Re: The Truth About Small-Diameter Implants

WHY DO SOME DENTISTS STATE THAT SMALL-DIAMETER IMPLANTS ARE NOT SUCCESSFUL?
Many of the same surgical dentists now condemning SDIs stated 40 years ago that conventional root from implants would not work. It appears that their opinion is that anything new is automatically bad! SDIs are new, but they are proving themselves.

This section is probably the most important part of this article. Some SDIs fail. We have experienced a few failures ourselves over the past 9 years of use. These failures were almost always related to one or more of the following errors:
Too much thickness of the soft tissue. If the ratio of the coronal portion of the SDI to the portion placed in the bone is excessive, a long lever arm is present. This situation stresses the SDI and may lead to failure of the implant. If the soft tissue, through which the SDI is to be placed, is thicker than about 2 mm, it should be reduced by taking a wedge of tissue from the coronal portion of the ridge. This can be done before the implants are placed, allowing for adequate healing, or at the time of implant placement. This surgery may be done with a scalpel, or some lasers may be used around implants to accomplish this task without causing damage to the implant osseointegration potential.
Improper parallelism of implants. SDIs should be as parallel as possible. If these implants are much more than 15° from parallelism, technical difficulty at placement of the prosthesis and subsequent potential clinical failure can be anticipated.
Inadequate preoperative radiographs. Poor bone is commonly present in some areas of edentulous patients. We discourage using only 2-dimensional conventional panoramic radiographs, because you cannot determine the quality or quantity of the bone in a facial-lingual dimension. Coarsely trabeculated bone is not appropriate for SDIs. The more dense the bone, the better. To determine the density of the bone, facial-lingual oriented radiographs are strongly suggested. These include tomograph or cone beam radiographs. Most communities now have accessibility to some form of the suggested facial-lingual orientation radiographs at moderate cost.
Poor bone density in the posterior maxillary tuberosity areas. Usually, the dense Type I bone of the resorbed anterior mandible is excellent for SDIs. The worst bone, contraindicated for SDI placement by most experienced practitioners is the posterior maxillary tuberosity, with its porous type IV bone. A careful analysis of the density of the bone in any other part of the oral cavity is suggested, as they too may have poor bone density contraindicating SDIs.
Too few SDIs are often placed. It has been suggested in both empirical and research reports that the minimal number of SDIs for edentulous mandibles is 4, evenly spaced from the left canine area to the right canine area. This is double the minimal number of implants suggested for conventional diameter implants. The ratio appears to be 2 SDIs where one conventional diameter implant would usually be used. Some companies are suggesting 6 SDIs instead of 4 for edentulous maxillas, evenly spaced from the canine area to the opposite canine areas. However, the more dense the bone, the fewer SDIs that are needed.
SDIs are too short. The most popular average length for SDIs is 13 mm. It appears from both clinical observation and research that this is a predictable and successful length. The implants must be used in adequate bone, according to the literature of reported successful use of thousands of SDIs and to the discussions with manufacturers about clinician reports to them.
Poorly adjusted occlusion, or loading the implants too soon. Most SDIs are loaded immediately on placement. Occlusion needs to be adjusted perfectly on placement of the prosthesis. Allowing heavy occlusion to traumatize these small implants is asking for early failure. If questionable bone quality or quantity is present, soft denture reline material may be placed in the denture around the area of the implants for several weeks to ensure that they have optimum time for initiation of osseointegration.

SUMMARY AND CONCLUSION
SDIs that are treatment planned correctly, placed and loaded properly, and are within a well-adjusted occlusion, are working in an excellent manner for the patients described in this article. It is time for those practitioners unfamiliar with SDIs and their uses to discontinue their discouragement of this technique. SDIs are easily placed, minimally invasive, and a true service to those patients described. They do not replace conventional diameter implants; however, they are a significant and important augmentation to the original root-form implant concept. There is obvious evidence of the growing acceptance of small-diameter implants by both general practitioners and specialists.

Table.
Use of SDIs in Approximate Order of Decreasing Frequency of Use
Edentulous mandible
Removable partial denture
Edentulous maxilla (this use has higher failure rate than edentulous mandibles)
Augmentation of fixed prosthesis
Sole support of fixed prosthesis
Salvage of previously made prosthesis