The Missing Link for Dental Implants
A new implant system holds the key to dental team communication.
Why has an interocclusal bite registration that is taken over prepared teeth become the accepted protocol in fixed restorative dentistry? Although mucosal bite records have long been accepted in removable prosthetics, the unpredictability of a bite record over tissue does not meet the exacting demands of fixed restorations.9 Common sense has long dictated that occlusal records be taken over the prepared teeth for fixed prosthetics; the acceptance of this science has become unquestionably
universal (Figure 1).
Dr. Jeffrey Rouse taught us that there are six key principles to an accurate bite registration.7 First, it is crucial that a high consistency polyvinylsiloxane (PVS) addition-type bite material is used because it is accurate, easy to dispense, and available in a variety of rigidities.7 Second, PVS bite registration is subject to the same hydrophilicity issues as PVS impression material.7 Therefore, it is necessary to always work in a dry field to prevent the PVS material from hydroplaning off of the teeth, which would result in poor duplication of the necessary occlusal dentate. Whenever the registration is taken with a serious lack of detail, the accuracy of the mounted casts may be challenged.7 Third, to ensure that the maxillary lingual cusps are captured in the impression, the clinician should always introduce the PVS to the maxillary arch first.7 Fourth, to set the bite registration correctly, it is critical that the record be properly trimmed (Figure 2). Since the PVS bite registration captures the tooth pit-and-fissure detail, it is necessary to trim these details out and leave only the depth of the cusp tips (Figure 3). The facial portion of the bite registration should be trimmed far enough back to allow a clear line of sight to the preparations and opposing dentition.7 Fifth, clinicians should always form a bite registration strategy prior to preparing the teeth.7 Last, when the most posterior stops are prepared, dentists must be careful to avoid heavy bite forces during the bite registration. Patients should be asked to bite “half hard” into the interocclusal record.7 Although the technique and materials within these six principles may vary between clinicians, it is hard to dispute the chronological order of actions that should be taken when making interocclusal registrations for any fixed restorative case.
Today, dental implants have become part of the restorative mainstream and present the largest growth area in all of dentistry. In fact, the worldwide dental implant market is expected to reach $7.9 billion by 2015.3 We now have more choices than ever of implant platforms, implant accessories, and dental educators to help us work through all of these new technical opportunities. The science is taught routinely in dental schools throughout the world. Congruently, patient acceptance has never been higher.4,6 We can all accept that implant dentistry is here to stay and that more technical advancements are a foregone conclusion. However, at times, the road to advanced technology can be lined with great achievements—only to find that we have missed the mark on some core principle and we then struggle to find the easy solution.
Let us again visit the accepted science of bite registrations over prepared teeth and ask ourselves what happened to our bite registration strategy when it came to fixed-implant dentistry. The absence of tooth preparations in implant dentistry has led to occlusal uncertainty for fixed prosthetics. It is reported that far more post-fabricated occlusal adjustments or remakes result for implant cases compared to traditional fixed restorative cases with the occlusal records taken over prepared teeth.10 Implant dentistry has caused us to revert back to the problematic science of bite records taken over tissue, a technique long associated with removable prosthetics only. It appears that we have talked ourselves into believing the myth that a small healing cap erupting through the tissue can serve as a surrogate preparation. Healing caps do not serve this purpose well because they often require part of the record to be on the soft-tissue area of the cast to balance the bite while placing the casts together. Mucosal surfaces are soft and compressible, so bite records over them will likely hold the registration material away from its true relationship with the models of the teeth.1 This problem is further exacerbated by reconstruction cases that have opposing quadrants being restored1 (Figure 4 and Figure 5). Whenever interocclusal records for fixed prosthetics are dependent on soft tissue, it is common to find more than one vertical dimension at which to place the casts.7 Also, the sheer number of different lengths and diameters of healing caps makes them very expensive and adds a great deal of confusion to the science of setting the casts. It is not uncommon for a laboratory to have several hundred healing caps, and the guessing game begins when they attempt to align the bite, healing caps, and casts together on a new case.
Brilliant techniques have been developed and used by many clinicians in an attempt to solve the issue of the inaccuracy of implant bite registrations (Figure 6 and Figure 7). Clinicians have experimented with splinting square transfer copings with auto-polymerizing acrylic resin, splinting transfer copings with impression plaster over dental floss, splinting transfer copings with PVS bite-registration material, and splinting implant analogs using plastic sprues with connecting auto-polymerizing resin.5,8 The reason that these systems have not gained universal acceptance lies in their complexity, extra time, and expense, as well as the burden of additional communication between clinician and laboratory.
Implant Bite Posts
Now a new system has been developed to mitigate the problems associated with previous attempts to manage the inaccuracy of implant bite registrations. Implant Bite Posts (IBP™, www.lebeaudental.com/implant-bite-registrations.html) were developed to create a universal system for occlusal management of implant cases that aids in doctor-laboratory communication and creates predictable results for the patient (Figure 8). The IBP™ system offers a unique strategy that imitates the traditional science of bite records over prepared teeth that has become the bedrock principle taught in dental school (Figure 9 and Figure 10). The ease of use of the IBP system and its traditional strategy eliminate extra time and communication.
To record the interocclusal record on an implant case, the clinician needs to select an implant bite post that coincides with the type of implant platform being used. The next step is to select one of the two vertical heights available and screw the bite post in with light finger pressure. Each post bottoms out to the implant platform with three easy turns and offers the optimal undercut to capture a precise bite. The bite registration is taken by the clinician, making certain that some of the bite material flows between the two cylinders at the apex of the bite post (Figure 11). The clinician should always use a soft PVS material like Jet Bite™ from Coltène Whaledent (www.coltene.com). The bite registration and implant bite posts are then sent to the laboratory with a brief explanation noting which of the two vertical bite post heights were used and on which site. After fabricating the stone cast, the laboratory technician simply screws the bite post(s) into the appropriate site(s) (Figure 12). The bite registration is then placed over the bite posts on the cast and trimmed back on the facial to provide visual proof that the bite fits the cast as it did in the mouth. The technician should always attempt to trim the areas of the bite record that come into contact with the tissue area of the casts (Figure 13). The restorations are then fabricated, and the case and bite posts are sent to the dentist for seating (Figure 14 through Figure 16). Integrating the accuracy of the implant bite post with concise bite registration strategy creates a pathway to predictable occlusion for high-expectation dentistry (Figure 17).
Implants are among the greatest advancements in the history of dentistry. The discipline that began with the blade implants in the 1970s, and moved to the UCLA abutments in the 1980s, now has virtually designed the CAM-milled abutments of today.2 The one certainty that dental science can collectively count on is that the innovative spirit of its members will always seek ways to advance our technology and use it to reach further into a functional esthetic future. Implant bite posts are a didactic attempt to fill a void left by the absence of prepared teeth in interocclusal bite science for implant cases. In fact, using these implant bite posts may be even more accurate than registrations over preparations, because the bite post used for the intraoral registration is the same one used to set the casts. These titanium or surgical steel bite posts eliminate any flaw from the impression of the preparations. IBP™ offers the first universal system for implant bite registrations, and over the course of the next few years, the dental industry will cast its technical ballot. Without question, our industry is moving the science and art of dental implantology forward.
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10. Wilhelm MW. New methods for improving the accuracy of bite registrations in restorative implant dentistry. Compend Contin Educ Dent. In press.
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Owner and CEO
LeBeau Dental Lab