The quality of impressions for crowns and bridges: an assessment of the work received at three commercial dental laboratories. assessing qualities of impressions that may lead to occlusal discrepancies with indirect restorations.

There are few published studies that directly assess the quality of impressions for crowns and bridges in the UK. This paper considers aspects of impression quality with particular attention to factors causing potential occlusal discrepancies in the final restoration. To this end three dental laboratories were visited over a 3-month period. All impressions for conventional crown and bridgework that arrived on the days of the visits were examined and assessed against criteria defined on a custom-designed assessment form. A total of 206 impression cases were considered in this study. Flexible impression trays were used for 65% of working impressions. Their use was more common for NHS work than for private work. 31.9% of all alginate impressions examined were not adequately fixed to the tray. Visible contamination of impressions was not uncommon.

The quality of impressions for crowns and bridges: an assessment of the work received at three commercial dental laboratories. assessing the quality of the impressions of prepared teeth.

The literature is limited in studies directly assessing the quality of impressions for crowns and bridges in the UK. The aim of the study was to assess the quality of impressions for conventional crown and bridgework received by commercial dental laboratories. Three dental laboratories were visited over a 3-month period. All impressions for conventional crowns and bridges that arrived on the days of the visits were examined prior to any laboratory processing. A total of 206 impression cases were examined and assessed against criteria laid out in a custom-designed assessment form. Defects were commonly found in the recording of prepared teeth. Overall, 44.2% of impression cases were unsatisfactory. NHS impressions were more than twice as likely to be unsatisfactory compared to private impressions. If the results of this survey are typical then the general quality of impressions for fixed crown and bridgework is unacceptable. This is particularly true for work completed under the NHS contract.

An audit to assess the quality and efficiency of complete and partial dentures delivered by junior hospital staff.

The average number of visits for the construction of metal-based and acrylic dentures by junior hospital staff was 10 visits. Our hypothesis was that supervision would optimise the number of visits and reduce any need for remakes. The first audit cycle was retrospective and included all patients treated by SHOs in the Prosthodontics Department. The standard of care was compared to the British Society for the Study of Prosthetic Dentistry. The re-audit showed that the time taken to completion was reduced by 2 visits for both denture types and the average length of time was reduced from 31 weeks to 22 weeks. These improvements were directly related to improved supervision by senior staff.

The clinical performance of hybrid bridges delivered by undergraduate dental students: a retrospective study.

The aim of this study was to retrospectively analyse the clinical performance of hybrid bridges and their effect on periodontal health. All the bridges in this study were delivered by undergraduate dental students at the University Dental School and Hospital Cork. The recall protocol took the form of a questionnaire and a full clinical examination of the abutments, retainers and contra lateral control teeth. In all, 22 patients with 25 bridges were examined. The periodontal response was generally favourable and soft tissue alteration was minimal. The outcome of the performance hybrid bridges is not encouraging, as 32% (8) of the bridges failed and 68% (17) were in service with a mean duration of clinical service of 48 months.

Endodontics versus implantology: to extirpate or integrate?

An increasingly frequent dilemma in restorative dentistry is the question of whether to retain a badly damaged tooth and restore it, or to remove and possibly replace it. Given the ethical difficulties inherent in testing this question, it is unlikely that we will ever see a properly designed clinical trial that will provide an answer. One of the most strongly debated components of this question is whether endodontic treatment and restoration can compete with a dental implant-borne prosthesis in terms of longevity and success. In the current paper, the authors will attempt to: (i) answer this question based on our current understanding of the dental literature; and (ii) provide practitioners with guidelines that might be applied to their daily practices.

The quality of dental casts used in crown and bridgework.

OBJECTIVE: To assess the quality of dental casts used in crown and bridge construction. DESIGN: Observational cross-sectional study of dental casts. SETTING: Commercial dental laboratories and a university dental hospital laboratory in the UK. MATERIALS AND METHODS: A sample (n = 150) of working and opposing casts used for crown and bridgework prescribed by general dental practices and a dental hospital were sampled from two commercial dental laboratories and an 'on-site' university dental hospital laboratory respectively. A simple '3 point' assessment scale of quality (good, fair and poor) was used to categorise the casts depending on the clarity of reproduction of soft and hard tissues. RESULTS: The quality of opposing casts used for articulation purposes was significantly better (P<0.001) than that of the working casts. In addition it was found that for working casts the quality in the preparation area(s) was significantly better (p<0.001) than that in areas remote from preparation(s) in the same arch. In general, the quality of casts in the incisal or occlusal surfaces was better than the buccal and lingual surfaces. CONCLUSIONS: This study has demonstrated that variation exists in the quality of casts used in crown and bridgework, specifically those used in the construction of indirect restorations and also those used for articulation purposes. This study highlights the need for clinicians to exercise continued vigilance with crown and bridge impressions, and casts, particularly in areas away from the prepared teeth.

[Clinical study of zirconium oxide bridges in the posterior segments fabricated with the DCM system]. / Klinische Studie von Zirkonoxidbrücken im Seitenzahngebiet hergestellt mit dem DCM-System.

