The quality of fixed prosthodontic impressions: An assessment of crown and bridge impressions received at commercial laboratories.

BACKGROUND: The authors evaluated and quantified clinically detectable errors commonly seen in impressions sent to commercial laboratories and determined possible relationships between finish line errors and other factors involved. METHODS: The authors visited 3 large and 1 small commercial dental laboratories over a 12-month period. Three calibrated examiners evaluated the impressions. The examiners evaluated all impressions for errors by using ×2.5 magnification loupes under ambient room lighting without the aid of additional illumination. RESULTS: The authors evaluated 1,157 impressions; 86% of the examined impressions had at least 1 detectable error, and 55% of the noted errors were critical errors pertaining to the finish line. The largest single error categories evaluated were tissue over the finish line (49.09%), lack of unprepared stops in dual-arch impressions (25.63%), pressure of the tray on the soft tissue (25.06%), and void at the finish line (24.38%). The factors blood on the impression (odds ratio, 2.31; P < .001) and tray type (odds ratio, 1.68; P < .001) were associated significantly with finish line errors. CONCLUSIONS: Marginal discrepancies made up the largest category of error noted in impressions evaluated. The authors noted an increase in errors at the finish line with dual-arch impression techniques and in the presence of blood. PRACTICAL IMPLICATIONS: Dentists have ethical, moral, and legal obligations bestowed on them by the profession and need to evaluate critically the work they send to laboratories. The authors strongly recommend an improvement in technique and reviewing of all impressions and working casts.

Dental technology services and industry trends in New Zealand from 2010 to 2012.

OBJECTIVE: To provide a snapshot of the New Zealand dental technology industry and influencing factors. BACKGROUND: Developing an understanding of the commercial dental laboratory environment in New Zealand can provide insight into the entire dental industry. METHODS: A web-based survey was the primary method for data collection, with separate questionnaires used for dental laboratory owners and dental technician employees. RESULTS: The mean net income for dental laboratory owners in New Zealand was similar to that of the United Kingdom, at $40.50 per hour. Clinical dental technicians are the highest paid employees, with a mean of $33.49 per hour. The mean technical charge for complete dentures was $632.59; including clinical services, it was $1907.00. The mean charge for a porcelain-fused-to-metal (PFM) crown was $290.27. Dental laboratory owners expressed fear about the possibility of losing dental clients to overseas laboratories due to the availability and cheap charge of offshore work. Only 25.4% of dental laboratories surveyed had computer-aided design (CAD) facilities, and even fewer (7.9%) had computer-aided manufacturing (CAM) systems. CONCLUSION: Clinical dental technology appears to be prospering. The dental technology industry appears to be adapting and remains viable, despite facing many challenges.

A survey of removable partial denture casts and major connector designs found in commercial laboratories, Athens, Greece.

PURPOSE: This survey was conducted to study the prevalence of partial edentulism, the type of removable partial denture (RPD) support, the type of major connectors, and the frequency of their use in relation to the partial edentulism classes encountered, concerning patients in Athens, Greece. MATERIALS AND METHODS: The material comprised 628 final casts for RPDs. Each cast was photographed in a way that would allow the number of existing teeth, the classification of partial edentulism, the RPD support, and the particular parts of the metal framework to be identified. Data collected were analyzed statistically using prevalence tables and the χ(2) test. RESULTS: Two hundred seventy six (43.9%) casts were for the maxilla and 352 (56.1%) for the mandible. The most frequently encountered group was Kennedy class I for both arches, while class IV was the classification least encountered (p < 0.001). Of all RPDs constructed, 96.8% had a metal framework (tooth-borne and tooth/tissue-borne), while 3.2% of the RPDs were frameless (tissue-borne, acrylic dentures). The U-shaped palatal connector (horseshoe) in the maxilla and the lingual bar in the mandible were the most frequently used for all partial edentulism classes, at 55.2% and 95%, respectively. CONCLUSIONS: Analysis of the casts revealed that the type of major connectors selected does not comply with the indications for their applications, considering the lack of dental history and clinical examination. This notes the need for further training dentists and dental technicians in aspects of RPD framework design.

Dental alloys used for crown and bridge restorations by dental technicians in New Zealand.

