Bone healing capacity of titanium plasma-sprayed and hydroxylapatite-coated oral implants

The authors report preliminary results of Brief Supportive Psychotherapy (BSP) in the Beth Israel Brief Psychotherapy Program for a sample with primarily Cluster C Axis II disorders. This study compares 24 patients treated with BSP with 25 patients treated with Short-Term Dynamic Psychotherapy (STDP). STDP was chosen because its confrontational methods contrast dramatically to BSP, which emphasizes building self-esteem, reducing anxiety, and enhancing coping mechanisms. Videotaped therapies were based on manualized 40-session protocols. Similar degrees of improvement were seen in BSP and STDP at termination and at 6-month follow-up. A study of therapeutic alliance in BSP showed stable and high levels of alliance in good-outcome cases and more variability in poor-outcome cases. These preliminary findings are consistent with other studies and suggest supportive psychotherapy may be effective for many patients, leading to significant and lasting change.     

Mechanical and histological evaluation of amorphous calcium phosphate and poorly crystallized hydroxyapatite coatings on titanium implants

The effect of amorphous calcium phosphate (Ca/P) and poorly crystallized (60% crystalline) hydroxyapatite (HA) coatings on bone fixation to "smooth" and "rough" (Ti-6A1-4V powder sprayed) titanium-6Al-4V (Ti) implants was investigated. Implants were evaluated histologically, mechanically, and by scanning electron microscopy (SEM) after 4 and 12 weeks of implantation in a rabbit transcortical femoral model. Histological evaluation of amorphous vs. poorly crystallized HA coatings showed significant differences in bone apposition (for rough-coated implants only) and coating resorption (for smooth- and rough-coated implants) that were increased within cortical compared to cancellous bone. The poorly crystallized HA coatings showed most degradation and least bone apposition. Mechanical evaluation, however, showed no significant differences in push-out shear strengths between the two types of coatings evaluated. Differences between 4 and 12 weeks were significant for coating resorption and push-out shear strength but not for bone apposition. Significant enhancement in interfacial shear strengths for bioceramic coated as compared to uncoated implants were seen for smooth-surfaced implants (3.5-5 times greater) but not for rough-surfaced implants at 4 and 12 weeks. Rough implants showed greater mean interfacial strengths than uncoated smooth implants at 4 and 12 weeks (seven times greater) and to coated smooth implants at 12 weeks only (two times greater). Mechanical failure of the bone/coating/implant interface consistently occurred within the bone, even in the case of the poorly crystallized HA coatings, which had almost completely resorbed on rough implants. These results suggest that once early osteointegration is achieved biodegradation of a bioactive coating should not be detrimental to the bone/coating/implant fixation.     

Long-term follow-up on hydroxylapatite-coated cylindrical dental implants: a comparison between developmental and recent periods

PURPOSE: To compare success rates for dental implants placed from 1985 through 1988 and from 1989 through 1991, and to investigate the factors associated with success or failure. PATIENTS AND METHODS: All hydroxylapatite-coated cylindrical implants placed from 1985 through 1991 were followed yearly. Lifetable survival analyses compared implant success for a "developmental period" from 1985 through 1988 (4 to 8 years follow-up) and a "recent period" from 1989 through 1991 (1 to 4 years follow-up). Reasons for success or failure, time from implant placement to removal related to failure reason, outcome after implant removal, and a morbidity analysis are included. RESULTS: The 7 to 8-year cumulative success rate for all implants placed in the developmental period (maxilla and mandible combined) was 86.5%; it was 84.2% for all maxillary implants and 87.5% for all mandibular implants. The cumulative success rate for all implants placed in the recent period was 97.5%; it was 97.5% for all maxillary implants and 97.6% for all mandibular implants. The difference between the two periods was statistically significant only for the anterior maxilla. Regression analysis on the interval success rates indicates that interval failure did not follow a linear relationship with time. The most common reasons associated with failure were lack of keratinized gingiva, poor oral hygiene, mechanical overload, and malposition. CONCLUSION: Comparison with previously reported cumulative success rates indicated learning curve experiences comparable with other implant systems. Improvements in hardware, surgical and prosthetic techniques, and patient selection have led to an improvement in success rates with the recent period implants.     

Mechanical properties of titanium impregnated with bismuth alloy

Conclusion The strength characteristics of the pseudoalloys titanium-BA are determined by the concentration of BA and by the degree of filling of the pores in the process of impregnation. The dependences of the mechanical properties on the BA content are of an extremal nature with a maximum corresponding to the volume concentration of BA of 20–25%. In spite of the low strength of the impregnated material (up to 30 MPa), the strength of the pseudoalloys titanium-BA is 1.5 times to twice as great as the strength of the initial titanium skeletons; this is due to the equalization of stress concentration within the bulk of the pseudoalloy.Translated from Poroshkovaya Metallurgiya, No. 2(278), pp. 83–86, February, 1986.     

