November/December 2009, Volume 5, Issue 10
Published by AEGIS Communications
Pursuing a Biomimetic Approach to Implant Dentistry
Dentists need to understand the limitations to their ability to manipulate the human tissues in the oral cavity.
Dentistry has not yet entered the stage where clinicians have the ability to place truly biological implant components that can mimic and/or replace missing natural tissues. As a result, when it comes to implant dentistry, dentists still need to understand that the human body reacts toward any foreign object as a potential threat, emphasizes Nitzan Bichacho, DMD, professor in the department of prosthodontics and Head of the R.E. Goldstein Center for Aesthetic Dentistry and Clinical Research at Hebrew University. Therefore, when placing an artificial implant into living bone, what first is required is the introduction of a biologically compatible material in such a way that the body will accept—rather than reject—its presence.
Equipped with this understanding, Bichacho says that what implant dentists actually should be trying to achieve becomes clear in the context of several primary goals. The first primary goal is to try to be as harmless as possible to the existing natural tissue.
"This means that we need to be as minimally invasive as possible, trying to reduce the trauma from the surgery and/or keep it to the minimum, by minimizing the number of surgeries and trying to avoid unnecessary incisions and flaps, if possible," Bichacho says, "This also means that if we insert a fixture or an implant into the bone, we must try to remove the least amount of bone as possible, keeping the existing biological environment as healthy and undamaged as possible." This requires drilling the hole for the implant in as minimal a size as possible.
Secondly, clinicians must ensure that the soft tissue covering the bone will be able to recuperate to the maximum volume possible, then remain there. Further, Bichacho adds that clinicians want the bone and soft tissue mass to remain in position for long periods of time, without receding or undergoing remodeling. It is, therefore, imperative that clinicians minimize these unfortunate processes.
"I think that what we need to accept is that there are limitations to our ability to manipulate the human tissues in the oral cavity," Bichacho says. "If we understand the reaction of those tissues and the limitations that we can work within, then we will be able to achieve long-lasting implant-supported restorations in a healthy environment that are functional and esthetically normal in their appearance."
What Bichacho envisioned and co-designed with three other dentists to accomplish this, is a screw-type implant with very unique threads and a small-head body design for screwing into the bone via a relatively narrow hole (Nobel Active System, Nobel Biocare, www.nobelbiocare.com). With this type of implant, less living bone tissue is removed, he says, and placement into the exact location is facilitated.
From a minimally invasive perspective of biomimetics, such an implant preserves more bone, since its placement destroys less bone, Bichacho explains. Additionally, the configuration design of the implant body enables its placement in certain clinical situations in which there is less bone, such as in defect areas immediately following an extraction. The implant configuration provides a relatively high primary stability and can engage even in small areas of bone and remain there, Bichacho says.
"This means that, many times, it minimizes the number of surgeries that the patient has to undergo, because in many cases you can place an implant even in clinical situations that are less than ideal and it will osseointegrate," Bichacho elaborates. "Moreover, in those cases where the implant has sufficient bone to engage, the primary stability of this implant enables, in many circumstances, immediate provisional restoration of the implant, and this has proved, in the long run, to result in a better gingival adaptation."
The head of the implant was designed in a tapered manner so that it is always very small in diameter. As a result, the bone surrounding the head of the implant has a greater chance to remain there in greater volume.
Bichacho explains that it is understood today that for bone to remain at the same level, a minimum mass of tissue must exist. Most implant systems would require drilling away the precious part of bone at the crest level, leaving only very thin bone surrounding the implant's head. When the bone surrounding the implant's head exceeds 1.5 mm, there is a much better chance it will remain there during the modeling and remodeling processes that follow during the biological cascade of the bone tissue. That is why a narrow implant head is an advantage in terms of the residual bone surrounding it.
"We cannot pretend to think that today's implants materials have anything to do with a true biological tissue. It is still a foreign body that is being inserted into the remaining tissue of the jaw, but when there is less trauma in order to place it, clinicians can take advantage of such implant designs in order to stabilize it better," Bichacho says. "Then, the upper part of the bone and covering gingiva can be matched to re-establish the proper contours around its head, which leads automatically not only to stable tissue for the long run, but also for much better esthetic results." When the original or even a larger mass of soft tissue surrounds the implant head, a very natural-looking crown supported by that implant can be developed, one with a nice soft tissue envelope surrounding it, he adds.
Another insight Bichacho shares regarding the stability of the soft tissue is minimizing the number of connections and disconnections of the prosthetic component. In the esthetic zone, the clinician should choose an implant system and such prosthetic components that allow for minimal disconnections of the abutments, he says. The ideal situation is to connect the abutment once, right after the implant's placement, or when it can be loaded and leave it untouched.
"So, to summarize, today we are not yet in that stage where we are utilizing true biomimetic components in implantology when it comes to the implant itself," Bichacho emphasizes. "Although the implants today are manufactured with different surfaces by types of treatment, we are not yet there."
As a result, in order for clinicians to try and "compete" with the natural tissues, Bichacho reiterates the need to understand that the best that they can do is to be as least traumatizing to the tissue as possible, since whatever is done might cause the body to start fighting in order to defend itself.
"By being less traumatizing to the body, and simultaneously being as humble as possible with our clinical approach and with the selection of components that we use, the body then will accept our treatment much more favorably," Bichacho says. "This will enable us to provide our patients with therapies they can enjoy for many years."