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Following earlier work, three novel aluminoborate glasses have been studied as potential cement components. Factors studied include the effect of batch size on composition and manipulative characteristics, and the effect of tartaric acid and conditions of storage on mechanical properties. It was concluded that two materials have potential for application as dental luting agents.
The rate of the setting process of zinc phosphate dental cement with organic phosphate polymers as additives was measured by a conductance technique. There are two rate-determining parameters, namely an induction period and a first-order reaction constant. The values of the latter constant are not affected by the additives.
We performed 88 primary ball-and-socket arthroplasties of the trapeziometacarpal joint in 84 patients (69 women and 15 men) with a mean age of 61 years (37 to 81). Cemented de la Caffinière prostheses were implanted in 43 joints from 1988 to 1991 and 45 cementless Ledoux implants were used between 1992 and 1994. Of the 61 surviving prostheses still in situ, 51 were reviewed clinically and radiologically with a mean follow-up of 25 months for the Ledoux and 63 months for the de la Caffinière implant. The survival rate for the Ledoux prosthesis was 58.9% at 16 months and for the de la Caffinière implant 66.4% at 68 months. Loosening occurred in 15% of the Ledoux stems, in 46% of the Ledoux cups, in 24% of the de la Caffinière stems and in 28% of the de la Caffinière cups. Both prostheses behaved similarly, and it is clear that a constrained ball-and-socket prosthesis is not suitable for the trapeziometacarpal joint.
Cement extrusion through cortical defects during total hip arthroplasty can be prevented by a simple technique utilizing one or more Penrose drains.
Seventy-six patients who had undergone revision of a cemented total hip replacement were reviewed with an average follow-up of almost ten years. The average age at primary total hip replacement (PTHR) was 63.3 years. The average time between primary total hip replacement and revision was 62.5 months. Revision surgery was performed without using special techniques such as acetabulum reconstruction or femoral bone grafting. We evaluated patients pre- and postoperatively using the Merle d'Aubigné-Postel(M d'A) hip score. Clinically we observed an improvement of the hip score after total hip revision, particularly regarding pain. Thirty hips required a second, and six a third revision. If re-revision is used as an end-point, our results are unsatisfactory, as we had a cumulative failure rate of 54% after 12 years. This is mainly due to not using special techniques adapted to revision situations.
Periacetabular surface deformation of the pelvis and micromotion between implant and bone were measured in three cementless acetabular components. Pelvic deformation was greater in cementless implants than in cemented ones-independent of the stiffness of the implant. The results of micromotion measurements confirmed the function of certain of anchorage concepts, but they also illustrated the limitations of such measurements in single locations.
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An evaluation of the effect of differences in chromium nitrate to cement ratio on the microbial stability of a chromium nitrate/cement waste form, as reflected in the leaching of chromium, calcium, magnesium and aluminum; was carried out in this study. An increase in the proportion of chromium in the waste form from 4.8 to 8.7% had no noticeable effect on microbial stability, with the total chromium leached essentially unchanged. Further increases in the proportion of chromium in the waste form from 8.7 to 10.7%, and from 10.7 to 15.9% resulted in a substantial decrease in microbial stability, with 3-fold and 1.3-fold increase in the total chromium leached, respectively, observed. For calcium, increases in the chromium proportion were accompanied with increases in the total calcium leached even though the increases were not in direct proportion to the increases in chromium proportion. For magnesium and aluminum, increases in the proportion of chromium within the range 4.8-10.7% were accompanied with increases in the total respective metals leached, with minor variation for each metal. On the whole, the maximum percentage chromium leached from the different waste forms was substantially lower than those of the other metals.
The influence of sewage sludge ash (SSA) on workability of cement mortars has been studied. The irregular morphology of SSA particles produced a decrease of mortar workability. A nonlinear reduction of workability in mortars containing SSA was observed, but when SSA content in mortars was increased the workability reduction was less significant. A superplasticizer is used in order to compensate the decrease of workability produced by SSA. When SSA sized fractions were used, only significant differences in workability for mortars prepared with high water volumes or with the presence of superplasticizer were observed.
A study is reported in which a zinc polycarboxylate and a glass polyalkenoate dental cement, were prepared from aqueous solutions of divalent metal chlorides, namely ZnCl2, CaCl2, MgCl2 and SrCl2, all at 1.0 mol dm-3 concentration, as well as from pure water. Calcium chloride was employed at additional concentrations, i.e. 2.0, 0.5 and 0.1 mol dm-3. As was previously found for monovalent salts, setting of the zinc polycarboxylate was speeded up and water uptake generally enhanced by the presence of the divalent metal salts. However, the divalent salts were found to reduce the compressive strength at 24 h (from 86 MPa to about 60 MPa). The glass polyalkenoate showed broadly similar effects to those observed in the presence of monovalent salts, with the setting time being increased, water uptake inhibited and compressive strength at 24 h reduced; however, by contrast, the working time was generally reduced. These results occur because the rate of the neutralization process is increased by the divalent salts, a consequence of the reduced pH of the poly(acrylic acid) caused by these salts. Infrared spectroscopy demonstrated interactions between the metal chlorides and poly(acrylic acid), with various chelate structures being apparent from the position of the asymmetric carbonyl stretch.
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