A stent for presurgical evaluation of implant placement

Fumitaka Takeshita, DDS, PhD, a Tsutomu Tokoshima, DDS, ~ and Tsuneo Suetsugu, DDS, PhD c Faculty of Dentistry, Kyushu University, Fukuoka, Japan

This article describes a method of fabricating a stent with barium sulfate and stainless steel tubes for the accurate radiographic evaluation of the relationships of the predesigned superstructure, the scheduled implant placement, and the anatomic structure. The barium sulfate in the stent depicts the outline of the predesigned superstructure, and the stainless steel tubes indicate the intended location and inclination of the implants on the computed tomographic scans. In addition, this stent can be used as a surgical stent to guide the pilot drill to the desired site. (J Prosthet Dent 1997;77:36-8.)

T o evaluate the relationship between anatomic structures and the stent, investigators have reported ra- diographic presurgical evaluations with gutta-percha, 1- 4 metal spheres, s the baseline, 6 color chalk powder, 7 and barium sulfate 8 as radiopaque materials. Gutta-percha has an advantage because of its thermoplastici~ The advantages of metal spheres are its round shape, easy fabrication procedure, and ease of measurement of im- age magnification. Color chalk powder and barium sulfate materials are useful for observing the outline of the predesigned superstructure because of their radiopacity. Three-dimensional imaging with computed tomography (CT) or tomography is cxtremely helpful to evaluate the predesigned surgical plan. Several types ofradiopaque materials have been used to examine their difference in appearance on radiographic images.

Thc purpose of this article is to introduce procedures for making and using a stent with two types of radiopaque materials for the evaluation of implant place- ment.

P R O C E D U R E

1. Form wax sprues at the distal most teeth bilaterally of the approved trial wax denture and make a sili- cone (Exafine putty, GC Corp., Tokyo, Japan) im- pression. The stent is made of clear autopolymerized methyl methacrylate resin pour material (Palapress Valio, Kulzer, Germany).

2. After the clear stent is recovered from the impres- sion, remove all the teeth. Reposition the clear stent base in the impression (Fig 1). Mix powder that con- sists of a 4: I ratio of resin polymer and barium sul- fate with monomer. Pour the mixture into the tooth forms of the impression. (The degree of radiopacity of various mixture ratios is illustrated in Fig. 2.)

%ssistant Professor, Prosthetic Dentistry [i. L'Resident, Prosthetic Dentistry II. ~Professor and Chairman, Prosthetic Dentistry II.

Fig. 1. Clear acrylic resin stent duplicated from patient-ap- proved trial mandibular denture.

Fig. 2. Radiopacity of various mixture ratios. From left to right, Upper, 6(polymer):1 (monomer), 5:!, and 4:1 ; lower, 1:1, 2:1, and 3:1.

3. Cure the finished stent at 40 ° C tbr 20 minutes in the processor (Palamat, Kulzer, Germany), then recover and polish (Fig. 3).

4. Make the access holes to guide the first surgical drill

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TAKESHITA, TOKOSHIMA, AND SUETSUGU THE JOURNAL OF PROSTHETIC DENTISTRY

Fig. 3. Compietely cured radiopaque teeth. Fig. 5. Panoramic tomograph of stent with five stainless steel tubes in mandible of patient.

Fig. 4. Occlusa[ view of fabricated stent shows five stainless steel tubes in lingual plate.

Fig. 6. Reconstructed image of CT scan indicates relationship between anterior tooth and predesigned implant placement.

according to information obtained from the final cast and the provisional restoration.

5. Cut stainless steel tube sprues (Murakami Institute, Fukuoka, Japan) to a uniform height, place into the access hole, and retain with wax (Fig. 4).

6. Obtain a panoramic tomograph (Fig. 5) and a CT scan (Fig. 6) with the stent in place.

7. After the radiographs are obtained, remove the tube sprues.

8. Sterilize the stent so it (the access holes) can be used to guide the surgical drill to the desired site for im- plant placement.

D I S C U S S I O N

The barium sulfate in the stent depicts the outline of the predesigned superstructures, and the stainless robes represent the location and inclination of the intended implant placement. The powder barium sulfate and resin polymer mixture exhibit good radiopacity without ra- diologic artifact and the panoramic radiographs revealed the markers and the inclination.

The most important advantage is found in its use with a CT scan. The radiopaque markers located on

the reconstructed image of the CT scan can be clearly observed (Fig. 6). The clear image of the stainless steel tube demonstrates the predesigned inclination of im- plant placement, whereas the image of the barium sul- fate shows the position of the anterior teeth on CT scans. The location and inclination of predesigned im- plant placement in the stent can then be corrected as necessary before surgery according to the radiographic information. Other advantages of using this procedure with barium sulfate and stainless steel tubes are its ease of use, economy (inexpensive), and simple design of the materials.

