Quality Evaluation of Zirconium Dioxide Frameworks Produced in Five Dental Laboratories from Different Countries.

PURPOSE: The aim of this study was to assess and compare quality as well as economic aspects of CAD/CAM high strength ceramic three-unit FDP frameworks ordered from dental laboratories located in emerging countries and Switzerland. MATERIAL AND METHODS: The master casts of six cases were sent to five dental laboratories located in Thailand (Bangkok), China (Peking and Shenzhen), Turkey (Izmir), and Switzerland (Bern). Each laboratory was using a different CAD/CAM system. The clinical fit of the frameworks was qualitatively assessed, and the thickness of the framework material, the connector height, the width, and the diameter were evaluated using a measuring sensor. The analysis of the internal fit of the frameworks was performed by means of a replica technique, whereas the inner and outer surfaces of the frameworks were evaluated for traces of postprocessing and damage to the intaglio surface with light and electronic microscopes. Groups (dental laboratories and cases) were compared for statistically significant differences using Mann-Whitney U-tests after Bonferroni correction. RESULTS: An acceptable clinical fit was found at 97.9% of the margins produced in laboratory E, 87.5% in B, 93.7% in C, 79.2% in A, and 62.5% in D. The mean framework thicknesses were not statistically significantly different for the premolar regions; however, for the molar area 4/8 of the evaluated sites were statistically significantly different. Circumference, surface, and width of the connectors produced in the different laboratories were statistically significantly different but not the height. There were great differences in the designs for the pontic and connector regions, and some of the frameworks would not be recommended for clinical use. Traces of heavy postprocessing were found in frameworks from some of the laboratories. The prices per framework ranged from US$177 to US$896. CONCLUSIONS: By ordering laboratory work in developing countries, a considerable price reduction was obtained compared to the price level in Switzerland. Despite the use of the standardized CAD/CAM chains of production in all laboratories, a large variability in the quality aspects, such as clinical marginal fit, connector and pontic design, as well as postprocessing traces was noted. Recommended sound handling of postprocessing was not applied in all laboratories. Dentists should be aware of the true and factitious advantages of CAD/CAM production chains and not lose control over the process.

Electronic laboratory quality assurance program: A method of enhancing the prosthodontic curriculum and addressing accreditation standards.

STATEMENT OF PROBLEM: An electronic quality assurance (eQA) program was developed to replace a paper-based system and to address standards introduced by the Commission on Dental Accreditation (CODA) and to improve educational outcomes. This eQA program provides feedback to predoctoral dental students on prosthodontic laboratory steps at New York University College of Dentistry. PURPOSE: The purpose of this study was to compare the eQA program of performing laboratory quality assurance with the former paper-based format. MATERIAL AND METHODS: Fourth-year predoctoral dental students (n=334) who experienced both the paper-based and the electronic version of the quality assurance program were surveyed about their experiences. Additionally, data extracted from the eQA program were analyzed to identify areas of weakness in the curriculum. RESULTS: The study findings revealed that 73.8% of the students preferred the eQA program to the paper-based version. The average number of treatments that did not pass quality assurance standards was 119.5 per month. This indicated a 6.34% laboratory failure rate. Further analysis of these data revealed that 62.1% of the errors were related to fixed prosthodontic treatment, 27.9% to partial removable dental prostheses, and 10% to complete removable dental prostheses in the first 18 months of program implementation. CONCLUSIONS: The eQA program was favored by dental students who have experienced both electronic and paper-based versions of the system. Error type analysis can yield the ability to create customized faculty standardization sessions and refine the didactic and clinical teaching of the predoctoral students. This program was also able to link patient care activity with the student's laboratory activities, thus addressing the latest requirements of the CODA regarding the competence of graduates in evaluating laboratory work related to their patient care.

Standards, Regulation and Registration of Dental Laboratories. An Industry Update.

State dental associations are showing increased interest in maintaining current standards and regulations affecting the dental laboratory industry as mandated by the Food and Drug Administration. The domestic dental laboratory industry is being significantly stressed by foreign competition, rapid technology development and unprecedented consolidation, which are changing the way that prosthetic devices and restorations are manufactured and delivered to dentists. Of paramount importance to the prescribing dentist is the accurate documentation of the source and materials being used in prostheses being delivered to patients.

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.

Laboratory quality assurance in the Department of Restorative Dentistry at the University of Illinois at Chicago, College of Dentistry.

