The use of digital photographs to locate implant abutment screws for implant-supported cement-retained restorations

Abstract

aAssociate Professor, Department of Restorative Dentistry, Loma Linda University. bProfessor and Director, Division of Postdoctoral Prosthodontics, Department of Restorative Sciences and Biomaterials, Goldman School of Dental Medicine, Boston University. (J Prosthet Dent 2008;100:238-239) Cement-retained implant-supported restorations are commonly used, and have advantages and disadvantages. Retention of implantsupported crowns by using cement eliminates unesthetic screw access openings. Another advantage is the potential to compensate for minor dimensional discrepancies in the fit of multiunit restorations by using cement and the cement space.1 However, cemented implant-supported crowns are more difficult to retrieve for subsequent maintenance.1 If the location of the access screw opening is not known, the removal of a cement-retained implant-supported restoration with a loose abutment screw or fractured porcelain may result in difficulties and perhaps irreversible damage to the restoration or the abutment. Several methods have been described in the literature to provide retrievability of cemented implant-supported restorations. One approach is the use of provisional cement. The argument that cements of differing retentive capacities can be titrated to somehow function as effectively as screws for either removal or retention has been challenged.1 A second method is the use of set screws that allow a retrieval screw to be placed in a position where a displacing force can be applied in the direction of the abutment to break the cement seal and allow removal of the restoration.2 The disadvantage of this technique is the access opening in the occlusal surface for the extra screw needed to remove the crown. A third approach is the placement of a well-defined small ceramic stain on the occlusal surface of a posterior implant-supported restoration in conjunction with a periapical radiograph for evaluating the implant angulation. This method provides a reliable landmark for locating the screw-access opening of the abutment.3 However, this technique is limited to posterior implant-supported restorations only, and the ceramic stain can only be placed in nonesthetic areas. A fourth approach is the use of a secondary lingual locking screw in the restoration for retention and retrievability.4 A fifth approach is the use of cylindrical guide holes in the lingual aspect of implant-supported restorations for the removal of cemented superstructures.5 A removing driver placed in these guide holes, when turned, creates a shear force and thereby raises and unseats the restoration. A sixth method is the use of a vacuum-formed clear retaining screw location guide, similar to a surgical guide, made on a cast. The location guide assists in locating the implant abutment access chamber and abutment retaining screw to facilitate the removal of a cemented implant-supported restoration.6 The disadvantage of this technique is the need to retain the original implant and abutment level casts. This article describes an uncomplicated technique to facilitate the removal of a cemented implant-supported restoration. This technique has 2 advantages: it will not damage the implant abutment, and the patient’s visit will be relatively brief. After seating the implant abutment(s) (Cast-to Gold Abutment, engaging; Zimmer Dental, Carlsbad, Calif ) and the implant-supported restoration(s), a series of digital photographs are made with a digital camera (Dine Pentax Digital Solution; Lester A. Dine, Inc, Palm Beach Gardens, Fla) with the use of the intraoral macro setting.