Commentary: Replacing Missing Teeth With Dental Implants: A Century of Progress
AbstractThere are few individuals in the last century who have changed how dentistry treats patients more than P.I. Brånemark. His seminal work, widely cited for years, defined the process of “osseointegration” of implants and changed dentistry’s opinion about implants in the oral cavity.1-3 Prior to the publications by Brånemark and his colleagues, implants were primarily being placed in the private practice setting by other pioneers in the field. However, the results reported by different clinicians were not consistent. In looking back, the problem was that these implants, whether blades or screws, were fibrous encapsulated; there was no bone-to-implant contact, which made them susceptible to infection. If an infection established near the crestal bone, it could easily surround the entire implant and lead to loss of the implant as well as the surrounding bone. Some of the reasons these implants were not integrating with bone included the surgical technique, which involved high cutting temperatures and incorrect loading; furthermore, most implants had very smooth surfaces. There were also other types of implants such as subperiosteal and ramus frame implants that would rest on the edentulous ridge and be covered by periosteum. However, these implant designs also had problems with bacterial infection around the abutment posts that supported the patient’s prosthesis. Despite active infections around many of these early implants, patients often felt they had a better quality of life than with their prior complete dentures. In fact, one of the reasons these implants developed a bad reputation was because patients often refused to have their implants removed even though the sites were clearly infected. By the time Brånemark’s group in Sweden presented their research, there were very few believers in dental implants. Those clinicians in the United States who did want to learn about dental implants had to either go to Toronto or Sweden to get appropriate training. Dental schools in the US were not yet convinced that any type of implant could be a successful long-term therapy. Brånemark et al. showed the profession in a scientific and methodical way that the bone could predictably attach to a screw made of titanium. He also gave the profession a clear and repeatable surgical technique and methodology for placing these implants and for allowing them to heal prior to loading.4-6 When the data from more than 8,000 implants consecutively followed for many years were presented, the world had to pay attention. Brånemark had given dentistry a rationale and a technique to allow the implants to “integrate” with the bone. It was not long before full-arch edentulous cases were being treated in the same way with five or six implants placed around the arch or between the mental foramina. Then, after realizing that these implants could integrate with bone and survive normal occlusal forces, it was not long before the profession was trying to use these implants for smaller partially edentulous spaces as an alternative to partial dentures.7 At this same time, another pioneer in modern implant dentistry, Andre Schroeder in Switzerland, was teaching the profession that dental implants did not have to be submerged at the time of surgery; the concept of the non-submerged implant was born. It was only natural for dentistry to start building on the basic principles of osseointegration to advance implant dentistry by exploring different methods of placement and loading.8-10 We now knew it was not necessary to submerge implants during the healing phase, and immediate loading of implants for full-arch cases was also shown to be as effective as if they were submerged and not loaded. In addition, incision designs were modified and became more conservative. Crestal incisions became routine instead of vestibular incisions, reducing postoperative discomfort for patients. Today, of course, it is routine to not submerge implants as well as to use crestal incisions for placement of implants. Also, as periodontists became concerned about cleansability and ease of hygiene with mucosal margins around these implants, further revisions in techniques focused on the importance of the preservation of attached gingiva and maintenance of the implants. The replacement of missing teeth with dental implants also brought about the recognition that crowns placed on implants were not susceptible to decay. Thus, clinicians could feel comfortable placing implants in patients who were prone to caries. What a wonderful paradigm shift for the replacement of missing teeth: stable support in the form of osseointegration and no decay under the restorations. Dentists no longer had to cut down perfectly healthy teeth to support a three-unit bridge just to replace a missing tooth. However, problems started to emerge when fully machined implants were used for single-unit replacement and implant-supported, small-unit fixed bridges. It became clear that there were positive and negative aspects in using machined implants for single and small-unit cases. Certain types of excess occlusal stresses in highly cancellous bone appeared to result in the loss of osseointegration, with a resulting loosening of implants.11 These observations led the profession to explore other implant surface coatings and textures that appeared to perform better in highly cancellous bone. The newly introduced coatings and textures were apparently allowing the bone to integrate and hold better under various occlusal forces. These changes meant that teeth with a poor prognosis could now be predictably replaced with implants in a variety of clinical situations where patients previously would have had healthy teeth prepared to accommodate fixed partial dentures. Still, given all of the impressive strategies that implants now allowed for replacing teeth, dentistry started to note problems. With time, implants, particularly the rougher textured ones, although secure and supporting bridges and crowns well, started to show that just like teeth, they could be susceptible to peri-implant diseases such as peri-mucositis and peri-implantitis.12 It became apparent that there are two parts of the implant surface that we as periodontists must be concerned with. First, the implant surface had to be appropriate for sound bone-to-implant contact (osseointegration). However, the coronal portion of the implant, which is exposed to the bacterial challenge of the mouth, had to be smooth enough not to foster plaque accumulation. This combination of two different needs for the implant surface has allowed companies to modify the coronal, middle, and apical ends of the implants.13 These fixture modifications, combined with new implant surface coatings and textures as well as new shapes of abutments, appear to be critical to the future of the discipline of implant dentistry. Clearly that future is bright, as periodontists embrace the responsibility of placing and maintaining dental implants. All in all, it has been an impressive century of progress in implant dentistry. Dental implants have ushered in an incredible paradigm shift in our ability to replace missing teeth or teeth that cannot be successfully treated. As dentistry continues to advance this exciting area of the profession, our ability to care for patients will only get better. ACKNOWLEDGMENT The author reports no conflicts of interest related to this commentary.
(Revista) ISSN 0022-3492