PURPOSE: The purpose of this study was to evaluate data collected in University of Illinois at Chicago College of Dentistry (UIC COD) laboratory quality assurance (QA) forms, analyze the collected data, and create a report of the findings. The goals of the study were to (1) identify the most common mistakes occurring during laboratory and clinical procedures when performing prosthodontic treatment, (2) note the incidence and trends of mistakes made by D3, D4, and IDDP2 students, and (3) observe any differences in the types of mistakes made by D3, D4, and IDDP2. MATERIALS AND METHODS: QA data from June 1, 2007 to May 31, 2009 were evaluated based on forms gathered from the QA dental laboratory from all D3, D4, and IDDP2 students' submissions. All students had graduated from the UIC COD at the time of collection. Data were recorded for type of errors made in submission of laboratory work (Indirect Restorations [IR], Removable Partial Dentures [RPD], Complete Dentures [CD]), year of student in dental school (D3, D4, IDDP2), and frequency of rejection for each respective student. The frequency of common mistakes were pooled, evaluated, and reported by respective class year. RESULTS: The five most common laboratory submission errors for D3, D4, and IDDP2 students were nearly the same among student years for IR, RPD, and CD. D4 students had disproportionately higher numbers of work rejections compared to D3 and IDDP2 students. CONCLUSIONS: D4 students had a higher percentage of laboratory submission errors compared to D3 students for all laboratory procedures. There were similar types of errors noted between foreign-trained students (IDDP2) and domestically trained students (D3, D4).

Microstructure analysis of dental castings used in fixed dental prostheses--a simple method for quality control.

The aim of this study was to evaluate the microstructural quality of noble alloy castings from commercial dental laboratories using the wiping-etching method as a simple method for quality control. In total, 240 castings from two noble alloys (AuAgCuPt and AuPtZn) were taken from a day's production of five different dental laboratories. The casting quality was evaluated by determining the grain size and by assessing the number and size of shrinkage cavities after acidic etching of the alloy surfaces. The AuAgCuPt alloy castings showed an acceptable quality in the microstructural analysis. The results of AuPtZn castings, however, were not satisfactory because 50.8% of the samples showed a remarkably poorer quality compared to the specifications made by the manufacturer. The proportion of the employed reclaimed alloy had no influence on the casting quality when AuAgCuPt alloy was used, but was influential when casting restorations with AuPtZn alloy. When determining the quantity and size of shrinkage cavities, none of the evaluated castings was of such a poor quality that a replacement of the castings had to be considered. The differences in grain size and quantity of shrinkage cavities were reflecting the individual laboratory process rather than the admixture of new/reclaimed alloy. The presented analysis can be used as a simple method for quality control of dental castings.

Influence of the fabrication process on the in vitro performance of fixed dental prostheses with zirconia substructures.

Chipping of the applied veneering ceramic is reported to be a main clinical failure type of computer-aided design/computer-aided manufacturing- or manually copy-milled zirconia restorations. The aim of this in vitro study was to investigate whether different substructure designs and veneering processes done by different dental technicians do significantly influence chipping in zirconia-based all-ceramic fixed dental prostheses during simulated oral service. Five groups (n = 8 per group) of three-unit zirconia substructures were fabricated in three different laboratories using copy-milling technique. Three series were veneered with identical porcelain (groups 1-3) and one with a second different porcelain (group 4). The fifth group was milled to final contour design without veneering. Dimensions of the connector areas were determined. All fixed partial dentures (FPDs) were adhesively boned on human teeth and thermally cycled and mechanically loaded (1.2 × 10(6) × 50 N; 6,000 × 5°C/55°C) using human antagonists. Restorations were monitored during thermal cycling and mechanical loading (TCML). FPDs which survived were loaded to fracture. FPDs which failed during TCML were investigated with fractographic means. During TCML, chipping took place in groups 1 (two times), 2 (four times) and 3 (five times) (Table 1). Chipping areas varied between 2.3 mm(2) (group 3) and 58.7 mm(2) (group 2). Groups 4 and 5 provided no failures during TCML. Failure in all cases started from contact points, where superficial wear and disruption of the porcelain were found. No significant correlation could be determined between connector thickness and number of failures. Median fracture results varied between 1,011 N (group 3) and 2,126 N (group 2). The results show the necessity of considering individual design and manufacturing of restorations as well as contact situation. Advanced technical training on zirconia-based restorations is recommended.

Firing temperature accuracy of four dental furnaces.

In spite of using recommended firing and displayed temperatures, low-fired dental porcelain more often demonstrates unsatisfactory results after firing than porcelain fired at higher temperatures. It could therefore be anticipated that temperatures shown on the display are incorrect, implying that the furnace does not render correct firing programs for low-fired porcelain. The purpose of this study is to investigate deviations from the real temperature during the firing process and also to illustrate the service and maintenance discipline of furnaces at dental laboratories. Totally 20 units of four different types of dental furnaces were selected for testing of temperature accuracy with usage of a digital temperature measurement apparatus, Therma 1. In addition,the staffs at 68 dental laboratories in Sweden were contacted for a telephone interview on furnace brand and on service and maintenance program performed at their laboratories. None of the 20 different dental furnaces in the study could generate the firing temperatures shown on the display, indicating that the hypothesis was correct. Multimat MCII had the least deviation of temperature compared with displayfigures. 62 out of 68 invited dental laboratories chose to participate in the interviews and the result was that very few laboratories had a service and maintenance program living up to quality standards. There is room for improving the precision of dental porcelain furnaces as there are deviations between displayed and read temperatures during the different steps of the firing process.