OBJECTIVE: To determine the range and elemental composition of alloys used for PFM and crown-and-bridge restorations by New Zealand dental laboratories, and to understand the reasons for their selection. MATERIALS AND METHODS: Two waves of data collection were carried out via post and telephone interview. The source population was dental laboratories advertised with the Yellow Pages Group in 2007/2008. RESULTS: A total of 83 out of 109 laboratories (76.1%) responded. Of those, 35 laboratories (42.1%) reported producing fixed-prosthodontic restorations. The range of alloy types (consisting of high noble, noble and base-metal alloys), brand names (55 products) and manufacturers was determined, along with the reasons for their selection. Ten international dental alloy manufacturers were identified as being used, with the leading manufacturer being Ivoclar-Vivadent (40.9%), followed by Argen (25.3%). Most laboratories select their alloys based on price and physical properties. The average laboratory carries three to four alloy products. CONCLUSION: Alloy selection by dentists and dental technicians is strongly influenced by economic factors. While the study identified the range of alloys being used for fixed restorations in terms of alloy type and brand name, further research is needed to determine the proportions of fixed restorations produced from high noble, noble and base metal alloys, together with dental practitioners' attitudes to, and preferences in, alloy selection.

Quality of communication and master impressions for the fabrication of cobalt chromium removable partial dentures in general dental practice in England, Ireland and Wales in 2009.

The aim of this study was to investigate the quality of communication and master impressions for the fabrication of cobalt chromium removable partial dentures (RPDs) in general dental practice in England, Ireland and Wales in 2009. Two hundred and ten questionnaires were distributed to 21 laboratories throughout England, Ireland and Wales. Information was collected regarding the quality of written communication and selection of master impression techniques for cobalt chromium partial dentures in general dental practice. One hundred and forty-four questionnaires were returned (response rate = 68%). Alginate was the most popular impression material being used in 58% of cases (n = 84), while plastic stock trays were the most popular impression tray, being used in 31% of cases (n = 44). Twenty-four per cent (n = 35) of impressions were not adequately disinfected. Opposing casts were provided in 81% of cases (n = 116). Written instructions were described as being 'clear' in 31% of cases (n = 44). In 54% of cases (n = 76), the technician was asked to design the RPD. Based on the findings of this study, written communication for cobalt chromium RPDs by general dental practitioners is inadequate. This finding is in breach of relevant contemporary legal and ethical guidance. There are also concerns in relation to the fabrication process for this form of prosthesis, particularly, in relation to consideration of occlusal schemes.

Replacement of missing teeth in a southern region of Vietnam--a descriptive dental laboratory study.

AIM: To explore whether tooth replacement in a southern region of Vietnam is in line with the primary health care approach, aiming at health services for all people at affordable costs. METHODS: Tooth replacement was investigated by means of prostheses as delivered by four dental laboratories of which the output was considered representative. Information was based on dental casts related to the prostheses. RESULTS: Prostheses replaced almost all missing teeth, irrespective of the types (interrupted or shortened dental arches) and numbers of missing teeth in the dental arch they were made for. Acrylic removable partial dentures were the most common prostheses delivered (65% of removable partial dentures). CONCLUSION: It cannot be stated that dental arch conditions in this study were representative for the southern Vietnamese population. However, it is concluded that dental practitioners tend to provide complete dental arches by tooth replacements. This morphologically based approach might introduce over treatment. In line with primary oral health care, a functionally oriented treatment management, including the shortened dental arch concept, should be implemented.

Considerations for services from dental technicians in fabrication of fixed prostheses: A survey of commercial dental laboratories in Thessaloniki, Greece.

STATEMENT OF PROBLEM: Effective communication and cooperation between dentists and dental technicians are essential in providing quality services. There has been a lack of information regarding dentist-dental technician communications and current methods and materials used for the fabrication of fixed partial dentures (FPDs). PURPOSE: This cross-sectional study identified the materials and techniques used for fabrication of FPDs, as well as the status of communication between dentists and dental technicians in Thessaloniki, Greece. MATERIAL AND METHODS: A questionnaire was developed with 7 sections pertaining to procedures and materials used for the fabrication of fixed prostheses: general questions, infection control, impressions/interocclusal records, die technique/mounting, information from final casts, prostheses design/materials, and communication/shade selection. The questionnaire was anonymous and distributed by the Association of Dental Technicians of Thessaloniki to all member laboratories (228) in the wider province of Thessaloniki, Greece. Due to the absence of normal distribution of the results, frequencies and medians were reported. RESULTS: Ninety-six of 228 dental laboratories responded (42.1% response rate). Twenty-six percent of dental laboratories did not routinely disinfect incoming items. The dental technicians considered 30% of incoming final impressions and 20% of interocclusal registrations as inadequate. Half of the time (55%) final casts were mounted by technicians on simple hinge articulators. Only 20% of tooth preparations had adequate finish lines. The majority (70%) of fixed restorations were metal-ceramic. Fifty-seven percent of dental technicians considered the delivery time requested by dentists as insufficient. CONCLUSION: The information provided in this study indicates areas of weakness in communication between dentists and dental technicians, along with areas where both parties should use greater care during clinical and laboratory procedures.

