An Era of Evidence-Based Implant Dentistry: 30 Years Since Toronto

In 1952, Swedish orthopedic surgeon Per-Ingvar Brånemark inadvertently discovered osseointegration—“the formation of a direct interface between an implant and bone, without intervening soft tissue”—while studying blood flow in rabbit bone using vital microscopy.^1,2 Recognizing the value of osseointegration, Brånemark and his colleagues spent the next three decades researching its application. While his original intent was to employ his discovery for knee and hip replacements, he realized that dental implantology would be more conducive to study.³

While Brånemark was researching osseointegration, other Europeans followed suit. They included Switzerland’s André Schröeder at the University of Berne, who was also working on a dental implant for clinical application. In conjunction with Institute Straumann, at the time an innovator in the integration and use of metal in orthopedic surgery, Schröeder “histologically demonstrated the in-growth of bone into titanium plasma-sprayed hollow endosseous implants.”⁴

But implant treatment outcomes of the time were erratic. The success rate for subperiosteal implants ranged from 39% to 66% at 10 years.⁵ Smithloff and Fritz reported similarly poor outcomes for blade-vent implants with a cumulative success rate of 55% at 5 years.⁶ As a result, in 1974, the American Dental Association took the position that dental implants were not recommended for routine clinical practice.

In 1978 the Dental Implant Consensus Development Conference jointly sponsored by the National Institutes of Health and Harvard University was the first of two landmark meetings that marked the transition out of an era in which implants were shunned as an unreliable and often experimental method for tooth replacement to one of dependability. It focused on implant modalities frequently employed in the United States. These included subperiosteal, blade-vent, vitreous carbon, and staple implants. In the end, the 1978 conference identified risks and benefits of implant therapy, and established standards in the field, many of which are still valid and useful today.⁷ The conference also recommended implementation of informed consent.

The Second 30 Years: Since 1982

Professor George A. Zarb of the Faculty of Dentistry in Toronto led the 1982 Toronto Conference on Osseointegration in Clinical Dentistry, which introduced the concept of osseointegration—along with its application in treating edentulous patients—to North America. It also legitimized the groundbreaking work of Brånemark’s team stating, “Brånemark’s major contribution toward implant dentistry is his thorough documentation of the long-term success of titanium in animal and human studies.”⁸ This is evident by his publication of the criteria for successful osseointegration in 1977 followed in 1985 by a 15-year follow-up of implant cases.^9,10 Subsequently, in 1985, Nobelpharma AB Sweden (today Nobel Biocare, Switzerland) filed the first application for commercial use of dental implants in the United States. Their application was approved the following year ushering in a new era of dental implantology. Soon after, other manufacturers followed suit.

The Toronto Conference on Osseo­in­te­gration in Clinical Dentistry also paved the way for the formation of the Academy of Osseointegration in 1986, which fostered the advancement of the field. Fittingly, in the first issue of the academy’s International Journal of Oral and Max­illofacial Implantology in 1986, Tomas Albrektsson and colleagues published an article on the myriad of dental implant systems. The first publication to summarize the research, treatment outcomes, and success rate of each system, it ultimately laid out criteria for successful implant therapy.¹¹

Trends that have emerged during the modern era included an initial focus on achieving osseointegration in and of itself with little regard for implant position to “crown-down” planning and subsequent implant placement. Prosthetic interfaces and components evolved, and there is a trend away from external to internal prosthetic connections in many clinical situations. In addition, advances have continued to focus on reducing healing times and, thereby, time to loading. Much of the innovation regarding time to loading is based upon alterations of implant surfaces and designs. Roughened surfaces seem to expedite osseointegration, increase surface area, and strengthen their attachment to bone; as a result, today rough surfaced implants dominate the market, allowing for implant placement into areas of limited bone quality and quantity, as well as expediting healing.

Implant dentistry is progressing rapidly today largely due to technological innovations. Most notably, cone beam computed tomography (CBCT) was initially introduced to dentistry by Mozzo et al in 1998, becoming commercially available in the United States in 2001.^12,13 As computer software and hardware evolves, other digital technologies are merging with CBCT to provide computerized implant planning and milling of computer-assisted design/computer assisted-manufacturing (CAD/CAM) and stereolithic guides. As software programs advance and milling of guides becomes more efficient and accurate, costs will diminish and availability will increase for clinicians. The plans and subsequent guides are driven by ideal implant placement, allowing doctors to do the “heavy lifting” on a computer rather than chairside. They allow doctors to recognize and compensate for shortcomings in alveolar support in advance of surgery. Additionally, these technologies allow doctors to mill custom abutments either in advance of surgical implant placement or at the end of healing. In either event, doctors and laboratory technicians can form and influence the shape and dimension of the transition zone as the restoration emerges through the gingival complex, predictably creating natural-looking tooth replacement.

The future of implant dentistry will focus on a number of issues. Researchers will continue to pursue shorter healing times using biologically active implant surfaces. Additionally, other materials will be combined with titanium or be used independently in order to create stronger, biologically compatible, and esthetic implants. Researchers are developing zirconia implants, offering biocompatibility, strength, and the benefit of natural tooth color. This will be particularly useful in thin biotypes where the gray hue of titanium may shine through. Additionally, if there is future gingival recession, zirconia implant bodies and abutments will be more esthetically acceptable than their present metal counterparts.

It can be said that Brånemark, Schröeder, and others ushered in an era of evidence-based implant dentistry. They set a new standard in the field, mandating that new products and techniques be based upon sound research and predictable outcomes.

Frederic J. Norkin, DMD

Adjunct Assistant Clinical Professor, Department of Periodontology, Nova Southeastern University College of Dental Medicine, Fort Lauderdale, Florida; Diplomate of the American Board of Periodontology

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