Radiological factors influencing femoral and acetabular failure in cemented Charnley total hip arthroplasties.
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We have made a retrospective review of 185 cemented Charnley total hip arthroplasties performed between 1970 and 1974 to determine the relationships between radiological variables and failure of the femoral and acetabular components. We measured the acetabular wear, the orientation of the cup, the thickness and consistency of acetabular and femoral cement mantles, radiolucency and femoral alignment. The mean follow-up was for 11.7 years. Femoral loosening was demonstrable radiologically in 15 hips (8.1%), ten (5.4%) of which were revised during the period of follow-up. Only when the first postoperative radiograph showed a thin cement mantle in Gruen zone 5 was there a significant association with failure of the femoral component. There were 12 loose acetabular components (6.5%), nine (4.8%) of which were revised. When the initial radiograph after operation showed radiolucency in DeLee and Charnley zone 1, the incidence of acetabular loosening was 28.21%. If such radiolucency was not present, the incidence of acetabular loosening was only 0.69%. Our findings emphasise the importance of careful cementing. (+info)
Influence of composite inlay/onlay thickness on hardening of dual-cured resin cements.
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This investigation evaluated the effect of resin composite inlay/onlay thickness on the hardness of a group of eight dual-cure resin-based cements. Fourteen disc specimens measuring 6 mm in diameter and 2.5 mm thick were prepared from each of eight dual-cure cements: Adherence, Choice, Duolink, Enforce, Lute-It, Nexus, Resinomer and Variolink. Two specimens from each material were directly light-cured while the remainder of the specimens were light-cured through resin composite spacers varying in thickness from 1 mm to 6 mm. Curing through the spacers always resulted in a decrease in the Knoop hardness number. For some cements, hardness values were reduced by 50% or more when the resin composite spacer thickness was 4 mm or greater even when measurements were made one week after dual-curing. Low hardness values indicate the presence of a weak chemical-curing mechanism that may compromise cement quality in areas of the cavity not readily accessible to the curing light. (+info)
A survey of the delegation of orthodontic tasks and the training of chairside support staff in 22 European countries.
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This paper reports on a survey which was undertaken to investigate the delegation of orthodontic tasks and the training of chairside support staff in Europe. Two questionnaires were posted to all members of the EURO-QUAL BIOMED II project together with an explanatory letter. The first dealt with the delegation of nine clinical tasks during orthodontic treatment. The second with the types of chairside assistant employed in each country and the training that they are given. Completed questionnaires, which were subsequently validated, were returned by orthodontists from 22 countries. They indicated that there was no delegation of clinical tasks in six of the 22 countries and delegation of all nine tasks in five countries. The most commonly delegated tasks were taking radiographs (in 14 of the 22 countries) and taking impressions (in 13 of the 22 countries). The least commonly delegated tasks were cementing bands (in five of the 22 countries) and trying on bands (in six of the 22 countries). Seven of the 22 countries provided chairside assistants with training in some clinical orthodontic tasks. Eighteen of the 22 countries provided general training for chairside assistants and offered a qualification for chairside assistants. Four of these 18 countries reported that they only employed qualified chairside assistants. Of the four countries which reported that they did not provide a qualification for chairside assistants, two indicated that they employed chairside assistants with no formal training and two that they did not employ chairside assistants. It was concluded that there were wide variations within Europe as far as the training and employment of chairside assistants, with or without formal qualifications, and in the delegation of clinical orthodontic tasks to auxiliaries was concerned. (+info)
Restoration of endodontically treated teeth with carbon fibre posts--a prospective study.
