A technique to enhance closed surgical stents for implant placement
BARRY F. McARDLE, D.M.D.
When the angulation of implant position is absolutely critical, using a closed surgical stent often is preferred as a guide for placement.1 An oral surgeon colleague once remarked that he considered the standard use of acrylic resin, with or without metal drill guide sleeves, in closed stent fabrication limiting.2 Neither option would allow him even the slightest eccentricity with his twist drill; with the sleeves, it was impossible, and, without them, he risked disrupting the material. If the center channel made through the stent by a general dentist or prosthodontist to create ideal prosthetic alignment did not permit suitable implant positioning, the stent was useless.
I use a technique for creating closed surgical stents that uses a flexible intermediate restorative material to give the surgical dentist more leeway in this type of situation.
I often fabricate three guide-cores using this technique, making successively wider center channel diameters to further aid the dentist in using progressively larger-bore twist drills during implant placement.
TECHNIQUE
To construct a closed surgical stent for implant patients, I first take impressions and interocclusal registrations. Then I wax a denture tooth onto the endentulous portion of the articulated casts and contour it to the correct occlusion. Next, I vacuum-mold the stent material onto the cast and trim the stent to size. Finally, most dentists add acrylic resin when producing the closed stent.
An alternative to this procedure I use is to manufacture the stent as I outlined previously until the trimming is done. At that point, I remove the denture tooth from the model and fill the corresponding area in the stent with Fermit (Ivoclar North America, Amherst, N.Y.), which is a light-cured intermediate restorative material that still is somewhat flexible when set. (I had extensive experience using Fermit for provisional partial coverage indirect restorations—inlays and onlays—before I developed this technique.) In my experience, Fermit-N (Ivoclar North America, Amherst, N.Y.), another light-activated intermediate restorative material, is too rigid when cured to use in fashioning this type of stent.
After filling the area of the stent, I seat the stent onto the cast and pare away any excess material extruding beyond its borders with a wax spatula. I light-cure the material from the buccal, occlusal and lingual aspects, as there is a considerable bulk of material inside the stent that may not be amenable to full curing with a single light exposure. I then remove the stent from the cast and cure the material from the tissue surface aspect. After the material has been contoured and cured inside the stent, I refer to it as a guide-core (Figure 1
).
The material’s flexibility and compositional difference from both the stone of the model and the thermoforming stent material allow me to remove the guide-core from the cast and stent. After removal, I trim away with scissors or a scalpel any superfluous material that may have issued onto the adjacent occlusal surfaces of the cast’s stone teeth. This can be accomplished best by reseating the guide-core on the cast and removing it several times to achieve the proper contours. Using this technique, virtually no abrasion of the stone teeth will occur. I reseat the guide-core with the stent on the cast and sink my center channel through it to serve as an index for the surgical dentist’s twist drill (Figure 2). Then, I store the guide-core and stent on the model until delivery to the surgical dentist at the time of the surgical appointment.
I often fabricate three guide-cores using this technique, making successively wider center channel diameters to further aid the surgical dentist in using progressively larger-bore twist drills during implant placement. The unique properties of Fermit, however, often will allow a twist drill larger than the first one to be used through the same guide-core without loss of stability. The flexibility of Fermit allows for a slightly off-center pass through it without loss of integrity. That and the intimate adaptation of this material to all areas within and adjacent to the edentulous site allow for a versatility that is not possible when acrylic resin is used.
These implant cases can be viewed in the mouth and on the cast with or without the stent or guide-core in place. This provides the surgical dentist with a unique perspective on the implant cases using closed surgical stents constructed using the described technique.
CONCLUSIONS
Fashioning closed stents using Fermit takes less time than it would using acrylic resin; however, material costs will be somewhat higher. I believe that the added confidence this technique will afford the surgical dentist and the improved result that such confidence will bring about are well worth the increased cost.
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FOOTNOTES
Dr. McArdle is a general dentist in private practice, 118 Maplewood Ave., The Captain Moses House, Suite B-7, Portsmouth, N.H. 03801, e-mail "drmcardle{at}mcardledmd.com". Address reprint requests to Dr. McArdle.
The author thanks Dr. Louis F. Clarizio for his advice in the development of this technique and Dr. Craig M. Leffingwell for his assistance in the preparation of the manuscript.
REFERENCES
- Orenstein IH. The surgical template: a prescription for implant success. Implant Dent 1992;1(3):182–4.[Medline]
- Kennedy BD, Collins TA Jr., Kline PC. Simplified guide for precise implant placement: a technical note. Int J Oral Maxillofac Implants 1998;13(5):684–8.[Medline]