Effect of a gas atmosphere on the short-term creep of a VT1-0 titanium alloy

The short-term creep of a VT1-0 titanium alloy is studied in a nitrogen, argon, or helium atmosphere. The experimental dependences of the creep strength and the creep rate on the heating temperature and the load are presented and compared with the data on the alloy creep in hydrogen and air atmospheres obtained earlier.     

Rheological properties and similarity conditions in simulating the upsetting of a titanium alloy VT20 billet: I. Experimental results

The results of high-temperature tensile and compressive tests are used to analyze the effect of a mechanical deformation scheme and the ratio of the initial sizes of the specimens to be upset on the rheological properties of the VT20 titanium alloy.     

热解碳结构对炭/炭复合材料摩擦磨损性能的影响

通过控制化学气相沉积(CVD)工艺条件,得到粗糙层、光滑层、过渡层等几种具有不同微观结构的热解碳。金相观察、摩擦磨损性能的测试结果表明:热解碳的微观结构对炭/炭复合材料的摩擦磨损性能有重大影响;粗糙层结构的炭/炭复合材料摩擦因数高,热稳定性好,是一种优良的摩擦材料;光滑层结构的炭/炭复合材料摩擦因数低,磨损小,可以用作耐磨材料。     

Crystallography of fracture facets in a near-alpha titanium alloy

A faceted initiation site is observed in Ti-6242 alloy for both the cyclic and static-loading test conditions. In this experimental study, the crystallographic orientation of the facets has been determined using the electron backscattered diffraction (EBSD) technique in conjunction with the quantitative tilt fractography in a scanning electron microscope (SEM). Quantitative tilt fractography analysis has been used to determine the spatial orientation of fracture facets. The results indicate that the normal-fatigue (no-dwell) fracture facets are oriented at ∼5 deg with respect to the basal plane; the dwell-fatigue fracture facets are oriented at ∼10 to 15 deg with respect to the basal plane and the static-loading fracture facets are oriented at ∼20 deg with respect to the basal plane. These crystallographic orientation determinations of the fracture facets at the crack-initiation site can be used to obtain an idea about the type of loading that produced them.     

Osseointegrated implants in a patient with osteoporosis: a case report

OBJECTIVE: To evaluate the performance of in situ piezolectric extracorporeal shock-wave lithotripsy (ESWL) in the middle part of the ureter. MATERIAL AND METHODS: 36 consecutive patients presenting with stones of the middle part of the ureter were treated by in situ piezoelectric ESWL (EDAP LT 02). The maximal dimensions of the stones ranged from 5 to 14 mm (m = 7.8). Moderate or severe ureterohydronephrosis was present in 19 cases (53%) and a double J stent had been previously implanted in 6 cases (17%). The ESWL sessions were performed in the ventral supine position without any anaesthesia or systematic premedication, but an IM injection of 100 mg of pethidine was administered during poorly tolerated treatments. RESULTS: The stone was located easily in 23 cases (64%) and with greater difficulty in 13 cases (36%), as an intraoperative intravenous injection of contrast agent was performed in 6 cases (17%). The number of sessions per patient ranged from 1 to 2 (m = 1.16). The complete sucess rate was 75%, with a 64% success rate after a single ESWL session. The performances were statistically independent of stone dimensions and the degree of obstruction of the urinary tract. The complication rate was 5.5%, but no ancillary endoscopic or percutaneous treatment was required. CONCLUSION: In situ piezoelectric ESWL allows effective management of most stones of the middle part of the ureter. However, the treatment of stones with a maximal diameter < 5 mm, especially poorly radiopaque stones, can raise problems of localization. Very large or impacted stones, especially when complicated by urinary tract infection, should be preferably treated by first-line ureteroscopy.     

Elevated-temperature oxidation behavior of titanium silicide and titanium silicide-based alloy and composite

The oxidation behavior of Ti₅Si₃ has been studied in air in the temperature range of 1200 °C to 1400 °C. The oxidation kinetics is slower than that predicted by the parabolic-rate law equation at 1200 °C, but is sharply enhanced beyond a temperature of 1300 °C. The oxidation kinetics of a Ti₅Si₃-8 wt pct Al alloy and a Ti₅Si₃-20 vol pct TiC composite at 1200 °C has also been investigated and compared to that of Ti₅Si₃. Alloying with Al does not alter the oxidation resistance much, but the presence of TiC reinforcements enhances the rate of oxidation significantly. The oxidation products have been identified and the mechanism of oxidation has been analyzed using thermodynamic and kinetic considerations.     

