If we listened to and believed some of the comments about small-diameter implants (SDIs) (or “mini” implants) that we hear coming from some areas of surgical dentistry, we would be led to think that these devices simply do not work. However, the truth is diametrically opposed to what some are saying, and it has been our observation that some of the most severely negative comments come from dentists who have never placed SDIs.
This article includes: the definition of “mini” or SDIs; a discussion of the evolution of SDIs, including their clearance by the US Food and Drug Administration (FDA) and research support; reasons for SDI use instead of conventional diameter implants; the indications for SDI use; and suggestions on how to use them successfully.
THE EVOLUTION OF THE SMALL-DIAMETER IMPLANT CONCEPT
There is no question among dentists that root-form implants, 3.0 mm in diameter and more, are one of the most successful and important additions to clinical dentistry in the entire history of dentistry. The FDA cleared these conventional-diameter root-form implants for clinical use in 1976. Millions of conventional-diameter implants have been placed for more than 4 decades, and their cumulative success rate of around 95% is impressive. In many situations, it has been our experience that the conventional prosthodontic portion of implant treatment fails faster than the properly integrated root-form implants themselves.
In the early 1990s, some innovative practitioners started using SDIs (up to 2.9 mm in diameter) for long-term use in situations with insufficient bone. At that time, SDIs were then considered to be for transitional use only. Also, orthodontists began using SDIs, also known as temporary anchorage devices, for anchorage for difficult tooth movement situations. It soon became obvious to those practitioners that properly placed SDIs were working adequately.
As a result of their obvious clinical success, SDIs were cleared by the FDA “for long-term intrabony applications” with the help of the Imtec company in 1997. Subsequently, numerous other SDI brands have received similar FDA clearance. Thousands of these SDIs are now in successful restorative use with a reported 91% to 97% survival rate. Numerous surveys, testimonials, research projects, and satisfied dentists and patients attest to that fact.1-6 Many more positive references are available in the restorative, prosthodontic, and orthodontic literature.
WHY USE SMALL-DIAMETER IMPLANTS IF CONVENTIONAL DIAMETER IMPLANTS ARE SO SUCCESSFUL?
Both of the authors of this article are prosthodontists who place both conventional and small-diameter root-form implants. The following are their observations on the desirability of SDI use compared to conventional diameter implant use.
Inadequate Bone Quantity
Conventional diameter implants, averaging about 3.5 mm in diameter, require minimally about 6 mm of bone in a facial-lingual dimension, and about 10 mm of bone in a crestal-apical dimension, for uncomplicated placement without grafting. Some patients accept the overall implant concept, but they have inadequate bone quantity and do not want to have significant bone grafting accomplished.
SDIs can be placed in as little as 3.0 mm of bone in a facial-lingual dimension and 10 mm of bone in a crestal-apical dimension. In fact, often bone 3 or 4 mm in a facial-lingual dimension is ideal, because the cortical bone plate on the facial has nearly approximated the lingual cortical plate, and this dense bone holds the SDI securely. Some experienced implant surgeons may question this, until they consider the fact that the SDI is usually a “screw,” expanding bone instead of cutting it away.
Inadequate Financial Resources
Some patients have inadequate bone, accept the implant concept, accept the need for extensive bone grafting, and they are ready to accept the treatment with the following exceptions: the cost of the grafting is too high, the expense of the restorative treatment is high, and conventional diameter implant treatment is denied. SDIs frequently solve this challenge, as stated in the previous point.
Compromised Physical Condition
Many physically debilitated patients do not have the ability to tolerate conventional diameter implant placement, but they can tolerate the simple, few-minute placement of SDIs without a flap. Recent research has shown that flapless implant placement may accelerate osseointegration and produce quicker healing. Debilitated persons can benefit from these simple procedures.
Major Uses of Small-diameter Implants
SDIs are listed in the Table in approximate order of decreasing frequency of use, as noted in the previously referenced articles, our own use patterns, and our observation of other practitioners.
If SDIs were used only for patients with edentulous mandibles, roughly 35 to 40 million edentulous patients in the United States alone would have better fitting and retained complete dentures. These implants are so easy to use in most edentulous mandibles that it is upsetting to us that they are not used more in the profession for the indications noted above.
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