Comparison of convergence angles achieved in posterior teeth prepared for full veneer crowns.

This study compares the convergence angle of preparations for posterior gold crowns made by fourth/ fifth year undergraduate dental students, clinical teaching staff and general dental practitioners. Sixty dies were cast from impressions previously taken of clinical preparations by clinicians within each of the four groups. Each die was trimmed and sectioned in both mesio-distal and bucco-lingual planes before being projected using an overhead projector, thereby enabling the convergence angle silhouette to be measured. The results show the greatest convergence angle range to be produced by the least experienced students (10 degrees - 82 degrees). However, no significant difference (p > 0.05) was found when students with one further year of experience were compared to experienced staff. The degree of conformity to the ideal taper (4 degrees - 14 degrees) was no greater than 50% for any of the groups.

Glass/ceramic/refractory techniques, their development and introduction into dentistry: A historical literature review.

This review considered the development of glass, ceramic, refractory materials, and techniques over a period of 25,000 years, from the time of stone-age man to their introduction into dentistry. Currently a wide variety of all-ceramic dental restorations are provided using alumina-reinforced, leucite-forming, and novel glass and ceramic materials along with a range of refractory materials and associated techniques. However, some of the problems of dimensional and thermal change experienced by early craftsmen still persist during current laboratory fabrication techniques. Early English archaeological and dental publications were obtained through the Archaeology Education Department of the British Museum in London and the Archives of the British Dental Association Library. More recent peer-reviewed articles published from 1966 to the present were obtained through MEDLINE.

Comparison of the replicability of routinely used centric relation registration techniques.

PURPOSE: This study was conducted to determine statistically the most repeatable mandibular position of 3 centric relation methods. MATERIALS AND METHODS: Three centric relation recording methods commonly reported in the literature were selected: bimanual mandibular manipulation with a jig, chin point guidance with a jig, and Gothic arch tracing. Fourteen healthy adult volunteers (7 males and 7 females), with an average age of 26.61 +/- 4.20 years and no history of extractions, temporomandibular joint dysfunction, or orthodontic treatment, were selected for the study. Accurate casts were mounted on an articulator (Denar D4A) by means of a facebow and maximum intercuspation silicone registration record. A mechanical 3-dimensional mandibular position indicator was constructed and mounted on the articulator enabling the operator to analyze the mandibular positions in 3 spatial axes (x, anteroposterior; y, superoinferior; z, mediolateral shift). Each centric relation method was recorded four times on each subject (at baseline, 1 hour, 1 day, and 1 week at approximately the same time of day). Records were transferred to the articulator, and data were extracted using a stereomicroscope modified to accept the mandibular position indicator. RESULTS: Variability within subjects ranged from 0.03 mm (left-side z axis for the bimanual method) to 1.6 mm (left-side y axis for the Gothic arch method). To indicate the least variable (most repeatable) method a comparison was made using the F test. The bimanual method was the most consistent, showing between 10.11 (p = 1) and 0.438 (p = 0.005) times less variation than the Gothic arch method (the least consistent). The repeatability of the chin point guidance method was somewhere between the other 2 methods. CONCLUSIONS: The results of this study showed that of the 3 centric relation methods evaluated, the bimanual manipulation method positioned the condyles in the temporomandibular joint with a more consistent repeatability than the other 2 methods, whereas the Gothic arch was the least consistent method.

A clinical overview of removable prostheses: 5. Diagnosis and treatment of RPD problems.

This, the fifth and final article in the series, addresses the diagnoses and treatment of problems which may arise following provision of removable partial dentures (RPDs). These include difficulties seating the denture, pain and discomfort, looseness and functional problems.

A clinical overview of removable prostheses: 4. Technological considerations when designing removable partial dentures.

This fourth article in a series concerning the prescription of removable partial dentures is a précis of the technical aspects of RPD construction, commencing with the definitive or 'working' impressions, although all impressions ought to be considered as 'working' impressions.

A clinical overview of removable prostheses: 2. Impression making for partial dentures.

This, the second article in a series on the prescription of removable partial dentures, will deal with the issue of primary impression and primary casts for partial dentures. The principles of definitive impressions and master cast planning will be described.

A clinical overview of removable prostheses: introduction.

This series of articles has been written with the intention of simplifying the processes involved in the prescription of removable partial dentures. The scene is set in this introduction, and the first article addresses basic clinical and patient-related factors involved in decision-making before commencing active prosthodontic treatment. The second paper will outline a variety of impression techniques for primary and definitive impressions, while the third discusses designing principles. The fourth article is a brief overview of some technological aspects of removable partial denture-making and the fifth attempts to provide a useful guide showing how to diagnose and manage common clinical problems associated with removable partial dentures.

A clinical overview of removable prostheses: 1. Factors to consider in planning a removable partial denture.

This is the first article in a series on the prescription of removable partial dentures. It addresses basic clinical and patient-related factors involved in decision-making before commencing active prosthodontic treatment. Further papers will outline a variety of impression techniques for primary and definitive impression, discuss designing principles, give an overview of some technological aspects of removable partial denture-making and provide guidelines on how to diagnose and manage common clinical problems associated with removable partial dentures.

A clinical overview of removable prostheses: 3. Principles of design for removable partial dentures.

Removable partial dentures (RPDs) should not be made for patients unless they are necessary. Most partial dentures have the potential to cause some damage to the teeth and supporting tissues, however well they are designed and constructed; the criteria for selecting such devices were described in a previous article. In general there is merit in, wherever possible, reducing tissue coverage as much as possible when RPDs are being planned. This article, the third in a series on the prescription of RPDs, discusses the design principles involved.