Dos sistemas de desinclusión de dientes retenidos: Sistema Resorte Ballesta y Sistema Trampa de Ratón / Two systems of desinclusion of retained teth: system means crossbow and mouse trap system

La presencia de un diente retenido es muy común en niños, excluyendo las terceras molares son los más frecuentemente impactados. Comúnmente la mayoría de estos dientes son expuestos quirúrgicamente siguiendo su orientación ortodóntico dentro de la arcada dental 1. Dentro de las variaciones de tratamiento ortodóntico tenemos el sistema Ballista Spring y el Mouse Trap que nos va a permitir solucionar limitaciones de otros sistemas 2,4,16.

The presence o retained teeth is very common in children, excluding third molars, the are the most frequently. Most of these teeth are exposed surgically following its orthodontic direction within the dental arches 1. In othodontic treatment we have the system Ballista Spring and the Mouse Trap that will allow us the solve limitations o another systems 2,4,16.

Dentist communication with the dental laboratory for prosthodontic treatment using implants.

PURPOSE: A questionnaire was sent to U.S. dental laboratories to evaluate the level of communication between dentists and laboratory technicians and to determine trends in procedures and materials used in fixed and removable implant restorations. METHODS AND MATERIALS: Dental laboratories were randomly chosen from the National Association of Dental Laboratories for each of the 50 states. The questionnaire was mailed to the laboratory directors for 199 dental laboratories. One hundred fourteen dental laboratories returned the survey, yielding a response rate of 57%. Of those laboratories, 37 indicated that they did not participate in the fabrication of fixed implant restorations, yielding a response rate of 39%. Forty-two dental laboratories indicated that they did not participate in the fabrication of implant-retained overdenture prostheses, yielding a response rate of 36%. RESULTS: Results from this survey show inadequate communication by dentists in completing work authorization forms. Custom trays are used more frequently for implant-retained overdenture impressions and stock trays for impressions of fixed implant prostheses. Poly(vinyl siloxane) is the material most commonly used for both fixed and removable implant-supported prostheses. Two implants with stud attachments are used more widely than those with bar attachments for implant-retained overdentures. CONCLUSIONS: Most laboratories working on implant prosthodontic cases report inadequate communication between the laboratory and dentists related to materials and techniques used in fabrication of implant restorations.

A survey of the UK maxillofacial laboratory service: profiles of staff and work.

We sent questionnaires to 98 maxillofacial laboratories in the United Kingdom and asked about the composition of their staff, the kind of work that they do, and their activities in relation to the treatment of disfigured patients who require facial and body prostheses. We received 59 replies about 193 laboratory staff, most of whom had 10 or more years experience and held basic and advanced qualifications in dental technology. Most laboratories did all sorts of work including maxillofacial, orthodontic, dental prosthetic and crown and bridge work. Only five confined themselves to maxillofacial work. One hundred and eighteen staff (61%) had contact with 4,259 disfigured patients who required prostheses. Fifty-three laboratory managers (89%) thought that maxillofacial prosthetists and technologists gave psychological support to these patients, but only 12 laboratories (21%) had staff with formal training in counselling.

The national survey of adverse reactions to dental materials in the UK: a preliminary study by the UK Adverse Reactions Reporting Project.

OBJECTIVE: Dental treatment involves the use of a wide range of materials. Many of the dental materials or their components pose a potential risk to the patient and member of the dental team. Pre-market biocompatibility testing cannot guarantee absolute safety, making monitoring of materials likely to cause an adverse reaction essential. The prevalence of adverse reactions to dental materials amongst dental patients and staff has not been systematically monitored in the UK. This project aims to develop a systematic approach to the evaluation and monitoring of the extent and severity of adverse reactions to dental materials in the UK. METHOD: Through the distribution of reporting forms to dental surgeries and laboratories in the UK, the ARRP has received 1,075 complete reports relating to adverse reactions seen or experienced by dental staff and patients. RESULTS: The main findings were that different materials cause adverse reactions to different groups of people. The largest proportion of patient related adverse reactions were reported to be due to metals (n = 175). These were mainly amalgam associated oral lichenoid reactions (n = 124). Dental technicians reported acrylic resin as the causal factor of hand dermatitis in 61% (44 out of a total 72) of cases reported. Finally, dental surgery staff reported gloves as causing hand dermatitis in 75% of cases (398 out of a total 531). CONCLUSIONS: Different dental materials affect different person groups depending on their exposure to the material. Dental staff are most at risk from an adverse reaction to latex gloves, whereas most reported reactions for patients were due to metals. For dental technicians the biggest danger of an adverse reaction was from acrylic resins. There is a need to continue to raise the awareness among dental professionals of the existence of the Adverse Reactions Reporting Project so as to overcome problems of under-reporting.

