A simple, permanent index for abutment screw access for cemented implant-supported crowns

A simple, permanent index for abutment screw access for cemented implant-supported crowns Edward E. Hill, DDSa University of Mississippi School of Dentistry, Jackson, Miss Cement-retained implant-supported crowns have advantages over screw-retained restorations, including ease of fabrication, lower cost, passivity of fit, and the opportunity to achieve optimal esthetics and occlusion.1 A significant disadvantage is retrievability, especially if crowns are luted with a definitive cement.2 Rajan3 described a technique in which a vent/screw access hole was included in the fabrication of the definitive crown, and the restoration was luted to the abutment prior to placement intraorally. At insertion, the screw channel was filled with gutta percha and the occlusal hole sealed with composite resin. Use of a special removing driver placed in a lingual guide hole of the restoration also has been suggested.4 Doerr5 described fabrication of a vacuum-formed matrix with holes corresponding to abutment positions to help identify access channel locations if needed later. The placement of a hole to access a screw in an implant-supported cemented restoration must be done carefully to minimize overall destruction and loss of occlusal contacts that would require refabrication and possibly a new abutment. A simple technique for determining future access hole position, which is similar to that of Doerr5 but uses a different approach and material, is described.

Fig. 1. Determine center of abutment.

PROCEDURE 1. Determine the external position of the center of the top of the abutment screw access channel(s) on the definitive restoration prior to cementation using a gold thickness gauge (Iwanson Spring Caliper; Hu-Friedy, Chicago, Ill) (Fig. 1). 2. Place a 2-mm bead of baseplate wax (TruWax; Dentsply Intl, York, Pa) or any other firm wax to mark the potential screw access position (Fig. 2). 3. Make a silicone putty index (Coltene Lab-Putty; Coltene/Whaledent, Mahwah, NJ) of the occlusal aspect of the restoration with the wax bead(s) (Fig. 2). 4. Store the matrix with the casts or treatment record of the patient. 5. If access to an abutment screw must be gained in the future via a hole in the restoration, perforate the bead hole indention(s) and place the matrix over the a

Associate Professor, Department of Care Planning and Restorative Sciences. J Prosthet Dent 2007;97:313-4.

MAY 2007

Fig. 2. Use wax to mark potential access hole position and make silicone putty index (below).

restoration to mark the exact entry point and size of the access hole. REFERENCES 1. Michalakis KX, Hirayama H, Garefis PD. Cement-retained versus screwretained implant restorations: a critical review. Int J Oral Maxillofac Implants 2003;18:719-28. 2. Chee W, Felton DA, Johnson PF, Sullivan DY. Cemented versus screw retained prosthesis: which is better? Int J Oral Maxillofac Implants 1999; 14:137-41. 3. Rajan M, Gunaseelan R. Fabrication of a cement-and screw-retained implant prosthesis. J Prosthet Dent 2004;92:578-80. 4. Okamoto M, Minagi S. Technique for removing a cemented superstructure from an implant abutment. J Prosthet Dent 2002;87:241-2. 5. Doerr J. Simplified technique for retrieving cemented implant restorations. J Prosthet Dent 2002;88:352-3.

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Reprint requests to: DR EDWARD E. HILL DEPARTMENT OF CARE PLANNING AND RESTORATIVE SCIENCES UNIVERSITY OF MISSISSIPPI SCHOOL OF DENTISTRY 2500 NORTH STATE ST. JACKSON, MS 39216 FAX: 601-984-6039 E-MAIL: [email protected]

Noteworthy Abstracts of the Current Literature

HILL

0022-3913/$32.00 Copyright Ó 2007 by The Editorial Council of The Journal of Prosthetic Dentistry.

doi:10.1016/j.prosdent.2007.03.001

Use of Er:YAG laser to improve osseointegration of titanium alloy implants—a comparison of bone healing Kesler G, Romanos G, Koren R. Int J Oral Maxillofac Implants 2006;21:375-9.

Purpose: The objective of this study was to compare the osseointegration of implants in rats in sites prepared with an Er:YAG laser with osseointegration in sites prepared using a conventional drill by assessing the percentage of bone-implant contact (BIC). Materials and Methods: Osteotomies were prepared with an Er:YAG laser in the tibiae of 18 rats (the test group) and drill-prepared with a 1.3-mm-wide surgical implant drill at 1,000 rpm with simultaneous saline irrigation in the tibiae of another 18 rats (the control group). Acid-etched titanium alloy implants (2 3 8 mm) were placed in the tibiae, engaging the opposite cortical plate. The Er:YAG laser was used with a regular handpiece and water irrigation (spot size, 2 mm; energy per pulse, 500 to 1,000 mJ; pulse duration, 400 ms; and energy density, 32 J/cm2). Nine animals from each group were sacrificed after 3 weeks of unloaded healing; the remainder were sacrificed after 3 months. The tissues were fixed and prepared for histologic and histomorphometric evaluation. Results: Statistical analysis showed significant differences between the 2 groups at both 3 weeks and 3 months. After 3 weeks of unloaded healing, the mean BICs (6SD) were 59.48% (621.89%) for the laser group and 12.85% (611.13%) for the control group. Following 3 months of unloaded healing, the mean BICs (6SD) were 73.54% (611.53%) for the laser group and 32.6% (66.39%) for the control group. Discussion: Preparation of the implant sites with the Er:YAG laser did not damage the interface; the healing patterns presented were excellent. Conclusions: Based on the results of this study, it may be concluded that the Er:YAG laser may be used clinically for implant site preparation with good osseointegration results and bone healing and with a significantly higher percentage of BIC compared to those achieved with conventional methods.—Reprinted with permission of Quintessence Publishing.

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