elaborate final prosthetic solutions, such as custom abutments and pink porcelain, designed to compensate for possible irrecoverable tissue defects, all of which will likely increase the cost and time required for procedures.
Additionally, if proper preload or clamping force on the prosthetic abutment screw is not achieved, screw loosening is possible.8 Abutment screw loosening may lead to complications like component breakage and implant failure.9 During the healing phase, if the screw loosens around the time of the suggested dip in stability between primary and secondary stability, then retightening could negatively affect wound healing and result in complete loss of stability and implant integration failure.10 Achieving the manufacturer's recommended abutment screw insertion torque is important to minimize the occurrence of abutment screw loosening.11 Utilization of the anti-rotation wing(s) can aid in achieving recommended insertion torque while maintaining the planned prosthetic orientation.
Conclusion
The concomitant use of a non-indexed abutment and anti-rotation wings on the provisional crown eliminates the clinician's need to control the implant placement timing, aids in achieving proper abutment screw preload, and helps maintain the prosthetic planned rotational orientation of the immediate provisional.
About the Author
Robert J. Stanley II, DDS, PhD, MS
Adjunct Professor, University of North Carolina School of Dentistry, Chapel Hill, North Carolina; Founder, Stanley Institute, Cary, North Carolina; Private Practice, Cary, North Carolina; Diplomate, American Board of Oral Implantology; Diplomate, International Congress of Oral Implantologists; Fellow, American Academy of Implant Dentistry; Fellow, Academy of General Dentistry
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