Tony Daher

CAD/CAM fabricated complete dentures: concepts and clinical methods of obtaining required morphological data

The clinical impression procedures described in this article provide a method of recording the morphology of the intaglio and cameo surfaces of complete denture bases and also identify muscular and phonetic locations for the prosthetic teeth. When the CAD/CAM technology for fabricating complete dentures becomes commercially available, it will be possible to scan the denture base morphology and tooth positions recorded with this technique and import those data into a virtual tooth arrangement program where teeth can be articulated and then export the data to a milling device for the fabrication of the complete dentures. A prototype 3-D tooth arrangement program is described in this article that serves as an example of the type of program than can be used to arrange prosthetic teeth virtually as part of the overall CAD/CAM fabrication of complete dentures.

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

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.

A simple, predictable intraoral technique for retentive mechanism attachment of implant overdenture attachments.

A technique is presented for intraorally attaching two O-ring attachments to a mandibular complete denture. The technique involves fabricating and placing a mandibular denture with conventional procedures. Patients adapt initially to the complete denture. The attachments are then attached to the denture base with autopolymerizing acrylic resin. This technique provides a predictable method to achieve a tissue-supported and implant-retained overdenture.

Altered corrosion resistance from casting to stainless steel posts

Heat treatment during the burnout procedure may cause corrosion of the stainless steel post. This study was undertaken to determine whether alteration of the corrosion resistance of stainless steel posts occurs as a result of various simulated burnout procedures. Stainless steel posts were divided into five groups of five posts: group 1, control; 2, gypsum-bonded investment, bench cooled; 3, gypsum-bonded investment, quenched; 4, phosphate-bonded investment, bench cooled; and 5, phosphate-bonded investment, quenched. The posts were placed in individual containers of Ringers solution and observed at 30, 180, and 600 days. Scanning electron microscopy, energy dispersive x-ray spectroscopy, optical emission spectroscopy, and optical microscopy were used to evaluate the posts qualitatively and quantitatively. Investment and heat treatment altered the metallic structure of stainless steel posts. Prefabricated posts submitted to simulated burnout procedures had a noticeable reduction in corrosion resistance. Direct casting to stainless steel posts is contraindicated.

Time-saving method for the fabrication of a definitive cast for an implant- supported prosthesis

Conventional methods for fabricating an implant-supported overdenture or an implant-supported, fixed complete denture involve a series of patient visits. Because these visits occur in sequence, each visit depends on the accuracy of the previous visit and influences the accuracy of subsequent visits. Any procedural errors during these visits could compromise the fit of the definitive prosthesis. 1,2 The first step in achieving an accurately fitting, passive prosthesis requires capturing the 3-dimensional intraoral relationship of the implants with an impression. The accuracy of this impression procedure has an essential role in the prosthesis-implant adaptation. 3-5 Although several strategies have been suggested to enhance precision when making the definitive impression and cast for an implantsupported prosthesis, 6 it appears that absolute accuracy is currently not attainable. 7,8 A number of implant impression techniques have been described. 9,10 Most implant impression techniques have 1 feature in common, whereby impression material is present between the implant impression copings and the custom tray. The presence of this impression material produces resiliency in the system, and this lack of a rigid connection to the tray may result in an inaccurate cast. This article describes a time-saving, step-by-step technique designed to achieve 4 objectives with accuracy in a single clinical visit: (1) impression of the soft tissue, (2) impression and position of the implants, (3) registration of the maxillo-mandibular relationships, and (4) arrangement of the artificial teeth. The use of a verification jig 11 has confirmed the accuracy of this impression method.

Obtaining maxillomandibular records and definitive impressions in a single visit for a completely edentulous patient with a history of combination syndrome

Any attempt to reduce the number of dental visits for the fabrication of complete dentures is appreciated by both the dentist and the patient. This article illustrates clinical and laboratory procedures for making a 2-stage definitive impression combined with the recording of maxillomandibular relations in the same visit for a completely edentulous patient with maxillary anterior mobile soft tissues.

Importance of the Implant Screw Access Channel Location: Development of a Screw Access Channel Locating Device and Radiographic Integrator

There are occasions when the implant restoration requires removal. Cemented restorations may not allow easy removal. The clinician may then be presented with the challenge of accessing the abutment screw channel with a bur. This chapter deals with several ways to provide information that could be useful in determining where the access cavity should be made. These may expedite the procedure and limit any damage as a result, saving time and, potentially, expense.

Implant treatment record form.

The identification of different dental implants and restorative components is difficult when dental records do not include an inventory of implant components. An implant record form is described. The form should be filled out and retained in the patients chart for future use and implant maintenance visits.