Why Does Implant Dentistry Need a Dedicated Screw Channel Barrier Material?

Scientific and clinical rationale for the practice of implant dentistry was adopted at the Toronto Osseointegration Conference in 1982. (1) Brånemark and coworkers also laid the foundation for the prosthetic design which we are still using in the fixed rehabilitation of edentulous jaws. This early prosthetic design consisted of prefabricated screw-retained basal abutments and screw - retained fixed prosthesis. (2) Many components of the restoration could be standardized with prefabricated parts and prosthesis could be repeatedly inserted and removed during fabrication and service. This design also created a screw access channel which can be viewed as a dead space (cavity) in the prosthesis. Indications for implants further expanded and alternative designs were developed by borrowing existing protocols from fixed and removable prosthodontics. Prosthetic solutions evolved into cemented restorations and removable overdentures.

It would be wise to take a further look at the prosthetic design of cemented restorations. The rationale for this design was to hide screw channels by covering them with a prosthesis so that unsightly channels would not be visible or weaken the occlusal table of restorations. (3) Despite its advantages, cement-retained restorations created challenges of their own.

Both screw-retained and cement-retained approaches can be successful, but we have also made several important observations over the past two decades. Firstly, a considerable number of implant restorations require maintenance, repair, and re-treatment. (4) Next, cement-retained restorations can be prone to complications associated with residual cement left inside the soft tissue. (5) Based on these observations, one can conclude that retrievability is an extremely desirable feature of implant restorations, and in the case of large reconstructions, it is mandatory. Therefore, to achieve predictable retrievability and reliable management of cement, the screw-retained design proves to be a more versatile option.

The early screw-retained prosthetic design was based on the UCLA abutment concept. (6) In the past decade, the concept of screw retained restorations has further expanded with the wider adoption of zirconia and glass ceramic material. Contemporary single and multiple unit screw-retained restorations are fabricated in a “hybrid” manner where restorations with access holes are adhesively cemented over custom or prefabricated abutments. (7) Monolithic and partially veneered zirconia ceramic with improved strength also allows for a more forgiving location of screw channels, without the need for them to be covered by the cemented restoration.

Another innovation was created with the introduction of the angulated screw channel concept: a specially designed driver could access retaining screw at an angle, thus, allowing for re-angulation of the screw channel into a more desirable location of the restoration. (8) In this manner, esthetics and strength of the restoration can be optimized for long term clinical performance.

At this moment in time, modern prosthetic design favors a screw retained approach. By committing to this approach, we create screw channels with a significant volume which need to be predictably managed by the clinician.

How we manage the screw channel of implant restorations is important to minimize bacterial colonization, increase efficiency and future retrievability. (9) There is no question regarding what type of material to use on the surface of restorations since direct composite filling materials suit this purpose very well. (10) However, there is a considerable debate about which barrier material one should use between the screw head and composite filling. All existing solutions involve using off the shelf materials, and we have never had a well-accepted clinical product developed specifically for this purpose. (11).

Earlier screw channel barrier options included cotton, silicone impression material, and endodontic gutta percha. However, in one form or another, the use of these materials can be problematic regarding placement and removal efficiency. In addition, it has been shown that cotton can facilitate microbial growth inside the channel. (12).

Faced with these limitations, clinicians continued to look for better options. A potential solution in the form of PTFE plumber’s tape (AKA threaded pipe tape, Teflon tape) was proposed in dental literature in 2010. (13) Use of plumber’s tape has been previously documented in adhesive dentistry as a protective barrier covering for natural teeth. (14) So why use plumber’s tape as a barrier material? PTFE textile offers several advantages as a barrier material: it is hydrophobic and displaces moisture from the screw channel, it compresses well, can be easily removed, and provides a low-cost solution. These advantages made plumber’s tape gain popularity as a screw channel barrier material.

A closer look plumber’s tape reveals some obvious problems. Plumber’s tape is not a standardized biocompatible medical product. Manufacturers of plumber’s tape are not required to comply with regulations established for medical products. Purchasing plumber’s tape typically involves a trip to the hardware or online store where clinicians are faced with many options.

It is quite confusing to select an appropriate product since none of them are made for the intended dental application. Furthermore, industrial products may present with impurities, contaminants, oils, and colour additives not approved for use in the human body. The clinical article which proposed the use of plumber’s tape inside screw channels suggested in-office sterilization prior to its use. However, in clinical practice, most clinicians use this product straight off the roll non-sterile.

Many clinicians assume that plumber's tape it is equivalent to the biocompatible PTFE sutures, membranes, and graft materials. Unlike plumber’s tape, medical products must comply with strict regulatory protocols. (15) If there is a quality issue or adverse effect with plumber’s tape, it will never be discovered or reported.

Another disadvantage of plumber’s tape is its non-optimized properties regarding shape and density. Practicing clinicians are aware of how long it takes to pack plumber’s tape into the large channel of implant restorations. Based on these limitations, one can see the clear need for an optimized screw channel barrier product.

Right from the beginning, we tried to address the limitations of the existing options by creating FirstPlug. It is a compliant medical PTFE product optimized in its dimension and density for use inside the screw channel. The same can be said for the delivery container and placement and removal instruments. These optimizations allow for more efficient placement and removal, thus, saving clinicians valuable chair-time. The per-application cost of FirstPlug is comparable with other dental accessories such as composite polishing disks, rubber dam, tray adhesives, and impression material injection tips.

Treatment of implant supported restorations requires biologically sound management of screw channels, which includes appropriate selection of a barrier material. The proposed solution in the form of a specially designed medical PTFE product provides clinicians with a better option in comparison to existing solutions. Additional concerns associated with use of industrial or not-optimized dental products are eliminated by using a dedicated material that follows accepted standards for medical devices.