Ira D. Zinner

An analysis of the development of complete denture impression techniques

Abstract Sixty-eight textbooks published in English since 1845 have contained references to impression making. References in these volumes to biologic, psychologic, behavioral and material science, and to clinical procedures were recorded. These notations were then tabulated into four eras for statistical analysis. There were a total of 9, 005 references in the various categories. For each classification an index of frequency was calculated (Figs. 1 to 9). The index of frequency is the number of times an item was recorded in an era divided by the number of books in that era. For example, under the category of pressure phenomena (Fig. 3), a reference to “equalization of pressure” in the 1900 to 1929 era was recorded 33 times. There were a total of 22 books published in this era. Therefore the index of frequency for this item in the second era is 33 ÷ 22 or 1.5 (Fig. 3). The index of frequency gives a measure of the interest in impression making (Table I). An increase in the index of frequency for compressive impressions, border molding, and denture extension was recorded over four eras. References to closed mouth impressions showed a smaller increase. No increase in references to displaceable ridges and facial contours was seen over the four eras, and a decrease was noted in the index of frequency for rebase impressions (Fig. 1). The index of frequency increased greatly in various categories of oral muscle and tissue movements over the four eras as authors became more sophisticated in the biologic concepts of impression making (Fig. 2). Similarly there were large increases in the index of frequency for many subcategories of physical phenomena—surface area coverage, retention, denture extension, and soft tissue displacement (Fig. 3). On the other hand, references to atmospheric pressure, peripheral seal, posterior palatal displacement, and border tissue adaptation showed little or no trends over the four periods of time. Index of frequency for references to anatomic areas remained fairly constant for nonspecific sites but showed an increase in references to specific bones, muscles, and oral spaces (Figs. 4 to 6). References to modeling compound and plaster showed large increases, especially in the later era, despite the introduction of new materials such as zinc oxide-eugenol paste, alginates, reversible hydrocolloids, thiokol rubbers, and silicones (Fig. 7). There were very few references to pathology, histology, and behavioral aspects of impression making and no trend was observed over the four eras (Figs. 8 and 9). The history of impression making shows that most of the significant advances occurred before 1930. Basic principles of pressure, maximum extension of the denture base over the denture-bearing area, and equal distribution of pressure were first introduced in the era 1845 to 1899. The most significant advances in the art were developed in the second era, 1900 to 1929. Advances in the accuracy of impression techniques and an increase in the methods of border molding and obtaining a posterior palatal seal were among the major innovations in this era. The era from 1930 to 1949 saw great advances in the knowledge of the anatomy of the oral and perioral tissues as they affect impression making. The use of immediate denture techniques and the introduction of several new materials such as zinc oxide-eugenol paste and the hydrocolloids were also noted. The fourth era saw progress in the biologic aspects of denture impression making. There was an appreciation of the rationale for border molding and an awareness of the muscles and how they relate to complete denture impression techniques. The importance of an in-depth review of impression making lies in the assessment of the historical value of all factors. The categorization for these factors into their respective physical, biologic, and behavioral areas can show their relativity to the time in which they were discussed and taught as well as to their assigned importance.

PROVISIONAL AND DEFINITIVE PROSTHESES FOLLOWING SINUS LIFT AND AUGMENTATION PROCEDURES

Sinus lift and augmentation procedures with simultaneous insertion of cylindrical root form implants can be used to treat the atrophic posterior maxilla. The long-term use of a second stage provisional prosthesis is emphasized. The recommended metal-reinforced acrylic resin provisional restoration allows treatment and/or removal of a failing implant and progressive loading before fabrication of the definitive prosthesis. Modifications in prosthesis fabrication after sinus lift surgery and augmentation procedures are discussed. (Implant Dent 1994;3:24—28)

Semiprecision rest system for distal-extension removable partial dentures☆

The history of the nonlocking type of intracoronal semiprecision rest has been traced from its origins with Neurohr in 1930, up to its present use as the Thompson dowel rest. The advantages of the use of this deep rest design and the clasp arm design for primary retention have been discussed. The Blatterfein modification of the lingual clasp arm has been introduced to overcome the problems of breakage and lack of stabilization which are present with the Thompson, Van Dam, and Wands designs.

Augmenting the maxillary sinus for implants: report of 27 patients

A method for restoring the posterior portion of the maxilla with a simultaneous composite alloplastic sinus lift graft and placement of press-fit implants is presented. Sinus grafting is needed because of minimal remaining alveolar bone. The composite graft material uses a combination of demineralized freeze-dried cortical bone and Interpore 200 hydroxyapatite. Since 1987, 45 sinus grafts with simultaneous placement of 111 root-form implants have been performed for 27 patients. None of the 76 restored implants have been lost. Complications were encountered in 2 patients (4 sinuses) who were heavy smokers. Antibiotics were administered, symptoms subsided, and the implants integrated.

Fabricating a nonrotational angulated abutment for a single-tooth prosthesis.

The fabrication of a custom waxed and cast nonrotational angulated abutment will be described. Most manufacturers of implant components fabricate angulated abutments for multiunit retrievable prostheses. However, they do not manufacture any components for a single unit that is screw retained. This article covers a step-by-step technique that was developed in an attempt to resolve this problem.

Clinical management of abutments with intracoronal attachments.

A method of preparing teeth to accommodate intracoronal attachments is presented. The resulting prosthesis incorporates a fixed partial denture with physiologically contoured crowns and a removable partial denture with a precisely determined path of insertion. These techniques stress the importance of surveyed diagnostic casts and coordinated tooth preparations for artificial crowns to facilitate treating complex cases.

A modification of the Thompson dowel rest for distal-extension removable partial dentures

A prefabricated Thompson dowel rest semiprecision attachment system for distal-extension removable partial dentures deserves consideration in the treatment planning of periodontally involved dentitions. It is a system that provides for rotation and therefore stress-breaking with controlled movement. Many other stress-breaking systems provide for rotation without specific control. In addition, the Thompson dowel rest system is the only stress-breaker that is intracoronal not extracoronal. This prefabricated system offers facilitation of laboratory procedures, eliminates the need for utilization of gold for dowels, reduces the size of the rest seats, and aids in the preservation of the integrity of the hard and soft supporting tissues.