R E F E R E N C E S

1. Verde MA, Morgano SM. A duabpurpose stent for the implant-supported prosthesis. J Prosthet Dent 1993;69:276-80.

2. Sonik M, Abrahams J, FaieHa RA. A comparison of the accuracy of periapical, panoramic, and computerized tomographic radiographs in locating the man- dibular canal. Int j Oral Maxil]ofac Implants 1994;9:455-60.

3. Pesun I J, Gardner FM. Fabrication of a guide for radiographic evaluation and surgical placement of implants, j Prosthet Dent "[ 995;73:548-52.

4. Stellino G, Morgano SM, Imbe[Ioni A. A dual-purpose, implan~ stent made from a provisional fixed partial denture. J Prosthet Dent 1995;74:212-4.

5. Lain EW, Ruprecht A, "fang J. Comparison of two-dimensional orthoradially reformatted computed tomography and panoramic radiography for dental implant treatment planning. J Prosthet Dent 1995;74:42-6.

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THE J O U R N A L O F PROSTHETIC DENTISTRY TAKESHITA, TOKOSHIMA, AND S U E T S U G U

6. Sethi A. Precise site location for implants using CT scans: a technical note. Int I Oral Maxillofac Implants 1993;8:433-8.

7. Espinosa Marino J, Alvarez Arena[ A, Pardo Cebal[os A, Fernandez Vazquez J, Ibaseta Diaz G. Fabrication of an implant radiologic-surgical stent for par- tially edentulous patient. Quintessence Int 1995;26:111-4.

8. Basten CH. The use of radiopaque templates for predictable implant place- ment. Quintessence Int 1995;26:609-12.

Reprint requests to: DR. FUMITAKA TAKESHiTA PROSTHETIC DENTISTRY [[ KYUSHU U NIVERSITY 3-1-1 MAIDASHI, H[GASHIKU FUKUOKA 812-82 JAPAN

Copyright © 1997 by The Editorial Council of The Journal of Prosthetic Dentistry.

0022-3913/97/$5.00 + 0. 10/1/78437

Hypermineralization of dentinal lesions adjacent to glass ionomer cement restorations. ten Cate JM, van Duinen RNB. J Dent Res 1995;74:1266-71.

Purpose. The purpose of this in vivo investigation was to compare the effects of glass ionomer cement (GIC), amalgam, and composite restorations on bordering dentinal carious lesions. Material and Methods. Bovine dentin specimens, 6 mm in diameter, were prepared 1 week before the in vivo investigation. By use of demineralization procedures, caries-like lesions were created in the dentin specimens. Cylindric preparations (2 mm diameter x 4 mm deep) were completed in each specimen close to the lesion. The preparations were filled with amalgam or composite (controls) or with one of two types of glass ionomer cements (test materials). In experiment I eight individuals participated; each person had one specimen that contained amal- gam and one specimen that contained GIC attached to the removable partial denture (on con- tralateral sides) with methyl methacrylate resin. A piece of retentive gauze was placed over each specimen to promote plaque formation. In experiment II, 12 individuals participated. Two speci- mens, one that contained composite and one that contained GIC material, were attached to their removable partial dentures as in experiment I. Gauze was not placed over these specimens. Par- ticipants in both experiments were asked to brush their teeth and removable partial dentures two times daily with a supplied combination fluoride toothpaste for the entire 12-week experimental period. They were instructed not to brush the attached specimens. All participants in this inves- tigation wore the removable partial dentures 24 hours per day. The specimens were retrieved, sectioned, and analyzed by microradiography. Student t tests were used for data analysis. Results. ExperimentI All sections from the amalgam group exhibited furthcr demineralization. The GIC group specimens, however, all exhibited hypermineralization of depths up to 150 ~m. Statistical analysis revealed a significant difference in mineral content between the two groups over the depth of the affected tissue (p < 0.01). Experiment H--GIC specimens exhibited remineralization or hypermineralization of the dentin. The composite specimens showed a large spread in the amounts of demineralization observed. Two of these specimens exhibited remineralization. In both experiments significantly higher mineral content was observed near the surface of the GIC specimens than either the amalgam or composite groups. No significant differences were noted between the two GIC materials. Conclusions. This study demonstrated that a significant potential for remineralization exists when GIC restorative materials are used intraorally. 29 R@rcnces.--DL Dixon

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