Evolving Immediate-Load Bridges
A breakthrough in efficiency of mandibular full-arch restoration with Trefoil
By Glen Liddelow, BDSc, MScD, DClinDent
The TrefoilTM system is an efficient way to get a high-quality immediate prosthesis. Since immediate-load bridges were introduced about 18 years ago, reductions in time and cost have improved treatment acceptance dramatically, and the Trefoil system is an important continuation of this.
The Trefoil system (Figure 1) uses a pre-manufactured bar supported by three implants and innovative fixation mechanisms composed of articulating discs that ensure passive fit of the prosthesis (Figure 2).
The real time-saver, however, is the fact that there is no temporary bridge with the Trefoil system, and there are fewer steps required than a conventional custom bridge workflow. With the Trefoil system, you eliminate all preliminary appointments required to produce a definitive bridge—eg, impressions, jaw relations, tooth try-in, framework try-in, and definitive bridge insertion—as these procedures can be done on the day of surgery.
In total, an experienced clinician and laboratory will require around 6 hours of working time, depending on clinician preference and close cooperation with the laboratory.
From a laboratory perspective, there are both time and cost savings. With the pre-manufactured bar there is no need to design the bridge framework.
First, the clinician places three implants in the predetermined position using guided templates. Following placement of the implants (Figure 3) and construction of a verification index that records the exact position of the implants (Figure 4), the prosthetic workflow begins by securing implant replicas to the verification index and embedding them into the master cast constructed with hard die or type IV stone in a base form (Figure 5). Once the stone is cured, the verification index is removed and the pre-manufactured Trefoil bar is placed onto the master cast model with the preassembled fixation mechanisms and try-in screws (Figure 6). Pressure is applied to the bar while tightening the screws to 15 Ncm. Passive fit of the prosthesis is facilitated by the self-adjusting articulating discs of the fixation mechanism. Following verification of passive fit, the fixation mechanism is secured in place with either resin or laser welding (Figure 7).
After sandblasting and cleaning, the bar is opaqued to minimize the translucency of the metal bar. A wax rim is attached to the Trefoil bar for intraoral bite registration. Impression material can be placed on the top of the wax rim and below the bar to obtain the occlusion and contour of the ridge simultaneously. Once the impression is taken and casts are prepared, the bar with wax rim is then secured to the master cast once more and mounted against the maxillary cast in the articulator (Figure 8).
Based on the articulation with the opposing dentition cast, the prosthetic teeth are mounted in wax. Once the tooth wax-up has been evaluated for position, occlusion, and adequate spacing around the bilateral distal cantilevers, acrylic processing can begin (Figure 9). The new acrylic fixed bridge is trimmed, polished, and cleaned, ready for placement by the restorative clinician (Figure 10 and Figure 11).
The definitive restoration is fixed with clinical screws with a torque of 35 Ncm (Figure 12). The occlusion is adjusted, if needed, and the screw access holes are covered with Teflon tape, silicone, or cotton and sealed with a minimal layer of resin.
Thanks to the Trefoil bar's fixation mechanism, patients receive a passively seated final prosthesis up to six months earlier than conventional full-arch treatment. The biggest factor is the time savings in waiting for the framework—the laboratory can immediately begin production of the bridge and not have to wait and track framework delivery.
For the patient, the main benefit of the Trefoil system is that getting a definitive prosthesis is fast: there is no provisional phase, a simplified workflow and less active working time for both practice and laboratory. Not only is the time-efficiency convenient for the patient, but it has the potential to translate into greater affordability. This is consolidated further by the efficiency of pre-manufactured, pre-assembled components. It forms a great alternative to fixed-removable treatments and gives more people access to high-quality full-arch treatment.
About the Author
Glen Liddelow, BDSc, MScD, DClinDent, is the Director for The Branemark Center Perth and a Clinical Associate Professor at the University of
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