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BACKGROUND: A prospective study was started in 1995 to evaluate the success of carbon fibre reinforced epoxy resin (CFRR) posts used to restore endodontically treated teeth. All the teeth in the study had lost more than 50% of their coronal structure. METHODS: Fifty-nine carbon fibre Composiposts cemented with Metabond and built up with Core Paste cores were placed into the teeth of 47 patients. Each tooth received a full-coverage restoration (porcelain fused to metal crown) and was followed for 6.7-45.4 months (average = 28.0 months, standard deviation = 10.7). RESULTS: Results for 52 teeth in 42 patients were analyzed. There were no fractures. The overall failure rate was 7.7% and the cumulative survival rate was 89.6% at the end of the follow-up period. The only statistically significant finding (p = 0.04) was that posts in lower premolars were at higher risk of failure. CONCLUSION: CFRR posts are among the most predictable systems available today. CFRR posts in the upper anterior teeth are associated with a higher success rate and longer life than those placed in premolars, especially lower premolars. This study contributes to the growing body of evidence that supports the use of CFRR posts in the restoration of endodontically treated teeth. (+info)
All-polyethylene versus metal-backed and stemmed tibial components in cemented total knee arthroplasty. A prospective, randomised RSA study.
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We studied the quality of fixation of the tibial component using radiostereometric analysis (RSA) in 40 patients who had undergone a cemented Freeman-Samuelson total knee arthroplasty. They were prospectively randomised to either a stemmed metal-backed (MB) or non-stemmed all-polyethylene (AP) tibial component. The articulating geometry of the implants was identical, as was the operative technique and the postoperative regime. The study showed no complications of fixation using AP tibial components, and the migration was the same as that of their metal-backed counterparts. There was no bony collapse or increased subsidence of any part of the tibial component or increased incidence of radiolucent lines in the knees with AP components. Most AP implants were stable between one and two years after surgery, a finding known to be of positive prognostic significance when predicting future aseptic loosening. (+info)
Radiological features predictive of aseptic loosening in cemented Charnley femoral stems.
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The radiological features of the cement mantle around total hip replacements (THRs) have been used to assess aseptic loosening. In this case-control study we investigated the risk of failure of THR as predictable by a range of such features using data from patients recruited to the Trent Regional Arthroplasty Study (TRAS). An independent radiological assessment was undertaken on Charnley THRs with aseptic loosening within five years of surgery and on a control group from the TRAS database. Chi-squared tests were used to test the probability of obtaining the observed data by chance, and odds ratios were calculated to estimate the strength of association for different features. Several features were associated with a clinically important increase (>twofold) in the risk of loosening, which was statistically significant for four features (p < 0.01). Inadequate cementation (Barrack C and D grades) was the most significant feature, with an estimated odds ratio of 9.5 (95% confidence interval 3.2 to 28.4, p < 0.0001) for failure. (+info)
Changes in proximal femoral strain after insertion of uncemented standard and customised femoral stems. An experimental study in human femora.
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We have compared the changes in the pattern of the principal strains in the proximal femur after insertion of eight uncemented anatomical stems and eight customised stems in human cadaver femora. During testing we aimed to reproduce the physiological loads on the proximal femur and to simulate single-leg stance and stair-climbing. The strains in the intact femora were measured and there were no significant differences in principal tensile and compressive strains in the left and right femora of each pair. The two types of femoral stem were then inserted randomly into the left or right femora and the cortical strains were again measured. Both induced significant stress shielding in the proximal part of the metaphysis, but the deviation from the physiological strains was most pronounced after insertion of the anatomical stems. The principal compressive strain at the calcar was reduced by 90% for the anatomical stems and 67% for the customised stems. Medially, at the level of the lesser trochanter, the corresponding figures were 59% and 21%. The anatomical stems induced more stress concentration on the anterior aspect of the femur than did the customised stems. They also increased the hoop strains in the proximomedial femur. Our study shows a consistently more physiological pattern of strain in the proximal femur after insertion of customised stems compared with standard, anatomical stems. (+info)
Esthetic option for the implant-supported single-tooth restoration -- treatment sequence with a ceramic abutment.
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A single implant-supported restoration is one treatment alternative to consider for the replacement of a missing tooth. Technological advances in materials and machining have led to the development of a densely sintered aluminum oxide ceramic abutment, designed and machined using CAD/CAM technology. This manufacturing method improves management of the subgingival depth of the crown/abutment interface and enhances the esthetic qualities of the restoration. However, since this ceramic abutment has less mechanical resistance than metal abutments, its use should be confined to the restoration of incisors and premolars not subjected to excessive occlusal forces. (+info)