Today's dental reconstructive therapeutic concepts require restoration of high esthetic quality and excellent biocompatibility. Full ceramic reconstructions accomplish these requirements but only for anterior teeth and premolars. For all-ceramic bridges the mechanical strength was insufficient to withstand the posterior chewing forces. Frequently the interdental connectors cracked, and the only way to prevent these fractures was to overconture the connectors to a size of approx. 16 mm2. The high-tech ceramic zirconia is a potential alternative for three-to five-unit full ceramic bridges in the functionally loaded posterior segments. Experimental zirconia bridges which were fabricated using the DCM system (Direct Ceramic Machining System at the ETH Zurich, were tested in vitro. The frameworks were digitally enlarged by 20% and were easily milled from a presintered yet porous zirconia blank. After the milling process, the framework was densely sintered and shrank to its original size. Due to these positive in-vitro results a clinical investigation was started. 22 veneered zirconia bridges were luted; 19 molars and 25 premolars were prepared. The connectors, max. 7 mm2, of all these bridges, have been functionally loaded by antagonists. After a mean observation time of 385 days (307 days to 488 days), all 22 bridges did not show any cracks in the framework or in the veneering porcelain. The patients commented particularly on the low heat conduction rate of zirconia. The only endodontic problem which occurred could not be directly connected to the type of bridge framework. The reliability of zirconia bridges in this investigation was connected to the DCM-Process. No statement about other zirconia-systems can be made on the results of this study.

CONSTRUCCION DE PUENTES CON EL SISTEMA UDA

El próposito principal del empleo del sistema de remplazo de dientes UDA si se lo usa correctamente es el de preservar y optimizar la condición fisiológica y el comportamiento masticatorio del sistema oral. El sitema UDA (Anclaje dental Universal) puede usarse en las áreas anterior y posterior y es adecuado para el remplazo de brechas simples y múltiples. Lo nuevo y actualizado en este concepto es que no sólo es una forma de evitar que los dientes pilares soporten fuerzas sumamente altas, sino que tambien ortoga posibilidades de combinar esta técnica con otras aplicaciones protéticas, sobre todo, la reversibilidad del procedimiento de UDA deja el camino abierto para progresos futuros. Los promisorios resultados, fruto de años de investigación clínica y experimental en diversas universidades de Europa, respaldan la exitencia de una técnica absolutamente justificada en los ámbitos médico. biológico, uso del sistema UDA y que son la preservación de la solidez de la sustancia del diente y el tejido periodontal, así como tambien faltas de interferencia con la oclusión natural, que son aspectos considerados prioritarios, asimismo, el aspecto económico del sistema se adapta a las necesidades del paciente

The influence of the impression tray on the accuracy of impressions for crown and bridge work--an investigation and review.

OBJECTIVE: To evaluate the accuracy of working casts for crown and bridge restorations made from twin mix putty/wash silicone elastomeric impression materials using different types of stock tray. DESIGN: A master cast was made from ivorine teeth in a mandibular model. Three teeth were prepared for full crown restorations to simulate a single unit and a three unit bridge. Impressions were taken using four different types of impression tray and two different viscosities of silicone putty, together with a wash. Full metal crowns were constructed and seated on duplicate master casts and measurements made of the marginal discrepancies. SETTING: The work was carried out in a dental technology laboratory in a university department of restorative dentistry in 1995/1996. RESULTS: Metal and rigid plastic impression trays showed the least discrepancy (about 50 microns), the latter slightly greater with the normal putty than the soft one. Impressions taken with flexible plastic trays produced considerable discrepancy with both putties, approximately 210 microns and 180 microns respectively. CONCLUSIONS: Metal and rigid plastic stock trays give greater accuracy in the putty/wash silicone twin mix impression technique compared with flexible plastic ones for crown and bridge work. Those using the latter should be aware of their shortcoming in this respect.

The quality of impressions for crowns and bridges received at commercial dental laboratories.

OBJECTIVE: To determine the quality of impressions for crown and bridge work made in general dental practice. DESIGN AND SETTING: All impressions for crown and bridge work which had been sent to four commercial dental laboratories in the UK were assessed by two examiners, each laboratory being visited on two occasions. MATERIALS AND METHODS: 290 cases which had been received by the laboratories on the days of the visits were assessed for a number of factors related to quality. There was no selection or rejection--all impressions received were examined. RESULTS: Flexible plastic trays were used for the majority of working impressions for crown and bridge work in general dental practice (72%), many had been re-used (> 13%), defects in the recording of the prepared teeth were common, and cross infection control was not routine. CONCLUSIONS: Quality standards for impressions for crown and bridge work in general dental practice in the UK are a cause for concern if the sample of cases seen in this study is typical.

SISTEMA DE OVERDENTURE CON RETENCION MAGNETICA EN RESTOS RADICULARES PARA PROTESIS PARCUAK RENIVIBLE

Las sobredentaduras Parciales Removibles, constituyen una opción más dentro de las restauraciones parciales removibles. Permiten la distribución de las fuerzas verticales, a través de la base de la prótesis. Las Sobredentaduras Parciales Removibles, en base a dispositivos magnéticos pueden ser retiradas e instaladas con facilidad, por parte del paciente. Para el uso de Sobredentaduras, se debe realizar una evaluación periodontal detallada. Las Slbredentaduras Parciales Removibles, son una modalidad terapéutica excelente para preservar el proceso alveolar. Al retener la raíz o raíces naturales, por debajo e la Sobredentadura Parcial Removible, logramos conservar la sensibilidad por la presencia de ligamento periodontal. Este tipo de Sobredentaduras no presentan alteraciones, puesto que los dispositivos intraradiculares no proporcionan movimento radicular

[Guidelines for occlusions and articulation. Part 2. Crown and bridgework on dental implants]. / Richtlijnen voor occlusie en articulatie. Deel 2. Kroon- en brugwerk op implantaten.

It is generally accepted that one should minimize horizontal forces or horizontal components of more vertically directed forces when loading dental implants. This has its implications for the choice of the occlusion concept. In this article various occlusal concepts aimed at different types of fixed prostheses on dental implants are discussed. When possible canine guided articulation or group function must be strived for. It is stressed that detailed pre-implantological diagnostics and treatment planning are essential to achieve high treatment standards.