The relationship between dentists and dental laboratories--predictions for the future.

This article provides an overview of the key market changes that are impacting the day-to-day relationship between dentists and dental laboratories and technicians. There are a variety of factors that facilitate the need for broader communication between dentists and dental technicians.

[Control of cross-contamination in dental prostheses laboratories in Galicia]. / Control de la infección cruzada en los laboratorios de prótesis dental de Galicia.

BACKGROUND: Dental laboratories are a potential source of cross-contamination. This study aims to assess its control in Galicia. METHODS: Voluntary random telephone interviews resulted in 149 completed questionnaires. The variables are described by percentages or means and standard deviations. A bivariate analysis was undertaken using the Chi square test. RESULTS: Participants were mostly middle-age (mean=45.7, SD=9.8) males (68.5%) with 20.8 (SD=10.5) years of professional experience in middle-size urban (58.4%) laboratories, who identified a higher risk when receiving items from the clinic (80.6%). Most technicians (57.7%) have a written protocol. Many (55.0%), significantly older males, do not check for item disinfection. Most technicians use gloves (62.4%) particularly younger staff at larger laboratories. Fifty-five point seven percent had been vaccinated against hepatitis B. Only 22.0% of technicians reported receiving training in cross-contamination control. CONCLUSIONS: Identified cross-infection control practices are below standards, and lack of training and protocols are a matter for concern.

Bioseguridad en el laboratorio dental / Biosafety in the dental laboratory

Una enfermedad infecciosa es aquella producida por un agente infeccioso (bacterias, hongos, virus, etc.) que ingresa y se desarrolla en el organismo de un hospedero. Posteriormente, puede trasmitirse de un individuo a otro directamente por contacto entre ambos, o bien, indirectamente, por medio de un vec-tor biológico (de naturaleza animal o vegetal), o de un fómite (objeto inanimado). Las vías por las que un agente infeccioso puede ingresar a un hospedero son: inhalación (respiración de aerosoles), ingestión (salpicaduras de gotas), penetración de mucosas (na-sal, ocular y bucal) o lesiones en la piel o mucosas. Las fuentes de infección pueden ser los pacientes, el personal del consultorio o laboratorio, las superficies e instrumental contaminados y las prótesis o com-ponentes de éstas. Para evitar la propagación de los agentes microbianos se debe interrumpir el proceso de transmisión de los mismos. Todo profesional debe fortalecer y readecuar normas y protocolos de biose-guridad en la tarea diaria, para minimizar el riesgo de transmisión directa y cruzada entre el profesional, su equipo auxiliar, el laboratorista y los pacientes (AU)

An infectious disease is one caused by an infectious agent (bacteria, fungi, virus, etc.) that enters and develops in a host. Then it can be transmitted from one individual to another directly by contact between the two or, indirectly through a biological vector (an animal or plant nature), or a fomite (an inanimate object). The routes by which an infectious agent can enter a host are: inhalation (breathing of aerosols), ingestion (splash of droplets), penetration of mucous membranes (nasal, ocular and oral) and skin or mucous lesions. Sources of infection can be patients, office or laboratory personnel, contaminated surfaces and instruments and the prosthesis or component thereof. To prevent the spread of microbial agents, the process of their transmission must be interrupted. Every professional must strengthen and readjust biosafety standards and protocols in daily work to minimize the risk of direct and cross-transmission between the professional, his auxiliary team, the laboratory technician and the patients (AU)

Longevity of the tooth/restoration complex: a review.

The contemporary dentist has a wide variety of materials to utilize in the restoration of defective teeth. The decision as to which restorative approach should be utilized in any given clinical situation is a joint one between the patient and the treating dentist. The dentist's primary obligations are to understand the indications and contraindications of various materials, understand how to optimally manipulate those materials, and educate the patient so that they make intelligent decisions and give proper informed consent. The ultimate decision as to which approach to use rests with the patient, and the patient must clearly understand the benefits and risks associated with different restorative options. Clearly, one of the important considerations with any treatment is the prognosis and restoration longevity. When attempting to predict the long-term prognosis of any restoration, it is important to consider both the restorative material being considered as well as the specific tooth that is being restored. Many times the amount of remaining tooth structure has a more significant bearing on long-term prognosis than what material is used for restoration. Thus, the tooth/ restoration complex must be considered as a whole when predicting potential longevity. Many clinical trials have been conducted to attempt to answer those questions, and relatively few unbiased, unambiguous answers are available. The only completely honest answer to those questions is "It depends". This is because the prognosis of all restorative therapy depends on the complex interaction of a number of variables, some of which are controlled by the dentist, and some of which are totally out of the dentist's control. This article will attempt to delineate some of the factors related to the long-term prognosis of the tooth/restoration complex, and specifically identify factors that decrease the prognosis of the tooth/restoration complex.