Gus J. Livaditis

Etched castings: An improved retentive mechanism for resin-bonded retainers

Summary A technique was described for a retentive mechanism that etches the inner side of cast fixed partial denture frameworks. The etched metal ceramometal restoration was then bonded to the enamel surface utilizing the technique for acid etching enamel. Improved resin-bonded retainers provide innovative, conservative, and viable alternatives to traditional fixed prosthodontics.

Resin-bonded retainers. Part I: Resin bond to electrolytically etched nonprecious alloys

Nonprecious Ni-Cr casting alloys can be electrolytically etched to yield a highly retentive surface for micromechanical bonding of dental resins. The acid, current density, and etching time to achieve the retentive features are specific for each alloy. Conditions for etching one beryllium-containing and one non-beryllium-containing alloy are described. The tensile strength of a resin system to these alloys has been determined to be over two times the accepted value of the resin bond to acid-etched enamel.

The matrix impression system for fixed prosthodontics

This article describes the instrumentation, materials, and clinical procedures for the matrix impression system. The matrix impression system uses a custom matrix to control the sulcular environment and to deliver impression material to the subgingival parts to be impressed. It describes the four types of forces involved in gingival displacement during impressions, effective delivery of impression material with simultaneous sulcular cleansing, and simplification of complex impressions with or without segmentation. The application of the matrix impression system is described for making routine impressions and for some atypical problems. The article also provides a detailed description of the formation and design of the matrix.

Comparison of the new matrix system with traditional fixed prosthodontic impression procedures

This article compares the methods and effectiveness of traditional fixed partial denture impression systems, which includes the matrix impression system, in relation to the registration of the finish lines and sulci of tooth preparations in the formation of a full arch impression. Concepts relating to custom trays, retraction, homeostasis, sulcular cleansing, sulcular flange registration, configuration and strength, viscosity of elastomeric impression materials, and delivering the impression material into the sulcus are reviewed. Several concepts are questioned and alternative procedures are proposed. Forces that impact the gingival tissues and determine the success of the impression are briefly described.

Fabricating abutment crowns for existing removable partial dentures using custom resin clasp analogs

A universal approach for fabricating abutment crowns for existing removable partial dentures is described. A replica (analog) of the clasp assembly is generated and transferred to a traditional working cast, which includes the abutment die. The analog is incorporated into the working cast as a removable component to allow the formation of the crown contours. The article reviews in detail the procedures required to transfer accurately all the essential components and information from the mouth to the working cast while allowing the patient uninterrupted use of the removable partial denture. Prestabilizing the removable partial denture, creating the analog impression, avoiding errors due to soft tissue components, forming a precise analog base, selecting materials, generating a rigid resin analog, and prescribing a path of insertion and withdrawal to the analog are described. The method replicates all types of clasps and can generate all types of fixed prosthodontic retainers to function harmoniously with the existing partial denture.

Crown foundations with a custom matrix, composites, and reverse carving

This article describes a restorative technique for the formation of composite cores for artificial crowns. The procedure uses a semirigid matrix with reverse carving to form the cores on substantially compromised teeth. The matrix allows the placement of the composite under pressure to reduce voids and gaps and permits completion of multiple cores simultaneously. Reverse carving enables development of a common axis for multiple cores. The dentist can perform the tooth preparation for the crown at the time of the core restoration. The effort commonly applied to developing tooth morphologic features in the core can be invested instead in the formation of the interim restoration. The remaining tooth structure, pin or post placement, and location of the finish line can be evaluated with the insight of a crown foundation and not merely as a traditional restoration.

Gold-plating etched-metal surfaces of resin-bonded retainers

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Repair with a surveyed cast clasp while patient retains the partial denture

A technique is described that allows a removable partial denture with a broken clasp or a removable partial denture in which an abutment has been extracted to be restored by the reattachment of a new cast clasp component or a complete surveyed clasp assembly. The technique is applicable to most clasp designs and can include attachment to the acrylic denture base or the metal major connector. The technique is distinguished from other repair techniques by (1) providing a cast clasp replacement, (2) allowing the patient to retain the prosthesis during the repair, (3) generating a precisely formed surveyed clasp assembly by the laboratory, and (4) including an efficient transfer mechanism for the precision clasp created in the laboratory to be attached to the removable partial denture in the dental office. A two-step impression procedure is used to ensure proper relation of the partial denture to the abutments.

Indexing procedures for converting removable partial dentures after extractions while the patient retains the prosthesis.

A new indexing procedure is described for the conversion of removable partial dentures when extraction of additional teeth is planned. Advantages and disadvantages of the indexing procedure are reviewed and compared with traditional treatment options. The new procedure facilitates the use of dental laboratory expertise and facilities and allows the patient to retain the prosthesis throughout the process. A component that includes teeth, denture base segments, and wire or cast clasps is created by the laboratory and attached by the dentist during the extraction visit as a simple denture repair procedure. The procedure can also be used to convert an existing partial denture to an immediate complete denture. Required clinical and laboratory procedures are described.

Etched-metal resin-bonded intracoronal cast restorations. Part I: The attachment mechanism

Numerous attempts have been made to increase the adhesive qualities of the luting medium. Investigators have attempted to modify the metal surface, the tooth surface, the luting material, or combinations. Although investigations have achieved limited success, the adhesive cement remains an elusive goal of restorative dentistry. This article described the etched-metal attachment mechanism as an intermediate phase between luting medium and adhesive medium. However the bond of the resin to the etched enamel and etched metal is not adhesion. Nevertheless, the continuity and microscopic dimension of the mechanical bond mimics the adhesion desired. Until that adhesive material is developed, the bonding mechanism will serve as an effective substitute. The attachment mechanism described is the basis for an improved restoration. Resin-bonded retention can compensate for insufficient frictional retention or may completely substitute for frictional retention prescribed in a resin-bonded retainer prosthesis. Etched-metal procedures for intracoronal restorations permits conservative tooth preparation, greater retention, and improved support of remaining cusps.