Quality of materials supplied to dental laboratories for the fabrication of cobalt chromium removable partial dentures in Ireland.

The adequacy of prescription for fabrication of cobalt chromium removable partial dentures is often regarded as being less than ideal. This study examines the nature and quality of written instructions and master impression sent to dental laboratories in Ireland for fabrication of cobalt chromium removable partial denture frameworks. Questionnaires were issued to dental laboratories seeking specific information relating to the materials (impression materials and trays) and written instructions supplied, as well as the technicians' opinion regarding the suitability of these materials. One hundred completed questionnaires were returned. One-third of master impressions were made using a plastic stock tray and alginate; technicians felt that one-fifth of master impressions were unsuitable; almost three-fifths of written instructions were inadequate. The quality of clinical information examined was found to be less than adequate.

Orthodontic soldering techniques: aspects of quality assurance in the dental laboratory.

BACKGROUND: In Germany, the dental technician is required by the Medical Products Act (MPG) to produce workpieces of high safety and quality and to document these properties. Soldering continues to be the prevailing joining technique in the dental laboratory, although problems arise from the susceptibility to corrosion and the low strength of soldered joints. This study aimed to reveal sources of defects in dental laboratory workpieces in order to achieve optimization in terms of quality assurance. MATERIAL AND METHODS: The joints were produced by various dental technicians using three different soldering techniques. These joining techniques were investigated for their quality and their corrosion properties during immersion in ferric chloride, orthodontic appliance cleanser, and artificial saliva. Observance of the soldering instructions by the dental technicians was checked. Corrosion attack was confirmed by scanning electron microscopy and by measuring the ion concentrations of copper, silver and zinc in the corrosive agents, using atomic emission spectroscopy with stimulation by inductively coupled plasma (ICP-AES analysis). RESULTS AND DISCUSSION: Incomplete filling of the soldering gap, porosities resulting from the production process, poor corrosion properties, and in particular a high variability of the measured values point to insufficient reliability of two soldering techniques. Variations in quality were also detected among the technicians' modes of operation. CONCLUSION: The analyses confirm the need for quality assurance of soldering techniques and for increased support for alternative joining techniques such as laser welding in the future. The results of the studies on laser welding are presented in a separate publication.

Debt and practice profiles of beginning dental practitioners.

Escalating student debt for dental education has led some to speculate that beginning practitioners may undertake procedures that are beyond their competence in an effort to augment practice income. This hypothesis was tested directLy using a data set containing self-reports of practice profiles across a wide range of procedures and debt for education, practice, and personal purposes. Respondents were 113 individuals who had graduated from a private dental school from 1986 to 1997. Conservative dental practice was measured by comparing frequency of commonly and uncommonly performed procedures in the group as a whole against the profile for each respondent. There was no association between educationaL debt and propensity to engage in unconventional procedures. Older dentists and those who felt more competent at the time of graduation were less conservative. Amount of practice debt was a better predictor of unconventional practice than was educational debt.

Analysis of workplace injuries in a dental school environment.

Workplace injuries at the University of Queensland Dental School during the period 1992-1994 were assessed to determine their incidence, and the associated indirect costs, causal factors, and appropriate preventive strategies. Overall, dental chairside assistants experienced a higher incidence of injuries than students both on a per worker and per time basis. Of the injuries with a low risk of cross-infection, burns and scalds from sterilizing equipment, and eye injuries in laboratories were the most common. This emphasizes the importance of wearing appropriate protective equipment in areas outside the treatment zone, and the need for signage and education. Common causes of sharps injuries were burs left in handpieces, two-handed needle recapping, and cleaning of probes in the sterilizing room. Changes to techniques and equipment would prevent such incidents. A range of factors which contribute to the calculation of indirect costs following injuries in the dental workplace are identified.

Quality assurance for the laboratory aspects of prosthodontic treatment.

Inconsistency in the product returned from the commercial dental laboratory led to the development of a formal quality assurance (QA) program at the University of Detroit Mercy School of Dentistry in 1994. The goal of the program was to improve the quality of prosthodontic laboratory submissions and the returned product, facilitate laboratory communications, and, ultimately, enhance the quality and timeliness of patient care. Each student submission is evaluated with a criterion-referenced evaluation form. Deficiencies are communicated to the student, and the corrected submission is then sent to the laboratory. Three-year remake data from the main clinic (QA site) and an extramural clinic (non-QA site) demonstrate the effectiveness of the program. The major benefits are more efficient, cost-effective patient care, as well as the provision of a model for the student to practice the skills needed for effective communication with the dental technician, upon graduation.