Mechanical behavior of a cryomilled near-nanostructured Al-Mg-Sc alloy

In the present study, the mechanical behavior of a cryomilled Al-7.5 pct Mg-0.3 pct Sc alloy was investigated at temperatures in the range of 298 to 648 K. The grain size of the as-extruded alloy was determined to be approximately 200 nm by transmission electron microscope (TEM) and X-ray diffraction (XRD) analysis. The data indicate that as a result of cryomilling, a supersaturated solid solution with high thermal stability was formed in the Al-Mg-Sc alloy. The high strength at room temperature was primarily attributed to three types of strengthening: grain size effect, solid solution hardening, and Orowan strengthening. The elevated temperature mechanical behavior of the Al-Mg-Sc alloy exhibits the following: (a) a strain-rate sensitivity, m, of less than 0.2; and (b) an activation energy, Q, that increases from 139 to 193 kJ/mol with increasing applied stress. An analysis of the experimental data at elevated temperatures shows that despite the fine-grained structure of the alloy, the deformation characteristics are not consistent with those arising from a superplastic deformation process that incorporates a threshold stress. On the other hand, the analysis suggests that the deformation characteristics agree with those associated with the transition in the creep behavior of Al-based solid solution alloys from that for the intermediate-stress region, where m=0.33 and Q=Q _D (Q _D is the activation energy for self-diffusion in Al), to that of the high-stress region, where m<0.2 and Q>Q _D .     

Hot-salt stress-corrosion of a titanium alloy in a dynamic air environment

Hot-salt stress-corrosion threshold data were determined for the Ti?8Al?1Mo?1V alloy under simulated turbine-engine compressor environmental conditions. Threshold data determined by residual tensile ductility were demonstrated to be a more sensitive indication of hot-salt stress-corrosion than threshold data determined from crack observations. Specimens that had been stress-relieved by chemically milling exhibited drastically lower threshold stresses than did specimens in the as-machined condition. A Mach 0.7 airflow with a dewpoint of?120° F did not significantly reduce stress-corrosion when compared to static air conditions.     

Mechanical behavior of a bulk nanostructured iron alloy

Bulk, fully dense materials were prepared from Fe-10Cu with grain diameters between 45 nm and 1.7 μm. The materials were prepared by ball milling of powders in a glove box, followed by hot isostatic pressing (hipping) or powder forging. Larger grain sizes were obtained by thermal treatment of the consolidated powders. The bulk materials were relatively clean, with oxygen levels below 1500 wpm and other contaminants less than 0.1 at. pct. The mechanical behavior of these materials was unique. At temperatures from 77 to 470 K, the first and only mechanism of plastic deformation was intense shear banding, which was accompanied by a perfectly plastic stress-strain response (absence of strain hardening). There was a large tension-compression asymmetry in the strength, and the shear bands did not occur on the plane of maximum shear stress or the plane of zero extension. This behavior, while unusual for metals, has been observed in amorphous polymers and metallic glasses. On the other hand, the fine-grained Fe-10Cu materials behaved like coarse-grained iron in some respects, particularly by obeying the Hall-Petch equation with constants reasonably close to those of pure iron and by exhibiting low-temperature mechanical behavior which was very similar to that of steels. Transmission electron microscopy (TEM) studies found highly elongated grains within shear bands, indicating that shear banding occurred by a dislocation-based mechanism, at least at grain sizes above 100 nm. Similarities and differences between the fine-grained Fe-10Cu and metals, polymers, metallic glasses, radiation-damaged metals, and quench-damaged metals are discussed. This article is based on a presentation made in the symposium “Mechanical Behavior of Bulk Nanocrystalline Solids,” presented at the 1997 Fall TMS Meeting and Materials Week, September 14–18, 1997, in Indianapolis, Indiana, under the auspices of the Mechanical Metallurgy (SMD), Powder Materials (MDMD), and Chemistry and Physics of Materials (EMPMD/SMD) Committees.     

Spectrum of histological changes reactive to prosthetic breast implants: a clinopathological study of 84 patients

A wide range of host reactions can be produced in response to prosthetic breast implants. Although the spectrum of histological changes is well described in the literature, the chronology and relative occurrence of these changes are not well documented. Examination of 161 capsulectomy specimens from 84 women suggested the following chronological sequence of tissue response: fibrous scar tissue; histiocyte response; foreign body giant cell reaction to extruded or exposed material including polyurethane and Dacron patch; synovial-like metaplasia; and calcification. Fibrous scar tissue was seen in all implants. Histiocytic response was noted in 107/161 of the specimens and a foreign body giant cell reaction to polyurethane was seen only in the two Meme implants. Synovial-like metaplasia was less common than previously reported, occurring in 45/161 of specimens after a mean in situ duration of 11.7 years. This peculiar process was seen only in association with a prominent histiocytic response and was not associated with calcification. Dystrophic calcification, which has been reported as occurring rarely in implant capsules, was seen in 15/161 of our specimens after a mean in situ duration of 17.7 years.     

Asymmetrical mechanical behavior of a precipitation hardened beta titanium alloy

Precipitation hardened single crystals of a beta (bcc) Ti-40 at. pct V + 1.0 at. pct Si alloy have been deformed in compression at 77 K and 298 K. The dependence of the yield stress upon aging time at 843 K for solution treated crystals shows two maxima which are caused by silicide precipitates. The orientation dependence of the yield stress and of the active macroscopic slip plane have been determined as a function of aging time. The solution treated as well as aged crystals exhibit an asymmetry of both the yield stress and the plane of slip, the degree of asymmetry being larger at 77 K than at 298 K. The asymmetry of slip and yielding is not affected by the presence of precipitation hardening. The results indicate that the effect of the dislocation core structure on dislocation motion is independent of the presence of precipitates.